A risk-based approach for developing standards for irrigation with reclaimed water

Making waves: Promoting municipal water reuse without a prevailing scarcity driver

The wealth of water reuse research in scarcity and/or rapid urbanisation contexts has underpinned significant change in many relatively water scarce contexts. Less progress has been achieved in water rich contexts; a fact illustrated by the lack of change on the ground. The Climate Emergency demands that all municipalities urgently contribute to more efficient resource management of water. Consequently, to advance municipal scale reuse projects in locations where scarcity is not forcing the issue, for example Scotland, there is a need to predicate water reuse on different drivers, specifically climate change and the circular economy. Moreover, greater contextual sensitivity needs to be applied when exploring barriers to reuse to more critically exploit opportunities, for example avenues to reform complex regulatory frameworks, different contingencies around trust, and different potential degrees of the yuck factor. To achieve this, new initiatives need to be urgently undertaken to consider the barriers to reuse that will not be swept aside by the imperative of  scarcity. The notion of a yum factor, whereby positive sentiments are nurtured to combat instinctive repugnance, coined as yuck by the bioethicist Arthur Caplan, is advanced as a strategic objective to promote more rapid expansion of municipal scale reuse.

Exploring acceptable risk in engineering and operations research and management science by bibliometric analysis

As the decision-making basis for "safety" in risk management and risk assessment activities, acceptable risk has always been an important topic of risk-related research. Based on the records in the Science Citation Index Expanded database and Social Sciences Citation Index database via the Web of Science Core Collection, 1124 articles or reviews related to acceptable risk in engineering and operations research and management science were retrieved. These documents, published between 1961 and 2021, covered 3056 authors, 75 countries/territories, 1296 institutions, and 323 journals. In this study, bibliometric data such as annual growth trends were analyzed by using descriptive statistics. Through the co-occurrence maps created by CiteSpace and Gephi, the most productive and influential countries/territories, institutions, and authors as well as their cooperation networks were identified. Further analysis was conducted to determine the core publications and publication sources in this field through co-citation analysis. Insights into focus areas and research topics over time were obtained through keyword co-occurrence analysis. This study provides a macroscopic overview of acceptable risk research and may help researchers better understand this research field and predict its dynamic directions.

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.

Cryptosporidium and Giardia in Biogas Wastewater: Management of Manure Livestock and Hygiene Aspects Using Influent, Effluent, Sewage Canal Samples, Vegetable, and Soil Samples

Cryptosporidium and Giardia are two water- and foodborne protozoan parasites that can cause diarrheal diseases. Poor microbial quality, sanitation conditions, and hygiene practices at exposure to biogas wastewater are important risk factors for human and animal infection. This study highlights the presence and level of both parasites in the environment in relation to biogas waste reuse in Vietnam. A total of 239 samples were collected from different types of samples in the studied districts in Bac Giang province in 2020 via direct immunofluorescent detection to study the occurrence of Cryptosporidium spp. and Giardia spp. (oo)cysts. Among the samples, Cryptosporidium was found in 19 (7.9%) with concentration from 1.10⁴ to 3.10⁵ oocysts/100 mL, while Giardia in 40 (16.7%) with concentration from 1.10⁴ to 2.10⁶ cysts/100 mL, respectively. In detail, the results show that the percentages of positive detection of Cryptosporidium spp. and Giardia spp. in influent, effluent, sewage canal, and vegetables were 13.1% (11/84), 6.0% (5/83), 15.4% (2/13) and 5.9% (1/17) and 26.2% (22/84), 7.2% (6/83), 7.7% (1/13) and 5.9% (1/17), respectively. The results show a trend of decreasing Cryptosporidium and Giardia densities, without statistical significance. Although these parasites decreased after biogas treatment, the remaining loads observed in biogas effluent can reach the watercourses and soil receiving it. Further investigations are needed to contribute to a general understanding of the risk of protozoan parasites, as well as strategies to control and reduce the contamination of environmental water sources and plants and reduce the burden of the pathogens in biogas wastewater in Vietnam.

