- Email: [email protected]
Integration of Biochar Filtration into Aquaponics: Effects on Particle Size Distribution and Turbidity Removal
Agricultural Water Management xxx (xxxx) xxxx
Contents lists available at ScienceDirect
Agricultural Water Management journal homepage: www.elsevier.com/locate/agwat
Integration of Biochar Filtration into Aquaponics: Effects on Particle Size Distribution and Turbidity Removal Zied Khiaria,*, Kumari Alkaa, Stephen Kellowayb, Beth Masonb, Nick Savidova a
Centre for Applied Research, Innovation and Entrepreneurship (CARIE) – Aquaculture Centre of Excellence (ACE). Lethbridge College. 3000 College Drive South, Lethbridge, Alberta, T1K 1L6, Canada b Verschuren Centre for Sustainability in Energy and the Environment. Cape Breton University. 1250 Grand Lake Road, Sydney, Nova Scotia, B1P 6L2, Canada
ARTICLE INFO
ABSTRACT
Keywords: aquaponics biochar filtration particle size distribution turbidity.
Small- and large-scale biochar-based filtrations were conducted to investigate the potential of biochar as a lowcost renewable filtration medium in aquaponics. The small-scale experimental design investigated the effects of 2 biochar media sizes (1 – 3 mm [referred to as fine biochar] and 3 – 5 mm [referred to as coarse biochar]), 3 biochar bed heights (2.5, 5.0 and 10.0 cm) and 3 loading rates (5, 10 and 15 m3/m2/d) on particle size distribution as well as turbidity removal efficiency. Both biochar sizes (fine and coarse) were able to clarify fish effluent. However, fine biochar led to better filtration characteristics compared to coarse biochar. Results indicated that biochar filter bed heights and loading rates affected the filtration performances. Using deeper filters combined with lower loading rates led to greater removal of suspended particles and turbidity compared to shallower filters and/or higher loading rates. Results from the large-scale filtration, using a mixture of fine and coarse biochar media (size of 1 – 5 mm), revealed that the ideal loading rate for maximizing the removal of turbidity from fish effluent in high-intensity aquaponic system for production of Nile tilapia and greenhouse plants (with 80 m3 total volume of water, 40 kg/m3 average stocking density and 15 kg/d feeding rate) was 10 m3/m2/d. This study suggests that biochar-based filtration could be incorporated into aquaponics as a polishing step before sending the water to plant growth systems.
1. Introduction The aquaculture industry is one of the fastest growing food-producing sectors in the world. According to the most recent estimates by the Food and Agriculture Organization of the United Nations (FAO), the global aquaculture production (both marine and inland) reached 80 million tons in 2016 (FAO, 2018) which accounted for 50% of the total seafood supply (Abate et al., 2016). Despite its considerable positive economic impacts, fish farming is associated with several environmental challenges such as significant water consumption and discharge of biologically unstable solid waste and nutrient-rich effluent (Turcios and Papenbrock, 2014; Wang et al., 2016). In order to alleviate these issues, more environmentally-friendly and sustainable fish farming technologies have been proposed, including recirculating aquaculture systems (RAS) and aquaponics (Ebeling and Timmons, 2012; Khiari et al., 2019; Savidov et al., 2007). Recirculating aquaculture systems (RAS) represent a technology for intensive fish farming where the water is recirculated to the fish culture tanks after mechanical and biological treatments (Badiola et al., 2012;
⁎
Van Rijn, 2013). RAS are capable of recycling more than 90% of the water (Badiola et al., 2012), which leads to reduction in both water consumption and effluent discharge. Biological filtration, though mandatory, is not sufficient on its own to guarantee adequate water quality for fish farming and therefore, other treatment processes (such as ozonation) are often required to remove organic carbon and turbidity (Gonçalves and Gagnon, 2011). Aquaponics, on the other hand, is a technology based on the co-production of fish and plants in one integrated system (Khiari et al., 2019; Savidov et al., 2007). In aquaponics, fish provide the required nutrients for plant growth, and in turn, plants absorb these nutrients decreasing their concentrations in the water, which is subsequently recycled back to the fish tanks (Medina et al., 2016). Biologically, aquaponics is an integrated multi-trophic system, which mimics the same interactions as those in natural ecosystems (Nichols and Savidov, 2012). Nitrification is just one of the processes in such ecosystems, where aerobic microorganisms convert ammonia (a toxic metabolite for fish) into nitrite and ultimately nitrate, which is considered the preferred form of nitrogen for plant growth (Khiari et al., 2019). The most significant benefits of aquaponics
Corresponding author. E-mail address: [email protected] (Z. Khiari).
https://doi.org/10.1016/j.agwat.2019.105874 Received 13 August 2019; Received in revised form 15 October 2019; Accepted 16 October 2019 0378-3774/ © 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Zied Khiari, et al., Agricultural Water Management, https://doi.org/10.1016/j.agwat.2019.105874
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
compared to RAS include increased revenue through the production of marketable vegetable crops (Savidov et al., 2007) as well as the reduced release of plant nutrients into the environment (since RAS require about 5 – 10% daily effluent discharge and fresh water renewal to lower the concentration of nitrate and other soluble minerals, which would otherwise accumulate in recirculated fish effluent (Van Bussel et al., 2012)). In this regard, several research studies indicated that plantbased removal of nutrients from fish effluent, through aquaponics, leads to more than 60% reduction in nitrate concertation and over 80% decrease in phosphorus level (Adler et al., 2003; Adler et al., 2000a; Adler et al., 2000b). The introduction of RAS and aquaponics into aquaculture practices resulted in significant advantages to the aquaculture industry and the environment. However, in order to achieve maximum RAS and aquaponics performance, a careful system design, a strict water quality control program and an optimum waste management strategy are required (Van Rijn, 2013; Wang et al., 2016). In both systems, ammonia removal and solids capture are the most critical treatment processes. In current industrial operations, ammonia removal is achieved through aerobic biological conversion to nitrate, while solids are separated from the water through mechanical filtration (such as drum and screen filters, floating bed filters and submerged high-pressure sand filters). The presence of organic solids can be extremely problematic for aquaponics. For instance, the biological decay of unconsumed feed and fecal matter lowers the oxygen level and generates toxic metabolites (Rakocy, 1994). In addition, the accumulation of organic debris in soilless crop production (such as aquaponic rafts and vertical towers) can plug the pipes and hinder drainage (Somerville et al., 2014). The problem of particle accumulation can be even more damaging on the root zone of the plants, as clogging the roots deprives them of adequate oxygen supply due to anaerobic decomposition of trapped debris (Rakocy et al., 2006, 2011; Rakocy, 1994). This, in turn, leads to severe plant stress and less resistance to root-borne diseases (such as Pithum) causing the ultimate failure of the plant production system. Although large-sized particles in fish effluent (≥ 30 μm) can be removed using conventional filtration methods, the challenge lies in the removal of smaller suspended micro- and nano-particles (Wang et al., 2016). Typically, particles below 30 μm are chemically removed through coagulation and/or flocculation (Tociu et al., 2014). Ozonation can also remove small particles. However, ozone application leads to the removal of dissolved organic compounds (Gonçalves and Gagnon, 2011) and thus deprives plants from important nutrients present in fish effluent. So far, there is no available technology, which can efficiently remove suspended particles from aquaculture effluents while retaining valuable plant nutrients. Biochar, also termed charcoal or biomass-derived black carbon, is a carbonaceous material produced from organic feedstock through pyrolysis (Meyer et al., 2011). The pyrolysis process leads to formation of a highly stable material with a complex network of interspersed tunnels with various pore sizes. Biochar porosity has been recognized as a desirable characteristic for numerous industrial applications. However, there was no in-depth study on biochar application for the removal of micro-particles and as a soilless growing medium until early 2000s when research investigations carried out by Savidov and Nichols (2010), Nichols et al. (2010) and Khan et al. (2015) indicated that biochar was not just a viable alternative to existing growing materials, but also exceeded them in terms of durability and crop yields. In addition to its role as a soilless growing medium, biochar can also function as a micro-filter when used in grow bags in aquaponics and organic hydroponics (Savidov, 2013). Another study also demonstrated the value of biochar in integrated fish and plant systems (Legault and Savidov, 2015). The following work is a continuation of unpublished work conducted at the Aquaculture Centre of Excellence (Lethbridge College) demonstrating and defining the microfiltration properties of biochar. The aims of this work were to (1) investigate biochar as a potential
low-cost renewable filtration medium in aquaponics, (2) optimize the biochar-based filtration process in a small-scale experimental set-up and (3) verify the outcomes in a large-scale biochar filter, incorporated within a high-intensity industrial aquaponic system. 2. Material and Methods 2.1. Materials 2.1.1. Fish effluent Fish effluent was obtained from a high-intensity aquaponic system of Nile tilapia (Oreochromis niloticus). In this system, fish effluent was first filtered through a drum filter (P.R.A. Manufacturing Ltd., Nanaimo, BC, Canada), which separated the liquid fraction (i.e. fish effluent rich in ammonia) from solid particulates (i.e. manure comprising unconsumed feed and fecal matter). Ammonia-rich fish effluent underwent a nitrification step within the fluidized-sand biofilter (biological filtration through aerobic nitrifying bacteria, mainly Nitrosomonas and Nitrobacter). This step initially converted ammonia into nitrite and subsequently into nitrate. Plants, in the greenhouse, absorbed nitrate and other soluble minerals reducing their concentrations in water, which was circulated back to the fish tank after oxygenation. The total volume of the water in this system was about 80 m3 and the average stocking density (weight of fish per unit volume of water) was approximately 40 kg/m3. The feeding rate of the fish was 15 kg/d with a fish feed (tilapia float 3.5 mm) comprising 40% crude protein, 9% crude fat and 10% ash (Skretting, Vancouver, BC, Canada). For the small- and large-scale filtration experiments, the water was collected after passing through the fluidized-sand biofilter and before delivery to the greenhouse. 2.1.2. Biochar Bamboo biochars, referred to as fine (with a particle size of 1 – 3 mm) and coarse (with a particle size of 3 – 5 mm), were separately used as filtration media. Biochar samples were prepared from the same bamboo feedstock and were divided after pyrolysis into different sizes (fine and coarse) using an industrial sieving machine. The biochars, used in this study, were prepared by Sungro Bioresource & Bioenergy Technologies Corp. (Edmonton, AB, Canada) and supplied by Pure Life Global Inc. (Calgary, AB, Canada). 2.2. Methods 2.2.1. Pretreatment Biochar samples (fine and coarse) were initially rinsed under cold tap water to remove dust and lower the pH of biochar to neutrality and then air-dried at 25 °C. 2.2.2. Biochar characterization 2.2.2.1. Density and total porosity. Bulk density was measured according to EBC guidelines (EBC, 2016). True density was determined at the Green Catalysis Research Group at University of Calgary (Calgary, AB, Canada) using an AccuPyc II 1340 pycnometer with helium as the displacement medium. Total porosity was calculated according to the following equation (Somerville and Jahanshahi, 2015):
Total Porosity (%) = 100 × 1
Bulk density True density
(1)
2.2.2.2. Scanning electron microscopy (SEM). The surface morphology of biochar was examined with a compact scanning electron microscope (Pemtron PS-230, Seoul, Korea). Biochar samples were first fixed using a double-sided carbon adhesive tape on an aluminum stub then gold coated by sputter coater and viewed at an acceleration voltage of 10.0 kV (Ghaffar et al., 2015). The scanning electron microscopy (SEM) 2
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
analysis was carried out at the Verschuren Centre for Sustainability in Energy and the Environment at Cape Breton University (Sydney, NS, Canada).
Table 1 Experimental design for small-scale biochar-based filtration.
2.2.3. Biochar-based filtration of fish effluent in aquaponics 2.2.3.1. Filter set-up. For the small-scale experiments, 3 biochar filters with various bed heights (2.5, 5.0 and 10.0 cm) were prepared for both fine and coarse biochars. Each filter was constructed using a polyvinyl chloride (PVC) pipe cap, with an internal diameter of 16.0 cm. An opening (with a diameter of 2.0 cm) was drilled in the center of PVC pipe cap, which served as the filter outlet port (Figure S1 A, Supplementary material). The internal surface of the filter was covered with a commercial landscaping polypropylene fabric in order to prevent the biochar from escaping. The large-scale biochar filter consisted of a cylindrical, fiberglass tank with a diameter of 2.4 m. An opening on the bottom center of the tank (with a diameter of 7.6 cm) was used as the outlet port (Figure S1 B, Supplementary material). The internal surface of the tank was covered with the same commercial landscaping polypropylene fabric that was used for the small-scale filters. The tank was filled with equal amounts of fine and coarse biochars (ratio 50:50, resulting in a biochar mixture with a size of 1 – 5 mm) to a height of 1.0 m based on literature for sand filters, which suggested an effective filtration media size of 2 – 4 mm and a recommended filter depth of 1 – 2 m (Zouboulis et al., 2007).
Flow rate ×(radius of the filter) 2
Filter bed height (cm)
Loading rate (m3/m2/d)
Filter bed height
Loading rate
1 2 3 4 5 6 7 8 9
2.5 2.5 2.5 5.0 5.0 5.0 10.0 10.0 10.0
5 10 15 5 10 15 5 10 15
−1 −1 −1 0 0 0 +1 +1 +1
−1 0 +1 −1 0 +1 −1 0 +1
(-1) denotes low level, (0) denotes medium level and (+1) denotes high level.
