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A Comparative Evaluation of Ceramic Membrane Bioreactors
8 A COMPARATIVE EVALUATION OF CERAMIC MEMBRANE BIOREACTORS Rahman Zeynali,1 Kamran Ghasemzadeh,1 Elham Jalilnejad,1 Angelo Basile2 1
Faculty of Chemical Engineering, Urmia University of Technology, Urmia, Iran; 2Institute on Membrane Technology, National Research Council, University of Calabria, Rende (CS), Italy
1. Introduction The growth of the world’s population and the tendency of reside in urban areas are the most important reasons for problems involving the availability of water resources, especially clean water. The fast rapid of growing of industries and urbanization produce wastewater in large amounts that includes contaminates such as: • organic toxic materials, • ammonium pollutant, • metals (heavy), and • complex and complicated composites. The discharge of untreated wastewater into the environment causes consequences for the underground water supply that lead to human health problems (Zhang et al., 2016; Jalilnejad and Vahabzadeh, 2014). According to statistical research, more than 85% of wastewater returns to the environment untreated. Many treatment methods are useful in this regard (Recepoglu et al., 2018): • physical methods, including separation and adsorption techniques; • chemical methods, including oxidation and coagulationflocculation techniques; and • biological methods including sequencing batch reactors and activated sludge. Current Trends and Future Developments on (Bio-) Membranes. https://doi.org/10.1016/B978-0-12-816822-6.00008-2 Copyright © 2020 Elsevier Inc. All rights reserved.
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The process for treating water depends on the intended use for the treated water; factors include the cost, energy consumption, and the space needed for a treatment plant. Among the various methods, membrane bioreactors (MBRs) are the most promising for industrial and municipal wastewater treatment (Fatimah et al., 2015; Lakard et al., 2015). Properties such as effective performance and a compact setup, which are important characters in membrane technology, have drawn the attention of researchers to MBR technology, especially for the wastewater treatment industry. MBR treatment has notable properties with respect to other methods, some of which are (Lakard et al., 2015; Liao et al., 2018): • highly efficient performance in nutrient elimination and a low energy requirement (0.6e2.3 kWh/m3) • less need for equipment • complete retention of biomass materials • good quality and enough effluent • high capacity of organic loadings in volume • less production of sludge The operation of MBRs can be divided into two main steps, membrane filtration with a physicochemical mechanism and activated sludge (mixed bacteria), to degrade organic contaminants and nutrient substances (such as phosphorus and nitrogen). The membrane system rejects most colloids and biomass particles that are part of solutes using microfiltration (MF) and ultrafiltration (UF), whereas in MBR, separation and biological treatment occur simultaneously and activated sludge causes particle waste to change into flock before the membrane separation unit (Liao et al., 2018; Krzeminski et al., 2017). The high cost of membranes and their maintenance have resulted in decreased interest in MBR systems and an increase in the cost of membranes. Because of technological improvements, MBR has become an economically feasible option for mediumscale systems with a population capacity about 10,000e100,000 or equivalent (Krzeminski et al., 2017; Castilho et al., 2009). Many MBR units are in use in different parts of the world. The first large-scale installation was in the United States in 1990 by General Motors Company, to treat industrial wastewater. After that, the first MBR using an internal membrane system was for the industrial food industry in 1998 in North America (Sutton, 2003). More than 200 MBR plants to treat wastewater have been installed all over the world (each plant’s capacity is more than 10,000 m3/d), with a total of more than 20 million m3/d (Zheng et al., 2013). More than 2200 MBR systems are under construction
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internationally, and it is predicted that the global market will grow by about 20%, most of which will be for wastewater treatment in municipal areas (Judd, 2016). The main goal of this chapter is to provide a broad introduction to MBRs, materials used in membranes, MBR configurations, parameters affecting their performance, and a cost assessment of ceramic MBRs. Applications of MBRs in wastewater treatment in industry and affluent cities, which covers membrane and biomass characteristics, are discussed. The limitation of MBRs and their mitigation behavior are also reviewed. Finally, in enable a good selection among MBRs based on the needs of treatment, an economic investigation into MBRs and their advantages and disadvantages are discussed.
2. Fundamentals of Membrane Bioreactors In this part of study, two important issues regarding MBRs will be discussed. The first part addresses the most common configurations of MBRs, and second part presents applications of MBRs such as biofuel production and wastewater treatment.
2.1 Configurations of Membrane Bioreactors There are some problems and challenges to using MBR on a large scale and these systems have not been thoroughly tested, so different configurations of MBRs have been introduced, including external, submerged, and airlift designs, as shown in Figs. 8.1e8.3.
Pressure gauge
Process control
O2/Air
Pressure gauge
Treated water Wastewater Pump Mixing + Aeration
Membrane unit
Figure 8.1 External model of membrane bioreactor scheme.
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Feed
Bio
Membrane module Permeate
Feed
Air
Figure 8.2 Airlift model of membrane bioreactor scheme.
Wastewater
Effluent/ Permeate Membrane Bioreactor
Figure 8.3 Submerged model of membrane bioreactor scheme.
The configuration of external MBRs is designed to overcome membrane fouling problems with direct control of hydrodynamic parameters. It has some advantages such as a high flux factor of production and easy replacement of the membrane, but an important disadvantage is the high energy consumption. The submerged design does not have this problem; it involves less rigorous cleaning and a lower operating cost (Le-Clech et al., 2006). Among these configurations, the airlift design optimizes energy consumption using the principle of the side stream with airlift. All three configurations are used in landfill leachate, municipal wastewater, and sewage wastewater treatment processes, but the airlift model has not been used much (Fan et al., 2006). The sludge activation method can occur in two different ways: suspended growth or medium immobilized growth; these are different from the distribution method (Radjenovic et al., 2007).
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According to the suspended growth system, microorganisms are able to move freely in liquid media and have the ability to recover after flock settles and to return to the system during the next treatment. During immobilized growth on natural substrates such as polyurethane, kissiris, zeolite, and carbon (activated), microorganisms survive as a biofilm shape on the substrates (Khan et al., 2011). Finally, according to studies, submerged MBR was inexpensive compared with other MBR systems (Santos et al., 2011).
2.2 Applications of Membrane Bioreactors This part of study discusses applications of MBRs for important issues such as biofuel production and wastewater treatment.
2.2.1 Wastewater Treatment MBR technology has gained a stable position among other methods for treating water and wastewater and has an important role in the treatment and sanitation of decentralized wastewater, especially in in United Nations Clean Water and Sanitation development plan (Shannon et al., 2010; Tobias et al., 2017). Use MF and UF to separate solids from liquids in MBRs has shown good results because they recycle water during the process. There are other benefits to using MBRs, which has led to these systems being employed for municipal wastewater treatment similar to industrial wastewater treatment (Judd, 2016). Because of properties such as a low propensity to foul, high chemical resistance, and high structural integrity of ceramic membranes, ceramic membranes are increasingly being used in MBRs compared with conventional polymeric membranes; those were common before ceramic membranes became less expensive (Wang et al., 2014; Meng et al., 2017). The tendency for fouling to occur in ceramic membranes containing titanium on a mixed oxide substrate is caused by bonding between the fouling agents and the membrane’s hydrophilic surface (Lee et al., 2013). Alumina-based ceramic membranes demonstrated great filtration properties compared with conventional polymeric membranes in an anaerobic MBR used to treat wastewater ( polyvinylidene fluoride [PVDF] with a pore size of 0.08 mm) (Jeong et al., 2018). Results from ceramic membrane performance during wastewater treatment in aerobic submerged MBRs with various pore sizes (0.08e0.30 mm) showed that less surface roughness and a small pore size slowed the rate of fouling (Jin et al., 2010).
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The presence of organic hydrophilic materials in the wastewater leads to the blockage of large pores in membranes and fouling, but ceramic membranes with good resistance during cleaning with chemical agents (Yue et al., 2015) allow the membranes to recycle during first stage and result in good performance (Mei et al., 2017; Yue et al., 2018). Alumina ceramic membranes have been used to treat wastewater with a pore size of 0.1e0.2 mm. For example, one was employed in an aerobic submerged MBR coupled with an anaerobic sludge blanket reactor to treat industrial effluents from beverage and pharmaceutical corporations (Niwa et al., 2016). Different kinds of materials have been used to scour the surface of ceramic membranes and control fouling in MBRs: • polyvinyl alcohol (PVA) in the form of gel beads, • activated carbon (granular), and • glass-based beads. Using glass beads led to surface abrasion in ceramic mem€ ppenbecker et al., 2017; Aslam et al., 2018b; Jeong branes (Du et al., 2017b). On the other hand, the use of charcoal and an electrical field may be useful in controlling the fouling rate. The performance of charcoal in enhancing microbial diversity in MBRs is useful (Zhang et al., 2017) and the simultaneous use of 0.1-mm flat sheets of ceramic-based membranes of metals such as Fe and Cu as an electrode can help to control fouling using direct current power (Dong et al., 2018). Silica membranes have been considered for the treatment of wastewater in MBRs and the pretreatment of industrial feed: for example, to remove oil from MBR feed. In a submerged aerobic MBR used for wastewater (2e5 g chemical oxygen demand [COD]/L) treatment with kaolin and a pore size of 0.2e0.4 mm and tubular geometry, the decline in flux was insignificant at low transmembrane pressures (Rezakazemi et al., 2018). The wastewater of a pharmaceutical industrial company was treated using a composite silica membrane incorporating highdensity polyethylene in a submerged aerobic MBR; it showed good results compared with a plain membrane (Aslam et al., 2018a). A PVAesilica membrane used to treat a molasses diluted solution in an MBR with a submerged configuration had an acceptable performance with respect to conventional polymeric systems. The rate of fouling was high at the beginning because of pore blockage (Bilad et al., 2015). In other experimental work, a ceramic silica-based membrane was used to treat wastewater in anaerobic MBRs in a submerged style. The results were comparable to those for alumina-based membranes used to remove COD and methane (Jeong et al., 2017a).
