Ventilated Improved Pit Latrines Research Articles

Compliance of private ventilated improved pit latrines to odour and fly control guidelines: A technical audit in selected regions of Ghana

The ventilated improved pit (VIP) latrine offers a promising route to safely managed sanitation to many households in developing countries. However, some technical guidelines must be followed in order to realise the technology's advantage of odour and fly nuisance control. This study sought to audit private VIP latrines in selected regions of Ghana to assess their compliance to conventional technical guidelines and to understand the major factors that influence the latrine designs. An inspection checklist was developed to assess 296 private VIP latrines in the Central, Ashanti and Northern Regions of Ghana while semi-structured interviews were conducted among the latrine owners to enquire the factors that influenced the designs of their latrines. The results show that provision of a window in the superstructure (86 %), and the avoidance of an insect screen in the window(s) (77 %) were the most complied guidelines. The use of 150 mm diameter vent pipe was the least satisfied guideline (5 %). On the average, a latrine satisfied about half (3.6) of the technical guidelines that were assessed. The decision or advice of local artisans is the most influential factor in the design of the latrines. Cost was the least mentioned factor cited by the latrine owners. There is the need to establish information desks at the various Metropolitan, Municipal and District Assemblies (MMDAs) to guide prospective owners on the proper design and construction of the VIP latrine. In addition, toilet construction should be incorporated in the curriculum for the basic training of building and construction students in Technical and Vocational Education and Training (TVET) institutions in Ghana. Further research is required to ascertain the basis of the decisions of local artisans and the potential impact of the use of accessories that are ‘borrowed’ from the WC toilet on odour and fly control in the latrine.

Comparative life cycle assessment of excreta management systems through composting and biomethanization: Case of a low-income tropical country.

Low-income tropical regions, such as Haiti, grapple with environmental issues stemming from inadequate sanitation infrastructure for fecal sludge management. This study scrutinizes on-site sanitation systems in these regions, evaluating their environmental impacts and pinpointing improvement opportunities. The focus is specifically on systems integrating excreta valorization through composting and/or anaerobic digestion. Each system encompasses toilet access, evacuation, and sludge treatment. A comparative life cycle assessment was undertaken, with the functional unit managing one ton of excreta in Haiti over a year. Six scenarios representing autonomous sanitation systems were devised by combining three toilet types (container-based toilets (CBTs), ventilated improved pit (VIP) latrines, and flush toilets (WC)) with two sludge treatment processes (composting and biomethanization). Biodigester-based systems exhibited 1.05 times higher sanitary impacts and 1.03 times higher ecosystem impacts than those with composters. Among toilet types, CBTs had the lowest impacts, followed by VIP latrines, with WCs having the highest impacts. On average, WC scenarios were 3.85 times more impactful than VIP latrines and 4.04 times more impactful than those with CBTs regarding human health impact. Critical variables identified include the use of toilet paper, wood shavings, greenhouse gas emissions, and construction materials.

Evaluation of knowledge, attitude, practices and effectiveness of menstrual hygiene interventions in rural schools from Lilongwe, Malawi

BackgroundMenstrual hygiene management (MHM) is associated with the menstrual process in women and adolescent girls who face cultural and financial challenges in rural areas of many developing countries. As part of the pilot study, we assessed the sustainability and effectiveness of the approaches and lessons learned from the MHM project intervention in rural areas of Lilongwe, Malawi.MethodsRural primary schools (n = 4) were purposively selected where an MHM intervention was implemented in Lilongwe, Malawi. The study employed a mixed-method research design. Assessments and data collection were performed through surveys of learners, literature reviews, key informant interviews (KIIs) (n = 90), and 20 focus group discussions (FGDs). The study participants included boys and adolescent girls (n = 100, 11–19 years; grades 5–8), teachers, mother groups, and community leaders from the selected schools.ResultsAll the schools had water sanitation and hygiene facilities and latrines (45% improved, 54% ventilated improved pit latrines – VIPs) that promoted menstrual hygiene for adolescent girls. However, two of the schools studied (50%, n = 4) did not have separate washrooms for changing sanitary materials. There was a slight increase in latrine coverage in Kabuthu zone communities (90% at baseline versus 93.4% at midterm). However, the coverage dropped to 85.7% at the final evaluation, which was attributed to too much rain received in the area that damaged most of the latrines. There was a significant reduction (p < 0.05) in the number of girls failing to attend classes due to menstruation (70% at baseline versus 14% at final evaluation). Furthermore, the project resulted in the majority of girls (94.4%) having access to school. There was a strong uptake and adoption of sanitary products (reusable pads and menstrual cups) among adolescent girls of all age groups. The study has demonstrated that the inclusion of key stakeholders such as health workers, parents, mother groups and community leaders promoted the uptake and sustainability of reusable pads and menstrual cups and MHM interventions and programs.ConclusionThe MHM project implementation improved adolescent girls’ education in the area. The inclusion of boys and other key stakeholders in the health education talks addressed issues of stigma and discrimination. The study, therefore, calls for comprehensive training on MHM and hygiene education to remove discrimination and harmful cultural practices.

