Die effek van bakteriee en swaarmetale in behandelde rioolwater op die baber

Thesis

Health risks associated with the utilization of waste water for fish production were studied by investigating the possible incorporation of pathogenic micro-organisms and heavy metals into ftllets of fish. Fish were grown in cages in a stabilization pond at the Bloemspruit sewage works, while another group of fish was kept in a similar cage in the Krugersdrift dam. Water and fish were analysed for total and faecal coliforms, Salmonella, colifages and Escherichia coli. Chemical analyses were also conducted on the water and fish for heavy metals and related trace elements. Even though high numbers of faecal coliforms and colifages were detected in the treated waste water, and in some instances Salmonella was isolated, none of these micro-organisms were found in fish fillets. Concentrations of heavy metals showed no toxic evidence in fillets although chromium might be of some concern in future, should the concentration of the metal Increase. Results of this study indicate that fillets of Clarias gariepinus grown in treated waste water like the water of the Bloemspruit sewage works, are microbiologically and chemically safe for human consumption, provided that simple precautions are maintained in food-handling and -processing. The ponds are restricted to domestic waste with a minimum of industrial waste. The fish in the Krugersdrift dam are also microbiologically and chemically safe for human consumption, although the concentrations of chemical compounds were generally higher in fillets of this fish group. Urgent attention must be given to the maintenance of stricter control of natural waters to prevent water pollution in this catchment area.