RESPONSE OF AN ANAEROBIC FLUIDIZED-BED REACTOR TREATING ICE-CREAM WASTE-WATER TO ORGANIC, HYDRAULIC, TEMPERATURE AND PH SHOCKS

An anaerobic fluidized bed reactor, operating at 35 degrees C, was used to treat ice-cream wastewater with an influent chemical oxygen demand (GOD) of 5.2 g l(-1). Start-up of the reactor was achieved within 30 days by use of a regime that included stepped increases in influent COD and methanol substitution of the substrate. A steady state was achieved with 94.4% COD reduction at an organic COD loading rate of 15.6 g l(-1) d(-1) (HRT 8 h). This rate is somewhat faster than those achieved in previously reported studies. The reactor was subjected to transient changes in temperature, pH, influent flow-rate and COD for 6 and 12 h periods. The quality of the effluent deteriorated under these shock load conditions but returned to steady-state values within 6-16 h upon restoring normal conditions. The stability of the reactor under unfavourable process conditions is discussed.