Aug 2026· Water Practice & Technology· Vol 21, pp. 3804-3815· 0 citations· 25 references
Abstract
Zambia's water utilities import chlorine gas and high-test hypochlorite (HTH) for disinfection. The imports pose service reliability and governance risks, because utilities must maintain residual chlorination despite foreign-exchange shocks, long transport corridors, and periodic stockouts. This study evaluates whether on-site electrolytic chlorination (OSEC), producing sodium hypochlorite from salt and electricity, can provide a cost-effective substitution pathway and whether local salt resources support scale-up. Choma was selected because it combines two interconnected treatment plants (Munzuma and ZESCO), an 18 km trunk main to Kalundu Station, HTH use, and a network representative of small-to-medium utility systems in Zambia. The analysis combines 16 months of plant records, engineering sizing, a 15-year discounted cash-flow analysis (8% discount rate), sensitivity testing, and an assessment of chlorine gas, HTH, and OSEC-grade salt. Results show that OSEC is most viable when deployed at critical network nodes rather than widespread rollout: Kalundu-plus-ZESCO reduces annual disinfection cost by 49% compared with HTH use. Demand uncertainty and system sizing are the main risks. Substituting HTH at suitable plants creates demand for an OSEC-grade salt value chain, but use depends on impurity removal and quality assurance. The study contributes a transferable utility-industry framework for improving disinfectant reliability in import-exposed water sectors.
This study explored whether it's possible to recover valuable resources from five operational Decentralised Wastewater Treatment Systems (DEWATS) in Dar es Salaam, Tanzania, to help build a stronger urban sanitation economy. We gathered data on biogas, biosolids, treated effluent, and household tariff revenues through laboratory analyses and interviews between December 2025 and April 2026, then ran a 20-year cost-benefit analysis using three discount rates. Two sites, Kigamboni-Tungi (131% OPEX cost coverage) and Tuangoma (115%), are already paying for themselves through resource recovery. However, across all sites, there’s still a combined annual revenue gap of 5,025 USD. Our findings show that better management, rather than new technology, is the key to success: benefit-cost ratios improved by 44–109% under more optimistic scenarios. The biggest challenges were institutional, not technical. For example, formalizing biosolid sales, adding disinfection to the effluent at three sites, and starting household tariffs at Mlalakuwa could help each site cover its costs with minimal additional investment. We encourage the Ministry of Water and Sanitation to recognize DEWATS as productive infrastructure in national water sector funding. Our study offers the first verified, multi-site financial dataset linking effluent quality, resource-recovery revenues, and lifecycle cost-benefit analysis for DEWATS in sub-Saharan Africa, providing practical evidence to inform sanitation-economy policy in low-income urban areas. To improve DEWATS sustainability, we recommend formalizing biosolid and effluent sales and investing in low-cost disinfection upgrades to unlock higher-value resource recovery. Strengthening CBWSO management capacity and incentives will further support long-term financial viability and effective operation.
W. N. Mmuya, D. Mmasi, A. Mremi· Journal of Applied Sciences...· 0 citations
The management and disposal of drinking water treatment residuals (DWTR) cause high economic costs and negative impacts on the quality of the receiving environment. This study proposed a replicable framework for estimating DWTR production, evaluating the technical and economic implications, and assessing the potential application of DWTR granules across selected scenarios in Chile as a case study. A production of 24,500 metric tons (t) of DWTR per day was estimated for drinking water treatment plants located in the Metropolitan Region of Santiago, Chile, which collectively produce 23.6 m3s-1 of treated water. The techno-economic analysis estimated DWTR conditioning costs between 50 and 80 USDt-1, depending on the dewatering technology employed. DWTR granulation costs ranged from 90 to 140 USDt-1. Costs vary mainly due to heat treatment (calcination) and the use of raw materials (binder), which account for over 70% of operational costs. The application scenarios showed that systems based on DWTR granules could remove arsenic and copper at costs of 0.10-0.19 and 0.10 USDm-3 of treated water, respectively, and phosphorus at costs of 370-530 USDkg-1 of P removed. These costs were economically favorable and competitive compared to DWTR disposal in landfill and other sorbents and treatment technologies. The sensitivity analysis illustrated that a ±30% variation in the costs of natural gas (calcination) and binder (bentonite) modified the DWTR granulation cost by up to ±24%. The results indicated that applying DWTR granules for the removal of aqueous contaminants constitutes an economically competitive strategy for managing waste within the urban water cycle.
