Characterization of distillery wastewater – An approach to retrofit existing effluent treatment plant operation with phycoremediation

Accepted Manuscript Characterization of distillery wastewater – An approach to retrofit existing effluent treatment plant operation with phycoremediation Krishnamoorthy Sankaran, Manickam Premalatha, Muthukaruppan Vijayasekaran PII:

S0959-6526(17)30249-4

DOI:

10.1016/j.jclepro.2017.02.045

Reference:

JCLP 8971

To appear in:

Journal of Cleaner Production

Received Date: 14 September 2016 Revised Date:

6 February 2017

Accepted Date: 6 February 2017

Please cite this article as: Sankaran K, Premalatha M, Vijayasekaran M, Characterization of distillery wastewater – An approach to retrofit existing effluent treatment plant operation with phycoremediation, Journal of Cleaner Production (2017), doi: 10.1016/j.jclepro.2017.02.045. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Characterization of distillery wastewater – an approach to retrofit existing effluent

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treatment plant operation with phycoremediation

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*Sankaran Krishnamoorthy a, Manickam Premalatha a and Muthukaruppan Vijayasekaran b

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a

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Technology, Tiruchirappalli, Tamil Nadu, India – 620 015.

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b

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Tiruchirappalli, Tamil Nadu, India – 620 004.

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Algae Biotechnology Laboratory, Dept. of Energy & Environment, National Institute of

Research & Development, Trichy Distilleries & Chemicals Ltd., Senthaneerpuram,

*Corresponding

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[email protected] (M. Premalatha) +91-9894600407; [email protected] (M. Vijayasekaran)

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+91-7667976675

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Author:

[email protected]

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(Sankaran

K)

+91-9940946997;

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Abbreviations

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BMSW

-

Anaerobically digested distillery wastewater (Biomethanated Spent Wash)

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BOD

-

Biological/Biochemical Oxygen Demand

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CHN Analyzer

-

Carbon, Hydrogen and Nitrogen Analyzer

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COD

-

Chemical Oxygen Demand

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DEE

-

Department of Energy & Environment

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DSC

-

Differential Scanning Calorimeter

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FT-MIR Spectroscopy

-

Fourier Transform – Mid Infrared Spectroscopy

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RO

-

Reverse Osmosis

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RSW

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Raw distillery wastewater (Raw Spent Wash)

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TDS

-

Total Dissolved Solids

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TGA

-

Thermo Gravimetric Analyzer

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TS

-

Total Solids

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TSS

-

Total Suspended Solids

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UATR

-

Universal Attenuated Total Reflectance

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Abstract

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Raw distillery wastewater (RSW) has the characteristics such as pH 4.0 – 4.6; chemical oxygen

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demand 85000 – 110000 ppm; total dissolved solids 85000 – 110000 ppm and biological oxygen

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demand 25000 – 35000 ppm. Anaerobic digestion is the widely used treatment process in

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distillery to reduce the pollution load by 65 – 70%. Further, the pollution load is treated by RO

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process. The operation of RO process becomes difficult due to high influent load. This research

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work suggests the positioning of an additional biotreatment step, called phycoremediation to

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retrofit into the existing effluent treatment plant (ETP). The wastewater from the nearby

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distillery is collected at the various treatment stages of ETP such as before and after anaerobic

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digestion, settling lagoons and RO process. The physico-chemical, thermal and spectroscopic

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characteristics of wastewater are studied and the analysis is made based on the stage-wise

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characterization. It is inferred from the analysis that the phycoremediation step needs to be

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retrofitted into the existing ETP after anaerobic digestion. Anaerobically digested distillery

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wastewater treatment with Oscillatoria sp. resulted further reduction in chemical oxygen demand

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up to 55%, which reduce the influent load to the reverse osmosis plant.

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Keywords

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Distillery wastewater; Characterization; Anaerobic digestion; Reverse Osmosis; Microalgae

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Total word count (including table and graph captions): 7,328

1. Introduction

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The importance of alcohol industries is steadily increasing due to the widespread applications of

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alcohol and its derived products such as acetaldehyde, acetic acid and ethyl acetate to

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pharmaceuticals, foods, paints and perfumery manufacturing industries. There are about 319

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distilleries in India which produce 3.25 x 109 L of alcohol and generate 40.4 x 109 L of

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wastewater annually (Bharagava et al., 2009). The discharge of distillery wastewater into the

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environment before treatment is harmful and has high pollution potential that include

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eutrophication potential, global warming potential, toxicity-related impacts, energy balance,

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water usage and land usage (Zang et al., 2015). Ministry of Environment and Forests (MoEF)

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listed alcohol industries at the top among the ‘Red category’ industries (Tewari et al., 2007).

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Indian Government body, Central Pollution Control Board (CPCB) in 2003, insisted that

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distilleries must achieve zero liquid discharge (ZLD) by the end of 2005. Distilleries at southern

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region of India achieve ZLD mainly through anaerobic digestion and reverse osmosis (RO) plant

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(Fig. 1) since it poses various advantages that include the generation of biogas and recovery of

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clean water. However, the efficiency of effluent treat plant (ETP) suffers due to the high

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pollution load of wastewater across the stages of operation.

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Anaerobic digestion is the best and most practiced first step of ETP scheme since

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BOD/COD>0.25. Pollution load reduction (up to 65% in terms of COD) and energy recovery as

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biogas are achieved through anaerobic digestion simultaneously (Rajeshwari et al., 2000).

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Settling lagoons which are placed after anaerobic digestion are found to be useful to settle the

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portion of total suspended solids (TSS) by gravity. The overflow from settling lagoons is sent to

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RO plant. The permeate (water) of reverse osmosis is recycled to the alcohol production unit,

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reducing the water requirement. The reject of the RO plant is mixed with the pressmud and

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marketed as a biocompost. Alternative to this ETP process, the evaporation technique is followed

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for treating the distillery wastewater in some distilleries. The outcome of evaporation is pure

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water and concentrated sludge (approximately 50% moisture). This sludge is further burnt to

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produce power and the potassium rich ash is recovered from the combustion of the sludge.

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However, the power requirement is a challenge for both the schemes to achieve ZLD. Excluding

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anaerobic digestion, all the other operations of ETP consume a lot of electrical power and require

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high maintenance cost.