Relative span factor (RSF) =
(Dv90 Dv10) Dv50
(3)
A smaller RSF value indicates a narrower and more uniform particle size distribution (Phat et al., 2015). 2.2.4.2. Turbidity. Turbidity was measured using Smart Spectro spectrophotometer (LaMotte, Chestertown, MD, USA). Results, expressed as Formazin Turbidity Unit (FTU), were converted into turbidity removal percentage as follows:
Turbidity removal (%) = 100 (Turbidity before filtration Turbidity after filtration) × Turbidity before filtration
2.2.3.2. Filtration conditions. Before performing the filtration experiments, 10 L of deionized water was loaded onto each smallscale filter, while the large-scale filter was sprinkled with tap water. This pre-treatment operation was carried out to moisten and pack the biochar media as well as to flush out any residual dust and impurities. Fish effluent samples obtained after undergoing a biological treatment in the fluidized-sand biofilter, were used in this study. For both smalland large-scale biochar filtrations, 3 different loading rates (5, 10 and 15 m3/m2/d) were assessed. The loading rate was calculated as the flow rate divided by the surface area of the filter (m2) as follows:
Loading rate (m3/ m2 /d) =
Run
(4) 2.2.5. Statistics In the small-scale filtration experiments, three-level (low, medium and high), two-factor (biochar bed height and loading rate) factorial design of nine runs was performed for each biochar size (fine and coarse). The experimental design comprised all possible combinations of values for each factor (Table 1). The filtration experiments (both small-scale and large-scale) were replicated three times on three different occasions (3 independent trials). New biochar filters were prepared for each replicate during small-scale filtrations while for largescale filtrations, the biochar bed was turned over before each trial. Each analysis was performed in triplicate for each trial. Analysis of variance (ANOVA) was used and multiple range test Tukey’s honestly significant difference (P < 0.05) was conducted to determine differences between means. In small-scale experiments, the model tested the filtration conditions (biochar size, biochar bed height and loading rate) as fixed effects. In large-scale experiments, the model tested the loading rate as a fixed effect. For both scales (small and large), the filtration day (filtration replicate) was considered as a random effect. All statistical analyses were performed using Statistical Analysis Software (SAS University Edition, SAS Institute Inc., Cary, NC) and letter groupings were obtained using the SAS PDMIX800 macro (Saxton, 1998).
(2)
A series of valves were used to control the filtration at the desired loading rate. Adjustable micro sprayers (for small-scale filters) and mini spray nozzle sprinklers (for the large-scale filter) were used to uniformly apply the fish effluent on the top surface of the filters. Fish effluent was allowed to pass through the filters then samples were collected in 50 mL plastic tubes and analyzed within 2 hours after collection. 2.2.4. Characterization of biochar-based filtration 2.2.4.1. Particle size distribution. Particle size distribution was obtained using a Multi-Wavelength Laser Diffraction Particle Size Analyzer (LS 13 320, Beckman Coulter, Inc., Brea, CA, USA) fitted with a micro liquid module (with a 12 mL working volume). Data of the particles size distribution, with size ranging from 0.375 to 2000 μm, were obtained by Beckman Coulter Particle Characterization Software (version 6.01). Several particle size data were reported in this study including, the volume-weighted mean diameter (De Broukere mean, D[4,3], which denotes the weighted average volume diameter assuming spherical particles of the same volume as the real particles (Byrn et al., 2017)) as well as Dv10, Dv50 (volume median diameter) and Dv90 which respectively represent the size below which 10, 50 and 90% of the sample volume exists. In order to describe the particle size distribution, the relative span factor (RSF), which is a dimensionless parameter reflecting the uniformity of the particle size distribution (Čižauskaitė et al., 2017), was calculated as follows (Van Snick et al., 2018):
3. Results and Discussion 3.1. Biochar characterization 3.1.1. Physical properties of bamboo biochars The density and porosity of fine and coarse bamboo biochars are summarized in Table 2. The bulk density is an important characteristic that is indicative of the presence of pores and reflects the ability of biochar to sink or float in water given the pores are air-filled (Brewer et al., 2014). The bulk density of fine biochar (0.366 g/cm3) was two times greater than that of coarse biochar (0.176 g/cm3), which was mainly due to differences in size and shape. In fact, as the size of particles increases, the bulk density decreases (Bitra et al., 2009). True 3
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
density, in which the volume of intra-particle pores and voids between particles are excluded (Hung et al., 2017), indicated that the 2 sizes of bamboo biochar were fairly similar. This was expected because both biochar samples were prepared from the same feedstock at the same pyrolysis conditions. When comparing porosity, coarse biochar had greater total porosity (89.1%) than fine biochar (76.2%). Since both biochar samples had similar true density, the lower total porosity in fine biochar could be attributed to less voids between particles (inter-pores) compared to coarse biochar.
Table 2 Density and total porosity of fine and coarse bamboo biochars. Physical Characteristics
Fine Biochar
Coarse Biochar
Bulk density (g/cm3) True density (g/cm3) Total porosity (%)
0.366 1.541 76.25
0.176 1.613 89.09
3.1.2. Scanning electron microscopy (SEM) Fig. 1 shows typical SEM micrographs of the external morphology of a randomly selected bamboo biochar sample at 3 different magnification levels. SEM images revealed the porous structure of bamboo biochar with relatively uniform pores, in micrometer range, forming a honeycomb-like morphology and reflecting a typical structure of xylem tissue. In general, the pyrolysis process leads to the release of volatile components in the feedstock and the non-volatile matter is converted into porous biochar with voids of various shapes and sizes (Liew et al., 2018). The SEM analysis was in agreement with the porosity result, which indicated that bamboo biochar was mainly composed of a porous structure, with the majority of pores between 30 and 60 microns. Both intra-pores and inter-pores of bamboo biochar could play a major role in filtration of fish effluent in aquaponics. In this respect, the removal of particulate matter and turbidity could be achieved by either trapping the particles within the intra-pores of biochar, wedging them between convex surfaces of two biochar grains (i.e. retention in crevice sites), holding them in a sheltered areas developed by several biochar grains (i.e. retention in cavern sites), or a combination of these processes (Benamar et al., 2007; Herzig et al., 1970; Zamani and Maini, 2009). It is important to note that several factors, such as, shape, size and density of the particles, the grain size and porosity of biochar, the chemical properties and flow rate of the effluent, as well as the interaction forces between the particles and biochar media significantly affect the retention of particles and therefore, significantly affect the overall filtration through porous media, such as biochar (Gao, 2007; Herzig et al., 1970; Sabiri et al., 2017). 3.2. Small-scale biochar-based filtration of fish effluent in aquaponics 3.2.1. Particle size distribution Fig. 2 shows the particle size distribution curves of fish effluent before and after small-scale biochar filtration while Table 3 presents the particle size data of fish effluent after small-scale biochar filtration using fine and coarse biochars. For all loading rates and all biochar bed heights, it was clear that the particle size distribution of the inflow water (before filtration) was significantly greater than the outflow water (after filtration) (Fig. 2). For all loading rates tested in this study, the inflow water had a broad fraction of larger-size particles with D [4,3] varying from 71.0 to 75.3 μm, Dv10 ranging from 14.1 to 14.5 μm, Dv50 varying from 47.8 to 51.9 μm, Dv90 ranging from 165.4 to 172.1 μm and RSF extending from 3.0 to 3.2. After biochar filtration, the particle size distribution of outflow significantly decreased (P < 0.05) compared to the inflow at all loading rates (5, 10, and 15 m3/m2/d) and for all biochar bed heights (2.5, 5.0 and 10.0 cm). The size of biochar (fine and coarse), the loading rate, the biochar bed height as well as their interactions had statistically significant effects on the particle size distribution of the outflow (Table 3). When considering the sole effect of biochar size (fine and coarse), the results indicated that biochar size impacted the particle distribution characteristics of the outflow. Using fine biochar resulted in outflow with significantly lower D[4,3], Dv10, Dv50, Dv90 and RSF compared to coarse biochar (Table 3). The better particle size characteristics of the outflow obtained with fine biochar could be attributed to the porosity of fine biochar (as discussed in section 3.1.1), where the smaller inter-pore size between fine biochar grains could have retained more particles
Fig. 1. Scanning electron microscopy images of bamboo biochar. Figure A shows a micrograph at a low magnification level (×237); Figure B shows a micrograph at a medium magnification level (×411); and Figure C shows a micrograph at a high magnification level (×1,600).
4
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
Fig. 2. Particle size distribution curves for small-scale biochar-based filtration. Figure A: filtration using fine biochar at a loading rate of 5 m3/m2/d; Figure B: filtration using coarse biochar at a loading rate of 5 m3/m2/d; Figure C: filtration using fine biochar at a loading rate of 10 m3/m2/d; Figure D: filtration using coarse biochar at a loading rate of 10 m3/m2/d; Figure E: filtration using fine biochar at a loading rate of 15 m3/m2/d; Figure F: filtration using coarse biochar at a loading rate of 15 m3/m2/d. LR 5: loading rate of 5 m3/m2/d; LR 10: loading rate of 10 m3/m2/d; LR 15: loading rate of 15 m3/m2/d.
suspended in fish effluent. In addition, the surface area of fine biochar may also have played a role in improving particle capture efficiency. In this regard, fine biochar is believed to possess greater surface area
compared to coarse biochar as size reduction increases surface area (Peterson et al., 2012) which may have resulted in greater adsorption of particles (Zheng et al., 2012). 5
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
Table 3 Particle size characteristics for small-scale biochar-based filtration. Biochar Size Outflow
P-value
Fine Fine Fine Fine Fine Fine Fine Fine Fine Coarse Coarse Coarse Coarse Coarse Coarse Coarse Coarse Coarse Effect of Effect of Effect of Effect of Effect of Effect of Effect of
Bed Height (cm)
Loading Rate (m3/m2/d)
2.5 5 5.0 5 10.0 5 2.5 10 5.0 10 10.0 10 2.5 15 5.0 15 10.0 15 2.5 5 5.0 5 10.0 5 2.5 10 5.0 10 10.0 10 2.5 15 5.0 15 10.0 15 biochar size bed height biochar size × bed height loading rate biochar size × loading rate bed height × loading rate biochar size × bed height × loading rate
D[4,3] μm
Dv10 μm
Dv50 μm
Dv90 μm
RSF
20.40 ± 0.54d 19.20 ± 0.08d 18.83 ± 0.32d 20.73 ± 1.13d 19.68 ± 0.40d 19.62 ± 0.14d 21.01 ± 1.14d 19.34 ± 0.40d 18.95 ± 0.30d 19.45 ± 0.28d 19.16 ± 0.08d 19.03 ± 0.27d 30.55 ± 2.47b 26.74 ± 1.94c 26.15 ± 2.49c 38.95 ± 4.05a 29.81 ± 4.11b 28.34 ± 1.75bc < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001
8.90 ± 0.26abcd 8.04 ± 0.09efg 7.67 ± 0.28fg 8.14 ± 0.60defg 7.94 ± 0.40efg 8.55 ± 0.09abcde 8.51 ± 0.34bcde 8.34 ± 0.21def 7.46 ± 0.12g 8.00 ± 0.24efg 8.37 ± 0.08cdef 8.70 ± 0.21abcde 9.36 ± 0.37a 9.35 ± 0.13ab 9.19 ± 0.16abc 9.33 ± 0.53ab 7.59 ± 1.48fg 5.70 ± 1.05h 0.0058 < 0.0001 0.0638 < 0.0001 < 0.0001 < 0.0001 < 0.0001
20.37 ± 0.42abc 19.04 ± 0.04cde 18.75 ± 0.14cde 19.26 ± 0.58bcde 19.01 ± 0.27cde 19.16 ± 0.07bcde 18.35 ± 3.10e 19.03 ± 0.12cde 18.71 ± 0.07de 19.15 ± 0.15bcde 18.84 ± 0.06cde 18.92 ± 0.12cde 21.00 ± 0.76a 20.71 ± 0.41ab 20.21 ± 0.26abcd 20.98 ± 2.28a 19.63 ± 0.82abcde 18.93 ± 0.26cde < 0.0001 0.0006 0.3238 0.0004 < 0.0001 0.6385 0.0012
31.09 ± 0.85d 29.41 ± 0.15d 28.75 ± 0.63d 32.35 ± 1.69d 30.24 ± 0.53d 30.10 ± 0.31d 32.34 ± 1.74d 29.76 ± 0.60d 29.05 ± 0.52d 29.94 ± 0.28d 29.37 ± 0.22d 28.98 ± 0.41d 74.64 ± 9.07b 48.91 ± 12.20c 45.75 ± 12.42c 109.58 ± 12.05a 74.37 ± 21.98b 72.09 ± 8.40b < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001
1.09 ± 0.02e 1.12 ± 0.01e 1.12 ± 0.01e 1.26 ± 0.05de 1.17 ± 0.03de 1.12 ± 0.02e 1.36 ± 0.42cde 1.13 ± 0.03e 1.15 ± 0.02e 1.15 ± 0.01e 1.11 ± 0.01e 1.07 ± 0.01e 3.10 ± 0.36b 1.90 ± 0.55c 1.80 ± 0.59cd 4.84 ± 0.86a 3.37 ± 0.93b 3.51 ± 0.44b < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 0.0055
Values are given as mean ± standard deviation. a-h Means within the same column sharing a common letter are not significantly different from each other.
