Urine-diverting Dry Toilets Research Articles

An environmental evaluation of urine-diverting dry toilets in Hiloweyn Camp, Dollo Ado, Ethiopia

Safe and hygienic management of human waste is essential in humanitarian settings. Urine-diverting dry toilets (UDDTs) can enable this management in some humanitarian emergency settings. A seeded, longitudinal environmental study was conducted in Hiloweyn refugee camp, Dollo Ado, Ethiopia, to measure Escherichia coli and Ascaris suum ova inactivation within closed UDDT vaults and to document environmental conditions (temperature, moisture content, and pH) that could influence inactivation. Hiloweyn camp represented an optimal location for a desiccation-based sanitation technology such as the UDDT. E. coli and Ascaris ova inactivation was observed in UDDTs under warm, dry, alkaline conditions at 6, 9, and 12 months of storage; UDDTs with samples containing <1000 E. coli/g total solids increased from 30 % to 95 % over 12 months, and a >2.8-log10 reduction in Ascaris ova viability was observed after 6 months. Additional laboratory-based studies were conducted to provide insights into the field study findings and study the impact of hydrated lime on E. coli and Ascaris ova inactivation. Results suggest that adding hydrated lime to elevate pH > 12 may increase inactivation and decrease storage time. Overall, UDDTs could contribute to the safe and hygienic management of human waste in comparable warm and dry humanitarian settings.

Understanding the adoption of urine-diverting dry toilets (UDDTs) in low- and lower-middle-income countries using the Diffusion of Innovation framework

Abstract Understanding barriers and facilitators to the adoption of sanitation technologies is crucial to the diffusion of these innovations. Urine-diverting dry toilets (UDDTs) have been implemented throughout regions that are lacking improved sanitation. This review applied the Diffusion of Innovation theory to 18 research articles that collected end-user/potential end-user feedback on UDDT pilot projects in low- and lower-middle-income countries to better understand barriers and facilitators to adoption. Results show the main barriers to adoption were beliefs incompatible with UDDT by-product reuse, a lack of supporting infrastructure, high capital costs, and ineffective promotional communication strategies. The benefits promoted by the diffusion agency were often misaligned with the desires and interests of the potential adopters. Ensuring supporting infrastructure was in place and tailoring the promotional communications to the adopters’ perspectives facilitated UDDT adoption. The main facilitator was the perceived relative advantages of the UDDT over existing sanitation options, including fertilizer production. This indicates that safe treatment and reuse processes need to be implemented. Urine diversion was rarely mentioned as a barrier. These findings can help communities and organizations working to increase sanitation technology adoption in low-income, rural areas by better understanding common barriers and facilitators to adoption.

Financial Viability and Environmental Sustainability of Fecal Sludge Treatment with Pyrolysis Omni Processors.

Omni Processors (OPs) are community-scale systems for non-sewered fecal sludge treatment. These systems have demonstrated their capacity to treat excreta from tens of thousands of people using thermal treatment processes (e.g., pyrolysis), but their relative sustainability is unclear. In this study, QSDsan (an open-source Python package) was used to characterize the financial viability and environmental implications of fecal sludge treatment via pyrolysis-based OP technology treating mixed and source-separated human excreta and to elucidate the key drivers of system sustainability. Overall, the daily per capita cost for the treatment of mixed excreta (pit latrines) via the OP was estimated to be 0.05 [0.03–0.08] USD·cap–1·d–1, while the treatment of source-separated excreta (from urine-diverting dry toilets) was estimated to have a per capita cost of 0.09 [0.08–0.14] USD·cap–1·d–1. Operation and maintenance of the OP is a critical driver of total per capita cost, whereas the contribution from capital cost of the OP is much lower because it is distributed over a relatively large number of users (i.e., 12,000 people) for the system lifetime (i.e., 20 yr). The total emissions from the source-separated scenario were estimated to be 11 [8.3–23] kg CO2 eq·cap–1·yr–1, compared to 49 [28–77] kg CO2 eq·cap–1·yr–1 for mixed excreta. Both scenarios fall below the estimates of greenhouse gas (GHG) emissions for anaerobic treatment of fecal sludge collected from pit latrines. Source-separation also creates opportunities for resource recovery to offset costs through nutrient recovery and carbon sequestration with biochar production. For example, when carbon is valued at 150 USD·Mg–1 of CO2, the per capita cost of sanitation can be further reduced by 44 and 40% for the source-separated and mixed excreta scenarios, respectively. Overall, our results demonstrate that pyrolysis-based OP technology can provide low-cost, low-GHG fecal sludge treatment while reducing global sanitation gaps.

