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Standardization of biogas technology is immensely important for the promotion of the biogas industry worldwide. China has built a complete biogas standard system, which is divided into common, household biogas, biogas engineering, biogas digester for domestic sewage treatment, output utilization, and service system standards. The problems and potential barriers for biogas standardization in China are analyzed and come down to sluggish standard, overlapped standard, government-dominated standard, and lagging international standard. Accordingly, all potential biogas standards should be evaluated and placed under the same department. China Biogas Society and China Association of Rural Energy Industry play leading roles in developing enterprise or group/association biogas standards and ISO biogas standards. The bio-natural gas standard system and experimental standardization should be developed as well to replenish biogas standard system. A paradigm shift in biogas standardization should be from government-dominated to market-oriented model. The lessons learned for other developing countries includes expanding standardization to multi-aspects to realize full lifecycle control and management, building rapid responding mechanism of standardization to adopt industry transformation, integrating outdated standards into new versions, and establishing market-based standard system.

Graphical abstract, Highlights • 20 randomly real urine samples were collected and analyzed. • Totally 30 antibiotics in the fresh real urine were identified. • Representative antibiotic resistance bacteria and its gene were identified. • Changes of antibiotics, antibiotic resistance bacteria and gens of urine were monitored., Human urine is a source of fertilizer and, with proper management, it can be reused in agriculture. Determining the contamination issue of antibiotics in source-separated urine is important because the majority of antibiotics are excreted with urine. In this study, source-separated urine samples were randomly collected from a male toilet in a university building and analyzed in terms of 30 typical antibiotics (including 14 sulfonamides, 4 tetracyclines, and 12 fluoroquinolones) and tetracycline-resistant Escherichia coli, as well as its antibiotic-resistant genes to determine the contamination characteristics of antibiotic-related pollution in fresh and stored urine. Results showed that 18 out of 30 typical antibiotics were detected in fresh source-separated human urine. The dominant antibiotic was oxytetracycline with a frequency of 100%, followed by tetracycline, sparfloxacin, enrofloxacin, and ofloxacin, which demonstrated a detection frequency of 55%. Among the detected values, sulfonamides (2 antibiotics), tetracyclines (4 antibiotics), and fluoroquinolones (12 antibiotics) had a concentration range of 0.25–2.94, 0.94–41.2, and 0.06–163.16 ng/mL, respectively. Furthermore, tetracycline-resistant Escherichia coli, which was measured using plate count method, and its related gene, tet M, exhibited a maximum cell density of (200,000 ± 5000) CFU/100 mL and (2.73 ± 0.261) × 107 copies/mL, respectively. When the fresh urine was stored in an ambient environment for 30 days to simulate the real circumstances of urine management, a significant reduction in antibiotics and antibiotic-resistant bacteria was observed, while the change in antibiotic-resistant genes was insignificant. The results of this study suggest that risks associated with antibiotics and their antibiotic-resistant bacteria and genes are retained during collection and storage. Hence, these kinds of microcontaminants must be considered in further urine utilization.

The provision of sanitation services for fast-growing urban populations is one of the world's urgent challenges. Hutong neighborhoods in Beijing, capital of China, cannot be rebuilt due to the protection of historical heritage, while residents still need to keep the habit of defecating in public toilets. One hundred public toilets with non-sewered sanitation in the Hutong neighborhoods of Beijing were visited to investigate the actual operating status in response to the “toilet revolution” campaign. The fault tree approach was used to identify the barriers toward a decent and environment-friendly public toilet and evaluate potential risks from the malfunction of various components. Four subsystems are defined and elaborated to calculate the fault possibility. These subsystems are environment- and user-friendly, regarded as ancillary facilities, and used for fecal sludge (FS) management. Statistical analysis of targeted cases indicated that fault probabilities of environmental considerations, user-friendly considerations, ancillary facilities, FS management are calculated as 0.79, 0.96, 0.96, and 0, respectively. The subsystems were weighted using a Delphi method concept. Results showed that the well operation ratio of Beijing Hutong public toilets is only 32%, and the sanitation service value chain can be further optimized. This study also provides references for other countries, which are dedicated to promoting urban sanitation and public health., Highlights • Potential risks of public toilets were identified through Fault Tree Analysis. • A methodology in framing failures of public toilet subsystems is developed. • Delphi method was applied, validated, and found useful in sanitation research. • The barriers toward decent and environment-friendly public toilets are identified.

Anaerobic digestion is one of the most sustainable and promising technologies for the management of organic residues. China plays an important role in the world&rsquo, s biogas industry and has accumulated rich and valuable experience, both positive and negative. The country has established relatively complete laws, policies and a subsidy system, its world-renowned standard system guarantees the implementation of biogas projects. Its prefabricated biogas industry has been developed, and several biogas-linked agricultural models have been disseminated. Nonetheless, the subsidy system in China&rsquo, s biogas industry is inflexible and cannot lead to marketization, unlike that of its European counterpart. Moreover, the equipment and technology levels of China&rsquo, s biogas industry are still lagging and underdeveloped. Mono-digestion, rather than co-digestion, dominates the biogas industry. In addition, biogas upgrading technology is immature, and digestate lacks planning and management. China&rsquo, s government subsidy is reconsidered in this work, resulting in the recommendation that subsidy should be based on products (i.e., output-oriented) instead of only input subsidy for construction. The policy could focus on the revival of abandoned biogas plants as well.