Increasing the loading rate decreased Dv10 and increased D[4,3], Dv50, Dv90 and RSF of the outflow (Table 3). The effect of increasing the loading rate on filtration performances was more profound for coarse biochar compared to fine biochar (Fig. 2 and Table 3). This phenomenon (i.e. decrease of filtration performance at higher loading rates) was previously reported for the filtration of wastewater (DuranRos et al., 2009; Williams et al., 2007) and was attributed to reduction of transport time due to higher velocities, as well as to the decline of particle attachment efficiency as a result of hydrodynamic forces (Williams et al., 2007). In addition, high loading rates can result in the dissociation of attached particles and the breakage of large particles because of shear forces (Boller and Blaser, 1998; Kim and Lawler, 2012) which consequently may have affected the particle size distribution, as depicted in Fig. 2 and Table 3. Unlike the loading rate, increasing the height of biochar bed from 2.5 cm to 5.0 cm decreased the range of particle size distribution (Fig. 2) as well as the particle size data (Table 3). Similar trends (i.e. enhancement of filtration performance with higher filter bed) have been observed for the removal of particulate matter and contaminants using activated carbon (Areerachakul et al., 2007), pumice, a porous volcanic rock (Farizoglu et al., 2003) and sand (Torrens et al., 2009). Subsequent increase of biochar filter bed height from 5.0 cm to 10.0 cm did not result in improvement of fish effluent filtration. The enhanced removal of larger particles with deeper biochar bed could be due to a greater detention time as well as higher surface area for the retention of particles (Farizoglu et al., 2003).
measurement (turbidity values and turbidity removal percentages) of outflow after biochar filtration are presented in Table 4. The turbidity values ranged from 15.22 to 31.11 FTU while the turbidity removal efficiencies varied from 60.47% to 80.66% depending on biochar size, loading rate, and biochar bed height. When comparing the effect of 2 biochar sizes, it was found that using fine biochar led to lower turbidity values and better turbidity removal percentages compared to coarse biochar. This could be attributed to the lower total porosity and the greater surface properties of fine biochar which may have resulted in better capture of particles. In fact, particle removal during filtration occurs through the transport of particulate matter and suspended solids from the inflow into the filtration media followed by their capture by either adsorption (due to Brownian motion and electrostatic interactions between the particles and the surface of the pores), size exclusion/ straining (due to size difference between the particles and the pore openings) and/or sedimentation/gravity settling (due to density difference between the particles and the carrying effluent) (Gao, 2007). Results also indicated that increasing the loading rate and/or decreasing the biochar bed height negatively impacted the turbidity removal efficiency. For filtration using fine biochar, the lowest turbidity value and the greatest turbidity removal percentage (15.22 FTU and 80.66%, respectively) were obtained at the lowest loading rate (5 m3/ m2/d) and the highest bed height (10.0 cm) (Table 4) while the lowest turbidity values (24.22 – 24.33 FTU) and the greatest turbidity removal efficiencies (69.08 – 69.22%) for coarse biochar were observed at 5 m3/ m2/d using 5.0 and 10.0 cm biochar bed heights (Table 4). Increasing the loading rate and/or decreasing the bed height caused the opposite effect (Table 4). In this regards, the greatest turbidity values and the lowest turbidity removal efficiencies for fine and coarse biochars were observed at 10 and 15 m3/m2/d using 2.5 cm bed height. After filtration, all waters were visually clear with light yellowish–brownish color, which was most probably due to the presence of dissolved humic matter. The turbidity results strongly indicated that biochar possessed the capacity to retain particles and clarify aquaponic effluents.
3.2.2. Turbidity removal efficiency Turbidity reflects the presence of suspended and dissolved solids that absorb or scatter light. As a water quality parameter, turbidity has a great significance in aquaculture and aquaponics because high turbidity reduces dissolved oxygen (Henley et al., 2000) and consequently turbid environments lose their ability to maintain healthy plants and aquatic organisms (Bisinoti et al., 2007). The inflow in this study had a turbidity value of 77.44 ± 2.01 FTU. Results from the turbidity
6
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
3.3. Large-scale biochar-based filtration of fish effluent in aquaponics
Table 4 Turbidity values and turbidity removal percentages for small-scale biocharbased filtration. Biochar Size
Bed Height (cm)
Loading Rate (m3/m2/d)
Outflow Fine 2.5 5 Fine 5.0 5 Fine 10.0 5 Fine 2.5 10 Fine 5.0 10 Fine 10.0 10 Fine 2.5 15 Fine 5.0 15 Fine 10.0 15 Coarse 2.5 5 Coarse 5.0 5 Coarse 10.0 5 Coarse 2.5 10 Coarse 5.0 10 Coarse 10.0 10 Coarse 2.5 15 Coarse 5.0 15 Coarse 10.0 15 P-value Effect of biochar size Effect of bed height Effect of biochar size × bed height Effect of loading rate Effect of biochar size × loading rate Effect of bed height × loading rate Effect of biochar size × bed height × loading rate
Turbidity (FTU)
Turbidity Removal (%)
25.78 ± 0.83gh 18.22 ± 1.39i 15.22 ± 1.30j 31.11 ± 0.93a 26.00 ± 0.71fgh 26.89 ± 1.45efg 31.11 ± 1.90a 27.89 ± 2.41cdefg 29.11 ± 2.15abcd 26.78 ± 1.64efg 24.22 ± 1.72h 24.33 ± 0.71h 29.33 ± 0.71abc 27.11 ± 0.78defg 26.22 ± 1.48fgh 30.56 ± 1.01ab 28.89 ± 0.60bcde 28.11 ± 1.45cdef < 0.0001 < 0.0001 < 0.0001
67.25 ± 1.06cd 76.85 ± 1.77b 80.66 ± 1.65a 60.47 ± 1.18j 66.96 ± 0.90cde 65.83 ± 1.85def 60.47 ± 2.41j 64.56 ± 1.61defg 63.01 ± 2.73ghij 65.97 ± 2.09def 69.22 ± 2.18c 69.08 ± 0.90c 62.73 ± 0.90hij 65.55 ± 0.99defg 66.68 ± 1.88cde 61.17 ± 1.29ij 63.29 ± 0.76fghi 64.28 ± 1.85efgh < 0.0001 < 0.0001 < 0.0001
< 0.0001 < 0.0001
< 0.0001 < 0.0001
< 0.0001
< 0.0001
< 0.0001
< 0.0001
Fig. 3 and Table 5 show, respectively, the particle size distribution curves and particle size distribution data for fish effluent after filtration using the large-scale biochar filter at 3 loading rates (5, 10 and 15 m3/ m2/d). Particle size analysis of the inflow water for large-scale biochar filtration indicated that D[4,3] varied from 64.9 to 72.6 μm, Dv10 ranged from 13.4 to 14.2 μm, Dv50 varied from 38.0 to 46.6 μm, Dv90 ranged from 162.6 to 177.0 μm and RSF extended from 3.5 to 3.9. Similar to small-scale outcomes, large-scale biochar filtration resulted in significant reduction of particle size distributions of fish effluent (Fig. 3). For all loading rates, D[4,3] was reduced by more than 90%, Dv10 and Dv90 dropped by more than 94% while Dv50 decreased by more than 84%. Increasing the loading rate from 5 m3/m2/d to 10 m3/ m2/d and subsequently to 15 m3/m2/d broadened the particle distribution of the outflow (Fig. 3) and significantly increased the values of the mean, median and the two percentiles Dv10 and Dv90 as well as the RSF (Table 5). The loading rate, in the large-scale biochar-based filtration, also significantly affected the turbidity values and the turbidity removal efficiencies. In this respect, increasing the loading rate from 5 m3/m2/d to 15 m3/m2/d significantly increased the turbidity values from 12.89 to 16.89 FTU and lowered the turbidity removal efficiencies from 83.35% to 78.18% (Table 6). The turbidity value (13.78 FTU) and the turbidity removal efficiency (82.20%) at 10 m3/m2/d were slightly lower than that obtained using a loading rate of 5 m3/m2/d (Table 6), however, the differences were not statistically significant (P > 0.05). Regardless of the loading rate, the turbidity of the outflow from largescale biochar filter ranged from 12.89 ± 0.60 to 16.89 ± 0.78 FTU. These turbidity values indicated that biochar-filtered fish effluents were suitable for re-use in aquaculture as their turbidity fell within the acceptable range (5 - 25 NTU/FTU) for domestic use (Drever, 2002) and did not exceed the maximum allowable value of 25 NTU/FTU for aquaculture use (EPA, 1988). Outcomes from the large-scale filtration experiments indicated that using a biochar filter with a media size of 1 – 5 mm (a mixture of fine and coarse biochars) at a loading rate of 10 m3/m2/d were the ideal
Values are given as mean ± standard deviation. a-j Means within the same column sharing a common letter are not significantly different from each other.
Fig. 3. Particle size distribution curves for large-scale biochar-based filtration. LR 5: loading rate of 5 m3/m2/d; LR 10: loading rate of 10 m3/m2/d; LR 15: loading rate of 15 m3/m2/d.
7
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
Table 5 Particle size characteristics for large-scale biochar-based filtration.
Outflow P-value
Loading Rate (m3/m2/d)
D[4,3] μm
Dv10 μm
Dv50 μm
Dv90 μm
RSF
5 10 15 Effect of loading rate
4.95 ± 0.31c 5.74 ± 0.13b 6.01 ± 0.11a < 0.0001
0.66 ± 0.07c 0.82 ± 0.02b 0.91 ± 0.04a < 0.0001
5.97 ± 0.33b 6.48 ± 0.26a 6.37 ± 0.39a 0.0074
7.34 ± 0.55c 9.57 ± 0.49b 10.77 ± 0.50a < 0.0001
1.12 ± 0.07c 1.35 ± 0.11b 1.56 ± 0.18a < 0.0001
Values are given as mean ± standard deviation. a-c Means within the same column sharing a common letter are not significantly different from each other.
4. Conclusion
Table 6 Turbidity values and turbidity removal percentages for large-scale biocharbased filtration.
Outflow P-value
Loading Rate (m3/m2/d)
Turbidity (FTU)
Turbidity Removal (%)
5 10 15 Effect of loading rate
12.89 ± 0.60b 13.78 ± 0.97b 16.89 ± 0.78a < 0.0001
83.35 ± 0.78a 82.20 ± 1.26a 78.18 ± 1.01b < 0.0001
Based on the present study, biochar represents a promising potential low-cost renewable biomass for aquaponic effluent filtration. The porous structure of biochar makes it very suitable for the retention of suspended particles and removal of turbidity. The quality of filter outflow, in terms of particle and turbidity removal efficiencies clearly demonstrated that biochar-based filtration can be used in aquaponics to clarify fish effluent, most appropriately as a water polishing step (before sending the treated water plant growth systems) especially for fish species with higher demand for water quality, such as salmonids. Results also indicated that the performance of biochar-based filtration depends on the operational conditions (biochar media size, biochar filter bed height and loading rate). Despite these positive findings, further research is still required to fully confirm the advantages of biochar-based effluent filtration in highly-intensive aquaponic productions.
Values are given as mean ± standard deviation. a-b Means within the same column sharing a common letter are not significantly different from each other.
conditions for the removal of suspended particles and turbidity in highintensity fish farming/aquaponic operations. Biochar-based filtration, in such systems, could most suitably be incorporated as a polishing process before sending the water back to the plant growth systems (such as raft media bed and vertical tower) as shown in Fig. 4. It is important to note, however, that these recommendations are only applicable for aquaponic systems running under similar operational conditions, as fish species, feed composition, feeding rate, stocking density and water treatment processes can all affect total suspended solids and particulate density and nature.
5. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Fig. 4. Suggested placement of biochar filter in aquaponics for removal of particulate matter and turbidity.