Understanding Households' Willingness to Pay for Improved Sanitation Services in Benin: A Study Protocol.

Nowadays, in Benin, latrine construction by households highly depends on their financial contributions. However, empirical evidence shows that many households are unwilling to invest in adequate sanitation services. The study aims to determine the household's willingness to pay for improved sanitation services and the associated factors. The study population will include households lacking unimproved sanitation facilities. The household heads will be eligible for survey participation. We will perform a contingent valuation to determine households' willingness to pay for a Ventilated Improved Pit (VIP) latrine. Following a description of the surveyed population, we will assess willingness to pay using the 'doubleb' command in Stata. Subsequently, we will conduct multivariate logistic regression to determine the factors associated with willingness to pay. The expected results will be: a description of the basic characteristics of households without improved sanitation services, an estimation of household willingness to pay for VIP latrines using the contingent valuation, and factors associated with household willingness to pay for VIP latrines. This study will contribute to the literature on household demand for improved sanitation services in Benin.

Ventilated improved pit latrine: a theoretical evaluation of conventional design guidelines, user adaptations and prospects for improvement

The ventilated improved pit latrine has the potential of meeting the sanitation needs of many households in developing countries and enhance the chances of attaining the Sustainable Development Goal (SDG) 6. However, some user adaptations of the technology appear to conflict with conventional design guidelines and may compromise the ventilation rate in the vent pipe. This would negatively affect the odour control function of the technology. This paper seeks to evaluate existing conventional design guidelines that are aimed at controlling odour and fly nuisance in the latrine to highlight their relevance and possible conflicts with existing and emerging user adaptations. It also identifies potential structural modifications that may be adopted to accommodate emerging user preferences without compromising the odour control mechanism. The review shows that, indeed, some construction practices such as provision of windows in multiple sides of the superstructure adversely affect the ventilation rate and could lead to odour problems. However, the effects of some suspected unfavourable user adaptations such as use of closed-top vent caps and ceramic seats with covers have not been investigated. Furthermore, recent studies have demonstrated the possibility of compensating for the negative effect of some user preferences with favourable environmental conditions such as high wind speed and structural modifications using a mathematical model. However, the existing model fails to account for some key design criteria and needs to be improved to make it useful for a wider application.

Wind Speed Thresholds for Adjusting Conventional Design Criteria for the Ventilated Improved Pit Latrine without Compromising Odour Control

Aims: The objective of this paper is to re-evaluate the wind speed threshold at which the 100 mm polyvinyl chloride (PVC) vent pipe may be used without compromising the ventilation rate required for effective odor control in a ventilated improved pit (VIP) latrine. The paper also sought to investigate the chances of leveraging upon high wind speeds to grant user preferences for multiple windows and installation of insect screens, which are conventionally forbidden.&#x0D; Study Design: A comparative experimental design was carried out in a VIP latrine with internal cubicle dimensions of 1.2 m x 1.5 m built over a pit of cross-section 1.2 m x 2.5 m and depth of 3.0 m which was fitted with a 100 mm PVC vent pipe.&#x0D; Place and Duration of Study: The experimental setup was located on the compound of a public basic school in Prampram, a peri-urban coastal community in Southern Ghana. The setup was monitored for twelve hours a day (5 am to 5 pm) for twelve days.&#x0D; Methodology: The experimental setups comprised of four designs of the VIP latrine: single-window and multi-window designs each with and without insect screen in the window. The ventilation rate in each modified design was monitored simultaneously with the external wind speed.&#x0D; Results: The results of the study indicate that the 100 mm PVC vent pipe could attain the recommended ventilation rate of 20 m3/h at an average wind speed as slow as 1.5 m/s as compared to the 3 m/s previously suggested. The influence of wind speed on the ventilation rate is insignificant at wind speed variations not exceeding 0.5 m/s when the 100 mm PVC vent pipe is used.&#x0D; Conclusion: At an average wind speed of 1.5 m/s, either the multiple-window design or insect screen used in combination with the 100 mm PVC vent pipe could attain the recommended ventilation rate and should not be outrightly forbidden. However, a wind speed threshold of 2.5 m/s is required for the adoption of the multi-window design with insect screens when the 100 mm PVC vent pipe is used.

