The effectiveness of sewage treatment processes to remove faecal pathogens and antibiotic residues

Abstract

Pathogens and antibiotics enter the aquatic environment via sewage effluents and may pose a health risk to wild life and humans. The aim of this study was to determine the levels of faecal bacteria, and selected antibiotic residues in raw wastewater and treated sewage effluents from three different sewage treatment plants in the Western Cape, South Africa. Sewage treatment plant 1 and 2 use older technologies, while sewage treatment plant 3 has been upgraded and membrane technologies were incorporated in the treatment processes. Coliforms and Escherichia coli (E. coli) were used as bioindicators for faecal bacteria. A chromogenic test was used to screen for coliforms and E. coli. Fluoroquinolones and sulfamethoxazole are commonly used antibiotics and were selected to monitor the efficiency of sewage treatment processes for antibiotic removal. Enzyme Linked Immunosorbent Assays (ELISAs) were used to quantitate antibiotic residues in raw and treated sewage. Raw intake water at all treatment plants contained total coliforms and E. coli. High removal of E. coli by treatment processes was evident for treatment plant 2 and 3 only. Fluoroquinolones and sulfamethoxazole were detected in raw wastewater from all sewage treatment plants. Treatment processes at plant 1 did not reduce the fluoroquinolone concentration in treated sewage effluents. Treatment processes at plant 2 and 3 reduced the fluoroquinolone concentration by 21% and 31%, respectively. Treatment processes at plant 1 did not reduce the sulfamethoxazole concentration in treated sewage effluents. Treatment processes at plant 2 and 3 reduced sulfamethoxazole by 34% and 56%, respectively. This study showed that bacteria and antibiotic residues are still discharged into the environment. Further research needs to be undertaken to improve sewage treatment technologies, thereby producing a better quality treated sewage effluent.

Review: <i>Pharmaceutical and personal care products (PPCPs) as endocrine disrupting contaminants (EDCs) in South African surface waters</i>

“…potentiating mixture interactions) in water bodies, as a large mixture of different EDCs might be present in water bodies. (Hendricks and Pool, 2012).…”

“…However, less resistance was observed in isolates treated with cephalosporins and fluoroquinolones, which are regarded as 'newly developed' antibiotics. Fluoroquinolones have also been detected in a WWTW effluent in the Western Cape Province (Table 1; Hendricks and Pool, 2012) and, although this pharmaceutical has high sensitivity as an antibacterial treatment, its increased occurrence in water systems might also lead to bacterial adaptation and future resistance.…”

Fecal contamination of wastewater treatment plants in Portugal

“…In Portugal, it is possible to reuse wastewater from municipal treatment plants for several purposes, either in agriculture or industry. However, those wastewaters applied for soil irrigation or industry will eventually reach humans and animals (Burch 2008;Carr et al 2004;Hendricks and Pool 2012), so they must be in accordance with good and acceptable microbiological standards (Burch 2008;Carr et al 2004). These standards take into account the microbiological status of the inflow and effluents and also the treatment methods used.…”

Removal of Escherichia coli in treated wastewater used for food production in Morogoro, Tanzania

“…The overall reduction of E. coli concentration in wastewater treatment ponds at the two study sites was approximately 4-log cfu/mL. The concentration of E. coli of about 5.0 log cfu/mL in untreated wastewater has been documented elsewhere (Hendricks and Pool, 2012;Farasat et al, 2012;George et al, 2007). Likewise a similar 4-log reduction of faecal indicators and pathogens was seen in a comparable wastewater treatment ponds systems treating municipal wastewater in Nigeria (Mohammed, 2006) and India (Tyagi et al, 2008).…”