8
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
Declaration of Competing Interest
State/Federal Criteria. United States Environmental Protection Agency, Office of Water Regulations and Standards, Washington, DC, pp. 1–20. FAO, 2018. The State of World Fisheries and Aquaculture 2018 - Meeting the sustainable development goals. Food and Agriculture Organization of the United Nations, Rome. Farizoglu, B., Nuhoglu, A., Yildiz, E., Keskinler, B., 2003. The performance of pumice as a filter bed material under rapid filtration conditions. Filtration & separation 40, 41–47. Gao, C., 2007. Factors affecting particle retention in porous media. Emirates Journal for Engineering Research 12, 1–7. Ghaffar, A., Ghosh, S., Li, F., Dong, X., Zhang, D., Wu, M., Li, H., Pan, B., 2015. Effect of biochar aging on surface characteristics and adsorption behavior of dialkyl phthalates. Environmental Pollution 206, 502–509. https://doi.org/10.1016/j.envpol. 2015.08.001. Gonçalves, A.A., Gagnon, G.A., 2011. Ozone Application in Recirculating Aquaculture System: An Overview. Ozone: Science & Engineering 33, 345–367. https://doi.org/ 10.1080/01919512.2011.604595. Henley, W.F., Patterson, M.A., Neves, R.J., Lemly, A.D., 2000. Effects of Sedimentation and Turbidity on Lotic Food Webs: A Concise Review for Natural Resource Managers. Reviews in Fisheries Science 8, 125–139. https://doi.org/10.1080/ 10641260091129198. Herzig, J.P., Leclerc, D.M., Goff, P. Le, 1970. Flow of Suspensions through Porous MedidApplicdtion to Deep Filtrdtion. Ind. Eng. Chem. 62, 8–35. Hung, C.Y., Tsai, W.T., Chen, J.W., Lin, Y.Q., Chang, Y.M., 2017. Characterization of biochar prepared from biogas digestate. Waste Management 66, 53–60. https://doi. org/10.1016/j.wasman.2017.04.034. Khan, A., Savidov, N., Zhang, J., Yang, J., Anderson, T., Harfield, D., Anyia, A.O., 2015. Biochar Substrate for Hydroponic Vegetable Production. In: Ok, Y.S., Uchimiya, S.M., Chang, S.X., Bolan, N. (Eds.), Biochar: Production, Characterization, and Applications. CRC Press, Taylor & Francis Group, Boca Raton, FL, pp. 274–291. Khiari, Z., Kaluthota, S., Savidov, N., 2019. Aerobic bioconversion of aquaculture solid waste into liquid fertilizer: Effects of bioprocess parameters on kinetics of nitrogen mineralization. Aquaculture 500, 492–499. https://doi.org/10.1016/j.aquaculture. 2018.10.059. Kim, J., Lawler, D.F., 2012. The influence of hydraulic loads on depth filtration. Water Research 46, 433–441. https://doi.org/10.1016/j.watres.2011.10.059. Legault, M., Savidov, N., 2015. Crop Production Platform Based On Aerobic Bio-Digestion Technology. Internal Report. Alberta Agriculture and Rural Development, BioIndustrial Opportunities Branch, Food and Bio-Processing Division. Liew, R.K., Nam, W.L., Chong, M.Y., Phang, X.Y., Su, M.H., Yek, P.N.Y., Ma, N.L., Cheng, C.K., Chong, C.T., Lam, S.S., 2018. Oil palm waste: an abundant and promising feedstock for microwave pyrolysis conversion into good quality biochar with potential multi-applications. Process Safety and Environmental Protection 115, 57–69. Medina, M., Jayachandran, K., Bhat, M.G., Deoraj, A., 2016. Assessing plant growth, water quality and economic effects from application of a plant-based aquafeed in a recirculating aquaponic system. Aquaculture international 24, 415–427. Meyer, S., Glaser, B., Quicker, P., 2011. Technical, Economical, and Climate-Related Aspects of Biochar Production Technologies: A Literature Review. Environmental Science & Technology 45, 9473–9483. https://doi.org/10.1021/es201792c. Nichols, M., Savidov, N., Aschim, K., 2010. Biochar as a Hydroponic Growing Medium. Practical Hydroponics and Greenhouses 112, 39–42. Nichols, M.A., Savidov, N.A., 2012. Aquaponics: a nutrient and water efficient production system. Acta Horticulturae. International Society for Horticultural Science (ISHS), Leuven, Belgium, pp. 129–132. https://doi.org/10.17660/ActaHortic.2012.947.14. Peterson, S.C., Jackson, M.A., Kim, S., Palmquist, D.E., 2012. Increasing biochar surface area: Optimization of ball milling parameters. Powder Technology 228, 115–120. https://doi.org/10.1016/j.powtec.2012.05.005. Phat, C., Li, H., Lee, D.U., Moon, B., Yoo, Y.B., Lee, C., 2015. Characterization of Hericium erinaceum powders prepared by conventional roll milling and jet milling. Journal of Food Engineering 145, 19–24. https://doi.org/10.1016/j.jfoodeng.2014.08.001. Rakocy, J., Masser, M.P., Losordo, T., 2006. Recirculating aquaculture tank production systems: Aquaponics – integrating fish and plant culture. Southern Regional Aquaculture Center (SRAC) Publication No. 454. Rakocy, J.E., 1994. Aquaponics: The integration of fish and vegetable culture in recirculating systems. In: Proceedings of the 30th Annual Meeting. Caribbean Food Crops Society, Saint Thomas. pp. 101–108. Rakocy, J.E., Bailey, D.S., Shultz, R.C., Danaher, J.J., et al., 2011. A commercial-scale aquaponic system developed at the University of the Virgin Islands. Proceedings of the 9th International Symposium on Tilapia in Aquaculture 336–343. Sabiri, N.E., Monnier, E., Raimbault, V., Massé, A., Séchet, V., Jaouen, P., 2017. Effect of filtration rate on coal-sand dual-media filter performances for microalgae removal. Environmental Technology (United Kingdom) 38, 345–352. https://doi.org/10. 1080/09593330.2016.1193224. Savidov, N., 2013. Supergrow (biochar) – greenhouse trials and commercial applications. Project #AB0512. ACIDF Official Report, Government of Alberta. Savidov, N., Nichols, M., 2010. Biochar – A New Hydroponic Growing Medium. 28th International Horticultural Congress 35. Savidov, N.A., Hutchings, E., Rakocy, J.E., 2007. Fish and plant production in a recirculating aquaponic system: a new approach to sustainable agriculture in Canada. Acta Horticulturae 742, 209–221. https://doi.org/10.17660/ActaHortic.2007. 742.28. Saxton, A.M., 1998. A macro for converting mean separation output to letter groupings. In: Proc Mixed. Proceedings of the 23rd SAS Users Group International. 22-25 Mar 1998, Nashville. pp. 1243–1246. Somerville, C., Cohen, M., Pantanella, E., Stankus, A., Lovatelli, A., 2014. Small-scale aquaponic food production: integrated fish and plant farming. FAO Fisheries and Aquaculture Technical Paper I.
None. Acknowledgements The Natural Sciences and Engineering Research Council of Canada (NSERC) and Alberta Innovates are gratefully acknowledged for providing funds under NSERC Engage and Campus Alberta Small Business Engagement (CASBE) Programs, respectively. Alberta Economic Development and Trade is acknowledged for financial support in purchasing the LS 13 320 Multi-Wavelength Laser Diffraction Particle Size Analyzer. The authors would like to thank John Derksen for reviewing the manuscript, Clay Boyes and Penny Takahashi for assistance in setting up biochar filters, Beckman Coulter Inc. for providing helpful technical support as well as Pure Life Global Inc. for in-kind contribution. Appendix A. Supplementary data Supplementary material related to this article can be found, in the online version, at doi:https://doi.org/10.1016/j.agwat.2019.105874. References Abate, T.G., Nielsen, R., Tveterås, R., 2016. Stringency of environmental regulation and aquaculture growth: A cross-country analysis. Aquaculture Economics & Management 20, 201–221. https://doi.org/10.1080/13657305.2016.1156191. Adler, P.R., Harper, J.K., Takeda, F., Wade, E.M., Summerfelt, S.T., 2000a. Economic evaluation of hydroponics and other treatment options for phosphorus removal in aquaculture effluent. HortScience 35, 993–999. Adler, P.R., Harper, J.K., Wade, E.M., Takeda, F., Summerfelt, S.T., 2000b. Economic Analysis of an Aquaponic System for the Integrated Production of Rainbow Trout and Plants. International Journal of Recirculating Aquaculture 1, 15–34. https://doi.org/ 10.21061/ijra.v1i1.1359. Adler, P.R., Summerfelt, S.T., Glenn, D.M., Takeda, F., 2003. Mechanistic approach to phytoremediation of water. Ecological Engineering 20, 251–264. https://doi.org/10. 1016/S0925-8574(03)00044-2. Areerachakul, N., Vigneswaran, S., Ngo, H.H., Kandasamy, J., 2007. Granular activated carbon (GAC) adsorption-photocatalysis hybrid system in the removal of herbicide from water. Separation and Purification Technology 55, 206–211. https://doi.org/ 10.1016/j.seppur.2006.12.007. Badiola, M., Mendiola, D., Bostock, J., 2012. Recirculating Aquaculture Systems (RAS) analysis: Main issues on management and future challenges. Aquacultural Engineering 51, 26–35. https://doi.org/10.1016/j.aquaeng.2012.07.004. Benamar, A., Ahfir, N.D., Wang, H.Q., Alem, A., 2007. Particle transport in a saturated porous medium: Pore structure effects. Comptes Rendus - Geoscience 339, 674–681. https://doi.org/10.1016/j.crte.2007.07.012. Bisinoti, M.C., Yabe, M.J.S., Gimenez, S.M.N., Simões, F., dos, S., Moreira, A.B., 2007. Water quality index as a simple indicator of aquaculture effects on aquatic bodies. Ecological Indicators 8, 476–484. https://doi.org/10.1016/j.ecolind.2007.05.002. Bitra, V.S.P., Womac, A.R., Miu, P.I., Chevanan, N., Sokhansanj, S., Yang, Y.T., Igathinathane, C., 2009. Bulk density and compaction behavior of knife mill chopped switchgrass, wheat straw, and corn stover. Bioresource Technology 101, 207–214. https://doi.org/10.1016/j.biortech.2009.07.083. Boller, M., Blaser, S., 1998. Particles under stress. Water Science and Technology 37, 9–29. Brewer, C.E., Chuang, V.J., Masiello, C.A., Gonnermann, H., Gao, X., Dugan, B., Driver, L.E., Panzacchi, P., Zygourakis, K., Davies, C.A., 2014. New approaches to measuring biochar density and porosity. Biomass and Bioenergy 66, 176–185. https://doi.org/ 10.1016/j.biombioe.2014.03.059. Byrn, S.R., Zografi, G., Chen, S., 2017. Solid state properties of pharmaceutical materials. Wiley Online Library. Čižauskaitė, U., Marksa, M., Bernatonienė, J., 2017. The optimization of technological processes, stability and microbiological evaluation of innovative natural ingredients based multiple emulsion. Pharmaceutical development and technology 2017, 1–10 vol. 00, iss. 00. Drever, J.I., 2002. The geochemistry of natural waters : Surface and groundwater environments LK, 3rd ed. Prentice Hall, Upper Saddle River, N.J. Duran-Ros, M., Puig-Bargués, J., Arbat, G., Barragán, J., Cartagena, F.R. de, 2009. Effect of filter, emitter and location on clogging when using effluents. Agricultural Water Management 96, 67–79. https://doi.org/10.1016/j.agwat.2008.06.005. EBC, 2016. Guidelines for a Sustainable Production of Biochar. European Biochar Foundation (EBC)https://doi.org/10.13140/RG.2.1.4658.7043. Ebeling, J.M., Timmons, M.B., 2012. Recirculating Aquaculture Systems. Aquaculture Production Systems. John Wiley & Sons, Ltd, pp. 245–277. https://doi.org/10.1002/ 9781118250105.ch11. EPA, 1988. Turbidity Water Quality Standards Criteria Summaries: A Compilation of
9
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al. Somerville, M., Jahanshahi, S., 2015. The effect of temperature and compression during pyrolysis on the density of charcoal made from Australian eucalypt wood. Renewable Energy 80, 471–478. https://doi.org/10.1016/j.renene.2015.02.013. Tociu, C., Diacu, E., Maria, C., 2014. Minimization of chemical risk by using recovered aluminium from metallurgical slag as coagulant in wastewater treatment. Environmental Engineering and Management Journal 13, 429–434. Torrens, A., Molle, P., Boutin, C., Salgot, M., 2009. Impact of design and operation variables on the performance of vertical-flow constructed wetlands and intermittent sand filters treating pond effluent. Water Research 43, 1851–1858. https://doi.org/ 10.1016/j.watres.2009.01.023. Turcios, A.E., Papenbrock, J., 2014. Sustainable treatment of aquaculture effluents-What can we learn from the past for the future? Sustainability (Switzerland) 6, 836–856. https://doi.org/10.3390/su6020836. Van Bussel, C.G.J., Schroeder, J.P., Wuertz, S., Schulz, C., 2012. The chronic effect of nitrate on production performance and health status of juvenile turbot (Psetta maxima). Aquaculture 326–329, 163–167. https://doi.org/10.1016/j.aquaculture. 2011.11.019. Van Rijn, J., 2013. Waste treatment in recirculating aquaculture systems. Aquacultural Engineering 53, 49–56. https://doi.org/10.1016/j.aquaeng.2012.11.010. Van Snick, B., Dhondt, J., Pandelaere, K., Bertels, J., Mertens, R., Klingeleers, D., Di Pretoro, G., Remon, J.P., Vervaet, C., De Beer, T., Vanhoorne, V., 2018. A
multivariate raw material property database to facilitate drug product development and enable in-silico design of pharmaceutical dry powder processes. International Journal of Pharmaceutics 549, 415–435. https://doi.org/10.1016/j.ijpharm.2018.08. 014. Wang, C.Y., Chang, C.Y., Chien, Y.H., Lai, H.T., 2016. The performance of coupling membrane filtration in recirculating aquaponic system for tilapia culture. International Biodeterioration and Biodegradation 107, 21–30. https://doi.org/10. 1016/j.ibiod.2015.10.016. Williams, G.J., Sheikh, B., Holden, R.B., Kouretas, T.J., Nelson, K.L., 2007. The impact of increased loading rate on granular media, rapid depth filtration of wastewater. Water Research 41, 4535–4545. https://doi.org/10.1016/j.watres.2007.06.018. Zamani, A., Maini, B., 2009. Journal of Petroleum Science and Engineering Flow of dispersed particles through porous media — Deep bed fi ltration 69, 71–88. https://doi. org/10.1016/j.petrol.2009.06.016. Zheng, R.L., Cai, C., Liang, J.H., Huang, Q., Chen, Z., Huang, Y.Z., Arp, H.P.H., Sun, G.X., 2012. The effects of biochars from rice residue on the formation of iron plaque and the accumulation of Cd, Zn, Pb, As in rice (Oryza sativa L.) seedlings. Chemosphere 89, 856–862. https://doi.org/10.1016/j.chemosphere.2012.05.008. Zouboulis, A., Traskas, G., Samaras, P., 2007. Comparison of single and dual media filtration in a full-scale drinking water treatment plant. Desalination 213, 334–342. https://doi.org/10.1016/j.desal.2006.02.102.
