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Cao X, Chen Y, Zheng H, Liao Y, Feng L, Feng J, Liu C, Ji F. Integration of steel slag and zeolite enhances simultaneous nitrification and autotrophic denitrification in ultra-low carbon/nitrogen ratio wastewater: Remodeling microbiota and iron metabolism. BIORESOURCE TECHNOLOGY 2025; 429:132504. [PMID: 40209910 DOI: 10.1016/j.biortech.2025.132504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2025] [Revised: 04/06/2025] [Accepted: 04/06/2025] [Indexed: 04/12/2025]
Abstract
Constructed wetlands (CWs) are widely used for nitrogen pollution control in rural aquatic environments, yet their nitrogen removal efficiency often remains suboptimal. This study firstly examines how zeolite robustly stimulates Fe-utilization of steelmaking waste (i.e., steel slag) to improve nitrification and autotrophic denitrification of low carbon-to-nitrogen (C/N) ratio wastewater (C/N ≈ 1). Steel slag, by providing alkalinity for nitrification, also serves as an electron donor for denitrification due to its low-valent iron content. As a result, the total nitrogen (TN) removal efficiency was increased by 153.5% compared to the control group. Zeolite reshaped the microbial consortia, enriching iron autotrophic denitrifying bacteria and aerobic denitrifying bacteria. More importantly, zeolite facilitated microbial iron utilization by enhancing transmembrane iron transport and intracellular iron oxidation to boost nitrification and autotrophic denitrification without additional aeration, external carbon sources, or pH regulation. Our work advances understanding the development of low carbon technologies for wastewater nitrogen removal.
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Affiliation(s)
- Xuekang Cao
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Yinguang Chen
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
| | - Hao Zheng
- College of Environment and Ecology, Chongqing University, Chongqing 400045, China
| | - Yong Liao
- College of Environment and Ecology, Chongqing University, Chongqing 400045, China; Dongfang Electric Machinery Co., Ltd., Deyang 618000, China
| | - Lihua Feng
- College of Environment and Ecology, Chongqing University, Chongqing 400045, China; Chengdu Engineering Consulting Co., Ltd., Chengdu 610072, China
| | - Jiacheng Feng
- Wuhu Ecological Environment Monitoring Centre, Wuhu 241004, China
| | - Chao Liu
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Fangying Ji
- College of Environment and Ecology, Chongqing University, Chongqing 400045, China.
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Tomoi H, Ingumba BB, Simiyu S, Otteng E, Osewe J, Majiwa H, Braun L, Cumming O, Moriyasu T. Barriers and enablers for group-based manual emptying services for onsite sanitation facilities in Nairobi, Kenya: a qualitative study. Int J Hyg Environ Health 2025; 267:114595. [PMID: 40381544 DOI: 10.1016/j.ijheh.2025.114595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2025] [Revised: 04/03/2025] [Accepted: 05/13/2025] [Indexed: 05/20/2025]
Abstract
Onsite sanitation, such as pit latrines, is essential to achieving universal access to safe sanitation, as outlined in Sustainable Development Goal target 6.2. However, manual emptying for pit latrines in low-income areas is often unhygienic, posing health and environmental risks. Enhancing the safety of these services increases costs, yet affordability for customers is essential. Thus, reducing service costs is a key priority. Group-based approach, where emptiers visit multiple toilets consecutively, has potential to improve both service efficiency and affordability. However, few studies have investigated its applicability to manual emptying. This paper aims to identify barriers and enablers for group-based manual emptying services in low-income neighbourhoods of Nairobi. We conducted 12 focus group discussions with landlords, tenants, and manual emptiers in the Korogocho informal settlement in Nairobi and interviewed 20 key informants from relevant sectors in Kenya. We identified five categories of barriers and enablers that affected general and group-based manual emptying: 1) funding, 2) expertise and equipment, 3) social and commercial habits, 4) physical conditions, and 5) regulatory systems. Of these, a norm that pits are not emptied until they get full, operating time constraints, fair and transparent pricing, and an organiser who can arrange group-based emptying from Category 3, and transport capacity from Category 4 specifically affected group-based manual emptying. Given that the barriers have a cascade structure, addressing some primary barriers such as capacity building and recognising manual emptiers' role in the sanitation policies could be effective ways to ensure safe and affordable emptying services.