Prevalence and predictors of intestinal schistosomiasis among the adult population, and water and sanitation conditions - A community-based cross-section study at Muleba District, Tanzania

INTRODUCTION: Intestinal schistosomiasis is one of the serious public health problems in all age groups and can lead to considerable morbidity and mortality, especially in communities with an inadequate supply of safe water and sanitation services. This study was conducted to establish the current burden of intestinal schistosomiasis among adults in the Muleba District and assess water and sanitation conditions that might influence the transmission of intestinal schistosomiasis.METHODS: A community-based cross-sectional study was conducted between July and August 2020. A total of 328 stool samples were collected and processed using formal-ether concentration and Kato-Katz methods. Water and sanitation data were collected using a questionnaire interview conducted among participants. Participants were randomly selected from four villages. Data were analyzed using Statistical Package for the Social Sciences software version 23.RESULTS: Thirty-six participants (11%) were infected with Schistosoma mansoni. The prevalence was higher among households using water from improved sources, houses without sanitation facilities, and participants who do not use sanitation facilities. We found a significantly increased risk of S. mansoni infection among participants in households without toilet facilities than those with ventilated improved pit latrine (OR =4.10, p = 0.001).CONCLUSION: The prevalence of intestinal schistosomiasis infection among the adult population in Muleba indicates a moderate risk of transmission. The type of toilet facility is a significant factor in the perpetuation of S. mansoni transmission.

Drivers and barriers to sustained use of Blair ventilated improved pit latrine after nearly four decades in rural Zimbabwe.

BackgroundSome latrines remain unused even under conditions of high coverage in rural areas of low- and middle-income countries. Not much is known on household latrine use in the long term in the absence of an intervention. The current work assesses drivers and barriers to sustained use of a ventilated improved pit latrine (Blair VIP) design where it originated and how rural households adapt it to climate change.MethodsA mixed methods study was conducted from November 2020 to May 2021 among rural households of Mbire district, Zimbabwe. A cross sectional survey of 238 households with Blair ventilated improved pit (BVIP) latrines was conducted using a questionnaire and a latrine observation checklist. Data were analysed using logistic regression. Qualitative data were collected using six focus groups among house heads and analysed by thematic analysis.ResultThe latrine has perceived health, non-health and hygiene benefits for its sustained use. However, there are design, environmental and social barriers. The quantitative study indicated that determinants of latrine use were contextual (individual and household levels) and technology (individual level) factors. Focus groups indicated that latrine use was influenced by social, technology and contextual factors at multiple level factors. Interplay of factors influenced the intention to adapt the BVIP latrine to climate change. Local climate change adaptation strategies for the latrine were odour and erosion control, construction of the conventional latrine design and raised structures.ConclusionThe conventional BVIP latrine design is durable and relatively resilient to climate change with high local household use. High construction cost of the latrine causes households to build incomplete and poor quality designs which affect odour and fly control. These are barriers to sustained latrine use. The government should implement the new sanitation policy which considers alternative sanitation options and offer community support for adapting sanitation to climate change.

