|
 
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| REVIEW ARTICLE |
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| Year : 2017 | Volume
: 2
| Issue : 2 | Page : 27-36 |
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Characterization and treatment of wastewater from food processing industry: A review
Deborah Olubunmi Aderibigbe, Abdur-Rahim Adebisi Giwa, Isah Adewale Bello
Department of Pure and Applied Chemistry, Ladoke Akintola University of Technology, Ogbomosho, Oyo State, Nigeria
| Date of Submission | 26-Jul-2017 |
| Date of Acceptance | 15-Jul-2018 |
| Date of Web Publication | 30-Aug-2018 |
Correspondence Address:
Dr. Abdur-Rahim Adebisi Giwa
Department of Pure and Applied Chemistry, Ladoke Akintola University of Technology, P.M.B. 4000, Ogbomoso, Oyo State
Nigeria
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/ijas.ijas_11_17
The food processing industry contributes to economic growth and makes food more available. Wastewaters discharged from food industries need to be characterized often for their compliance to standards by regulatory authorities. In order to reduce environmental pollution, these industries use different treatment methods to treat their wastewater. Characterization of wastewater helps in developing various treatment methods among which are biological techniques, advanced oxidation process (AOP), and more recently adsorption. The biological treatment and AOP have undergone several investigations in the past few years and have advantages ranging from low operation cost to no waste product but not as efficient as adsorption which has low operation cost and high efficiency. This review focuses on works been done on characterization as well as the treatment of wastewater from food processing industry.
Keywords: Adsorption, advanced oxidation process, biological, economic
How to cite this article:
Aderibigbe DO, Giwa ARA, Bello IA. Characterization and treatment of wastewater from food processing industry: A review. Imam J Appl Sci 2017;2:27-36 |
How to cite this URL:
Aderibigbe DO, Giwa ARA, Bello IA. Characterization and treatment of wastewater from food processing industry: A review. Imam J Appl Sci [serial online] 2017 [cited 2023 May 31];2:27-36. Available from: https://www.e-ijas.org/text.asp?2017/2/2/27/240161 |
| Introduction | |  |
Water is a resource as well as a life source because of its importance for life and its usefulness for several purposes such as in agricultural, industrial, domestic, recreation, and environmental activities. This also makes it a precious commodity.[39],[90] Industries are established to manufacture products targeted at meeting the demand of increasing population in developing countries. These industries are the backbone of development of a country. However, as they produce useful products, they also generate wastes and potentially harmful by-products which leads to pollution of the environment.[2],[23],[97],[99] Pollution can be as a result of contamination of air, soil, and water, but the common one with processing industries is water. Wastewaters released from industries are associated with diseases which may be linked to the current shorter life expectancy in the developing countries.[104],[105] In addition, aquatic organisms are adversely affected when untreated or poorly treated industrial wastewaters are discharged into water bodies.
Industrial wastewater contains sanitary waste, process wastes from manufacturing sections, wash water from equipment sections, and relatively uncontaminated water from heating and cooling operations. Naturally, all wastewaters contain both organic and inorganic compounds which account for their usual high dissolved solids and biochemical oxygen demand (BOD).[28],[63],[75],[109] Food processing industries often produce to increase accessibility to more edible products and can process raw materials such as fruit, vegetables, and milk. They require large amount of water for each batch of production. Water is used throughout operations such as production, cleaning, sanitizing, materials transport, and cooling.
Several methods which include physical, chemical, and biological processes like coagulation/flocculation process have been used for the treatment of these wastewaters,[5],[75],[90] biological photooxidation.[13] However, the latest and the widely used one is adsorption using activated carbon. There are limited studies on characterization-assisted adsorption methods, hence the need for this review to give a detailed account of works available on the subject matter.