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Vacuum pump
Influent
Effluent Feed pump Bio gas sparging
Alumina-bades ceramic membrane
Feed pump Wastewater
Gas diaphragm pump
Influent
Effluent
Feed tank Bio gas sparging Pyrophyllite-based ceramic membrane
Gas diaphragm pump
Figure 8.4 Scheme of submerged aerobic membrane bioreactor with alumina coating.
Another study compared the performance of submerged and side-stream configurations of MBRs. The membrane was same in both configurations. It was made from a single layer of galumina on a tubular substrate from clay-alumina. The configurations had the same results in this study (Banerjee et al., 2016). A few examples were reported of silica-based MBRs used to treat wastewater. A model of submerged aerobic MBR with alumina coating was tested to remove nitrogen and obtain high-quality water for agriculture (Jeong et al., 2017a), as shown in Fig. 8.4. One of the gas separation MBR with internal gas recycling is presented in Fig. 8.5.
CO2-rich
H2/CO2
H2-rich
Gas separation membrane
Fermentative H2 reactor
Figure 8.5 Gas separation membrane bioreactor with internal gas recycling.
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An MBR (capacity not specified) employing membranes fabricated from waste ceramic and agroindustrial processes was tested in a wastewater treatment plant in Murcia, Spain; the effluent was reused in agriculture (Jeong et al., 2017a).
2.2.2 Biofuel Production Because of population growth and the high demand for energy, researchers are motivated to study biochemical conversion in biomass and the production of likely energy sources such as hydrogen, butanol, and ethanol. A variety of lignocellulosic biomass sources have been used to obtain pentose and hexose sugars containing hydrolysates that are then used as the substrate for fermentation. MBRs have considerable potential for biofuel production to maintain a high cell concentration in continuous fermentation as well as to remove inhibitory compounds (Ylitervo et al., 2013). High product concentrations inhibit the biochemical conversion of sugars to alcohols. The continuous removal of alcohol from the fermentation broth can reduce product inhibition, resulting in a longer process and higher cumulative production and thus less waste in a liquid form. Membranes are used to hold cells in the production of biohydrogen. One of the most important operations in this area is pervaporation (PV), which is done in different kinds of membranes. Results are comparable, such as the fermentation of some alcohols in continuous versus noncontinuous modes in polymeric and ceramic membranes (Van Hecke and De Wever, 2017). A comparison of butanol and ethanol production using different cycles and employing fermentation in integrated polydimethylsiloxane (PDMS) PV membranes demonstrated different results and advantages. The experiment showed a high conversion in ethanol fermentation and high process stability in butanol fermentation. To study this process deeply, the researchers used cross-linked PDMS cast on PVDF (Jung et al., 2018). In addition to PV, ethanol recovery by membrane distillation (MD) was reported (Gryta et al., 2000). Removing components such as ethanol or volatile components from the fermentation broth using direct contact membrane distillation with polypropylene membranes caused an increase in effective conversion compared with the conventional czyk, 2016). process of fermentation (Tomaszewska and Białon
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Integrated fermentation using vacuum membrane distillation and a polytetrafluoroethylene membrane led to high productivity in ethanol production. Finally, mechanical vapor compression and the fractional condensation of permeate resulted in energy efficiency in this process (Li et al., 2018). According to a review on ethanol fermentation, there was extensive work on cell recycling in ethanol fermentation (Ylitervo et al., 2013). In addition, one of the most important issues is regarding recycling unconverted substrate materials. For instance, one study combined nanofiltration (NF) (to recycle and recover unconverted glucose back to the bioreactor) and MF (to enhance cell density and recycle cells in the bioreactor) (Saha et al., 2019). Polymeric membranes (e.g., a 0.50-mm PVDF MF membrane and polyamide thin-film composite NF membranes with a 150- to 300-Da molecular weight cutoff) were used to obtain complete cell retention followed by 58%e86% glucose rejection. A limited number of silica-based or silicate-based ceramic or composite membranes have been used for applications such as MD MBRs, PV, and multilayer silicalite-coated membranes, all of which were prepared on stainless-steel disks and examined for lez ethanol separation from the fermentation broth (Orozco-Gonza et al., 2016). Because of outstanding properties such as high power conversion efficiency, high energy density, and low pollution, biohydrogen has become one of the most important fuels. The use of MBRs has improved hydrogen production using an anaerobic approach (Bakonyi et al., 2017). Also, using MF and UF to incorporate membranes leads to an efficient operation and avoiding volatile fatty acid accumulation in anaerobic hydrogen production and lower hydraulic retention times (Buitrón et al., 2019). In another study, in a continuous anaerobic MBR for hydrogen production, gas and cell separation were performed simultaneously. Commercial polymeric MF and gas separation (GS) membranes were integrated with bioreactor and of MF was used for cell retention and GS for the membrane to remove H2 from fermenter off-gases (Bakonyi et al., 2017). The issue of hydraulic retention time can easily affect MF performance and the bioreactor; 30% in situ enrichment of hydrogen was obtained in the system. The process of hydrogen evolution in dark fermentation can be facilitated by gas extraction (Singer et al., 2018); moreover, the enriched fraction of carbon dioxide can be used to separate hydrogen from the reactor (Bakonyi et al., 2017) (Fig. 8.5).
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In general, there is an impressive extension for coordinating GS layers in biochemical transformations focused on different biofuels. These incorporate (1) algal bioreactors to evacuate the oxygen that is created and to maintain ideal carbon dioxide levels; (2) anaerobic bioreactors to isolate carbon dioxidee methane in the produced biogas to acquire highly immaculate methane; and (3) anaerobic bioreactors delivering hydrogen, in which the carbon dioxideehydrogen separation process is necessary to obtain hydrogen of high purity.
3. Development of Ceramic Membrane Bioreactors This section discusses the new generation of MBRs that employ ceramic membranes in an anaerobic form, as well as improvements in wastewater treatment.
3.1 Anaerobic Membrane Bioreactors With Ceramic Membranes The ideal situation for using a ceramic MBR comprises one or more accompanying condition: • the need for water of high quality. MBRs that are employ ceramic membranes are more reliable for wastewater treatment and water quality after treatment and improve the lifetime of the filtration process. • industrial wastewater and wastewaters that is hard to treat (difficult wastewater), There are some requirements such as chemical agents, high temperature, and the presence of solvents: for example, biorefractory materials and oily water. • the log lifetime for membranes, because of the minimal production of sludge during treatment and a low energy requirement, and small space to install equipment. • high or medium loading of organic materials. Operating costs for MBR systems primarily depend on the volumetric loading factor, whereas for conventional and common systems, organic loading mostly determines the air supply requirement. During high-strength wastewater treatment with low fluxes, the additional energy input parameter for filtration is not significant compared with the need for an aeration basin; consequently ceramic MBRs are competitive. • the process of decentralized urban wastewater treatment. Small-size MBR systems for treating and reusing municipal
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wastewater in isolated communities, for example, require a robust process with limited required maintenance that does not need to be performed by highly qualified personnel. Use of an external ceramic membrane system in MBRs can overcome most problems that are present in polymeric membranes because of their mechanical strength, long lifetime, and tolerance for hard chemical conditions. Although decentralized systems do not represent the main market for ceramic MBR systems, it is an interesting niche application for this technology. • operational adaptability. An investigation of a few MBRs in industry demonstrated that wastewater treatment and the executives are in charge of over 60% of daily work and support costs. The activity is progressively adaptable when earthenware films are used because their capacity to help high varieties of suspended solids can prompt weekly or even monthly sludge drainage and dewatering operations (Meabe et al., 2011). Ceramic membrane layers can be used in both anaerobic and aerobic MBR frameworks. However, coupling ceramic-based membrane layers into anaerobic MBRs is required to suggest greater potential thanks to the previously mentioned favorable circumstances, particularly in their obstruction against destructive synthetic concoctions and higher than regular working temperatures. Moreover, anaerobic procedures have been generally viewed as a conceivable method for financial feasibility, particularly considering the treatment of high-quality mechanical (industrial) wastewaters, because of higher amount of COD substances, the potential for long life, and the lower generation of abundance muck (Mei et al., 2017). In 1982, Dorr Oliver presented an anaerobic MBR (AnMBR) framework for the treatment of modern industrial wastewater. Pilot-scale research demonstrated that MBRs are a promising innovation for treating high-quality wastewater. It is expected that critical upgrades should be made with respect to membrane proficiency. Countless numbers of MBR investigations have been conducted into urban wastewater treatment. Their outcomes suggest that combining ceramic membranes with an MBR may be a reasonable elective innovation and alternative choice because of proof of the lower degree of fouling and the capacity to clean the layers of membrane thoroughly with chemical materials without shortening the lifetime of the membrane (Sun et al., 2018).
