Tertiary treatment and dual disinfection to improve microbial quality of reclaimed water for potable and non-potable reuse: A case study of facilities in North Carolina

Identification of performance and cost in a new backwash method to clean the UF membrane: backwashing with low dosage of NaClO

Ultrafiltration (UF) is widely used in wastewater reclamation treatments. Conventional backwashing is usually performed at regular time intervals (10-120 min) with permeate and without the addition of chemicals. Chemical enhanced backwashing (CEB) is usually applied after 70-90 filtration cycles with added chemicals. These cleaning methods cause membrane fouling and require costly chemicals. Instead of conventional backwashing, we propose herein a new backwashing method involving backwashing the effluent with low doses of sodium hypochlorite (NaClO) named as BELN. The performance and cost of UF backwashing were investigated with Beijing wastewater reclamation treatment. The results showed that the transmembrane pressure (TMP) increased from 33.2 to 48.2 kPa during hydraulic backwashing after 80 filtration cycles but increased from 33.3 to 39.3 kPa during backwashing with a low NaClO content of 20 mg/L. It was also noticed that the hydraulic-irreversible fouling index decreased from 5.58 × 10-3 m2/L to 3.58 × 10-3 m2/L with the new method. According to the three-dimensional fluorescence excitation-emission (3D-EEM), the response increased from 11.9 to 15.2% with BELN. Protein-like material was identified as the main component causing membrane fouling by blocking the membrane pores. The results indicated that the low dosage of NaClO effectively stripped the fouling layer. Finally, based on an economic evaluation, the capacity of the UF process was increased from 76,959 to 109,133 m3/d with the new method. The amount of NaClO consumed for Beijing wastewater reclamation treatment was similarly compared with the conventional backwashing in per year under BELN. The new method has good potential for application.

New diamond coatings for a safer electrolytic disinfection

In this work, a new coating of boron-doped diamond ultra-nanocrystalline (U-NBDD), tailored to prevent massive formation of perchlorates during disinfection, is evaluated as electrode for the reclaiming of treated secondary wastewater by the electrochemically assisted disinfection process. Results obtained are compared to those obtained by using a standard electrode (STD) that was evaluated as a standard in previous research showing outstanding performance for this application. First tests were carried out to evaluate the chlorine speciation obtained after the electrolysis of synthetic chloride solutions at two different ranges of current densities. Concentrations of hypochlorite obtained using the U-NBDD anode at 25 mA cm-2 were 1.5-fold higher, outperforming STD anode; however, at 300 mA cm-2, an overturn on the behavior of anodes occurs where the amount of hypochlorite produced on STD anode was 1.5-fold higher. Importantly, at low current density the formation of chlorates and perchlorates is null using U-NBDD. Then, the disinfection of the real effluent of the secondary clarifier of a municipal wastewater treatment facility is assessed, where inactivation of Escherichia coli is achieved at low charge applied per volume electrolyzed (0.08 A h L-1) at 25 mA cm-2 using the U-NBDD. These findings demonstrate the appropriateness of the strategy followed in this work to obtain safer electro-disinfection technologies for the reclaiming of treated wastewater.

Life cycle sustainability assessment of advanced treatment techniques for urban wastewater reuse and sewage sludge resource recovery

Wastewater treatment plants can become a source of valuable resources, such as clean water, energy, fuels and nutrients and thus contribute to the sustainable development goals and a transition to a circular economy. This can be achieved by adopting advanced wastewater and sludge treatment techniques. However, these have to be evaluated on their sustainability to avoid any unintentional consequences. Therefore, this paper presents a life cycle sustainability assessment of advanced wastewater and sludge treatment techniques by integrating the environmental, economic and social aspects. The options considered for advanced wastewater treatment are: i) granular activated carbon; ii) nanofiltration; iii) solar photo-Fenton; and iv) ozonation. The technologies for advanced sludge treatment are: i) agricultural application of anaerobically digested sludge; ii) agricultural application of composted sludge; iii) incineration; iv) pyrolysis; and v) wet air oxidation. The results for the advanced wastewater treatment techniques demonstrate that nanofiltration is the most sustainable option if all the sustainability aspects are considered equally important. If, however, a higher preference is given to the economic aspect, ozonation and granular activated carbon would both be comparable to nanofiltration; if the social aspect is considered more important, only activated carbon would be comparable to nanofiltration. Among the sludge treatment methods, agricultural application of sludge is the most sustainable technique for mean-to-high resource recovery. If the recovery rate is lower, this option is comparable with incineration and pyrolysis with high recovery of their respective products. This work helps to identify the most sustainable techniques that could be combined with conventional wastewater treatments for promoting wastewater reuse and resource recovery across a wide range of operating parameters and products outputs. The findings also support the notion that more sustainable wastewater treatment could be achieved by a circular use of water, energy and nutrients contained in urban wastewaters.