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digestion followed by RO process could be reduced by introducing one more pretreatment step

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The energy consumption of the overall ETP in case of anaerobic

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before RO, to reduce the pollution load further. Any one of the physical, chemical or biological

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methods could be chosen as a pretreatment method to RO. However, physical and chemical

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treatments have larger limitations with respect to the cost, characteristics of the influent

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(requiring dilution), generation of secondary pollutants, requirement of energy and power

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(Padoley et al., 2012; Sangave and Pandit, 2004; Siles et al., 2011). Adding one more biological

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treatment could be thought of, if that could help in reducing the pollution load. Microalgae

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technology can offer elegant solution for the tertiary wastewater treatment due to its ability to

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utilize the pollutants for its growth (Phycoremediation). Further, it is an environment friendly

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approach since secondary pollutants are not generated rather it produces biogas (Rawat et al.,

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2011). The distillery wastewater contains both organic and inorganic pollution load. Organic

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load could be used as a substrate for the growth of microalgae and inorganic load could be used

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for its nutrients requirement. The energy required for the growth of microalgae could be utilized

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from the sun (Photoheterotrophs) (Wang et al., 2010). Microalgae such as Chlorella,

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Scenedesmus, Phormidium, Oscillatoria, Botryococcus, Chlamydomonas and Spirulina are

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useful in treating the wastewater and the efficiency of treatment is promising (Ruiz-Marin et al.,

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2010). Characteristics of the wastewater at different stages of the ETP scheme is essential to

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find the position of microalgae treatment step as a suitable retrofit to the existing ETP. However,

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no literature is available regarding the characteristics of distillery wastewater at different

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treatment stages. So, the objective of this work is to study the detailed characterization of

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distillery wastewater (physicochemical, thermal and spectroscopic characterization) at different

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stages of ETP operation so as to couple phycoremediation at right position and uplift distillery as

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a cleaner industry. The stages of the sampling include (a) after distillation and alcohol separation

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(raw distillery wastewater), (b) wastewater discharged after anaerobic digestion (anaerobically

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digested distillery wastewater) and (c) Permeate of RO plant operation.

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2. Materials and Methods

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2.1. Measurement of parameters

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Table 1 gives the parameters measured and the instrument/procedure used for the measurement.

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2.2. Sophisticated instrument analysis

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The wastewater received from distillery at different stages was solar dried. The solid sample was

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prepared as a fine powder using mortar and pestle. Thermo gravimetric analyzer (TGA) and

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Differential Scanning Calorimeter (DSC) were used for thermal analysis of solid samples. The

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proximate composition of the distillery waste was obtained through TGA and the quantum of

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energy required for the treatment was understood using DSC and TGA kinetic analysis. FT-MIR

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studies were conducted to find the major functional groups present in the distillery wastewater.

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CHN analysis was carried out to find the percentage of carbon, hydrogen and nitrogen present in

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the distillery wastewater sample. Table 2 describes the instrumentation details.

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2.3. Process details

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The work was carried out at M/s Trichy Distilleries & Chemicals Limited (M/S TDCL) located

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at Tiruchirappalli, Tamil Nadu, India. The distillery wastewater was treated through anaerobic

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digester, settling lagoons (SP2A and SP2B), RO plant and biocomposting. The scheme of the

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treatment was shown in the horizontal flowchart. 1

SP2A

2

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Digester 1

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Distillery wastewater (RSW)

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Digester 2

SP2B

RO Plant

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The ETP was observed for a period of six months.

The critical parameters of distillery

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wastewater were measured at untreated stage and after anaerobic digestion for a period of 30 d.

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RO plant characteristics were also monitored and measured for 23 d excluding the days of

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cleaning and maintenance. The variations in the parameters in every unit operation of ETP also

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monitored and measured for finding the operation efficiency and stability. The instrumental

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analysis was carried out at solid testing and analysis laboratory (ISO 9001:2008 certified) and

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algae biotechnology laboratory of DEE, National Institute of Technology, Tiruchirappalli, Tamil

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Nadu, India.

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2.3.1. Anaerobic digestion

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The anaerobic biomethanation system was a specially designed mixed tank reactor (MTR) called

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bioreactor at M/s TDCL, to convert organic matter into useful energy in the form of biogas. The

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biological process of conversion was taken place at mesophilic temperature range in a controlled

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atmosphere ensuring maximum conversion efficiency and production of biogas. The process of

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bacterial digestion of distillery wastewater was explained by Sankaran et al. (2014a). The

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wastewater before entering into the reactor was mixed with the active sludge recycled from the

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bottom of parallel plate clarifier in the header located on top of the digester. The sludge recycle

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flow rate was measured by flow meter. By pass arrangement was provided for the operation

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simplicity and maintenance of the flow meter. Agitators, using scientifically designed mixing

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system and further enhanced by gas production, did mixing in the reactor. The mixing system

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had two top entry agitators and four side entry agitators for both the reactors (Digester 1 and 2).

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Feed point in the reactor was located just beneath the blades of the top entry agitators in a

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specially designed draft tube. The top entry agitator pushed the influent through the draft tube

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towards the bottom. The draft tube had slots at the bottom, from where the mixed feed was

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coming out and mixed with the entire biomass in the reactor.

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microorganisms to reach fresh food (wastewater) in favorable living condition and convert

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organic matter into methane and carbon dioxide. The treated wastewater (BMSW) along with

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some biomass was flowing out from the overflow, while the biogas flew to the free zone at the

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top of the reactor. From this free zone, gas was collected and sent to the gasholder. Various

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sample points were provided on both the bioreactors (Digester 1 and 2) to collect the sample for

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laboratory analysis. Drain points were also provided to drain the excess sludge from bioreactor

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as and when required.

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Bioreactor was designed for 17 to 18 d of hydraulic retention time, which was required for

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achieving designed parameters while reducing the effects of shock loads and making the process

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study. The digested wastewater (BMSW) from the bioreactors flew to the parallel plate clarifiers

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via degassing vessels where the entrapped gases in the digested wastewater (BMSW) were

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released. Sludge in the BMSW which was going to parallel plate clarifier was settled and

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recycled back to the bioreactors to increase solid retention time. The sludge was recycled by

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sludge recycle pumps. Excess biomass and sludge were removed from the bottom of bioreactor

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regularly. The mixed feed pH was adjusted to 6.5-7.0 by recycling part of the treated wastewater

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(BMSW) from the bottom of both parallel plate clarifiers with the help of sludge recycle pumps.

