Performance Study On Inverted Anaerobic Sludge Blanket Reactor For High Fat Content Wastewater

Abstract

In dairy wastewater treatment, Fat, Oil and Grease (FOG) have been an ever-growing environmental concern.  Because, FOG is considered hard to treat with current biological systems as having susceptibility to float, in due course solidifies and deposits on the ramparts of the pipeline, reactor and causes obstruction. Consequently, restricts the oxygen transfer in the conventional aerobic treatment. FOG is usually produced in food service establishments, discharge from slaughterhouse, palm oil mill effluents, dairy industry effluents, automobile workshop, etc. In our country, even though a many research works were carried out in treating a low strength to very high strength wastewater, considerable landmark is not achieved in FOG removal/ treatment. It is a well-recognized fact that anaerobic digestion is an energy recovery process, where the organic matters are converted into methane, a renewable energy which can be upgraded to bio-methane, removing CO2. This present study aimed to recover and enhance biogas production from wastewater rich in FOG, under anaerobic condition in a specially designed reactor named as Inverted Anaerobic Sludge Blanket (IASB) reactor exclusively for treating wastewater rich in FOG concentrations. The effects of varying organic loading rate (OLR) and hydraulic retention time (HRT) on the performance of the reactor treating fat rich dairy wastewater having chemical oxygen demand (COD) and fat content ranges between 1980 to 3320 mg/L and 50 to 140 mg/L, respectively were investigated in a bench scale reactor with an effective volume of 12 L operated at an ambient temperature 26 to 380C for 100 days including startup period of 52 days. After stabilization, the reactor was operated at different HRTs of 24, 18 and 12 h with OLRs 3.1, 4.3 and 6.2 Kg COD/ m3.d, respectively. A maximum COD removal of 92.4 % and corresponding fat removal of 92.1 % was achieved. Concurrently, the biogas generation of 11.6 L/d (331 L/ kg COD removal) was observed at 24 h HRT. The ratio VSS/TSS of the sludge increases gradually from 0.33 to 0.38 at the end of the study showing the growth of microbes.  Morphological examination of sludge also confirms the presence of Escherichia coli, Bacillus.sp, Kelbsilla.sp, Enterococcus.sp and Streptococcus.sp. The quality of the effluent found to be agreeable for irrigation, aquaculture or industrial use as it is anticipated that recycling of water will play a major role in meeting upcoming water shortages.