Biological dehalogenation of kraft mill wastewaters

A single-stage aerobic biological treatment system was developed specifically to convert organically bound chlorine to inorganic chloride. In initial laboratory tests, greater than 90% reduction of AOX was achieved in synthetic dichlorophenol, commercial pentachlorophenol, and combined kraft wastewaters, and less than a week was required for startup/acclimation. A six-month field test of the process on a pentachlorophenol wastewater was very successful under highly variable influent conditions. No chlorinated byproducts were detected, and measurements strongly indicated that dehalogenation had occurred. Recent experiments found Cl/El wastewater to be most easily treatable by the aerobic process, followed by combined lagoon influent, El wastewater, and finally lagoon effluent. However, results have indicated that application of the treatment process to kraft AOX reduction can become feasible only if further process improvements can be defined.