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INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 1, No 7, 2011

© Copyright 2010 All rights reserved Integrated Publishing Association

Research article ISSN 0976 – 4402

Received on April 2011 Published on June 2011 1621

Utilization and treatment of dairy effluent through biogas generation A case study

Bhumesh Singh Bhadouria 1 , Sai.V.S 2 1 Wildlife Institute of India, Chandrabani, Dehradun, India 2 Awadhesh Pratap Singh University, Rewa, M.P. India

[email protected]

ABSTRACT

Biogas is an alternate source of energy and after realizing the potential of biogas, a National level programme was initiated in India during 1970s. Present study on biogas generation from dairy effluent and control of water pollution has been viewed with the aim of control of water pollution through treatment of dairy waste as well as generation of biogas. Environmental parameters like Temperature, pH, Biological Oxygen Demand (BOD) & Chemical Oxygen Demand (COD) was taken in to account. No change in the average value of temperature and pH was recorded but BOD and COD reduced to the extent of 50 percent. All parameters however showed statistically significant differences at 5 percent level between inlet and outlet point. Gas generation fluctuated between .5m 3 /day to maximum 4.5 m 3 /day with an average of 3m 3 /day was recorded.

Keywords: Biogas, BOD, COD, Dairy effluent

1. Introduction

In India, milk usually distributed by farmers directly to the consumers however remaining part processed in dairy plants to manufacture various milk products. The dairy industries require large quantity of water for the purpose of washing of cans, machinery and floor therefore the liquid waste in a dairy originates from manufacturing process, utilities and service section (CPCB, 1997). Water management in the dairy industry is well documented (Berg Van Den and Kennedy, 1983) but effluent production and disposal remain a problematic issue for the dairy industry. The various sources of waste generation from a dairy are spoiled and skimmed milk. Dairy wastes have high oxygen demand because it is composed of organic matter. In streams it is consumed at very rapid rate causing depletion of oxygen and in some cases exhaustion resulting in serious pollution. Hence the rapid growth in the size of dairy operations has resulted in new laws and regulations governing the handling and disposal of manure. Completely mixed thermophilic digesters were proposed in Oregon to treat dairy manure (Tillamook, 1999). The study presents utilization of dairy effluent through anaerobic technique and control of water pollution as well as generation of biogas from dairy effluent.

2. Materials and Method

2.1 Study Site

Present study was carried out at Grasim Industries Ltd., BirlaGram Nagda, Ujjain (M.P.) India. A Seasonal drain located near the complex in which treated effluent is released.

Utilization and Treatment of Dairy Effluent Through Biogas Generation A Case Study

Bhumesh Singh Bhadouria, Sai.V.S International Journal of Environmental Sciences Volume 1 No.7, 2011

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2.2 Climate

The climate of study site is semitropical and mansoonic characterized by three main seasons, namely, rainy season (Second half of June to Second half of September), winter season (October February) and summer season (MarchJune). Minimum temperature varied between 17 0 C in December to 30 0 C in May while the maximum temperature between 24 0 C in January to 41 0 C in May.

2.3 Methodology

2.3.1 Source of effluent

Waste from milk products contain milk solids in more or less diluted form as stated below:

(i) Spoiled raw or manufacture product

(ii) By products (iii) Spoilage or overflow due to insufficient equipment and careless operations

(iv) Rinsing and washing from canes, equipment and utensils.

2.3.2 Volume of the effluent

The volume of effluent discharged by dairy is near about 20,000 liters/day. The milk processed is nearby 45005000 liters. The volume of effluent or waste liquors generated on an average would be two to three times the volume of milk processed.

2.3.3 Characteristics of effluent

Dairy waste is white in colour and usually slightly alkaline in nature. The use of alkyls and detergents in washing of canes and other utensils makes it acidic quite rapidly because milk sugar gets fermented into lactic acid. The above process decreases the pH immediately, which leads to the precipitation of Cassin. All the waste liquors mentioned above have a high BOD as they contain appreciable concentration of carbohydrates. The dairy effluent have high oxygen demand and decomposition of Cassin leading to the formation of heavy black sludge and strong butyric acid odors characterizing milk waste pollution. Wilkie (2000) reported that the anaerobic process removes a vast majority of the odorous compounds.

