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New Technologies in the Dairy Industry Wastewater Treatment

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The dairy industry involves processing raw milk into products such as consumer milk, butter, cheese, yogurt, condensed milk, dried milk (milk powder), and ice cream, using processes such as chilling, pasteurization, and homogenization. Typical by-products include buttermilk, whey, and their derivatives.

The wastewaters discharged by raw milk quality control laboratories are more complex than the ones commonly generated by dairy factories because of the presence of certain chemicals such as sodium azide or chloramphenicol, which are used for preserving milk before analysis.

This section provides details on the latest developments and efforts in the dairy industry waste water treatment.

We have discussed the following:

  • Current Wastewater Treatment Process - Dairy Industry
  • New Technologies in the Dairy Industry Waste Water Treatment
    • Biomethanation of Whey and Cattle Dung
    • Treatment of Dairy Industry Wastewater by Reverse Osmosis for Water Reuse
    • Anaerobic Filter Reactor Performance for the Treatment of Complex Dairy Wastewater at Industrial Scale
    • Influence of the Content in Fats and Proteins on the Anaerobic Biodegradability of Dairy Wastewaters
    • Influence of Filtration Conditions on The Performance of Nanofiltration and Reverse Osmosis Membranes in Dairy Wastewater Treatment
    • Anaerobic Treatment of Dairy Wastewaters: A Review
    • Electrochemical Technologies in Wastewater Treatment
    • Hydrolytic Enzymes as Coadjuvants in the Anaerobic Treatment of Dairy Wastewaters
    • Effect of Enzymatic Hydrolysis on Anaerobic Treatment of Dairy Wastewater

Current Wastewater Treatment Process - Dairy Industry

Pollution Characteristics and Current Treatment Practices of Dairy Industry Waste

 

The average volume of wastewater in dairies is currently 1.3 l/kg milk. This results in considerable wastewater disposal costs. Hygiene is the most important factor in milk processing and the production of dairy products. This necessarily results in the use of considerable volumes of water for cleaning purposes. In addition, considerable quantities of wastewater with volatile milk constituents, fats and proteins occur when milk is being processed, particularly during evaporation and spray-drying.

Pretreatment of effluents consists of screening, flow equalization, neutralization, and air flotation (to remove fats and solids); it is normally followed by biological treatment. If space is available, land treatment or pond systems are potential treatment methods. Other possible biological treatment systems include trickling filters, rotating biological contactors, and activated sludge treatment.

Pretreated dairy effluents can be discharged to a municipal sewerage system, if capacity exists, with the approval of the relevant authority. Odor control by ventilation and scrubbing may be required where cheese is stored or melted. Dust control at milk powder plants is provided by fabric filters.

After aerobic or anaerobic biological treatment of dairy wastewaters, the residual sludge is sent through a clarifying decanter which efficiently dewaters the sludge before the clean water is recycled back into the process. A calculation by the Verband der deutschen Milchwirtschaft (Association of German Dairying) shows how in-plant wastewater treatment pays: direct dischargers, i. e. operations with their own wastewater processing facility, operate with costs that are up to two thirds lower than users of municipal wastewater treatment plants.

New Technologies in the Dairy Industry Waste Water Treatment

The following article throws light on the disposal of salty whey in the dairy industry which is a major problem faced now:

Biomethanation of a Mixture of Salty Cheese Whey and Poultry Waste or Cattle Dung

This paper describes the results of a study aimed at improving the efficiency of anaerobic digestion of salty cheese whey in combination with poultry waste or cattle dung. Best results were obtained when salty cheese whey was mixed with poultry waste in the ratio of 7:3, or cattle dung in the ratio of 1:1, both on dry weight basis giving maximum gas production of 1.2 L/L of digester/d with enriched methane content of 64% and 1.3 L/L of digester/d having methane content of 63% respectively. Various conditions such as temperature and retention time have been optimized for maximum process performance.2

