1.IJAEST-Vol-No-8-Issue-No-1-“Biomethanation-of-Dairy-Waste-Water-Through-UASB-at-Mesophilic-Tempe

Monali Gotmare* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 8, Issue No. 1, 001 - 009

“Biomethanation of Dairy Waste Water Through UASB at Mesophilic Temperature Range�

Monali Gotmare1 , R.M.Dhoble2, A.P.Pittule3 1

M.Tech student IV sem ,Department of Civil Engineering , G.H.Raisoni college of engineering, C.R.P.F. Gate No.3, Digdoh Hills, Hingna Road, Nagpur 440016, (India) E-mail:monaligotmare@yahoo.com.

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Associate Professor, Department of Civil Engineering , G.H.Raisoni college of engineering, C.R.P.F. Gate No.3, Digdoh Hills, Hingna Road, Nagpur 440016, (India) 3

ABSTRACT

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Deputy General Manager,Lars Enviro Pvt.Ltd.,218, Bajaj Nagar South ambazari Road,Nagpur,440010, (India)

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In any dairy industry the quantity and characteristics of effluent is depending upon the extent of production activities, Pasteurisation to several milk products. Waste water 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. The Indian dairy industries is stated to have the growth at more than15% & poised to cross the 150 Million tones per annum.The requirement for milk & milk products are keep growing in steady pace, making a significant impact on the Indian agriculture domain. In dairy industry waste water produces from the operations of bottle, can and tanker washing, machinery and floor, the liquid waste in a dairy originates from manufacturing process, utilities and service section.

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The paper present initiated study the removal efficiency and performance of Upflow Anaerobic Sludge Blanket (UASB) Reactor for treating dairy effluent and biogas generation estimation. The aim of this work was to the study of a UASB reactor treating dairy wastewater. The digester 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), Total Suspended Solids (TSS) and Volatile Fatty Acids (VFA) and biogas production.The reactor achieved COD, BOD,TSS removal efficiency was observed 87.06%,94.50%,and 56.54% respectively. and the VFA/Alkalinity ratio varies from 0.28 to 0.43. The pH of reactor was found to be 6.9-7.1.

The average gas production and methane gas conversion at optimum conditions was observed to be 179.35 m3/day and 125.55 m3/day, respectively. The overall methane composition was noticed to be 75% of the biogas.This study suggests that the post-treatment of dairy waste water effluent is required to meet the safe effluent disposal standards.

Keywords: Anaerobic digestion, Biogas, Dairy wastewater, UASB reactor, Methane.

ISSN: 2230-7818

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Monali Gotmare* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 8, Issue No. 1, 001 - 009

Most of the literature data on the anaerobic treatment of dairy waste water in continuous systems are not detailed enough to allow the calculation of the conversion to methane of the removed COD. In order to obtain conversions to methane of the removed COD above 70% in continuous UASB reactors the maximum load is around 3.0 g COD/l/d and the HRT must be above 12 h [8]. This value for the maximum load is in accordance with other previous works on anaerobic treatment of dairy effluents [9, 10, and 11]. Other works on anaerobic treatment of dairy effluents in continuous reactors have reported a significant decrease in reactor performance or failure due to build up of organic matter inside the reactors [12,13] although no numerical data are presented for this accumulation.The intermittent feed operating mode was recommended for complex wastewater, specifically for dairy waste water[14].

The intermittent operation consists of an interruption of the reactor feed during a certain amount of time keeping the same (or a higher) operating temperature as during the feed period. In the feedless period time is allowed for the biological degradation of the adsorbed substrates thus eliminating or reducing the accumulation of organic matter in the sludge bed. This operating mode was successfully tested for dairy waste water [15].

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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, anaerobic digestion offers a unique treatment option to the dairy industry. Not only does anaerobic digestion reduce the COD of an effluent, but little microbial biomass is produced. The biggest advantage is energy recovery in the form of methane and up to 95% of the organic matter in a waste stream can be converted into the biogas [2]. Many high-rate digester designs are currently available and some have successfully been used for the treatment of dairy effluents.Lettinga and Hulshoff-Pol [3] reported the use of fullscale up flow anaerobic sludge blanket digesters in use worldwide.dairy industry uses 2 to 5 L of water per L of milk processed [4].

have contributed to highlight anaerobic systems for the treatment of sewage waste water [7].

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1.0 Introduction

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In recent years there has been a growing interest in anaerobic treatment of wastewaters.Compared to aerobic growth, anaerobic fermentation produces much less biomass from the same amount of COD removal[5]. Upflow anaerobic sludge blanket (UASB) reactor is a popular anaerobic reactor for both high and low temperature [6]. The UASB reactor is by far the most widely used high rate anaerobic system for anaerobic sewage treatment. In the case of a relatively low strength wastewater such as sewage, the hydraulic retention time rather than organic loading rate is the most important parameter determining the shape and the size of the UASB reactor. The several favorable characteristics of anaerobic processes, such as low cost, operational simplicity, low biosolids production and considerable biogas production, together with suitable environmental conditions

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The aim of present work to access the performance of intermittent operation of mesophilic UASB reactor for treating dairy effluent and biogas generation estimation.This assessment was made in terms of COD removal and its conversion to methane and in terms of the stability of the reactors when operated at the higher loads.

