Oestrogen, testosterone, cytotoxin and cholinesterase inhibitor removal during reclamation of sewage to drinking water

Abstract

Namibia is the driest sub-Saharan country in Africa. Namibia's capital, Windhoek, reclaims sewage water for domestic use at the Goreangab Water Reclamation Plant (GWRP). Risks associated with sewage effluent and reclaimed sewage should be closely monitored; therefore water at the Gammams Sewage Treatment Plant (GSTP) inlet and outlet, as well as reclaimed water from the GWRP, were assayed using selected bioassays. Samples collected were analysed using enzyme-linked immunosorbent-assays and chromogenic tests for steroid hormones, neurotoxicity, cytotoxicity and inflammatory activity. Estradiol level at the sewage treatment inlet was 78 pg/mℓ and the treated sewage level showed an 83% to 95% reduction in this, while after reclamation the level was below detection limit. Estrone concentrations at the sewage treatment inlet ranged from 10 to 161 pg/mℓ. Sewage treatment reduced estrone by between 85% and 92%. After reclamation the level of estrone was below detection limit. Testosterone ranged between 162 and 405 pg/mℓ at the sewage plant inlet. Sewage treatment removed 96% of the initial testosterone. The residual testosterone was effectively removed by processes in GWRP and after reclamation no testosterone was detected in water. Acetylcholinesterase (AChE) inhibition at the sewage treatment inlet was 50% while it was only 27% after sewage treatment. After reclamation AChE inhibition was not detected. Only water at the sewage inlet in March and February showed cytotoxicity. High inflammatory activity was detected at the sewage plant inlet. Sewage treatment reduced inflammatory activity by 64%. After reclamation low inflammatory activity was induced. Treated sewage used for reclamation tested positive for most of the biomarkers and can pose a risk to human health. However, reclamation successfully removed these contaminants. Due to the presence of contaminants in the intake water at the reclamation plant, it is essential to routinely monitor the water produced by the reclamation plant for potential residues that can adversely affect human health.

Steroid hormone concentrations and physiological toxicity of water from selected dams in Namibia

“…Furthermore, excess sewage effluent from the GSTP, which receives stormwater runoff and domestic sewage, is also released into the dam. This effluent showed AChE inhibition of up to 22% (Faul et al 2013). Comparable studies indicated that sewage effluent and stormwater runoff can be a source of chemicals (e.g.…”

“…Furthermore, part of the effluent from the Gammams sewage treatment plant (GSTP) is released into the dam. This effluent contains testosterone concentrations exceeding 10 pg ml -1 (Faul et al 2013).…”

“…Inter-and intra-assay variation for steroid hormone ELISAs are negligible, as shown by Swart and Pool (2007) who determined inter-assay variation at 5.6% (n  3) and intra-assay variation between 0.6% and 2.5% (n  3). This was repeated by Faul et al (2013), who measured inter-assay variation at 0.8% (n  15) and intraassay variation between 0.3% and 7.2% (n  3). Thus, the accuracy of the ELISAs reduces the need for expensive and time-consuming replication and provides for a rapid screen of a number of samples.…”

“…Consequently, the largest part of Namibia relies on water from boreholes or surface water in dams for human consumption, agriculture and industry. However Windhoek, the capital of Namibia, also relies on the reclamation of sewage water to supplement the potable water supply, and it is especially here that the monitoring for EDCs becomes critical (du Pisani 2006;Faul et al 2013). A large proportion of the country is hyper-arid and the majority of the population is concentrated in more densely populated towns, usually located close to water sources.…”

“…Namibia has a low population density, with 823 680 km 2 of land being inhabited by a population of about 2.1 million in Introduction Faul, Julies andPool 190 2011 (National Planning Commission 2012). It is a predominantly hyper-arid to semi-arid country with an average annual rainfall of 360 mm (Mendelsohn et al 2009).…”