Treatment of Dairy Industry Wastewater by Reverse Osmosis for Water Reuse

The dairy industry is among the most polluting of the food industries in volume in regard to its large water consumption. The present work was related to investigations about practices of water management of 11 dairy plants. Treatment of the process water produced in the starting, equilibrating, stopping and rinsing processing units was proposed to produce water for reuse in the plant and to lower the effluent volume. Reverse osmosis of such wastewaters, collected in dairy plants, was performed after a prior check of their stability during storage. Filtration performances were focused on permeate flux versus water recovery and on water quality (TOC, conductivity). Reverse osmosis water similar to available vapour condensates (produced in drying processes) can be achieved allowing this water to be reused for heating, cleaning and cooling purposes. A 540 m2 RO unit is required to treat 100 m3/d of wastewater with 95% water recovery.3

Anaerobic Filter Reactor Performance for the Treatment of Complex Dairy Wastewater at Industrial Scale

The wastewaters discharged by raw milk quality control laboratories are more complex than the ones commonly generated by dairy factories because of the presence of certain chemicals such as sodium azide or chloramphenicol, which are used for preserving milk before analysis. The treatment of these effluents has been carried out in a full-scale plant comprising a 12 m3 anaerobic filter (AF) reactor and a 28 m3 sequential batch reactor (SBR). After more than 2 years of operation, a successful anaerobic treatment of these effluents was achieved, without fat removal prior to the anaerobic reactor. The organic loading rates maintained in the AF reactor were 5–6 kg COD/m3 d, with COD removal being higher than 90%. No biomass washout was observed, and most of the fat contained in the wastewaters was successfully degraded. The addition of alkalinity is crucial for the maintenance of a proper buffer medium to ensure pH stability. The effluent of the AF reactor was successfully treated in the SBR reactor, and a final effluent with a COD content below 200 mg/l and total nitrogen below 10 mg N/l was obtained.4

Influence of the Content in Fats and Proteins on the Anaerobic Biodegradability of Dairy Wastewaters

The relative amounts of fats, proteins and carbohydrates in wastewaters from dairy industries cause problems during their anaerobic treatment. The anaerobic biodegradability of two synthetic wastewaters, one rich in fats (chemical oxygen demand (COD) ratio; Fats/Proteins/Carbohydrates: 1.7/0.57/1) and the other with a low fat content (COD ratio; Fats/Proteins/Carbohydrates: 0.05/0.54/1) was studied in samples with total COD ranging from 0.4 to 20 g/l. There were no problems of sludge flotation and the maximum biodegradability and methanisation were obtained when operating with wastewaters in the range of 3–5 gCOD/l. The intermediates of fat degradation (glycerol and long chain fatty acids) seemed not to reach concentrations high enough to affect the process. The anaerobic biodegradation of fat-rich wastes was slower than carbohydrate-rich wastes due to the slower hydrolytic step of fat degradation which prevented the accumulation of volatile fatty acids (VFAs) and favoured the overall process. Carbohydrate-rich wastewater degradation produced free ammonia (FA) at concentrations near to inhibitory levels (62.2 mg FA/l), but in this case, ammonia production facilitated regulation of fall in pH caused by of the accumulation of VFA.5

Influence of Filtration Conditions on the Performance of Nanofiltration and Reverse Osmosis Membranes in Dairy Wastewater Treatment

Filtration performance and fouling of nanofiltration (NF) and reverse osmosis (RO) membranes in the treatment of dairy industry wastewater were investigated. Two series of experiments were performed. The first one involved a NF membrane (TFC-S) for treating the chemical-biological treatment plant effluents. The second one used a RO membrane (TFC-HR) for treating the original effluents from the dairy industry. The permeate flux was higher at higher transmembrane pressures and higher feed flowrates. The curves of permeate flux exhibited a slower increase while the feed flowrate decreased and the pressure increased. Membrane fouling resulted in permeate flux decline with increasing the feed COD concentration. Furthermore, the flux decline due to the COD increase was found higher at higher pressures for both NF and RO membranes.6