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Typically biogas is composed of methane (50–75%), carbon dioxide (25-50%) and varying quantities of water (H2O) and hydrogen sulphide (H2S) and Other compounds can also be found, especially in waste dump biogas: ammonia (NH3), hydrogen (H2), nitrogen (N2) and carbon monoxide (CO)[16].

Characteristics Flow pH Alkalinity

Typical value 165 to 200(m3/d) 7.1-8.2 800 to1500(mg/L)

Suspended Solids

1045 to 1800 (mg/L)

Total Dissolved 1100 to 1600(mg/L) Solids BOD 800 to 1000 (mg/L) COD

1400 to 2500 (mg/L)

3.0 Materials and Methods 3.1 Reactor

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To use the energy of the biogas, biogas appliances, such as gas stoves or gas lamps are required. Both special biogas appliances or pressure-kerosene and LPG (Liquefied Petroleum Gas) equipment are adapted [17]. Besides cooking stoves and lamps, biogas can also be used to run refrigerators, water heaters, radio, television, power engines or any other appliances when it has been transformed to electricity. An average small-scale biogas plant can save up to 4.7 tonnes of carbon dioxide emissions per year [18].In fact the contribution of a methane molecule to the greenhouse effect is 21 times greater than that of a carbon dioxide molecule [19].

Therefore burning methane, even though producing CO2, reduces its impact on the environment.

Table 1: Average characteristics of dairy industry wastewater

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1.1 Biogas production:

The UASB reactor used in the present study was made up of R.C.C.The working volume of the reactor was 120.12 m3. The reactor consisted of five sampling ports; one inlet, which was further diverged into four channels; one effluent outlet; two gas outlets and a gas-solid-liquid separator.

The feed loading rates were controlled with peristaltic pumps (Siemens Company 180 CMH).

2.0 Location of Industry

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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, and Bhandara.The dairy situated about 8 km from Bhandara.

The unit processes produced 40,000 L of effluent every day. The average characteristics of dairy industry are shown in Table 1.

Fig.1.Upflow Sludge Blanket Reactor (UASB) process flow diagram

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Efficiency of COD in UASB reactor

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4.0 Result and Discussion

Fig .2(a). Variation in flow & % removal

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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 adequately diluted sample was strongly digested in the presence of strong oxidant (K2Cr2O7) and was titrated against standard solution of ferrous ammonium sulphate. BOD was assessed by the direct method and volatile fatty acids (VFAs) were analysed by the Distillation method followed by titration with 0.1N NaOH with a phenolphthalein indicator.

Alkalinity was estimated by titrating the filtered sample with 0.02N H2SO4, using methyl orange as indicator. Total solids (TS) and Total Suspended Solids (TSS) were measured by drying the raw sample and filtered sample at 105°C, respectively [20]. 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.

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3.2 Analysis

4.1 Treatability Study of the UASB Reactor

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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.

Fig 2(a) & 2(b) shows that the reactor shown lot of resilence against the hydraulic load fluactuations.The % reduction of COD and BOD varied within narrow range during observed fluactuations in the hydraulic load. This indicates that the reactor is satisfactorily stabilised.

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Fig .2(b). Variation in flow & % removal

Efficiency of BOD in UASB reactor 4.2 pH

pH is the most important and principle operating parameter of anaerobic digestion. The most common feed pH was observed to be between 5.5 to 6.0.

However the recommended optimum pH for UASB reactor is between 6.9 to 7.4. pH of reactor was observed and found to be within this range during the studies.

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Monali Gotmare* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 8, Issue No. 1, 001 - 009

UASB reactor is expected due to straining effect of the formed granules. As shown in Fig.5, the average range of TSS at inlet of UASB reactor was found to be 478 to 844mg/L and at outlet of UASB reactor was found to be 273 to 366 mg/L. The slightly low efficiency of TSS removal is due to excessive turbulence in the UASB reactor; therefore, the likelihood of entrapping suspended and colloidal solids is reduced.

pH

at

inlet

of

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Fig.5. Reduction of TSS in UASB reactor

900 800 VFA/Alkalinity (mg/L)

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Fig.3.Variation UASB reactor

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Fig.3 shows the variation in pH at the inlet of UASB reactor for different time intervals At 10 am the range of sample for pH 7.33-7.63, similarly at 1 pm was found 7.4-7.83 and at 3 pm 7.27-7.49.and in Fig.4 it was observed that the variation in pH at the outlet of UASB reactor for different time intervals at 10 am sample ranges from 6.9-7.01, at 1PM sample ranges from 6.9-7.01 and at 3PM sample ranges from 6.97-7.13.

