Efficiency of a Pilot-Scale Waste Treatment System to Reduce Toxicity of CTMP Effluents, 1990 Environmental Conference Proceedings

Pilot-scale waste treatment systems have shown that CTMP pulp and paper mill effluents can be treated by aerobic and anaerobic waste treatment systems but consistent reduction of toxicity has been difficult to achieve. Raw CTMP effluents contain high BOD, sulfite, and resin acid concentrations which can reduce treatment efficiency as well as exert an organic demand and a toxic effect upon stream and lake biota after effluent discharge. The chemical characteristics of CTMP effluents depend upon the wood species and mill process conditions. The resin acid content is highly correlated with effluent toxicity. Ninety six-hour LCso concentrations range from 0.4-1.1 mg/L.

A pilot-scale Carrousel oxidation ditch effectively treated two different CTMP effluents. Over a 30-day period, we typically obtained 95-97% BODs removal. Resin acids were reduced to undetectable levels (mg/L). Color and pH increased as a result of biotreatment. Raw mill effluent ranged in toxicity from 0.31-0.51% (96-hr LC50) while toxicity was nearly completely removed by biotreatment. Remaining toxicity was attributed to low concentrations of ammonia and nitrite. Reduced feeding of ammonium hydroxide to the system lowered ammonia levels in the effluent below that considered toxic and we inferred that the remaining toxicity was associated with nitrite.