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The biogas produced in both the bioreactors (digester 1 and 2) was collected in the respective top

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dome. From the dome, the gas flew to the gasholder via foam traps with water spraying system

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and sediment traps. From traps with water spraying system, removed moisture as carried over by

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the gas and also removed partial H2S in the gas. The gasholder acted as intermediate gas storage

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and pressure control device. The biogas was transferred to power unit for the generation of

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electricity.

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2.3.2. RO process

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Rochem Plate Tube (PT) membrane system was adopted as RO system at M/S TDCL. This

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system did not require high level pretreatment to prevent fouling and scaling at industrial scale.

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Also, it was relatively less expensive compared to traditional membrane systems such as spiral-

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wound, hollow fine fiber or tubular modules. The RO system consists of 3 stages of operation.

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The permeate at each stage was collected and recycled to storage tank for reuse. The reject from

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each stage was fed to the next stage. The number of stages operated at any instant was decided

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based on the level of pollution load available after anaerobic digestion. The anaerobically

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digested distillery wastewater was pumped into the PT system by the pre filter booster pump at

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the inlet of the filter pump. The effluent water was initially filtered by the sand filter and

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cartridge filter to remove the foreign materials. The filtered water was then pressurized to 50 –

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60 bar (normal operating pressure) by the high pressure pump. The operating pressure of 40 bar

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was maintained for treating the condensates by reverse osmosis in beet based distilleries (Morin-

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Couallier et al., 2008). The water was then passed over the membrane cushions in the PT

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modules. The high pressure was regulated by the servo motor control valve. The filter pump

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further ensured that the sufficient pressure was maintained in the system for normal operation.

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About 62-64% of the input was collected as water across the pure water side.

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concentrated wastewater (reject) from the last stage of RO system, was mixed with pressmud and

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marketed as a biocompost. The entire operation of the RO plant was automatically controlled by

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a stored programme in the microprocessor fitted in the control panel. The control panel housed

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all the electronics and the electrical circuits.

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2.4. Analysis of kinetic parameters

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Thermo gravimetric and derivative thermo gravimetric curves for raw wastewater (RSW) and

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anaerobically digested wastewater (BMSW) were analyzed for the determination of kinetic

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parameters. The method followed by Naveen and Premalatha, (2016, 2014) holds good for the

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analysis.

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Arrhenius decomposition equation, which is

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= .  / 

The residual

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The dependence of reaction constant with temperature could be obtained from

(1)

-1

-1

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where, k – rate constant (s ); A – pre exponential or frequency factor (s ) which was assumed to

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be independent of temperature; R- universal gas constant (8.314 J/mol/K) and T – temperature

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(K).

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Kinetics of vitalization reaction could be written as (Jeguirim and Trouve, 2009)

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=


 

  





(2)

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where, w – weight of the sample (mg) at time ‘t’; w0 – initial weight of the sample (mg); wf –

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final weight of the sample (mg);

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and n- order of the reaction.

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After substituting k-value from Eq. (1) into Eq. (2) and taking natural logarithm for both sides,

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the Eq. (2) had become

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ln 

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Eq. (3) could resemble the linear form of the equation

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! = " + #$ + %&

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where, Y = ln 

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The graph was plotted between Y vs X to find the kinetic parameters.

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2.5. Statistical analysis

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Microsoft excel spreadsheet 2013 and Origin 7.0 were used as tools for data and graphical

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analysis. TGA and DSC analysis were carried out using ‘pyris’ software. FT-MIR curve was

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plotted using ‘spectrum’ software. Linear regression analysis for the determination of kinetics

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parameters was carried out using LINEST function of Microsoft Excel.

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3. Results and Discussion

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To identify the position of retrofitting the ETP operation with microalgae treatment step, the

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wastewater characteristics at different stages were monitored and measured. ETP plant was

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studied horizontally and vertically. Treatment of wastewater through the ETP operation and

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comparison of wastewater before and after anaerobic digestion were carried out as horizontal

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study. Vertical study refers to, the variations of parameters with reference to time for different

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stages of ETP operation. Vertical study provides an idea of upper and lower limits of wastewater

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characteristics over a period of month (30 d). Results of TGA, DSC and CHN provide the

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insight of wastewater available at different stages.

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3.1. Treatment studies – Horizontal study 1

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The alcohol production in the distillery was 40 kL/d and so the production of wastewater was

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around 500-600 kL/d. The wastewater was treated through two parallel anaerobic digesters and

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a series of settling lagoon (SP2A & SP2B) followed by RO process. Digester 1 and 2 had the

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capacity of 22-25 m3/h.

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3.1.1. Treatment study through anaerobic digestion and settling lagoon

 











; C = ln (A); m =  ; X = ; D = n; Z =  



 

  

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The study was mentioned as route 1 (RSW
Digester 1
SP2A
SP2B) and route 2

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(RSW
Digester 2
SP2A
SP2B) of ETP scheme. The pollution load reduction (COD) in

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both the route was up to 65-70% which was further fed to RO process. Fig. 2 shows the changes

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in the parameters such as pH, conductivity, BOD, inorganic TDS, TDS, TSS and COD on an

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average scale across the treatment stages of ETP operation. During treatment, the pH was greatly

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increased up to 70-75% (route 1/route2) due to the bacterial growth in the anaerobic digester

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(Mohana et al., 2013). Further, it was increased slightly (5-7%) in the settling lagoon because of

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TSS settling (Fig. 2 (a1 & a2)). Conductivity was changed in line with the treatment process up

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to 15% due to the change in the concentration of inorganic substances in the wastewater (Fig. 2

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(b1 & b2)). BOD and COD were reduced maximum in the two parallel digester 1 & 2 due to the

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conversion of organic pollution load to methane (Fig. 2 (c1 & c2; g1& g2)). TDS was reduced

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greatly in the digester (60-65%) due to the organic pollution load conversion to biogas by

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bacteria (Fig. 2 (e1 & e2)). However, inorganic TDS was increased slightly through the

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treatment process as it was not consumed by bacteria in the digester (Fig. 2 (d1 & d2)). TSS

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increased greatly in the digester because of bacteria in suspension and the same was reduced in

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the settling lagoons by gravity settling due to the inability of anaerobic bacteria survival in the

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open atmosphere (Fig. 2 (f1 & f2)). It was observed from the treatment studies that major

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reduction in pollution load of wastewater was obtained in anaerobic digester. Settling lagoons

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showed the similar characteristics as that of wastewater obtained after anaerobic digestion except

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the concentration of TSS. It was further observed that the wastewater after anaerobic digestion

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contain reduced organic pollution load and the same inorganic pollution load as compared to raw

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distillery wastewater. The pH was shifted between 4 and 8 through the treatment process. This

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favored the possible coupling of microalgae after anaerobic digestion. Further, it insisted the

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detailed comparison between raw and anaerobically treated distillery wastewater was necessary

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to identify the key inorganic substances present in the anaerobically digested wastewater

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(BMSW).

