This paper evaluates the performance and potential of a full-scale hybrid multi-soil-layering (MSL) system for the treatment of domestic wastewater for landscape irrigation reuse. The system integrates a solar septic tank and sequential vertical flow MSL and horizontal flow MSL components with alternating layers of gravel and soil-based material. It operates at a hydraulic loading rate of 250 L/m2/day. Results show significant removal of pollutants and pathogens, including total suspended solids (TSS) (97%), chemical oxygen demand (COD) (88.57%), total phosphorus (TP) (79.93%), and total nitrogen (TN) (88.49%), along with significant reductions in fecal bacteria indicators (4.21 log for fecal coliforms and 3.90 log for fecal streptococci) and the pathogen Staphylococcus sp. (2.43 log). The principal component analysis confirms the effectiveness of the system in reducing the concentrations of NH4, COD, TP, PO4, fecal coliforms, fecal streptococci, and fecal staphylococci, thus supporting the reliability of the study. This work highlights the promising potential of the hybrid MSL technology for the treatment of domestic wastewater, especially in arid regions such as North Africa and the Middle East, to support efforts to protect the environment and facilitate the reuse of wastewater for landscape irrigation and agriculture.

Biological approaches and coagulation are frequently used to reduce the chemical oxygen demand (COD) for treatment of ceramic effluent water. The technology known as the moving bed biofilm reactor (MBBR) can accomplish this goal. Further, the process of emulsification-aided innovative MBBR using biosurfactants can be proposed for ceramic effluent treatment. In a step-by-step upgrading scheme, biosurfactants and a consortia of halophilic and halotolerant microbial culture was utilized for the treatment of the effluent water. Over the course of 21 days, a progressive decrease in COD of up to 95.79% was achieved. Over the next 48 h period, the biochemical oxygen demand (BOD) was reduced by 98.3%, while total suspended solids (TSS) decreased by 79.41%. With the use of this innovative MBBR technology, biofilm formation accelerated, lowering the COD, BOD, and TSS levels. This allows treated water to be used for further research on recycling it back into the ceramics sector and repurposing it for agricultural purposes. PRACTITIONER POINTS: Implementation of modified MBBR technology for the treatment of effluent water. Biosurfactants could reduce in the organic and inorganic loads. Increase in MLSS values with COD removal observed. The plant operations without the use of chemical coagulants was effective with biosurfactants. Biofilm formation on carriers was scraped and the presence of surfactin and rhamnolipid was confirmed.

To reduce pollution and carbon emissions, a quantitative evaluation of the carbon footprint of the wastewater treatment processes is crucial. However, micro carbon element flow analysis is rarely focused considering treatment efficiency of different technology. In this research, a comprehensive carbon footprint analysis is established under the micro carbon element flow analysis and macro carbon footprint analysis based on life cycle assessment (LCA). Three wastewater treatment processes (i.e., anaerobic anoxic oxic, A2O; cyclic activated sludge technology, CAST; modified cyclic activated sludge technology, M-CAST) for low carbon source urban wastewater are selected. The micro key element flow analysis illustrated that carbon source mainly flows to the assimilation function to promote microorganism growth. The carbon footprint analysis illustrated that M-CAST as the optimal wastewater treatment process had the lowest global warming potential (GWP). The key to reduce carbon emissions is to limit electricity consumption in wastewater treatment processes. Under the comprehensive carbon footprint analysis, M-CAST has the lowest environmental impact with low carbon emissions. The sensitivity analysis results revealed that biotreatment section variables considerably reduced the environmental impact on the LCA and the GWP, followed by the sludge disposal section. With this research, the optimization scheme can guide wastewater treatment plants to optimize relevant treatment sections and reduce pollution and carbon emissions.