Convective drying kinetics of faecal sludge from VIP latrines

In striving to achieve sustainable sanitation, one challenge is to ensure hygienic treatment of faecal sludge from on-site sanitation. Thermal drying is an important treatment step for moisture removal and disinfection. Improved understanding of the drying process is crucial for the proper design of treatment technologies for faecal sludge. In this study, faecal sludge from ventilated improved pit (VIP) latrines from Durban, South Africa, were dried in a convective drying thermobalance by varying the temperature from 40 to 80 °C, the relative humidity from 0 to 25% and the air velocity from 0.3 to 1.2 mm/s. The faecal sludge samples were in the form of a thin layer and pellets with different diameters from 8 to 14 mm. Kinetic parameters were determined from the experimental data, were compared to classical drying models in literature and were then used to develop a correlative drying model.Drying rates ranged between 1 and 40 g/min/m2, leading to drying times comprised between 100 and 300 min. The drying kinetics increased as temperature was higher, and pellet diameter and relative humidity were lower. Temperature had the greatest influence on the drying kinetics (in both the constant and falling rate periods), followed by the effect of pellet diameter. The drying kinetics were affected in a moderate way by the relative humidity in the constant rate period and part of the falling rate period. The air velocity had a slight effect of drying kinetics during the constant rate period, but this becomes insignificant during the falling rate period. The effective diffusivities increased from 7.81 × 10−8 to 1.97 × 10−7 m2/s by increasing the temperature from 40° to 80 °C, leading to an activation energy of 23 kJ/mol. These values are typical from those found for wastewater sludge. The sludge exhibited a critical moisture content varying between 2.4 and 3.2 g/g db during drying without a clear trend as a function of the operating conditions and suggested that sludge was composed of considerably more bound moisture than unbound.The experimental data fitted the most closely to the Page model and, based on this, a new model was proposed for the prediction of drying times across the range of explored temperatures and pellet diameters in this study. The results of the proposed model fitted the experimental data with acceptable accuracy, so that the developed model could be employed as an analytical tool for the design, operation and optimisation of drying equipment.

Manual emptying of ventilated improved pit latrines and hygiene challenges - a baseline survey in a peri-urban community in KwaZulu-Natal, South Africa

ABSTRACT The presence of Escherichia coli and Staphylococcus spp. was determined on the skin, personal protective equipment, the municipal vehicle, and various surfaces at ten households in a peri-urban community (KwaZulu-Natal, South Africa) before and after manual emptying of ventilated improved pit latrines. Surface samples (n = 14) were collected using sterile wet wipes, and target bacteria were detected using standard procedures. Additionally, E. coli was enumerated in soil samples from an area of open defecation (log10 3.7 MPN/g) and areas where geophagia occurred (log10 2.7 – log10 3.3 MPN/g), using a most probable number (MPN) method. The detection frequency for the target bacteria on household surfaces (e.g., the walkway between the pit latrine and the municipal vehicle) and on municipal workers’ hands (which were frequently contaminated before pit emptying), occasionally increased after the pits were emptied, indicating that manual pit emptying might pose a potential health risk to workers and community members.

Drying of faecal sludge from VIP latrines through a medium infrared radiation process

In order to treat faecal sludge from ventilated improved pit (VIP) latrines, eThekwini Municipality (Durban, South Africa) developed an infrared dryer, ‘LaDePa’ (Latrine Dehydration Pasteurization). Parameters that influence its operation were investigated using a laboratory-scale replica of the full-scale machine. For this, faecal sludge collected from VIP latrines was pelletized and dried under different operating conditions. Drying curves were obtained by plotting medium wave infrared intensity (MIR), height of emitters above the belt, air flowrate and pellet diameter against the residence time. These curves were then used to determine the drying rate and energy consumption. The results show that the drying rate increased while the energy consumption decreased by increasing the power of the MIR emitters and decreasing the size of the pellets. For example, the drying time to get a moisture content of 0.8 g water/g dry solid was shortened from 27 to 6 min while the energy consumption for this reduced from 1.5 to 0.8 kWh after increasing the MIR power from 1.5 to 3.3 kW. Similar drying curves were obtained by varying the distance between the pellets and MIR emitters, and adjusting intensity of the MIR radiation to obtain the same temperature in the drying zone. It was also observed that higher airflow rates enhanced mass transfer rates, but led to a cooling effect. No effect on the drying rate was observed after pre-drying the sludge or adding sawdust. The study shows that for the process to be efficient, the MIR intensity should be high enough for fast drying to occur (T ≥ 150°C), but without causing thermal degradation (T ≤ 220°C). The height of emitter above the belt and the pellet size should be as small as possible (8 mm); airflow rate should be optimised to maximize the mass transfer rate and minimize the cooling effect.

