TREATABILITY STUDIES AND PROCESS DESIGN FOR TOXICITY REDUCTION FOR A SYNTHETIC-FIBER INDUSTRY

A series of batch treatability screening tests were conducted to ident ify technologies suitable for removal of ethylenediamine (EDA) and aqu atic toxicity in a wastewater discharge from a synthetic fiber plant. Air stripping, cation exchange resin, activated silica, macroreticular resin, granular activated carbon and bio-hydrolysis were evaluated. O nly cation exchange resin and bio-hydrolysis reduced effluent toxicity to the required limit. Continuous flow bench-scale activated sludge t reatability tests were conducted over a four month period under simula ted warm and cold weather operating conditions. The results confirmed that activated sludge treatment alone could consistently provide great er than 95 percent BOD reduction and complete EDA hydrolysis, nitrific ation and toxicity reduction. Toxicity reduction could be accomplished at high organic loading (F/M >1.0/day) but hydrolysis of EDA caused a n effluent NH3-N concentration of greater than 300 mg/L. A lower organ ic loading (F/M <0.30/day) was therefore selected to provide nitrifica tion for compliance with the 25 mg/L NH3-N pretreatment limit. Alterna tively, a high rate activated sludge system (F/M >1.0/day) coupled wit h high pH air stripping of ammonia was considered in ''desktop'' evalu ations. A detailed process design and cost estimate were developed.