Kinetic Analysis of COD Removal from Actual Domestic Wastewater in an Expanded Granular Sludge Bed (EGSB) Reactor

Treatment of actual domestic wastewater at ambient temperature, even low temperature is considered to be difficult by traditional systems. The present study is related to treatment of actual domestic wastewater in an EGSB reactor. The study showed the effectiveness of biological treatment of actual domestic wastewater involving appropriate microorganism and granules in an EGSB reactor. At 26 degrees C, the reactor was operated at 18.7kg COD.m(-3).d(-1) of average organic loading and 83% high COD removal efficiency, and even at the highest loading rate of 57.12kgCOD.m(-3).d(-1), the COD removal efficiency still could attain to 68%. Varied influent flow need to supply varied optimal V-up and thus to ensure the optimal removal effect. Low temperature would cause pollutant removal rate decrease. However, enhancing V-up could optimize the contact of sludge and wastewater and thus strengthen the performance effect. Modified Stover-Kincannon model was applied to data obtained from experimental studies in EGSB reactor. Treatment efficiencies of the reactor were investigated at different hydraulic retention times (0.5-1.3h) and different operation temperature (15 degrees C, 26 degrees C). The modified Stover-Kincannon model was best fitted to the EGSB reactor, and the substrate utilization rate(U-max), saturation constant value(K-B), and actual pollutant removal rate(U-max/K-B) were found to be 1.7x10(5)g.l(-1)d(-1), 200g.l(-1).d(-1), and 8.5x10(2) for 26 degrees C, 1.0x10(5)g.l(-1)d(-1), 140g.l(-1).d(-1), and 7.1x10(2) for 15 degrees C (before increasing V-up), and 2.0x10(5)g.l(-1)d(-1), 240g.l(-1).d(-1), and 8.3x10(2) for 15 degrees C (after increasing V-up). Low temperature could cause U-max/K-B decrease and thus cause distinct decreasing of COD removal efficiency. However, increasing V-up increase U-max/K-B and accordingly increase COD removal efficiency.