Characterization of Faecal Sludge from Pit Latrines to Guide Management Solutions in Cape Coast, Ghana

This study characterised faecal sludge from public ventilated improved pit (VIP) latrines in Cape Coast to assess their potential impact on the environment and to guide the selection of appropriate management solutions. The paper also estimates the amount of beneficial resources wasted due to the lack of a faecal sludge (FS) treatment facility. The study employed a quantitative design involving laboratory analysis of FS sampled from 13 purposively sampled VIP latrines in Cape Coast, Ghana. Sampling activities were carried out in January and February (dry season) and September and October (wet season) of 2015. Samples of unhardened pit latrine sludge were collected from all 13 pit latrines for quality assessment. Physicochemical parameters (moisture content, COD, BOD5, total solids and total volatile solids) of homogenous samples from the surface, middle and bottom of pit contents were analysed following standard procedures. Apart from total solids, all other parameters decreased with the depth of sampling and the differences were statistically significant (p&lt;.01). Seasonal variation in faecal sludge characteristics was not significant except for BOD5. A high COD: BOD5 (3.8-4.5:1) shows faecal sludge that is characterised by slowly degradable organic matter. Even though the FS at the bottom of the pits was found to be the most stabilized, its characteristic parameters indicate that discharging it into the environment without any further treatment would pose a significant threat to public health. The characteristics suggest that co-composting would be the most appropriate option for treating the FS and also underscore the fact that the VIP latrine technology is not suitable for use as a public toilet.

Factors associated with perception of bad odor by users of ventilated improved pit latrines in Cape Coast, Ghana

Perception of bad odor in sanitation facilities is one of the causes of open defecation, which is a major cause of water pollution in developing countries. This study assessed how users of ventilated improved pit (VIP) latrines in Cape Coast, Ghana, perceive the level of odor in their latrines and identified the factors associated with perception of bad odor. A total of 211 users of 127 VIP latrines were purposively sampled from selected communities within the City. A semi-structured questionnaire was used to obtain information on the users’ perception of the odor level measured on an ordinal scale. The questionnaire also enquired the users’ characteristics and observations about the hygienic conditions of their toilets. An inspection checklist was used to assess the design and construction features of the latrines as well as the usage and maintenance practices. It was found that having a stake in a latrine’s ownership reduces the odds for perceiving bad odor in the latrine while attainment of higher education increases the odds. Furthermore, perception of bad odor was found to be more associated with the usage and maintenance practices (such as fouling of the squat hole or seat with excreta and mismanagement of used anal-cleansing materials) rather than the design and construction of the latrines. The findings of the study underscore the need to accompany the provision of sanitation facilities with user hygiene, as highlighted in the sanitation target of the sustainable development goals, else physical facilities alone cannot provide a guarantee against open defecation.

Mechanical properties of faecal sludge

On-site sanitation facilities contribute to the majority of toilet facilities in developing countries as full waterborne sanitation is not feasible or affordable. The characteristics of faecal sludge vary greatly between different locations and types of onsite sanitation facilities and at the same time their understanding is crucial for improvement of the existing faecal sludge management services. The Pollution Research Group (PRG), within the School of Chemical Engineering in the University of Kwa-Zulu Natal have been focussing on the analysis of faecal sludge from different on-site sanitation, such as urine diversion and dehydration toilets, wet and dry ventilated improved pit latrines at household and community levels and unimproved pit latrines. This study was undertaken between 2012 and 2014 and focussed on the characteristics of faecal sludge obtained from different on-site sanitation facilities in the Durban metro area in South Africa. Sampling methods were developed and applied for different depth levels of the pits for each on-site sanitation facility. The analysis followed the PRG standard operation procedures for properties such as: moisture content, total solids, ash content, pH, chemical oxygen demand, density, nutrient contents and thermal properties.

Design and construction of household ventilated improved pit latrines: gaps between conventional technical guidelines and construction practices in Cape Coast, Ghana

Abstract This study was conducted to identify the gaps that exist between ventilated improved pit (VIP) latrine construction practices in Cape Coast, Ghana, and conventional technical guidelines, and to assess how any non-compliance with technical guidelines influences the users' perception of odour and fly nuisances. An inspection guide was used to assess 127 VIP latrines, while a questionnaire survey was used to obtain feedback from 211 users of the latrines on their perception of odour and fly nuisance. Not a single latrine was found to be fitted with a vent pipe that satisfied the recommended diameter of 150 mm. Aside from the vent pipe diameter, only 5.5% of latrines complied with all four other design guidelines that were assessed. However, with the exception of failure to install insect screens on vent pipes, which was associated with the users seeing flies in the latrine cubicles, failure to comply with other guidelines did not necessarily lead to significantly higher user perception of the targeted nuisance. The findings of the study suggest that user perception of odour in their latrines may be more influenced by non-structural factors such as the management or cleanliness of the latrines rather than their structural designs.

