Designing pit emptying technologies: combining lessons from the field with systems thinking

The ideal pit emptying machine has been envisioned to be safe, hygienic, and economical, while being mobile and lightweight, allowing access to pits located away from main roads. The machine should be robust, should be amenable to easy operation by a few personnel, and can be maintained using local expertise and supplies. Using the insights from a recent workshop and our own field experience, we discuss the challenges of designing such a machine, and broaden the discussion to include the entire system of pit emptying, collection, and transport. We classify pit emptying technologies according to the type of pit (e.g., wet pits with little trash, wet pits with lots of trash, and dry pits with lots of trash), and argue that designing technologies accordingly should be the focus in the future. A systems approach that includes transport optimisation, sustainability of small businesses, and operator safety and training is advocated

Characterization of pit latrines to support the design and selection of emptying tools in peri-urban Mzuzu, Malawi

The urban areas of many low-income countries must balance a rising demand for pit latrines for household sanitation provision against limitations in space, resulting in a need for pit latrine emptying services. This study was undertaken in the peri-urban neighborhood of Area 1B in the city of Mzuzu, Malawi, to examine the characteristics of household pit latrines for designing and selecting pit latrine emptying tools. We used 150 structured household surveys and field observations. From this, a subset was selected and 30 manual cone penetrometer tests were conducted at full latrines. Chemical oxygen demand analysis was also performed for 14 pit latrines. The results indicated that in addition to serving as a disposal for fecal matter, 90% of households also used pit latrines for domestic waste. Only 10% of the studied pit latrines were lined. The filling rate in the study area is calculated to be about three years, and no respondents reported previous emptying. It is suggested pit latrine emptying technology development focuses on a maximum tool diameter of 10 cm to fit through the keyhole (squat hole) and height of 146 cm to fit inside the superstructure, as well as supporting unlined pits and the ability to pump trash

Educating sanitation professionals: moving from STEM to specialist training in higher education in Malawi

Achieving the United Nations Sustainable Development Goals (SDGs) requires effective changes in multiple sectors including education, economics, and health. Malawi faces challenges in attaining the SDGs in general, and specifically in the sanitation sector. This paper aims to describe the existing landscape within public universities in Malawi to build a framework for training a cadre of locally trained experts. This is achieved by reviewing science, technology, engineering, and mathematics (STEM) degree programmes and assessing the extent of inclusion of sanitation education. The historical compartmentalization of academic programmes has resulted in few programmes to build on. Deliberate investment is needed to build from the current STEM higher education landscape to an effective framework for training sanitation experts, especially female experts. For low-income countries such as Malawi, a cadre of ~17,600 locally trained sanitation experts may be needed, for which the current higher education landscape is not sufficient. Using the Centre of Excellence in Water and Sanitation at Mzuzu University in Malawi as a case study, this paper provides a model of sanitation education in low-income countries that: 1) provides an effective complementary contribution to delivering sanitation education; 2) links to overall SDGs, national policy, university goals, and localized needs; and 3) engages students, faculty, and communities in local research

Trash removal methods for improved mechanical emptying of pit latrines using a screw auger

Trash in pit latrines is one of the largest challenges facing pit emptying technologies, including the powered auger (the Excrevator), developed for improved emptying in lower- and lower-middle income countries. This study focused on two trash removal methods in conjunction with pit emptying by the Excrevator: (1) simultaneous removal of trash with sludge and (2) manual trash removal prior to sludge removal. Simultaneous removal was tested by adding to the inlet of the Excrevator system two cutting heads designed to reduce the size of trash particles before entering the pipe and auger. Laboratory testing indicated that the auger will not provide the rotational speeds necessary for proper maceration of fibrous materials such as clothing, indicating that a separate maceration unit with higher rotational methods may be more appropriate. Four manual trash removal mechanisms were designed to improve on existing manual trash ‘fishing’ tools such as iron rods with fixed hooks. Two of these tools (the ‘claw’ and the ‘hook’) showed promising laboratory results and were subsequently field tested in Mzuzu, Malawi. Both tools proved more efficient than the current tools used in the field and have potential for use in Malawi

Microbial community function and bacterial pathogen composition in pit latrines in peri-urban Malaw

Despite the widespread global reliance on pit latrines as improved sanitation systems, the decomposition of waste within pit latrines is poorly understood. One area needing elucidation is the characterization and function of microbial communities within pit latrines. To address this gap, we characterized the microbial communities of 55 lined pit latrines at three sampling layers from two communities in peri-urban Malawi. The microbial communities of the fecal sludge samples were analyzed for beta diversity, pathogen presence, and functional profiling. Household surveys were conducted and used to compare microbial community patterns to household characteristics and pit latrine use patterns. Compared to activated sludge, anaerobic digestion in municipal wastewater systems, and human gut microbiomes, pit latrines were found to contain unique microbial communities. While the microbial community composition as a whole did not vary by sampling depth, pathogen composition varied by sampling depth, location, and household water source. The inferred microbial function also varied by depth (e.g., increase in methanogens and decrease in aerobes with depth). The richness of lined pit latrines determined from surface samples from eight latrines was found to be representative for a given area. Samples from middle and lower depths collected using a Gulper pump did not provide more information on richness, a result that informs future sampling designs. These findings are important for improving waste-based epidemiology (WBE) approaches to understand community health and waste degradation characterization of lined pit latrines

Microbial community function and bacterial pathogen composition in pit latrines in peri-urban Malawi

Despite the widespread global reliance on pit latrines as improved sanitation systems, the decomposition of waste within pit latrines is poorly understood. One area needing elucidation is the characterization and function of microbial communities within pit latrines. To address this gap, we characterized the microbial communities of 55 lined pit latrines at three sampling layers from two communities in peri-urban Malawi. The microbial communities of the fecal sludge samples were analyzed for beta diversity, pathogen presence, and functional profiling. Household surveys were conducted and used to compare microbial community patterns to household characteristics and pit latrine use patterns. Compared to activated sludge, anaerobic digestion in municipal wastewater systems, and human gut microbiomes, pit latrines were found to contain unique microbial communities. While the microbial community composition as a whole did not vary by sampling depth, pathogen composition varied by sampling depth, location, and household water source. The inferred microbial function also varied by depth (e.g., increase in methanogens and decrease in aerobes with depth). The richness of lined pit latrines determined from surface samples from eight latrines was found to be representative for a given area. Samples from middle and lower depths collected using a Gulper pump did not provide more information on richness, a result that informs future sampling designs. These findings are important for improving waste-based epidemiology (WBE) approaches to understand community health and waste degradation characterization of lined pit latrines