Performance evaluation of Activated Sludge Process in Dairy Waste water TreatmentPerformance evaluation of Activated Sludge Process in Dairy Waste water Treatment
Abstract
Wastewater from dairy industries generally has oils and greases in high concentration and contains high concentration of biochemical oxygen demand (BOD) and chemical oxygen demand (COD). This experimental study is being initiated to evaluate an Activated Sludge Process (ASP) with mixed bacteria for dairy waste water treatment. A three phase study was carried out by varying hydraulic retention time (HRT). The study is being undertaken in two steps in which the bacteria is being cultured in a medium by the process of acclimatization. The later stage will be the determination of the operating parameters. The characteristics of dairy industry waste water were studied and the performance was analyzed. A lab-scale ASP was set up for the study of the performance in treatment of effluent. The effect of various aeration time phases were analyzed in the lab scale Aeration Process for the HRT time of (2, 4, 6) hrs respectively. ASP efficiently removes BOD, COD and nutrients when designed and professionally operated according to local requirements. From the effects of various HRT, the 6 hrs HRT was more efficient in removal of the organic matter. The removal efficiency of COD, BOD and TSS were 97%, 97.5% and 96% respectively. In this process all the parameters were within the standard discharge limits. Hence, the enhancement of organic removal from dairy effluent using ASP was found feasible
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Introduction
A dairy industry processes the raw milk received from farmers so as to extend its marketable life or to prepare dairy products such as butter, cheese, yogurt etc. The two main processes are involved in the industry are pasteurization and homogenization. Pasteurization is the process of heating up milk either to 62° C for 30 minutes or 71° C for 15 seconds and then quickly cooling it down to 4°C. It eliminates the presence of certain bacteria such as Salmonella, E.Coli and Listeria which may be present in unpasteurized milk. Homogenization is a process which breaks down the fat molecules in milk so that they resist separation. The dairy industry is one of the largest sources of wastewater generation. The volume of waste generated from it is around one to three times the volume of milk processed in the industry. Roughly, every year around 3.739 to 11.217 million m3 of waste is generated from the milk industry. As the demand for milk is increasing in all the countries, the dairy industry is flourishing which ultimately leads to an increase in the generation of dairy wastewater.
Conclusion
The enhancement of COD, BOD removal from the dairy effluent by the ASP process was found feasible and was in the range of 80 to 96 % and the HRT of 6 hrs was found to be more efficient. The process of acclimatization was found to be more feasible in the development of bacteria in this study.