Economic cost analysis of low-cost sanitation technology options in informal settlement areas (case study: Soweto, Johannesburg)

In Urban Africa, water and sanitation utility companies are facing a huge backlog of sanitation provision in the informal settlement areas. In order to clear this backlog, new investment is required. However, to select appropriate sanitation technologies, lifecycle costs need to be assessed. The aim of this research was to establish lifecycle costs for appropriate sanitation technologies in informal settlement areas. Three sanitation options were compared: simplified sewerage, urine diversion dry toilet (UDDT) and Ventilated Improved Pit (VIP) latrine. Three scenarios for simplified sewerage were considered; gravity flow into existing conventional sewers with treatment; new-build with pumping and treatment; and new-build gravity flow with treatment. The study revealed that simplified sewerage is the cheapest option for Soweto informal settlement, even when the costs of pumping and treatment are included. Gravity simplified sewerage with treatment is cheaper than the UDDT system and VIP latrine at all population densities above 158 and 172 persons/ha, respectively. The total annual cost per household of simplified sewerage and treatment was US$142 compared to US$156 and US$144 for UDDT and VIP latrine respectively. The costs of simplified sewerage could be recovered through a monthly household surcharge and cross-subsidy summing US$5.3 The study concluded that simplified sewerage system was the first choice for Soweto informal settlement areas, given the current population density.

The Impact of Improved Water, Sanitation, and Hygiene on Oral Rotavirus Vaccine Immunogenicity in Zimbabwean Infants: Substudy of a Cluster-randomized Trial.

BackgroundOral vaccines have lower efficacy in developing compared to developed countries. Poor water, sanitation, and hygiene (WASH) may contribute to reduced oral vaccine immunogenicity.MethodsWe conducted a cluster-randomized 2 × 2 factorial trial in rural Zimbabwe. Pregnant women and their infants were eligible if they lived in clusters randomized to (1) standard of care (52 clusters); (2) improved infant feeding (53 clusters); (3) WASH: ventilated improved pit latrine, 2 hand-washing stations, liquid soap, chlorine, infant play space, and hygiene counseling (53 clusters); or (4) feeding plus WASH (53 clusters). This substudy compared oral rotavirus vaccine (RVV) seroconversion (primary outcome), and seropositivity and geometric mean titer (GMT) (secondary outcomes), in WASH vs non-WASH infants by intention-to-treat analysis.ResultsWe included 801 infants with documented RVV receipt and postvaccine titer measurements (329 from 84 WASH clusters; 472 from 102 non-WASH clusters); 328 infants with prevaccination titers were included in the primary outcome. Thirty-three of 109 (30.3%) infants in the WASH group seroconverted following rotavirus vaccination, compared to 43 of 219 (19.6%) in the non-WASH group (absolute difference, 10.6% [95% confidence interval {CI}, .54%–20.7%]; P = .031). In the WASH vs non-WASH groups, 90 of 329 (27.4%) vs 107 of 472 (22.7%) were seropositive postvaccination (absolute difference, 4.7% [95% CI, –1.4% to 10.8%]; P = .130), and antirotavirus GMT was 18.4 (95% CI, 15.6–21.7) U/mL vs 14.9 (95% CI, 13.2–16.8) U/mL (P = .072).ConclusionsImprovements in household WASH led to modest but significant increases in seroconversion to RVV in rural Zimbabwean infants.Clinical Trials RegistrationNCT01824940.

Redesigning the ventilated improved pit latrine for use in built-up low-income settings

Abstract The ventilated improved pit (VIP) latrine has the potential to address the challenge of access to improved sanitation in built-up low-income settings. However, its conventional technical design fails to address the needs and preferences of some users. The objective of this paper was to test the technical performance of modified engineering designs of the technology to respond to some preferences of toilet users. The entry of air from multiple windows in the superstructure and installation of insect screens in windows were tested in an experimental VIP latrine. The modified design achieved the recommended ventilation rate of 20 m3/h when a vent pipe diameter of 150 mm was used. The study concludes that adopting a multidirectional airflow design leads to a lower ventilation rate as compared to the conventional design. However, when fitted with the recommended size of vent pipe, this modified design achieves more than twice the recommended ventilation rate with or without an insect screen installed in the windows. Nevertheless, the practice in which 100 mm diameter vent pipes are used with insect screens installed in windows is likely to lead to odour problems due to inadequate ventilation through the vent pipe.