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3.2 Ceramic Membrane Bioreactor Treatment Performance (Wastewater) Many research studies have suggested implementing ceramic membranes in MBR systems to treat industrial or municipal wastewater. Zhang et al. (2018) used a flat sheet anaerobic ceramic MBR (AnCMBR) to treat high-strength dyeing wastewater and compared it with an upflow anaerobic sludge blanket (UASB) reactor. Researchers have proposed developing ceramic-based membranes in MBR frameworks to treat modern or urban wastewater. Zhang et al. (2018) used an anaerobic-level sheet ceramic membrane bioreactor (CMBR) to treat high-quality colored wastewater and contrasted it with a UASB reactor. Although total nitrogen and total phosphorus (TP) evacuation rates were low for the two kinds of reactors and the removal by the CMBR of a few toxins was better compared with the UASB reactor. After 150 days of activity, the COD and TP evacuation rates for the CMBR were 20% and 2.5 higher, respectively, compared with the UASB reactor. Moreover, methane (CH4) creation achieved 0.18 m3/kg COD for the anaerobic CMBR, in contrast to 0.10 m3/kg COD for the UASB reactor during the last period of the investigation. Niwa et al. (2016) assessed the execution and performance of a full-scale plant using a system based on a hybrid membrane composed of a UASB reactor followed by an MBR. Wastewater from industry mixed with other wastewaters was first treated by the UASB reactor (working at just 6.3 h of hydraulic retention time [HRT]), followed by the ceramic-based MBR (with 8 h of HRT), with generally low lifetime use (0.76 kWh m3). The feed water incorporated the blended wastewater release of more than 300 processing plants, including sustenance, refreshment, and pharmaceutical businesses from the mechanical region of Jurong (a district in western Singapore) and contained (among others) solvents, oil, and synthetic compounds. The outcome demonstrated that the blend of the UASB reactor and clay MBR accomplished a generally effective expulsion of 93.6% for oil despite of the high introductory oil and oil fixations in the feed water (Fig. 8.6). Although anaerobic treatment is generally analyzed as a major innovation to treat high-quality modern industrial wastewater, it has also been employed for urban wastewater because of its potential for recuperation as biogas (containing methane) and for the lower amount slop generated. Much research has
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Screen Raw feed
Equalization tank
UASB reactor
Heavier sludge Anoxic zone
Aerobic zone
Membrane tank
Permeate
Sludge circulation Excess sludge
Figure 8.6 Schematic flow diagram of demonstration plant. UASB, upflow anaerobic sludge blanket.
developed ceramic-based membranes in AnMBR frameworks to treat household or mechanical wastewater. Aslam et al. (2018a) developed a staged-anaerobic fluidized bed ceramic MBR system for the treatment of the effluent produced by an anaerobic fluidized bed bioreactor. In another study, a system was created that manufactured low-quality residential wastewater and an alumina-based ceramic membrane with tubular geometry (Al2O3). The outcomes demonstrated that the effectiveness total COD elimination was up to 93% whereas the particular normal solvent COD in the saturate was under 30 mg/L. Cho et al. (2018) examined the performance of an anaerobic MBR coupled with a ceramic membrane under a wide range of working temperatures (15 C, 20 C, 25 C, and 35 C) in order to evaluate its potential for the co-management of domestic wastewater (DWW) and for food waste recycling wastewater (FRW). The system framework effectively worked at temperatures higher than 20 C with generally high than normal COD elimination (>93.9%), methane creation (>0.1 L CH4/g COD evacuated), and acceptable filtration (>6.0 L/hr/m2), with the recommendation that the AnCMBR could be effectively connected as a standard procedure for overseeing DWW and FRW squandered waste streams.
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Ceramic-based MBRs of various pore sizes (80, 200, and 300 nm) in three AnCMBR frameworks treated household wastewater to inspect treatment efficiency. The average effectiveness of the total COD elimination was modified to 86e88% (Yue et al., 2015).
4. Economic Assessment of Ceramic Membrane Bioreactors in Wastewater Treatment MBRs stand outs among the most progressive and powerful innovations in the field of wastewater treatment including the procedures of UF and MF with the customary organic decontamination of active sludge (silt). Because of important innovations, the fundamental components of MBR are the membranes, which create a resilient obstruction against infections and microscopic organisms and result in a high level of purification.
4.1 Materials and Methods An economic point of view is one of most important aspects of MBRs use and membranes and membrane modules are two main factors of assessing cost. Two kinds of MBRs are assesses based on their membrane position: submerged and external module. From operational and financial perspectives, each has its focal points and problems. Subsequently, we will examine the kinds of membrane modules that are favorable according to a financial perspective (Makisha et al., 2018). As the type of structure, the most popular is the immiscible module of MBRs, because of the straightforward design. This factor is critical because it suggests various other points of interest that are quite streamlined, such as the lessened expense of overhauling the worked MBR. With straightforward development, factors such as modernizing the bioreactor can be considered; in the meantime, the workforce necessary to administer the job is smaller. Each element influences both the underlying initial cost of bio membrane reactors (ICBMs) expense and the cost of devaluation that are inevitable. Obviously, adding a straightforward configuration involves certain expenses. For this situation, in the case of MBRs, it has a special positive effect. For MBRs based on pressure, the factor has a value few times higher (about three or four times). Typically, it adds up to 40e100 L/m2$h; most modules used in MBRs under most conditions do not surpass a capacity of
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10e30 L/m2$h. Loss in performance can be a serious drawback, as the time dependency of water which sifted in unit is exceptionally vital. In addition, in general, for projects with huge volumes of filtration, wastewater is necessary. Nevertheless, now and then, when the ideal opportunity for which the filtration is performed is not as imperative, it may be disregarded (Kulakov and Makisha, 2017). Pressure and immersive MBR modules also differ in methods of reducing membrane contamination. MBRs based on pressure have used uncommon innovative cross-flow (implying a transverse stream), chemical cleaning, discharging, and air flushing; in immersive air blending modules, discharging and synthetic cleaning are employed. Turn-around flushing is not practical because it results in less of a demand in the market for MBRs with huge modules. For MBRs with a huge module and less complicated structure, it is possible to accomplish a higher-pressure thickness of layers in correlation with the modules’ weight. The MBR’s pressure is low, just 50e200 m2/m3, whereas the mentioned factor is about 600 m2/m3 in submerged MBRs, which is higher by three to 12 times. In this case, unfortunately, such a huge gap in packing density of membranes partially causes the loss of immersive MBRs before the pressure ones in specific productivity. The straightforwardness structure and low explicit efficiency diminish the use of vitality, which assumes a critical job for the long-term business task of MBRs. The use of intensity by weight of MBRs modules surpasses 0.50 kW$h/m3, whereas requirements for MBRs are about 0.20e4.4 kW$h/m3. In light of these parameters, we can make an initial determination about the financial practicality of every specific framework. After contrasting the attributes of immersion and pressure modules of MBRs, we conclude that the establishment and consequent task of huge MBRs are substantially less expensive as far as mounting and use. Of course, in cases requiring high specific power, it is necessary to use MBRs of pressure type, especially for overhauling vast areas of effluent belonging to urban areas and city centers. Various types of membranes are used in different kinds of membrane modules. The varied shapes include tubular, flat, or hollow fibers. The kind of selected membranes depends on the nature of the tainted water and the cost-effectiveness. Polymerbased membranes are used in these cases; however, in some special cases, a rounded sheath may be composed of earthenware. Empty fiber films outperform their rivals as far as the fiber
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pressing thickness, which specifically influences the nature of the water planned for purification. The density of prepared membranes varied from 300 m2/m3 to 600 m2/m3, which is a lot higher than that for flat membranes (50e150 m2/m3) and tubular membranes (<300 m2/m3). Membranes with a hollow fiber design are pioneers regard to performance. Their use of material clearly will decrease or increase the cost of development (Kulakov and Makisha, 2017). The membranes’ specific productivity is one of the most important characteristics. While the passing a benign cleaning more water can pass the membrane through fibers, the more productive structure will work along these lines, spare assets. In this issue, will without a doubt level matrices prevail with their high profitability, leaving tubular membranes and hollow fibers far behind. Membranes have a propensity to end up obstructed by the development of dregs. There is a “critical stream” which implies a passable stream, the overflow of which prompts the unsuitably concentrated development of sediment that turns into a hindrance for the ordinary working of the film module. A wide range of membranes are obstructed by a change in force. Level films tend to be obstructed more quickly than other choices. This demonstrates that MBRs will need increased cleaning, which will increase the expense of activity, so the nature of the purified water and the stability of cleaning productivity are important. Because of their design, membranes with a tubular geometry will be obstructed more than their rivals. Membranes with a hollow fiber design have a normal position in the classification, which makes them the most adjustable alternative. Throughout the operation, at some point or another, the topic emerges of supplanting specific membranes because of harm and breakage of ones that were used. Membranes with a hollow fiber design are subpar compared with flat membranes and those with a tubular design; if this is important, isolated components can be replaced, bringing the structure back to top-notch throughput. Moreover, it is inevitable for membrane module design to change. On the off chance that that damage occurs that is unusual, most likely places where breaks occur will stop up with slop and the module will keep on working. In the event that we depend on factors that we have mentioned previously, we can presume that the inclination will be toward membranes with a hollow fiber design, which are used in both submersible and pressure modules because of the upsides of their qualities. Notwithstanding their negative and positive characteristics,
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among the different choices, membranes with a hollow fiber design are least expensive. During the investigation of accessible essential pieces of ceramic MBRs, it can also be presumed that there are six various types of gradation. By combining the types of membrane modules with different layer types as membrane, it can be accomplished compelling cleaning, yet in addition monetary advantages when considering all the strong and weak sides of these innovations. When operating MBRs, various major issues emerge with regard to the development of this innovation. Excluding the subtleties of the functioning of the biological treatment itself, these issues suggest the priority of problems: • contamination of filters and membranes through use; • contamination that causes membrane damage; • failure facing automation system communication lines; • failure in blowing systems membrane; • aerator and blower failure; • grid and net contamination; and • failure of auxiliary equipment of membrane. If we look at the expense of activity in figures, for an examination of costs, the capital expenses for developing MBRs plants that are usable for treating wastewater run from V6000 to as much as V1000 for 1 m3/day, depending upon the framework’s efficiency. Moreover, 30e60% of cost comes from the auxiliary equipment of the plant, which is a noteworthy piece of the absolute whole. The expense of membrane squares block changes from V75 to V150/m2 with a normal explicit profitability of 15e30 L/h per 1 m2 of film zone. The expense of treating household wastewater using a membrane system with this design costs V0.08e0.15/m3. Moreover, lower values are achieved by using of modules based on a hollow fiber design. Absolute working performance costs total V0.24e0.25/m3. In a comparison of the performance of the traditional technological system and the MBR scheme in treating wastewater, there are some noticeable differences, including economic benefits and cleaning efficiency. Both of these factors are closely related to and are not independent. Some characteristics can clarify the boundaries between the traditional and new MBR technology: • Most of the microorganisms and solids remain in a retentate side in MBR technology with no need for reagents, increasing the effect of the biochemical oxygen demand and COD on purification; • the minimum value of water residence time duration in the separation zone, which includes solid phase; and
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• complete retention of microorganisms because of changing the selected condition in the reactor that belongs to sludge (activated). All of these issues control reactor conditions easily by changing and controlling some factors such as: • increasing the age of the sludge (activated) by changing hydraulic loading on the reactor; • controlling the speed of biological destruction with time controlled in the reactor (suspension time); • excluding the effect of sludge (activated) sedimentation characteristics on water purification; and • using the biosensors to increase the system’s stability because of fluctuating water contaminates at a high concentration. Nevertheless, in case financial considerations are primary, we can address various issues brought about by expenses from all phases of innovation with MBRs, instead of technologies that were used before these innovations. Between the MBRs with high cost (Catalysis Today, 331, 68e77), the particular expense of the membrane process units themselves is for all intents and purposes autonomous from profitability. There are also the issues of unavoidably polluting membranes and the resulting consequent cost, wasting for power and film substitutes, the increasingly mind-boggling process control and mechanization framework, and the problem with providing adequate air circulation for high dynamic muck for MBRs. To evaluate the cost of a typical MBR and traditional system for wastewater treatment, economic indicators of these systems are summarized in Table 8.1. As reported in the table, the total cost of MBR systems
Table 8.1 Economic Indicators Demonstrated Based on Technical Method (Makisha et al., 2018). Equipment for Traditional System
Cost of Construction (Euros)
Primary clarifiers Aerotank mixer Secondary clarifiers Posttreatment Total cost
23,190.04 33,028.34 15,730.82 27,601.56 99,550.77
Equipment for Membrane Bioreactor System
Cost of Construction (Euros)
Aerotank mixer
10,307.34
Membrane unit
88,043.48
Total cost
98,350.82
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is lower than for traditional system. However, depending on the membrane types the preference may change. Thus, to show the cost-effectiveness of ceramic MBRs, a synthesis of the cost of ceramic membranes is more useful.