10
Contents lists available at ScienceDirect
Agricultural Water Management journal homepage: www.elsevier.com/locate/agwat
Integration of Biochar Filtration into Aquaponics: Effects on Particle Size Distribution and Turbidity Removal Zied Khiaria,*, Kumari Alkaa, Stephen Kellowayb, Beth Masonb, Nick Savidova a
Centre for Applied Research, Innovation and Entrepreneurship (CARIE) – Aquaculture Centre of Excellence (ACE). Lethbridge College. 3000 College Drive South, Lethbridge, Alberta, T1K 1L6, Canada b Verschuren Centre for Sustainability in Energy and the Environment. Cape Breton University. 1250 Grand Lake Road, Sydney, Nova Scotia, B1P 6L2, Canada
ARTICLE INFO
ABSTRACT
Keywords: aquaponics biochar filtration particle size distribution turbidity.
Small- and large-scale biochar-based filtrations were conducted to investigate the potential of biochar as a lowcost renewable filtration medium in aquaponics. The small-scale experimental design investigated the effects of 2 biochar media sizes (1 – 3 mm [referred to as fine biochar] and 3 – 5 mm [referred to as coarse biochar]), 3 biochar bed heights (2.5, 5.0 and 10.0 cm) and 3 loading rates (5, 10 and 15 m3/m2/d) on particle size distribution as well as turbidity removal efficiency. Both biochar sizes (fine and coarse) were able to clarify fish effluent. However, fine biochar led to better filtration characteristics compared to coarse biochar. Results indicated that biochar filter bed heights and loading rates affected the filtration performances. Using deeper filters combined with lower loading rates led to greater removal of suspended particles and turbidity compared to shallower filters and/or higher loading rates. Results from the large-scale filtration, using a mixture of fine and coarse biochar media (size of 1 – 5 mm), revealed that the ideal loading rate for maximizing the removal of turbidity from fish effluent in high-intensity aquaponic system for production of Nile tilapia and greenhouse plants (with 80 m3 total volume of water, 40 kg/m3 average stocking density and 15 kg/d feeding rate) was 10 m3/m2/d. This study suggests that biochar-based filtration could be incorporated into aquaponics as a polishing step before sending the water to plant growth systems.
1. Introduction The aquaculture industry is one of the fastest growing food-producing sectors in the world. According to the most recent estimates by the Food and Agriculture Organization of the United Nations (FAO), the global aquaculture production (both marine and inland) reached 80 million tons in 2016 (FAO, 2018) which accounted for 50% of the total seafood supply (Abate et al., 2016). Despite its considerable positive economic impacts, fish farming is associated with several environmental challenges such as significant water consumption and discharge of biologically unstable solid waste and nutrient-rich effluent (Turcios and Papenbrock, 2014; Wang et al., 2016). In order to alleviate these issues, more environmentally-friendly and sustainable fish farming technologies have been proposed, including recirculating aquaculture systems (RAS) and aquaponics (Ebeling and Timmons, 2012; Khiari et al., 2019; Savidov et al., 2007). Recirculating aquaculture systems (RAS) represent a technology for intensive fish farming where the water is recirculated to the fish culture tanks after mechanical and biological treatments (Badiola et al., 2012;
⁎
Van Rijn, 2013). RAS are capable of recycling more than 90% of the water (Badiola et al., 2012), which leads to reduction in both water consumption and effluent discharge. Biological filtration, though mandatory, is not sufficient on its own to guarantee adequate water quality for fish farming and therefore, other treatment processes (such as ozonation) are often required to remove organic carbon and turbidity (Gonçalves and Gagnon, 2011). Aquaponics, on the other hand, is a technology based on the co-production of fish and plants in one integrated system (Khiari et al., 2019; Savidov et al., 2007). In aquaponics, fish provide the required nutrients for plant growth, and in turn, plants absorb these nutrients decreasing their concentrations in the water, which is subsequently recycled back to the fish tanks (Medina et al., 2016). Biologically, aquaponics is an integrated multi-trophic system, which mimics the same interactions as those in natural ecosystems (Nichols and Savidov, 2012). Nitrification is just one of the processes in such ecosystems, where aerobic microorganisms convert ammonia (a toxic metabolite for fish) into nitrite and ultimately nitrate, which is considered the preferred form of nitrogen for plant growth (Khiari et al., 2019). The most significant benefits of aquaponics
Corresponding author. E-mail address: [email protected] (Z. Khiari).
https://doi.org/10.1016/j.agwat.2019.105874 Received 13 August 2019; Received in revised form 15 October 2019; Accepted 16 October 2019 0378-3774/ © 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Zied Khiari, et al., Agricultural Water Management, https://doi.org/10.1016/j.agwat.2019.105874
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
compared to RAS include increased revenue through the production of marketable vegetable crops (Savidov et al., 2007) as well as the reduced release of plant nutrients into the environment (since RAS require about 5 – 10% daily effluent discharge and fresh water renewal to lower the concentration of nitrate and other soluble minerals, which would otherwise accumulate in recirculated fish effluent (Van Bussel et al., 2012)). In this regard, several research studies indicated that plantbased removal of nutrients from fish effluent, through aquaponics, leads to more than 60% reduction in nitrate concertation and over 80% decrease in phosphorus level (Adler et al., 2003; Adler et al., 2000a; Adler et al., 2000b). The introduction of RAS and aquaponics into aquaculture practices resulted in significant advantages to the aquaculture industry and the environment. However, in order to achieve maximum RAS and aquaponics performance, a careful system design, a strict water quality control program and an optimum waste management strategy are required (Van Rijn, 2013; Wang et al., 2016). In both systems, ammonia removal and solids capture are the most critical treatment processes. In current industrial operations, ammonia removal is achieved through aerobic biological conversion to nitrate, while solids are separated from the water through mechanical filtration (such as drum and screen filters, floating bed filters and submerged high-pressure sand filters). The presence of organic solids can be extremely problematic for aquaponics. For instance, the biological decay of unconsumed feed and fecal matter lowers the oxygen level and generates toxic metabolites (Rakocy, 1994). In addition, the accumulation of organic debris in soilless crop production (such as aquaponic rafts and vertical towers) can plug the pipes and hinder drainage (Somerville et al., 2014). The problem of particle accumulation can be even more damaging on the root zone of the plants, as clogging the roots deprives them of adequate oxygen supply due to anaerobic decomposition of trapped debris (Rakocy et al., 2006, 2011; Rakocy, 1994). This, in turn, leads to severe plant stress and less resistance to root-borne diseases (such as Pithum) causing the ultimate failure of the plant production system. Although large-sized particles in fish effluent (≥ 30 μm) can be removed using conventional filtration methods, the challenge lies in the removal of smaller suspended micro- and nano-particles (Wang et al., 2016). Typically, particles below 30 μm are chemically removed through coagulation and/or flocculation (Tociu et al., 2014). Ozonation can also remove small particles. However, ozone application leads to the removal of dissolved organic compounds (Gonçalves and Gagnon, 2011) and thus deprives plants from important nutrients present in fish effluent. So far, there is no available technology, which can efficiently remove suspended particles from aquaculture effluents while retaining valuable plant nutrients. Biochar, also termed charcoal or biomass-derived black carbon, is a carbonaceous material produced from organic feedstock through pyrolysis (Meyer et al., 2011). The pyrolysis process leads to formation of a highly stable material with a complex network of interspersed tunnels with various pore sizes. Biochar porosity has been recognized as a desirable characteristic for numerous industrial applications. However, there was no in-depth study on biochar application for the removal of micro-particles and as a soilless growing medium until early 2000s when research investigations carried out by Savidov and Nichols (2010), Nichols et al. (2010) and Khan et al. (2015) indicated that biochar was not just a viable alternative to existing growing materials, but also exceeded them in terms of durability and crop yields. In addition to its role as a soilless growing medium, biochar can also function as a micro-filter when used in grow bags in aquaponics and organic hydroponics (Savidov, 2013). Another study also demonstrated the value of biochar in integrated fish and plant systems (Legault and Savidov, 2015). The following work is a continuation of unpublished work conducted at the Aquaculture Centre of Excellence (Lethbridge College) demonstrating and defining the microfiltration properties of biochar. The aims of this work were to (1) investigate biochar as a potential
low-cost renewable filtration medium in aquaponics, (2) optimize the biochar-based filtration process in a small-scale experimental set-up and (3) verify the outcomes in a large-scale biochar filter, incorporated within a high-intensity industrial aquaponic system. 2. Material and Methods 2.1. Materials 2.1.1. Fish effluent Fish effluent was obtained from a high-intensity aquaponic system of Nile tilapia (Oreochromis niloticus). In this system, fish effluent was first filtered through a drum filter (P.R.A. Manufacturing Ltd., Nanaimo, BC, Canada), which separated the liquid fraction (i.e. fish effluent rich in ammonia) from solid particulates (i.e. manure comprising unconsumed feed and fecal matter). Ammonia-rich fish effluent underwent a nitrification step within the fluidized-sand biofilter (biological filtration through aerobic nitrifying bacteria, mainly Nitrosomonas and Nitrobacter). This step initially converted ammonia into nitrite and subsequently into nitrate. Plants, in the greenhouse, absorbed nitrate and other soluble minerals reducing their concentrations in water, which was circulated back to the fish tank after oxygenation. The total volume of the water in this system was about 80 m3 and the average stocking density (weight of fish per unit volume of water) was approximately 40 kg/m3. The feeding rate of the fish was 15 kg/d with a fish feed (tilapia float 3.5 mm) comprising 40% crude protein, 9% crude fat and 10% ash (Skretting, Vancouver, BC, Canada). For the small- and large-scale filtration experiments, the water was collected after passing through the fluidized-sand biofilter and before delivery to the greenhouse. 2.1.2. Biochar Bamboo biochars, referred to as fine (with a particle size of 1 – 3 mm) and coarse (with a particle size of 3 – 5 mm), were separately used as filtration media. Biochar samples were prepared from the same bamboo feedstock and were divided after pyrolysis into different sizes (fine and coarse) using an industrial sieving machine. The biochars, used in this study, were prepared by Sungro Bioresource & Bioenergy Technologies Corp. (Edmonton, AB, Canada) and supplied by Pure Life Global Inc. (Calgary, AB, Canada). 2.2. Methods 2.2.1. Pretreatment Biochar samples (fine and coarse) were initially rinsed under cold tap water to remove dust and lower the pH of biochar to neutrality and then air-dried at 25 °C. 2.2.2. Biochar characterization 2.2.2.1. Density and total porosity. Bulk density was measured according to EBC guidelines (EBC, 2016). True density was determined at the Green Catalysis Research Group at University of Calgary (Calgary, AB, Canada) using an AccuPyc II 1340 pycnometer with helium as the displacement medium. Total porosity was calculated according to the following equation (Somerville and Jahanshahi, 2015):
Total Porosity (%) = 100 × 1
Bulk density True density
(1)
2.2.2.2. Scanning electron microscopy (SEM). The surface morphology of biochar was examined with a compact scanning electron microscope (Pemtron PS-230, Seoul, Korea). Biochar samples were first fixed using a double-sided carbon adhesive tape on an aluminum stub then gold coated by sputter coater and viewed at an acceleration voltage of 10.0 kV (Ghaffar et al., 2015). The scanning electron microscopy (SEM) 2
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
analysis was carried out at the Verschuren Centre for Sustainability in Energy and the Environment at Cape Breton University (Sydney, NS, Canada).
Table 1 Experimental design for small-scale biochar-based filtration.
2.2.3. Biochar-based filtration of fish effluent in aquaponics 2.2.3.1. Filter set-up. For the small-scale experiments, 3 biochar filters with various bed heights (2.5, 5.0 and 10.0 cm) were prepared for both fine and coarse biochars. Each filter was constructed using a polyvinyl chloride (PVC) pipe cap, with an internal diameter of 16.0 cm. An opening (with a diameter of 2.0 cm) was drilled in the center of PVC pipe cap, which served as the filter outlet port (Figure S1 A, Supplementary material). The internal surface of the filter was covered with a commercial landscaping polypropylene fabric in order to prevent the biochar from escaping. The large-scale biochar filter consisted of a cylindrical, fiberglass tank with a diameter of 2.4 m. An opening on the bottom center of the tank (with a diameter of 7.6 cm) was used as the outlet port (Figure S1 B, Supplementary material). The internal surface of the tank was covered with the same commercial landscaping polypropylene fabric that was used for the small-scale filters. The tank was filled with equal amounts of fine and coarse biochars (ratio 50:50, resulting in a biochar mixture with a size of 1 – 5 mm) to a height of 1.0 m based on literature for sand filters, which suggested an effective filtration media size of 2 – 4 mm and a recommended filter depth of 1 – 2 m (Zouboulis et al., 2007).
Flow rate ×(radius of the filter) 2
Filter bed height (cm)
Loading rate (m3/m2/d)
Filter bed height
Loading rate
1 2 3 4 5 6 7 8 9
2.5 2.5 2.5 5.0 5.0 5.0 10.0 10.0 10.0
5 10 15 5 10 15 5 10 15
−1 −1 −1 0 0 0 +1 +1 +1
−1 0 +1 −1 0 +1 −1 0 +1
(-1) denotes low level, (0) denotes medium level and (+1) denotes high level.
