Model-based prediction of bathing water quality in a lake polluted by fecal coliform bacteria from combined sewer overflows

Towards stormwater reuse risk management plans: Methodology and catchment scale evaluation of QMRA

The reuse of stormwater represents a potential option for meeting water demands in water stressed regions as well as preventing and mitigating diffuse pollution of receiving water bodies. Particularly, the elaboration of a risk management plan for stormwater reuse may help to understand associated environmental and public health risks and design fit-for-purpose water treatment processes. In this work, it is presented an innovative methodology to perform quantitative microbial risk assessment (QMRA) for stormwater reuse by using data simulated by SWMM software. Particularly, 210 rain events were simulated by SWMM after qualitative and quantitative calibration of the sewer network model of the city of Cupra Maritima (Italy) to identify sewer overflows. Obtained concentrations of pathogens (i.e., E. coli, Campylobacter) in overflows from each critical spillway were fitted by theoretical distribution curves. Hence, QMRA for Campylobacter was performed by Monte Carlo simulation and by linking observed overflows to the exposure events of stormwater reuse for the scenario of 1) municipal irrigation, 2) garden irrigation and 3) toilet flushing as defined by the Australian Guideline for water recycling. Furthermore, QMRA analysis was repeated after simulation of sewer overflow treatment by nature-based solution (NBS) with and without disinfection (UV and performic acid - PFA). Stormwater treatments were simulated by applying uniform distributions of expected range of bacteria log removals. Results showed that stormwater treatment by nature-based solution and disinfections (PFA dose of 2.5-5 mg/L) were able to reduce the risk of Campylobacter infection to acceptable level for most of spillways in the three investigated reuse scenarios. In addition, produced data were elaborated to identify critical overflows discharging in bathing water according to the indications of the EU bathing directive.

Feasible cultivation of Verrucodesmus verrucosus on sterile raw wastewater for energy purposes: a case study in Mexico

In this study, wastewater from a sewage treatment plant was used to culture the microalga, Verrucodesmus verrucosus. The ability of microalgae to adapt to adverse environments and produce high lipid concentrations was evaluated using different media, including sterile and non-sterile media and a control medium. The analysis showed that the control medium (distilled water sample enriched with fertilizer) removed 80.35% ammonium, 32.71% phosphate, and 83.86% nitrate. The sterile raw effluent removed 78.91% of ammonium, 83.44% of phosphate, and 98.82% of nitrate. The optimal conditions for biomass production were sterile raw wastewater, which produced 383.3 mg L-1 of biomass, 2.5% of total lipids, and an average lipid production of 9.31 mg L-1. Microalgae can grow and consume inorganic nutrients under adverse environmental conditions such as in raw wastewater, which is of great importance because it is a pollutant that negatively affects the environment and society. However, wastewater may represent a viable alternative substrate, allowing the generation of high-value products, such as lipids. Furthermore, the specificity of microalgal morphotypes must be evaluated, because each has specific metabolic plasticity. Verrucodesmus verrucosus is a microalga that has not been evaluated in bioremediation processes of wastewater with and without the presence of biotic factors. Therefore, the present study provides a viable alternative for this biological process, with the potential to store metabolites of interest in the industry.

Faecal contamination in China: Trends, sources, and driving mechanisms

Faecal contamination of surface waters is a global public health and economic burden. Here, we constructed a 30-year dataset to analyse the spatiotemporal trends and driving mechanisms of faecal coliforms (FCs) in China. We found that previous national policies to reduce water pollution have significantly improved the quality of surface water and, correspondingly, faecal contamination. However, the downward trend in FC levels has been more gradual than that for physico-chemical pollutants, and this trend may be exaggerated. Our results show that the driving mechanisms of faecal pollution were seasonal and complex. During the dry season, forests and grasslands were the source landscapes that exacerbated faecal pollution; during the wet season, urbanisation dominated, highlighting China's poorly designed drainage systems. Our projections revealed that faecal contamination will continue to worsen from 2022 to 2035, highlighting the need for pollution control. In the future, faecal indicators should be included in routine monitoring, evaluation, and assessment at the national level. Moreover, coordinated design of forest, grassland, and wetland landscapes is recommended for faecal pollution control at the regional level, whereas stormwater-related source control needs to be further strengthened at the urban level.