Norovirus transmission mitigation strategies during simulated produce harvest and packing

In the agricultural setting, core global food safety elements, such as hand hygiene and worker furlough, should reduce the risk of norovirus contamination on fresh produce. However, the effect of these practices has not been characterized. Using a quantitative microbial risk model, we evaluated the individual and combined effect of farm-based hand hygiene and worker furlough practices on the maximum risk of norovirus infection from three produce commodities (open leaf lettuce, vine tomatoes, and raspberries). Specifically, we tested two scenarios where a harvester's and packer's norovirus infection status was: 1) assumed positive; or 2) assigned based on community norovirus prevalence estimates. In the first scenario with a norovirus-positive harvester and packer, none of the individual interventions modeled reduced produce contamination to below the norovirus infectious dose. However, combined interventions, particularly high handwashing compliance (100%) and efficacy (6 log10 virus removal achieved using soap and water for 30 s), reduced produce contamination to <1-82 residual virus. Translating produce contamination to maximum consumer infection risk, 100% handwashing with a 5 log10 virus removal was necessary to achieve an infection risk below the threshold of 0.032 infections per consumption event. When community-based norovirus prevalence estimates were applied to the harvester and packer, the single interventions of 100% handwashing with 3 log10 virus removal (average 0.02 infection risk per consumption event) or furlough of the packer (average 0.03 infection risk per consumption event) reduced maximum infection risk to below the 0.032 threshold for all commodities. Bundled interventions (worker furlough, 100% glove compliance, and 100% handwashing with 1-log10 virus reduction) resulted in a maximum risk of 0.02 per consumption event across all commodities. These results advance the evidence-base for global produce safety standards as effective norovirus contamination and risk mitigation strategies.

Spatial distribution of heavy metal contamination and uncertainty-based human health risk in the aquatic environment using multivariate statistical method

Heavy metal contamination in the aquatic environment is one of the most serious health issues worldwide. In this study, an evaluation framework is developed to identify the sources and health risk of heavy metals (i.e., As, Hg, Cr, Cu, Zn, Pb, and Cd) contamination in the North Canal of Fengtai District, China, which is based on multiple approaches, including multivariate statistical method, health risk assessment, and uncertainty analysis. Spatial distribution of these heavy metals could exhibit their impact on the aquatic environment. Pearson's correlation analysis shows that a majority of the correlations between different heavy metals are not significant due to the differences in sources of heavy metals. Principal component analysis indicates that there are four principal components to explain 91.381% of the total variance. Moreover, health risk reveals that hazard quotient values are in low levels, ranging from 0.48 to 0.74, relative higher quotient levels could be observed in the northern section. The carcinogenic risk of Cd has exceeded the acceptable level in S1, S3, and S7. Sensitivity analysis ensures the reliability of health risk assessments. Furthermore, some specific recommendations are given to help decision-makers develop more comprehensive strategies for improving water environment quality.

Evaluating the health risks of heavy metals from vegetables grown on soil irrigated with untreated and treated wastewater in Arba Minch, Ethiopia