Relative span factor (RSF) =
(Dv90 Dv10) Dv50
(3)
A smaller RSF value indicates a narrower and more uniform particle size distribution (Phat et al., 2015). 2.2.4.2. Turbidity. Turbidity was measured using Smart Spectro spectrophotometer (LaMotte, Chestertown, MD, USA). Results, expressed as Formazin Turbidity Unit (FTU), were converted into turbidity removal percentage as follows:
Turbidity removal (%) = 100 (Turbidity before filtration Turbidity after filtration) × Turbidity before filtration
2.2.3.2. Filtration conditions. Before performing the filtration experiments, 10 L of deionized water was loaded onto each smallscale filter, while the large-scale filter was sprinkled with tap water. This pre-treatment operation was carried out to moisten and pack the biochar media as well as to flush out any residual dust and impurities. Fish effluent samples obtained after undergoing a biological treatment in the fluidized-sand biofilter, were used in this study. For both smalland large-scale biochar filtrations, 3 different loading rates (5, 10 and 15 m3/m2/d) were assessed. The loading rate was calculated as the flow rate divided by the surface area of the filter (m2) as follows:
Loading rate (m3/ m2 /d) =
Run
(4) 2.2.5. Statistics In the small-scale filtration experiments, three-level (low, medium and high), two-factor (biochar bed height and loading rate) factorial design of nine runs was performed for each biochar size (fine and coarse). The experimental design comprised all possible combinations of values for each factor (Table 1). The filtration experiments (both small-scale and large-scale) were replicated three times on three different occasions (3 independent trials). New biochar filters were prepared for each replicate during small-scale filtrations while for largescale filtrations, the biochar bed was turned over before each trial. Each analysis was performed in triplicate for each trial. Analysis of variance (ANOVA) was used and multiple range test Tukey’s honestly significant difference (P < 0.05) was conducted to determine differences between means. In small-scale experiments, the model tested the filtration conditions (biochar size, biochar bed height and loading rate) as fixed effects. In large-scale experiments, the model tested the loading rate as a fixed effect. For both scales (small and large), the filtration day (filtration replicate) was considered as a random effect. All statistical analyses were performed using Statistical Analysis Software (SAS University Edition, SAS Institute Inc., Cary, NC) and letter groupings were obtained using the SAS PDMIX800 macro (Saxton, 1998).
(2)
A series of valves were used to control the filtration at the desired loading rate. Adjustable micro sprayers (for small-scale filters) and mini spray nozzle sprinklers (for the large-scale filter) were used to uniformly apply the fish effluent on the top surface of the filters. Fish effluent was allowed to pass through the filters then samples were collected in 50 mL plastic tubes and analyzed within 2 hours after collection. 2.2.4. Characterization of biochar-based filtration 2.2.4.1. Particle size distribution. Particle size distribution was obtained using a Multi-Wavelength Laser Diffraction Particle Size Analyzer (LS 13 320, Beckman Coulter, Inc., Brea, CA, USA) fitted with a micro liquid module (with a 12 mL working volume). Data of the particles size distribution, with size ranging from 0.375 to 2000 μm, were obtained by Beckman Coulter Particle Characterization Software (version 6.01). Several particle size data were reported in this study including, the volume-weighted mean diameter (De Broukere mean, D[4,3], which denotes the weighted average volume diameter assuming spherical particles of the same volume as the real particles (Byrn et al., 2017)) as well as Dv10, Dv50 (volume median diameter) and Dv90 which respectively represent the size below which 10, 50 and 90% of the sample volume exists. In order to describe the particle size distribution, the relative span factor (RSF), which is a dimensionless parameter reflecting the uniformity of the particle size distribution (Čižauskaitė et al., 2017), was calculated as follows (Van Snick et al., 2018):
3. Results and Discussion 3.1. Biochar characterization 3.1.1. Physical properties of bamboo biochars The density and porosity of fine and coarse bamboo biochars are summarized in Table 2. The bulk density is an important characteristic that is indicative of the presence of pores and reflects the ability of biochar to sink or float in water given the pores are air-filled (Brewer et al., 2014). The bulk density of fine biochar (0.366 g/cm3) was two times greater than that of coarse biochar (0.176 g/cm3), which was mainly due to differences in size and shape. In fact, as the size of particles increases, the bulk density decreases (Bitra et al., 2009). True 3
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
density, in which the volume of intra-particle pores and voids between particles are excluded (Hung et al., 2017), indicated that the 2 sizes of bamboo biochar were fairly similar. This was expected because both biochar samples were prepared from the same feedstock at the same pyrolysis conditions. When comparing porosity, coarse biochar had greater total porosity (89.1%) than fine biochar (76.2%). Since both biochar samples had similar true density, the lower total porosity in fine biochar could be attributed to less voids between particles (inter-pores) compared to coarse biochar.
Table 2 Density and total porosity of fine and coarse bamboo biochars. Physical Characteristics
Fine Biochar
Coarse Biochar
Bulk density (g/cm3) True density (g/cm3) Total porosity (%)
0.366 1.541 76.25
0.176 1.613 89.09
3.1.2. Scanning electron microscopy (SEM) Fig. 1 shows typical SEM micrographs of the external morphology of a randomly selected bamboo biochar sample at 3 different magnification levels. SEM images revealed the porous structure of bamboo biochar with relatively uniform pores, in micrometer range, forming a honeycomb-like morphology and reflecting a typical structure of xylem tissue. In general, the pyrolysis process leads to the release of volatile components in the feedstock and the non-volatile matter is converted into porous biochar with voids of various shapes and sizes (Liew et al., 2018). The SEM analysis was in agreement with the porosity result, which indicated that bamboo biochar was mainly composed of a porous structure, with the majority of pores between 30 and 60 microns. Both intra-pores and inter-pores of bamboo biochar could play a major role in filtration of fish effluent in aquaponics. In this respect, the removal of particulate matter and turbidity could be achieved by either trapping the particles within the intra-pores of biochar, wedging them between convex surfaces of two biochar grains (i.e. retention in crevice sites), holding them in a sheltered areas developed by several biochar grains (i.e. retention in cavern sites), or a combination of these processes (Benamar et al., 2007; Herzig et al., 1970; Zamani and Maini, 2009). It is important to note that several factors, such as, shape, size and density of the particles, the grain size and porosity of biochar, the chemical properties and flow rate of the effluent, as well as the interaction forces between the particles and biochar media significantly affect the retention of particles and therefore, significantly affect the overall filtration through porous media, such as biochar (Gao, 2007; Herzig et al., 1970; Sabiri et al., 2017). 3.2. Small-scale biochar-based filtration of fish effluent in aquaponics 3.2.1. Particle size distribution Fig. 2 shows the particle size distribution curves of fish effluent before and after small-scale biochar filtration while Table 3 presents the particle size data of fish effluent after small-scale biochar filtration using fine and coarse biochars. For all loading rates and all biochar bed heights, it was clear that the particle size distribution of the inflow water (before filtration) was significantly greater than the outflow water (after filtration) (Fig. 2). For all loading rates tested in this study, the inflow water had a broad fraction of larger-size particles with D [4,3] varying from 71.0 to 75.3 μm, Dv10 ranging from 14.1 to 14.5 μm, Dv50 varying from 47.8 to 51.9 μm, Dv90 ranging from 165.4 to 172.1 μm and RSF extending from 3.0 to 3.2. After biochar filtration, the particle size distribution of outflow significantly decreased (P < 0.05) compared to the inflow at all loading rates (5, 10, and 15 m3/m2/d) and for all biochar bed heights (2.5, 5.0 and 10.0 cm). The size of biochar (fine and coarse), the loading rate, the biochar bed height as well as their interactions had statistically significant effects on the particle size distribution of the outflow (Table 3). When considering the sole effect of biochar size (fine and coarse), the results indicated that biochar size impacted the particle distribution characteristics of the outflow. Using fine biochar resulted in outflow with significantly lower D[4,3], Dv10, Dv50, Dv90 and RSF compared to coarse biochar (Table 3). The better particle size characteristics of the outflow obtained with fine biochar could be attributed to the porosity of fine biochar (as discussed in section 3.1.1), where the smaller inter-pore size between fine biochar grains could have retained more particles
Fig. 1. Scanning electron microscopy images of bamboo biochar. Figure A shows a micrograph at a low magnification level (×237); Figure B shows a micrograph at a medium magnification level (×411); and Figure C shows a micrograph at a high magnification level (×1,600).
4
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
Fig. 2. Particle size distribution curves for small-scale biochar-based filtration. Figure A: filtration using fine biochar at a loading rate of 5 m3/m2/d; Figure B: filtration using coarse biochar at a loading rate of 5 m3/m2/d; Figure C: filtration using fine biochar at a loading rate of 10 m3/m2/d; Figure D: filtration using coarse biochar at a loading rate of 10 m3/m2/d; Figure E: filtration using fine biochar at a loading rate of 15 m3/m2/d; Figure F: filtration using coarse biochar at a loading rate of 15 m3/m2/d. LR 5: loading rate of 5 m3/m2/d; LR 10: loading rate of 10 m3/m2/d; LR 15: loading rate of 15 m3/m2/d.
suspended in fish effluent. In addition, the surface area of fine biochar may also have played a role in improving particle capture efficiency. In this regard, fine biochar is believed to possess greater surface area
compared to coarse biochar as size reduction increases surface area (Peterson et al., 2012) which may have resulted in greater adsorption of particles (Zheng et al., 2012). 5
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
Table 3 Particle size characteristics for small-scale biochar-based filtration. Biochar Size Outflow
P-value
Fine Fine Fine Fine Fine Fine Fine Fine Fine Coarse Coarse Coarse Coarse Coarse Coarse Coarse Coarse Coarse Effect of Effect of Effect of Effect of Effect of Effect of Effect of
Bed Height (cm)
Loading Rate (m3/m2/d)
2.5 5 5.0 5 10.0 5 2.5 10 5.0 10 10.0 10 2.5 15 5.0 15 10.0 15 2.5 5 5.0 5 10.0 5 2.5 10 5.0 10 10.0 10 2.5 15 5.0 15 10.0 15 biochar size bed height biochar size × bed height loading rate biochar size × loading rate bed height × loading rate biochar size × bed height × loading rate
D[4,3] μm
Dv10 μm
Dv50 μm
Dv90 μm
RSF
20.40 ± 0.54d 19.20 ± 0.08d 18.83 ± 0.32d 20.73 ± 1.13d 19.68 ± 0.40d 19.62 ± 0.14d 21.01 ± 1.14d 19.34 ± 0.40d 18.95 ± 0.30d 19.45 ± 0.28d 19.16 ± 0.08d 19.03 ± 0.27d 30.55 ± 2.47b 26.74 ± 1.94c 26.15 ± 2.49c 38.95 ± 4.05a 29.81 ± 4.11b 28.34 ± 1.75bc < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001
8.90 ± 0.26abcd 8.04 ± 0.09efg 7.67 ± 0.28fg 8.14 ± 0.60defg 7.94 ± 0.40efg 8.55 ± 0.09abcde 8.51 ± 0.34bcde 8.34 ± 0.21def 7.46 ± 0.12g 8.00 ± 0.24efg 8.37 ± 0.08cdef 8.70 ± 0.21abcde 9.36 ± 0.37a 9.35 ± 0.13ab 9.19 ± 0.16abc 9.33 ± 0.53ab 7.59 ± 1.48fg 5.70 ± 1.05h 0.0058 < 0.0001 0.0638 < 0.0001 < 0.0001 < 0.0001 < 0.0001
20.37 ± 0.42abc 19.04 ± 0.04cde 18.75 ± 0.14cde 19.26 ± 0.58bcde 19.01 ± 0.27cde 19.16 ± 0.07bcde 18.35 ± 3.10e 19.03 ± 0.12cde 18.71 ± 0.07de 19.15 ± 0.15bcde 18.84 ± 0.06cde 18.92 ± 0.12cde 21.00 ± 0.76a 20.71 ± 0.41ab 20.21 ± 0.26abcd 20.98 ± 2.28a 19.63 ± 0.82abcde 18.93 ± 0.26cde < 0.0001 0.0006 0.3238 0.0004 < 0.0001 0.6385 0.0012
31.09 ± 0.85d 29.41 ± 0.15d 28.75 ± 0.63d 32.35 ± 1.69d 30.24 ± 0.53d 30.10 ± 0.31d 32.34 ± 1.74d 29.76 ± 0.60d 29.05 ± 0.52d 29.94 ± 0.28d 29.37 ± 0.22d 28.98 ± 0.41d 74.64 ± 9.07b 48.91 ± 12.20c 45.75 ± 12.42c 109.58 ± 12.05a 74.37 ± 21.98b 72.09 ± 8.40b < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001
1.09 ± 0.02e 1.12 ± 0.01e 1.12 ± 0.01e 1.26 ± 0.05de 1.17 ± 0.03de 1.12 ± 0.02e 1.36 ± 0.42cde 1.13 ± 0.03e 1.15 ± 0.02e 1.15 ± 0.01e 1.11 ± 0.01e 1.07 ± 0.01e 3.10 ± 0.36b 1.90 ± 0.55c 1.80 ± 0.59cd 4.84 ± 0.86a 3.37 ± 0.93b 3.51 ± 0.44b < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 < 0.0001 0.0055
Values are given as mean ± standard deviation. a-h Means within the same column sharing a common letter are not significantly different from each other.
