2.IJAEST-Vol-No-8-Issue-No-1-“Bio-oxidation-of-Anaerobically-Treated-Dairy-Wastewater”-010-018

Yashika R. Deshmukh* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 8, Issue No. 1, 010 - 018

“Bio-oxidation of Anaerobically Treated Dairy Wastewater�

Yashika R. Deshmukh1, Dr.P.B.Nagarnaik2, A.P.Pittule3 1

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Student of M.Tech, Department of Civil Engineering, G.H.Raisoni College of Engineering, C.R.P.F. Gate No.3, Digdoh Hills, Hingna Road, Nagpur-440 016,(India) E-mail: yashika.deshmukh@gmail.com 2 Dean Academics, Department of Civil Engineering, G.H.Raisoni College of Engineering, C.R.P.F. Gate No.3, Digdoh Hills, Hingna Road, Nagpur-440 016,(India) 3 Deputy General Manager, Lars Enviro Pvt. Ltd., 218, Bajaj Nagar South Ambazari Road, Nagpur-440 010, (India) ABSTRACT

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Dairy industry is one of the major industries causing water pollution. In India, dairy industry generates about 6-10L wastewater/L of milk processed depending upon the process employed and product manufactured. The dairy industry in India is expected to grow rapidly and have the waste generation and related environmental problems. Poorly treated wastewater with high levels pollutants caused by poor design, operation or treatment systems creates major environmental problems when discharged to surface water or land. Wastewater generated in dairy contains highly putrescible organic constituents and almost all the organic constituents of dairy waste are easily biodegradable. The anaerobic digesters in first phase of treatment which is followed by high rate aerobic treatment remains as the most common effluent treatment method for dairy industry.

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The paper present initiated study the removal efficiency and performance of Extended Aeration Tank (EAT) for treating dairy effluent. The aim of this work is the study of Extended Aeration Tank treating dairy wastewater. The tank efficiency of treating dairy wastewater at organic loading rates was studied and its performance was assessed by monitoring pH, Dissolved Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD),Dissolved Oxygen (DO), Mixed Liquor Suspended Solids (MLSS) and Sludge Volume Index (SVI).The tank achieved COD, BOD removal efficiency was observed to be 77.53%, 88.52% and MLSS, SVI, DO values was observed that 5838.5mg/L, 94.10, 2.89mg/L. The pH of tank was found to be 6.7-7.5. The study demonstrated that the posttreatment of dairy wastewater effluent is required to meet the safe effluent disposal standards.

Keywords: Aerobic digestion, Dairy wastewater, Extended Aeration Tank

ISSN: 2230-7818

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Yashika R. Deshmukh* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 8, Issue No. 1, 010 - 018

In order to provide high-rate oxidation of organic pollutants, microorganisms must be provided with an environment that allows them to thrive. Temperature, pH, Dissolved Oxygen and other factors affect the growth of microorganisms and their rate of biochemical oxidation. The rate of bio-oxidation is a function of temperature.

Various microbial species have optimal temperatures for survival and cell synthesis. Psychrophilic microorganisms thrive in optimum temperature is 12° to 18°C,Mesophilic microorganisms thrive in optimum temperature is 25° to 40°C and Thermophilic microorganisms thrive in optimum temperature is 55° to 65°C. Overall, as temperature increases, microbial activity increases. Food to Microorganism Ratio (F/M) represents the mass of bio-available organic compounds (substrate) loaded into the aeration chamber each day in relation to the mass of microorganisms contained within the aeration chamber.

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An organic loading rate or a substrate removal rate parameter for the activated sludge process must be both microbiologically pertinent and practically applicable.The development of such a parameter requires the expression of the concentration and activity of the activated sludge microorganisms as well as the substrate concentration in the wastewater[3].

effluent and are retained within the ATU. The biological solids settle back into the aeration chamber where they serve as seed for new microbial growth. Settled biomass and residuals will accumulate in the bottom of the chamber and must be removed with periodic maintenance.

Because the biomass creates an oxygen demand, clarifier is an important part of generation a high- quality effluent the soluble BOD of the effluent is generally 5mg/L, but the biomass solids carry over may produce an effluent BOD of 20mg/L OR greater[4].

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1.0Introduction Water management in dairy industry is well documented [1], but effluent production and disposal remain a problematic issue for the dairy industry.

To enable the dairy industry to contribute to water conservation, an efficient and cost-effective effluent treatment technology has to be developed. To this effect, aerobic digestion offers a unique treatment option to the dairy industry. Not only does anaerobic digestion reduce the BOD of an effluent, but little microbial biomass is produced. Dairy industry uses 2 to 5 L of water per L of milk processed [2].

