Robust planning of sanitation services in urban informal settlements: An analytical framework

Centralized or Onsite Testing? Examining the Costs of Water Quality Monitoring in Rural Africa

Rural water systems in Africa have room to improve water quality monitoring. However, the most cost-effective approach for microbial water testing remains uncertain. This study compared the cost per E. coli test (membrane filtration) of four approaches representing different levels of centralization: (i) one centralized laboratory serving all water systems, (ii) a mobile laboratory serving all systems, (iii) multiple semi-centralized laboratories serving clusters of systems, and (iv) decentralized analysis at each system. We employed Monte Carlo analyses to model the costs of these approaches in three real-world contexts in Ghana and Uganda and in hypothetical simulations capturing various conditions across rural Africa. Centralized testing was the lowest cost in two real-world settings and the widest variety of simulations, especially those with water systems close to a central laboratory (<36 km). Semi-centralized testing was the lowest cost in one real-world setting and in simulations with clustered water systems and intermediate sampling frequencies (1-2 monthly samples per system). The mobile lab was the lowest cost in the fewest simulations, requiring few systems and infrequent sampling. Decentralized testing was cost-effective for remote systems and frequent sampling, but only if sampling did not require a dedicated vehicle. Alternative low-cost testing methods could make decentralized testing more competitive.

Technologies for pollutant removal and resource recovery from blackwater: a review

Blackwater (BW), consisting of feces, urine, flushing water and toilet paper, makes up an important portion of domestic wastewater. The improper disposal of BW may lead to environmental pollution and disease transmission, threatening the sustainable development of the world. Rich in nutrients and organic matter, BW could be treated for resource recovery and reuse through various approaches. Aimed at providing guidance for the future development of BW treatment and resource recovery, this paper presented a literature review of BWs produced in different countries and types of toilets, including their physiochemical characteristics, and current treatment and resource recovery strategies. The degradation and utilization of carbon (C), nitrogen (N) and phosphorus (P) within BW are underlined. The performance of different systems was classified and summarized. Among all the treating systems, biological and ecological systems have been long and widely applied for BW treatment, showing their universality and operability in nutrients and energy recovery, but they are either slow or ineffective in removal of some refractory pollutants. Novel processes, especially advanced oxidation processes (AOPs), are becoming increasingly extensively studied in BW treatment because of their high efficiency, especially for the removal of micropollutants and pathogens. This review could serve as an instructive guidance for the design and optimization of BW treatment technologies, aiming to help in the fulfilment of sustainable human excreta management.

Anthropogenic pollution discharges, hotspot pollutants and targeted strategies for urban and rural areas in the context of population migration: Numerical modeling of the Minjiang River basin

Unprecedented urbanization-induced population migration in China severely affects the scale and geographic distribution of anthropogenic pollutant discharge. Understanding how pollutant discharge patterns respond to population migration can help guide future efforts to maintain water sustainability. Here, based on a new calculation framework with 18 dynamic parameters designed for anthropogenic discharges, we finely tracked and visualized the effects of population migration on the spatial and temporal changes in anthropogenic discharge from 1980 to 2019 in the Minjiang River basin. The results indicate that the increasing effect of population migration on anthropogenic discharges peaked in 2002 and started to contribute to pollutant reduction from 2010 onward. The direct impact of population migration only contributes to the shift of anthropogenic discharges from rural to urban areas, while the migration bonus is the key factor leading to the reduction in anthropogenic discharges. Population migration is highly beneficial for chemical oxygen demand (COD) reduction, which has contributed to a shift from COD to NH₄⁺-N and total phosphorus (TP) as hotspot pollutants in the whole basin (NH₄⁺-N in urban areas and TP in rural areas). Moreover, pollution reduction resulting from the demographic bonus phenomenon has remained limited only to urban areas. Since approximately 2010, the per capita amount and total amount of anthropogenic pollutant discharges in rural areas have exceeded those in urban areas; in particular, the per capita COD and TP discharges in rural areas reached four times those in urban areas. This suggests that future pollution control strategies should give more attention to rural areas and focus on the differentiation and targeting of urban and rural areas.

Navigating Multidimensional Social-Ecological System Trade-Offs across Sanitation Alternatives in an Urban Informal Settlement

Urban growth in low- and middle-income countries has intensified the need to expand sanitation infrastructure, especially in informal settlements. Sanitation approaches for these settings remain understudied, particularly regarding multidimensional social-ecological outcomes. Guided by a conceptual framework (developed in parallel with this study) re-envisioning sanitation as a human-derived resource system, here we characterize existing and alternative sanitation scenarios in an informal settlement in Kampala, Uganda. Combining two core research approaches (household survey analysis, process modeling), we elucidate factors associated with user satisfaction and evaluate each scenario's resource recovery potential, economic implications, and environmental impacts. We find that existing user satisfaction is associated with factors including cleaning frequency, sharing, and type of toilets, and we demonstrate that alternative sanitation systems may offer multidimensional improvements over existing latrines, drying beds, and lagoons. Transitioning to anaerobic treatment could recover energy while reducing overall net costs by 26-65% and greenhouse gas emissions by 38-59%. Alternatively, replacing pit latrines with container-based facilities greatly improves recovery potential in most cases (e.g., a 2- to 4-fold increase for nitrogen) and reduces emissions by 46-79%, although costs increase. Overall, this work illustrates how our conceptual framework can guide empirical research, offering insight into sanitation for informal settlements and more sustainable resource systems.

