Environmental performance of an integrated water supply and wastewater system through life cycle assessment - A Brazilian case study

Life cycle environmental impacts of urban water systems in China

Urban water systems in China are facing multiple challenges, including rapid urbanisation, climate change and infrastructure ageing. It is crucial to evaluate their environmental performance from a holistic perspective in planning and management processes. To the best of our knowledge, there is a lack of nationwide life cycle assessment (LCA) studies on China's urban water systems that cover all system stages. Therefore, this study aims to present a comprehensive and nationwide LCA analysis that pinpoints the environmental hotspots and their major sources across China. This study was conducted based on water utility databases at the province level, covering water abstraction and treatment, waterwork sludge treatment, water distribution, sewage collection, stormwater drainage, wastewater treatment and sewage sludge treatment. Nine environmental impact categories were calculated and analysed. The results reveal the inequity of environmental impacts across provinces, with overall impacts geographically higher in the east and south, lower in the west and north. However, at the functional unit level, the impacts in the northern and northeastern provinces are higher than other regions. Most environmental categories are dominated by multiple water system stages. The analyses of underlying drivers found that purchased electricity is the primary source of several environmental impacts. This study provides a holistic understanding of the environmental performance of China's urban water systems, offers some insights for comprehensive decision-making support on sustainable water system management, and can also serve as a benchmark for future scenario analysis to explore options for reducing environmental impact.

Modular life cycle assessment approach: Environmental impact of rainwater harvesting systems in urban water systems

The environmental assessment of urban water systems through life cycle analysis can be facilitated by using a modular approach. This study aimed to use such an approach to assess the impact of implementing rainwater harvesting systems in buildings in the urban environment during their lifespan, from manufacture to disposal. For this purpose, urban systems were divided into components (water treatment plant, potable water distribution, consumer water use, wastewater collection and wastewater treatment plant). The impacts were quantified using the ReCiPe 2016 H impact assessment method, which considers eighteen impact categories. A case study was carried out in the Belém river basin in central Curitiba, southern Brazil, to validate the method. The results showed a reduction of environmental impacts of up to 23.0 % on water treatment plants, up to 19.0 % on potable water distribution and up to 11.3 % on wastewater treatment plants with the implementation of rainwater harvesting systems. The consumer component was the most significant contributor in eight and seven impact categories in the scenarios with and without rainwater harvesting, respectively. Despite the increased infrastructure materials, the results showed potential for environmental impact reduction with rainwater harvesting, mainly in urban water systems' operation process (energy and chemicals consumption). By analysing the total impacts, implementing rainwater harvesting reduced the impacts in eleven out of eighteen impact categories analysed (up to 11.0 % reduction). The principal reductions occurred in ozone depletion, ionising radiation and water use. Finally, the modular life cycle assessment approach proved to be a comprehensive analysis, which can aid in the analysis and decision-making for different scenarios.

Sustainability assessment of waste and wastewater recovery for edible mushroom production through an integrated nexus. A case study in Lazio

With a global population of eight billion people, improving the sustainability and nutritional quality of diets has become critical. Mushrooms offer a promising solution because of their nutritional value and ability to be grown from agricultural residues, in line with the circular economy. This study, therefore, focuses on assessing the environmental compatibility of Agaricus bisporus mushroom production in Italy, the world's third largest per capita consumer, by using a Life Cycle Assessment (LCA) and an integrated Water-Energy-Nitrogen-Carbon-Food (WENCF) nexus analysis. The LCA results reveal that for a functional unit of 23,000 kg of the substrate, the production process emits 2.55 × 104 kg of CO2 eq. Sensitivity analysis shows that changing input quantities can reduce environmental impacts by about 5 %. In addition, one scenario evaluates the environmental effects of recycling resources by introducing water and ammonium sulfate from scratch instead of continuous recycling, along with water purification. The study shows that sustainable food production can mitigate resource depletion, climate-altering emissions, and intersectoral competition. Using agro residues for mushroom cultivation and optimizing resource management contribute to environmental sustainability. This approach could not only improve the resilience and efficiency of the food system but could also improve the sustainability of diets. In conclusion, this study highlights the importance of adopting sustainable and circular approaches in mushroom production to address global challenges related to food sustainability.