Improving management of manually emptied pit latrine waste in Nairobi’s urban informal settlements

Sanergy has offered reliable, non-sewered sanitation services in Nairobi, Kenya through the implementation of container-based, urine-diverting dry toilets. However, there remains a large volume of untreated faecal waste in urban informal settlements due to poorly managed pit latrines. With limited space in the settlements to bury old pits and dig new ones, management of faecal sludge requires manual pit emptying and safe discharge. Sanergy piloted the Mtaa Fresh project in the settlement of Mukuru Kwa Njenga, establishing a waste transfer station where manual pit emptiers could safely and reliably dispose of pit latrine contents. The most important factors in the successful implementation of this station were, first, the relationship established between Sanergy and the pit emptiers and, second, Sanergy’s commitment to iterating as new insights emerged. The relationship with the emptiers impacted the location, design, and adoption of the site, and aided in the formalization of a pit emptiers’ community-based organization. The commitment to iterating enabled Sanergy to respond to learnings gained from the emptiers. Additional factors that ensured the success of Mtaa Fresh included the implementation of full-time staff, security when the site is closed, support from local authorities, and an expansion to improve management of faecal sludge and trash. Improvements trialled during the expansion aim to minimize operation and maintenance costs, but sustainability will still rely on government support and external funding.

Opportunities for circular bionutrient economy in Kenya: Sanitation and waste stream characterization

AbstractThe majority of people in low‐ and middle‐income countries, such as Kenya, lack effective sanitation and waste management systems. Circular bionutrient economy (CBE) is emerging as a framework to safely reuse organic wastes in agriculture. This study aimed to characterize waste and sanitation systems in Kisumu City, Kenya, with a view to exploring opportunities for CBE in the Lake Victoria basin. Sanitation was characterized through a case study approach in a populous informal settlement, and waste was quantified in two markets in the city. The main toilet facility was pit latrine, although there were also some urine‐diverting dry toilets (UDDTs). One toilet served about 36 people. Over a 1‐mo period, the UDDTs yielded approximately 64,400 L of urine, whereas about 67,500 L of fecal sludge was emptied from the pit latrines, out of which only about 33,000 L (48.9%) was properly disposed of. About 3 t of waste was generated daily from the markets, 95% of which was organic, and was disposed of at an open dumpsite. Organic waste, including human excreta, contains large amounts of organic matter and plant nutrients, and can be processed for agricultural nutrient cycles. Additionally, black soldierly larvae can effectively convert organic waste into nutrient‐rich fertilizer and high protein biomass for animal feeds. These results suggest an opportunity for a CBE system in the region for sustainable organic waste management and urban sanitation, and with opportunity to improve livelihoods and equity.

Can local nutrient-circularity and erosion control increase yields of resource-constraint smallholder farmers? A case study in Kenya and Uganda

As many regions in sub-Saharan Africa, the border region of Kenya (KE) and Uganda (UG) has faced a declining soil fertility for decades, resulting from soil erosion, intensely managed agricultural soils due to population pressure and small inputs of mineral and organic fertilizers. With limited financial means, farmers need measures and/or technologies that effectively reduce nutrient losses or increase inputs at a low cost. In this study, four such measures are in focus, namely erosion reduction practices, vermicomposting of animal manure, collection of human urine in jerry cans and, collection of human excreta in urine-diverting dry toilets. Current soil nutrient balances in five districts in the Sio-Malaba-Malakisi River Basin and the potential of these measures to reduce the soil nutrient deficit are studied using the method of material flow analysis and the software STAN. Furthermore, crop-nutrient-response functions are used to determine their potential impact on maize harvests. Overall, results reveal that there exists a non-negligible and exploitable potential of local resources to reduce the soil nutrient deficit, improve harvests and in turn food security of the smallholder farmers in the region. Soil nutrient deficits could be reduced by 20–30%, 23–42% and 9–15% for nitrogen (N), phosphorus (P) and potassium (K), respectively. Subsequently, maize harvests could be increased by 8–40%, depending on the applied technology and area. This research provides useful insights for agricultural extension workers, politicians and researchers alike, highlighting that simple and easily available technologies can harness similar amounts of nutrients as more complex and expensive ones if all specific technology-constraints are adequately incorporated in the analyses.