Current experiences in pilot sanitation projects indicate that the spontaneous precipitation in urine diversion (UD) systems has been one of the main challenges for the implementation of urine source separation on large-scale. As a result of microbial ureolysis, an increased pH leads to the formation of inorganic precipitates, which increases the risk of pipe blockage. Although significant advancements have been made in controlling the spontaneous precipitation in UD systems, experimentation in pilot projects is not enough to provide the feasible and reliable support for technical selection to adapt quickly to changing boundary conditions, such as population size and density. Therefore, established techniques should be constantly reassessed and improved in a broader variety of experimental settings to ensure the wide applicability, economic and environmental benefits, and social acceptance. This work also clarified the importance of establishing standardized evaluation methods, which helps to integrate the knowledge gained from reported specific case studies and provide detailed information that can support the decision makers. On the other hand, the economic assessment indicated that maximizing the value of the urine-derived fertilizers can ensure a favorable rate of return, which is important to attract investors and promote the implementation of urine source separation. Meanwhile, current legislation and government support have provided the opportunities for large-scale implementation of urine source separation. The decision makers should be prepared well to deal with such a paradigm shift.

This note from the field shows a novel, hybrid concept of a constructed wetland for the first time in a water-stressed region in the coldest capital in the world, Ulaanbaatar, Mongolia. After selecting a suitable household compound, an ‘Ice-Block Unit’ was designed and constructed to assess its technical performance and capacity to reduce greywater-borne hazards during 2013 and 2014. This system was based on storing water during the winter freezing period as an ice block, and then starting treatment during the summer/non-freezing period. Results showed that the maximum removal rates of chemical oxygen demand (COD), NH 4 + , NO 2 − , total suspended solids (TSS), PO 4 − , and Escherichia coli were up to 100%, 99%, 97%, 97%, 87%, and 98%, respectively. The effluent met the neighbouring country, China's, municipal discharge standard of A grade effluent and could also be considered restricted and unrestricted irrigation water as reported in other studies. The system has proven potential from a technical point of view and can be scaled up to community or cluster levels. This would enable reduction of greywater-borne hazards in low, middle and high income countries with similar contexts.

Rural toilet retrofitting (RTR) is a complex, dynamic system that is affected by many factors and the positive/negative feedback relationships between subsystems and variables. Traditional technologies and management methods face challenges in fundamentally describing and solving problems in RTR. To bridge this gap, this study utilizes system dynamics and causal loop diagrams to explain such problems based on data collected from the stakeholders of the RTR in Jiaozhou from 2018 to 2019. Specifically, this study examines the RTR system from the perspectives of household users, wastewater treatment plants, local governments, grassroots promoters, operation and maintenance personnel, toilet supplier and construction teams, and fecal sludge end users. The factors and processes involved in RTR are identified, and the feedback and relationships among its major stakeholders are established. Results show that the motivation of farmers to engage in RTR is a key variable that affects their final decisions regarding retrofitting and maintaining toilet functions. Meanwhile, the important variables related to the feedback and relationships among the major stakeholders of RTR are mostly focused on policies, subsidies, technology, satisfaction, and cooperation. A scientific analysis method and the updated RTR plan for toilet revolution are then formulated to promote the implementation of RTR in developing countries., Highlights • Typical case of rural toilet retrofitting in China is selected and investigated. • System dynamics model for simulating rural toilet retrofitting is developed. • Causal loop diagrams for rural toilet retrofitting are presented and analyzed. • Experience of rural toilet retrofitting is shared for other developing countries.

China has promoted its biogas industry for a long time and begun to support bio-natural gas (BNG; also known as biogas upgrading or biogas-to-biomethane) projects for the first time in 2015 at the central government level. This study presented a comprehensive overview of the BNG industry in China, including its status quo, national strategic planning, upgrading technologies, investment cost, potential, and opportunities and challenges. A total of 65 BNG demonstration projects were approved by the central government between 2015 and 2017, and 197 projects are expected to have been built by 2020 as part of the 13th Five-Year Plan (2016–2020). BNG is an emerging industry, and its development provides several opportunities, including a huge natural gas demand, national policy incentives, integrated agriculture, and reduced carbon emissions. The challenges and barriers to such developments include the high upgrading cost, fluctuating natural gas prices, unsound market access mechanism for biomethane and biofertilizer, scarce competition-oriented feedstock resources, incomplete standard system and cross-sectorial management, imperfect policy and subsidy mechanism, and lagging technology and equipment. China can learn from other developed countries in four ways. First, the country must enhance the cost effectiveness of its subsidies. Then, China must highlight the operations of its BNG industry and evaluate its performance; prioritize digestate management in the planning stage; improve its project service level and reinforce research and development. The findings of this work provide a valuable reference for other developing countries that intend to address energy shortage issues and integrate waste management into their regional planning.