| Characterization of Wastewater from Food Processing Industries | | |
Food processing industries consist of a variety of industries such as dairy, snacks, sweets, beverages, and distillery. Wastewaters from these industries come from different plant operations such as production, cleaning, sanitizing, cooling, and materials transport.[3]
However, the constituents of these wastewaters are biodegradable due to high organic substances and may also be nontoxic. This eventually results in high concentrations of BOD, chemical oxygen demand (COD), and suspended solids (SSs).[18] The characteristics of wastewater play a major role in selecting the type of treatment to be carried out on it.[19] Typical characteristics of a food processing industry are shown in [Table 1].[97],[99],[102]
Schmidt and Ahring[92] characterized and treated wastewater from a multiproduct food processing company (fruits and vegetables). They observed that wastewater from peas processing plants had COD value of 5.8 mg/L, total solid (TS) of 4.5 mg/L, and volatile solid (VS) of 3.8 mg/L while that of carrot has COD of 7.7 mg/L, TS of 11 mg/L, and VS of 6 mg/L. Furthermore, celery processing plant wastewater is characterized by COD of 1.4 mg/L, TS of 1.7 mg/L, and VS of 1.2 mg/L while that of leek has COD of 4.1 mg/L, TS of 2.1 mg/L, and VS of 1.6 mg/L. Characterization of wastewaters from beverage and vegetable industries was also carried out by Tariq et al.[97] They found out that the wastewater from the vegetable ghee had a pH of 7.80, electrical conductivity (EC) of 288, total SS (TSS) of 422 mg/L, total dissolved solid (TDS) of 288 mg/L, and BOD of 110 mg/L while that of the beverage has pH of 8.9, EC of 832, TSS of 125 mg/L, TDS of 82 mg/L, and BOD of 191 mg/L. Characterization of wastewater from dairy products industry are presented in [Table 2].
In characterizing effluents from food processing plants, Vanerkar et al.[102] took composite samples of wastewater from different food industries (dairy, beverage, meat and poultry, fruit, etc.) and reported the following results: pH 4.12–4.28, TSS 2210 mg/L, TS 3830 mg/L, COD 11,220 mg/L, BOD 6860 mg/L, TP 3.2 mg/L, and TN 16.4 mg/L.
Tikariha and Sahu[99] embarked on the characterization and treatment of wastewater from dairy industry. The wastewater was collected on monthly interval for a whole year. The analysis revealed the following characteristics: pH 6.1–7.7, EC 352.7–954.0 μmhos/cm, BOD 9033 mg/L, COD 4958 mg/L, and TP 18–26.42 mg/L. Dubey and Joshi[23] characterized and treated the wastewater from the ice cream industry in 2015. The characteristics are pH 6.96–7.95, COD 1,600–3,200 mg/L, BOD 1800 mg/L, TS 3788–3800 mg/L, and TSS 1158–1183 mg/L.
Thomas et al.[98] reported the physicochemical analysis of seafood processing effluents. The following parameters and their values were observed: pH 6.8–7.5, TS 2211.5–3779.9 mg/L, TSS 191.5–680.6 mg/L, BOD 964–2250 mg/L, and COD 1442–2700 mg/L.
Characterization of wastewater from sugar industry was carried out by Lakdawala and Patel.[54] The characteristics revealed that the wastewater has a pH of 6.61, COD 1529.01 mg/L, and BOD 910 mg/L. The slaughterhouse wastewater was characterized and treated by Bustillo-Lecompte et al.[13] The following range of results of the characterization were recorded: pH 4.90–8.10, BOD 610–4635 mg/L, COD 1250–15,900 mg/L, TSS 300–2800 mg/L, TN 50–841 mg/L, and TP 25–200 mg/L. Characterization studies helped in designing a treatment plan ranging from biological treatment methods to adsorption.