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Affiliation(s)
- Hiroaki Tomoi
- London School of Hygiene & Tropical Medicine, Keppel Street, WC1E 7HT, London, United Kingdom; School of Tropical Medicine and Global Health, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, Japan.
| | | | - Sheillah Simiyu
- African Population & Health Research Center, APHRC Campus, Manga Cl, Nairobi, Kenya
| | - Evelyne Otteng
- African Population & Health Research Center, APHRC Campus, Manga Cl, Nairobi, Kenya
| | - James Osewe
- African Population & Health Research Center, APHRC Campus, Manga Cl, Nairobi, Kenya
| | | | - Laura Braun
- London School of Hygiene & Tropical Medicine, Keppel Street, WC1E 7HT, London, United Kingdom
| | - Oliver Cumming
- London School of Hygiene & Tropical Medicine, Keppel Street, WC1E 7HT, London, United Kingdom
| | - Taeko Moriyasu
- Nagasaki University Office for Global Relations, 1-14 Bunkyo-machi, Nagasaki, Japan
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Liu R, Ma Y, Zhang H, Han D, Hao X, Li S, Geng X. A review-based estimation of GHG emissions of China's wastewater management system. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2025; 380:124869. [PMID: 40073476 DOI: 10.1016/j.jenvman.2025.124869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2024] [Revised: 02/03/2025] [Accepted: 03/04/2025] [Indexed: 03/14/2025]
Abstract
Under China's "Dual Carbon Goal", the wastewater treatment system plays a crucial role in the country's efforts to reduce greenhouse gas (GHG) emissions. However, a lack of baseline emissions data poses challenges for decarbonization efforts. This study aims to profile and diagnose the GHG emissions of China's entire wastewater system and identify key contributing factors. Our findings show that China's wastewater system, including wastewater treatment plants (WWTPs) and septic tanks, is responsible for significant emissions, with baseline estimates at 108.26 ± 47.37 Mt CO2-eq/a. Septic tanks and WWTPs emerged as the major GHG hotspots, contributing the most to the total emissions. This study highlights the variability in emission results from previous literature, stressing the need for consistent accounting methods and scientific emission factors. Additionally, current on-site monitoring practices in China show gaps, which hinder the accurate determination of baseline emissions. To guide future emission reduction strategies, regulatory frameworks and improved monitoring practices are recommended for the wastewater sector in China.
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Affiliation(s)
- Ranbin Liu
- Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies, Beijing University of Civil Engineering & Architecture, Beijing, 100044, PR China; Beijing Energy Conservation & Sustainable Urban and Rural Development Provincial and Ministry Co-construction Collaboration Innovation Center, Beijing University of Civil Engineering & Architecture, Beijing, 100044, PR China.
| | - Yan Ma
- Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies, Beijing University of Civil Engineering & Architecture, Beijing, 100044, PR China
| | - Huanlun Zhang
- Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies, Beijing University of Civil Engineering & Architecture, Beijing, 100044, PR China
| | - Dingrong Han
- Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies, Beijing University of Civil Engineering & Architecture, Beijing, 100044, PR China
| | - Xiaodi Hao
- Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies, Beijing University of Civil Engineering & Architecture, Beijing, 100044, PR China; Beijing Energy Conservation & Sustainable Urban and Rural Development Provincial and Ministry Co-construction Collaboration Innovation Center, Beijing University of Civil Engineering & Architecture, Beijing, 100044, PR China.
| | - Shuang Li
- Beijing Capital Eco-environment Protection Group Co., Ltd., Beijing, 100052, PR China
| | - Xiao Geng
- Beijing Capital Eco-environment Protection Group Co., Ltd., Beijing, 100052, PR China
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Mills F, Foster T, Kome A, Munankami R, Halcrow G, Ndungu A, Evans B, Willetts J. Indicators to complement global monitoring of safely managed on-site sanitation to understand health risks. NPJ CLEAN WATER 2024; 7:58. [PMID: 38979059 PMCID: PMC11227438 DOI: 10.1038/s41545-024-00353-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 06/24/2024] [Indexed: 07/10/2024]
Abstract
Halfway through the Sustainable Development Goal (SDG) period, there has been little research on the criteria for monitoring safely managed sanitation under SDG target 6.2. For reporting against SDGs, global indicators are necessarily limited and exclude many safety aspects from a public health perspective. Primary survey data from 31,784 households in seven countries in Asia and Africa were analysed, comparing estimates of safely managed on-site sanitation based on global indicators with five complementary indicators of safety: animal access to excreta, groundwater contamination, overdue emptying, entering containments to empty and inadequate protection during emptying. Application of additional criteria reduced the population with safely managed sanitation by 0.4-35% for specific indicators, with the largest impact due to the risk of groundwater contamination, animal access, and containments overdue for emptying. Combining these indicators across the service chain, excluding transport and treatment, found almost three-quarters of on-site systems currently assessed as safely managed with global indicators were considered unsafe based on complementary indicators. A more comprehensive assessment of safety of on-site sanitation can be achieved through these indicators, which could be integrated into national monitoring systems and used to inform sanitation investments that address local health-related risks.
