STABILITY AND PERFORMANCE OF AN ANAEROBIC DOWNFLOW FILTER TREATING SLAUGHTERHOUSE WASTE-WATER UNDER TRANSIENT CHANGES IN-PROCESS PARAMETERS

An anaerobic downflow filter, operating at 35 degrees C, was used to t reat slaughter-house wastewater with an influent chemical oxygen deman d (COD) of 5050 mg/l. Start-up of the reader was achieved within 35 da ys by use of a regime that included stepped increases in influent COD and methanol substitution of the substrate. A steady state was achieve d with 94.5% COD reduction at an organic loading rate of 10.1 kg of CO D/day per m(3) (hydraulic retention time 12 h). This rate is significa ntly higher than the rates achieved in previously reported studies. Th e reactor was subjected to transient changes in temperature, pH, influ ent flow-rate and COD for 5 and 10 h periods. The quality of the efflu ent deteriorated under these shock load conditions, but returned to st eady-state values within 6-15 h when normal conditions were restored. The stability of the reactor under unfavourable process conditions Is discussed.