Anaerobic Treatment of Dairy Wastewaters: A Review

Anaerobic treatment is often reported to be an effective method for treating dairy effluents. The objective of this paper is to summarize recent research efforts and case studies in anaerobic treatment of dairy wastewaters. The main characteristics of industrial dairy waste streams are identified and the anaerobic degradation mechanisms of the primary constituents in dairy wastewaters, namely carbohydrates (mainly lactose), proteins and lipids are described. Primary attention is then focused on bench–pilot–full-scale anaerobic treatment efforts for dairy waste effluents. Combined (anaerobic–aerobic) treatment methods are also discussed. Finally, areas where further research and attention are required are identified.7

Electrochemical Technologies in Wastewater Treatment

This paper reviews the development, design and applications of electrochemical technologies in water and wastewater treatment. Particular focus was given to electrodeposition, electrocoagulation (EC), electroflotation (EF) and electrooxidation. Over 300 related publications were reviewed with 221 cited or analyzed. Electrodeposition is effective in recover heavy metals from wastewater streams. It is considered as an established technology with possible further development in the improvement of space-time yield. EC has been in use for water production or wastewater treatment. It is finding more applications using either aluminum, iron or the hybrid Al/Fe electrodes. The separation of the flocculated sludge from the treated water can be accomplished by using EF. The EF technology is effective in removing colloidal particles, oil & grease, as well as organic pollutants. It is proven to perform better than either dissolved air flotation, sedimentation, impeller flotation (IF). The newly developed stable and active electrodes for oxygen evolution would definitely boost the adoption of this technology. Electrooxidation is finding its application in wastewater treatment in combination with other technologies. It is effective in degrading the refractory pollutants on the surface of a few electrodes. Titanium-based boron-doped diamond film electrodes (Ti/BDD) show high activity and give reasonable stability. Its industrial application calls for the production of Ti/BDD anode in large size at reasonable cost and durability.8

Hydrolytic Enzymes as Coadjuvants in the Anaerobic Treatment of Dairy Wastewaters

An enzymatic extract produced by Penicillium restrictum having a high level of lipase activity (17.2 U.g-1) was obtained by solid-state Fermentation using babassu cake as substrate. The enzymatic extract was used in the hydrolysis of a dairy wastewater with high fat contents (180, 450, 900 and 1,200 mg.L-1). Different hydrolysis conditions were tested, and it was determined that it should be carried out at a temperature of 35ºC, without agitation, with 10% v/v enzymatic extract and a hydrolysis time of 12 hours. Both crude and hydrolysed effluents were then submitted to an anaerobic biological treatment. It was observed that for the enzymatically pretreated effluent there was a significant improvement in the efficiency of the anaerobic treatment. For the highest fat content tested (1,200 mg.L-1), removal efficiencies of 19 and 80% were attained for crude and hydrolysed effluents, respectively. In addition, a tenfold increase in the removal rate of COD from the hydrolysed effluent (1.87 kg COD.m-3.d-1) was observed in relation to the crude effluent (0.18 kg COD.m-3.d-1). The results obtained in this study illustrate the viability of using a hybrid treatment (enzymatic-biological) for wastewaters having high fat contents.9

Effect of Enzymatic Hydrolysis on Anaerobic Treatment of Dairy Wastewater

The biological treatment of a synthetic dairy wastewater containing high levels of oil and grease (200, 600 and 1000 mg/l) was investigated, using two identical UASB reactors. One reactor was fed with wastewater from an upstream enzymatic hydrolysis step and the other with raw wastewater. The hydrolysis was carried out at 35 °C for 14 h, using an enzyme preparation obtained through solid-state fermentation, presenting pronounced lipase activity. The reactors were continuously operated with each fat concentration. The performance of both reactors was similar up to the concentration of 600 mg/l. However, the benefits of the hydrolysis step became evident with the highest concentration (1000 mg/l). COD removals averaged 90% in the reactor fed with the hydrolyzed effluent and 82% in the control reactor. The results showed that UASB reactors are able to operate, even when fed with high levels of oil and grease in dairy wastewaters.10

References

1http://www.westfalia-separator.com/applications/fluids-water/drinking-water-recovery-waste-water-treatment/treatment-of-dairy-waste-water.html

2Chirag Patel and Datta Madamwar, 1996. Biomethanation of a mixture of salty cheese whey and poultry waste or cattle dung. Applied Biochemistry and Biotechnology, Volume 60.