Effect of fecal matter co-digestion with kitchen waste on Hermetia illucens’ larval weight and protein content

Abstract Sustainable treatment of fecal matter is a long-standing challenge in sanitation, particularly in developing countries. Although recent developments have seen the evolution of innovative onsite sanitation technologies, the treatment of fecal waste collected still remains a daunting task. This study evaluated the effect of formulated feedstock: fecal matter from urine-diverting dry toilets and kitchen waste (1:0, 1:1, 2:1, 4:1, and 0:1) on waste weight reduction, Hermetia illucens’ larval weight gain, and crude protein content during co-digestion. Samples were collected after every 2 days for larval weight determination and protein content analysis using the Kjeldahl method of nitrogen determination. The waste reduction index (WRI) was determined after 50% pupation. The larvae grew on all substrates yielding 32.97–38.6% dry matter (DM) protein content and larval weight ranging from 1.12 to 1.70 g per five larvae. Results indicate that a 1:1 co-digestion ratio resulted in a high WRI (3.61), DM crude protein content (38.6%), and larval weight (1.70 g per five larvae). This study used the circular economy-based approach which provides a win–win situation to sanitation provision and environmental management while realizing products with potential for livelihood improvement.

Improving management of manually emptied pit latrine waste in Nairobi’s urban informal settlements

Sanergy has offered reliable, non-sewered sanitation services in Nairobi, Kenya through the implementation of container-based, urine-diverting dry toilets. However, there remains a large volume of untreated faecal waste in urban informal settlements due to poorly managed pit latrines. With limited space in the settlements to bury old pits and dig new ones, management of faecal sludge requires manual pit emptying and safe discharge. Sanergy piloted the Mtaa Fresh project in the settlement of Mukuru Kwa Njenga, establishing a waste transfer station where manual pit emptiers could safely and reliably dispose of pit latrine contents. The most important factors in the successful implementation of this station were, first, the relationship established between Sanergy and the pit emptiers and, second, Sanergy’s commitment to iterating as new insights emerged. The relationship with the emptiers impacted the location, design, and adoption of the site, and aided in the formalization of a pit emptiers’ community-based organization. The commitment to iterating enabled Sanergy to respond to learnings gained from the emptiers. Additional factors that ensured the success of Mtaa Fresh included the implementation of full-time staff, security when the site is closed, support from local authorities, and an expansion to improve management of faecal sludge and trash. Improvements trialled during the expansion aim to minimize operation and maintenance costs, but sustainability will still rely on government support and external funding.

Beyond technology: a program for promoting urine-diverting dry toilets in rural areas to support sustainability

This work proposes a UDDT promotional program with the aim of promoting urine-diverting dry toilets in rural areas.

Power, danger, and secrecy-A socio-cultural examination of menstrual waste management in urban Malawi.

Menstrual blood is not just a physical substance; it is laden with symbolism and often powerfully stigmatised. It is important to understand local perceptions and attitudes towards menstrual blood, as well as the preferred practices of menstruating women, in order to design appropriate sanitation and solid waste systems to support menstruation. Failure to take account of socio-cultural factors can jeopardise the effectiveness of such infrastructure. This study, conducted in Blantyre, Malawi, is a qualitative socio-cultural examination of how women manage and view menstruation. Thirty nine interviews, conducted with individuals and with small groups of friends, were carried out with thirty one women using pit latrines, flush toilets, and urine-diverting dry toilets in early 2019. Menstruation in Blantyre was found to be shrouded in secrecy because it was viewed as ‘dirty’, and therefore remained concealed. There was widespread anxiety about menstrual blood being used in ufiti (witchcraft), which affected how women used and disposed of their menstrual absorbents. At the same time, menstrual blood was also viewed as a powerful healing substance with uses in traditional medicine. The type of infrastructure required by women to support their menstruation depended on the type of menstrual absorbent used. Those using reusable cloth generally preferred a private bathroom with discreet drainage, whilst those using disposable pads needed a discreet and convenient disposal system. Increased preference for disposable pads over reusable cloth (particularly for younger women in education or employment) suggested that menstrual waste profiles of urban areas may be changing. Understanding these changing needs will be crucial for planning effective, sustainable waste disposal and sanitation infrastructure.

