REMOVAL OF POLYCYCLIC AROMATIC-HYDROCARBONS AND HETEROCYCLIC NITROGEN-COMPOUNDS IN A MUNICIPAL TREATMENT-PLANT

Emissions of polycyclic aromatic hydrocarbons (PAHs) and heterocyclic nitrogenous compounds (HNCs) were measured at a publicly owned treatme nt works (POTW) receiving a dry weather flow (DWF) of 409 ML/d. Sample s of raw sewage, primary and secondary effluents were monitored over t hree sampling periods and were screened for 16 PAHs and 24 HNCs. The P AHs tended to partition to the solid phase while the HNCs were predomi nantly found in the liquid phase. Higher levels of PAHs were observed in the raw wastewaters than typically seen at POTWs, suggesting the in fluence of industrial discharges. Despite removal efficiencies of 98.3 % for PAHs and 96.3% for HNCs, average daily effluent mass discharges of 0.2 kg PAHs/d and 1.0 kg HNCs/d were measured. A fate of contaminan ts model, Toxchem, was used to forecast the impact of different proces s strategies for minimizing the discharge of PAHs. Analysis suggested that increases of up to 50% in primary or secondary clarifier capacity would not likely improve PAH capture. A 100% increase in the solids r etention time of the activated sludge system similarly would not likel y improve PAH removal.