3Mickael Vourch, Béatrice Balannec, Bernard Chaufer and Gérard Dorange, 2008. Treatment of dairy industry wastewater by reverse osmosis for water reuse. Desalination, 219 (190- 202).

4Francisco Omil, Juan M. Garrido, Belén Arrojo and Ramón Méndez, 2003. Anaerobic filter reactor performance for the treatment of complex dairy wastewater at industrial scale. Water Research, 37 (4099-4108).

5 Vidal G, Carvalho A., Méndez R and Lema J. M, 2000.  Influence of the content in fats and proteins on the anaerobic biodegradability of dairy wastewaters. Bioresource technology, 74 (231- 239).

6Mustafa Turan, 2004. Influence of filtration conditions on the performance of nanofiltration and reverse osmosis membranes in dairy wastewater treatment. Desalination, 170 (83- 90).

7Burak Demirel, Orhan Yenigun and Turgut T. Onay, 2005. Anaerobic treatment of dairy wastewaters: a review. Process biochemistry, 40 (2583- 95).

8Guohua Chen, 2004.  Electrochemical technologies in wastewater treatment. Separation and Purification Technology, 38 (11-41).

9Leal M.C.M.R, Cammarota M.C, Freire D.M.G and SantAnna Jr G.L, 2002. Hydrolytic enzymes as coadjuvants in the anaerobic treatment of dairy wastewaters.  Brazilian Journal of Chemical Engineering, volume 19.

10Leal M.C.M.R, Cammarota M.C, Freire D.M.G and SantAnna Jr G.L, 2002. Effect of enzymatic hydrolysis on anaerobic treatment of dairy wastewater.  Process biochemistry, 41 (1173-78). 

The dairy industry involves processing raw milk into products such as consumer milk, butter, cheese, yogurt, condensed milk, dried milk (milk powder), and ice cream, using processes such as chilling, pasteurization, and homogenization. Typical by-products include buttermilk, whey, and their derivatives.

The wastewaters discharged by raw milk quality control laboratories are more complex than the ones commonly generated by dairy factories because of the presence of certain chemicals such as sodium azide or chloramphenicol, which are used for preserving milk before analysis.

This section provides details on the latest developments and efforts in the dairy industry waste water treatment.

We have discussed the following:

  • Current Wastewater Treatment Process - Dairy Industry
  • New Technologies in the Dairy Industry Waste Water Treatment
    • Biomethanation of Whey and Cattle Dung
    • Treatment of Dairy Industry Wastewater by Reverse Osmosis for Water Reuse
    • Anaerobic Filter Reactor Performance for the Treatment of Complex Dairy Wastewater at Industrial Scale
    • Influence of the Content in Fats and Proteins on the Anaerobic Biodegradability of Dairy Wastewaters
    • Influence of Filtration Conditions on The Performance of Nanofiltration and Reverse Osmosis Membranes in Dairy Wastewater Treatment
    • Anaerobic Treatment of Dairy Wastewaters: A Review
    • Electrochemical Technologies in Wastewater Treatment
    • Hydrolytic Enzymes as Coadjuvants in the Anaerobic Treatment of Dairy Wastewaters
    • Effect of Enzymatic Hydrolysis on Anaerobic Treatment of Dairy Wastewater

Current Wastewater Treatment Process - Dairy Industry

Pollution Characteristics and Current Treatment Practices of Dairy Industry Waste

 

The average volume of wastewater in dairies is currently 1.3 l/kg milk. This results in considerable wastewater disposal costs. Hygiene is the most important factor in milk processing and the production of dairy products. This necessarily results in the use of considerable volumes of water for cleaning purposes. In addition, considerable quantities of wastewater with volatile milk constituents, fats and proteins occur when milk is being processed, particularly during evaporation and spray-drying.