5. Conclusion and Future Trends The increasing need to solve water shortage issues has spurred a large amount of research. Current innovations in polymeric membranes involve wastewater treatment and desalination to resolve worldwide water contamination and water deficiency issues. In parallel with the improvements in polymeric membranes, researchers and architects have been widely examining advancements in increasingly effective membranes for the economical generation of consumable water. The practicality and science of fired materials offer an extraordinary chance to understand the ideal performance of ceramic membranes focused on applications in industry. Membranes based on ceramics have been viewed as a fascinating class of membrane for desalination and wastewater treatment. Among the MBRs with high capital cost, current ceramic membrane science and innovation are working together on a few urgent methods, such as the progressive structure of individual or hybrid ceramic membrane materials and atoms that can upgrade usefulness, selectivity, and flux; the fabrication of defect-free support and thin membranes or those without an interlayer; and the development of freestanding membranes specially based on carbon using facile approaches, all using methods and materials that decrease the cost of MBR production. With more ideas and strategies emerging to improve processing techniques, ceramic membranes hold promising potential for real-world applications.
List of Abbreviations GS MBR MD MF NF PDMS PV PVA PVDF UASB UF
Gas Separation Membrane Bioreactor Membrane Distillation Microfiltration Nanofiltration Polydimethylsiloxane Pervaporation Polyvinyl alcohol Polyvinylidene fluoride Upflow anaerobic sludge blanket Ultrafiltration
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References Aslam, M., Ahmad, R., Kim, J., 2018a. Recent Developments in Biofouling Control in Membrane Bioreactors for Domestic Wastewater Treatment. Separation and Purification Technology. Aslam, M., Yang, P., Lee, P.-H., Kim, J., 2018b. Novel staged anaerobic fluidized bed ceramic membrane bioreactor: energy reduction, fouling control and microbial characterization. J. Membr. Sci. 553, 200e208. lafi-Bakó, K., Bakonyi, P., Buitrón, G., Valdez-Vazquez, I., Nemestóthy, N., Be 2017. A novel gas separation integrated membrane bioreactor to evaluate the impact of self-generated biogas recycling on continuous hydrogen fermentation. Appl. Energy 190, 813e823. Banerjee, P., Kumar Dey, T., Sarkar, S., Swarnakar, S., Mukhopadhyay, A., Ghosh, S., 2016. Treatment of cosmetic effluent in different configurations of ceramic UF membrane based bioreactor: toxicity evaluation of the untreated and treated wastewater using catfish (Heteropneustes fossilis). Chemosphere 146, 133e144. Bilad, M., Marbelia, L., Laine, C., Vankelecom, I.F., 2015. A PVCesilica mixedmatrix membrane (MMM) as novel type of membrane bioreactor (MBR) membrane. J. Membr. Sci. 493, 19e27. ez, K.M., Herna ndez-Mendoza, C.E., 2019. Biohydrogen Buitrón, G., Muñoz-Pa production using a granular sludge membrane bioreactor. Fuel 241, 954e961. Castilho, L.R., Mitchell, D.A., Freire, D.M., 2009. Production of polyhydroxyalkanoates (PHAs) from waste materials and by-products by submerged and solid-state fermentation. Bioresour. Technol. 100, 5996e6009. Dong, Z., Shang, W., Dong, W., Zhao, L., Li, M., Wang, R., Sun, F., 2018. Suppression of membrane fouling in the ceramic membrane bioreactor (CMBR) by minute electric field. Bioresour. Technol. 270, 113e119. € ppenbecker, B., Engelhart, M., Cornel, P., 2017. Fouling mitigation in Du anaerobic membrane bioreactor using fluidized glass beads: evaluation fitness for purpose of ceramic membranes. J. Membr. Sci. 537, 69e82. Fan, Y., Li, G., Wu, L., Yang, W., Dong, C., Xu, H., Fan, W., 2006. Treatment and reuse of toilet wastewater by an airlift external circulation membrane bioreactor. Process Biochem. 41, 1364e1370. Fatimah, I., Sahroni, I., Putra, H.P., Nugraha, M.R., Hasanah, U.A., 2015. Ceramic membrane based on TiO2-modified kaolinite as a low cost material for water filtration. Appl. Clay Sci. 118, 207e211. Gryta, M., Morawski, A.W., Tomaszewska, M., 2000. Ethanol production in membrane distillation bioreactor. Catal. Today 56, 159e165. Jalilnejad, E., Vahabzadeh, F., 2014. Use of a packed-bed airlift reactor with net draft tube to study kinetics of naphthalene degradation by Ralstonia eutropha. Environ. Sci. Pollut. Control Ser. 21, 4592e4604. Jeong, Y., Cho, K., Kwon, E.E., Tsang, Y.F., Rinklebe, J., Park, C., 2017a. Evaluating the feasibility of pyrophyllite-based ceramic membranes for treating domestic wastewater in anaerobic ceramic membrane bioreactors. Chem. Eng. J. 328, 567e573. Jeong, Y., Hermanowicz, S.W., Park, C., 2017b. Treatment of food waste recycling wastewater using anaerobic ceramic membrane bioreactor for biogas production in mainstream treatment process of domestic wastewater. Water Res. 123, 86e95. Jeong, Y., Kim, Y., Jin, Y., Hong, S., Park, C., 2018. Comparison of filtration and treatment performance between polymeric and ceramic membranes in
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anaerobic membrane bioreactor treatment of domestic wastewater. Separ. Purif. Technol. 199, 182e188. Jin, L., Ong, S.L., Ng, H.Y., 2010. Comparison of fouling characteristics in different pore-sized submerged ceramic membrane bioreactors. Water Res. 44, 5907e5918. Judd, S.J., 2016. The status of industrial and municipal effluent treatment with membrane bioreactor technology. Chem. Eng. J. 305, 37e45. Jung, H.-M., Lee, J.Y., Lee, J.-H., Oh, M.-K., 2018. Improved production of isobutanol in pervaporation-coupled bioreactor using sugarcane bagasse hydrolysate in engineered Enterobacter aerogenes. Bioresour. Technol. 259, 373e380. Khan, S.J., Ilyas, S., Javid, S., Visvanathan, C., Jegatheesan, V., 2011. Performance of suspended and attached growth MBR systems in treating high strength synthetic wastewater. Bioresour. Technol. 102, 5331e5336. Krzeminski, P., Leverette, L., Malamis, S., Katsou, E., 2017. Membrane bioreactorsea review on recent developments in energy reduction, fouling control, novel configurations, LCA and market prospects. J. Membr. Sci. 527, 207e227. Kulakov, A., Makisha, N., 2017. Removal of nitrogen and phosphorous from domestic wastewater. In: MATEC Web of Conferences. EDP Sciences, p. 10019. Lakard, S., Magnenet, C., Mokhter, M., Euvrard, M., Buron, C., LAKARD, B., 2015. Retention of Cu (II) and Ni (II) ions by filtration through polymer-modified membranes. Separ. Purif. Technol. 149, 1e8. Le-Clech, P., Chen, V., Fane, T.A., 2006. Fouling in membrane bioreactors used in wastewater treatment. J. Membr. Sci. 284, 17e53. Lee, S.-J., Dilaver, M., Park, P.-K., Kim, J.-H., 2013. Comparative analysis of fouling characteristics of ceramic and polymeric microfiltration membranes using filtration models. J. Membr. Sci. 432, 97e105. Li, J., Zhou, W., Fan, S., Xiao, Z., Liu, Y., Liu, J., Qiu, B., Wang, Y., 2018. Bioethanol production in vacuum membrane distillation bioreactor by permeate fractional condensation and mechanical vapor compression with polytetrafluoroethylene (PTFE) membrane. Bioresour. Technol. 268, 708e714. Liao, Y., Bokhary, A., Maleki, E., Liao, B., 2018. A Review of Membrane Fouling and its Control in Algal-Related Membrane Processes. Bioresource technology. Makisha, N., Saveliev, O., Katella, S., 2018. Cost aspects of membrane bioreactors for wastewater treatment. In: IOP Conference Series: Earth and Environmental Science. IOP Publishing, p. 012037. Meabe, E., Lopetegui, J., Ollo, J., Lardies, S., 2011. Ceramic Membrane Bioreactor: potential applications and challenges for the future. In: Proceedings of the MBR Asia International Conference. Kuala Lumpur, Malaysia, pp. 25e26. Mei, X., Quek, P.J., Wang, Z., Ng, H.Y., 2017. Alkali-assisted membrane cleaning for fouling control of anaerobic ceramic membrane bioreactor. Bioresour. Technol. 240, 25e32. Meng, F., Zhang, S., Oh, Y., Zhou, Z., Shin, H.-S., Chae, S.-R., 2017. Fouling in membrane bioreactors: an updated review. Water Res. 114, 151e180. Niwa, T., Hatamoto, M., Yamashita, T., Noguchi, H., Takase, O., Kekre, K.A., Ang, W.S., Tao, G., Seah, H., Yamaguchi, T., 2016. Demonstration of a fullscale plant using an UASB followed by a ceramic MBR for the reclamation of industrial wastewater. Bioresour. Technol. 218, 1e8. lez, N., Bustamante, F., Acosta-Ca rdenas, A., 2016. Experimental Orozco-Gonza assessment of the integration of in situ removal of ethanol by pervaporation
