Effect of Chlorination on Microbiological Quality of Effluent of a Full-Scale Wastewater Treatment Plant

Abstract

The evaluation of effluent wastewater quality mainly relies on the assessment of conventional bacterial indicators, such as fecal coliforms and enterococci; however, little is known about opportunistic pathogens, which can resist chlorination and may be transmitted in aquatic environments. In contrast to conventional microbiological methods, high-throughput molecular techniques can provide an accurate evaluation of effluent quality, although a limited number of studies have been performed in this direction. In this work, high-throughput amplicon sequencing was employed to assess the effectiveness of chlorination as a disinfection method for secondary effluents. Common inhabitants of the intestinal tract, such as Bacteroides, Arcobacter and Clostridium, and activated sludge denitrifiers capable of forming biofilms, such as Acidovorax, Pseudomonas and Thauera, were identified in the chlorinated effluent. Chloroflexi with dechlorination capability and the bacteria involved in enhanced biological phosphorus removal, i.e., Candidatus Accumulibacter and Candidatus Competibacter, were also found to resist chlorination. No detection of Escherichia indicates the lack of fecal coliform contamination. Mycobacterium spp. were absent in the chlorinated effluent, whereas toxin-producing cyanobacteria of the genera Anabaena and Microcystis were identified in low abundances. Chlorination significantly affected the filamentous bacteria Nocardioides and Gordonia, whereas Zoogloea proliferated in the disinfected effluent. Moreover, perchlorate/chlorate- and organochlorine-reducing bacteria resisted chlorination.

Assessment of Effluent Wastewater Quality and the Application of an Integrated Wastewater Resource Recovery Model: The Burgersfort Wastewater Resource Recovery Case Study

“…Furthermore, these results implied that the disinfection method used was not sufficient. Zerva et al [45] also observed poor disinfection by chlorine due to its limited effect on the bacterial structure of TC, FC, and E. coli. Therefore, chlorination needs to be applied in tandem with other disinfection methods such as ozonation.…”

Quantitative detection and reduction of potentially pathogenic bacterial groups of Aeromonas, Arcobacter, Klebsiella pneumoniae species complex, and Mycobacterium in wastewater treatment facilities

“…In addition, the correlation between antibiotic-resistant bacteria, antibiotic-resistance genes, and water quality parameters should be further investigated to comprehensively reduce health risks associated with the discharge and use of treated wastewater [ 82 ]. Furthermore, certain Aeromonas , Arcobacter , and Mycobacterium members can be highly resistant to chlorine disinfection, which is the most cost-effective disinfection method [ 83 ]. Therefore, the efficacy of different disinfection methods against these potentially pathogenic bacterial groups warrants further investigation.…”

The Prevalence of Arcobacteraceae in Aquatic Environments: A Systematic Review and Meta-Analysis

“…Further, surface and groundwater are usually used as a water source in developing countries for multiple purposes, increasing the potential health risk. In turn, the lower values of the estimated prevalence of Arcobacteraceae species in processing water and drinking water may be associated with the potential inactivation effect of these bacteria by the chlorination process of the water [27], which may be ineffective [28,29]. The presence of Arcobacteraceae in environmental waters indicates that it can survive and persist in those waters, which points to their potential to be waterborne pathogens.…”