Assessing the abundance of Cryptosporidium and Giardia spp. in borehole water close to eMbalenhle wastewater treatment plant and associated human health impacts

Abstract

Groundwater quality is often an overlooked aspect and due to this oversight, groundwater remains vulnerable to contamination by such sources as wastewater treatment plants (WWTPs). Even though most WWTPs in South Africa are monitoring the contamination of groundwater for physicochemical and some microbiological parameters, contamination by Cryptosporidium and Giardia spp. are often disregarded. Using groundwater contaminated with enteric pathogens like Cryptosporidium and Giardia oo(cyst) for consumption, irrigation, and recreational activities lead to gastrointestinal illness in humans and animals. This research aimed to assess the abundance of Cryptosporidium and Giardia spp. in borehole water close to the eMbalenhle wastewater treatment plant and the associated impacts. Groundwater samples were collected from three boreholes located inside the eMbalenhle wastewater treatment plant in the period autumn to the summer season. The samples were collected and analyzed for the physicochemical and microbiological indicator parameters including the presence of Cryptosporidium and Giardia oo(cyst). The selected parameters were evaluated and compared with the South African National Standard for Drinking Water SANS241:2015, South African Water Guidelines (Irrigation, Recreational Activities, and Aquatic Ecosystem), and guidelines for drinking water as stipulated by the World Health Organization (WHO). The correlation between the physicochemical and microbiological parameters with the abundance of the oo(cyst) was determined using Microsoft Excel correlation analysis. Some physicochemical parameters of boreholes exceeded the recommended limits except the range of such parameters as total ded solids (TSS) (21-157 mg/L), nitrates (17- 20 mg/L), phosphate (0.2 mg/L), and ammonia (0.1- 0.2 mg/L), which were below the SANS241:2015 specification of 1.5 mg/L. The results for (pH, conductivity, and chloride) showed a degree of conformance with all the standards. The E. coli and coliforms were present in all the boreholes throughout the sampling seasons, with E. coli in the range 7- 900 cfu/100 mL and fecal coliform in the range 9 – 1100 cfu/100 mL. The highest counts were recorded in autumn. Cryptosporidium and Giardia (oo)cysts were detected by immunofluorescence and immunomagnetic separation. An analysis of groundwater samples from all the boreholes for Cryptosporidium detected oo(cysts) in autumn in one borehole. An analysis for Giardia on all samples from the two seasons (autumn and summer) showed the presence of a Giardia cyst. In autumn, all boreholes tested positive for Giardia cysts and the highest count for the cysts were recorded in the same period. In summer cysts were detected in only one borehole. The findings of the study can be used by the Govan Mbeki Municipality to improve its existing groundwater quality and monitoring strategy. The microbial parameters exceeded acceptable limits and proved the borehole water to be unsuitable for human consumption, irrigation, recreational activities, and aquatic ecosystem.