Isothermal drying characteristics and kinetics of human faecal sludges

Background: Drying is an important step for the thermochemical conversion of solid fuels, but it is energy-intensive for treating highly moist materials. Methods: To inform the thermal treatment of faecal sludge (FS), this study investigated the drying characteristics and kinetics of various faecal wastes using thermogravimetric analysis and isothermal heating conditions. Results: The findings show that FS from anaerobic baffled reactor (ABR) and ventilated improved pit (VIP) latrines exhibit similar drying characteristics, with maximum drying rates at 0.04 mg/min during a constant rate period that is followed by a distinct falling rate period. On the contrary, fresh human faeces (HF) and FS from urine-diverting dry toilets (UDDT) exhibited a falling rate period regime with no prior or intermittent constant rate periods. The absence of constant rate period in these samples suggested limited amounts of unbound water that can be removed by dewatering and vice versa for VIP and ABR faecal sludges. The activation energies and effective moisture diffusivity for the sludges varied from 20 to 30 kJ/mol and 3∙10-7 to 1∙10-5 m2/s at 55°C and sludge thickness of 3mm. The Page model was consistent in modelling the different sludges across all temperatures. Conclusions: These results presented in this study can inform the design and development of innovative drying methods for FS treatment.

Return to learn: recommendations from revisited rural ecosan projects in Burkina Faso

Burkina Faso has extensive experience with urine-diverting dry toilets (UDDTs) and the reuse of human excreta in agriculture in line with the ecological sanitation (ecosan) principles of containment, treatment, and reuse. Around 30 such ecosan projects have been implemented over the past 15 years, including installation of approximately 13,500 household UDDTs, accompanied by awareness-building and training on toilet use, emptying, and reuse. Recently, efforts have been made to revisit former and current project sites in the spirit of ‘return to learn’. We identified four such learning initiatives (studies/events), from which we draw recommendations to improve the sustainability of future implementation of ecosan in Burkina Faso and similar contexts. Key recommendations include increased attention to different user needs, handwashing and training on emptying/reuse as well as research and innovation on toilet design, urine collection/handling, menstrual management, and cost reduction/financing. Burkina Faso has set up the ambitious goal of 100 per cent toilet coverage and optimal reuse in the national sanitation programme by 2030, with UDDTs projected to make up 15 per cent of the 2 million toilets needed in rural areas. It is therefore timely to take stock and learn from past interventions. In addition, to enable resource recovery and reuse at scale, it will be important to develop a supportive policy and legal framework with collaboration between the WASH, agriculture, health, and environmental sectors.

Field-Scale Co-fermentation of Solid Waste From Urine-Diverting Dry Toilets (UDDT-SW) and Banana Waste to Produce Undissociated Carboxylic Acids to Inactivate Ascaris Eggs

Innovative, low-cost methods for inactivating pathogens in human fecal material (HFM) are needed, particularly in expanding urban areas where conventional sewer systems and centralized wastewater treatment plants are not feasible. To address this challenge, we have developed a bioprocess that utilizes open cultures of anaerobic bacteria (i.e., microbiomes) to produce carboxylic acids using HFM as substrate. When the pH is sufficiently low, the carboxylic acids exist in the undissociated form and inactivate pathogens. Here, we used real sanitation waste collected from container-based, urine-diverting dry toilets (UDDT-SW) in Nairobi, Kenya to conduct lab-scale and field-scale trials. Through these trials, we investigated operating conditions required to use carboxylic acid fermentation in sanitation waste treatment processes. We tested three different inoculum treatments and determined that the microbiome in UDDT-SW is well suited to produce carboxylic acids without the need for an external inoculum. We also tested co-fermentation of UDDT-SW with carbohydrate-rich food waste as a means of reducing the pH. We found that when food waste was incorporated in a way that maintained the pH between 4.8 and 5.2, then the food waste was quickly converted to carboxylic acids, and the low pH created high concentrations of undissociated carboxylic acids. The resulting concentrations of undissociated carboxylic acids resulted in Ascaris inactivation within 15 days. However, we found that a temperature ≥30°C is required for carboxylic acid production to occur.

