Storm runoff quality in a residential catchment in Malaysia

This paper examines the storm runoff quality from a medium cost residential area in south Johor, Malaysia. The quantity and quality of storm runoff during nine storm events were investigated. A total of 101 storm runoff samples were analyzed for total suspended solids (TSS), biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and oil and grease (O&G). The ranges of event mean concentration (EMC) were 2.09-70.27 mg/L for TSS, 2.27-15.21 mg/L for BOD5, 15.86-47.93 mg/L for COD, and 1.25-5.55 mg/L for O&G. These gave site mean concentrations of 40.62 mg/L, 6.67 mg/L, 27.53 mg/L, and 3.07 mg/L for TSS, BOD5, COD and O&G, respectively. The pollutographs of all pollutants showed peak concentrations preceded the peak flow of runoff. EMCs for all constituents also show large inter event variation. Correlation analysis showed that only rainfall intensity has significant influence on the EMC of O&G and TSS in storm water runoff. The EMCs of BOD and COD were influenced by antecedent dry days. All pollutant constituents show the occurrence of first flush, indicating that higher mass loading was delivered during the early part of the storm runoff.