Disinfection means the killing of pathogenic organisms (e.g. bacteria and its spores, viruses, protozoa and their cysts, worms, and larvae) present in water to make it potable for other domestic works. The substances used in the disinfection of water are known as disinfectants. At municipal level, chlorine (Cl₂), chloramines (NH₂Cl, NHCl₂), chlorine dioxide (ClO₂), ozone (O₃) and ultraviolet (UV) radiations, are the most commonly used disinfectants. Chlorination, because of its removal efficiency and cost effectiveness, has been widely used as method of disinfection of water. But, disinfection process may add several kinds of disinfection by-products (DBPs) (∼600–700 in numbers) in the treated water such as Trihalomethanes (THM), Haloacetic acids (HAA) etc. which are detrimental to the human beings in terms of cytotoxicity, mutagenicity, teratogenicity and carcinogenicity. In water, THMs and HAAs were observed in the range from 0.138 to 458 μg/L and 0.16–136 μg/L, respectively. Thus, several regulations have been specified by world authorities like WHO, USEPA and Bureau of Indian Standard to protect human health. Some techniques have also been developed to remove the DBPs as well as their precursors from the water. The popular techniques of DBPs removals are adsorption, advance oxidation process, coagulation, membrane based filtration, combined approaches etc. The efficiency of adsorption technique was found up to 90% for DBP removal from the water.

Recent reports are pointing towards the potential increasing risks of resistomes in human host. With no permissible limit in sight, resistomes are continually multiplying at an alarming rate in the ecosystem, with a disturbing level in drinking water source. The morphology and chemical constituent of resistomes afford them to resist degradation, elude membrane and counter ionic charge, thereby, rendering both conventional and advanced water and wastewater treatment inefficient. Water and wastewater matrix may govern the propagation of individual resistomes sub-type, co-selection and specific interaction towards precise condition may have enhanced the current challenge. This review covers recent reports (2011–2019) on the occurrence of ARB/ARGs and ease of spread of resistance genes in the aquatic ecosystem. The contributions of water matrix to the spread and mitigation, treatment options, via bulk removal or capture, and intracellular and extracellular DNA lysis were discussed. A complete summary of recent occurrences of ARB/ARGs, fate after disinfection and optimum conditions of individual treatment technology or in tandem, including process limitations, with a brief assessment of removal or degradation mechanism were highlighted.

Due to continuous spread of coronavirus disease 2019 (COVID-19) worldwide, long-term effective prevention and control measures should be adopted for public transport facilities, as they are increasing in popularity and serve as the principal modes for travel of many people. The human infection risk could be extremely high due to length of exposure time window, transmission routes and structural characteristics during travel or work. This can result in the rapid spread of the infection. Based on the transmission characteristics of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and the nature of public transport sites, we identified comprehensive countermeasures toward the prevention and control of COVID-19, including the strengthening of personnel management, personal protection, environmental cleaning and disinfection, and health education. Multi-pronged strategies can enhance safety of public transportation. The prevention and control of the disease during the use of public transportation will be particularly important when all countries in the world resume production. The aim of this study is to introduce experience of the prevention and control measures for public transportation in China to promote the global response to COVID-19.

The pressure on natural water resources associated with increasing water scarcity highlights the value of using reclaimed water through the development of efficient and environmentally friendly treatment technologies. In this work, the use of magnetic nanoparticles in photo-Fenton catalysis for water disinfection was considered to inactivate natural enteric bacteria present in municipal wastewater effluents under white light and neutral pH. The most recommended ranges were evaluated in key variables such as the loading and composition of nanoparticles (NPs), hydrogen peroxide (H₂O₂) concentration, the light source (UV and visible) and treatment time were evaluated in wastewater disinfection expressed in terms of total coliforms and Escherichia coli colony forming units (CFU). The magnetic separation of NPs allowed the disinfection process to be carried out in different cycles, facilitating the recovery of the nanocatalyst and avoiding its discharge with the treated effluent.