Determining reclaimed water quality thresholds and farming practices to improve food crop yield: A meta-analysis combined with random forest model

Irrigated agricultural systems with reclaimed water (RW) play a crucial role in alleviating global water scarcity and increased food demand. However, appropriate reclaimed water quality thresholds and farming practices to improve food crop yield is virtually unclear. Therefore, for the first time, this study made a large compilation of previous studies using meta-analysis combined with a random forest (RF) model and analyzed the impact of RW versus freshwater (FW) on the yield of food crops (cereals, vegetables, and fruits). It was found that magnesium ion (Mg²⁺), calcium ion (Ca²⁺), electrical conductivity (EC), total nitrogen (TN), and potential of hydrogen (pH) were the most important factors for RW quality indicators. Based on the results, water managers should establish more conservative RW quality thresholds to promote food crop production, especially for salts and pollutants in RW. Compared to international water quality standards, it could be slightly relaxed the restrictions of TN in RW. The optimal farming practices obtained that irrigation amount of the mixed RW and FW (RW + FW) was from 1000 m³ ha^-1 to 5000 m³ ha^-1, and the cultivation period was no more than three years. Flood irrigation (FI) and drip irrigation (DI) for cereals were also recommended. Finally, a comparison of the determined results from this method with other scenarios published, finding a good agreement.

A step forward on site-specific environmental risk assessment and insight into the main influencing factors of CECs removal from wastewater

The presence of Contaminants of Emerging Concern (CECs) in water systems has been recognized as a potential source of risk for human health and the ecosystem. The present paper aims at evaluating the effects of different characteristics of full-scale Wastewater Treatment Plants (WWTPs) on the removal of 14 selected CECs belonging to the classes of caffeine, illicit drugs and pharmaceuticals. Particularly, the investigated plants differed because of the treatment lay-out, the type of biological process, the value of the operating parameters, the fate of the treated effluent (i.e. release into surface water or reuse), and the treatment capacity. The activity consisted of measuring concentrations of the selected CECs and also traditional water quality parameters (i.e. COD, phosphorous, nitrogen species and TSS) in the influent and effluent of 8 plants. The study highlights that biodegradable CECs (cocaine, methamphetamine, amphetamine, benzoylecgonine, 11-nor-9carboxy-Δ9-THC, lincomycin, trimethoprim, sulfamethoxazole, sulfadiazine, sulfadimethoxine, carbamazepine, ketoprofen, warfarin and caffeine) were well removed by all the WWTPs, with the best performance achieved by the MBR for antibiotics. Carbamazepine was removed at the lowest extent by all the WWTPs. The environmental risk assessed by using the site-specific value of the dilution factor resulted to be high in 3 out of 8 WWTPs for carbamazepine and less frequently for caffeine. However, the risk was reduced when the dilution factor was assumed equal to the default value of 10 as proposed by EU guidelines. Therefore, a specific determination of this factor is needed taking into account the hydraulic characteristics of the receiving water body.

Modeling carbonate/bicarbonate and nitrate disturbance during secondary effluent disinfection by UV/H2O2 and UV/ozone

The disinfection of effluents has been considered the main step to inactivate pathogenic organisms to prevent the spread of waterborne diseases. The variation in the matrix composition can lead to the use of inadequate oxidant dose and disturb a correct treatment. The objective of this study was to develop a simple and practical mathematical model to simulate the disturbance of inorganic anions (CO₃^2-/HCO₃^- and NO₃^-) during secondary effluent disinfection by UV/H₂O₂ and UV/O₃. The pathogenic agents chosen for this study were total coliforms and E. coli. To build the mathematical model, a modification of the Chick model (referred to as 'Modified Chick Model') was proposed by employing a weighted average in the calculation of the kinetic constant. Both treatments were affected by the presence of the anions. However, with the highest NO₃^- concentration, less inhibition of disinfection was observed in the UV/H₂O₂. The use of the arithmetic means to calculate the value of k, as indicated by the Chick model, demonstrates a lesser precision in the prediction of the microorganisms' concentrations. On the other hand, using the Modified Chick Model, a better prediction of the inactivation of the microorganisms was obtained, which can be confirmed by the validation performed.