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3.1.2. Treatment study in RO plant

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Reverse Osmosis (RO) was coupled as the final treatment process to recycle the clean water

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from the wastewater for the usage. Mavrov and Belieres, 2000 used RO process to reduce water

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consumption and wastewater quantities by recycling the water in food industry. RO permeate

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had the characteristics such as pH-7.3; conductivity 1241 µS.cm-1; inorganic TDS 819 ppm;

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organic TDS 940 ppm and COD 93 ppm (average values). However, the RO system suffers due

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to the pollution load of influent which was anaerobically digested wastewater (BMSW) resulting

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high maintenance cost. The presence of inorganic substances affects the RO process. So, it

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necessitates the reduction of inorganic pollution load prior to RO process which could be carried

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out through coupling phycoremediation after anaerobic digestion.

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3.2. Comparison studies – Horizontal study 2

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3.2.1. Physicochemical characterization of raw distillery wastewater (RSW) and anaerobically

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digested distillery wastewater (BMSW)

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The characteristics such as pH, COD, BOD, TDS and TSS decide the choice of treatment

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technology to be adopted for any wastewater. Table 3(a) shows the required characteristics for

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the design of wastewater treatment scheme. It could be visualized from the table that the ratio of

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BOD/COD was varying between 0.28 – 0.3. Sankaran et al. (2014a) stated that biological

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treatment was found good when the BOD/COD ratio was greater than 0.25. Anaerobic digestion

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although it was conventional, but still was the best in attacking the raw distillery wastewater

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(RSW). The characteristics of RSW indicated that the organic loading of wastewater was high.

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When it was treated under anaerobic digestion it could produce biogas through which the major

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fraction (more than 80%) of power requirement was met.

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Table 3(b) shows the reduction in organic pollution load achieved through anaerobic digestion.

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The reduction of TDS, COD and BOD were 60%, 68% and 72%. The results were comparable

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with Moletta, (2005). The reduction in TDS and BOD indicated that the organic load available

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in dissolved form was utilized by the microorganisms to produce biogas. Methanogenic bacterial

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group takes only organic compound as its nutrients (Weiland, 2010). However, the increase

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(79.5%) in TSS was observed. It was majorly due to the presence of high inorganic salt

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concentration in distillery wastewater and the microorganisms available in the treated

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wastewater. However, sulphates were also reduced by 68% through anaerobic digestion. The

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behavior of sulphate reducing bacteria in acidogenic phase of anaerobic digestion was studied by

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Mizuno et al., 1998. Further, the total carbon after anaerobic digestion was 22000 – 23000 ppm

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out of which 17000 – 18000 ppm was available as organic carbon and 5000 – 6000 ppm as

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inorganic carbon.

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Table 3(b) further indicates that the inorganic substances such as bicarbonate, potassium,

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chloride and sulphate were majorly contributing for the pollution load in BMSW. It ascertained

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that the coupling of phycoremediation at this stage was highly preferred. Microalgae could take

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the inorganic substances as its nutrients. BMSW treatment study with Oscillatoria sp. (BDU

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142191) was resulted the reduction of COD up to 55% and total carbon reduction up to 40%

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(Suriya Narayanan et al., 2014; Sankaran et al., 2014b). The calorific value of the treated algae

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biomass was between 15-18 MJ/kg and could generate biogas through secondary anaerobic

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digestion. The phycoremediation study was carried out after removing the TSS in the BMSW.

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However, the removal of TSS might not require for large scale treatment study since it majorly

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consists of bacterial suspension which found dead in aerobic treatment and so anaerobic bacteria

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could not interact with the microalgae.

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3.2.2. Characterization using analytical instruments

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TGA analysis

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TGA was carried out for finding the thermal characteristics of RSW and BMSW, following the

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standards used for TGA analysis of coal (Fig. 3) (ASTM methods). The samples were heated

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from 30oC to 105oC at 5oC/min and held for 30 minutes at 105oC in nitrogen atmosphere to find

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the moisture content. It was 8.6% for RSW and 8.33% for BMSW. Samples were further heated

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from 105oC to 900oC at a maximum rate of 50oC/min in nitrogen atmosphere for the

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quantification of volatile compounds. Weight loss was maximum at this stage because of release

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of numerous volatile compounds. Li et al. (2008) observed the release of volatiles when sewage

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sludge was heated from the room temperature up to 500°C at a heating rate of 2°C/min. From

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the derivative TGA curve of RSW, it was observed that while the temperature ranges between

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360oC and 380oC, the weight loss was relatively higher and it was approximately 32.5%. The

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weight loss was 26.6% between the temperature 380oC and 900oC. Yang and Jiang, (2009)

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reported that the maximum weight loss was obtained between 200oC and 530oC in the sewage

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sludge when heated using derivative thermo gravimetry. They further concluded that the sludge

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contains higher level of volatile substances and lower level of salts. In case of BMSW, from the

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derivative TGA curve, it was observed that the weight loss due to volatiles was comparatively

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lower than the RSW. 21.2% weight loss was observed in the temperature range of 420oC -

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440oC. The decreased weight loss indicated the conversion of volatiles into biogas during

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anaerobic digestion process. The temperature range of volatiles were shifted, indicating the

366

complexity of volatiles after anaerobic digestion. The weight loss was 22% at the temperature

367

range of 440oC - 900oC. This difference in weight loss was also due to the conversion of volatiles

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in the given temperature range to biogas during anaerobic digestion. Further, the samples were

369

held at 900oC for 7 minutes after switching gas to oxygen atmosphere for the fixed carbon

370

analysis. It was approximately 10% for RSW and 15% for BMSW. Samples were then held for

371

30 min at 900oC. The ash content was less than 22% for RSW & BMSW. Further, it was

372

concluded that the fixed carbon of BMSW could be utilized for the growth of microalgae and the

373

inorganic content (ash) could satisfy the nutrient requirement of algae.

