Near Real-Time Flow Cytometry Monitoring of Bacterial and Viral Removal Efficiencies during Water Reclamation Processes

Reclaimed water use is an important component of sustainable water resource management. However, there are concerns regarding pathogen transport through this alternative water supply. This study characterized the viral community found in reclaimed water and compared it with viruses in potable water. Reclaimed water contained 1000-fold more virus-like particles than potable water, having approximately 10(8) VLPs per millilitre. Metagenomic analyses revealed that most of the viruses in both reclaimed and potable water were novel. Bacteriophages dominated the DNA viral community in both reclaimed and potable water, but reclaimed water had a distinct phage community based on phage family distributions and host representation within each family. Eukaryotic viruses similar to plant pathogens and invertebrate picornaviruses dominated RNA metagenomic libraries. Established human pathogens were not detected in reclaimed water viral metagenomes, which contained a wealth of novel single-stranded DNA and RNA viruses related to plant, animal and insect viruses. Therefore, reclaimed water may play a role in the dissemination of highly stable viruses. Information regarding viruses present in reclaimed water but not in potable water can be used to identify new bioindicators of water quality. Future studies will need to investigate the infectivity and host range of these viruses to evaluate the impacts of reclaimed water use on human and ecosystem health.

Viruses have been detected in the different stages of wastewater treatment plants (WWTPs) at concentrations of 10(8) -10(10)  ml(-1) of virus-like particles (VLPs), 10-1000 times higher than in natural aquatic environments, suggesting that WWTPs can be considered as an important reservoir and source of viruses. This study revealed novel diversity and function with the DNA viral communities in the influent, activated sludge, anaerobic digester, and effluent of a domestic WWTP using metagenomics. WWTP was a very specific environment, with less than 5% of the > 936 000 metagenomic sequences obtained (∼70-119 Mbp per sample) similar to sequences present in other environmental viromes. Many viruses found in the WWTP were novel, resulting in only  82% were shared. These data suggested that VLPs of most viral types could be present between 1 and 30 days in the process before they were discharged. Viruses in WWTP and the discharged ones can have potential impacts on the functioning of the wastewater treatment system and on the dynamics of microbial community in the surrounding aquatic environments respectively. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

The paucity of proper sanitation facilities has contributed to the spread of waterborne diseases in many developing countries. The primary goal of this study was to demonstrate the feasibility of using a wastewater electrolysis cell (WEC) for toilet wastewater disinfection. The treated wastewater was designed to reuse for toilet flushing and agricultural irrigation. Laboratory-scale electrochemical (EC) disinfection experiments were performed to investigate the disinfection efficiency of the WEC with four seeded microorganisms (Escherichia coli, Enterococcus, recombinant adenovirus serotype 5, and bacteriophage MS2). In addition, the formation of organic disinfection byproducts (DBPs) trihalomethanes (THMs) and haloacetic acids (HAA5) at the end of the EC treatment was also investigated. The results showed that at an applied cell voltage of +4 V, the WEC achieved 5-log10 reductions of all four seeded microorganisms in real toilet wastewater within 60 min. In contrast, chemical chlorination (CC) disinfection using hypochlorite [NaClO] was only effective for the inactivation of bacteria. Due to the rapid formation of chloramines, less than 0.5-log10 reduction of MS2 was observed in toilet wastewater even at the highest [NaClO] dosage (36 mg/L, as Cl2) over a 1 h reaction. Experiments using laboratory model waters showed that free reactive chlorine generated in situ during EC disinfection process was the main disinfectant responsible for the inactivation of microorganisms. However, the production of hydroxyl radicals [•OH], and other reactive oxygen species by the active bismuth-doped TiO2 anode were negligible under the same electrolytic conditions. The formation of THMs and HAA5 were found to increase with higher applied cell voltage. Based on the energy consumption estimates, the WEC system can be operated using solar energy stored in a DC battery as the sole power source.