An evaluation of the water quality and toxicity of wastewater at selected car wash facilities in Tshwane, Gauteng

Abstract

Car washing consumes large quantities of water and results in large amounts of wastewater effluent being generated, but has received little attention as a potential source of water pollution globally. The study investigated the water use, wastewater effluent quality and toxicity of selected carwashes in City of Tshwane. Ten carwashes in the City of Tshwane were purposively selected and analysis done on a variety of water quality aspects including microbiological, toxicity, BOD,COD, oil and grease, anionic surfactants, sulphates, phosphates and heavy metals. The results obtained show that oil and grease exceeded the WHO and National Water Act standards of 2.5mg/L in all sites except CW2 and Diesel range organics were significantly high in some sites (CW4, 7 & 8) at 60.5, 40 and 48.8mg/L. COD and BOD of the waste water exceeded the WHO standards of 30mg/L and 60mg/L in all sites except CW2. Bacteria contamination was very high in all wastewater samples and all samples exhibited (mild to high) toxicity to Vibrio fischeri and high toxicity to Daphnia pulex except CW2. These results suggest that wastewater from carwashes is high in some pollutants that may interfere with the receiving environment and municipal treatment systems and there is a need for responsible authorities to regulate the quality of effluent discharged into the environment