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with a simultaneous saccharificationefermentation process. J. Chem. Technol. Biotechnol. 91, 3011e3017. Radjenovic, J., Matosic, M., Mijatovic, I., Petrovic, M., Barceló, D., 2007. Membrane bioreactor (MBR) as an advanced wastewater treatment technology. In: Emerging Contaminants from Industrial and Municipal Waste. Springer. _ Arda, M., Yu € ksel, M., Yoshizuka, K., Recepoglu, Y.K., Kabay, N., Yılmaz-Ipek, I., Nishihama, S., 2018. Elimination of boron and lithium coexisting in geothermal water by adsorption-membrane filtration hybrid process. Separ. Sci. Technol. 53, 856e862. Rezakazemi, M., Maghami, M., Mohammadi, T., 2018. High loaded synthetic hazardous wastewater treatment using lab-scale submerged ceramic membrane bioreactor. Period. Polytech. Chem. Eng. 62, 299e304. Saha, K., Maharana, A., Sikder, J., Chakraborty, S., Curcio, S., Drioli, E., 2019. Continuous production of bioethanol from sugarcane bagasse and downstream purification using membrane integrated bioreactor. Catal. Today 331, 68e77. Santos, A., Ma, W., Judd, S.J., 2011. Membrane bioreactors: two decades of research and implementation. Desalination 273, 148e154. Shannon, M.A., Bohn, P.W., Elimelech, M., Georgiadis, J.G., Marinas, B.J., Mayes, A.M., 2010. Science and technology for water purification in the coming decades. In: Nanoscience and Technology: A Collection of Reviews from Nature Journals. World Scientific. Singer, S., Magnusson, L., Hou, D., LO, J., Maness, P.-C., Ren, Z.J., 2018. Anaerobic membrane gas extraction facilitates thermophilic hydrogen production from Clostridium thermocellum. Environ. Sci. Water Res. Technol. 4, 1771e1782. Sun, H., Liu, H., Han, J., Zhang, X., Cheng, F., Liu, Y., 2018. Chemical cleaningassociated generation of dissolved organic matter and halogenated byproducts in ceramic MBR: ozone versus hypochlorite. Water Res. 140, 243e250. Sutton, P.M., 2003. Membrane bioreactors for industrial wastewater treatment: the state-of-the-art based on full scale commercial applications. Proc. Water Environ. Fed. 23e32, 2003. € nzle, R., Gebauer, H., Gru € ndl, H., Morgenroth, E., Tobias, R., O’Keefe, M., Ku Pronk, W., Larsen, T.A., 2017. Early testing of new sanitation technology for urban slums: the case of the blue diversion toilet. Sci. Total Environ. 576, 264e272. czyk, L., 2016. Ethanol production from whey in a Tomaszewska, M., Białon bioreactor coupled with direct contact membrane distillation. Catal. Today 268, 156e163. Van Hecke, W., De Wever, H., 2017. High-flux POMS organophilic pervaporation for ABE recovery applied in fed-batch and continuous set-ups. J. Membr. Sci. 540, 321e332. Wang, Z., Ma, J., Tang, C.Y., Kimura, K., Wang, Q., Han, X., 2014. Membrane cleaning in membrane bioreactors: a review. J. Membr. Sci. 468, 276e307. Ylitervo, P., Akinbomi, J., Taherzadeh, M.J., 2013. Membrane bioreactors’ potential for ethanol and biogas production: a review. Environ. Technol. 34, 1711e1723. Yue, X., Koh, Y.K.K., Ng, H.Y., 2015. Effects of dissolved organic matters (DOMs) on membrane fouling in anaerobic ceramic membrane bioreactors (AnCMBRs) treating domestic wastewater. Water Res. 86, 96e107.
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Yue, X., Koh, Y.K.K., Ng, H.Y., 2018. Membrane fouling mitigation by NaClOassisted backwash in anaerobic ceramic membrane bioreactors for the treatment of domestic wastewater. Bioresour. Technol. 268, 622e632. Zhang, Q., Jin, P., Ngo, H., Shi, X., Guo, W., Yang, S., Wang, X., Wang, X., Dzakpasu, M., Yang, W., 2016. Transformation and utilization of slowly biodegradable organic matters in biological sewage treatment of anaerobic anoxic oxic systems. Bioresour. Technol. 218, 53e61. Zhang, W., Liu, F., Wang, D., Jin, Y., 2018. Impact of reactor configuration on treatment performance and microbial diversity in treating high-strength dyeing wastewater: anaerobic flat-sheet ceramic membrane bioreactor versus upflow anaerobic sludge blanket reactor. Bioresour. Technol. 269, 269e275. Zhang, W., Liu, X., Wang, D., Jin, Y., 2017. Effects of bamboo charcoal on fouling and microbial diversity in a flat-sheet ceramic membrane bioreactor. Bioresour. Technol. 243, 1020e1026. Zheng, X., Wei, Y., Wang, Z., Zhang, Z., 2013. Report for Sustainable Development Strategy of China Water Treatment IndustrydMembrane Industry. China Renmin University Press, Beijing.
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Faculty of Chemical Engineering, Urmia University of Technology, Urmia, Iran; 2Institute on Membrane Technology, National Research Council, University of Calabria, Rende (CS), Italy
1. Introduction The growth of the world’s population and the tendency of reside in urban areas are the most important reasons for problems involving the availability of water resources, especially clean water. The fast rapid of growing of industries and urbanization produce wastewater in large amounts that includes contaminates such as: • organic toxic materials, • ammonium pollutant, • metals (heavy), and • complex and complicated composites. The discharge of untreated wastewater into the environment causes consequences for the underground water supply that lead to human health problems (Zhang et al., 2016; Jalilnejad and Vahabzadeh, 2014). According to statistical research, more than 85% of wastewater returns to the environment untreated. Many treatment methods are useful in this regard (Recepoglu et al., 2018): • physical methods, including separation and adsorption techniques; • chemical methods, including oxidation and coagulationflocculation techniques; and • biological methods including sequencing batch reactors and activated sludge. Current Trends and Future Developments on (Bio-) Membranes. https://doi.org/10.1016/B978-0-12-816822-6.00008-2 Copyright © 2020 Elsevier Inc. All rights reserved.
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The process for treating water depends on the intended use for the treated water; factors include the cost, energy consumption, and the space needed for a treatment plant. Among the various methods, membrane bioreactors (MBRs) are the most promising for industrial and municipal wastewater treatment (Fatimah et al., 2015; Lakard et al., 2015). Properties such as effective performance and a compact setup, which are important characters in membrane technology, have drawn the attention of researchers to MBR technology, especially for the wastewater treatment industry. MBR treatment has notable properties with respect to other methods, some of which are (Lakard et al., 2015; Liao et al., 2018): • highly efficient performance in nutrient elimination and a low energy requirement (0.6e2.3 kWh/m3) • less need for equipment • complete retention of biomass materials • good quality and enough effluent • high capacity of organic loadings in volume • less production of sludge The operation of MBRs can be divided into two main steps, membrane filtration with a physicochemical mechanism and activated sludge (mixed bacteria), to degrade organic contaminants and nutrient substances (such as phosphorus and nitrogen). The membrane system rejects most colloids and biomass particles that are part of solutes using microfiltration (MF) and ultrafiltration (UF), whereas in MBR, separation and biological treatment occur simultaneously and activated sludge causes particle waste to change into flock before the membrane separation unit (Liao et al., 2018; Krzeminski et al., 2017). The high cost of membranes and their maintenance have resulted in decreased interest in MBR systems and an increase in the cost of membranes. Because of technological improvements, MBR has become an economically feasible option for mediumscale systems with a population capacity about 10,000e100,000 or equivalent (Krzeminski et al., 2017; Castilho et al., 2009). Many MBR units are in use in different parts of the world. The first large-scale installation was in the United States in 1990 by General Motors Company, to treat industrial wastewater. After that, the first MBR using an internal membrane system was for the industrial food industry in 1998 in North America (Sutton, 2003). More than 200 MBR plants to treat wastewater have been installed all over the world (each plant’s capacity is more than 10,000 m3/d), with a total of more than 20 million m3/d (Zheng et al., 2013). More than 2200 MBR systems are under construction
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internationally, and it is predicted that the global market will grow by about 20%, most of which will be for wastewater treatment in municipal areas (Judd, 2016). The main goal of this chapter is to provide a broad introduction to MBRs, materials used in membranes, MBR configurations, parameters affecting their performance, and a cost assessment of ceramic MBRs. Applications of MBRs in wastewater treatment in industry and affluent cities, which covers membrane and biomass characteristics, are discussed. The limitation of MBRs and their mitigation behavior are also reviewed. Finally, in enable a good selection among MBRs based on the needs of treatment, an economic investigation into MBRs and their advantages and disadvantages are discussed.
