Sugar wastewater treatment with aerated fixed-film biological systems

Wastewater effluents from the sugar industry contain high concentrations of organic materials which are sometimes discharged into the municipal wastew ater collection system:and processed in wastewater treatment plants along w ith domestic wastewater. This study examined the performance of a four-comp artment, fixed-film system in which the biofilm is attached to submerged ce ramic tiles under diffused aeration, known as the aerated submerged fixed-f ilm (ASFF) process. Field experiments were conducted using four ASFF units each of about 100 1 capacity operated at different hydraulic loading rates to provide hydraulic residence time (HRT) of 2, 4, 6 and 8 hours. Process p erformance was evaluated under both normal operation with domestic wastewat er and under pulse and prolonged organic shock loads with sugar wastewater. The influent and effluent of the process was analyzed for solids, BOD, GOD , and nitrogen forms to determine both carbonaceous and nitrogenous substra te removal. The ASFF process was found to be able to handle continuous seve re organic loads increasing from about 5 to 120 g BOD/m(2).d with slight de crease in organic removal efficiency from 97.9% to 88.5% for BOD and from 7 3.6 to 67.8% for GOD. Nitrification was similarly decreased but at higher r ates. The system was also able to cope with pulse injection of sugar wastew ater and recovery to normal steady-stale COD values was achieved in 10 hour s for the 200 g COD/1 spikes, An increase in the organic loading rate was a ccompanied by an increase in biofilm specific oxygen uptake rate until reac hing a maximum which determines the optimum loading rate for process operat ion. Substrate removal rates were evaluated for process design. (C) 1999 Pu blished by Elsevier Science Ltd on behalf of the IAWQ; All rights reserved.