Increasing the loading rate decreased Dv10 and increased D[4,3], Dv50, Dv90 and RSF of the outflow (Table 3). The effect of increasing the loading rate on filtration performances was more profound for coarse biochar compared to fine biochar (Fig. 2 and Table 3). This phenomenon (i.e. decrease of filtration performance at higher loading rates) was previously reported for the filtration of wastewater (DuranRos et al., 2009; Williams et al., 2007) and was attributed to reduction of transport time due to higher velocities, as well as to the decline of particle attachment efficiency as a result of hydrodynamic forces (Williams et al., 2007). In addition, high loading rates can result in the dissociation of attached particles and the breakage of large particles because of shear forces (Boller and Blaser, 1998; Kim and Lawler, 2012) which consequently may have affected the particle size distribution, as depicted in Fig. 2 and Table 3. Unlike the loading rate, increasing the height of biochar bed from 2.5 cm to 5.0 cm decreased the range of particle size distribution (Fig. 2) as well as the particle size data (Table 3). Similar trends (i.e. enhancement of filtration performance with higher filter bed) have been observed for the removal of particulate matter and contaminants using activated carbon (Areerachakul et al., 2007), pumice, a porous volcanic rock (Farizoglu et al., 2003) and sand (Torrens et al., 2009). Subsequent increase of biochar filter bed height from 5.0 cm to 10.0 cm did not result in improvement of fish effluent filtration. The enhanced removal of larger particles with deeper biochar bed could be due to a greater detention time as well as higher surface area for the retention of particles (Farizoglu et al., 2003).
measurement (turbidity values and turbidity removal percentages) of outflow after biochar filtration are presented in Table 4. The turbidity values ranged from 15.22 to 31.11 FTU while the turbidity removal efficiencies varied from 60.47% to 80.66% depending on biochar size, loading rate, and biochar bed height. When comparing the effect of 2 biochar sizes, it was found that using fine biochar led to lower turbidity values and better turbidity removal percentages compared to coarse biochar. This could be attributed to the lower total porosity and the greater surface properties of fine biochar which may have resulted in better capture of particles. In fact, particle removal during filtration occurs through the transport of particulate matter and suspended solids from the inflow into the filtration media followed by their capture by either adsorption (due to Brownian motion and electrostatic interactions between the particles and the surface of the pores), size exclusion/ straining (due to size difference between the particles and the pore openings) and/or sedimentation/gravity settling (due to density difference between the particles and the carrying effluent) (Gao, 2007). Results also indicated that increasing the loading rate and/or decreasing the biochar bed height negatively impacted the turbidity removal efficiency. For filtration using fine biochar, the lowest turbidity value and the greatest turbidity removal percentage (15.22 FTU and 80.66%, respectively) were obtained at the lowest loading rate (5 m3/ m2/d) and the highest bed height (10.0 cm) (Table 4) while the lowest turbidity values (24.22 – 24.33 FTU) and the greatest turbidity removal efficiencies (69.08 – 69.22%) for coarse biochar were observed at 5 m3/ m2/d using 5.0 and 10.0 cm biochar bed heights (Table 4). Increasing the loading rate and/or decreasing the bed height caused the opposite effect (Table 4). In this regards, the greatest turbidity values and the lowest turbidity removal efficiencies for fine and coarse biochars were observed at 10 and 15 m3/m2/d using 2.5 cm bed height. After filtration, all waters were visually clear with light yellowish–brownish color, which was most probably due to the presence of dissolved humic matter. The turbidity results strongly indicated that biochar possessed the capacity to retain particles and clarify aquaponic effluents.
3.2.2. Turbidity removal efficiency Turbidity reflects the presence of suspended and dissolved solids that absorb or scatter light. As a water quality parameter, turbidity has a great significance in aquaculture and aquaponics because high turbidity reduces dissolved oxygen (Henley et al., 2000) and consequently turbid environments lose their ability to maintain healthy plants and aquatic organisms (Bisinoti et al., 2007). The inflow in this study had a turbidity value of 77.44 ± 2.01 FTU. Results from the turbidity
6
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
3.3. Large-scale biochar-based filtration of fish effluent in aquaponics
Table 4 Turbidity values and turbidity removal percentages for small-scale biocharbased filtration. Biochar Size
Bed Height (cm)
Loading Rate (m3/m2/d)
Outflow Fine 2.5 5 Fine 5.0 5 Fine 10.0 5 Fine 2.5 10 Fine 5.0 10 Fine 10.0 10 Fine 2.5 15 Fine 5.0 15 Fine 10.0 15 Coarse 2.5 5 Coarse 5.0 5 Coarse 10.0 5 Coarse 2.5 10 Coarse 5.0 10 Coarse 10.0 10 Coarse 2.5 15 Coarse 5.0 15 Coarse 10.0 15 P-value Effect of biochar size Effect of bed height Effect of biochar size × bed height Effect of loading rate Effect of biochar size × loading rate Effect of bed height × loading rate Effect of biochar size × bed height × loading rate
Turbidity (FTU)
Turbidity Removal (%)
25.78 ± 0.83gh 18.22 ± 1.39i 15.22 ± 1.30j 31.11 ± 0.93a 26.00 ± 0.71fgh 26.89 ± 1.45efg 31.11 ± 1.90a 27.89 ± 2.41cdefg 29.11 ± 2.15abcd 26.78 ± 1.64efg 24.22 ± 1.72h 24.33 ± 0.71h 29.33 ± 0.71abc 27.11 ± 0.78defg 26.22 ± 1.48fgh 30.56 ± 1.01ab 28.89 ± 0.60bcde 28.11 ± 1.45cdef < 0.0001 < 0.0001 < 0.0001
67.25 ± 1.06cd 76.85 ± 1.77b 80.66 ± 1.65a 60.47 ± 1.18j 66.96 ± 0.90cde 65.83 ± 1.85def 60.47 ± 2.41j 64.56 ± 1.61defg 63.01 ± 2.73ghij 65.97 ± 2.09def 69.22 ± 2.18c 69.08 ± 0.90c 62.73 ± 0.90hij 65.55 ± 0.99defg 66.68 ± 1.88cde 61.17 ± 1.29ij 63.29 ± 0.76fghi 64.28 ± 1.85efgh < 0.0001 < 0.0001 < 0.0001
< 0.0001 < 0.0001
< 0.0001 < 0.0001
< 0.0001
< 0.0001
< 0.0001
< 0.0001
Fig. 3 and Table 5 show, respectively, the particle size distribution curves and particle size distribution data for fish effluent after filtration using the large-scale biochar filter at 3 loading rates (5, 10 and 15 m3/ m2/d). Particle size analysis of the inflow water for large-scale biochar filtration indicated that D[4,3] varied from 64.9 to 72.6 μm, Dv10 ranged from 13.4 to 14.2 μm, Dv50 varied from 38.0 to 46.6 μm, Dv90 ranged from 162.6 to 177.0 μm and RSF extended from 3.5 to 3.9. Similar to small-scale outcomes, large-scale biochar filtration resulted in significant reduction of particle size distributions of fish effluent (Fig. 3). For all loading rates, D[4,3] was reduced by more than 90%, Dv10 and Dv90 dropped by more than 94% while Dv50 decreased by more than 84%. Increasing the loading rate from 5 m3/m2/d to 10 m3/ m2/d and subsequently to 15 m3/m2/d broadened the particle distribution of the outflow (Fig. 3) and significantly increased the values of the mean, median and the two percentiles Dv10 and Dv90 as well as the RSF (Table 5). The loading rate, in the large-scale biochar-based filtration, also significantly affected the turbidity values and the turbidity removal efficiencies. In this respect, increasing the loading rate from 5 m3/m2/d to 15 m3/m2/d significantly increased the turbidity values from 12.89 to 16.89 FTU and lowered the turbidity removal efficiencies from 83.35% to 78.18% (Table 6). The turbidity value (13.78 FTU) and the turbidity removal efficiency (82.20%) at 10 m3/m2/d were slightly lower than that obtained using a loading rate of 5 m3/m2/d (Table 6), however, the differences were not statistically significant (P > 0.05). Regardless of the loading rate, the turbidity of the outflow from largescale biochar filter ranged from 12.89 ± 0.60 to 16.89 ± 0.78 FTU. These turbidity values indicated that biochar-filtered fish effluents were suitable for re-use in aquaculture as their turbidity fell within the acceptable range (5 - 25 NTU/FTU) for domestic use (Drever, 2002) and did not exceed the maximum allowable value of 25 NTU/FTU for aquaculture use (EPA, 1988). Outcomes from the large-scale filtration experiments indicated that using a biochar filter with a media size of 1 – 5 mm (a mixture of fine and coarse biochars) at a loading rate of 10 m3/m2/d were the ideal
Values are given as mean ± standard deviation. a-j Means within the same column sharing a common letter are not significantly different from each other.
Fig. 3. Particle size distribution curves for large-scale biochar-based filtration. LR 5: loading rate of 5 m3/m2/d; LR 10: loading rate of 10 m3/m2/d; LR 15: loading rate of 15 m3/m2/d.
7
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
Table 5 Particle size characteristics for large-scale biochar-based filtration.
Outflow P-value
Loading Rate (m3/m2/d)
D[4,3] μm
Dv10 μm
Dv50 μm
Dv90 μm
RSF
5 10 15 Effect of loading rate
4.95 ± 0.31c 5.74 ± 0.13b 6.01 ± 0.11a < 0.0001
0.66 ± 0.07c 0.82 ± 0.02b 0.91 ± 0.04a < 0.0001
5.97 ± 0.33b 6.48 ± 0.26a 6.37 ± 0.39a 0.0074
7.34 ± 0.55c 9.57 ± 0.49b 10.77 ± 0.50a < 0.0001
1.12 ± 0.07c 1.35 ± 0.11b 1.56 ± 0.18a < 0.0001
Values are given as mean ± standard deviation. a-c Means within the same column sharing a common letter are not significantly different from each other.
4. Conclusion
Table 6 Turbidity values and turbidity removal percentages for large-scale biocharbased filtration.
Outflow P-value
Loading Rate (m3/m2/d)
Turbidity (FTU)
Turbidity Removal (%)
5 10 15 Effect of loading rate
12.89 ± 0.60b 13.78 ± 0.97b 16.89 ± 0.78a < 0.0001
83.35 ± 0.78a 82.20 ± 1.26a 78.18 ± 1.01b < 0.0001
Based on the present study, biochar represents a promising potential low-cost renewable biomass for aquaponic effluent filtration. The porous structure of biochar makes it very suitable for the retention of suspended particles and removal of turbidity. The quality of filter outflow, in terms of particle and turbidity removal efficiencies clearly demonstrated that biochar-based filtration can be used in aquaponics to clarify fish effluent, most appropriately as a water polishing step (before sending the treated water plant growth systems) especially for fish species with higher demand for water quality, such as salmonids. Results also indicated that the performance of biochar-based filtration depends on the operational conditions (biochar media size, biochar filter bed height and loading rate). Despite these positive findings, further research is still required to fully confirm the advantages of biochar-based effluent filtration in highly-intensive aquaponic productions.
Values are given as mean ± standard deviation. a-b Means within the same column sharing a common letter are not significantly different from each other.
conditions for the removal of suspended particles and turbidity in highintensity fish farming/aquaponic operations. Biochar-based filtration, in such systems, could most suitably be incorporated as a polishing process before sending the water back to the plant growth systems (such as raft media bed and vertical tower) as shown in Fig. 4. It is important to note, however, that these recommendations are only applicable for aquaponic systems running under similar operational conditions, as fish species, feed composition, feeding rate, stocking density and water treatment processes can all affect total suspended solids and particulate density and nature.
5. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Fig. 4. Suggested placement of biochar filter in aquaponics for removal of particulate matter and turbidity.
8
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al.