2.4 Operation of the plant

Dairy plant handles 45005000 liters of milk every day and treatment is given for the effluent by using standard practices.

Figure 1: Showing the effluent treatment process and biogas generation.

Effluent Dairy→Sump pit →Anaerobic filter→Biogas Storage tank

↓ ↓ ↓ Inlet sampling point Outlet sampling point Biogas



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2.5 Sampling and analysis of dairy effluent

The effluents from dairy were analyzed with respect to the following parameters:

(i) Temperature (ii) pH

(iii) Biological Oxygen Demand (BOD)

(iv) Chemical Oxygen Demand (COD)

(v) Gas Generation

2.6 Methods of Sampling

Daily samples were collected in plastic bottles which were first rinsed with distilled water in the laboratory and then rinsed with effluent at the sampling site.

Samples were taken from inlet and outlet section of the plant (Figure1). Inlet samples consisted of waste effluent and outlet consisted of treated effluent.

2.7 Analysis of Samples

2.7.1 Temperature

Temperature was measured from both untreated inlet and treated outlet sampling points by simple thermometer.

2.7.2 pH

pH of effluent was determined by using pH meter by glass electrode method.

2.7.3 Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD)

BOD and COD were measured by standard methods.

2.8 Statistical analysis

The physical and chemical parameters measured for the inlet and outlet points were compared statistically using paired t test.

3. Results

Analysis of dairy effluent from inlet and outlet point gave following results:

3.1 Temperature

In the present study, the temperature of inlet samples ranged from 26 0 29 0 C and average temperature was 28 0 C which is slightly low but useful for mesophilic bacteria. At the outlet sampling point temperature ranged from 26 0 C to 28 0 C and average temperature was 27 0 C. After treatment the effluent is released in the stream where its temperature is reduced by 1 0 C. The statistical treatment of temperature data using paired t test (Table 1) rewarded significant differences at 5% level between inlet and outlet temperature.



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3.2 pH

In the present study pH value of inlet samples ranged from 5.1 to 7 and average was 6.2. It indicated that the effluent of dairy was slightly acidic in nature. The pH value after treatment or pH value of outlet samples ranged from 6.26.9 and average pH was 6.6, which is desirable for mesophilic bacteria. The pH values of inlet samples showed large fluctuations while that of outlet samples pH values displayed more stable and low fluctuations (Figure 2).

Figure 2: pH value at inlet and outlet point.

3.3 Biological Oxygen Demand

In the present study the inlet effluent analysis showed effluent is highly BOD loaded and average BOD level was 1024 mg/liters, in other words demand of biological oxygen was very high. After anaerobic treatment the analysis of outlet effluent showed reduction in biological oxygen demand up to 403 mg/liter. The statistical treatment of BOD data using paired t test (Table 1) recorded significant difference at 5% level between inlet and outlet. Daily fluctuation in percentage BOD reduction between inlet and outlet samples depicted graphically in Figure 3 which is showing 60 percent of samples recorded less then 50 percent BOD reduction while 40 percent of samples recorded more then 60 percent BOD reduction.

Figure 3: Performance of Biogasgas plant (% BOD reduction)



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3.4 Chemical Oxygen Demand

Present study showed that at inlet effluent analysis COD value ranged from 408 mg/liter to 2800 mg/ liter and average value was 1860 mg/liter. The analysis of COD at outlet sample showed variation from 224 mg/liter to 1600mg/liter. The study showed a total reduction of COD of 62 percent. The daily fluctuations in percentage COD reduction between inlet and outlet samples are graphically depicted in figure 4. 29 percent of samples displayed less then 50 percent of COD reduction, 41percent samples recorded COD reduction between 50 to 70 percent.

Figure 4: Performance of Biogas plant (COD reduction in % )

3.5 Biogas Generation

Biogas, a mixture consisting primarily of methane and carbon dioxide, is produced from dairy wastes through anaerobic digestion, a natural process that breaks down organic material in an oxygenfree environment and it is well documented process for treating organic waste (Dwaraka Kothapalli and Meena Vangalapati, 2010; Borzacconi et.al.1995; Lawson 1992; Ralph and Keith , 1990). Krisch and Sykes elaborated Barkers postulates and suggested involvement of two step conversion of organic matter to methane. Not only anaerobic digestion reduce the COD of an effluent, but also little microbial biomass is produced by the process. The biggest advantage is energy recovery in the form of methane and up to 95 percent of the organic matter in a waste stream can be converted in to biogas (Orhon et. al.1993). The gas generation fluctuated between .5m 3 /day to maximum of 4.5m 3 /day with an average of 3m 3 /day. The initial and middle lot of samples displayed uniform gas generation while the remaining samples displayed large fluctuations in gas generation (Figure 5).



