Algal species penetrating water purification processes in the balkfontein purification plant

Abstract

Goldfield Water at Balkfontein purifies turbid, polluted water from the middle Vaal River for potable purposes. Algal species pentetrate the different phases of water purification. The main aim of the investigation was to determine the nature and extent of algal-related problems, the types of algal species involved as well as the relations between algae in the river water and algae in the different phases of the purification process. Algal species were identified and concentrations determined in order to compare the removal of algal species in relation to different treatment conditions, dosage concentrations of the different flocculants used. Different flocculants and other chemicals (for example ferri-chloride, ferri-sulphate, lime and chlorine) had different effects on algal removal. Representatives of six different algal groups were present in the river as well as in the water sampled at the different sampling localities. A reduction in algal biomass occurred in the different phases of the purification process. Synechococcus cedrorum, Synechocystis sp. (blue-green algae) and Monoraphidium arcuatum, Monoraphidium circinale and Carteria globosa (green algae) were the dominant penetrating algal species during the study period. The algal species identified from the different sampling localities were grouped into morphological groups. Unicellular groups penetrated the system more frequently than colonial and filamentous groups. The unicellular discoidal group was removed more efficiently than the other groups.