Carlos I González, A. Vega, María Molinos-Senante et al.· Journal of Environmental Man...· 0 citations
Existing industrial buildings represent a critical but under-addressed field for operational carbon emission reduction, as retrofit decisions are constrained by production continuity, limited investment capacity, and heterogeneous technical options. This study developed a decision support framework integrating the Decision-Making Trial and Evaluation Laboratory (DEMATEL) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) methods to evaluate and prioritize operational phase decarbonization retrofit schemes for existing industrial buildings. The framework was applied to the Thyssenkrupp S Plant in eastern China, where ten candidate schemes were identified through an energy audit, on-site investigation, and expert consultation. The results show that heating, ventilation, and air conditioning (HVAC) operational control and temperature set-point optimization ranked first, followed by lighting operational management and automatic control. These management-based measures offer strong near-term applicability because of their low investment, short payback periods, limited implementation disturbance, and immediate emission reduction benefits. Their sustained effectiveness, however, requires standardized procedures, staff education, energy monitoring, and appropriate automation. Rooftop photovoltaics provide the largest annual carbon reduction but have a lower short-term priority because of their high upfront investment. Expert-consistency testing and sensitivity analyses, including criterion weight perturbation, preference scenarios, and Monte Carlo simulation, support the robustness of the leading ranking pattern. The findings support staged retrofit planning that prioritizes durable management measures in the short term, equipment-level efficiency improvements in the medium term, and renewable energy deployment in the long term.
Daizhong Tang, Yuefeng Cao, Shikun Ma et al.· Buildings· 0 citations
Growing water scarcity calls for sustainable and decentralized strategies to reduce demand for freshwater resources. Greywater reuse is a promising option, though concerns about pathogens and organic micropollutants (OMPs) necessitate effective treatment. This study evaluates a full-scale system integrating a green wall with ozonation, installed on a residential building in Sant Quirze del Vallès (Barcelona, Spain), for greywater and rainwater treatment and reuse in toilet flushing. Over one year, the green wall achieved high removal of COD (84%), BOD5 (96%), TOC (87%), TSS (94%), and ammonium (>99%), with ozonation providing additional polishing and ensuring microbial safety (E. coli below the detection limit). Several OMPs, including caffeine, benzotriazole, and tramadol, were effectively removed by the green wall, while ozonation addressed more persistent compounds such as DEET or valsartan. The treated effluent consistently met Spanish quality standards for non-potable reuse. Social acceptance was assessed through resident surveys and stakeholder interviews. While participants acknowledged the environmental value of water reuse, acceptance was influenced by practical concerns (odour, noise or water colour) and trust in the managing entity. Findings highlight the need to complement strong technical performance with effective communication and reliable maintenance to foster long-term adoption of such nature-based and hybrid solutions.