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Figure 5: Performance of Biogas plant, Gas generation in m 3

3.6 Correlation of environmental parameter with amount of gas generation

Correlation of the amount of gas generated with temperature, pH, BOD and COD was accessed using scattered diagram (Figure 6, 7, 8, 9). pH and BOD seems to be positively correlated with the amount of gas generation. There was no change in the average value of temperature and pH at inlet and outlet point, but BOD and COD was reduced to the extent of 50%. All parameters, however, showed statistically significant differences at 5% level between inlet and outlet points (Table1). Qasim operated a completely mixed mesophilic digester at an organic loading rate of 3.2 kg / m3 / d and achieved a 52.9 percent volatile solids conversion to gas (Quasim, and Warren 1984). Murthy and Kulshrestha (1985) and Sambo et.al. (1995) reported the effect of pH and temperature and other operating parameters on production of biogas.

Table1: Values of paired t test for fluctuation of water quality parameter between inlet and outlet samples of dairy plants.

Parameters t values df t at 5% Significance

Temperature pH BOD COD

3.00 3.97 4.68 6.98

16231019

2.12 2.07 2.23 2.09

Significant Significant Significant Significant

4. Discussions

4.1 Temperature

Temperature is an important physical property and most important effluent parameter. Ahring et.al. (2001) studied the effect of temperature on performance and microbial population



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dynamics of an anaerobic reactor treating cattle manure. The effect of temperature on anaerobic digestion is of great importance because the rate of biochemical reactions is directly affected by temperature. There are two group of organism that can affect digestion, namely the mesophilic organism that works best in the temperature range 30 0 C to 38 0 C and thermophilic organism that thrive in higher temperature but have optimum reaction rates of 50 0 C to 60 0 C. Some studies have shown that thermophilic digestion is more tolerant to organic overloads than mesophilic digestion when immobilized reactor designs are used Ahring (1994), Harris et.al. (1993).

Figure 6: Correlation between Temperature and Gas generation.

4.2 pH

pH indicates the general condition of environment and for most digesters, a typical pH value of 6.5 to 7.6 is considered normal.

Figure 7: Correlation between inlet pH and Gas generation.

4.3 Biological Oxygen Demand and Chemical Oxygen Demand (BOD and COD)

BOD and COD are most important parameters. Richa Kothari et.al.(2011) reported that anaerobic process reduces the organic pollution load and brings down BOD to 9.4 40% and



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COD 3958% from original initial value. These are few examples of what can often be achieve (Figure 8 & 9).

Figure 8: Correlation between BOD and Gas generation

It is also recorded that 70.40 percent of COD removal at a flow rate of 0.006 m3/day for an Overall OLR of 1.265 Kg COD/m3 (Srinivasan et. al. 2009). Anaerobic digestion can convert a significant portion (>50%) of the COD to biogas, which may be used as an in plant fuel, and also saves the energy (Wilkie et.al. 2000).

Figure 9: Correlation between COD and Gas generation

Changes in parametric value of temperature, pH, BOD and COD seems to have influenced the amount of biogas generated. During the period of study, gas generation was steady during the first week followed by wide fluctuations in the following week with steady higher values of gas generation in the later half. High but fluctuating gas generation was recorded in the last week. pH and BOD correlated positively with the amount of gas generated. There was no



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change in the average values of temperature and pH at the inlet and outlet points. But BOD and COD was reduced to the extent of 50 percent. All parameters however displayed statistically significant at 5 % level between inlet and outlet point.

The results of this study carried out by Richa Kothari et.al. (2011) indicate that parameters of dairy industrial waste like BOD, COD, TS and TOC show a higher rate of % reduction in values after anaerobic digestion and simultaneously potential for biogas production in waste was also noticed.

5. Conclusion

Biogas is considered as renewable natural gas that can be produced by the controlled decomposition of dairy manure or similar waste products. Biogas can provide number of social and environmental benefits, especially improved energy security and it is an effective substitute for fuel wood and more environmental friendly.