Re-Envisioning Sanitation As a Human-Derived Resource System

Sanitation remains a global challenge, both in terms of access to toilet facilities and resource intensity (e.g., energy consumption) of waste treatment. Overcoming barriers to universal sanitation coverage and sustainable resource management requires approaches that manage bodily excreta within coupled human and natural systems. In recent years, numerous analytical methods have been developed to understand cross-disciplinary constraints, opportunities, and trade-offs around sanitation and resource recovery. However, without a shared language or conceptual framework, efforts from individual disciplines or geographic contexts may remain isolated, preventing the accumulation of generalized knowledge. Here, we develop a version of the social-ecological systems framework modified for the specific characteristics of bodily excreta. This framework offers a shared vision for sanitation as a human-derived resource system, where people are part of the resource cycle. Through sanitation technologies and management strategies, resources including water, organics, and nutrients accumulate, transform, and impact human experiences and natural environments. Within the framework, we establish a multitiered lexicon of variables, characterized by breadth and depth, to support harmonized understanding and development of models and analytical approaches. This framework's refinement and use will guide interdisciplinary study around sanitation to identify guiding principles for sanitation that advance sustainable development at the nature-society interface.

Conventional Sewer Systems Are Too Time-Consuming, Costly and Inflexible to Meet the Challenges of the 21st Century

There is an urgent need for innovation in the sanitation sector because the conventional model (toilet-to-sewer-to-treatment) is too time-consuming and costly, and alternatives are lacking. We estimate the challenge ahead by developing scenarios for 60 of the fastest-growing urban conglomerates in the World. We find that the majority would need to build out their sewer systems at a rate that is ten to 50 times higher than the highest rate for any project in the World Bank’s database, which is unrealistic. We also carry out a case study of Lagos, Nigeria, which suggests that, in any given year, 14–37% of Lagos State’s budget would need to be invested to provide sanitation to the presently underserviced population while keeping up with population growth, which also is unrealistic. Our study provides clear evidence that the conventional model for sanitation is unworkable for rapidly growing urban areas. We conclude there is an urgent need to encourage and fund projects that promote innovations that can tackle the three core challenges: can be built sufficiently quickly, are flexible, and affordable. This is not likely to happen unless the future generation is systematically trained and educated to creatively support innovation in sustainable sanitation.

Advancing Sustainable Sanitation and Agriculture through Investments in Human-Derived Nutrient Systems

The sixth Sustainable Development Goal seeks to achieve universal sanitation, but a lack of progress due to inhibiting factors (e.g., limitations in financial resources, sociocultural conditions, household decision-making) demands innovative approaches to meet this ambitious goal. Resource recovery may generate income to offset sanitation costs while also enhancing agriculture through increased access to agricultural nutrients. The objective of this work was to determine if resource recovery sanitation can be a profitable business model in a specific context (Kampala, Uganda) and to explore the potential for this approach to translate to other Sub-Saharan African contexts. A techno-economic analysis was performed to evaluate the financial viability of two nutrient recovery systems and business models in urban communities in Kampala under two financing scenarios: (1) Startup relying on partial sanitation aid, and (2) Self-sustaining without philanthropic financing. Results show profitability can be achieved at a nutrient selling price at or below fertilizer market value in Uganda. Recoverable nutrients from the total population without at least basic sanitation services, in 10 Sub-Saharan African countries, are the same magnitude as nutrients distributed in subsidy programs (30-450% of distributed nutrients), indicating a potential to offset inorganic fertilizer consumption or increase nutrient availability. This research makes a case to support innovative sanitation strategies and the development and financial support of human-derived fertilizer markets in areas with poor fertilizer and sanitation access.

Priority Addressment Protocol: Understanding the Ability and Potential of Sanitation Systems to Address Priorities

Sanitation acceptance is unlikely if user priorities are not addressed. However, sanitation systems are commonly implemented, especially in resource-limited communities, without incorporating local context. Understanding sanitation systems' abilities to address different priorities will further inform technology selection processes. Therefore, a protocol was created to identify priorities and measure how well sanitation systems address them, based upon their importance to a community. This protocol was applied to 20 community-based sanitation systems in India. Overall, 52 sanitation and 40 community priorities were identified; most, along with their relative importance, were case-specific and not yet identified in literature. Existing sanitation systems poorly addressed priorities. Nonfunctional systems addressed the fewest, but, if use and maintenance were improved, they had the potential to address priorities almost as well as functional systems. Resource recovery systems addressed the most priorities, but there was usually minimal benefit to adding all three resources to an existing system; biogas and water had greater potential to address more priorities than compost. This priority addressment protocol can help identify the most appropriate technologies and strategies to improve technology development and success.

Toilet revolution in China

The wide-spread prevalence of unimproved sanitation technologies has been a major cause of concern for the environment and public health, and China is no exception to this. Towards the sanitation issue, toilet revolution has become a buzzword in China recently. This paper elaborates the backgrounds, connotations, and actions of the toilet revolution in China. The toilet revolution aims to create sanitation infrastructure and public services that work for everyone and that turn waste into value. Opportunities for implementing the toilet revolution include: fulfilling Millennium Development Goals and new Sustainable Development Goals; government support at all levels for popularizing sanitary toilet; environmental protection to alleviate wastewater pollution; resource recovery from human waste and disease prevention for health and wellbeing improvement. Meanwhile, the challenges faced are: insufficient funding and policy support, regional imbalance and lagging approval processes, weak sanitary awareness and low acceptance of new toilets, lack of R&D and service system. The toilet revolution requires a concerted effort from many governmental departments. It needs to address not only technology implementation, but also social acceptance, economic affordability, maintenance issues and, increasingly, gender considerations. Aligned with the ecological sanitation principles, it calls for understanding issues across the entire sanitation service chain. Public-private partnership is also recommended to absorb private capital to make up the lack of funds, as well as arouse the enthusiasm of the public.