Independent and combined effects of improved water, sanitation, and hygiene, and improved complementary feeding, on child stunting and anaemia in rural Zimbabwe: a cluster-randomised trial.

SummaryBackgroundChild stunting reduces survival and impairs neurodevelopment. We tested the independent and combined effects of improved water, sanitation, and hygiene (WASH), and improved infant and young child feeding (IYCF) on stunting and anaemia in in Zimbabwe.MethodsWe did a cluster-randomised, community-based, 2 × 2 factorial trial in two rural districts in Zimbabwe. Clusters were defined as the catchment area of between one and four village health workers employed by the Zimbabwe Ministry of Health and Child Care. Women were eligible for inclusion if they permanently lived in clusters and were confirmed pregnant. Clusters were randomly assigned (1:1:1:1) to standard of care (52 clusters), IYCF (20 g of a small-quantity lipid-based nutrient supplement per day from age 6 to 18 months plus complementary feeding counselling; 53 clusters), WASH (construction of a ventilated improved pit latrine, provision of two handwashing stations, liquid soap, chlorine, and play space plus hygiene counselling; 53 clusters), or IYCF plus WASH (53 clusters). A constrained randomisation technique was used to achieve balance across the groups for 14 variables related to geography, demography, water access, and community-level sanitation coverage. Masking of participants and fieldworkers was not possible. The primary outcomes were infant length-for-age Z score and haemoglobin concentrations at 18 months of age among children born to mothers who were HIV negative during pregnancy. These outcomes were analysed in the intention-to-treat population. We estimated the effects of the interventions by comparing the two IYCF groups with the two non-IYCF groups and the two WASH groups with the two non-WASH groups, except for outcomes that had an important statistical interaction between the interventions. This trial is registered with ClinicalTrials.gov, number NCT01824940.FindingsBetween Nov 22, 2012, and March 27, 2015, 5280 pregnant women were enrolled from 211 clusters. 3686 children born to HIV-negative mothers were assessed at age 18 months (884 in the standard of care group from 52 clusters, 893 in the IYCF group from 53 clusters, 918 in the WASH group from 53 clusters, and 991 in the IYCF plus WASH group from 51 clusters). In the IYCF intervention groups, the mean length-for-age Z score was 0·16 (95% CI 0·08–0·23) higher and the mean haemoglobin concentration was 2·03 g/L (1·28–2·79) higher than those in the non-IYCF intervention groups. The IYCF intervention reduced the number of stunted children from 620 (35%) of 1792 to 514 (27%) of 1879, and the number of children with anaemia from 245 (13·9%) of 1759 to 193 (10·5%) of 1845. The WASH intervention had no effect on either primary outcome. Neither intervention reduced the prevalence of diarrhoea at 12 or 18 months. No trial-related serious adverse events, and only three trial-related adverse events, were reported.InterpretationHousehold-level elementary WASH interventions implemented in rural areas in low-income countries are unlikely to reduce stunting or anaemia and might not reduce diarrhoea. Implementation of these WASH interventions in combination with IYCF interventions is unlikely to reduce stunting or anaemia more than implementation of IYCF alone.FundingBill & Melinda Gates Foundation, UK Department for International Development, Wellcome Trust, Swiss Development Cooperation, UNICEF, and US National Institutes of Health.

Optimising ventilation to control odour in the ventilated improved pit latrine

The rate of ventilation through the vent pipe of a ventilated improved pit latrine is the main technical factor that determines its efficiency in odour control aside the maintenance and cleaning practices of the users. Even though the factors affecting the ventilation rate have been well researched, they have not been previously related in a mathematical model to quantify the relative effect of the various factors on the ventilation rate. The objective of this paper is to develop such a model that could be used to optimise and predict the ventilation rate as a function of relevant design criteria and weather conditions. The ventilation rates produced by various design modifications in an experimental ventilated improved pit latrine were measured under monitored weather conditions. A linear regression model was used to assess the relative effect of the various design modifications and the elements of weather on the ventilation rate. It was found that the diameter of the vent pipe is the most important factor which accounts for 53% of variations in the ventilation rate, followed by the external wind speed, which accounts for 25% of changes in ventilation. The provision of windows in other sides of the superstructure other than the windward side leads to a reduction of 32% in the ventilation rate and accounts for 9% of the variations in the ventilation rate. A regression model developed in this study could be used to optimise and predict the ventilation rate based on a set of design criteria and meteorological data.