Wastewater reuse for irrigation of produce: A review of research, regulations, and risks

The burden of disease caused by the contamination of ready-to-eat produce with common waterborne microbial pathogens suggests that irrigation supplies should be closely monitored and regulated. Simultaneously freshwater resources have become increasingly scarce worldwide while global demand continues to grow. Since the turn of the 20th century with the advent of modern wastewater treatment plants, the reuse of treated wastewater is considered a safe and viable water source for irrigation of ready-to-eat vegetables. However strict, and often costly, treatment regimens mean that only a fraction of the world's wastewater supplies are being put to reuse. The purpose of this review is to explore the available literature on the risks associated with reuse water for ready-to-eat produce production including different approaches to reducing those risks as the demand for reuse water increases. It is not the intent of the authors to determine which methods of treatment should be applied, which pathogens should be considered of greatest concern, or which regulations should be applied. Rather, it is meant to be a discussion of the evolving guidelines governing irrigation with reuse water, potential risks from known pathogens common to produce production and recommendations for improving the adoption of water reuse moving forward. To date, there is little evidence to suggest that adequately treated reuse water poses more risk for produce-related illness or outbreaks than other sources of irrigation water. However, multiple epidemiological and quantitative risk assessment models suggest that guidelines for the use of reuse water should be regionally specific and based on local growing practices, available technologies for wastewater treatment, and overall population health. Though research suggests water reuse is generally safe, the assumptions of risk are both personal and of public interest, they should be considered carefully before water reuse is either allowed or disallowed in produce production environments.

UV inactivation of sewage isolated human adenovirus

Adenoviruses are known to be one of the most resistant viruses to UV disinfection. This study determined the inactivation kinetics of adenovirus freshly isolated from sewage samples, and compared the results with reference adenovirus stocks grown in the laboratory. Human adenoviruses were isolated from sewage samples using the HEK 293 cell line. Inactivation kinetics for UV irradiation was determined for monochromatic low pressure (LP) mercury UV lamp (254 nm) and polychromatic medium pressure (MP) mercury UV lamp for each sewage isolate. Eleven (11) isolates were obtained from nine (9) different sewage samples with most isolates belonging to the enteric adenovirus group, specifically adenovirus 41. The average dose required for 4 log inactivation using LP UV lamps for sewage isolates (220 mJ/cm²) was not significantly different (p > 0.1) from the average dose reported for lab-grown enteric adenovirus (179.6 mJ/cm²). Interestingly, the average dose required for 4 log inactivation using MP UV lamps was significantly higher (p = 0.004) for sewage isolates (124 mJ/cm²) when compared to the average dose reported for laboratory stocks of adenovirus 40 and 41 (71 mJ/cm²). Viral capsid analysis using the propidium monoazide (PMA)-qPCR method showed that adenovirus isolates from group F were less affected by exposure to MP UV Lamps than adenoviruses from group D and C. Adenovirus isolates obtained from sewage samples showed greater resistance to UV irradiation compared to laboratory grown strains, although required doses for MP UV were still considerably lower than LP UV. These data suggest that the required fluence for inactivation of adenoviruses in real-world waters may be higher than previously understood.

A synthetical methodology for identifying priority pollutants in reclaimed water based on meta-analysis

Wastewater reclamation and reuse is an increasing global project, while the reclamation treatment on wastewater does not completely remove all pollutants in water. The residual pollutants in reclaimed water would cause potential risk on human health and ecosystem safety during the long-term use. It is impossible to analyze and control all pollutants one by one in practice, therefore, identification and control of priority pollutants will be efficient strategy to ensure the safe use of reclaimed water. An integrated three-step methodology for identifying priority pollutants in reclaimed water was proposed in this study. First, a comprehensive literature survey on the occurrence of pollutants in reclaimed water was conducted, and a dataset D_PR for pollutants occurrence in reclaimed water was established, containing 1,113 pollutants. Second, 611 chemicals that had been recommended as hazardous pollutants for various water bodies in previous literatures were summarized, and a dataset D_HP for hazardous pollutants in water was obtained. Third, meta-analysis on these two datasets (D_PR and D_HP) was performed, a new dataset D_HPR for hazardous pollutants in reclaimed water was established, including 265 candidates. Finally, 59 substances out of dataset D_HPR were identified as priority pollutants for reclaimed water based on their recommendation frequency. It is expected that this synthetical methodology will provide powerful support for scientific evaluating and managing water pollution and ensuring safe use of reclaimed water.