| Methods of Treating Wastewater from Food Processing Industries | | |
Discharging untreated wastewaters from food processing industries into rivers and other aquatic environment contribute to eutrophication by addition of phosphorus and nitrogen compounds. Hence, many food processing industries used a whole array of methods in treating their wastewater before the eventual disposal.[74] These treatment methods include photocatalysis,[1],[12],[13],[42],[45],[67],[68],[92] coagulation,[49],[50],[82],[89],[102],[106] AOP such as fenton reaction,[25],[55],[58],[60],[68],[100] electrochemical oxidation,[27],[37],[41],[85],[101] ozonation,[7],[16],[56],[88] biological treatments such as anaerobic digestion,[19],[24],[86],[92],[99],[107] aerobic digestion,[10],[31],[57],[83],[103] combined treatment of anerobic/aerobic system,[12],[13],[33],[58],[83],[103] phytoremediation,[68] and adsorption.[3],[8],[15],[40],[52],[54],[55],[63],[74],[81],[91]
Biological treatment (bioremediation/biodegradation) of food processing industries wastewater
The conventional chemical/physicochemical methods of treating effluents from industries have not been successful in overcoming the complex pollution load of industrial wastewater, and sometimes they also contribute to another type of complex by-product which is more difficult to treat and further pollutes the soil or water sources.[80] Furthermore, these methods (chemical/physicochemical) utilize costly chemicals and treatment units which are difficult to manage in the industries.[4] However, biological methods involve the use of microbes and plants for the treatment of effluents. Microbes undergo degradation or conversion of the waste into some other form. Most importantly, whether degradation or conversion to other products, the end product is nontoxic and less problematic than the initial substance. Microorganism plays an important role in the degradation of xenobiotics and in maintaining the steady-state concentration of chemicals in the environment.[60] Biological treatment can be achieved by aerobic and anaerobic method. Various high rate reactors have been designed for the biological treatment at full-scale operation.[20]
In 2016, Noukeu et al.[68] used stillage (Eichhornia crassipes and Panicum maximum) to treat effluent from food processing industries. In this study, they collected effluents from food processing industries and characterized them before and after treatment. The results revealed that treating with E. crassipes reduced TDS from 3100 mg/L to 351 mg/L, COD from 22,500 mg/L to 150 mg/L, BOD5 from 20,300 mg/L to 123 mg/L, SS from 100 mg/L to 8 mg/L, phosphate from 101 mg/L from 2.4 mg/L, and nitrate from 12 mg/L to 8 mg/L, while treatment with P. maximum makes TDS to reduce from 3100 mg/L to 576 mg/L, COD from 22500 mg/L to 380 mg/L, BOD5 from 20,300 to 239 mg/L, SS from 100 mg/L to 12 mg/L, and nitrates from 12 mg/L to 0 mg/L.
Anaerobic treatment
The treatment of industrial wastewaters using anaerobic technology was used earlier for the treatment of effluents from various industries such as tanneries, food processing ranging from high-strength waste to low-strength waste. Various reactors have been developed to treat wastewater from different industries such as anaerobic contact reactor, upflow anaerobic sludge blanket reactor (UASB), fluidized bed reactor, and anaerobic fixed-film reactor.[80]
In anaerobic treatment, the high organic content in effluents decomposes into methane and carbon dioxide with the help of microorganisms. This treatment shows huge advantages such as production of very little sludge, requirement of less amount of energy, operation at high organic loading rate, need of low nutrient amount, and production of biogas which can be utilized for energy production in the process.[65] Ganesh et al.[35] studied the performance of upflow anaerobic fixed-seed reactors for the treatment of winery wastewater and reported that 80% COD removal was attained.
Upflow anaerobic sludge blanket reactor
UASB reactors have been used widely in treating effluent.[11] Its effective use depends on the formation of active and able granules. These granules consist of self-immobilized, compact form of aggregate of organisms, and lead to their (organisms) effective retention. UASB reactors have some advantages such as independence from mechanical mixing, recycling of sludge biomass, and ability to cope up with perturbances caused by the high loading rate. This reactor is effective in the treatment of effluent in psychrophile conditions.[80]
Schmidt and Ahring[92] treated wastewater from a multiproduct food processing company by UASB reactors. The company processes peas, carrots, celery, roots, and leeks. Four UASB reactors were used for the four different types of wastewater. They noted that there were significant differences in both the activities of the different metabolic groups and the numbers of bacteria in the metabolic group were found indicating that problems could occur when changing from one wastewater to another. On further investigation, they observed that there is significant decrease in overall efficiency when (i) changing from celery wastewater to any other wastewaters due to a significant increase in the organic loading rate of the reactor and (ii) Leek wastewater with high content of lipids and protein was fed to the reactor.
Several studies have been conducted on the use of UASB reactor for the treatment of wastewater from food processing industries.[79] Esparza et al.[29] treated cereal-processing wastewater with UASB reactor and observed 82%–92% COD removal at 17°C with hydraulic retention time (HRT) of 5.2 h. Furthermore, Shastry et al.[94] investigated the treatment of hydrogenated vegetable oil wastewater using UASB reactor and the result revealed COD removal efficiency of 80%–99%. Rajagopal et al.[78] reported the configuration of a UASB reactor and its use in treating wine distillery wastewater. They observed that the method had a high COD removal efficiency of 85%. García et al.[36] also used UASB reactor with polyacrylamide to treat liquid fraction of dairy manure. They found out that the reactor achieved 83% COD removal compared with UASB reactor without the polymer (77% COD removal). In their work on the treatment of synthetic dairy wastewater in series using the same UASB reactor, Kim and Shin[47] reported COD removal of 80%.
