Monitoring and evaluation of removal of pathogens at municipal wastewater treatment plants

Abstract

The concentrations and removal of Cryptosporidium, Giardia, and microbial indicators, including somatic coliphages and fecal coliforms were investigated through the wastewater treatment processes at three municipal wastewater treatment plants in Beijing, China. The experimental results showed that the concentrations of Cryptosporidium in untreated wastewater, primary treatment effluent, secondary treatment effluent, tertiary treatment effluent were 33-600, 67-333, 0-9 and 0-0.4 oocysts L(-1), and that of Giardia were 130-3,600, 533-2,033, 0-32 and 0-2.1 cysts L(-1), respectively. The reduction ratios of Cryptosporidium and Giardia by the primary treatment process were 0.12 log and 0.18 log, respectively. Oxidation ditch process had higher reduction efficiency to Cryptosporidium and Giardia than anaerobic-anoxic-oxic process and conventional activated sludge process, probably because of longer retention time and higher sludge concentration. Membrane ultrafiltration had a notably better efficiency to reduce microorganisms, especially Cryptosporidium and Giardia, than conventional flocculation sedimentation and sand filtration process, as the tertiary treatment. Comparing with total coliforms, fecal coliforms and heterotrophic bacteria, concentration of somatic coliphages was correlated better with that of Cryptosporidium and Giardia in untreated wastewater and secondary treatment effluent.

Pathogenic members of Escherichia coli & Shigella spp. Shigellosis

“…3.1.4.2 Primary /preliminary treatment The primary treatment performed in wastewater treatment plants does not produce a significant reduction in pathogens. A reduction of 0.06 log 10 units for fecal coliforms was observed after a primary sedimentation treatment in a full-scale waste water treatment plant (Fu et al, 2010) (Table 9).…”

“…Oxidation ditch treatment produced a reduction of around 2.5 log 10 units for fecal coliforms (Fu et al, 2010). Combined sewers carry wastewater from urban areas as well as storm water runoff in the same pipe.…”

“…Secondary wastewater treatment based on activated sludge has been reported to achieve a reduction in fecal coliforms by 2 log 10 units (Garcia-Armisen and Servais, 2007) or higher (Wéry et al, 2008;Fu et al, 2010) and between 2 and 4 log 10 units for E. coli (Francy et al, 2012). The reduction is attributed both to different abiotic and biotic factors, such as adsorption to flocs and sedimentation, the natural microorganisms die-off as well as predation.…”

Pathogenic parasites and enteroviruses in wastewater: support for a regulation on water reuse

“…demonstrating that giardiasis occurs more frequently than cryptosporidiosis in Norway. Fu et al (2010) investigated the performance of three WTPs in Beijing, China, by determining the concentrations of fecal indicators and pathogenic protozoa. According to their study, Cryptosporidium and Giardia densities in untreated wastewater varied from 33 to 600 oocysts/L and 130 to 3,600 cysts/L, respectively.…”

Risk assessment of Giardia from a full scale MBR sewage treatment plant caused by membrane integrity failure

“…Nasser et al (2012) reported that in 23 out of 30 studies, all tested raw wastewater samples were positive for Giardia, at concentrations ranging from 2.3 to 1,000,000 cysts/10 L, showing that Giardia pollution is quite universal and requires effective control to secure the biological safety of reclaimed water. Giardia concentrations in raw wastewater and primary, secondary and tertiary treatment effluents were 1300-36,000, 5330-20,330, 0-320 and 0-21 cysts/10 L, respectively, in three municipal wastewater treatment plants in Beijing, China (Fu et al, 2010). Thus, significant removals of Giardia were achieved through secondary and tertiary treatment, showing the importance of establishing multiple barriers for pathogen control.…”