Evaluating Fecal Indicator and Pathogen Relationships in Sewage Impacted Surface Waters to Blend with Reclaimed Water for Potable Reuse in North Carolina

Surface waters used for drinking water supply often receive upstream wastewater effluent inputs, resulting in de facto wastewater reuse for drinking water and recreation. As populations grow, demands on water supplies increase. As this trend continues, it creates the need to understand the risks associated with such reuse. In North Carolina, potable reuse has been proposed as a combination of at least 80% surface water with up to 20% tertiary-treated, dual-disinfected, reclaimed wastewater, which is then stored for 5 days and further treated using conventional drinking water treatment methods. The state of North Carolina has set standards for both intake surface water and for the reclaimed water produced by wastewater utilities, using indicator microorganisms to measure compliance. The goal of this study was to quantify fecal indicator microorganisms, specifically E. coli, coliphages, and C. perfringens as well as key pathogens, specifically Salmonella spp. bacteria, adenoviruses, noroviruses, and the protozoan parasites Cryptosporidium and Giardia, in two types of water representing potential candidates for potable reuse in North Carolina, (1) run of river surface water and (2) sewage-impacted surface waters, with the purpose of determining if there are predictive relationships between these two microorganism groups that support microbial indicator reliability.

Quantitative microbial human exposure model for faecal indicator bacteria and risk assessment of pathogenic Escherichia coli in surface runoff following application of dairy cattle slurry and co-digestate to grassland

Animal waste contains high numbers of microorganisms and therefore can present a potential biological threat to human health. During episodic rainfall events resulting in runoff, microorganisms in the waste and soil may migrate into surface runoff, contaminating surface water resources. A probabilistic human exposure (HE) model was created to determine exposure to faecal indicator bacteria (FIB): total coliforms (TC), E. coli and enterococci following application of bio-based fertiliser (dairy cattle slurry, digestate) to grassland; using a combination of experimental field results and literature-based data. This step was followed by a quantitative microbial risk assessment (QMRA) model for pathogenic E. coli based on a literature-based dose-response model. The results showed that the maximum daily HE (HE_daily) is associated with E. coli for unprocessed slurry (treatment T1) on day 1, the worst-case scenario where the simulated mean HE_daily was calculated as 2.84 CFU day ^-1. The results indicate that the overall annual probability of risk (P_annual) of illness from E. coli is very low or low based on the WHO safe-limit of P_annual as 10 ^-6. In the worst-case scenario, a moderate risk was estimated with simulated mean P_annual as 1.0 × 10 ^-5. Unpasteurised digestate application showed low risk on day 1 and 2 (1.651 × 10 ^-6, 1.167 × 10 ^-6, respectively). Pasteurised digestate showed very low risk in all scenarios. These results support the restriction imposed on applying bio-based fertiliser if there is any rain forecast within 48 h from the application time. This study proposes a future extension of the probabilistic model to include time, intensity, discharge, and distance-dependant dilution factor. The information generated from this model can help policymakers ensure the safety of surface water sources through the quality monitoring of FIB levels in bio-based fertiliser.

An insight to sequential ozone‑chlorine process for synergistic disinfection on reclaimed water: Experimental and modelling studies

Water reclamation plants (WRPs) are facing the challenges of ensuring microbial safety and require efficient disinfection systems. Sequential ozone‑chlorine disinfection is supposed to be a favorable alternative for reclaimed water disinfection. This study compared the inactivation efficiency of E.coli by single ozone, single chlorine, and sequential ozone‑chlorine disinfection approaches. Notably, a single ozone or chlorine process could only achieve a log removal rate of up to 5 log, whereas the sequential ozone‑chlorine disinfection could completely inactivate microorganisms (7.3 log). For sequential ozone‑chlorine disinfection, the efficiency of chlorination was improved by 2.4%-18.5%. The synergistic effect mainly attributed to the elimination of chlorine consuming substances by ozone. Through the chlorine decay model (CRS) fitting and calculating the integral CT value, the enhancement ability of ozone to chlorine disinfection was quantified. By introducing an enhancement coefficient (β), a succinct and accurate model was established to estimate the inactivation rate of sequential ozone‑chlorine disinfection (mean absolute percentage error: 0.035). The results and methodology of this study are informative to optimize the disinfection units of WRPs.