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1.2Aerobic Digestion Process

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Aerobic treatment units are high-rate oxidizers of soluble organic and nitrogenous compounds. From a biological perspective, aerobic treatment units (ATUs) do not employ any new processes that are not already utilized in large-scale wastewater treatment plants. In addition to the reduction of BOD by aerobic digestion and removal of nutrients, suspended solids and pathogens from the effluent. Primary treated wastewater enters the aeration unit and is mixed with dissolved oxygen and suspended and/ or attached microbes. The aerobic microbes convert organic compounds into energy, new cells and residual matter. As the water moves through the clarifier, a portion of the biological solids are separated out of the

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Typically this ratio is expressed in terms of mass of mass of BOD per day per mass of microbes in the treatment unit [5]. The

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Yashika R. Deshmukh* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 8, Issue No. 1, 010 - 018

1.2Extended Aeration Tank

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Extended aeration is characterized by long-term aeration, long detention times, low food to microorganism ratio, and low biomass accumulation. As shown in Fig.1, by providing plenty of dissolved oxygen and minimal soluble organic matter, the microbes will be in the endogenous phase of growth and will readily consume bioavailable organic carbon including biomass. The goal is to balance the mass of new cells synthesized per day with the mass of cells endogenously biochemicallydegraded per day.[6]suggests that for a treatment unit to operate in extended aeration, 2000 cubic feet of air should be injected in the water per pound of BOD5 removal.

application of substrate where biomass concentration changes in response to changes in substrate concentration.

Intermitted-flow, complex mix systems only operate over a small range on these curves because the concentration of substrate tends to be relatively constant.

Under substrate-limit conditions, microbes will feed on each other at higher rate than new cells can be produced. The aerobic degradation of cellular material is endogenous respiration.

Endogenous respiration is not 100% efficient and thus there is an accumulation of slowlydegradable cellular material and other residuals [7]. Aerobic treatment units employed in the decentralized wastewater management industry operate in the endogenous respiration phase. In extended aeration process at a low organic loading long aeration time, high MLSS concentration and low F/M ratio.

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influent pH has significant impact on wastewater treatment. [4] Report that it is possible to treat organic wastewater over a wide pH range; however the optimum pH for microbial growth is between 6.5 and 7.5. It is interesting to note that bacteria grow best at slightly alkaline water.

Similarly, algae and fungi grow best in slightly acidic water.

Fig.1 Kinetics of aerobic digestion As substrate increases, biomass increases.

These curves represent a “batch-style�

ISSN: 2230-7818

The BOD removal efficiency is high because of high detention in the aeration tank, the mixed liquor solid undergo considerable endogenous respiration and get well stabilized. The excesses sludge dose not requires separate digestion and can be directly dried on sand beds. Also the excess sludge production is minimum.

The oxygen requirement for the process is higher and running costs are also therefore high. The length of the tank depends upon the type of activated sludge plant.

Completely mixed plants the aeration tanks are designed as long narrow channels. The width and depth of aeration tank depend on the type of aeration equipment employed.

The depth controls the aeration efficiency and the width controls the mixing. The horizontal velocity should be around

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2.0 Materials and Methods 2.1Location of Industry

The dairy industry wastewater stream resulting from the washing operations at the Bhandara Co-operative dairy is unit of Bhandara Zilla Dugdha Utpadak Sahakari Sangh Maryadit Bhandara and was established in 25 July 2009 in Jamni Dabha, Bhandara Road, Bhandara. The dairy situated about 8 km from Bhandara was used in the present study. The unit processes ≈ 40,000 L of effluent every day.

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Since introducing of the activated sludge process in the early 1900s, many different types of subsurface or diffused aeration devices have been design and developed to dissolve oxygen into wastewater. Diffused aeration devices are usually classified as either fine or coarse bubble referring to the relative diameter of the bubble produced.

The demarcation between fine and coarse bubbles is not well defined [8, 9].

However, the improvement of the degree of treatment and consideration of nitrification has resulted in increased requirements for aeration system. Supply of oxygen constitutes a major operating cost for biological wastewater treatment systems. Many researchers [10, 11, 12, 13] contend that the potential economical design capabilities of the ASP have not been reached. It has been suggested that oxygen transfer limitations restrict the design of plant beyond the present accepted limit of loading. A diffused-air system consists of diffuser that are submerged in the waste water, header, pipe, air mains, and the blower and appurtenances through which the air passes. It consists of a tank with perforated pipes, tubes or diffuser plates, fixed at the bottom to release fine air bubbles from compressor unit. The tank depth is kept as 3 to 4 m and tank width is within 1.5 times its depth. If depth is more, the diffusers must be placed at 3 to 4 m depth below water surface. Centrifugal blowers are almost universally used where the unit capacity is greater than 425m3/ min of free air. Rated discharge pressure range normally from 48 to 62 kN/ m2. For higher

discharge pressure applications [> 55 kN/m2] and for capacities smaller than 425 m3/ min of free air per unit. Air piping consists of main valve, meter and other fitting that transport compressed air from the blowers to the air diffusers. Because the pressure are low [less than 70 kN/ m2], lightweight piping can be used. Piping should be sized so that losses in air header and diffuser manifold are small in comparison to the losses in diffusers [14].

