Abstract
Using a biological treatment system with sponge cubes made of polyurethane foam, we succeeded in purifying wastewater with 400 to 1600 mg COD·L-1, that dealt with a fluorescent-penetrant-inspection (FPI) process. Such wastewater contains slowly -biodegradable organic matter and is usually treated by coagulation processes. Field tests in two factories conducted for two years demonstrated that more than 80% COD was removed using the biological process with hydraulic retention time of 4 days, and that more than 97% COD was removed in the total system using the same biological process including post-treatment with granular activated carbon (GAC). Coagulants were not used. The n-hexane extract, whose concentrations in the wastewater were between 50 and 200 mg·L-1, did not exceed 30 mg·L-1 in the effluent from the bioreactor or 3 mg·L-1 in the effluent from the GAC process. This biological system would be an alternative means of FPI wastewater treatment, which reduces chemical cost, the amount of secondary waste and the space needed for chemical tanks.