Some researchers applied UASB reactors to raw wastewater from cheese–whey industries and their report showed COD removal efficiency of 81%–99%.[14] On the other hand, Yang et al.[108] and Rodgers et al.[86] used UASB reactors to treat cheese–whey wastewater (CWW) in raw and diluted form. Yang et al.[107] reported the COD removal efficiency of 94.6%–96.4% under thermophilic conditions and HRT of 10 days in raw CWW, while Rodgers et al.[86] obtained 89% and HRT of 1 day under mesophilic condition.
Dubey and Joshi[24] treated ice cream industry wastewater using UASB reactor. They revealed that after 12 h in the reactor there was removal of TS, TSS, and TDS by 63.80%, 64.95%, and 61.45%, respectively. Furthermore, there was COD reduction of 66.67% and BOD reduction of 70%.
Other anaerobic reactors
The application of some other anaerobic reactors has also been studied. Rajagopal et al.[77] used upflow anaerobic filters packed with low-density polyethylene medial to treat wastewater discharge from various agro food industries and concluded that the reactor is effective in treating wastewater from these industries. Fuzzato et al.[34] treated lipid-rich wastewater with anaerobic sequencing batch biofilm reactor and achieved 90% removal efficiency. Bialek et al.[9] investigated the performance of two kinds of reactors; inverted fluidized bed and expanded granular sludge bed reactors using it to treat simulated dairy wastewater and observed that at 37°C and HRT of 24 h, there was 80% COD removal. Tikariha and Sahu[99] used anaerobic process in a bioreactor to treat wastewater from the dairy industry. They reported that there was 80% COD removal after 2 days in the reactor while it increased to 90% after 4 days.
Zhukova et al.[109] studied the use of combined anaerobic/aerobic in treating the wastewater from food industry in removing nitrogen compounds. They installed four bioreactors in series and found out that there was a removal efficiency of 98%.
Aerobic reactor
Fang[30] reported the aerobic treatment of cheese wastewater and achieved 89% of COD elimination. Furthermore, Frigon et al.[33]treated another cheese wastewater and observed COD reduction of 98%. Rivas et al.[82] treated CWW with aerobic activated sludge and achieved 97% COD removal. Furthermore, in 2011, Rivas et al.[83] treated another CWW with an aerobic reactor (not activated sludge) and achieved 95% COD reduction. Work on aerobic treatment of wastewater from food is scanty because of its limitation which is excessive sludge formation.
Advanced oxidation processes
These processes involve the production of highly free radicals (OH) through chemical, photochemical, and photocatalytic reactors. The methods include Fenton process, ultraviolet (UV) photolysis, sonication, ozonation, and electrochemical oxidation. This applies most especially to refractory organic pollutants.[43],[69]
Electrochemical coagulation
This method involves the formation of OH at active sites of anode and using it to decontaminate wastewater containing organic pollutants.[84] Xu et al.[106] reported the recovery and characterization of by-product from egg processing plant wastewater using coagulant. They used four coagulants, namely, lignosulfonate (LSA), bentonite (BEN), carboxymethylcellulose, and ferric chloride (FeCl3). They observed that for the four coagulants, there was removal efficiency of 90%, 97%, and 95% for COD, turbidity, and TS, respectively.
Electrocoagulation using Fe and Al was used to treat wastewater from cattle slaughterhouse by Un et al.[101] The results revealed that there was 94.4% removal of COD using Al electrode, while it was 81.1% using Fe electrode. Baker's yeast wastewater was treated by Kobya and Delipinar[48] using Fe and Al electrodes. They reported COD removal of 71%, total organic carbon (TOC) removal of 53%, and turbidity reduction of 90% at pH of 6.5, current density of 70 A/m2, and operating time of 50 min for Al electrode. For Fe electrode, COD removal of 69%, TOC removal of 52%, and turbidity reduction of 56% were obtained at pH of 7, current density of 70 A/m2 and operating time of 50 min. Roa-morales et al.[85] used aluminum electrocoagulation and hydrogen peroxide to treat wastewater from pasta and cookie wastewater under the condition of pH 4 and current density of 18.2 mA/m2. COD removal of 90%, BOD reduction of 96%, and TS removal of 95% were achieved. Vanerkar et al.[102] treated the wastewater from food processing industry using coagulation/flocculation process. They reported that with lime dosage of 200 mg/L, there was reduction in COD and BOD of 53.59% and 57.19%, respectively. They also investigated the potential of alum as a coagulant which showed the reduction in COD and BOD varied between 16.81%–29.97% and 22.81%–38.81% for doses between 50 and 100 mg/L, respectively. They also observed more efficiency when lime of 200 mg/L was combined with 0.3 mg/L of magnafloc E-207 (a polyelectrolyte) which was 67.61%, 71.01%, and 81.53% reductions in COD, BOD, and SS, respectively.