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1.5m/s. tank free board is generally kept between 0.3 and 0.5m.The inlet should be design to maintain a minimum velocity of 0.2 mps to avoid the deposition of solids.

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2.2Extended Aeration Tank The Extended Aeration Tank used in the present study was made up of R.C.C. The working length, width and depth of the tank were 6.9m, 5.2m and 4.0m and volume of the tank was 143.52m3.

Kirloskar company material pipes was used into the tank and compressor unit is used Siemens Company 180 CMH. 2.3Analysis The sample pH was measured with HANNA instrument pH meter (accuracy Âą 0.01 pH units), Chemical Oxygen Demand (COD) of the samples were analysed by open reflux method in which the

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Yashika R. Deshmukh* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 8, Issue No. 1, 010 - 018

3.0 Result and Discussion

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10AM sample ranges from 7.52 – 7.7, at 1PM sample ranges from 7.53 – 7.67, at 3PM sample ranges from 7.54 – 7.73.

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adequately diluted sample was strongly digested in the presence of strong oxidant (K2Cr2O7) and was titrated against standard solution of ferrous ammonium sulphate. Biochemical Oxygen Demand (BOD) was assessed by direct method and the sample of Dissolved Oxygen (DO) was measured with HANNA instrument Microprocessor Dissolved Oxygen Meter (accuracy ± 1.5% full scale mg/L O2).

Settleability of the sample were measured by volumetric test by using imhoff cone and Total solids (TS) measured by drying the raw sample and filtered sample at 105°C, respectively[15]. All the chemicals were of analytical reagent grade unless otherwise stated. Distilled water in all – glass units of Borosil design, was used for all purposes.

Fig. 2:Variation in pH at Inlet of Extended Aeration Tank

3.1Treatability Study of the Extended Aeration tank

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The waste water collected from both the inlet and outlet of waste water processing unit was analysed to obtain seasonal variation in the different parameters concentration in the waste water. The test was performed at regular interval to explore the feasibility of treatment carried out over there.

The pH is the measure of the intensity of acidity or alkalinity and measures the concentration of the hydrogen ions in the water. Fig.2 shows the variation in pH at the inlet of Extended aeration tank for different time intervals at 10AM sample ranges from 6.9 – 7.05, at 1PM sample ranges from 6.92 – 7.09, at 3PM sample ranges from 7.05 – 7.13. Fig.3shows the variation in pH at the outlet of Extended aeration tank for different time intervals at

ISSN: 2230-7818

Fig.3: Variation in pH at Outlet of Extended Aeration Tank

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Fig.6 shows that the variation of Extended aeration tank SVI (Sludge Volume Index).

SVI is used to indicate setting characteristics of activated sludge and other biological suspension. The lower the SVI the better is the setting quality of the aerated mixed liquor. Likewise high SVI values indicate poor setting qualities.

Sludge with an SVI of 100 or lee is considered a good settling sludge. From the Fig.6 shows the observed value of SVI was 94.10.

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Fig.4 shows that the variation of Extended aeration tank DO (Dissolved Oxygen). The presences of adequate DO indicate the healthy condition of Extended Aeration Tank and healthy and active aerobic microorganism can be safely assumed to be present. From the fig. the DO value was given by 2.89 mg/ L.

Fig.4: Variation of EAT DO (mg/L)

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Fig.5 shows that the variation of Extended aeration tank MLSS it indicates the microbial population is present in tank. If microbial population is more i.e. MLSS is more then there are more chances of organic matter coming in contact with micro-organism and getting removed so treatment efficiency is more. From Fig.5 the average MLSS value was observed that 5838.6 mg/L.