Acknowledgement

This study was conducted at the Grasim Industries Ltd., Birlagram, Nagda, M.P. (India) and the authors would like to thanks the managers of HRD, Dr. T.K. Mandal and Dr. V.A. Ashtekar for providing the necessary permissions.

5. References

1. Ahring BK. (1994). Status on science and application of thermophilic anaerobic Digestion, Water Science and Technology, 30 (12), pp 241249.

2. Ahring, B. K. and Ibrahim, A.A. (2001). Effect of Temperature Increase from 55 to 65°C on Performance and Microbial Population Dynamics of an Anaerobic Reactor Treating Cattle Manure, Water Research, 35(10), pp 24462452.

3. Berg Van den, L. and Kennedy, K.J. (1983). Dairy waste treatment with anaerobic stationary fixed film reactors, Water Science & Technology, 15 (89), pp 35968.

4. Dwaraka Kothapalli and Meena Vangalapati (2010). Kinetic Studies on Dairy Wastewater Using Immobilized Fixed Bed Anaerobic Digester, International Journal of Chemical, Environmental and Pharmaceutical Research, 1(1), pp 15.

5. Borzacconi L., Lopez I. and Vinas M. (1995). Application of anaerobic digestion to the treatment of agroindustrial effluents in Latin America, Water Science and Technology, (32)12, pp 105–111.

6. Central Pollution Control Board (CPCB). (1997). National inventory of large and medium industry and status of effluent treatment and emission control system, New Delh CPCB, 1, pp 411 (Programme objective series PROBES/68/199798).

7. Harris W.L, and Dague R.R. (1993). Comparative performance of anaerobic filters at mesophilic and thermophilic temperatures, Water Environment Research, 65 (6), pp 764771.



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8. Lawson PS. (1992). Municipal solid waste conversion to energy, Biomass and Bioenergy. 2 (16), pp 319–330.

9. Murthy N. R. K. and Kulshrestha S.P. (1985) Effect of pH and temperature on biogas Production, Proceedings Silver jubilee convention, Indian Society of Agriculture Engineers 4, 13–19.

10. Orhon, D., Gorgum,E., Germirli, F., and Artan, N. (1993). Biological treatability of dairy Waste waters, Water Research, 27, (4), pp 635663.

11. Quasim, S. R. and Warren K. (1984). Methane Gas Production from Anaerobic Digestion of Cattle Manure, Energy Sources, 7(4), pp 319341.

12. Ralph S. and Keith R. (1990). Anaerobic digestion of crops and farm wastes in the United Kingdom, Agriculture Ecosystem & Environment, 30 (12), pp 85–95.

13. Richa Kothari, Virendra Kumar and Vineet Veer Tyagi (2011) ASSESSMENT OF WASTE TREATMENT AND ENERGY RECOVERY FROM DAIRY INDUSTRIAL WASTE BY ANAEROBIC DIGESTION, The IIOAB Journal, SPECIAL ISSUE ON ENVIRONMENTAL MANAGEMENT FOR SUSTAINABLE DEVELOPMENT, 2(1) pp 16.

14. Sambo A.S., Garba B. and Danshehu B.G. (1995) Effect of some operating parameters on biogas production rate, Renewable Energy, 6 (3), pp 343–344.

15. Srinivasan, G., Subramaniam, R. and Nehru kumar, V. (2009). A Study on Dairy Wastewater Using FixedFilm Fixed Bed Anaerobic Diphasic Digester, American Eurasian Journal of Scientific Research, 4 (2), pp 8992.

16. Tillamook (1999). Anaerobic digester a success at dairy farm, BioCycle, 40 (3),pp18.

17. Wilkie A.C, Riedesel K.J. and Owens J.M. (2000 a) Stillage characterization and anaerobic treatment of ethanol stillage from conventional and cellulosic feed stocks, Biomass and Bioenergy, 19(2), pp 63 102.

18. Wilkie, A. C. (2000 b). Reducing Dairy Manure Odor and Producing Energy, BioCycle, 41(9), pp 4850.

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Utilization a nd treatment of dairy effluent through ... · PDF file2.3.3 Characteristics of effluent Dairy waste is white in ... Dairy plant handles 4500 ... Utilization and Treatment