Sustainability for wastewater treatment: bioelectricity generation and emission reduction

This review covers the technological measures of a self-sustainable anaerobic up-flow sludge blanket (UASB) system compared with an aerobic activated sludge process (ASP) for wastewater treatment plants (WWTPs). The ASP requires a huge amount of electricity and chemicals and also results in the emission of carbon. The UASB system, instead, is based on greenhouse gas (GHG) emission reduction and is associated with biogas production for cleaner electricity. WWTPs including the ASP system are not sustainable due to the massive financial power required for clean wastewater. When the ASP system was used, the amount of production was estimated to be 10658.98 tonnes CO₂eq-d^- of carbon dioxide. Whereas it was 239.19 tonnes CO₂eq-d^-1 with the UASB. The UASB system is advantageous over the ASP system as it has a high production of biogas, needs low maintenance, yields a low amount of sludge, and is also a source of electricity that can be used as a power source for the WWTPs. Also, the UASB system produces less biomass, and this helps in reducing costs and maintaining work. Moreover, the aeration tank of the ASP needs 60% of energy distribution; on the other hand, the UASB consumes less energy, approximately 3-11%.

Analysis of the Electricity Consumption in Municipal Wastewater Treatment Plants in Northeast China in Terms of Wastewater Characteristics

A municipal wastewater treatment plant plays an important role in treating urban sewage and reducing the quantity of pollutants discharged into rivers. However, the energy consumption of the municipal wastewater treatment industry is large. High energy consumption indirectly produces ecological damage, accelerates the energy crisis, and increases carbon emissions. For energy conservation and emission reduction in wastewater treatment plants, it is first necessary to identify the main factors influencing energy consumption. Electricity consumption accounts for more than 80% of the energy consumption of wastewater treatment plants. Wastewater quantity and wastewater quality have become the key influencing factors of energy conservation and consumption reduction in wastewater treatment plants. In this study, a municipal wastewater treatment plant in Northeast China was selected as the research object, and the measured data, such as air temperature, wastewater quantity, wastewater quality, and electricity consumption of the plant from 2017 to 2020 were statistically analyzed to explore the influences of temperature and wastewater quantity and wastewater quality indicators of influent and effluent on energy consumption. Firstly, the range of influent quantity in the wastewater treatment plant was large. The influent quantity in summer was high because some rainwater entered the sewage treatment plant. In winter, average daily electricity consumption (ADEC) was higher than that in summer. The relationship between ADEC and the wastewater quantity showed a positive correlation, and ADEC slowly increased with the increase in wastewater quantity. Electricity consumption per unit of wastewater (UEC) was negatively correlated with the wastewater quantity, but the correction coefficient in winter was larger than that in summer. Secondly, the ranges of chemical oxygen demand (COD_Cr) and ammonia nitrogen in influent were large, and the ranges of COD_Cr and ammonia nitrogen in effluent were small. Influent COD_Cr concentration was negatively correlated with influent ammonia nitrogen concentration. ADEC increased slightly with the increase in influent COD_Cr concentration. In winter, the increasing trend of ADEC with the influent COD_Cr concentration was higher than that in the summer. The increasing trend of UEC with the increase in influent COD concentration in summer was more significant than that in winter. Thirdly, influent COD_Cr in 11.6% of the samples exceeded the corresponding designed value, and influent ammonia nitrogen concentration in 41.4% of the samples exceeded the corresponding designed value. Effluent COD_Cr in 10.6% of the samples exceeded the First Level Class B standard in "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants (GB18918-2002)", and unqualified COD_Cr in 94% of the effluent samples was ascribed to the unqualified ammonia nitrogen concentration in the influent samples. The electricity consumption level under abnormal conditions was higher than that under normal conditions. Fourthly, ADEC was positively correlated with the average daily COD_Cr reduction. The correction coefficient of ADEC with average daily COD_Cr reduction was greater in winter than that in summer. Fifthly, the average electricity consumption per unit of wastewater was close to the national average energy consumption, displaying the characteristics of high energy consumption in winter and low energy consumption in summer. The correlation analysis results of unit electricity consumption and temperature showed that when it was below 0 °C, the lower the temperature, the higher the electricity consumption. In Northeast China, the influences of seasons and temperatures on the electricity consumption of sewage plants were obvious. Accordingly, it is necessary to implement the diversion of rainwater and sewage, reduce the discharge of unqualified wastewater from enterprises, and take thermal insulation measures in winter. In addition, activated sludge microorganisms suitable for a low temperature area and the optimal scheduling of sewage pipe networks can also improve the operation and management of sewage treatment plants.