Biosolid management is becoming one of the most crucial issues for wastewater treatment plant (WWTP) operators. The application of the Oxic Settling Anaerobic (OSA) process allows the minimisation of excess sludge production. This study compares conventional activated sludge (CAS) and OSA layouts in a full-scale WWTP (namely, Corleone - Italy). Extensive monitoring campaigns were conducted to assess treatment performances regarding carbon and nutrient removal, greenhouse gas (GHG) emissions, excess sludge production, and biomass activity (by means of respirometric analysis). Results showed that the effluent quality consistently met the Italian discharge limits. However, with the implementation of the OSA process, there was a decrease in ammonium removal efficiency, which could be attributed to reduced nitrifier activity related to reduced biomass production and extended anaerobic conditions affecting the nitrification process. On the other hand, the OSA configuration significantly increased phosphorus removal, indicating a high phosphorus content in the resulting waste sludge. A worsening of the sludge settling properties was observed with the OSA configuration likely due to decreased EPS concentrations. The sludge production in the OSA configuration decreased by 17.3 % compared to CAS. Nitrous-oxide measurements did not show a variation between CAS and OSA configurations, confirming that the OSA process can be a suitable solution for reducing WWTP\'s carbon footprint.

Constructed wetlands (CWs) are widely used to polish the effluent of wastewater treatment plants and micro-polluted river or lake water. However, the impact of large-scale applications of CWs on carbon emissions is unclear. In this study, the carbon footprints of two full-scale hybrid CWs were determined based on life cycle assessment (LCA). Results showed that the carbon emission of CW ranged from 0.10 to 0.14 kg CO2-eq/m3, and was significantly correlated with the influent chemical oxygen demand loads and electricity consumption. However, CW would approach carbon neutrality during the service period when taking plant carbon sequestration into consideration. Compared with other advanced wastewater treatment technologies, CWs showed significant low-carbon emission and cost-effective benefits. This study clarified the role of CWs in the carbon cycle and would provide guidance for the construction and management of CWs.

Dual upflow reactive filtration by a slowly moving sand bed with continuously renewed, hydrous ferric oxide-coated sand is used for removing polluting substances and for meeting the ultralow 0.05 mg/l total phosphorus discharge permit limits at a 1.2 million liters per day (0.32 million gallons per day) water resource recovery facility in Plummer, Idaho, in the United States. A life cycle assessment (LCA) of this reactive filtration installation was carried out to assess the environmental hotspots in the system and analyze alternative system configurations with a focus on CO2 equivalent (CO2 e) global warming potential, freshwater and marine eutrophication, and mineral resource scarcity. \"What if\" scenarios with alternative inputs for the energy, metal salts, and air compressor optimization show trade-offs between the impact categories. Key results that show a comparative reduction of global warming potential include the use of Fe versus Al metal salts, the use of renewable energy, and the energy efficiency benefit of optimizing process inputs, such as compressor air pressure, to match operational demand. The LCA shows a 2 × 10-2  kg CO2 e footprint per cubic meter of water, with 47% from housing concrete, and an overall freshwater eutrophication impact reduced by 99% versus no treatment. The use of renewable hydropower energy at this site isolates construction concrete as a target for lowering the CO2 e footprint. PRACTITIONER POINTS: The main LCA eco-impact hotspots in this dual reactive filtration tertiary treatment are construction concrete and the ferric sulfate used. Iron salts show smaller impact in global warming, freshwater eutrophication, and mineral resource scarcity than \"what if scenario\" aluminum salts. The energy mix for this site is predominantly hydropower; other energy mix \"what if\" scenarios show larger impacts. Operational energy efficiency and thermodynamic analysis show that fine tuning the air compressor helps reduce carbon footprint and energy use. LCA shows a favorable 2 x 10-2 kg CO2e/m3 water impact with 99% reduction of freshwater eutrophication potential versus no treatment.

Wastewater treatment facility location selection and network design issues have become attractive topics in the field of wastewater management due to increasing human population, resource scarcity, environmental concerns, and rise of necessity for sustainable solutions for future policy designs. Especially in areas where the demand for wastewater treatment increases dramatically over the years because of reasons such as high migration levels, rapid industrialization, and tourism activities, the problem turns out to be more critical and dynamic. The existing studies try to deal with the issue through mathematical modeling approaches based on optimization perspectives, which require significant computational effort. In this study, an alternative approach based on system dynamics (SD) method is proposed to examine the complex dynamic and nonlinear structure of wastewater treatment facility location selection and network design problems. The proposed SD simulation model is designed for a densely populated industrial and tourism spot, the city of Antalya, located on the Mediterranean coast of Turkey. The model is capable of determining where and when to build a new wastewater treatment facility as well as generating the generic wastewater network structure to be built for the five districts situated in the city center based on cost issues for 2015-2040 period. In addition, the impacts of demand level changes for wastewater treatment due to population variations are analyzed via several scenarios to help decision makers to develop sustainable and cost-efficient management policies. Although SD is a frequently utilized approach in the water/wastewater management arena, to the best of our knowledge, this study is the first attempt to examine the complex and dynamic nature of wastewater treatment facility location selection and network design problems through SD approach.