2. Fundamentals of Membrane Bioreactors In this part of study, two important issues regarding MBRs will be discussed. The first part addresses the most common configurations of MBRs, and second part presents applications of MBRs such as biofuel production and wastewater treatment.
2.1 Configurations of Membrane Bioreactors There are some problems and challenges to using MBR on a large scale and these systems have not been thoroughly tested, so different configurations of MBRs have been introduced, including external, submerged, and airlift designs, as shown in Figs. 8.1e8.3.
Pressure gauge
Process control
O2/Air
Pressure gauge
Treated water Wastewater Pump Mixing + Aeration
Membrane unit
Figure 8.1 External model of membrane bioreactor scheme.
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Feed
Bio
Membrane module Permeate
Feed
Air
Figure 8.2 Airlift model of membrane bioreactor scheme.
Wastewater
Effluent/ Permeate Membrane Bioreactor
Figure 8.3 Submerged model of membrane bioreactor scheme.
The configuration of external MBRs is designed to overcome membrane fouling problems with direct control of hydrodynamic parameters. It has some advantages such as a high flux factor of production and easy replacement of the membrane, but an important disadvantage is the high energy consumption. The submerged design does not have this problem; it involves less rigorous cleaning and a lower operating cost (Le-Clech et al., 2006). Among these configurations, the airlift design optimizes energy consumption using the principle of the side stream with airlift. All three configurations are used in landfill leachate, municipal wastewater, and sewage wastewater treatment processes, but the airlift model has not been used much (Fan et al., 2006). The sludge activation method can occur in two different ways: suspended growth or medium immobilized growth; these are different from the distribution method (Radjenovic et al., 2007).
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According to the suspended growth system, microorganisms are able to move freely in liquid media and have the ability to recover after flock settles and to return to the system during the next treatment. During immobilized growth on natural substrates such as polyurethane, kissiris, zeolite, and carbon (activated), microorganisms survive as a biofilm shape on the substrates (Khan et al., 2011). Finally, according to studies, submerged MBR was inexpensive compared with other MBR systems (Santos et al., 2011).
2.2 Applications of Membrane Bioreactors This part of study discusses applications of MBRs for important issues such as biofuel production and wastewater treatment.
2.2.1 Wastewater Treatment MBR technology has gained a stable position among other methods for treating water and wastewater and has an important role in the treatment and sanitation of decentralized wastewater, especially in in United Nations Clean Water and Sanitation development plan (Shannon et al., 2010; Tobias et al., 2017). Use MF and UF to separate solids from liquids in MBRs has shown good results because they recycle water during the process. There are other benefits to using MBRs, which has led to these systems being employed for municipal wastewater treatment similar to industrial wastewater treatment (Judd, 2016). Because of properties such as a low propensity to foul, high chemical resistance, and high structural integrity of ceramic membranes, ceramic membranes are increasingly being used in MBRs compared with conventional polymeric membranes; those were common before ceramic membranes became less expensive (Wang et al., 2014; Meng et al., 2017). The tendency for fouling to occur in ceramic membranes containing titanium on a mixed oxide substrate is caused by bonding between the fouling agents and the membrane’s hydrophilic surface (Lee et al., 2013). Alumina-based ceramic membranes demonstrated great filtration properties compared with conventional polymeric membranes in an anaerobic MBR used to treat wastewater ( polyvinylidene fluoride [PVDF] with a pore size of 0.08 mm) (Jeong et al., 2018). Results from ceramic membrane performance during wastewater treatment in aerobic submerged MBRs with various pore sizes (0.08e0.30 mm) showed that less surface roughness and a small pore size slowed the rate of fouling (Jin et al., 2010).
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The presence of organic hydrophilic materials in the wastewater leads to the blockage of large pores in membranes and fouling, but ceramic membranes with good resistance during cleaning with chemical agents (Yue et al., 2015) allow the membranes to recycle during first stage and result in good performance (Mei et al., 2017; Yue et al., 2018). Alumina ceramic membranes have been used to treat wastewater with a pore size of 0.1e0.2 mm. For example, one was employed in an aerobic submerged MBR coupled with an anaerobic sludge blanket reactor to treat industrial effluents from beverage and pharmaceutical corporations (Niwa et al., 2016). Different kinds of materials have been used to scour the surface of ceramic membranes and control fouling in MBRs: • polyvinyl alcohol (PVA) in the form of gel beads, • activated carbon (granular), and • glass-based beads. Using glass beads led to surface abrasion in ceramic mem€ ppenbecker et al., 2017; Aslam et al., 2018b; Jeong branes (Du et al., 2017b). On the other hand, the use of charcoal and an electrical field may be useful in controlling the fouling rate. The performance of charcoal in enhancing microbial diversity in MBRs is useful (Zhang et al., 2017) and the simultaneous use of 0.1-mm flat sheets of ceramic-based membranes of metals such as Fe and Cu as an electrode can help to control fouling using direct current power (Dong et al., 2018). Silica membranes have been considered for the treatment of wastewater in MBRs and the pretreatment of industrial feed: for example, to remove oil from MBR feed. In a submerged aerobic MBR used for wastewater (2e5 g chemical oxygen demand [COD]/L) treatment with kaolin and a pore size of 0.2e0.4 mm and tubular geometry, the decline in flux was insignificant at low transmembrane pressures (Rezakazemi et al., 2018). The wastewater of a pharmaceutical industrial company was treated using a composite silica membrane incorporating highdensity polyethylene in a submerged aerobic MBR; it showed good results compared with a plain membrane (Aslam et al., 2018a). A PVAesilica membrane used to treat a molasses diluted solution in an MBR with a submerged configuration had an acceptable performance with respect to conventional polymeric systems. The rate of fouling was high at the beginning because of pore blockage (Bilad et al., 2015). In other experimental work, a ceramic silica-based membrane was used to treat wastewater in anaerobic MBRs in a submerged style. The results were comparable to those for alumina-based membranes used to remove COD and methane (Jeong et al., 2017a).
Chapter 8 A COMPARATIVE EVALUATION OF CERAMIC MEMBRANE BIOREACTORS
Vacuum pump
Influent
Effluent Feed pump Bio gas sparging
Alumina-bades ceramic membrane
Feed pump Wastewater
Gas diaphragm pump
Influent
Effluent
Feed tank Bio gas sparging Pyrophyllite-based ceramic membrane
Gas diaphragm pump
Figure 8.4 Scheme of submerged aerobic membrane bioreactor with alumina coating.
Another study compared the performance of submerged and side-stream configurations of MBRs. The membrane was same in both configurations. It was made from a single layer of galumina on a tubular substrate from clay-alumina. The configurations had the same results in this study (Banerjee et al., 2016). A few examples were reported of silica-based MBRs used to treat wastewater. A model of submerged aerobic MBR with alumina coating was tested to remove nitrogen and obtain high-quality water for agriculture (Jeong et al., 2017a), as shown in Fig. 8.4. One of the gas separation MBR with internal gas recycling is presented in Fig. 8.5.
CO2-rich
H2/CO2
H2-rich
Gas separation membrane
Fermentative H2 reactor
Figure 8.5 Gas separation membrane bioreactor with internal gas recycling.
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An MBR (capacity not specified) employing membranes fabricated from waste ceramic and agroindustrial processes was tested in a wastewater treatment plant in Murcia, Spain; the effluent was reused in agriculture (Jeong et al., 2017a).
2.2.2 Biofuel Production Because of population growth and the high demand for energy, researchers are motivated to study biochemical conversion in biomass and the production of likely energy sources such as hydrogen, butanol, and ethanol. A variety of lignocellulosic biomass sources have been used to obtain pentose and hexose sugars containing hydrolysates that are then used as the substrate for fermentation. MBRs have considerable potential for biofuel production to maintain a high cell concentration in continuous fermentation as well as to remove inhibitory compounds (Ylitervo et al., 2013). High product concentrations inhibit the biochemical conversion of sugars to alcohols. The continuous removal of alcohol from the fermentation broth can reduce product inhibition, resulting in a longer process and higher cumulative production and thus less waste in a liquid form. Membranes are used to hold cells in the production of biohydrogen. One of the most important operations in this area is pervaporation (PV), which is done in different kinds of membranes. Results are comparable, such as the fermentation of some alcohols in continuous versus noncontinuous modes in polymeric and ceramic membranes (Van Hecke and De Wever, 2017). A comparison of butanol and ethanol production using different cycles and employing fermentation in integrated polydimethylsiloxane (PDMS) PV membranes demonstrated different results and advantages. The experiment showed a high conversion in ethanol fermentation and high process stability in butanol fermentation. To study this process deeply, the researchers used cross-linked PDMS cast on PVDF (Jung et al., 2018). In addition to PV, ethanol recovery by membrane distillation (MD) was reported (Gryta et al., 2000). Removing components such as ethanol or volatile components from the fermentation broth using direct contact membrane distillation with polypropylene membranes caused an increase in effective conversion compared with the conventional czyk, 2016). process of fermentation (Tomaszewska and Białon
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Integrated fermentation using vacuum membrane distillation and a polytetrafluoroethylene membrane led to high productivity in ethanol production. Finally, mechanical vapor compression and the fractional condensation of permeate resulted in energy efficiency in this process (Li et al., 2018). According to a review on ethanol fermentation, there was extensive work on cell recycling in ethanol fermentation (Ylitervo et al., 2013). In addition, one of the most important issues is regarding recycling unconverted substrate materials. For instance, one study combined nanofiltration (NF) (to recycle and recover unconverted glucose back to the bioreactor) and MF (to enhance cell density and recycle cells in the bioreactor) (Saha et al., 2019). Polymeric membranes (e.g., a 0.50-mm PVDF MF membrane and polyamide thin-film composite NF membranes with a 150- to 300-Da molecular weight cutoff) were used to obtain complete cell retention followed by 58%e86% glucose rejection. A limited number of silica-based or silicate-based ceramic or composite membranes have been used for applications such as MD MBRs, PV, and multilayer silicalite-coated membranes, all of which were prepared on stainless-steel disks and examined for lez ethanol separation from the fermentation broth (Orozco-Gonza et al., 2016). Because of outstanding properties such as high power conversion efficiency, high energy density, and low pollution, biohydrogen has become one of the most important fuels. The use of MBRs has improved hydrogen production using an anaerobic approach (Bakonyi et al., 2017). Also, using MF and UF to incorporate membranes leads to an efficient operation and avoiding volatile fatty acid accumulation in anaerobic hydrogen production and lower hydraulic retention times (Buitrón et al., 2019). In another study, in a continuous anaerobic MBR for hydrogen production, gas and cell separation were performed simultaneously. Commercial polymeric MF and gas separation (GS) membranes were integrated with bioreactor and of MF was used for cell retention and GS for the membrane to remove H2 from fermenter off-gases (Bakonyi et al., 2017). The issue of hydraulic retention time can easily affect MF performance and the bioreactor; 30% in situ enrichment of hydrogen was obtained in the system. The process of hydrogen evolution in dark fermentation can be facilitated by gas extraction (Singer et al., 2018); moreover, the enriched fraction of carbon dioxide can be used to separate hydrogen from the reactor (Bakonyi et al., 2017) (Fig. 8.5).
