Urban effluent discharges as causes of public and environmental health concerns in South Africa's aquatic milieu.

Abstract

The water quality in South Africa's river systems is rapidly deteriorating as a consequence of increased discharge of wastewater effluents. The natural ability of rivers and reservoirs to trap toxic chemicals and nutrients in their sediments enables these systems to accumulate contaminants, altering the natural balance in environmental water quality, thereby raising a plethora of public and environmental health concerns. Impaired water quality has been linked to an array of problems in South Africa including massive fish mortalities, altered habitat template leading to the thinning of riverine macroinvertebrate diversity, shifts in microbial community structures with drastic ecological consequences and evolvement of antibiotic resistance genes that, under natural conditions, can be transferred to waterborne pathogens. Urban wastewater discharge has also been implicated in increased bioaccumulation of metals in edible plant parts, elevated concentrations of endocrine-disrupting compounds (EDCs), which are blamed for reduced fertility and increased cancer risk, excessive growth of toxic cyanobacteria and an increase in concentrations of pathogenic microorganisms which constitute a potential health threat to humans. However, despite the ecotoxicological hazards posed by wastewater effluents, ecotoxicological studies are currently underutilised in South African aquatic ecosystem assessments, and where they have been done, the observation is that ecotoxicological studies are mostly experimental and restricted to small study areas. More research is still needed to fully assess especially the ecotoxicological consequences of surface water pollution by urban wastewater effluents in South Africa. A review of the effects of urban effluent discharges that include domestic effluent mixed with industrial effluent and/or urban stormwater run-off is hereby presented.