In the present work, acute impact of heavy metals on activated sludge was investigated, specifically the release of biopolymers and nitrogenous soluble microbiological products (N-SMP) that significantly impact tertiary effluent quality. Based on the previously reported studies, Hg²⁺ and Ag⁺ were selected as representative “non-essential” heavy metals, while Cu²⁺ was selected as the “essential” heavy metal. Stress tests show that under the present experimental conditions, adding a higher concentration of heavy metals to the activated sludge increases the concentration of biopolymers and SMP in the supernatant; N-SMP increased more significantly than carbonaceous products, implying a greater risk of formation of toxic nitrogenous disinfection by-products or membrane fouling in relevant tertiary treatment processes. The severity of the release of SMP into the supernatant depended on the heavy metal, with an order of Hg²⁺ > Ag⁺ > Cu²⁺ (“non-essential” > “essential”) under identical molar concentrations. The mass balance of typical organics (e.g., biopolymers) in SMP and extracellular polymeric substances (EPS) in activated sludge was analyzed, and a negative correlation between the organics in the SMP and tightly bound EPS was observed, implying that a significant fraction of the SMP could be quickly released from the tightly bound EPS under heavy metal shock conditions and could be related to cell response or damage.

Wastewater has become one of the most important and least expensive water for the agriculture sector, as well as an alternative to the overexploitation of water resources. However, inappropriate treatment before its reuse can result in a negative impact on the environment, such as the presence of pathogens. This poses an increased risk for environmental safety, which can subsequently lead to an increased risk for human health. Among all the emerging wastewater pathogens, bacteria of the genus Helicobacter are some of the most disturbing ones, since they are directly related to gastric illness and hepatobiliary and gastric cancer. Therefore, the aim of this study was to determine the presence of potentially pathogenic Helicobacter spp. in treated wastewater intended for irrigation. We used a next generation sequencing approach, based on Illumina sequencing in combination with culture and other molecular techniques (qPCR, FISH and DVC-FISH), to analyze 16 wastewater samples, with and without an enrichment step. By culture, one of the direct samples was positive for H. pylori. FISH and DVC-FISH techniques allowed for detecting viable Helicobacter spp., including H. pylori, in seven out of eight samples of wastewater from the tertiary effluents, while qPCR analysis yielded only three positive results. When wastewater microbiome was analyzed, Helicobacter genus was detected in 7 samples. The different molecular techniques used in the present study provided evidence, for the first time, of the presence of species belonging to the genus Helicobacter such as H. pylori, H. hepaticus, H. pullorum and H. suis in wastewater samples, even after disinfection treatment.

Giardia is a protozoan parasite of primary concern for the drinking water industry. High contact times are required for Giardia inactivation by chlorination, while ozonation may be effective at much lower Ct products. In this study, we have assessed the occurrence of Giardia cysts in raw water, and in chlorinated or ozonated water from a drinking water treatment plant (DWTP) in Brazil, over a 16-month period. Moreover, we analyzed the effects of primary disinfection on cysts, and calculated the infection risk caused by the occurrence of Giardia cysts in raw water, chlorinated or ozonated water. Furthermore, we assessed the correlation of Giardia cysts with indicator bacteria in raw water. Data referring to concentration of Giardia cysts in raw water showed adherence to a gamma distribution at a significance level α = 0.05. The detection frequency and the mean concentration of Giardia cysts were higher in raw water (86.6%, 26 cysts∙L⁻¹), than in chlorinated (46.1%, 15.7 cysts·L⁻¹) or ozonated water (43.5%, 11.1 cysts·L⁻¹). Overall, Giardia non-viable cysts were detected more frequently in ozonated water (80%) than in chlorinated water (68.2%) or raw water (37.7%). Ozonation and chlorination resulted, respectively, in ≈27.5- and ≈13- fold reduction of Giardia infection risk, when compared to the risk calculated for raw water. Total coliform and Escherichia coli proved to be suitable surrogates to predict the occurrence of Giardia cysts in raw surface water, however, the indicator bacteria may not be suitable surrogates to predict the disinfection of Giardia cysts, as no correlation was found between indicator bacteria and Giardia cysts in treated water. To our knowledge, this is the first study reporting the efficacy of chlorine and ozone at Ct products actually applied at a full-scale drinking water treatment plant against Giardia cysts naturally occurring in the source water, i.e. real situation. Ozonation has proven more efficient than chlorination against Giardia cysts in surface water. Escherichia coli proved to be suitable surrogate to predict Giardia cysts in raw surface water.