Viral Interference as a Factor of False-Negative in the Infectious Adenovirus Detection Using Integrated Cell Culture-PCR with a BGM Cell Line

This study investigated the influence of viral interference on the detection of enteric viruses using the integrated cell culture (ICC)-PCR with a BGM cell line. It was possible to detect 10² plaque-forming units (PFU)/flask of enterovirus 71 (EV71) in spite of the presence of 10⁴ PFU/flask of adenovirus 40 (AdV40). Meanwhile, 10⁴ PFU/flask of AdV40 was not detected in the presence of 10² PFU/flask of EV71. This inhibition of AdV40 detection using ICC-PCR was attributable to the growth of EV71, because the addition of a growth inhibitor of EV71 (rupintrivir) neutralized the detection inhibition of AdV40. The growth inhibition of AdV40 under co-infection with EV71 is probably caused by the immune responses of EV71-infected cells. AdV is frequently used as a fecal contamination indicator of environmental water, but this study demonstrated that false-negative detection of infectious AdV using ICC-PCR could be caused by the co-existence of infectious EV in a water sample. The addition of rupintrivir could prevent false-negative detection of AdV using ICC-PCR. This study, therefore, emphasizes the importance of confirming the presence of multiple enteric viruses in a sample derived from environmental water prior to the application of ICC-PCR because the viral interference phenomenon may lead to the false-negative detection of target viruses.

Functional resilience of activated sludge exposed to Bacillus globigii and bacteriophage MS2

This study evaluated the effect of two biocontaminant surrogates on the activity and performance of activated sludge. In the presence of bacteriophage MS2 at 3.2 × 10⁸ PFU/ml, the peak respiration rates varied between 9.1 and 10.5 mg O₂/gVSS/hr, generally similar to the rates observed in negative controls. MS2 did not alter the molar CO₂-produced-to-O₂ consumed stoichiometry observed during respiration. Similar results were observed for Bacillus globigii (BG). Ethanol, a potential co-contaminant associated with biocontamination incidents, can inhibit initial oxygen uptake. MS2 and BG both adsorbed to activated sludge; post-exposure viability was confirmed for BG but not for MS2. This study is the first to evaluate the effects of BG and MS2 on activated sludge, and it presents a protocol that can be used in operational situations.

Synergetic suppression effects upon the combination of UV-C irradiation and berberine on Microcystis aeruginosa and Scenedesmus obliquus in reclaimed water: Effectiveness and mechanisms

The risk of harmful algal blooms (HABs) in the water recharged with reclaimed water is a bottleneck for water reuse. The suppression effects and mechanisms of the combination of UV-C and berberine on Microcystis aeruginosa and Scenedesmus obliquus in reclaimed water were investigated. Mono UV-C irradiation at 75 mJ cm^-2 could suppress the growth of M. aeruginosa for 7 d and that at 90 mJ cm^-2 could suppress the growth of S. obliquus for 5 d. UV-C irradiation combined with 0.2-2 mg L^-1 berberine lengthened the inhibition period of M. aeruginosa to 10- > 22 d and that of S. obliquus to 7- > 22 d and induced more rapid lethal effects on the harmful microalgal cells, in significant synergetic patterns. The combination of UV-C and berberine suppressed total, intracellular and extracellular microcystin-LR (MC-LR) more effectively and decreased the MC-LR quota significantly, which further reduced the risks of microcystin production and release. Furthermore, synergetic mechanisms of the combined treatments were systematically investigated from the aspects of photosynthetic system (photosynthetic activity and pigments), metabolic activity (ATP and membrane potential), oxidation stress (reactive oxygen species (ROS) and glutathione (GSH)), and apoptosis-like cell death (phosphatidylserine (PS) ectropion, caspase-3 activity and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positive rate). The combination treatment provided a joint attack of UV-C and berberine on photosynthetic transport chain of photosynthetic system II (PS II), and a synergetic pathway to achieve more severe disruptions in energy metabolism as well as aggravated oxidative stress. The accumulated ROS enhanced increases in programmed cell death (PCD) indicators of both microalgal species, which contributed to the enhancement effects on growth suppression. The results showed that the combination treatment achieved lower dose requirements of both UV-C irradiation and berberine for inducing the same inhibition effects on microalgal cells, which was promising to be applied in the HABs control of reclaimed water.