374

For finding the thermal decomposition kinetics of wastewater, a constant rate of heating at

375

10oC/min from 30oC to 900oC in nitrogen atmosphere was carried out for RSW & BMSW. It

376

was found that thermal degradation occurs in a linear fashion for both the stages of wastewater

377

and approached zero order reaction kinetics (Fig. 4). Naveen and Premalatha, (2014) were also

378

observed zero order kinetics for the thermal degradation of distillery wastewater. The kinetic

379

analysis was carried out for the temperature region at which maximum weight loss was occurred.

380

In RSW, the maximum weight loss was occurred between 253.98oC - 328.07oC and between

381

677.68oC – 737.86oC (Fig. 4a). While in BMSW, the maximum weight loss was occurred only

382

between 231.04oC and 386.44oC. The determined kinetic parameters were summarized in Table

383

4.

384

wastewater was higher in RSW compared to BMSW. Other kinetic parameters like frequency

385

factor (A) and peak temperature (Table 4) were also favor the coupling of microalgae treatment

386

step after anaerobic digestion.

387

DSC analysis

388

DSC was carried out for calorimetric analysis of RSW and BMSW. DSC curve was obtained for

389

the temperature interval between -30oC and 445oC at the rate of 10oC/min. For RSW, a very

390

small (156.46oC – 158.98oC) and a large (160.98oC – 169.65oC) adjacent endothermic peaks

391

were observed which were due to vaporization and decomposition. DSC curve also showed the

392

endothermic reaction peak values at 157.19oC and 162.97oC.

393

interpreted as 2.471 mW, 13.172 mW and 33.671 mJ, 517.600 mJ respectively. From those

394

values, enthalpies were calculated and they were 10.329 J/g and 158.773 J/g (Fig. 5(a)). In case

395

of BMSW, a very small (144.61oC – 148.67oC) and a large (162.43oC – 169.43oC) adjacent

396

endothermic peaks were observed which were also due to vaporization and decomposition. A

397

small exothermic peak was also (250.06oC – 259.92oC) observed and it was due to the

398

decomposition again.

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Peak height and area were

In other words, the rate of decomposition and vaporization were 13

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maximum between the temperature 162.43oC and 169.43oC. DSC curve further showed the

400

endothermic reaction peak values at 146.42oC and 163.99oC and exothermic reaction peak value

401

at 255.25oC. Peak height and area were interpreted as 2.185 mW, 14.917 mW, -1.048 mW and

402

37.173 mJ, 454.941 mJ, -30.303 mJ respectively (Fig. 5(b)). From those values, enthalpies were

403

calculated and they were 10.184 J/g, 124.641 J/g and -8.302 J/g (Fig. 5(b)). So, it was observed

404

that the energy required for the decomposition of wastewater compounds was relatively lower

405

for BMSW as compared to RSW, favoring the coupling of microalgae after anaerobic digestion.

406

Della Zassa et al., 2013 also calculated enthalpies for industrial wastewater sludge and observed

407

the effect of enthalpies associated with solid- transformation in the sludge.

408

FT-MIR analysis

409

RSW and BMSW were analyzed in FT-MIR spectroscopy between 4000 cm-1 and 400 cm-1 in

410

UATR mode for finding the stretches of major functional groups (Acharya et al., 2009). Fig. 6 (a

411

& b) shows the FT-MIR spectra of RSW and BMSW. FT-MIR spectra revealed the complex

412

chemical bond structure of wastewater that constitutes complicated organic and mineral

413

compounds. Hossain et al., 2011 observed the complex chemical bond structure through FT-MIR

414

for sludge and biochar samples. Fig. 6 (a & b) shows the broad band between 3500 and 3200

415

cm-1 which were due to O-H stretch of phenolic function group present in the wastewater

416

(Moussavi and Khosravi, 2010). Peaks observed between 1650 and 1580 cm-1, 1500 and 1400

417

cm-1 were due to N-H bend of amine and C-C stretch of aromatic functional group in the

418

wastewater (Zhao et al., 2010). Peaks at 1470 and 1450 cm-1, 1250 and 1020 cm-1 were due to

419

the presence of alkanes and aliphatic amines, indicating the bending and stretching vibrations of

420

C-H bond and C-N bond in the wastewater. The difference in the spectra of BMSW when

421

compared to RSW spectra was the magnitude of stretching vibrations between 1650 and 1020

422

cm-1 which could be observed through Fig. 6 (a & b). The relative low magnitude of peaks

423

observed in the BMSW was due to the reduction of organic pollution load as methane from the

424

wastewater. Figure 4b also shows the complex pattern between 500 and 400 cm-1, indicating the

425

presence of various inorganic compounds. So, it was concluded that coupling phycoremediation

426

was preferable after anaerobic digestion.

427

CHN analysis

428

Elemental analysis reported that the carbon value in BMSW was less as compared to RSW

429

(Table 5), favoring less complexity of coupling phycoremediation (Banerjee and Biswas, 2004).

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3.3. Variation studies – Vertical study

431

3.3.1. Variation studies – RSW, Digester (1&2), Settling lagoon (SP2A & SP2B)

432

This variation study aimed to reveal the upper and lower limit characteristics of distillery

433

wastewater in every unit operation of ETP plant. It would be an insight to check the withstanding

434

ability of phycoremediation proposed in order to improve the characteristics of wastewater.