The existence of micropollutants (MPs) including pathogens in waters poses great risks to ecological safety and human health. Sulfate radical (SO4•−)‒based advanced oxidation processes (AOPs) have attracted considerable attention in water treatment for both disinfection and removal of emerging MPs. Here, we investigated the SO4•−‒mediated kinetic and mechanistic aspects of simultaneous inactivation of Enterococcus faecalis (E. faecalis) and degradation of carbamazepine (CBZ), a typical MP with high occurrence in wastewater. In the absence of CBZ, (73.8 ± 2.3) % E. faecalis were inactivated after 12 min of treatment, while in the presence of CBZ, (68 ± 1.6) % of E. faecalis were inactivated, exhibiting similar inactivation efficiency with or without MP. The second‒order rate constant (k) of E. faecalis reacting with SO4•− was determined to be (5.42 ± 0.64) × 10⁹ M⁻¹ s⁻¹. In addition, two distinct types of disinfection models, one based on the quenching ratio (Q model) and the other on steady‒state concentration of SO4•− (R model), were developed to predict the inactivation kinetics of E. faecalis. Both models exhibited good performance for describing the disinfection of E. faecalis with RMSE of 0.065 and 0.048, respectively. Our kinetic experimental and modelling results on bacterial disinfection and degradation of CBZ were projected to offer valuable insight into future developments for typical wastewater scenarios where microorganisms and MPs coexist.

Ballast water (BW) is a dead weight used by ships to provide stability in their journeys. It poses health, economic and ecological problems. Since 2017, the International Maritime Organization-IMO mandated management of BW. This research compares plankton mortality and microorganism inactivation in different BW treatments to identify possible decay models. Treatments include solar radiation (Srad), UV, H₂O₂ and advanced oxidation processes (AOPs).In the wild populations, the disinfection capacity was measured in natural seawater pumped from the Santa Marta port zone in Colombia. AOPs showed different models and effectiveness according to the treatment and microorganism. Plankton larger than 50 μm was the most resistant; therefore, it must be removed first by a previous filter. Wild microorganisms showed log-linear and log-linear tail decay models for most AOPs in E. coli. For Vibrio, the models were log-lineal tail and biphasic models.

Wastewater treatment plants (WWTPs), usually designed to remove organic pollutants and nutrients, are often poorly equipped to handle pathogens. The present study investigated the multiple barriers provided by WWTPs to understand their role in spreading pathogenic bacteria into the environment. Three types of WWTPs (hospital, domestic, and mixed) differing in the source of raw influent, operating parameters, and reactor configuration (biological and tertiary treatment processes) were compared for the presence of fecal indicators and pathogenic bacteria discharged in their treated effluents. The plate-count technique was used for bacterial enumeration on selective agar. The microbial quality of the treated effluent was observed to be strongly influenced by characteristics inherent to a WWTP rather than depending on the characteristics of the raw influent. Among the different configurations studied, membrane bioreactor (MBR) treatment followed by chlorine disinfection provided an effluent of the highest quality (100% bacterial removal rates) followed by moving bed bioreactor (MBBR) combined with UV disinfection. MBR treatment greatly increased the efficiency of chlorine disinfection. Higher total suspended solids (TSS) removal corresponded to higher bacterial removal rates. Tertiary treatment proved to be an important determinant of the microbial quality of the final effluent. A great heterogeneity was observed in the removal rates of different bacterial groups with different treatment processes. The highest removal was observed in the case of indicators and least in the case of emerging pathogens like Escherichia coliO157: H7 indicating a lack of correlation between traditional indicators and emerging pathogens and also the inefficiency of the current wastewater treatment technologies in dealing with emerging pathogens.