Treatment of solids and petroleum hydrocarbons in storm runoff with an on-site detention basin

Storm generated runoff pollution in urban areas is a significant problem for water quality planners. Previous studies have characterized the inorganic and organic constituents in urban runoff (Pitt 1979 and Hoffman et al. 1982 and 1983), and it was shown that many of these pollutants are susceptible to quiescent settling and removal from the water column. Whipple and Hunter (1980) showed that for suspended solids and suspended hydrocarbons, 70% and 65% respectively, of the initial concentration settled out after 32 hours. Metals closely associated with suspended solids (e.g. lead) settled out more than those less associated with the solids (e.g. copper, nickel, and zinc). Finnemore and Lynard (1982) indicated that detention basins, either natural or manmade, are comparatively inexpensive management practices for the control of urban runoff pollution. The present study assessed a detention basin for its effectiveness in treating petroleum hydrocarbons, polycyclic aromatic hydrocarbons and suspended solids from runoff at a shopping center parking lot. MATERIALS AND METHODS Influent and effluent samples from a small detention basin that serves a large shopping center pa~king lot in Seekonk, MA were collected in April and June, 198~. The basin is quasi-rectangula r in sha~e with an area of 0.003 Km L and a volume of approximately 3790 m ~ The total area drained is 0.05 km z. Runoff samples (4 I) were collected in a metal bucket and immediately transferred to precleaned glass solvent bottles where they were stored for up to 48 hours. Samples were collected simultaneously at the influent and effluent outfalls at intervals that varied from a few minutes to hours, depending upon flow conditions at the influent. Flow velocity was measured electronically with a Marsh-McBirney (Model 201) flow meter and multiplied by the crossectional area of the influent outfall to calculate the flow rate. Cumulative rainfall measurements were read from a standard rain gauge located on site. Procedures for analyses of runoff samples for petroleum hydrocarbons (PHC) are given in Hoffman et al., 1983. Briefly, samples were filtered through preweighed, precombusted glass fiber filters. Filters and filtrates were individually extracted with