Naturally occurring fecal coliforms and fecal streptococci in Hawaii's freshwater streams

Abstract

Abstract The recreational quality of stream water in Hawaii was assessed by carefully analyzing stream, sewage, cesspool, and storm drain samples for concentrations of fecal coliform (FC), fecal streptococcus (FS), and selected physical and chemical parameters. High concentrations of FC, far in excess of the recreational water quality standard of 200 FC/100 mL, could be readily recovered from streams with no obvious sources of pollution and increased dramatically as the stream flowed through urbanized areas. Since sewage and cesspool wastes were characterized by a high (>4) FC: FS ratio, whereas stream water and storm drain samples had a low (<0.7) FC: FS ratio, it was concluded that the source of indicator bacteria in streams was not sewage or cesspool but most likely land runoff. The concentrations of indicator bacteria in treated sewage effluent being discharged into streams were determined to be much lower than the concentrations present in the receiving stream water. Thus, the impact of sewage effluent discharge into the streams of Hawaii cannot be properly evaluated by analyzing stream water samples for FC as mandated by law. Concentrations of orthophosphate, which is low in streams and high in sewage, was determined to be a reliable indicator for the presence of sewage effluent in streams.