Assessing the public perceptions of treated wastewater reuse: opportunities and implications for urban communities in developing countries

Wastewater reuse has become an integral part of Integrated Water Resources Management and thus plays a role in securing the water needs for future generations. This study aimed at determining the perceptions of Canaanland, an emerging urban community in Ogun State, Nigeria, on treated wastewater reuse for several purposes. Data were collected through questionnaires administered to the city residents (n = 244). Findings revealed that the city was aware of the economic and environmental benefits of wastewater reuse but would prefer reuse schemes that involved less human contact such as flushing toilets, electricity generation, building construction, and car wash. The least preferred option was for potable purposes. The community also revealed that they would be willing to accept wastewater reuse as long as it is endorsed by medical doctors, university professors, and experts. However, 45.5% of the respondents were from the Covenant University academic environment. Also, an assessment was carried out to ascertain the implications and opportunities for wastewater reuse in the city. Findings indicated that wastewater reuse involves several complexities and interlinkages, which revolve around political and decisional factors, economic and social factors, environmental factors, and technological factors. From the study, policy and decisional suggestions and a wastewater process flow were developed for more efficient wastewater management within developing cities. A study was carried out on eight cities from developing nations that have created a framework for wastewater management using several approaches. Also, a summary of findings reveals that if adequately researched, cheap and alternative means of wastewater treatment and reuse could be developed for electricity generation, carwash, and firefighting for developing nations. The result of this research can be used to address public anxieties regarding wastewater-reuse practices. Additionally, this study hopes to aid successful wastewater management schemes in the foreseeable future.

A feasibility study of conducting surveillance for swine pathogens in slurry from North Carolina swine farms

Despite close contact between humans and animals on large scale farms, little to no infectious disease research is conducted at this interface. Our goal in this preliminary study was to explore if we could detect swine pathogens using a non-invasive, indirect approach through the study of swine slurry. From April to November 2018, 105 swine slurry samples were collected by farm personnel from waste pits at two sites on a swine farm in North Carolina. These samples were tested for DNA and RNA viruses using a real-time PCR and RT-PCR. Statistical analyses were performed to measure association between virus positive outcomes and potential predictors such as date of sample collection, weight of pigs, number of pigs in barn, temperature, and weather conditions. Overall, 86% of the samples had evidence of at least one of the targeted viruses. Ultimately, this study demonstrated the utility of conducting noninvasive surveillance for swine pathogens through the study of swine slurry. Such swine slurry surveillance may supplant the need to handle, restrain, and collect specimens directly from pigs thus providing an approach to emerging pathogen detection that appeals to the swine industry.

Paradigm shifts and current challenges in wastewater management

Wastewater is a significant environmental and public health concern which management is a constant challenge since antiquity. Wastewater research has increased exponentially over the last decades. This paper provides a global overview of the exponentially increasing wastewater research in order to identify current challenges and paradigm shifts. Besides households, hospitals and typical industries, other sources of wastewater appear due to emerging activities like hydraulic fracturing. While the composition of wastewater needs constant reassessment to identify contaminants of interest, the comprehensive chemical and toxicological analysis remains one of the main challenges in wastewater research. Moreover, recent changes in the public perception of wastewater has led to several paradigm shifts: i) water reuse considering wastewater as a water resource rather than a hazardous waste, ii) wastewater-based epidemiology considering wastewater as a source of information regarding the overall health of a population through the analysis of specific biomarkers, iii) circular economy through the implementation of treatment processes aiming at harvesting valuable components such as precious metals or producing valuable goods such as biofuel. However, wastewater research should also address social challenges such as the public acceptance of water reuse or the access to basic sanitation that is not available for nearly a third of the world population.

