Anaerobic Treatment of Industrial Wastewater under Psychrophilic Conditions (10 °C ) using Upflow Anaerobic Sludge Blanket (UASB) reactor, Lab Studies.

Abstract

The main objective of this study was to investigate the performance of UASB reactors for their efficiency of removing COD and producing methane gas at psychrophilic temperature, 10 °C by treating high strength municipal wastewater ranged from 500 – 1600 mg COD/l, received from the effluent from DAF unit at IVAR Grødaland WWTP. The study also included to investigate if UASB treatment would be a better option to apply prior to SBR unit at Grødaland WWTP for the removal of dissolved COD. All the thesis work was done on the laboratory scale at University of Stavanger. Two In-house designed Upflow Anaerobic Sludge Blanket, UASB reactors Reactor I and Reactor II that had been in operation for a year were used in this study. The organic loading rate (OLR) was variable in both reactors throughout the experimental period. The flow rate in Reactor II was purposely increased, 20 % to investigate its effect on methane gas production and COD removal efficiency. The gas meters were not functioning properly during parts of the study, therefore, the gas production values were estimated from Day 24 in Reactor I and from Day 28 in Reactor II, for calculations. The hydraulic retention time (HRT) in Reactor I and Reactor II varied from 6 – 14 h and 5 – 14 h, respectively. The pH in Rector I was between 7.2 – 7.8 while in Reactor II it was between 7.2 – 7.6 throughout the experimental period. The results obtained indicate a significant amount of methane production and COD removal efficiency. The maximum methane production achieved at psychrophilic temperature in Reactor I was 0.21 l CH4/l.d, which is 0.37 l CH4/g COD at OLR of 1.0 g/l.d and in Reactor II maximum methane production achieved was 0.23 l CH4/l.d which is 0.29 l CH4/g COD at OLR of 1.8 g/l.d. The average COD recovery achieved in both the reactors was 78 % with average COD removal efficiency of 56 % at 10 °C. There was a little deviation in results due to the equipment error otherwise, the results obtained indicate that anaerobic treatment using UASB technology to treat high strength wastewater to remove dissolved COD prior to SBR unit at IVAR Grødaland WWTP would be an attractive and feasible option even at psychrophilic temperature. By using a longer HRT and sludge retention time (SRT) and appropriate gas measuring meters the economically valuable methane gas can be produced and achieved.