Comparative Study of Two Packing Media for Anaerobic Filter Reactor for the Treatment of Cheese Whey

Abstract

India has emerged as the largest milk producing country in the world with present level of annual milk production estimated as 121.8 million tonnes in 2010-11. We expect a production level of 155 million tonnes by the year 2016-17. The industry had been recording an annual growth of 4% during the period 1993-2005, which is almost 3 times the average growth rate of the dairy industry in the world. The processing of milk not only yields various dairy and milk products but also generates some kind of waste or effluent. With the emergence of new techniques in the dairy industry, there lies a hidden responsibility for treatment of waste or effluent generated before its disposal.The strengthening of pollution control norms has forced the effluent treatment process to get more important for dairy industry. Now a day, the upgradation in the present techniques used for this treatment has gained importance. Anaerobic treatment process provides the advantage of energy production in form of biogas and less sludge production. In recent past, the process has earned more feasibility to cope up with the variability in effluent and rapid rate of its production after the development of several high rate reactors. Amongst these several high rate reactors, anaerobic fixed reactors are the one which combines the advantage of rapid start up, ability to withstand shock loads, tolerance to high ammonia and VFA levels, ability to adapt intermittent feeding, simple construction and lower installation cost. Hence, it was selected to study its applicability and evaluate the performance for treatment of dairy effluent. Whey is considered to be the most unmanageable effluent due to its higher organic strength, exihibiting a BOD5 values about 30,000 - 50,000 ppm and COD values about 60,000 - 80,000 ppm. Therefore, diluted cheese whey was selected to check the feasibility of anaerobic filter. An important constituent of anaerobic filter is the packing media. Two pilot scale models are installed that were identical in every aspect except the packing media in them. The reactors were named A and B for Brickbats media and Polypropylene biorings media, respectively. After working out their volume calculation and porosity, they were started and commissioned and then operated at different HRTs. The performance was evaluated and a comparison was made between the reactors. During the operation, the Organic Loading Rate(OLR) was increased in stepwise from 0.7 to 2.5 kgCOD/m3d and the Hydraulic Retention Time (HRT) shortened to 5 days. The COD removal efficiency was more favorable in B (78%) respect to A(60%). The biomass concentration in the reactor was 4400 mg/l and 6500 mg/l in A and B respectively. Under steady state conditions, the first-order, Stover-Kincannon and Grau-second-order kinetic models were used to represent the kinetics of organic matter removal in the anaerobic filter. The experimental data showed that the Grau kinetic models were the most suitable for predicting organic matter degradation.