700

0.5

836.7

0.45 705.2 640.7

600

604.8

4.3 Total Suspended Solids (TSS) As per, literature the higher Total Suspended Solid (TSS) removal across the

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0.4 609.2 0.35

0.3

500

0.25

400

300 272.3 200

240.2

214.5

264.7

0.2

209.4

224.5

0.15 0.1

100

VFA (mg/L) Alkalinity (mg/L) VFA/Alkalin ity Ratio

0.05

0

Fig.4.Variation in pH at outlet of UASB reactor

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0

MONTH

Fig.6.Variation in VFA and Alkalinity in UASB reactor

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Monali Gotmare* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 8, Issue No. 1, 001 - 009

VFA and alkalinity together are the good indicators for evaluating the process stability of the anaerobic reactor. As reported by [31] if the ratio of VFA to alkalinity exceeds 0.8, the inhibition of methanogens occurs. On contrary, [32] and [33] have stated that, optimum ratio of VFA to alkalinity should be less than 0.3 or 0.4. Fig 6 shows variation in VFA & Alkalinity. It shows that the ratio varied between 0.28 to 0.43 which is well within favourable range.

4.5 BOD and COD

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The BOD and COD removal is generally high in the UASB reactor. It generally varies between 60 to 90% [24, 25].

Fig.7.Shows that the average range of BOD at inlet of UASB reactor was found to be 765 to 1420mg/L and at outlet of UASB reactor was found to be 52.5 to 96 mg/L and BOD % removal efficiency of UASB reactor found to be 88 to 94% which is satisfactory as per performance of the reactor refer [24,25].

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4.4 Volatile Fatty Acid (VFA) and Alkalinity

Fig.8.Shows that the average range of COD at inlet of UASB reactor was found to be 1288 to 2262 mg/L and at outlet of UASB reactor was found to be 195 to 302 mg/L and COD % removal efficiency of UASB reactor was found to vary 78 to 87 %.

Fig.7.Reduction of BOD in UASB reactor

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Fig.8.Reduction reactor

of COD in

UASB

The performance of the reactor as judged on the basis of COD removal efficiency was found satisfactory (COD removal more than 80%) [26] and the reactor achieved treatment efficiency of the order of 75-85% and were able to withstand shock-loads without adversely affecting the treatment efficiency[27]. This indicates that the performance of the UASB reactor is satisfactory.

5.0 Biogas Generation The maximum and minimum average Biogas obtained was observed to be 179 m3/d and 100 m3/d as shown in the Fig.9.

The biogas operation observed to vary depending on the feed rate.

Methane content of 75-80% and 75% was observed working on methanolic wastes and dairy wastes [28]. The rest of the gas content is mainly carbon dioxide, because these two gases, methane and carbon dioxide are produced during anaerobic digestion.

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Monali Gotmare* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 8, Issue No. 1, 001 - 009

A portion of hydrogen gas is also produced if the system is not working properly due to the presence of hydrogen-producing acetogens, which will provide unfavorable conditions for the conversion of volatile fatty acids to acetate other than to methane.

reactor. The waste water flow from the processing unit is highly fluctuating.

In present study the methane was observed as about 70% of the biogas. The lowest gas composition of methane can be attributed to the recalcitrant properties of the substrate which is mainly composed of lignin. An average gas generation rate calculated is was 0.5m3/KgCOD removed.

3. The reactors 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.

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

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4. The VFA/Alkalinity ratio varies from 0.28 to 0.43. The pH of reactor was found to be 6.9-7.1. VFAs and pH are good indicators for the performance of UASB reactor. Acetate and propionate, products of lactose fermentation, were found to be the predominant intermediate metabolites in the UASB reactor and their concentrations were strongly dependent on the temperature and the organic load.

Fig.9. Biogas and methane production in UASB reactor 6.0 Conclusions

The present work was successfully conducted for the biogas production and treatability of dairy waste water using the UASB bioreactor as a anaerobic bioreactor. The main conclusions drawn from this study are:

5. The reactor achieved COD, BOD, TSS removal efficiency was observed to be 87.06%, 94.50%, and 56.54% respectively.

It was observed that working condition of UASB reactor is satisfactory.

6. 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.

7. The average gas production and methane gas conversion at optimum conditions was observed to be 179.35 m3/day and 125.55 m3/day, respectively.

The overall methane composition was noticed to be 75% of the biogas. The biogas generation from UASB reactor was less in amount but it can be use for different purposes as a source of energy generation in plant.

1. The loading rates applied during start-up and steady state operation control the characteristics of sludge developed in the

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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.

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Acknowledgement

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