Available freshwater scarcity significantly affects sustainable food production for the rapidly growing population. This problem has forced people in most parts of the world to use wastewater as a viable solution. However, wastewater reuse has some deleterious effects on human and environmental health. This study was designed to investigate the health risks (HRs) of heavy metals (HMs) from vegetables irrigated with untreated and treated wastewater. The composite wastewater was collected at various sites in Arba Minch town and subjected to aerobic-anoxic treatment. Treated and untreated wastewater (UTW) was used to irrigate vegetables (lettuce, cabbage and tomato), and HM results were compared with the control (tap water) and standards. Water, soil and vegetables were investigated for various physical and chemical properties. Human health effects due to vegetable consumption were analyzed using HR- index (HRI), target hazard quotient (THQ) and hazard index (HI). The results revealed that most of the water quality indexes were significantly enhanced after aerobic-anoxic treatment, suggesting that wastewater collected from different sites was suitable for biodegradation. Soil physicochemical analyses also showed that pH, cation exchange capacity, organic carbon and organic matter were higher for UTW irrigated soil. Heavy metal concentrations were relatively greater in soils than water used for irrigation purposes and vegetables. The HM concentration in vegetables was higher for UTW than for treated and tap water irrigated vegetables. In vegetables, the order of HM content was Fe > Mn > Zn > Pb > Cu > Cd. Tomato followed by cabbage and lettuce accumulated significant amount of HMs (Fe > Mn > Zn > Pb > Cu > Cd) in their different organs (fruit/leaf>root>stem). The individual and combined health indexes (HRI, THQ and HI) showed that Pb and Cd have values greater than unity for wastewater irrigated vegetables, which could result in non-carcinogenic disease for short/lifetime exposure in adults and children. Overall, consumption of vegetables can be safer when grown with treated effluent than with UTW.

Prevalence of Cryptosporidium and Giardia in vegetables in Iran: a nineteen-years meta-analysis review

Cryptosporidium and Giardia are two major protozoa reported from vegetables and environment. The prevalence of these parasites supposes to be different regarding the climate zones. This review aimed to evaluate the prevalence of Cryptosporidium and Giardia in vegetables according to the major climate zones in Iran. The results showed pooled prevalence 7% (95% CI: 2%, 14%) and 4% (95% CI: 3%, 6%) for Cryptosporidium spp., and Giardia spp., respectively. The prevalence of Giardia spp. in mountain, desert and semi-desert, and Mediterranean regions was 4% (95% CI: 2%, 6%), 5% (95% CI: 3%, 8%) and 7% (95% CI: 1%, 18%), respectively. Cryptosporidium spp. was reported 8% (95% CI: 0%, 65%), 6% (95% CI: 0%, 18%) and 4% (95% CI: 0%, 77%) from mountain, desert and semi-desert, and Mediterranean climate zones, respectively. This review suggests the higher prevalence of Giardia and Cryptosporidium in Mediterranean and mountain regions, respectively.

Quality change mechanism and drinking safety of repeatedly-boiled water and prolonged-boil water: a comparative study

Quality, safety and potability of repeatedly-boiled water (RBW) and prolonged-boil water (PBW) lead to concern and even misgivings in the public from time to time, especially in China, and other societies have a habit of drinking boiled water, with improvements of living standards and owing to increasing concerns for human health. This phenomenon is mainly attributed to the fact that the conclusions drawn from existing scientific experiments could not respond well to the concerns. In order to make up for this deficiency, tap water was selected to carry out RBW and PBW experiments independently. The quality changes of RBW and PBW show very similar trends that are not as great as might be imagined, and both are impacted by the tap water quality and the physiochemical effects. The dominating physiochemical effects are the water evaporation and the resulting concentration of unreactive components (most dissolved components), which can be easily explained by the existing evaporation-concentration theory. The results show that tap water will be still safe and potable after being frequently boiled or after having undergone prolonged boiling, as long as it satisfies the sanitary standards of drinking water prior to heating. Therefore, there is no need to worry about drinking RBW or PBW in daily life.

Waterless Urinals Remove Select Pharmaceuticals from Urine by Phase Partitioning

We investigated the potential for waterless urinal sealants fluids to remove pharmaceuticals from urine. ¹H NMR, FTIR, and GC/MS characterization of the fluids indicated that they are mostly composed of aliphatic compounds. Removal of ethinyl estradiol was >40% for two of the three sealant fluids during simulated urination to a urinal cartridge but removal of seven other compounds with greater hydrophilicity was <30%. At equilibrium with Milli-Q water, ≥ 89% partitioning to the sealant phase was observed for three compounds with pH adjusted log K_ow (log D_ow) > 3.5. At equilibrium with synthetic urine, removal ranged widely from 2% to 100%. K_ow was poorly correlated with removal for both matrices at equilibrium, but D_ow was correlated with removal from synthetic urine for two of the three sealants, indicating that ionization and hydrophilicity control partitioning between the urine and sealant phases. To improve removal during urination, where equilibrium is not achieved, we increased the hydraulic retention time 100-fold over that of typical male urination. Removal of specific hydrophobic compounds increased, indicating that both hydrophobicity and kinetics control removal. Removal of ethinyl estradiol was ≥90% for all sealants in the increased hydraulic retention time experiment, demonstrating the potential for implementation to female urinals.

