This paper applies a semi-quantitative approach to review the diversity, environmental controls, detection methods, human health risks, and mitigation of cyanotoxins in drinking water systems (DWSs). It discusses the environmental factors controlling the occurrence of cyanotoxins, presents the merits and limitations of emerging methods of their detection (qPCR, liquid chromatography–mass spectrometry, and electrochemical biosensors), and outlines the human exposure pathways and health outcomes with identification of high-risk groups and settings. High-risk groups include (1) communities relying on untreated drinking water from unsafe, polluted water sources and (2) low-income countries where cyanotoxins are not routinely monitored in DWSs. The fate and behavior processes are discussed, including removing cyanotoxins in DWSs based on conventional and advanced treatment processes. The available methods for cyanotoxin removal presented in this paper include (1) polymer-based adsorbents, (2) coagulation/flocculation, (3) advanced oxidation processes, (4) ultra- and nanofiltration, and (5) multi-soil layer systems. Future research should address (1) detection and fate in storage and conveyance facilities and at the point of consumption, (2) degradation pathways and toxicity of by-products or metabolites, (3) interactive health effects of cyanotoxins with legacy and emerging contaminants, (4) removal by low-cost treatment techniques (e.g., solar disinfection, boiling, bio-sand filtration, and chlorination), (5) quantitative health risk profiling of high-risk groups, and (6) epidemiological studies to link the prevalence of human health outcomes (e.g., cancer) to cyanotoxins in DWSs.

The management of wastewater remains a challenge, particularly in developing countries. The potential use of constructed wetlands to treat wastewater is promising but their contaminant removal efficiencies, particularly in a tropical country such as Zimbabwe, are not fully understood. A pilot-scale study was undertaken in Zimbabwe to evaluate the efficiency of vertical-flow constructed wetlands planted with Typha latifolia in the treatment of domestic wastewater. Four pilot subsurface vertical-flow constructed wetland units (measuring 1 m × 1 m × 1.1 m) were built from concrete. The units were filled with waste rock from a nickel mine. Three units were planted with Typha latifolia while the fourth one was left unplanted, acting as the control. Each unit was loaded with wastewater at a rate of 220 dm³/day. Physico-chemical and bacteriological parameters were analyzed during the winter season. Physico-chemical and bacterial contaminant concentrations were significantly lower in the effluent than in the influent, and the system achieved maximum removals for BOD₅, COD, TDS, TSS, nitrates, phosphates, phosphate pentoxide, phosphorus, and E. coli of 56.01%, 82.87%, 30.61%, 90.40% 17.26%, 35.80%, 36.19%, 40.64%, and 90.28%, respectively. The study shows that constructed wetland systems can be successfully established for the removal of physical, chemical, and microbial contaminants from domestic wastewater.

Emerging organic contaminants (EOCs) of anthropogenic origins are ubiquitous in environmental compartments, including aquatic systems. Thus, EOCs have attracted considerable research and public attention due to their potential human and ecological health risks. However, compared to other aquatic environments such as wastewater systems, comprehensive reviews focussing on the occurrence and human health risks of EOCs in drinking water systems are still lacking. Therefore, to address this knowledge gap, the current review posits that drinking water systems harbour a cocktail of toxic EOCs, which pose public health risks via multiple exposure routes. In the present review, global evidence is examined to track EOCs along the source-pathway-receptor-impact-mitigation (SPRIM) continuum. Evidence shows that, various groups of EOCs, including pharmaceuticals and personal care products, solvents, plasticizers, endocrine disrupting compounds, gasoline additives, per- and polyfluoroalkyl substances (PFAS), food colourants, artificial sweeteners, and musks and fragrances, have been detected in drinking water systems. The anthropogenic sources of EOCs detected in drinking water systems, including wastewater systems and industrial emissions, are summarized. Further, the behaviour and fate of EOCs in the drinking water systems, including removal processes are discussed. Once in drinking water systems, human exposure to EOCs may occur via ingestion of contaminated drinking water and cooked foods, and possibly dermal contact and inhalation. The high-risk environments, and risk factors and behaviours predisposing humans to EOC exposure are discussed. Evidence on the human health risks of the various EOCs and a critique of the data are presented. Notably, besides inferential data, quantitative epidemiological evidence directly relating the occurrence of EOCs in drinking water systems to specific adverse human health outcomes is still scarce. Lastly, future research directions, including the need for quantitative public health risk assessment, and the application of emerging detection tools are discussed.

Constructed wetlands are increasingly recognised for their potential in wastewater treatment, particularly in the removal of pathogenic microorganisms. However, the mechanisms of removal are not fully understood. This study investigated the role of endophytic and rhizosphere fungi and associated secondary metabolites in the removal of pathogenic bacteria from wastewater. Endophytic and rhizosphere fungi were isolated from roots of wetland macrophytes (T. latifolia, C. papyrus and P. mauritianus) and screened for their antimicrobial effects on E. coli, Shigella spp., Salmonella spp. and Vibrio spp. Secondary metabolites were extracted from fungal isolates (broth cultures) and tested for their antibacterial activity as a possible mechanism of pathogen removal. Antimicrobial activity of the fungi and their metabolites, measured as zones of inhibition, was analysed using ANOVA at a 5% significance level. Active secondary metabolites were identified using GC-MS techniques. Four fungal isolates (three endophytic, one rhizospheric) from the genus Candida exhibited antimicrobial activity against E. coli, Salmonella spp., Shigella spp. and Vibrio spp. in vitro. There were significant differences in inhibition zones (p < 0.0001) between the different species of fungi. Fungus RTGRS did not show any antibacterial activity on Vibrio spp. and Shigella spp. but showed the highest zones of inhibition of 21.17 ± 0.75 against Salmonella spp. This study demonstrated that the selected wetland macrophytes harbour both endophytic and rhizosphere fungi that can produce bioactive compounds that have antimicrobial properties, inhibiting the growth of pathogenic bacteria E. coli, Salmonella spp., Shigella spp. and Vibrio spp., contributing to pathogen removal in CWs. The findings have implications for the design and operation of CWs, as it is important to select macrophytes that harbour fungi with antimicrobial properties. More research is needed on the use of these fungi in wastewater treatment in full-scale CWs.