The anaerobic digestion technology has many advantages and is a sustainable way to produce energy, solve the crisis on energy shortage, and reduce waste stream and carbon footprint. In this field experiment, a mixture of food, fruits, and vegetable waste, dairy manure, and inoculum was anaerobically digested in a constructed water tank digester. This study was performed at ambient temperature under different organic loading rates (OLRs), which were increased every two weeks. Results showed that the optimum feedstock-to-inoculum ratio is 0.4, which resulted in highest specific biogas and methane yields (0.44 and 0.28 Nm3/kg VS, respectively). With the OLRs, the highest yield was observed at 1.4 kg VS/m3 average feeding. When the feedstock-to-inoculum ratio was increased from 0.4 to 0.8, the effect on biogas yield and the volatile solids decreased. Hence, the total cumulative biogas production was approximately 18.5 Nm3 per reactor volume. The pathogen concentration, which was determined in the feedstock and the effluent samples, revealed that the reduction efficiency was relatively low. On the basis of the performance of this field study, emphasizing household organic waste composed with other feed materials to produce bioenergy was feasible. Anaerobic co-digestion produces biogas, contributes to sustainable waste management, and reduces environmental pollution. This scientific study can play a fundamental role in implementing this technology at the household level for efficient biogas production in Bangladesh and worldwide.

There are limited studies that focus on greywater treatment and reuse options, particularly in nomadic societies with unique cultural and climatic conditions. Studies relating to household greywater treatment in nomadic-cultured societies are limited. This study aims to address this gap by examining a case with a high concentration of chemical components in the greywater (e.g. where chemical oxygen demand ranged between 35 and 70,032 mg/L). Specifically, an upgraded greenhouse greywater treatment unit (GH-GWTU) was designed and constructed during the summer of 2013 in Ulaanbaatar, Mongolia, in order to assess the technical feasibility, and up-scaling capability, of the system at the community level. Chemical and biological test results indicated that most parameters (e.g. PO 4 3 − , NO 2 − , NH 4 + ) had a high removal rate of up to 98%. Moreover, the greenhouse may extend the treatment period up to 8 months. This study has shown that GH-GWTU is a potential technology that can significantly reduce the chemicals and biological agents in greywater in Mongolian Ger contexts which may reduce the greywater-borne hazards and vulnerability in the area. It can be replicable both at the household and community scale according to resources available for system operation and maintenance.

One of the major challenges for deploying sustainable sanitation technologies and services around the world is financing. The present study applied both qualitative (key informant interviews) and quantitative (household survey) methods to explore sources of alternative financing in Ulaanbaatar, Mongolia, towards deploying sustainable sanitation technologies and services. Microfinance organizations, government subsidies and mining industries may represent potential sources of financing for the implementation of sustainable sanitation technologies and services in Mongolia. Moreover, building social capital among Ger residents and reinventing the idea of ‘corporate WASH responsibility’ could constitute new directions for the future.

This study examines a closed-loop sanitation system (CLSS) in the ger areas (informal peri-urban settlements) of Ulaanbaatar, Mongolia in order to evaluate system feasibility and to identify the future prospects of CLSS as an alternative to conventional sanitation and drainage options. Results show that the CLSS concept is well understood and accepted by users and that services are being scaled up. Over 50 per cent of respondents used CLSS technologies during both winter and summer, testifying to the potential for scaling up these technologies and services. Moreover, all users responded positively in their evaluation of the emptying services. Despite some problems and challenges, the system proved to be feasible, replicable and acceptable in the study area. It is recommended that the entire CLSS approach be tested through scientific validation to convince more communities, government and other stakeholders about scaling up the system beyond the study area for better health, environmental conservation and resource recovery.

The biogas project for domestic sewage treatment (BPDST) is considered a promising facility for wastewater management in rural areas of China. This paper explores previous experimental works, cost analysis, and BPDST structure and design based on Chinese literature. Opportunities for developing decentralized or neighborhood-based BPDSTs include fulfilling Millennium Development Goals (MDGs) and Sustainable Development Goals (SDGs), the water pollution situation and deficiency of wastewater treatment facilities, the advantages of BPDSTs compared with centralized sewage plant, government support and policy drive for rural wastewater treatment, and reuse demand for resources. Meanwhile, challenges faced are emphasized as follows: uncertain responsibility for BPDSTs under different governmental departments restricts BPDST development and should be specified; uncertain effluent quality due to low efficiency of nutrient removal requires aerobic post-treatment to some extent; rural environmental awareness is still low and should be heightened; more funds should be invested in R&D for improvement of technology innovation; more reuse and resource recovery elements should be considered during implementation; follow-up services are lacking and should be improved; and BPDST maintenance should be trained. This paper could provide valuable reference for other developing countries.