Fig.5: Variation of EAT MLSS (mg/L)

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Fig.6: Variation of EAT SVI

Fig.7 shows that the variation of Extended aeration tank F/M Ratio. F/ M Ratio was the food to micro-organism ratio if F/M Ratio is the food available to microorganism decreases hence there is competition for substrate among the micro- organisms. For EAT standard value is given by the range of 0.1 – 0.05and Fig. 5.10 shows 0.02

Fig.7: Variation of EAT F/M Ratio

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Fig.8 shows that the average range of COD at inlet of Extended aeration tank was found to be 195.6 to 302.2 mg/L and outlet of extended aeration tank was found to be 61.00 to 90.90 mg/L and Fig.9 shows the COD % removal efficiency of extended aeration tank found to be 77.53%.

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Fig.10: Inlet and Outlet BOD Reduction of EAT

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Fig.8: Inlet and Outlet COD Reduction of EAT

Fig.9: Variation in COD efficiency of EAT Fig.10 shows that the average range of BOD at inlet of Extended aeration tank was found to be 52.50 to 96.00 mg/L and at outlet of Extended aeration tank was found to be 8.50 to 18.50 mg/L and in Fig.11 shows the BOD % removal efficiency of Extended aeration tank found to be 88.52%.

ISSN: 2230-7818

Fig.11: Variation in BOD efficiency of EAT 4.Conclusions The present work was successfully conducted for the treatability of dairy waste water using the Extended Aeration Tank as an aerobic tank. The main conclusions drawn from this study are: 1.The COD, BOD and TSS removal efficiency was observed to be 77.53%, 88.52% and 53.94% respectively.

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3.It was also observed that plant is working at the design efficiency even if there is variation in the concentration of parameter analyzed for determining the performance.

5. It was observed that working condition of Extended Aeration Tank is good.

Acknowledgement

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The authors gratefully acknowledge Bhandara Zilla Dugdha Utpadak Sahakari Sangh Maryadit, Bhandara and Lars Enviro Pvt. Ltd., Nagpur for their cooperation and support.

References

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1.Berg Van den, L. and K.J. Kennedy, (1983). “Dairy waste treatment with anaerobic stationary fixed film reactors”.

Water Science Technol., 15:pp. 359-68.

2. Amritkar S R, (1995). “ Introduction of anaerobic pretreatment in treating dairy effluents–A positive step towards conservation and co-generation of energy, Proc 3rd Intl Cong on appropriate waste management technologies for developing countries” (National Environmental Engineering Research Institute, Nagpur, India. pp.127-132.

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4.Benefield, L. D. and C. W. Randall.

1985. Biological Process Design for Wastewater Treatment. Ibis Publishing, Charlottesville, Virginia. Bounds, T. 2003.

Personal correspondence. Orence Systems, Inc. May 24 5.Crites, R. and G. Tchobanoglous. 1998.

Introduction to Environmental Engineering. McGraw-Hill, New York

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4.The consistency of reactor performance even when BOD loading is changed quickly over a wide range of values indicates the robustness of the system.

3.Clark L. Weddl and David Jenkins “The viability and activity of activated sludge” Sanitary Engineering Research Laboratory, University of California, Berkley, California, U.S.A., (Received 20 December 1969)

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2.The tank apper capable of treating the wash waters with a high degree of consistency even when the influent strength may vary due to across-the-week flow variations, shock loads, etc.

6.ASCE, 1977. Wastewater Treatment Plant Design, Manual of practice No. 36.

Lancaster Press, Lancaster, PA. 7. Reynolds, T.D. 1982. Unit Operations and Processes in Environmental Engineering. PWS-KENT Publishing Company, Boston 8.Richard, C. A.; Gordon B. Rattray; Paul, P. D. “ Air Diffusion Unit” J. Water pollution Control Fed, 1974, 46 (5).

9.Warriner R. and Brenner R. C., “ Oxygen Transfer 10.American Society of Civil Engineering, “ Wastewater Treatment Plant Design” WPCF Manual of Practice No. 8, ASCE Manual on Engineering Practice No. 36, Lancaster Press, Inc. Lancaster, Pa., USA, Third edition, 1991, Chapter 14, (Activated Sludge).

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11.Khudenko, B. M.; Shpirt E.: “Hydrodynamic Prameters of Diffused Air Systems” Water Research, 1986, 20(7).

12.Metcalf & Eddy, “Wastewater th Engineering” 4 edition Tata Mc Graw Hill Edition, New Delhi, 2003.

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14.Dr. Rjor, S. Rastogi, N. Singh, “Design and cost comparison of Extended aeration and SAFF for typical wastewater” Department of Biotechnology and Environmental Science, June 2009.

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13.Suschka J., “ Oxygenation in Aeration Tanks”, J. Water Pollution Control Fed. , 43 (1), 1971

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15.APHA, 1998. Standard methods for the examination of water and wastewater.20th American Public Health Association, American Water Works Association, Water Pollution Control Federation, Washington, DC.

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