Dialysis as a new pre-treatment technique for online bacterial counting

Real-time bacteriological counting technology is capable of providing an online profile of bacterial removal during the wastewater treatment process, and can enhance the safety of recycled water for potable water reuse. However, autofluorescence emanating from dissolved organic compounds present in treated wastewater interferes with the analysis. In this study, a novel approach is adopted, viz., dialysis treatment for the removal of dissolved interfering substances from treated wastewater, and the efficiency of this treatment protocol is evaluated as a pre-treatment technique for real-time bacteriological counting. Dialysis using membranes having a molecular weight cut-off (MWCO) of 1000 kDa and 6-8 kDa were found to successfully reduce the intensity of autofluorescence emitted from the interfering substances; whereas the courser dialysis membrane having a MWCO of 1000 kDa was found to be more effective in removing the interfering substances. Here we demonstrate for the first time that continuous online dialysis treatment aids in the direct determination of the bacterial counts in ultrafiltration- and membrane bioreactor-treated wastewaters. The results of the study indicate that the dialysis pre-treatment technique is effective for continuously reducing the concentration of interfering substances in treated wastewater, and thus allows for direct online counting of bacteria.

Cryptosporidium and Giardia in urban wastewater: A challenge to overcome

This study aimed to quantify Giardia and Cryptosporidium in disinfected water reuse samples from two Wastewater Treatment Plants (A and B), which were quantified by USEPA 1693/2014 Method. Giardia was found in 35.8% of the total samples (<0.03 to 16 cysts/L) while Cryptosporidium in 30.2% (<0.03 to 25.8 oocysts/L). This study highlights the presence of both parasites in water for reuse despite treatment processes for their removal, which means there is a challenge to overcome. Their presence is preoccupant even though in low concentrations because the infectivity dose is low coupled with high prevalence in the global population. The practice of water recycling is valuable for sustainable water management and it is in line with Sustainable Developments Goals but should not threaten human health. Tackling this issue is more critical in developing countries because treatment processes are often more limited, the monitoring data from water reuse are not always available, the lack of regulation for water reuse quality and the lack of planning for its sustainable usage.

Water allocation and governance in multi-stakeholder environments: Insight from Axios Delta, Greece

This article deals with stakeholders' interactions and institutional capacity influencing water resource management where competitive demands co-exist. For the case study area of Axios Delta, Northern Greece, a water deficit in the agricultural sector, an unmet environmental flow and a reduced capacity for urban supply during drought conditions are observed. An egocentric network analysis based on desk-study and a series of semi-structured stakeholder interviews reveals how weak stakeholder ties lead to ineffective multilevel governance and, as a result, low water efficiency practices. There is a lack of understanding of other users' priorities as well as of the risks related to climate change and/or seasonal variability. This is reflected in the flat rate abstraction licence for agricultural purposes which reduces environmental flow to below acceptable standards. There is no transboundary cooperation between Greece and the Republic of North Macedonia which hinders an integrated management approach. A limited exchange of information to support an evidence-based allocation plan is observed. Suitable interventions identified through a DPSIR approach are evaluated in a multi-criteria analysis considering cost effectiveness, delivered benefits as well as ease of implementation. Suitable technical practices include the development of a local and catchment-scale monitoring network for surface water and groundwater, climate-adaptive agriculture and treated-water reclamation. Updated management policies involve the institutional prioritisation of environmental flow through an adaptive allocation plan as well as the strengthening of transboundary cooperation. This research shows how the coordination of aggregated diverging interests in multilevel multi-stakeholder environments appears to be key in supporting positive water budgets in an uncertain climate future.

Water reclamation and reuse

Literature published in 2018 pertinent to water reclamation and reuse has been classified into five topics: safe reuse, treatment technologies, management, assessment, and case studies. Researches have been conducted to develop new technologies and improve conventional treatments for achieving sustainable wastewater reclamation, and increasing efforts have been made to facilitate safe water reuse. PRACTITIONER POINTS: The way of publicity greatly influences people's acceptance of water reuse and willingness to purchase produce irrigated with recycled water. Integrated process is the most commonly used treatment technology to reclaim water. There is a lack of local or regional regulatory and policy for sustainable water management.