In recent years, the demand for clean water has been growing all over the world despite the different threats posed, including increasing pollution, increasing deforestation and climate change. Industrial activity is the second largest consumer of water, so highly industrialized regions are more susceptible to water stress. In this sense, reuse strategies have been progressively discussed and used around the world; however, in Brazil there is still place for many advances, whether due to lack of incentives, cultural issues in society, or poor regulation of the subject. The objective of this work was to carry out a diagnosis of raw water uptake by industries in one Hydrographic Region of the state of Rio de Janeiro and to propose a discussion on the adoption of water reuse practices for non-potable purposes from the use of treated effluents. A survey of the theoretical framework on the subject was carried out, as well as an analysis of sustainability indicators and reports of the companies, including the current licensing processes of large undertakings consuming water resources. With this study, it was possible to obtain the average cost of implementing a water reuse unit for an industry in the state of Rio de Janeiro-Brazil, which, despite still being expensive, has a strong tendency to use due to world water shortages. Finally, it was concluded that the state of Rio de Janeiro has a threat of water scarcity that could be aggravated in the coming years, if measures and investments in supply alternatives are not adopted (water reuse), and improvement in all stages of water management water resources.

Ball milling (BM) as a solvent-free technology has been widely used to tailor the biochar-based adsorbents with high porosity and well dispersion for enhancing their environmental applications. In this study, the ball-milled layered double hydroxides (LDHs) biochar composite (B-LDHs-BC) was successfully fabricated with BM method for Cd(II) adsorption and the BM effects on the LDHs-BC structure-performance relationships were investigated. The solid-state characterization demonstrated the LDHs were successfully exfoliated by BM on the B-LDHs-BC surface which was identified by the enlarged basal spacing and reduced crystallite size of the LDHs. Although the BET surface area of B-LDHs-BC (226 m2/g) was slightly lower than the ball-milled BC, the B-LDHs-BC had more O-containing functional groups and higher adsorption capacity (119 mg/g). The kinetics experiments indicated that the Cd(II) removal by B-LDHs-BC was through both the physical and chemical adsorption processes, and the liquid membrane diffusion was the rate-controlling step. The positive BM effects mainly induced more abundant acidic functional groups and active adsorption sites, and thus enhanced Cd(II) performance of B-LDHs-BC. This work demonstrated a facile solvent-free method for production of the exfoliated LDHs modified BC composite, and also well illustrated the BM effects which can extend their practical use in environment.

In arid regions such as Saudi Arabia, wastewater treatment (WWT) facilities (meeting promulgated standards) need to adapt their continuous performance improvement (CPI) for long-term sustainability. To achieve this, the facilities need to improve their performance to comply with more strict objectives for broader reuse applications of treated effluent. The present research proposes a CPI framework based on performance benchmarking process for the stepwise improvement of WWT facilities. A grey rational analysis water quality index (GWQI) based on exceedance probability was developed. For weights\' estimation of 11 physical, chemical, and biological water quality parameters, the entropy method effectively accommodated the changes in relative importance of the parameters with including additional future reuse applications. For existing effluent reuse scenarios of restricted and unrestricted irrigation, the GWQI values were found consistent with the modified version of the Canadian WQI (GWQI). The indices\' values (ranged between 0 and 100) greater than 80 showed the efficient operation of four WWT plants in the Qassim Region of Saudi Arabia. Two hypothetical CPI scenarios with future reuse applications (fish, livestock drinking, and recreation) showed an overall decline in the average (of four plants) values of the GWQI (97 to 78) and GWQI (85 to 60). GWQI predicted stricter results for the facilities with parameters\' concentrations exceeding the targets with larger margins and was found applicable for the CPI of WWT facilities in arid regions. For existing scenarios, the assessment results suggest the facilities to control and monitor the chlorination practice. For future targets, tertiary treatment needs to be enhanced for desired nutrients and total dissolved solids removal. The proposed CPI framework provides a platform to initiate the performance benchmarking process for WWT facilities at local or regional levels in Saudi Arabia and elsewhere.