Publication Abstract

Behaviour and fate of polychlorinated biphenyls in a pilot waste water treatment plant

S. Morris and J.N. Lester

The distribution and fate of polychlorinated biphenyls (PCBs) have been studied in a pilot wastewater treatment facility, utilizing conventional unit treatment processes to treat combined industrial and domestic wastewaters. Samples of influent, effluent and sludges were obtained from three configurations of the pilot plant and PCB concentrations were determined by gas liquid chromatography with electron capture detection (ECD). An evaluation of the performances of biofiltration and activated sludge units operating in series and in isolation was conducted. Influent PCB concentrations ranged from < 5 to 350 mu g/l. Commercial Aroclor formulations were detected in treated wastewaters and sludges. Estimated influent masses varied between 0.4 and 1.3 g total PCB/d at a flow rate of 22 m super(3)/d. Primary sedimentation removed approx. 45% of the PCB load. Concentrations in primary sludges ranged from 8.7 to 659.3 mg/kg. A simplified mass balance across primary sedimentation indicated potential sources of sampling and analytical error which were exacerbated by the complex chemical nature of the influent. PCB removal across combined secondary biofiltration achieved a mean level of 99%. Biofiltration alone, attained a removal efficiency of 90% and activated sludge treatment eliminated 96%. Typical concentrations in activated sludge ranged from 1.6 to 5.4 mg/kg dry weight. Final effluent loadings approximated to 0.01 g total PCB/d. An order of magnitude reduction was recorded across the pilot plant in all combinations with residual PCB discharge being associated with fine, non-settleable particulates.

Reference:

S. Morris and J.N. Lester, 1994. Behaviour and fate of polychlorinated biphenyls in a pilot waste water treatment plant. Water Research, 28(7): 1553-1561.