Performance of wastewater reclamation systems in enteric virus removal

Analysis of virus removal by tertiary or advanced sewage treatment processes is an emerging topic due to importance of reusing water on a global level. This study aimed to monitor important human viral pathogens: the human adenovirus (HAdV), JC polyomavirus (JCV) and Species A rotaviruses (RVA) in urban sewage, secondary effluents and reclaimed water from metropolitan São Paulo (MSP), Brazil. Four large wastewater treatment plants (WWTPs) in MSP were sampled monthly during a one-year period (April 2015 to March 2016). The viruses were quantified by quantitative PCR (qPCR), and HAdV viability was tested by the integrated cell culture (ICC)-qPCR assay. WWTPs are composed of activated sludge processes and different tertiary treatments (coagulation/sedimentation, sand-anthracite filters, membrane bioreactors (MBRs)/reverse osmosis (RO) and disinfection by chlorination). Physicochemical parameters were also evaluated to verify association with density of viruses detected in different treatment stages. HAdV, JCV and RVA were consistently detected (100%) in the sewage influent samples (range: 10⁶-10⁸ genome copies GC/L). In the secondary effluent, HAdV was detected in 100% (48/48) of the analysed samples, JCV in 85.4% and RVA in 97.9% (range: 10⁴-10⁷ GC/L for all viruses tested). HAdV was the most frequently detected virus in the tertiary effluent (62.2%) (28/45), exhibiting a viability between 0 and 44% of the tested samples in the wastewater reclamation systems. The MBR/RO systems demonstrated better virus removal efficiencies (range: 2.3-2.9 log₁₀). Temperature, pH, turbidity and total organic carbon presented association with the viral density in the reclaimed water samples. Presence of viruses in treated effluents can indicates health risks depending on uses of recovery water. Further risk assessment studies should be conducted to better assess health risks under different exposure scenarios for water recovery in urban settings.

Aptness of Escherichia coli host strain CB390 to detect total coliphages in Colombia

Fecal bacteria have been used for more than a century as indicators of fecal contamination in water. In recent years, the monitoring of somatic and F-specific coliphages has been gradually included in guidelines and regulations as an additional parameter to reinforce water safety. The Escherichia coli host strain CB390 was tailored to detect both somatic and F-specific coliphages in a single test. The efficacy of this strain for bacteriophage detection, previously evaluated in Western Europe and North America, was assessed here for the first time in South America. The detection of somatic and F-specific coliphages by the strain CB390, as well as by standardized methods, was performed in drinking and river water and municipal and abattoir wastewaters. No statistical difference was found in the numbers of total coliphages detected by strain CB390 and the sum of somatic and F-specific coliphages determined separately by the standardized ISO methods. The data presented here provide further validation of the effectiveness of the host strain E. coli CB390 for the detection of total coliphages in waters in a single test and demonstrate its suitability for application in upper-middle income countries of the Americas (World Bank category).

Epidemiological Evidence and Health Risks Associated With Agricultural Reuse of Partially Treated and Untreated Wastewater: A Review

The use of partially treated and untreated wastewater for irrigation is beneficial in agriculture but may be associated with human health risks. Reports from different locations globally have linked microbial outbreaks with agricultural reuse of wastewater. This article reviews the epidemiological evidence and health risks associated with this practice, aiming toward evidence-based conclusions. Exposure pathways that were addressed in this review included those relevant to agricultural workers and their families, consumers of crops, and residents close to areas irrigated with wastewater (partially treated or untreated). A meta-analysis gave an overall odds ratio of 1.65 (95% CI: 1.31, 2.06) for diarrheal disease and 5.49 (95% CI: 2.49, 12.10) for helminth infections for exposed agricultural workers and family members. The risks were higher among children and immunocompromised individuals than in immunocompetent adults. Predominantly skin and intestinal infections were prevalent among individuals infected mainly via occupational exposure and ingestion. Food-borne outbreaks as a result of crops (fruits and vegetables) irrigated with partially or untreated wastewater have been widely reported. Contamination of crops with enteric viruses, fecal coliforms, and bacterial pathogens, parasites including soil-transmitted helminthes (STHs), as well as occurrence of antibiotic residues and antibiotic resistance genes (ARGs) have also been evidenced. The antibiotic residues and ARGs may get internalized in crops along with pathogens and may select for antibiotic resistance, exert ecotoxicity, and lead to bioaccumulation in aquatic organisms with high risk quotient (RQ). Appropriate mitigation lies in adhering to existing guidelines such as the World Health Organization wastewater reuse guidelines and to Sanitation Safety Plans (SSPs). Additionally, improvement in hygiene practices will also provide measures against adverse health impacts.