Declaration of Competing Interest
State/Federal Criteria. United States Environmental Protection Agency, Office of Water Regulations and Standards, Washington, DC, pp. 1–20. FAO, 2018. The State of World Fisheries and Aquaculture 2018 - Meeting the sustainable development goals. Food and Agriculture Organization of the United Nations, Rome. Farizoglu, B., Nuhoglu, A., Yildiz, E., Keskinler, B., 2003. The performance of pumice as a filter bed material under rapid filtration conditions. Filtration & separation 40, 41–47. Gao, C., 2007. Factors affecting particle retention in porous media. Emirates Journal for Engineering Research 12, 1–7. Ghaffar, A., Ghosh, S., Li, F., Dong, X., Zhang, D., Wu, M., Li, H., Pan, B., 2015. Effect of biochar aging on surface characteristics and adsorption behavior of dialkyl phthalates. Environmental Pollution 206, 502–509. https://doi.org/10.1016/j.envpol. 2015.08.001. Gonçalves, A.A., Gagnon, G.A., 2011. Ozone Application in Recirculating Aquaculture System: An Overview. Ozone: Science & Engineering 33, 345–367. https://doi.org/ 10.1080/01919512.2011.604595. Henley, W.F., Patterson, M.A., Neves, R.J., Lemly, A.D., 2000. Effects of Sedimentation and Turbidity on Lotic Food Webs: A Concise Review for Natural Resource Managers. Reviews in Fisheries Science 8, 125–139. https://doi.org/10.1080/ 10641260091129198. Herzig, J.P., Leclerc, D.M., Goff, P. Le, 1970. Flow of Suspensions through Porous MedidApplicdtion to Deep Filtrdtion. Ind. Eng. Chem. 62, 8–35. Hung, C.Y., Tsai, W.T., Chen, J.W., Lin, Y.Q., Chang, Y.M., 2017. Characterization of biochar prepared from biogas digestate. Waste Management 66, 53–60. https://doi. org/10.1016/j.wasman.2017.04.034. Khan, A., Savidov, N., Zhang, J., Yang, J., Anderson, T., Harfield, D., Anyia, A.O., 2015. Biochar Substrate for Hydroponic Vegetable Production. In: Ok, Y.S., Uchimiya, S.M., Chang, S.X., Bolan, N. (Eds.), Biochar: Production, Characterization, and Applications. CRC Press, Taylor & Francis Group, Boca Raton, FL, pp. 274–291. Khiari, Z., Kaluthota, S., Savidov, N., 2019. Aerobic bioconversion of aquaculture solid waste into liquid fertilizer: Effects of bioprocess parameters on kinetics of nitrogen mineralization. Aquaculture 500, 492–499. https://doi.org/10.1016/j.aquaculture. 2018.10.059. Kim, J., Lawler, D.F., 2012. The influence of hydraulic loads on depth filtration. Water Research 46, 433–441. https://doi.org/10.1016/j.watres.2011.10.059. Legault, M., Savidov, N., 2015. Crop Production Platform Based On Aerobic Bio-Digestion Technology. Internal Report. Alberta Agriculture and Rural Development, BioIndustrial Opportunities Branch, Food and Bio-Processing Division. Liew, R.K., Nam, W.L., Chong, M.Y., Phang, X.Y., Su, M.H., Yek, P.N.Y., Ma, N.L., Cheng, C.K., Chong, C.T., Lam, S.S., 2018. Oil palm waste: an abundant and promising feedstock for microwave pyrolysis conversion into good quality biochar with potential multi-applications. Process Safety and Environmental Protection 115, 57–69. Medina, M., Jayachandran, K., Bhat, M.G., Deoraj, A., 2016. Assessing plant growth, water quality and economic effects from application of a plant-based aquafeed in a recirculating aquaponic system. Aquaculture international 24, 415–427. Meyer, S., Glaser, B., Quicker, P., 2011. Technical, Economical, and Climate-Related Aspects of Biochar Production Technologies: A Literature Review. Environmental Science & Technology 45, 9473–9483. https://doi.org/10.1021/es201792c. Nichols, M., Savidov, N., Aschim, K., 2010. Biochar as a Hydroponic Growing Medium. Practical Hydroponics and Greenhouses 112, 39–42. Nichols, M.A., Savidov, N.A., 2012. Aquaponics: a nutrient and water efficient production system. Acta Horticulturae. International Society for Horticultural Science (ISHS), Leuven, Belgium, pp. 129–132. https://doi.org/10.17660/ActaHortic.2012.947.14. Peterson, S.C., Jackson, M.A., Kim, S., Palmquist, D.E., 2012. Increasing biochar surface area: Optimization of ball milling parameters. Powder Technology 228, 115–120. https://doi.org/10.1016/j.powtec.2012.05.005. Phat, C., Li, H., Lee, D.U., Moon, B., Yoo, Y.B., Lee, C., 2015. Characterization of Hericium erinaceum powders prepared by conventional roll milling and jet milling. Journal of Food Engineering 145, 19–24. https://doi.org/10.1016/j.jfoodeng.2014.08.001. Rakocy, J., Masser, M.P., Losordo, T., 2006. Recirculating aquaculture tank production systems: Aquaponics – integrating fish and plant culture. Southern Regional Aquaculture Center (SRAC) Publication No. 454. Rakocy, J.E., 1994. Aquaponics: The integration of fish and vegetable culture in recirculating systems. In: Proceedings of the 30th Annual Meeting. Caribbean Food Crops Society, Saint Thomas. pp. 101–108. Rakocy, J.E., Bailey, D.S., Shultz, R.C., Danaher, J.J., et al., 2011. A commercial-scale aquaponic system developed at the University of the Virgin Islands. Proceedings of the 9th International Symposium on Tilapia in Aquaculture 336–343. Sabiri, N.E., Monnier, E., Raimbault, V., Massé, A., Séchet, V., Jaouen, P., 2017. Effect of filtration rate on coal-sand dual-media filter performances for microalgae removal. Environmental Technology (United Kingdom) 38, 345–352. https://doi.org/10. 1080/09593330.2016.1193224. Savidov, N., 2013. Supergrow (biochar) – greenhouse trials and commercial applications. Project #AB0512. ACIDF Official Report, Government of Alberta. Savidov, N., Nichols, M., 2010. Biochar – A New Hydroponic Growing Medium. 28th International Horticultural Congress 35. Savidov, N.A., Hutchings, E., Rakocy, J.E., 2007. Fish and plant production in a recirculating aquaponic system: a new approach to sustainable agriculture in Canada. Acta Horticulturae 742, 209–221. https://doi.org/10.17660/ActaHortic.2007. 742.28. Saxton, A.M., 1998. A macro for converting mean separation output to letter groupings. In: Proc Mixed. Proceedings of the 23rd SAS Users Group International. 22-25 Mar 1998, Nashville. pp. 1243–1246. Somerville, C., Cohen, M., Pantanella, E., Stankus, A., Lovatelli, A., 2014. Small-scale aquaponic food production: integrated fish and plant farming. FAO Fisheries and Aquaculture Technical Paper I.
None. Acknowledgements The Natural Sciences and Engineering Research Council of Canada (NSERC) and Alberta Innovates are gratefully acknowledged for providing funds under NSERC Engage and Campus Alberta Small Business Engagement (CASBE) Programs, respectively. Alberta Economic Development and Trade is acknowledged for financial support in purchasing the LS 13 320 Multi-Wavelength Laser Diffraction Particle Size Analyzer. The authors would like to thank John Derksen for reviewing the manuscript, Clay Boyes and Penny Takahashi for assistance in setting up biochar filters, Beckman Coulter Inc. for providing helpful technical support as well as Pure Life Global Inc. for in-kind contribution. Appendix A. Supplementary data Supplementary material related to this article can be found, in the online version, at doi:https://doi.org/10.1016/j.agwat.2019.105874. References Abate, T.G., Nielsen, R., Tveterås, R., 2016. Stringency of environmental regulation and aquaculture growth: A cross-country analysis. Aquaculture Economics & Management 20, 201–221. https://doi.org/10.1080/13657305.2016.1156191. Adler, P.R., Harper, J.K., Takeda, F., Wade, E.M., Summerfelt, S.T., 2000a. Economic evaluation of hydroponics and other treatment options for phosphorus removal in aquaculture effluent. HortScience 35, 993–999. Adler, P.R., Harper, J.K., Wade, E.M., Takeda, F., Summerfelt, S.T., 2000b. Economic Analysis of an Aquaponic System for the Integrated Production of Rainbow Trout and Plants. International Journal of Recirculating Aquaculture 1, 15–34. https://doi.org/ 10.21061/ijra.v1i1.1359. Adler, P.R., Summerfelt, S.T., Glenn, D.M., Takeda, F., 2003. Mechanistic approach to phytoremediation of water. Ecological Engineering 20, 251–264. https://doi.org/10. 1016/S0925-8574(03)00044-2. Areerachakul, N., Vigneswaran, S., Ngo, H.H., Kandasamy, J., 2007. Granular activated carbon (GAC) adsorption-photocatalysis hybrid system in the removal of herbicide from water. Separation and Purification Technology 55, 206–211. https://doi.org/ 10.1016/j.seppur.2006.12.007. Badiola, M., Mendiola, D., Bostock, J., 2012. Recirculating Aquaculture Systems (RAS) analysis: Main issues on management and future challenges. Aquacultural Engineering 51, 26–35. https://doi.org/10.1016/j.aquaeng.2012.07.004. Benamar, A., Ahfir, N.D., Wang, H.Q., Alem, A., 2007. Particle transport in a saturated porous medium: Pore structure effects. Comptes Rendus - Geoscience 339, 674–681. https://doi.org/10.1016/j.crte.2007.07.012. Bisinoti, M.C., Yabe, M.J.S., Gimenez, S.M.N., Simões, F., dos, S., Moreira, A.B., 2007. Water quality index as a simple indicator of aquaculture effects on aquatic bodies. Ecological Indicators 8, 476–484. https://doi.org/10.1016/j.ecolind.2007.05.002. Bitra, V.S.P., Womac, A.R., Miu, P.I., Chevanan, N., Sokhansanj, S., Yang, Y.T., Igathinathane, C., 2009. Bulk density and compaction behavior of knife mill chopped switchgrass, wheat straw, and corn stover. Bioresource Technology 101, 207–214. https://doi.org/10.1016/j.biortech.2009.07.083. Boller, M., Blaser, S., 1998. Particles under stress. Water Science and Technology 37, 9–29. Brewer, C.E., Chuang, V.J., Masiello, C.A., Gonnermann, H., Gao, X., Dugan, B., Driver, L.E., Panzacchi, P., Zygourakis, K., Davies, C.A., 2014. New approaches to measuring biochar density and porosity. Biomass and Bioenergy 66, 176–185. https://doi.org/ 10.1016/j.biombioe.2014.03.059. Byrn, S.R., Zografi, G., Chen, S., 2017. Solid state properties of pharmaceutical materials. Wiley Online Library. Čižauskaitė, U., Marksa, M., Bernatonienė, J., 2017. The optimization of technological processes, stability and microbiological evaluation of innovative natural ingredients based multiple emulsion. Pharmaceutical development and technology 2017, 1–10 vol. 00, iss. 00. Drever, J.I., 2002. The geochemistry of natural waters : Surface and groundwater environments LK, 3rd ed. Prentice Hall, Upper Saddle River, N.J. Duran-Ros, M., Puig-Bargués, J., Arbat, G., Barragán, J., Cartagena, F.R. de, 2009. Effect of filter, emitter and location on clogging when using effluents. Agricultural Water Management 96, 67–79. https://doi.org/10.1016/j.agwat.2008.06.005. EBC, 2016. Guidelines for a Sustainable Production of Biochar. European Biochar Foundation (EBC)https://doi.org/10.13140/RG.2.1.4658.7043. Ebeling, J.M., Timmons, M.B., 2012. Recirculating Aquaculture Systems. Aquaculture Production Systems. John Wiley & Sons, Ltd, pp. 245–277. https://doi.org/10.1002/ 9781118250105.ch11. EPA, 1988. Turbidity Water Quality Standards Criteria Summaries: A Compilation of
9
Agricultural Water Management xxx (xxxx) xxxx
Z. Khiari, et al. Somerville, M., Jahanshahi, S., 2015. The effect of temperature and compression during pyrolysis on the density of charcoal made from Australian eucalypt wood. Renewable Energy 80, 471–478. https://doi.org/10.1016/j.renene.2015.02.013. Tociu, C., Diacu, E., Maria, C., 2014. Minimization of chemical risk by using recovered aluminium from metallurgical slag as coagulant in wastewater treatment. Environmental Engineering and Management Journal 13, 429–434. Torrens, A., Molle, P., Boutin, C., Salgot, M., 2009. Impact of design and operation variables on the performance of vertical-flow constructed wetlands and intermittent sand filters treating pond effluent. Water Research 43, 1851–1858. https://doi.org/ 10.1016/j.watres.2009.01.023. Turcios, A.E., Papenbrock, J., 2014. Sustainable treatment of aquaculture effluents-What can we learn from the past for the future? Sustainability (Switzerland) 6, 836–856. https://doi.org/10.3390/su6020836. Van Bussel, C.G.J., Schroeder, J.P., Wuertz, S., Schulz, C., 2012. The chronic effect of nitrate on production performance and health status of juvenile turbot (Psetta maxima). Aquaculture 326–329, 163–167. https://doi.org/10.1016/j.aquaculture. 2011.11.019. Van Rijn, J., 2013. Waste treatment in recirculating aquaculture systems. Aquacultural Engineering 53, 49–56. https://doi.org/10.1016/j.aquaeng.2012.11.010. Van Snick, B., Dhondt, J., Pandelaere, K., Bertels, J., Mertens, R., Klingeleers, D., Di Pretoro, G., Remon, J.P., Vervaet, C., De Beer, T., Vanhoorne, V., 2018. A
multivariate raw material property database to facilitate drug product development and enable in-silico design of pharmaceutical dry powder processes. International Journal of Pharmaceutics 549, 415–435. https://doi.org/10.1016/j.ijpharm.2018.08. 014. Wang, C.Y., Chang, C.Y., Chien, Y.H., Lai, H.T., 2016. The performance of coupling membrane filtration in recirculating aquaponic system for tilapia culture. International Biodeterioration and Biodegradation 107, 21–30. https://doi.org/10. 1016/j.ibiod.2015.10.016. Williams, G.J., Sheikh, B., Holden, R.B., Kouretas, T.J., Nelson, K.L., 2007. The impact of increased loading rate on granular media, rapid depth filtration of wastewater. Water Research 41, 4535–4545. https://doi.org/10.1016/j.watres.2007.06.018. Zamani, A., Maini, B., 2009. Journal of Petroleum Science and Engineering Flow of dispersed particles through porous media — Deep bed fi ltration 69, 71–88. https://doi. org/10.1016/j.petrol.2009.06.016. Zheng, R.L., Cai, C., Liang, J.H., Huang, Q., Chen, Z., Huang, Y.Z., Arp, H.P.H., Sun, G.X., 2012. The effects of biochars from rice residue on the formation of iron plaque and the accumulation of Cd, Zn, Pb, As in rice (Oryza sativa L.) seedlings. Chemosphere 89, 856–862. https://doi.org/10.1016/j.chemosphere.2012.05.008. Zouboulis, A., Traskas, G., Samaras, P., 2007. Comparison of single and dual media filtration in a full-scale drinking water treatment plant. Desalination 213, 334–342. https://doi.org/10.1016/j.desal.2006.02.102.
10