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In general, there is an impressive extension for coordinating GS layers in biochemical transformations focused on different biofuels. These incorporate (1) algal bioreactors to evacuate the oxygen that is created and to maintain ideal carbon dioxide levels; (2) anaerobic bioreactors to isolate carbon dioxidee methane in the produced biogas to acquire highly immaculate methane; and (3) anaerobic bioreactors delivering hydrogen, in which the carbon dioxideehydrogen separation process is necessary to obtain hydrogen of high purity.
3. Development of Ceramic Membrane Bioreactors This section discusses the new generation of MBRs that employ ceramic membranes in an anaerobic form, as well as improvements in wastewater treatment.
3.1 Anaerobic Membrane Bioreactors With Ceramic Membranes The ideal situation for using a ceramic MBR comprises one or more accompanying condition: • the need for water of high quality. MBRs that are employ ceramic membranes are more reliable for wastewater treatment and water quality after treatment and improve the lifetime of the filtration process. • industrial wastewater and wastewaters that is hard to treat (difficult wastewater), There are some requirements such as chemical agents, high temperature, and the presence of solvents: for example, biorefractory materials and oily water. • the log lifetime for membranes, because of the minimal production of sludge during treatment and a low energy requirement, and small space to install equipment. • high or medium loading of organic materials. Operating costs for MBR systems primarily depend on the volumetric loading factor, whereas for conventional and common systems, organic loading mostly determines the air supply requirement. During high-strength wastewater treatment with low fluxes, the additional energy input parameter for filtration is not significant compared with the need for an aeration basin; consequently ceramic MBRs are competitive. • the process of decentralized urban wastewater treatment. Small-size MBR systems for treating and reusing municipal
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wastewater in isolated communities, for example, require a robust process with limited required maintenance that does not need to be performed by highly qualified personnel. Use of an external ceramic membrane system in MBRs can overcome most problems that are present in polymeric membranes because of their mechanical strength, long lifetime, and tolerance for hard chemical conditions. Although decentralized systems do not represent the main market for ceramic MBR systems, it is an interesting niche application for this technology. • operational adaptability. An investigation of a few MBRs in industry demonstrated that wastewater treatment and the executives are in charge of over 60% of daily work and support costs. The activity is progressively adaptable when earthenware films are used because their capacity to help high varieties of suspended solids can prompt weekly or even monthly sludge drainage and dewatering operations (Meabe et al., 2011). Ceramic membrane layers can be used in both anaerobic and aerobic MBR frameworks. However, coupling ceramic-based membrane layers into anaerobic MBRs is required to suggest greater potential thanks to the previously mentioned favorable circumstances, particularly in their obstruction against destructive synthetic concoctions and higher than regular working temperatures. Moreover, anaerobic procedures have been generally viewed as a conceivable method for financial feasibility, particularly considering the treatment of high-quality mechanical (industrial) wastewaters, because of higher amount of COD substances, the potential for long life, and the lower generation of abundance muck (Mei et al., 2017). In 1982, Dorr Oliver presented an anaerobic MBR (AnMBR) framework for the treatment of modern industrial wastewater. Pilot-scale research demonstrated that MBRs are a promising innovation for treating high-quality wastewater. It is expected that critical upgrades should be made with respect to membrane proficiency. Countless numbers of MBR investigations have been conducted into urban wastewater treatment. Their outcomes suggest that combining ceramic membranes with an MBR may be a reasonable elective innovation and alternative choice because of proof of the lower degree of fouling and the capacity to clean the layers of membrane thoroughly with chemical materials without shortening the lifetime of the membrane (Sun et al., 2018).
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3.2 Ceramic Membrane Bioreactor Treatment Performance (Wastewater) Many research studies have suggested implementing ceramic membranes in MBR systems to treat industrial or municipal wastewater. Zhang et al. (2018) used a flat sheet anaerobic ceramic MBR (AnCMBR) to treat high-strength dyeing wastewater and compared it with an upflow anaerobic sludge blanket (UASB) reactor. Researchers have proposed developing ceramic-based membranes in MBR frameworks to treat modern or urban wastewater. Zhang et al. (2018) used an anaerobic-level sheet ceramic membrane bioreactor (CMBR) to treat high-quality colored wastewater and contrasted it with a UASB reactor. Although total nitrogen and total phosphorus (TP) evacuation rates were low for the two kinds of reactors and the removal by the CMBR of a few toxins was better compared with the UASB reactor. After 150 days of activity, the COD and TP evacuation rates for the CMBR were 20% and 2.5 higher, respectively, compared with the UASB reactor. Moreover, methane (CH4) creation achieved 0.18 m3/kg COD for the anaerobic CMBR, in contrast to 0.10 m3/kg COD for the UASB reactor during the last period of the investigation. Niwa et al. (2016) assessed the execution and performance of a full-scale plant using a system based on a hybrid membrane composed of a UASB reactor followed by an MBR. Wastewater from industry mixed with other wastewaters was first treated by the UASB reactor (working at just 6.3 h of hydraulic retention time [HRT]), followed by the ceramic-based MBR (with 8 h of HRT), with generally low lifetime use (0.76 kWh m3). The feed water incorporated the blended wastewater release of more than 300 processing plants, including sustenance, refreshment, and pharmaceutical businesses from the mechanical region of Jurong (a district in western Singapore) and contained (among others) solvents, oil, and synthetic compounds. The outcome demonstrated that the blend of the UASB reactor and clay MBR accomplished a generally effective expulsion of 93.6% for oil despite of the high introductory oil and oil fixations in the feed water (Fig. 8.6). Although anaerobic treatment is generally analyzed as a major innovation to treat high-quality modern industrial wastewater, it has also been employed for urban wastewater because of its potential for recuperation as biogas (containing methane) and for the lower amount slop generated. Much research has
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Screen Raw feed
Equalization tank
UASB reactor
Heavier sludge Anoxic zone
Aerobic zone
Membrane tank
Permeate
Sludge circulation Excess sludge
Figure 8.6 Schematic flow diagram of demonstration plant. UASB, upflow anaerobic sludge blanket.
developed ceramic-based membranes in AnMBR frameworks to treat household or mechanical wastewater. Aslam et al. (2018a) developed a staged-anaerobic fluidized bed ceramic MBR system for the treatment of the effluent produced by an anaerobic fluidized bed bioreactor. In another study, a system was created that manufactured low-quality residential wastewater and an alumina-based ceramic membrane with tubular geometry (Al2O3). The outcomes demonstrated that the effectiveness total COD elimination was up to 93% whereas the particular normal solvent COD in the saturate was under 30 mg/L. Cho et al. (2018) examined the performance of an anaerobic MBR coupled with a ceramic membrane under a wide range of working temperatures (15 C, 20 C, 25 C, and 35 C) in order to evaluate its potential for the co-management of domestic wastewater (DWW) and for food waste recycling wastewater (FRW). The system framework effectively worked at temperatures higher than 20 C with generally high than normal COD elimination (>93.9%), methane creation (>0.1 L CH4/g COD evacuated), and acceptable filtration (>6.0 L/hr/m2), with the recommendation that the AnCMBR could be effectively connected as a standard procedure for overseeing DWW and FRW squandered waste streams.
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Ceramic-based MBRs of various pore sizes (80, 200, and 300 nm) in three AnCMBR frameworks treated household wastewater to inspect treatment efficiency. The average effectiveness of the total COD elimination was modified to 86e88% (Yue et al., 2015).
4. Economic Assessment of Ceramic Membrane Bioreactors in Wastewater Treatment MBRs stand outs among the most progressive and powerful innovations in the field of wastewater treatment including the procedures of UF and MF with the customary organic decontamination of active sludge (silt). Because of important innovations, the fundamental components of MBR are the membranes, which create a resilient obstruction against infections and microscopic organisms and result in a high level of purification.
