PHYSICOCHEMICAL BEHAVIOR OF POLYNUCLEAR AROMATIC-HYDROCARBONS IN PRIMARY SEDIMENTATION .1. BATCH STUDIES

In this, the first part of a combined laboratory/pilot plant study int o the behaviour of Polynuclear Aromatic Hydrocarbons (PAH) during wast e water treatment, laboratory experiments were conducted to investigat e the effect of primary sedimentation on PAH removal from law sewage. Losses of 14 PAHs due to settlability, volatilisation and photodegrada tion were quantified. PAH particle size distributions in sewage we als o reported. Sedimentation resulted in PAH removal rates from raw sewag e ranging from 35% for acenaphthylene to 86% for benz(a)anthracene. Re moval rates increased with increasing molecular weight and the associa tion of a PAH with sewage particulate matter was found to correlate wi th the compound's log K-OW value. Association of PAH with sewage parti culate matter was greatest for the smallest particle size fraction (0. 45 to 53 mu m). PAH associated with the dissolved/colloidal phase in r aw sewage (the size fraction < 0.45 mu m) were enriched in the compoun ds with the lowest molecular weight. The removal of PAK from raw sewag e by volatilisation or photodegradation over the comparitively rapid p rocess of primary sedimentation is minimal compared to sedimentation.