Assessment of raw and treated sewage using in vitro assays
Water scarcity is becoming an increasingly relevant problem for urban centres, especially in Southern Africa. However, water availability is not the only concern for consumers, because water quality is just as relevant. Many studies have revealed adverse health effects in organisms exposed to polluted waters, and the main source of that water pollution was traced back to sewage treatment works (STWs). Physiological systems that are affected include the endocrine system (as well as the reproductive system) and the immune system. Recently, the Stellenbosch STW started upgrading its facility, but this procedure would also affect the STW‘s operations. Stellenbosch STW uses an activated sludge treatment, but also employs trickling filters (biofilters). After screening and grit removal, wastewater enters trickling filters, and then undergoes activated sludge treatment (aerobic basin). After activated sludge treatment (and settling) some water is chlorinated before entering a maturation pond. The other water goes directly to a larger maturation pond (for a longer period), instead. The final effluent then gets discharged into the Veldwagters River. Since STW operations is an important factor in STW effluent quality, this study aimed to investigate the water quality (at Stellenbosch STW) during the upgrade. Specifically, the bacterial quality, the steroidal quality (testosterone, progesterone, estrone: E1, 17 β- estradiol: E2 and 17 α-ethinyl estradiol: EE2) and the potential immunotoxic quality of waters were assessed. Water samples were collected after the grit removal (influent), after the trickling filters (biofilter effluent), while it was leaving the aerobic basin activated sludge effluent) and as it was leaving the maturation ponds (final effluent). To determine bacterial quality a semi-quantitative ReadyCult® assay was performed on raw water samples (detects total coliforms and Escherichia coli). Bacterial levels were high for all influent samples, water from the biofilter, water from the aerobic digester (activated sludge) and the final effluent (most days). The first collection date, however, showed less than 1cfu/mL of both E. coli and total coliforms for the final effluent. Raw water also underwent solid phase extraction, before the steroid concentrations were determined by enzyme-linked immunosorbent assays (ELISAs). Steroid levels were very high in the influent. Each treatment progressively reduced the steroid concentration. However, progesterone concentration increased during the biofilter treatment. The increase in progesterone was probably due to bacterial de-conjugation of hydrophilic-progesterone-conjugates. Nonetheless effluent steroid levels were significantly lower than the influent. Steroid reduction through the Stellenbosch STW was 96%, 95%, 55%, 78% and 87% for testosterone, progesterone, estrone, estradiol and ethinyl estradiol respectively. Much variability in steroid concentrations was noted between sampling dates. The activated sludge treatment was the best at reducing steroid concentration. Nonetheless, the STW still discharged steroids into the environment. Finally, the humoral immune effects of Stellenbosch STW influent and effluent was determined by using hybridoma cells and assessing affects on antibody production. Antibody levels were then detected by ELISA. No adverse effects to antibody synthesis/secretion were noted as a result of exposure to either influent or effluent.