Sangeetha et al.[89] studied the COD removal from sago industries wastewater and the optimization of the process parameters using Box–Behnken design. The result revealed that at optimum condition at 100 mg/L of alum (coagulant) dosage, pH 4.5, and 2.5 g/L concentration of wastewater, there was COD removal efficiency of 67.86%.
Fenton process
This involves oxidation with Fenton's reagent which is a mixture of ferrous ions and hydrogen peroxide.[38] Several researchers have investigated the use of this method on wastewater from different food and allied processing industries. Effluents from baker's yeast industry were treated using Fenton's oxidation by Pala and Erden.[70] They reported 88% COD removal at pH 4 and reaction time of 20 min. Livestock producing industry wastewater was also treated using Fenton process and COD and color removal of 88% and 95.4%, respectively, were reported by Lee and Shoda.[56] In addition, when treated with Fenton's reagents, wastewater from olive oil mill recorded 80% COD removal and 85% total phenol removal. This was reported by Kiril Mert et al.[58]
Ozonation
This process uses ozone (O3) as oxidizing agents. O3, being a strong oxidizing agent, leaves no toxic residue that has to be removed or disposed.[100] It reacts well with conjugated double bond which is often associated with color.[17] Olive oil mill wastewater was also treated by ozonation. This was done at three different times of 60, 90, and 120 min with the highest efficiency achieved at 120 min. The results revealed polyphenols and COD reduction of 82.4% and 59.8%, respectively. The study was reported by Andreozzi et al.[7] Distillery wastewater was treated by Sangave et al.[88] using ozonation process. They achieved 79% COD reduction, while the treatment of molasses fermentation wastewater gave 90% color reduction and COD removal of 37%.[17]
Photocatalysis
This process involves the excitation of semiconductors by electromagnetic radiation to produce conduction band electrons and valence band holes capable of removing pollutants.[95] Some catalytic materials that have been studied include TiO2, ZnO, SnO, WO3, ZrO2, CeO, and YO3.[87]
Oily wastewater from restaurant was treated with UV/TiO2 under the following conditions of 10 min of radiation, 150 mg/L of TiO2, and pH of 7.0. The study revealed the removal efficiency of COD, BOD, and oil of 63%, 43%, and 70%, respectively, it was reported by Kang et al.[45] Furthermore, Agustina et al.[1] reported the treatment of winery wastewater with TiO2/H2O2; about 84% COD removal was achieved in the process. Molasses fermentation wastewater was subjected to treatment with calcined YO3 and the report indicated that there was decolorization of 98.23% and COD removal of 92.98%. The study was carried out by Qin et al.[75] A study was conducted on treatment of molasses wastewater with UV/TiO2/MoO3 by Navgire et al.[67] They observed 70% color removal and reduction of COD (90%), BOD (90%), and TDS (50%).
