Vehicle washing as a source of organic pollutants in municipal wastewater

Effluent wastewaters from a large number of automatic vehicle washing facilities in Göteborg have been analysed for conventional parameters (COD, oil content) and for individual organic pollutants using GC-MS. The identified pollutants encompassed short-chain paraffins, substituted benzenes, glycol ethers, phthalates, adipate, tributyl phosphate, bi- and polycyclic aromatic compounds and nonylphenol. While the volatile hydrocarbons, ethers and nonylphenol were discharged through the use of petroleum based degreasing formulations and washing agents, dirt/dust particles and traffic grime contributed to a large extent to the origin of bicyclic aromatic compounds, PAH's and phthalates in the effluent wastewater. A material balance study did not show the elimination of the organic pollutants in the oil separator, probably due to the formation of stable emulsions. Although the wastewaters from vehicle washing facilities exhibited a relatively high content of organic pollutants their estimated contribution to the total load on the municipal sewer in Göteborg was, with the exception of naphthalene, very low.