Pretreatment of effluents consists of screening, flow equalization, neutralization, and air flotation (to remove fats and solids); it is normally followed by biological treatment. If space is available, land treatment or pond systems are potential treatment methods. Other possible biological treatment systems include trickling filters, rotating biological contactors, and activated sludge treatment.

Pretreated dairy effluents can be discharged to a municipal sewerage system, if capacity exists, with the approval of the relevant authority. Odor control by ventilation and scrubbing may be required where cheese is stored or melted. Dust control at milk powder plants is provided by fabric filters.

After aerobic or anaerobic biological treatment of dairy wastewaters, the residual sludge is sent through a clarifying decanter which efficiently dewaters the sludge before the clean water is recycled back into the process. A calculation by the Verband der deutschen Milchwirtschaft (Association of German Dairying) shows how in-plant wastewater treatment pays: direct dischargers, i. e. operations with their own wastewater processing facility, operate with costs that are up to two thirds lower than users of municipal wastewater treatment plants.

New Technologies in the Dairy Industry Waste Water Treatment

The following article throws light on the disposal of salty whey in the dairy industry which is a major problem faced now:

Biomethanation of a Mixture of Salty Cheese Whey and Poultry Waste or Cattle Dung

This paper describes the results of a study aimed at improving the efficiency of anaerobic digestion of salty cheese whey in combination with poultry waste or cattle dung. Best results were obtained when salty cheese whey was mixed with poultry waste in the ratio of 7:3, or cattle dung in the ratio of 1:1, both on dry weight basis giving maximum gas production of 1.2 L/L of digester/d with enriched methane content of 64% and 1.3 L/L of digester/d having methane content of 63% respectively. Various conditions such as temperature and retention time have been optimized for maximum process performance.2

Treatment of Dairy Industry Wastewater by Reverse Osmosis for Water Reuse

The dairy industry is among the most polluting of the food industries in volume in regard to its large water consumption. The present work was related to investigations about practices of water management of 11 dairy plants. Treatment of the process water produced in the starting, equilibrating, stopping and rinsing processing units was proposed to produce water for reuse in the plant and to lower the effluent volume. Reverse osmosis of such wastewaters, collected in dairy plants, was performed after a prior check of their stability during storage. Filtration performances were focused on permeate flux versus water recovery and on water quality (TOC, conductivity). Reverse osmosis water similar to available vapour condensates (produced in drying processes) can be achieved allowing this water to be reused for heating, cleaning and cooling purposes. A 540 m2 RO unit is required to treat 100 m3/d of wastewater with 95% water recovery.3

Anaerobic Filter Reactor Performance for the Treatment of Complex Dairy Wastewater at Industrial Scale

The wastewaters discharged by raw milk quality control laboratories are more complex than the ones commonly generated by dairy factories because of the presence of certain chemicals such as sodium azide or chloramphenicol, which are used for preserving milk before analysis. The treatment of these effluents has been carried out in a full-scale plant comprising a 12 m3 anaerobic filter (AF) reactor and a 28 m3 sequential batch reactor (SBR). After more than 2 years of operation, a successful anaerobic treatment of these effluents was achieved, without fat removal prior to the anaerobic reactor. The organic loading rates maintained in the AF reactor were 5–6 kg COD/m3 d, with COD removal being higher than 90%. No biomass washout was observed, and most of the fat contained in the wastewaters was successfully degraded. The addition of alkalinity is crucial for the maintenance of a proper buffer medium to ensure pH stability. The effluent of the AF reactor was successfully treated in the SBR reactor, and a final effluent with a COD content below 200 mg/l and total nitrogen below 10 mg N/l was obtained.4

Influence of the Content in Fats and Proteins on the Anaerobic Biodegradability of Dairy Wastewaters