Challenges of Governing Off-Grid “Productive” Sanitation in Peri-Urban Areas: Comparison of Case Studies in Bolivia and South Africa

Globally, peri-urban areas are experiencing rapid urbanization. Conventional infrastructure development is generally slow to catch up and the lack of basic sanitation in peri-urban areas is a constantly growing—and often overlooked—problem. There are examples where these challenges have been addressed by off-grid “productive” sanitation systems that provide opportunities for recovery and reuse of valuable waste stream resources. However, governing such systems and ensuring effective municipal policies can be challenging since the socio-economic contexts in many peri-urban areas are transforming rapidly. A comparison of two initiatives in Bolivia and South Africa offers valuable insights for introducing functional off-grid “productive” sanitation systems relying on urine-diverting dry toilets (UDDTs) in peri-urban settlements. Findings suggest that acceptance of the UDDTs by households largely rely on consistent awareness raising and capacity building, in addition to adaptation to the local needs and creating a sense of ownership over the toilet system. Changing perceptions of what constitutes an aspirational toilet, and developing services for waste management collection, seem to be crucial components for ensuring long-term use and functionality of the UDDTs. Investments and further innovations for upscaling of resource recovery systems are needed to make these systems cost-effective and logistically viable. To attract these additional investments, it will be crucial to assess the societal economic benefits of off-grid “productive” sanitation compared to centralized wastewater systems. The comparison also highlights that off-grid sanitation requires a clear division and coordination of roles and responsibilities among different authorities, in order to transcend political difficulties that emerge where these boundaries overlap. Thus, integrating clear boundaries into urban planning policies, and including informal processes in communities, play an important role in improving governance of basic services in peri-urban areas.

Urea stabilisation and concentration for urine-diverting dry toilets: Urine dehydration in ash

Human excreta contain the same nitrogen, phosphorus and potassium (N-P-K) as the fertilisers used to produce the food consumed. However, human excreta are considered unwanted waste throughout the world, creating humanitarian and environmental problems. In order to replace the nutrients removed from fields during crop harvesting, more fertilisers are manufactured, in processes contributing to environmental changes at global level. The limitation of human urine as a fertiliser is its low nutrient concentration compared with commercial fertilisers. This study developed a technique to increase the N concentration (from 0.6% to >6%) through urine dehydration to produce a dry fertiliser of monetary value and avoid the need for liquid disposal from the toilet. The technique is intended for a container-based sanitation system that collects, contains, treats and reduces the volume of urine within the container. In tests, fresh human urine was added at various intervals to wood ash at 35°C and 65°C, to alkalise and thus inhibit the enzyme urease from catalysing hydrolysis of urea to ammonia. Mass balance calculations demonstrated a 95% reduction during dehydration, while preserving up to 90% of the N. Such a system would greatly simplify the logistics and costs of storage, transportation and application of urine as a fertiliser. The truly innovative feature is the final product: a dry powder with 7.8% N, 2.5% P and 10.9% K by weight, i.e. equivalent to commercial fertiliser.

Microwave treatment of faecal sludge from intensively used toilets in the slums of Nairobi, Kenya

Toilet facilities in highly dense areas such as the slum and emergency settlements fill up rapidly; thus, requiring frequent emptying. Consequently, big quantities of fresh faecal sludge (FS) containing large amounts of pathogens are generated. Fast and efficient FS treatment technologies are therefore required for safe treatment and disposal of the FS in such conditions. This study explores the applicability of a microwave (MW) technology for the treatment of fresh FS obtained from urine-diverting dry toilets placed in slum settlements in Nairobi, Kenya. Two sample fractions containing 100 g and 200 g of FS were exposed to MW irradiation at three input MW power levels of 465, 1085 and 1550 W at different exposure times ranging from 0.5 to 14 min. The variation in the FS temperature, pathogen reduction via the destruction of E. coli and Ascaris lumbricoides eggs, and vol/wt reduction were measured during the MW treatment. It was demonstrated that the MW technology can rapidly and efficiently achieve complete reduction of E. coli and Ascaris lumbricoides eggs, and over 70% vol/wt reduction in the fresh FS. Furthermore, the successful evaluation of the MW technology under real field conditions demonstrated that MW irradiation can be applied for rapid treatment of fresh FS in situations such as urban slum and emergency conditions.