435

Treatment of raw distillery wastewater (RSW) was processed through Digester1 or Digester 2,

436

settling lagoons (SP2A & SP2B) and RO processes. Measurement and analysis were carried out

437

for the period of 30 d to find the variations in physico-chemical characteristics of wastewater at

438

every ETP operations. The major parameters observed were pH, conductivity, total dissolved

439

solids (TDS), inorganic total dissolved solids (Inorganic TDS), chemical oxygen demand (COD)

440

and total suspended solids (TSS). Fig. 7 (a, b, c, d, e & f) shows the variation patterns of various

441

parameters measured over the period of 30 d with regard to individual unit operation. Fig. 7a

442

shows the pH variation pattern. The variation was between 4.16 and 4.52 for RSW, it was 7.59-

443

7.86 and 7.52–7.79 in the parallel digesters stage (1 and 2). At SP2A stage, it was 7.66-7.95 and

444

it was 7.8-8.04 at SP2B stage. Fig. 7b shows the conductivity variation in the stages of ETP

445

operation. The variations observed were 27-34 mS.cm-1, 30-35 mS.cm-1 or 27-35 mS.cm-1, 33-

446

36 mS.cm-1 and 34-36 mS.cm-1 at RSW, Digester 1 or Digester 2, SP2A and SP2B stages. The

447

variations in total dissolved solids (TDS) and inorganic total dissolved solids (ITDS) were shown

448

in Fig. 7 (c & d). The TDS variations were 93370-110120 ppm, 39490-44240 ppm or 38480-

449

45700 ppm, 46330-51960 ppm and 47150-51470 ppm at RSW, Digester 1 or Digester 2, SP2A

450

and SP2B stages (Fig. 7c).

451

19800-23100 ppm or 20460-23100 ppm, 23100-23760 ppm and 22440-23760 ppm across the

452

treatment stages (Fig. 7d). The COD variations were 93486-104030 ppm in RSW, 32208-36360

453

ppm or 32208-39390 ppm in the parallel digester 1 and 2, 32023-36144 ppm at SP2A stage and

454

30990-34360 ppm at SP2B stage (Fig.7e). Similarly, variations at every stage of ETP operation

455

also observed for the total suspended solids (TSS) parameter (Fig. 7f). The variations in the

456

parameters were due to the characteristics of wastewater at different treatment stages. The

457

characteristics of wastewater varied with time due to (a) variations in the quality of raw material

458

(molasses) used in the distillery (b) variations of plant load factor of distillery (c) variations in

459

the efficiency of ETP operation. The variations observed in the monitored parameters were

460

summarized in Table 6 for better understanding.

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Inorganic TDS variations were observed as 19800-22440 ppm,

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3.3.2. Variation study – RO process

462

The variations found in the various parameters of RO permeate over the period of 30 d

463

(excluding the days of cleaning and maintenance) were shown in Fig. 8 (a, b & c). The variation

464

in inorganic TDS and organic TDS were between 726-1128 ppm and 860-1198 ppm (Fig. 8a)

465

and the pH and conductivity variations were 6.95-7.44 and 1140-1710 µS.cm-1 (Fig. 8b). The

466

COD variation was observed to be 85-110 ppm in the RO permeate (Fig. 8c) and the total

467

suspended solids (TSS) were found as nil. The safety discharge characteristics of distillery

468

wastewater to the inland surface water were pH 5.5-9, COD 250 ppm and TSS 100 ppm

469

(Sankaran et al., 2015). The RO permeate characteristics were within the limit of safe discharge

470

and the RO permeate was recycled to the production unit to minimize the water foot print of

471

alcohol production in the distillery. RO reject was mixed with pressmud obtained from sugar

472

industry and used for bio composting and thus achieving zero liquid discharge by the distillery.

473

4. Conclusion

474

Raw distillery wastewater sample which was collected from M/s Trichy Distilleries & Chemicals

475

Ltd. (M/S TDCL), contains high concentration of degradable organic and inorganic compounds.

476

It was treated through anaerobic digestion, settling lagoon and RO process. The present

477

investigation revealed the overall treatment efficiency of ETP operation by distillery and the

478

variation study showed the upper and lower limits of wastewater characteristics in every stage of

479

operation. However, ETP suffers due to the pollution load across the stages of ETP operation.

480

Due to increase in the stringency of CPCB regulatory norms, it is wise to include a biological

481

treatment step to reduce the pollution load further and benefit the distillery through its

482

byproduct(s). Physico-chemical comparison studies showed the presence of various inorganic

483

compounds in the anaerobically digested wastewater (BMSW) which affect the RO process.

484

However, it was treated as nutrients by microalgae. Through the characterization of distillery

485

wastewater at different stages of treatment, it is proposed to retrofit the existing ETP with

486

microalgae treatment step after anaerobic digestion. Instrumental analysis using TGA, DSC and

487

CHN analyzer provided the insight of wastewater and favor the coupling of phycoremediation in

488

between anaerobic digestion and RO process to achieve zero liquid discharge (ZLD) by

489

distillery. Though the suitability and treatment result of phycoremediation of anaerobically

490

digested distillery wastewater was provided, it requires a detailed study with regard to strain

491

selection, acclimatization and design aspects.

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Acknowledgements

493

Authors acknowledge Science & Engineering Research Board (SERB) for the collaborative

494

research study with M/s Trichy Distilleries & Chemicals Ltd. (TDCL), Tiruchirappalli through

495

Prime Minister’s Fellowship for Doctoral Research managed by Confederation of Indian

496

Industry (CII). Authors also thank Dept. of Energy & Environment of NIT-T for the laboratory

497

facilities and the staff of M/s TDCL for the cooperation. Special thanks extended to Mr. Ram V.

498

Tyagarajan, Chairman & Managing Director, M/s Thiru Arooran Sugars Ltd., Thirumandangudi

499

for his suggestion and direction.

500

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Table 1 List of parameters and its protocol/instrument used for the analysis S.No.

Instrument/Procedure Henna Handheld pH meter Hach conductivity probe

4.

COD measurement

Merck spectroquant TR 420 and pharo 300 spectrophotometer

5.

BOD measurement

Lovibond Oxidirect

6.

Measurement of chemicals like sulphate, ammoniacal nitrogen, chloride, phenol, phosphate, total nitrogen, hardness, nitrate, fluoride, sodium, iron, oil & grease, potassium, silica, bicarbonate

RI PT

pH Conductivity Total Solids (TS) Total Dissolved Solids (TDS) Total Suspended Solids (TSS)

SC

Weight measurement

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APHA Standard, 21st Edition, 2005

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1. 2. 3.

Parameters

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Table 2 List of analytical instruments and the procedure followed for the sample analysis Make/Model

Procedure followed

1.

Thermo Gravimetric Analyzer

TGA 4000/PerkinElmer

Heated from ambient to 9000C with the heating rate as per ASTM procedure used for coal with nitrogen and oxygen switching.

2.

Differential Scanning Calorimeter

DSC 6000/PerkinElmer

Heated from -300C to 4450C with the heating rate of 100C/min in nitrogen atmosphere.

3.