Combined process
This method is usually employed to reduce cost and enhance efficiency. It is also used to reduce reaction time.[108] A combination of photocatalysis and ozonation processes (UV/H2O2/O3) was used to treat coffee wastewater by Zayas et al.[108] They observed that the process was capable of reducing COD content of the wastewater by 87% in 35 min at optimum pH of 2.0. De Sena et al.[22] used dissolved air floatation (DAF) with UV/H2O2 or photo-Fenton to treat wastewater from the meat industry. They reported that using DAF/UV/H2O2 gives reduction of BOD5, COD, TS, and VS by 82.9%, 91.1%, 72.5%, and 77.0%, respectively. Olive mill wastewater was also treated with UV/O3 and the removal of 91% COD was achieved by Lafi et al.[53] But when olive mill wastewater was subjected to modified photo-Fenton/ozonation, there was 87.9% polyphenol reduction and 64.9% COD reduction. The study was carried out by Andreozzi et al.[7]
Coagulation/flocculation process
This is referred to as the most simple and economical. It involves using a solution of some salts to precipitate dissolved organic compounds. The use of coagulants such as alum and FeCl3 has been studied.[74],[102] Qasim and Mane[74] used alum to treat wastewater from dairy, sweets, snacks, and ice-cream industries, respectively. Wastewaters from the different food processing industries were treated with lime, alum, ferrous sulfate (FeSO4), and FeCl3. They reported the following percentage removal: 71.5% SS, 65.58% BOD, and 59.47% COD using lime. In the case of alum, 54.5% SS removal, 38.81% BOD removal, and 29.97% COD removal were achieved all at 300 mg/L dose of coagulant. The results revealed that FeSO4 coagulant gave 72.52% SS removal, 58.22% BOD removal, and 52.99% COD removal while that of FeCl3 gives 71.15% SS removal, 44.64% BOD removal, and 41.59% COD removal at 175 mg/L dose of coagulants.
Xu et al.[106] used four coagulants, namely Lignosulfonate (LSA), carboxymethyl cellulose (CMC), bentonite (BEN), and FeCl3, to treat wastewater from egg processing plant. They reported that using LSA, the removal percentages for COD, TSS, and turbidity (TUR) were 94%, 99%, and 98%, respectively, while those for CMC were 95%, 99%, and 98% for COD, TSS, and TUR, respectively. They also observed that using BEN gave 97% COD removal, 98.7% TSS removal, and 99% turbidity removal while for FeCl3, 88% COD removal, 99% TSS removal, and 99% TOR removal were achieved. Cheese Whey Wastewater (CWW) was treated with three coagulants, namely FeSO4, FeCl3, and alum, by Rivas et al.[82] The results obtained indicated that there was reduction of COD by 43%, BOD 67%, TOR 97%, total Kjeldahl nitrogen (TKN), 43%, and phosphorus (P) 89% for FeSO4 while in the case of FeCl3, percentage removal was 32% for COD, 23% for BOD, 72% for TOR, 44% for TKN, and 14% for P. On the other hand, alum removed COD by 35%, BOD 36%, TOR 96%, TKN 44%, and P by 77%.
Adsorption
This is a natural process by which molecules of dissolved substance collect on and adhere to the surface of an adsorbent (solid). It occurs when the attraction force at the adsorbent surface overcome the attractive forces of the dissolved substance of the liquid.[74] Works have been done on treatment of wastewater using adsorption techniques. Notable among this is a study conducted by Amuda and Ibrahim.[6] The authors used commercial activated carbon, activated carbon from coconut shell to treat wastewater from a beverage industry. The results showed that acid-activated coconut shell carbon has the highest COD removal of about 92% followed by barium chloride-activated coconut shell carbon with 72% and commercial-activated carbon with 69% COD removal. Petalas et al.[73] used an agricultural by-product, olive pomace, as an adsorbent in removing total phenols in the wastewater from an olive mill industry. They reported that at optimum conditions, the adsorption efficiency for the removal of total phenols was 40%. Studies on the adsorptive treatment of distillery wastewater by bagasse fly ash, a by-product from sugar industry, was carried out by Kulkarni et al.[52] They indicated that at optimum pH of 6 and contact time of 2.5 h, there was 85% COD removal.
Qasim and Mane[74] investigated the treatment of wastewater from dairy, sweet, and ice-cream industries by adsorption. They observed that there was reduction in COD and TDS upon treatment with activated carbon. Sugar mill effluent was treated with activated charcoal, wood ash, and bagasse pith by Suxena and Madan.[96] The results revealed that there was 76.18% COD reduction, 70.65% BOD reduction, 86.6% TDS reduction, and 79.18% TS reduction for activated charcoal while for wood ash, there was reduction in COD, BOD, TDS, and TS by 67.43%, 58.64%, 74.08%, and 72.34%, respectively. The percentage reduction in COD, BOD, TDS and TS when treated with bagasse was found to be 74.41%, 60.71%, 83.99% and 76.22% respectively. Murali et al.[64] used a low-cost biosorbent, water hyacinth, to reduce the COD of wastewater from the dairy industry. They observed that at optimum contact time of 40 min, there was COD reduction of 65.4% and at optimum dosage of 15 g, there was a reduction of 89.5%.
