A series of batch treatability screening tests were conducted to identify technologies suitable for removal of ethylenediamine (EDA) and aquatic 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. Only cation exchange resin and bio-hydrolysis reduced effluent toxicity to the required limit. Continuous flow bench-scale activated sludge treatability tests were conducted over a four month period under simulated warm and cold weather operating conditions. The results confirmed that activated sludge treatment alone could consistently provide greater than 95 percent BOD reduction and complete EDA hydrolysis, nitrification and toxicity reduction. Toxicity reduction could be accomplished at high organic loading (F/M > 1.0/day) but hydrolysis of EDA caused an effluent NH3-N concentration of greater than 300 mg/L. A lower organic loading (F/M <0.30/day) was therefore selected to provide nitrification for compliance with the 25 mg/L NH3-N pretreatment limit. Alternatively, a high rate activated sludge system (F/M > 1.0/day) coupled with high pH air stripping of ammonia was considered in “desktop” evaluations. A detailed process design and cost estimate were developed.