CHN Analyzer

CHNS/O 2400/PerkinElmer

CHN analysis using combustion and reduction technique with nitrogen, oxygen and helium gases.

4.

FT-MIR Spectrophotometer

Spectrum Two/PerkinElmer

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Instrument

AC C

S. No.

Wave number range 4000– 400 cm-1

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Table 3(a) Major composition of raw distillery wastewater (RSW) - M/S Trichy Distilleries & Chemicals Ltd. Concentration range Parameters

Concentration range

(ppm)

(ppm)

RI PT

Parameters

Dark brown

Acidity

5200 – 8000

Odor

Sugar smell

BOD

25000 – 35000

Temperature

80-900C

Sulphate

13100 – 13800

pH

4-4.6

Ammoniacal nitrogen

800 – 1100

Conductivity

26-31 mS.cm-1

Chlorides

Inorganic TDS

17160 – 20460

TDS

85000 – 110000

TSS

4500 – 7000

COD

85000 – 110000

Table 3(b)

M AN U

4500 – 8400

Phenols

3000 – 4000

Phosphate

1500 – 2200

Total Nitrogen

4200 – 4800

Total carbon

44000 - 46000

Total inorganic 4000-6000 carbon

TE D

Total organic 40000-42000 carbon

SC

Color

Major composition of anaerobically digested distillery wastewater (BMSW) – M/S Trichy

Parameters

EP

Distilleries & Chemicals Ltd.

Concentration

range Parameters

Color

AC C

(ppm)

Temperature

Dark Brown

Concentration range (ppm)

Ammoniacal

1000 – 1050

nitrogen 0

35-40 C

Dissolved

350 - 360

Phosphate

pH Conductivity

7.5 – 8.0 31-36 mS.cm-1

Chlorides Sulphates

8500 – 8550 4000 – 4500

Turbidity (NTU)

40

Fluorides

5-6

TDS

35000 – 45000

Nitrates

350 - 400

ACCEPTED MANUSCRIPT

22000 – 34000

Sodium

250 - 270

COD

25000 – 40000

Total Iron

10

Alkalinity

17000 – 24000

Oil & Grease

30 - 32

BOD

7000 – 10000

Potassium

12500 – 12800

as 3100 – 3200

Total Silica

60 – 62

as 600 - 650

Reactive Silica

50 - 52

Bicarbonate

12800 – 12850

Total

hardness

CaCO3 Calcium

hardness

CaCO3

SC

Magnesium hardness as 2500 – 2600

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TSS

AC C

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MgCO3

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Table 4 Determination of kinetic parameters using Thermo gravimetric analyzer (TGA)

159.36 47.36

25.20

M AN U

0.985

7

14.83 x 10

0.993

3

0.994

9.14 x 10

SC

290.20

19.17

R2

RI PT

284.69 708.84

231.04 - 386.44

A (min-1)

Peak temperature E (KJ/mol) (0C)

TE D

BMSW

677.68 – 737.86

EP

RSW

Temperature region at which maximum weight loss occurred (0C) 253.98 – 328.07

AC C

Sample

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Table 5 Elemental composition of distillery wastewater (RDW) Anaerobically digested distillery wastewater (BMSW) elemental composition Carbon – 28.09% Nitrogen – 4.15%

Oxygen – 2.61%

Oxygen – 2.65%

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Nitrogen – 5.20%

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Raw distillery wastewater elemental composition Carbon -30.59%

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Table 6 Responses for the measurement of various parameters at stages of effluent treatment plant (ETP) Conductivity (mS.cm-1)

TDS (ppm)

Inorganic TDS (ppm)

COD (ppm)

TSS (ppm)

Raw wastewater (RSW)

4.16-4.52

27-34

93370-110120

19800-22440

93486-104030

3940-6490

Digester 1

7.59-7.86

30-35

39490-44240

19800-23100

32208-36360

15620-27970

Digester 2

7.52-7.79

27-35

38480-45700

20460-23100

32208-39390

*

SP2A

7.66-7.95

33-36

46330-51960

23100-23760

32023-36144

1710-4380*

SP2B

7.8-8.04

34-36

47150-51470

22440-23760

30990-34360

1100-1740

M AN U

EP

TE D

Extreme case

AC C

*

RI PT

pH

SC

Parameters Treatment stages

9000-32270

M AN U

SC

RI PT

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AC C

EP

TE D

Fig. 1. ETP Flow Chart - Trichy Distilleries & Chemicals Limited (TDCL), Tiruchirappalli, Tamil Nadu, India

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8.5 8.0

RI PT

7.5

pH M easurem ent

6.5 6.0 5.5

SC

pH Value

7.0

5.0 4.5

M AN U

4.0 R SW

D igester 1

S P 2A

S P 2B

ET P O perations

TE D

(a1)

8.5 8.0 7.5

6.0

EP

6.5

pH Measurement

AC C

pH Values

7.0

5.5 5.0 4.5 4.0

RSW

Digester 2

SP2A

ETP Operations

(a2)

SP2B

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40 39 38 37

35

RI PT

Conductivity (mS/cm)

36

34 33 32 31

C o n d u ctiv ity M e a s u re m e n t

30 29

SC

28 27 26

M AN U

25 RSW

D ig e s te r 1

S P2A

SP2B

E T P O p e ra tio n s

39 38 37

35 34 33 32

AC C

Conductivity (mS/cm)

36

EP

40

TE D

(b1)

C o n d u c tiv ity M e a s u re m e n t

31 30 29 28 27 26 25

RSW

D ig e s te r 2

S P 2A

E T P O p e ra tio n s

(b2)

SP2B

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30000 27500 25000

20000 17500

BOD Measurement

15000 12500 10000 7500 5000 Digester 2

SP2A

SP2B

M AN U

RSW

RI PT

22500

SC

Biological Oxygen Demand (BOD) in ppm

32500

ETP Operations

27 50 0 25 00 0 22 50 0 20 00 0 17 50 0

EP

30 00 0

B O D M e a su re m e n t

AC C

Biological Oxygen Demand (BOD) in ppm

32 50 0

TE D

(c1)

15 00 0 12 50 0 10 00 0 7 50 0 5 00 0

RSW

D ig es ter 1

SP2A

E T P O p e ra tio n s

(c2)