Karale and Suryavanshi[46] treated dairy wastewater with a mixture of coconut shell-activated carbon (CSAC) and laterite. They use column chromatography to investigate the effect of operating parameter. The results indicated that when CSAC and laterite were mixed in ratio 1:1, there was COD reduction of 72.85% and BOD reduction of 76.75%, while on mixing with ratio 2:1 (CSAC to laterite), COD reduces to 75.3% and BOD reduces to 79.69%, and then mixing with ratio 1:2 (CSAC to laterite), COD reduces to 80.65% and BOD reduces to 81.09%. Lakdawala and Patel[51] studied the adsorption capacity of zeolite for removal of chemical and BODs from wastewater from the sugar industry. The results revealed that at optimum dosage of 160 g/L, there was 26.67% COD reduction and 30.79% BOD reduction. Sasikala and Muthuraman[90] studied the reduction of COD in pond water by activated carbons from Moringa oleifera, sugarcane bagasse, coconut coir, and sawdust. They observed that at optimum conditions sawdust-activated carbon has the highest percentage removal of COD of 95% followed by coconut coir which is 75% while sugarcane bagasse has 45% and then Moringa oleifera's was 70%. Wastewater from the dairy industry was also treated with rice husk using the principle of adsorption. This was studied by Pathak et al.[72] The investigation was carried out with variation of parameters such as contact time and adsorbent dosage. The results showed that there was maximum COD removal of 92.5% at dosage of 5 g/L, pH of 2, and temperature of 30°C. Subjecting the data to isotherm and kinetics models, it was observed that the adsorption process followed Langmuir isotherm closely and fitted into pseudo-second-order kinetic model. The thermodynamic parameters also suggested that the process was spontaneous, exothermic, and enthalpy driven.
| Conclusion | | |
One of the most important industries in civilized societies is the food processing industry. Food, because of its importance to life, makes large numbers of humans and animals to be dependent on it. But aside this, food processing produces enormous pollutants, therefore, the growth of food processing industries may have hazardous effect on the quality of aquatic environment and human health. Thus, one of the major causes of concern about the day by day increased level of water pollution is the food processing industry; hence, there is a need for regular monitoring and characterization of wastewaters from food processing industries. As a result of the rapid decrease in the level of water resources, and the increasing demand for water, it is important to reuse wastewater by finding and using a treatment process that is sustainable to clean up polluted wastewater that is economical and safe and could be easily accessed by the common people.
Industry is a point source of pollution because contaminants are produced during manufacturing process. Different treatment methods for food processing have contributed largely in determining the fate of these recalcitrant organic substances in various treatment systems. These include advanced oxidation processes such as ozonation, Fenton reaction, ultrasonic irradiation, direct photolysis and photocatalysis (TiO2 and solar), and coagulation/flocculation. These methods significantly improved the removal rate and biodegradability of organics from food processing wastewater. However, there is a need to increase treatment efficiencies, identify the degradation substances, and determine the feasibility and the cost of full-scale operations. This gives rise to the use of biological methods.
Biological methods of treatment have been used long ago for the treatment of food processing wastewater. They are subdivided into aerobic and anaerobic processes; anaerobic processes include anaerobic filters, sludge reactors, sequence batch reactor, membrane batch reactor, and use of activated sludge. However, some factors come into play that requires modifications for the food processing wastewater to adapt to enhance high efficiency of biodegradability and capable mineralization of biological processes.
Adsorption is the latest means of treating wastewater which has high efficiency and produces no sludge. It is also very economical in that the adsorbent can be desorbed and reused for further treatment. But in the early discovery of adsorption method, activated charcoal was used as adsorbent, but the need to reduce the cost of adsorption gives rise to finding an alternative cheaper and equally effective and efficient adsorbent. This was achieved by so many researchers which used carbonaceous materials such as barks, roots, leaves, shells, husks of both plant and animal whether in raw, modified, or carbonized form and these have been found to have high treatment efficiencies as that of activated charcoal. All these processes are aimed at having a pollutant-free wastewater which goes into the environment, but adsorption seems to be the less cumbersome, easy to operate, and cheap. However, all the technologies, when singly used have lower efficiencies compared to when two or more treatment methods are combined, especially with adsorption. This is likely to be one of the best technologies to protect and clean up the environment.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]
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