Mitigating risks and maximizing sustainability of treated wastewater reuse for irrigation.

Scarcity of freshwater for agriculture has led to increased utilization of treated wastewater (TWW), establishing it as a significant and reliable source of irrigation water. However, years of research indicate that if not managed adequately, TWW may deleteriously affect soil functioning and plant productivity, and pose a hazard to human and environmental health. This review leverages the experience of researchers, stakeholders, and policymakers from Israel, the United-States, and Europe to present a holistic, multidisciplinary perspective on maximizing the benefits from municipal TWW use for irrigation. We specifically draw on the extensive knowledge gained in Israel, a world leader in agricultural TWW implementation. The first two sections of the work set the foundation for understanding current challenges involved with the use of TWW, detailing known and emerging agronomic and environmental issues (such as salinity and phytotoxicity) and public health risks (such as contaminants of emerging concern and pathogens). The work then presents solutions to address these challenges, including technological and agronomic management-based solutions as well as source control policies. The concluding section presents suggestions for the path forward, emphasizing the importance of improving links between research and policy, and better outreach to the public and agricultural practitioners. We use this platform as a call for action, to form a global harmonized data system that will centralize scientific findings on agronomic, environmental and public health effects of TWW irrigation. Insights from such global collaboration will help to mitigate risks, and facilitate more sustainable use of TWW for food production in the future.

Performic Acid Disinfection of Municipal Secondary Effluent Wastewater: Inactivation of Murine Norovirus, Fecal Coliforms, and Enterococci.

Performic acid (PFA) is an emerging disinfectant to inactivate bacterial and viral microorganisms in wastewater. In this study, the inactivation kinetics of murine norovirus (MNV) by PFA, in phosphate buffer and municipal secondary effluent wastewater, are reported for the first time. PFA decay followed first-order kinetics and the inactivation of MNV was governed by the exposure of microorganisms to PFA, i.e., the integral of the PFA concentration over time (integral CT or ICT). The extension of the Chick-Watson model, in the ICT domain, described well the reduction of MNV by PFA, with determined ICT-based inactivation rate constants, kd, of 1.024 ± 0.038 L/(mg·min) and 0.482 ± 0.022 L/(mg·min) in phosphate buffer and wastewater, respectively, at pH 7.2. Furthermore, the simultaneous PFA inactivation of MNV and fecal indicators indigenously present in wastewater such as fecal coliforms and enterococci showed that 1-log reduction could be achieved with ICT of 2, 1.5, and 3.5 mg·min/L, respectively. When compared with the most commonly used peracid disinfectant of municipal wastewater, peracetic acid (PAA), the ICT requirements determined using the fitted ICT-based kinetic models were ∼20 times higher for PAA than PFA, indicating a much stronger inactivation power of the PFA molecule.

Inactivation of Murine Norovirus and Fecal Coliforms by Ferrate(VI) in Secondary Effluent Wastewater.

Ferrate(VI) (FeVIO42, Fe(VI)) is an emerging oxidant/disinfectant to treat a wide range of contaminants and microbial pollutants in wastewater. This study describes the inactivation of murine norovirus (MNV) by Fe(VI) in phosphate buffer (PB) and secondary effluent wastewater (SEW). The decay of Fe(VI) had second-order kinetics in PB while Fe(VI) underwent an initial demand followed by first-order decay kinetics in SEW. The Chick-Watson inactivation kinetic model, based on integral CT (ICT) dose, well fitted the inactivation of MNV in both PB and SEW. In PB, the values of the inactivation rate constant (kd) decreased with an increase in pH, which was related to the reaction of protonated Fe(VI) species (HFeO4-) with MNV. Higher kd was observed in SEW than in PB. The inactivation of indigenous fecal coliforms (FC) in SEW was also measured. A two-population double-exponential model that accounted for both dispersed and particle-associated FC well fitted the inactivation data with determined kd and particle-associated inactivation rate constant (kp). Results show that Fe(VI) was more effective in inactivating dispersed FC than MNV. The MNV inactivation results obtained herein, coupled with the detailed modeling, provide important information in designing an Fe(VI) wastewater disinfection process.

Inactivation kinetics of antibiotic resistant Escherichia coli in secondary wastewater effluents by peracetic and performic acids.

While disinfection processes have been central for public health protection, new concerns have been raised with respect to their ability to control the spread of antibiotic resistance in the environment. In this study, we report the inactivation kinetics by peracetic and performic acids of a typical indicator, Escherichia coli and its corresponding antibiotic-resistant subpopulation, in secondary settled wastewater effluent. Performic acid always showed greater inactivation efficiency than peracetic acid, whether or not the indicator was Ampicillin-resistant. Observed inactivation data, fitted with an exposure-based inactivation model, predicted very well the inactivation profile of both total and ampicillin resistant Escherichia coli. Notably, the antibiotic resistance percentage decreased significantly in treated wastewater compared to untreated wastewater thus making the peracid-based disinfection processes beneficial in controlling antibiotic resistance in secondary settled wastewater. Moreover, the minimum inhibitory concentration values remained unchanged. Finally, antibiotic-resistant-specific inactivation kinetics were used to predict the disinfection efficiency in continuous-flow reactors under ideal and non-ideal hydraulics thus providing useful information for future design and operation of disinfection process in antibiotic-resistance controlling mode.

Detailed modeling and advanced control for chemical disinfection of secondary effluent wastewater by peracetic acid.

Advanced control of chemical disinfection processes is becoming increasingly important in view of balancing under-treatment (low pathogen inactivation) and over-treatment (excessive consumption of disinfectant and disinfection byproducts formation) thereby providing considerable environmental and economic benefits. Conventional control strategies such as flow pacing or residual trim ignore chemical demand/decay, inactivation kinetics, and other factors governing disinfection performance in continuous-flow reactors such as reactor hydraulics and process variability. This study presents the development, verification, and pilot-scale validation of a novel CT-based real-time disinfection control strategy, derived from first principles, and applied to peracetic acid disinfection of municipal secondary effluent wastewater. Validation experiments were carried out using a 3-m3 pilot contact basin of which the hydraulic performance was first characterized by means of tracer tests and then mathematically modeled using the well-established theoretical framework of continuous stirred-tank reactors in series. The analytical model describing hydraulic performance was subsequently extended to take into account disinfectant demand/decay and microbial inactivation kinetics. The integrated model was successfully used to predict, and control, residual peracetic acid as well as microbial concentration in the pilot effluent. Validation studies conclusively supported that the novel CT-based control strategy was superior in maintaining constant disinfection performance, desired microbial counts, and low residual disinfectant under variable flow and wastewater quality. When compared with flow pacing, the CT-based control required two times less the amount of chemical for the same treatment objective (<100 cfu/100 mL). Remarkably, the CT-based control strategy could be extended to other chemical disinfection processes such as chlorination and ozonation, alone or in combination with physical treatment technologies such as membranes and ultraviolet irradiation.