Esther Mendoza, Èric Herrán-Morueco, Massimiliano Riva et al.· Journal of Environmental Man...· 0 citations
The maritime shipping industry faces increasing pressure to decarbonise, with alternative fuels emerging as key pathways to reduce greenhouse gas emissions. This study develops an operational expenditure -based multi-scenario framework to evaluate the techno-economic and environmental performance of alternative marine fuels for a 15,000 TEU containership operating on the Rotterdam–Singapore route. The analysis compares Heavy Fuel Oil (HFO), Liquefied Natural Gas (LNG), and ammonia across Suez Canal (SC) and Cape of Good Hope (COGH) routing options under normal market conditions and Red Sea crisis conditions, incorporating fuel costs, tank-to-wake CO2 emission costs, and SC transit tolls under alternative pricing and rebate schemes. The results demonstrate that the Red Sea crisis substantially increases total operating costs across all fuel pathways on the COGH route. Compared with normal market conditions, total operating costs increase by approximately 155% for HFO, 118% for LNG, and 58% for ammonia. While ammonia remains the highest-cost option in absolute terms, it exhibits the smallest relative cost escalation under crisis conditions, indicating greater resilience to fuel price and carbon cost shocks. LNG emerges as the most cost-competitive option across most scenarios, whereas HFO loses relative competitiveness due to its higher exposure to fuel and carbon costs. The diversion of vessels from the SC to the COGH increases voyage distance from 8288 to 11,755 nm, resulting in higher fuel consumption, emissions, and carbon costs. Consequently, CO2 emissions increase from 4114 to 5,481 tons on the SC route to 5797–7723 tons on the COGH route, highlighting the critical influence of route choice on both environmental and economic performance. The findings further suggest that emerging IMO carbon pricing measures are likely to strengthen the competitiveness of low- and zero-emission fuels, particularly under conditions of geopolitical disruption. Overall, the study provides a comparative benchmark for evaluating alternative fuel pathways and routing strategies, contributing to the understanding of the interactions between maritime decarbonization, route selection, and geopolitical risk in global container shipping.
S. H. Okasha· Journal of Shipping and Trad...· 0 citations
Landfill leachate circuits that operate without discharge, by recirculating aerated leachate onto the waste mass, are widespread in South-East Europe, yet their long-term behaviour is rarely documented with sample-level data. This study reports a six-year (2020–2025) seasonal monitoring campaign at a sanitary landfill in northern Serbia (alluvial aquifer of the Sava River, transboundary Danube basin) and re-examines it with a transparent multivariate protocol. Seventy-two leachate samples (collection well, aeration lagoon, sedimentation lagoon; n = 24 each, 30 parameters), 28 realised surface-water campaigns, and six years of groundwater summaries were evaluated by principal component analysis/factor analysis (PCA/FA, Varimax normalized), hierarchical cluster analysis, PERMANOVA, non-parametric paired tests and, for benchmarking, supervised machine learning. The pooled leachate model (n = 72; 21 variables; KMO = 0.700; Bartlett χ2 = 956, p < 0.001) retained four factors by parallel analysis, explaining 61.6% of total variance; after rotation the factors accounted for 27.7%, 14.3%, 10.4%, and 9.3%. Factor 1 grouped organic load with particle-reactive metals (COD, BOD5, Fe, Ni, Cr, As, Zn), Factor 2 a reduced sulfur–fluoride–BTEX signature, Factor 3 temperature-driven nitritation, and Factor 4 a nitrate–manganese redox contrast. Crucially, paired campaign-by-campaign comparison showed no removal of the dominant pollutants along the circuit. Median COD, BOD5 and NH4-N were not lower in the sedimentation lagoon than in the collection well, while pH rose from 8.08 to 8.75 (p < 0.001); only Cu, Pb, NO3-N, and NO2-N decreased significantly. The circuit therefore homogenises and concentrates dissolved load rather than removing it. Downstream surface water was significantly enriched in electrical conductivity (+110 µS/cm), total dissolved solids, NH4-N, and NO2-N relative to upstream (Wilcoxon, p < 0.05), and groundwater showed episodic conductivity up to 12,760 µS/cm and NH4-N up to 102 mg/L. Cytotoxicity (MTT) confirmed biological relevance, with MRC-5 viability falling to 37% after 24 h exposure to 50 vol.% groundwater (Pw3) versus 60% in A549 cells. A random-forest classifier separated circuit units far better than PCA-based discrimination (76.4% versus 54.2% cross-validated accuracy) and distinguished the 2020–2021 pandemic period from 2022–2025 with 94.2% accuracy, a period effect also confirmed by PERMANOVA (R2 = 7.2%, p < 0.001). The results indicate that closed-loop recirculation without an engineered discharge barrier transfers, rather than eliminates, contaminant load, and that after-care of such systems requires mass-balance monitoring and polishing treatment.
N. Grba, V. Mihajlović, Goran Benedeković et al.· Processes· 0 citations
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