The relative amounts of fats, proteins and carbohydrates in wastewaters from dairy industries cause problems during their anaerobic treatment. The anaerobic biodegradability of two synthetic wastewaters, one rich in fats (chemical oxygen demand (COD) ratio; Fats/Proteins/Carbohydrates: 1.7/0.57/1) and the other with a low fat content (COD ratio; Fats/Proteins/Carbohydrates: 0.05/0.54/1) was studied in samples with total COD ranging from 0.4 to 20 g/l. There were no problems of sludge flotation and the maximum biodegradability and methanisation were obtained when operating with wastewaters in the range of 3–5 gCOD/l. The intermediates of fat degradation (glycerol and long chain fatty acids) seemed not to reach concentrations high enough to affect the process. The anaerobic biodegradation of fat-rich wastes was slower than carbohydrate-rich wastes due to the slower hydrolytic step of fat degradation which prevented the accumulation of volatile fatty acids (VFAs) and favoured the overall process. Carbohydrate-rich wastewater degradation produced free ammonia (FA) at concentrations near to inhibitory levels (62.2 mg FA/l), but in this case, ammonia production facilitated regulation of fall in pH caused by of the accumulation of VFA.5

Influence of Filtration Conditions on the Performance of Nanofiltration and Reverse Osmosis Membranes in Dairy Wastewater Treatment

Filtration performance and fouling of nanofiltration (NF) and reverse osmosis (RO) membranes in the treatment of dairy industry wastewater were investigated. Two series of experiments were performed. The first one involved a NF membrane (TFC-S) for treating the chemical-biological treatment plant effluents. The second one used a RO membrane (TFC-HR) for treating the original effluents from the dairy industry. The permeate flux was higher at higher transmembrane pressures and higher feed flowrates. The curves of permeate flux exhibited a slower increase while the feed flowrate decreased and the pressure increased. Membrane fouling resulted in permeate flux decline with increasing the feed COD concentration. Furthermore, the flux decline due to the COD increase was found higher at higher pressures for both NF and RO membranes.6

Anaerobic Treatment of Dairy Wastewaters: A Review

Anaerobic treatment is often reported to be an effective method for treating dairy effluents. The objective of this paper is to summarize recent research efforts and case studies in anaerobic treatment of dairy wastewaters. The main characteristics of industrial dairy waste streams are identified and the anaerobic degradation mechanisms of the primary constituents in dairy wastewaters, namely carbohydrates (mainly lactose), proteins and Lipids are described. Primary attention is then focused on bench–pilot–full-scale anaerobic treatment efforts for dairy waste effluents. Combined (anaerobic–aerobic) treatment methods are also discussed. Finally, areas where further research and attention are required are identified.7

Electrochemical Technologies in Wastewater Treatment

This paper reviews the development, design and applications of electrochemical technologies in water and wastewater treatment. Particular focus was given to electrodeposition, electrocoagulation (EC), electroflotation (EF) and electrooxidation. Over 300 related publications were reviewed with 221 cited or analyzed. Electrodeposition is effective in recover heavy metals from wastewater streams. It is considered as an established technology with possible further development in the improvement of space-time yield. EC has been in use for water production or wastewater treatment. It is finding more applications using either aluminum, iron or the hybrid Al/Fe electrodes. The separation of the flocculated sludge from the treated water can be accomplished by using EF. The EF technology is effective in removing colloidal particles, oil & grease, as well as organic pollutants. It is proven to perform better than either dissolved air flotation, sedimentation, impeller flotation (IF). The newly developed stable and active electrodes for oxygen evolution would definitely boost the adoption of this technology. Electrooxidation is finding its application in Wastewater Treatment in combination with other technologies. It is effective in degrading the refractory pollutants on the surface of a few electrodes. Titanium-based boron-doped diamond film electrodes (Ti/BDD) show high activity and give reasonable stability. Its industrial application calls for the production of Ti/BDD anode in large size at reasonable cost and durability.8

Hydrolytic Enzymes as Coadjuvants in the Anaerobic Treatment of Dairy Wastewaters