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Affiliation(s)
- Freya Mills
- Institute for Sustainable Futures, University of Technology Sydney, Ultimo, NSW Australia
| | - Tim Foster
- Institute for Sustainable Futures, University of Technology Sydney, Ultimo, NSW Australia
| | - Antoinette Kome
- SNV Netherlands Development Organisation, The Hague, The Netherlands
| | - Rajeev Munankami
- SNV Netherlands Development Organisation, The Hague, The Netherlands
| | - Gabrielle Halcrow
- SNV Netherlands Development Organisation, The Hague, The Netherlands
| | - Antony Ndungu
- SNV Netherlands Development Organisation, The Hague, The Netherlands
| | - Barbara Evans
- School of Civil Engineering, University of Leeds, Leeds, UK
| | - Juliet Willetts
- Institute for Sustainable Futures, University of Technology Sydney, Ultimo, NSW Australia
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Manga M, Muoghalu CC. Greenhouse gas emissions from on-site sanitation systems: A systematic review and meta-analysis of emission rates, formation pathways and influencing factors. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 357:120736. [PMID: 38574706 DOI: 10.1016/j.jenvman.2024.120736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 03/18/2024] [Accepted: 03/19/2024] [Indexed: 04/06/2024]
Abstract
Onsite sanitation systems (OSS) are significant sources of greenhouse gases (GHG) including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). While a handful of studies have been conducted on GHG emissions from OSS, systematic evaluation of literature on this subject is limited. Our systematic review and meta-analysis provides state-of-the- art information on GHG emissions from OSS and identifies novel areas for investigation. The paper analyzes GHG emission rates from different OSS, the influence of various design, operational, and environmental factors on emission rates and proffers mitigation measures. Following the Preferred Reporting Items for Systematic reviews and Meta-analysis (PRISMA) guidelines, we identified 16 articles which quantified GHG emissions from OSS. Septic tanks emit substantial amounts of CO2 and CH4 ranging from 1.74 to 398.30 g CO2/cap/day and 0.06-110.13 g CH4/cap/day, respectively, but have low N2O emissions (0.01-0.06 g N₂O/cap/day). CH4 emissions from pit latrines range from 0.77 to 20.30 g CH4/cap/day N2O emissions range from 0.76 to 1.20 gN2O/cap/day. We observed statistically significant correlations (p < 0.05) between temperature, biochemical oxygen demand, chemical oxygen demand, dissolved oxygen, storage period, and GHG emissions from OSS. However, no significant correlation (p > 0.05) was observed between soil volumetric water content and CO2 emissions. CH4 emissions (expressed as CO2 equivalents) from OSS estimated following Intergovernmental Panel for Climate Change (IPCC) guidelines were found to be seven times lower (90.99 g CO2e/cap/day) than in-situ field emission measurements (704.7 g CO2e/cap/day), implying that relying solely on IPCC guidelines may lead to underestimation of GHG emission from OSS. Our findings underscore the importance of considering local contexts and environmental factors when estimating GHG emissions from OSS. Plausible mitigation measures for GHG emissions from OSS include converting waste to biogas in anaerobic systems (e.g. biogas), applying biochar, and implementing mitigation policies that equally address inequalities in sanitation service access. Future research on GHG from OSS should focus on in-situ measurements of GHGs from pit latrines and other common OSS in developing countries, understanding the fate and transport of dissolved organics like CH4 in OSS effluents and impacts of microbial communities in OSS on GHG emissions. Addressing these gaps will enable more holistic and effective management of GHG emissions from OSS.
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Affiliation(s)
- Musa Manga
- Department of Environmental Sciences and Engineering, The Gillings School of Global Public Health, University of North Carolina at Chapel Hill, 0030 Michael Hooker Research Center, 135 Dauer Drive, Campus Box # 7431, NC 27599, Chapel Hill, NC, USA; Department of Construction Economics and Management, College of Engineering, Design, Art and Technology (CEDAT), Makerere University, P.O. Box 7062, Kampala, Uganda.
| | - Chimdi C Muoghalu
- Department of Environmental Sciences and Engineering, The Gillings School of Global Public Health, University of North Carolina at Chapel Hill, 0030 Michael Hooker Research Center, 135 Dauer Drive, Campus Box # 7431, NC 27599, Chapel Hill, NC, USA
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