S P 2B

RI PT

25000 24500 24000 23500 23000 22500 22000 21500 21000 20500 20000 19500 19000 18500 18000 17500 17000 16500 16000 15500 15000

SC

In organ ic T D S M e asurem ent

RSW

M AN U

Inorganic Total Dissolved Solids (ppm)

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D igester 1

S P 2A

S P 2B

E T P O pe rations

TE D EP

25000 24500 24000 23500 23000 22500 22000 21500 21000 20500 20000 19500 19000 18500 18000 17500 17000 16500 16000 15500 15000

AC C

Inorganic Total Dissolved Solids (ppm)

(d1)

RSW

In o r g a n ic T D S M e a s u r e m e n t

D ig e s te r 2

SP 2A

E T P O p e r a tio n s

SP 2B

ACCEPTED MANUSCRIPT (d2)

120000

RI PT

80000

T o ta l D is s o lv e d S o lid s M e a s u r e m e n t

SC

60000

40000

20000

0 RSW

M AN U

Total Dissolved Solids (ppm)

100000

D ig e s te r 1

SP2A

SP2B

E T P O p e ra tio n s

120000

TE D

(e1)

EP

40

100000

AN

80000

AC C

Total Dissolved Solids (ppm)

an

Total Dissolved Solids Measurement

60000

40000

ap AP 42

AQ aq 43

SP2A

SP2B

ao AO 41

20000

0 RSW

Digester 2

ETP Operations

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32500 30000

RI PT

25000 22500

T o ta l S u s p e n d e d S o lid s M e a s u rm e n t

20000 17500 15000 12500 10000

SC

Total Suspended Solids (ppm)

27500

7500 5000

0 RSW

M AN U

2500 D ig e s te r 1

SP 2A

SP2B

E T P O p e ra tio n s

32500

27500 25000 22500 20000 17500

T o ta l S u s p e n d e d S o lid s M e a s u re m e n t

AC C

Total Suspended Solids (ppm)

30000

EP

35000

TE D

(f1)

15000 12500 10000 7500 5000 2500

0 RSW

D ig e s te r 2

SP2A

E T P O p e r a tio n s

(f2)

SP2B

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110000 100000 95000 90000 85000

RI PT

80000

C O D M e a s u re m e n t

75000 70000 65000 60000 55000 50000 45000

SC

Chemical Oxygen Demand (COD) in ppm

105000

40000 35000 30000 D ig e s te r 1

SP 2A

SP 2B

M AN U

RSW

E T P O p e ra tio n s

100000 95000 90000 85000 80000 75000 70000 65000

C O D M e a s u re m e n t

60000

AC C

Chemical Oxygen Demand (COD) in ppm

105000

EP

110000

TE D

(g1)

55000 50000 45000 40000 35000 30000

RSW

D ig e s te r 2

SP 2A

E T P O p e ra tio n s

(g2)

S P2B

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AC C

EP

TE D

(a)

M AN U

SC

RI PT

Fig. 2. Reduction in parameters during wastewater treatment through (Route 1) RSW-Digester 1SP2A-SP2B (a1-g1) and (Route 2) RSW-Digester 2-SP2A-SP2B (a2-g2)

(b) Fig. 3. Thermo gravimetric analysis (TGA) of (a) raw distillery wastewater (RSW) (b) anaerobically digested distillery wastewater (BMSW)

M AN U

SC

RI PT

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AC C

EP

TE D

(a)

(b) Fig. 4. TGA analysis of (a) RSW (b) BMSW to identify the thermal kinetics

AC C

EP

TE D

(a)

M AN U

SC

RI PT

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(b) Fig. 5. Differential Scanning Calorimetric (DSC) analysis of (a) raw distillery wastewater (RSW) (b) anaerobically digested distillery wastewater (BMSW) for finding enthalpy and reaction that occurred in it

AC C

EP

TE D

M AN U

(a)

SC

RI PT

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(b)

Fig. 6. FT-MIR analysis of (a) RSW (b) BMSW

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RSW

Digester 1

SP2A

SP2B

Digester 2

8.0 7.5

RI PT

pH Value

7.0 6.5 6.0 5.5

SC

5.0

4.0 0

5

M AN U

4.5

10

15

Days

AC C

EP

TE D

(a)

(b)

20

25

30

M AN U

SC

RI PT

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(c)

RSW

SP2B

Digester 2

EP

22000

20000

SP2A

AC C

Inorganic TDS (ppm)

23000

21000

Digester 1

TE D

24000

19000

18000

17000

0

5

10

15

Days

(d)

20

25

30

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

(e)

RSW

30000

20000

AC C

10000

SP2A

SP2B

Digester 2

EP

TSS (ppm)

25000

15000

Digester 1

TE D

35000

5000

0

0

5

10

15

20

25

30

Days

(f) Fig. 7. Variations of parameters over 30 d of operation of effluent treatment plant (TDCL) (a) pH variations (b) conductivity variations (c) Total dissolved solids (TDS) variations (d) Inorganic total dissolved solids (ITDS) variations (e) Chemical oxygen demand (COD) variations (f) Total suspended solids (TSS) variations

(a) Days Vs pH

Days Vs Conductivity

1800 1700

7.8

7.6

1500 1400

EP

7.4

1600

7.2

AC C

7.0

1300 1200 1100

6.8

0

2

4

6

8

10

12

14

Days

(b)

16

18

20

22

24

Conductivity (micro S/cm)

TE D

8.0

pH value

M AN U

SC

RI PT

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105

COD (ppm)

RI PT

100

95

90

85 0

2

4

6

8

10

12

16

18

M AN U

Days

14

SC

Chemical Oxygen Demand (ppm)

110

20

22

24

(c)

AC C

EP

TE D

Fig. 8. Reverse Osmosis permeate characteristics - Variations in parameters in RO process (a) Inorganic & Organic total dissolved solids (TDS) variations (b) pH & Conductivity variations (C) Chemical oxygen demand (COD) variations

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Research Highlights

RI PT

SC M AN U TE D

  

EP

 

Revealing the physico-chemical characteristics of wastewater at every stage of ETP operation Thermal characterization of wastewater using TGA & DSC Observation of major functional groups present in RSW & BMSW using FT-MIR spectroscopy Visualizing the variations of monitoring parameters in the individual operation Favoring conditions to include microalgae treatment step, is after anaerobic digestion Achieving zero liquid discharge through new clean ETP strategy.

AC C

