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 runoff is hereby presented.

Mucociliary transport, differential white blood cells, and cyto-genotoxicity in peripheral erythrocytes in fish from a polluted urban pond

“…Changes in ammonia, hardness, and conductivity levels have been frequently associated with the input of sewage and/or urban storm water runoff, sources which are considered complex mixtures containing many toxic compounds, such as organic substances, pharmaceuticals, personal care products, metals, hydrocarbons, detergents, pesticides, drugs, and other toxics (Sibanda et al 2015;Pereira et al 2016;Silva et al 2017).…”

Differential blood counting in fish as a non-destructive biomarker of water contamination exposure

“…Urban effluents consist of complex mixtures containing many toxic compounds, such as organic substances, pharmaceuticals and personal care products, metals, hydrocarbons, detergents, pesticides, drugs, and other toxic contaminants (Seriani et al 2010;Sibanda, Selvarajan, and Tekere 2015;Pereira et al 2016). However, urban effluents are frequently disposed into the aquatic ecosystems without prior treatment, a process that has biological effects and threatens aquatic organisms and human health alike (Alimba, Saliu, and Ubani-Rex 2015).…”

A Review: Assessment of Trace Metals in Municipal Sewage and Sludge: A Case Study of Limpopo Province, South Africa

“…On the Oliphant River catchment, there are a number of municipal sewage plants that discharge effluent either directly into the Oliphant River [15] or via some of tributaries such as the Elands River [23] and Ga-Selati River [24]. The Oliphant River is the most polluted river in South Africa and this is mainly due to mining activities, especially acid mine drainage, commercial and subsistence farming, and formal and informal residential discharges from municipal sewage plants [15,25].…”