Health assessment of spatial and temporal distribution of arsenic in soils irrigated with reclaimed water

Reclaimed water is an important water resource for agricultural irrigation. Based on the systematic analysis of experimental data, this paper studies the spatiotemporal transformation and distribution of As in soil-crop system. Through the comparison with groundwater irrigation, reclaimed water irrigation was tested and studied in connection with the greenhouse vegetables in the growing season. The accumulation, distribution and transportation of As in different depths of soil within 7 days after reclaimed water irrigation were analyzed and discussed. The results showed that the concentration of As was the highest on the first day after irrigation; it was the highest at the depth of 100 cm on the third day after irrigation, but its concentration in the topsoil slightly decreased; from the fifth to the seventh day, the concentrations of As in the different layers of soil were almost the same, but it was the highest at the depth of 80-120 cm; and it decreased slightly with the increase in depth when the depth was less than 120 cm. As in soil during the growing season varied as the frequency of irrigation increased. The specific situation was as follows: as the accumulated As in the topsoil increased, the increased As at the depth of 80-120 cm would become less and the concentration of As at 200 cm would fall. Therefore, when the appropriate concentration of reclaimed water is used for irrigation, the concentration of As in the deep layer soil will comply with the standard limits of GB15618-1995 and the irrigation with reclaimed water of appropriate concentration will not cause As pollution.

Health evaluation on migration and distribution of heavy metal Cd after reclaimed water drip irrigation

The utilization of reclaimed water is one of the effective measures to save water resources. The study of reclaimed water irrigation and the analysis of how heavy metals migrate in the soil, especially their movement laws, have important theoretical and practical significance. It helps to predict the risk of heavy metals in foods, which protects our health and safety. In this paper, we studied the accumulation and distribution of heavy metal Cd in soils with reclaimed water drip irrigation in greenhouses during growing season, comparing the effects with groundwater drip irrigation. The results show that the Cd concentration in the surface soil is the highest on the second day after drip irrigation. It will be the highest on the fourth day in the depth of 100 cm, and then, it will decrease slightly. During the period of the sixth day to the eighth day, the Cd concentrations are similar in each depth, and it is the highest in the depth of 0-40 cm and 80-120 cm, but the Cd concentration decreases with the lower depth below 120 cm. By utilizing proper ways of reclaimed water drip irrigation, the Cd concentration in the deep soil will not violate the standard limits of GB15618-1995, which will not cause Cd pollution.

Risk-Yuck Factor Nexus in Reclaimed Wastewater for Irrigation: Comparing Farmers’ Attitudes and Public Perception

The successes and failures of water reuse schemes are shaped by complex interrelationships between technological, economic, and socio-political factors. However, it has long been recognized that the main challenges to more effective water management are largely social rather than technical. This article reviews the recent literature (2007–2017) to analyze driving factors associated with farmers’ concerns and public perception of reclaimed wastewater for irrigation. The aim of the paper is to synthetize how both environmental and health risks and the yuck factor could be addressed in order to promote mutual understanding between farmers and the public. Results show: (1) how farmers and the public perceive environmental and health risks in a similar way, (2) how the yuck factor is more noticeable for the public than farmers, and (3) how constructed wetlands, reclaimed water exchange consortiums, product certification, and direct site visits to water reuse infrastructure could be promoted in order to foster understanding between farmers and the public. The article concludes by providing key research questions for managers and public authorities relating to how to focus on the study of technical and social issues related to water reuse.