4.1 Materials and Methods An economic point of view is one of most important aspects of MBRs use and membranes and membrane modules are two main factors of assessing cost. Two kinds of MBRs are assesses based on their membrane position: submerged and external module. From operational and financial perspectives, each has its focal points and problems. Subsequently, we will examine the kinds of membrane modules that are favorable according to a financial perspective (Makisha et al., 2018). As the type of structure, the most popular is the immiscible module of MBRs, because of the straightforward design. This factor is critical because it suggests various other points of interest that are quite streamlined, such as the lessened expense of overhauling the worked MBR. With straightforward development, factors such as modernizing the bioreactor can be considered; in the meantime, the workforce necessary to administer the job is smaller. Each element influences both the underlying initial cost of bio membrane reactors (ICBMs) expense and the cost of devaluation that are inevitable. Obviously, adding a straightforward configuration involves certain expenses. For this situation, in the case of MBRs, it has a special positive effect. For MBRs based on pressure, the factor has a value few times higher (about three or four times). Typically, it adds up to 40e100 L/m2$h; most modules used in MBRs under most conditions do not surpass a capacity of
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10e30 L/m2$h. Loss in performance can be a serious drawback, as the time dependency of water which sifted in unit is exceptionally vital. In addition, in general, for projects with huge volumes of filtration, wastewater is necessary. Nevertheless, now and then, when the ideal opportunity for which the filtration is performed is not as imperative, it may be disregarded (Kulakov and Makisha, 2017). Pressure and immersive MBR modules also differ in methods of reducing membrane contamination. MBRs based on pressure have used uncommon innovative cross-flow (implying a transverse stream), chemical cleaning, discharging, and air flushing; in immersive air blending modules, discharging and synthetic cleaning are employed. Turn-around flushing is not practical because it results in less of a demand in the market for MBRs with huge modules. For MBRs with a huge module and less complicated structure, it is possible to accomplish a higher-pressure thickness of layers in correlation with the modules’ weight. The MBR’s pressure is low, just 50e200 m2/m3, whereas the mentioned factor is about 600 m2/m3 in submerged MBRs, which is higher by three to 12 times. In this case, unfortunately, such a huge gap in packing density of membranes partially causes the loss of immersive MBRs before the pressure ones in specific productivity. The straightforwardness structure and low explicit efficiency diminish the use of vitality, which assumes a critical job for the long-term business task of MBRs. The use of intensity by weight of MBRs modules surpasses 0.50 kW$h/m3, whereas requirements for MBRs are about 0.20e4.4 kW$h/m3. In light of these parameters, we can make an initial determination about the financial practicality of every specific framework. After contrasting the attributes of immersion and pressure modules of MBRs, we conclude that the establishment and consequent task of huge MBRs are substantially less expensive as far as mounting and use. Of course, in cases requiring high specific power, it is necessary to use MBRs of pressure type, especially for overhauling vast areas of effluent belonging to urban areas and city centers. Various types of membranes are used in different kinds of membrane modules. The varied shapes include tubular, flat, or hollow fibers. The kind of selected membranes depends on the nature of the tainted water and the cost-effectiveness. Polymerbased membranes are used in these cases; however, in some special cases, a rounded sheath may be composed of earthenware. Empty fiber films outperform their rivals as far as the fiber
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pressing thickness, which specifically influences the nature of the water planned for purification. The density of prepared membranes varied from 300 m2/m3 to 600 m2/m3, which is a lot higher than that for flat membranes (50e150 m2/m3) and tubular membranes (<300 m2/m3). Membranes with a hollow fiber design are pioneers regard to performance. Their use of material clearly will decrease or increase the cost of development (Kulakov and Makisha, 2017). The membranes’ specific productivity is one of the most important characteristics. While the passing a benign cleaning more water can pass the membrane through fibers, the more productive structure will work along these lines, spare assets. In this issue, will without a doubt level matrices prevail with their high profitability, leaving tubular membranes and hollow fibers far behind. Membranes have a propensity to end up obstructed by the development of dregs. There is a “critical stream” which implies a passable stream, the overflow of which prompts the unsuitably concentrated development of sediment that turns into a hindrance for the ordinary working of the film module. A wide range of membranes are obstructed by a change in force. Level films tend to be obstructed more quickly than other choices. This demonstrates that MBRs will need increased cleaning, which will increase the expense of activity, so the nature of the purified water and the stability of cleaning productivity are important. Because of their design, membranes with a tubular geometry will be obstructed more than their rivals. Membranes with a hollow fiber design have a normal position in the classification, which makes them the most adjustable alternative. Throughout the operation, at some point or another, the topic emerges of supplanting specific membranes because of harm and breakage of ones that were used. Membranes with a hollow fiber design are subpar compared with flat membranes and those with a tubular design; if this is important, isolated components can be replaced, bringing the structure back to top-notch throughput. Moreover, it is inevitable for membrane module design to change. On the off chance that that damage occurs that is unusual, most likely places where breaks occur will stop up with slop and the module will keep on working. In the event that we depend on factors that we have mentioned previously, we can presume that the inclination will be toward membranes with a hollow fiber design, which are used in both submersible and pressure modules because of the upsides of their qualities. Notwithstanding their negative and positive characteristics,
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among the different choices, membranes with a hollow fiber design are least expensive. During the investigation of accessible essential pieces of ceramic MBRs, it can also be presumed that there are six various types of gradation. By combining the types of membrane modules with different layer types as membrane, it can be accomplished compelling cleaning, yet in addition monetary advantages when considering all the strong and weak sides of these innovations. When operating MBRs, various major issues emerge with regard to the development of this innovation. Excluding the subtleties of the functioning of the biological treatment itself, these issues suggest the priority of problems: • contamination of filters and membranes through use; • contamination that causes membrane damage; • failure facing automation system communication lines; • failure in blowing systems membrane; • aerator and blower failure; • grid and net contamination; and • failure of auxiliary equipment of membrane. If we look at the expense of activity in figures, for an examination of costs, the capital expenses for developing MBRs plants that are usable for treating wastewater run from V6000 to as much as V1000 for 1 m3/day, depending upon the framework’s efficiency. Moreover, 30e60% of cost comes from the auxiliary equipment of the plant, which is a noteworthy piece of the absolute whole. The expense of membrane squares block changes from V75 to V150/m2 with a normal explicit profitability of 15e30 L/h per 1 m2 of film zone. The expense of treating household wastewater using a membrane system with this design costs V0.08e0.15/m3. Moreover, lower values are achieved by using of modules based on a hollow fiber design. Absolute working performance costs total V0.24e0.25/m3. In a comparison of the performance of the traditional technological system and the MBR scheme in treating wastewater, there are some noticeable differences, including economic benefits and cleaning efficiency. Both of these factors are closely related to and are not independent. Some characteristics can clarify the boundaries between the traditional and new MBR technology: • Most of the microorganisms and solids remain in a retentate side in MBR technology with no need for reagents, increasing the effect of the biochemical oxygen demand and COD on purification; • the minimum value of water residence time duration in the separation zone, which includes solid phase; and
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• complete retention of microorganisms because of changing the selected condition in the reactor that belongs to sludge (activated). All of these issues control reactor conditions easily by changing and controlling some factors such as: • increasing the age of the sludge (activated) by changing hydraulic loading on the reactor; • controlling the speed of biological destruction with time controlled in the reactor (suspension time); • excluding the effect of sludge (activated) sedimentation characteristics on water purification; and • using the biosensors to increase the system’s stability because of fluctuating water contaminates at a high concentration. Nevertheless, in case financial considerations are primary, we can address various issues brought about by expenses from all phases of innovation with MBRs, instead of technologies that were used before these innovations. Between the MBRs with high cost (Catalysis Today, 331, 68e77), the particular expense of the membrane process units themselves is for all intents and purposes autonomous from profitability. There are also the issues of unavoidably polluting membranes and the resulting consequent cost, wasting for power and film substitutes, the increasingly mind-boggling process control and mechanization framework, and the problem with providing adequate air circulation for high dynamic muck for MBRs. To evaluate the cost of a typical MBR and traditional system for wastewater treatment, economic indicators of these systems are summarized in Table 8.1. As reported in the table, the total cost of MBR systems
Table 8.1 Economic Indicators Demonstrated Based on Technical Method (Makisha et al., 2018). Equipment for Traditional System
Cost of Construction (Euros)
Primary clarifiers Aerotank mixer Secondary clarifiers Posttreatment Total cost
23,190.04 33,028.34 15,730.82 27,601.56 99,550.77
Equipment for Membrane Bioreactor System
Cost of Construction (Euros)
Aerotank mixer
10,307.34
Membrane unit
88,043.48
Total cost
98,350.82
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is lower than for traditional system. However, depending on the membrane types the preference may change. Thus, to show the cost-effectiveness of ceramic MBRs, a synthesis of the cost of ceramic membranes is more useful.
5. Conclusion and Future Trends The increasing need to solve water shortage issues has spurred a large amount of research. Current innovations in polymeric membranes involve wastewater treatment and desalination to resolve worldwide water contamination and water deficiency issues. In parallel with the improvements in polymeric membranes, researchers and architects have been widely examining advancements in increasingly effective membranes for the economical generation of consumable water. The practicality and science of fired materials offer an extraordinary chance to understand the ideal performance of ceramic membranes focused on applications in industry. Membranes based on ceramics have been viewed as a fascinating class of membrane for desalination and wastewater treatment. Among the MBRs with high capital cost, current ceramic membrane science and innovation are working together on a few urgent methods, such as the progressive structure of individual or hybrid ceramic membrane materials and atoms that can upgrade usefulness, selectivity, and flux; the fabrication of defect-free support and thin membranes or those without an interlayer; and the development of freestanding membranes specially based on carbon using facile approaches, all using methods and materials that decrease the cost of MBR production. With more ideas and strategies emerging to improve processing techniques, ceramic membranes hold promising potential for real-world applications.
List of Abbreviations GS MBR MD MF NF PDMS PV PVA PVDF UASB UF
Gas Separation Membrane Bioreactor Membrane Distillation Microfiltration Nanofiltration Polydimethylsiloxane Pervaporation Polyvinyl alcohol Polyvinylidene fluoride Upflow anaerobic sludge blanket Ultrafiltration
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