The Impact of Conditional Cash Transfer on Toilet Use in eThekwini, South Africa

In the developing world, having access to a toilet does not necessarily imply use: infrequent or non-use limits the desired health outcomes of improved sanitation. We examine the sanitation situation in a rural part of South Africa where recipients of novel, waterless “urine-diverting dry toilets” are not regularly using them. In order to determine if small, conditional cash transfers (CCT) could motivate families to use their toilets more, we paid for urine via different incentive-based interventions: two were based on volumetric pricing and the third was a flat-rate payment (irrespective of volume). A flat-rate payment (approx. €1) resulted in the highest rates of regular (weekly) participation at 59%. The low volumetric payment (approx. €0.05/L) led to regular participation rates of only 12% and no increase in toilet use. The high volumetric payment (approx. €0.1/L) resulted in lower rates of regular participation (35%), but increased the average urine production per household per day by 74%. As a first example of conditional cash transfers being used in the sanitation sector, we show that they are an accepted and effective tool for increasing toilet use, while putting small cash payments in the hands of poor, largely unemployed populations in rural South Africa.

Assessing the promotion of urine-diverting dry toilets through school-based demonstration facilities in Kalisizo, Uganda

Urine-diverting dry toilets (UDDTs) are designed to recover nutrients and organic matter from human excreta for agricultural reuse. Their wider implementation could help address problems in areas where water scarcity limits coverage of sanitation systems and declining soil fertility jeopardizes nutritional security. Demonstration facilities can improve stakeholders’ views of UDDTs; however, it is uncertain whether these facilities should be located at households or institutions. Using a novel methodological approach that included qualitative data collection before and after introduction of demonstration UDDTs and quantitative monitoring of treatment conditions, this study evaluated changes in local attitudes and knowledge resulting from a UDDT promotion strategy at two primary schools in Uganda. Before introduction, students had little knowledge of UDDT facilities, while most attitude-related statements conveyed negative viewpoints and skepticism. After introduction and six months of operation, students exhibited increased knowledge, and 68% of attitude-related statements conveyed positive opinions that focused on the UDDTs’ long-term economic value and their role in creating a more hygienic school environment. These changes were seen in facility users and in other students at the schools who were non-users. In the future, with these improved perceptions, students could become compelling representatives for UDDTs within their communities, potentially increasing adoption.

Estimation of Ascaris lumbricoides egg inactivation by free ammonia treatment of ash-amended UDDT vault products using stored urine in Uganda

Urine-diverting dry toilets (UDDTs) are designed to recover nutrients and organic matter from human excreta for use as agricultural amendments, and have been promoted in many developing countries, including Uganda. Wider UDDT implementation could help address problems in areas where water scarcity limits sanitation coverage and/or declining soil fertility jeopardizes growing populations’ nutritional security. However, concerns have been raised regarding the safety of recovered UDDT vault products, which may contain persistent pathogens such as Ascaris lumbricoides eggs. A. lumbricoides eggs can be inactivated through elevation of free ammonia levels. This study assessed the feasibility of a secondary ammonia treatment strategy for UDDT ash-amended vault products using urine. Treatment parameters were measured in mixtures of urine, ash-amended vault products, and wood ash, a model was developed to account for temperature fluctuations, and A. lumbricoides egg inactivation times were estimated using a previously published model. A mixture containing two parts urine and one part ash-amended vault products was estimated to provide 2-log10 inactivation after 3 months of indoor storage (daily mean temperatures: 22.8 ± 0.3 °C) or 2 months of outdoor storage (25.9 ± 1.3 °C). This strategy could improve the safety of recovered products for agricultural use to improve the nutritional security of vulnerable populations.

Promoting Sanitation in South Africa through Nutrient Recovery from Urine

The water utility of Durban, eThekwini Water and Sanitation (EWS), installed urine-diverting dry toilets to provide sanitation to under-served communities in rural and peri-urban areas. While faeces was treated by dehydration, urine was discharged into a soak away in the ground. EWS teamed up with the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and other partners in Switzerland and South Africa to valorise this resource. The VUNA project developed a sanitation system which produces a valuable fertiliser from urine, reduces pollution of water resources and promotes the acceptance of dry toilets.