An enzymatic extract produced by Penicillium restrictum having a high level of lipase activity (17.2 U.g-1) was obtained by solid-state fermentation using babassu cake as substrate. The enzymatic extract was used in the hydrolysis of a dairy wastewater with high fat contents (180, 450, 900 and 1,200 mg.L-1). Different hydrolysis conditions were tested, and it was determined that it should be carried out at a temperature of 35ºC, without agitation, with 10% v/v enzymatic extract and a hydrolysis time of 12 hours. Both crude and hydrolysed effluents were then submitted to an anaerobic biological treatment. It was observed that for the enzymatically pretreated effluent there was a significant improvement in the efficiency of the anaerobic treatment. For the highest fat content tested (1,200 mg.L-1), removal efficiencies of 19 and 80% were attained for crude and hydrolysed effluents, respectively. In addition, a tenfold increase in the removal rate of COD from the hydrolysed effluent (1.87 kg COD.m-3.d-1) was observed in relation to the crude effluent (0.18 kg COD.m-3.d-1). The results obtained in this study illustrate the viability of using a hybrid treatment (enzymatic-biological) for wastewaters having high fat contents.9

Effect of Enzymatic Hydrolysis on Anaerobic Treatment of Dairy Wastewater

The biological treatment of a synthetic dairy wastewater containing high levels of oil and grease (200, 600 and 1000 mg/l) was investigated, using two identical UASB reactors. One reactor was fed with wastewater from an upstream enzymatic hydrolysis step and the other with raw wastewater. The hydrolysis was carried out at 35 °C for 14 h, using an enzyme preparation obtained through solid-state fermentation, presenting pronounced lipase activity. The reactors were continuously operated with each fat concentration. The performance of both reactors was similar up to the concentration of 600 mg/l. However, the benefits of the hydrolysis step became evident with the highest concentration (1000 mg/l). COD removals averaged 90% in the reactor fed with the hydrolyzed effluent and 82% in the control reactor. The results showed that UASB reactors are able to operate, even when fed with high levels of oil and grease in dairy wastewaters.10

References

1http://www.westfalia-separator.com/applications/fluids-water/drinking-water-recovery-waste-water-treatment/treatment-of-dairy-waste-water.html

2Chirag Patel and Datta Madamwar, 1996. Biomethanation of a mixture of salty cheese whey and poultry waste or cattle dung. Applied Biochemistry and Biotechnology, Volume 60.

3Mickael Vourch, Béatrice Balannec, Bernard Chaufer and Gérard Dorange, 2008. Treatment of dairy industry wastewater by reverse osmosis for water reuse. Desalination, 219 (190- 202).

4Francisco Omil, Juan M. Garrido, Belén Arrojo and Ramón Méndez, 2003. Anaerobic filter reactor performance for the treatment of complex dairy wastewater at industrial scale. Water Research, 37 (4099-4108).

5 Vidal G, Carvalho A., Méndez R and Lema J. M, 2000.  Influence of the content in fats and proteins on the anaerobic biodegradability of dairy wastewaters. Bioresource technology, 74 (231- 239).

6Mustafa Turan, 2004. Influence of filtration conditions on the performance of nanofiltration and reverse osmosis membranes in dairy wastewater treatment. Desalination, 170 (83- 90).

7Burak Demirel, Orhan Yenigun and Turgut T. Onay, 2005. Anaerobic treatment of dairy wastewaters: a review. Process biochemistry, 40 (2583- 95).

8Guohua Chen, 2004.  Electrochemical technologies in wastewater treatment. Separation and Purification Technology, 38 (11-41).

9Leal M.C.M.R, Cammarota M.C, Freire D.M.G and SantAnna Jr G.L, 2002. Hydrolytic enzymes as coadjuvants in the anaerobic treatment of dairy wastewaters.  Brazilian Journal of Chemical Engineering, volume 19.

10Leal M.C.M.R, Cammarota M.C, Freire D.M.G and SantAnna Jr G.L, 2002. Effect of enzymatic hydrolysis on anaerobic treatment of dairy wastewater.  Process biochemistry, 41 (1173-78). 



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