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Specific models for the rational design of pit latrines of different shapes and sizes are presently non-existent. What exist are general design models irrespective of the shape and size of latrine which may not give the actual design parameters needed. This research was limited to the derivation of models that will aid the design of the capacity of pit latrines of different shapes and dimensions for different population of users and under different soil formations and ground conditions. The objective of this research was to derive models for the rational design of pit latrines of different shapes using data collected from 500 different household pit latrines already filled up. Thus, models were derived for different latrine pit shapes and sizes using data collected through the administration of designed questionnaire on 500 households having pit latrines already filled up. Models were developed specifically for different latrine shapes whereas those of other researchers were generalized. These models were calibrated and verified for the rational design of pit latrines of different shapes and sizes. The regression coefficients for calibration were 0.75, 0.65, and 0.50 and for verification are 0.97, 0.98 and 0.99 for square, circular and rectangular pits respectively. The implication of this research is availability of design models for the construction of different pit latrine shapes.

Faecal sludge deposited into the pit latrine is subject to biodegradation. The aim of this research was to develop model for the filling rate of faeces in ordinary pit latrine together with the effect of shape factor on such fillings to prepare the minds of users on the filling characteristics of the pit based on contents, usage and environmental factors. Consequently, faecal sludges sampled from 100 pits already filled were subjected to laboratory analyses for their physico-chemical and biological characteristics. Models for the actual filling rate of faeces in ordinary pit latrines were derived using BOD, COD, VS, and TS data, calibrated and verified. For a more critical situation, models were also derived for the filling rates considering pit shapes that gave the actual pit filling in comparison with the general condition. From the results, the actual filling rate was lower than those obtained using BOD, VS and TS. However, the COD gave filling rate closer to the actual filling rate than other parameters since TS could not be used to assess the filling rate of faeces in pit latrines. The pits exhibited low filling rate in terms of BOD in 2 pits. In terms of COD, the filling rate was higher compared with that of BOD. Low filling rate was observed with volatile solids and only 3 pits exhibited moderately high filling rates whereas total solids had the highest number of pits with high filling rates. The filling rates for both the square and rectangular pits increased by 26.5% from 40 – 90 ℓ/capita/year to 50 – 112 ℓ/capita/year due to the shape factor and this was above the values obtained in existing models while that of the circular pit remained the same. Reduction in pit volume and increase in filling rate by faeces was due to dead corners as a result of clogging, thereby reducing the area available for faecal infiltration into the surrounding soil. Circular pits are more stable because of the natural arching effect of the ground around the hole and there are no corners to concentrate the stresses. Pits with flat sides are much more likely to develop clogging resulting to dead corners than the circular pit. From this study, it is therefore evident that the shape of pit latrine determines the actual volume and the filling rate of faeces in pit latrine taking into consideration geological and environmental factors. Thus for optimal design, our engineers should take note of the pit shape factor. Thus, the model can be used to determine the filling rate of ordinary pit latrines considering soil characteristics, ground conditions and other favourable conditions.&nbsp

There is limited information about the characteristics of faecal sludges in ordinary pit latrines. Knowledge of the physico-chemical and biological characteristics of pit sludge from different layers of the pit apart from providing an indication of the nature of pit contents endeavoured to provide information and decision support for managing pit latrines during their normal lifespan. Therefore, this paper was aimed at investigating the physico-chemical and biological characteristics of pit sludge samples to equip latrine owners with environmental and health implications of this sludge. Legislation that establishes regulations specifically for the treatment and discharge, enduse, or disposal of faecal sludge is therefore essential. Thus, faecal sludges sampled from ten (10) pit latrines were subjected to laboratory analyses with particular reference to selected parameters. From the study, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total solids (TS), moisture content, suspended solids (SS) and volatile solids (VS) showed decreasing trend throughout as the pit depth increased. Temperature presented double scenarios, increasing initially and decreasing afterwards with the highest values within 0.4m to 0.6m pit depth in all the pit latrines. Efforts to understand and mitigate the health effects of particulate matter (PM) air pollution have a rich and interesting history. This review focuses on six substantial lines of research that have been pursued since 1997 that have helped elucidate our understanding about the effects of PM on human health. There has been substantial progress in the evaluation of PM health effects at different time-scales of exposure and in the exploration of the shape of the concentration-response function. There has also been emerging evidence of PM-related cardiovascular health effects and growing knowledge regarding interconnected general pathophysiological pathways that link PM exposure with cardiopulmonary morbidity and mortality. Despite important gaps in scientific knowledge and continued reasons for some skepticism, a comprehensive evaluation of the research findings provides persuasive evidence that exposure to fine particulate air pollution has adverse effects on cardiopulmonary health. Although much of this research has been motivated by environmental public health policy, these results have important scientific, medical, and public health implications that are broader than debates over legally mandated air quality standards.

This study was carried using finite element software (Plaxis) in studying the Engineering behavior of erodible soil-quarry dust composite at a proportion of 50% quarry dust and 10% cement. It discusses the effects of decorative street light through numerical analysis using the Finite Elements Method. Plaxis program v8.2 was applied to model the soil behavior. The Mohr-Coulomb model reveals that the deformations are concentrated exclusively on the base course, with the appearance of plastic tension cut-off points on base course. The structure was subjected to double point loads of 50 kN/m each which resulted to 100 kN/m. The results shows that the pavement deformed at load 85.16kN/m which showed that the soil strength cannot withhold the pressure from the street light. The load displacement acting on the base of the highway in study is . The result also shows that failure was concentrated at the base course of the pavement. This was due to the presence of underground water beneath the phreatic level. The quarry dust is a good replacement to weak soil or a good additive to help improved a problematic soil. From analysis, the soil strength lies below the effective stress acting on the pavement which is equal to 85.16 kN/m. It is advisable to replace some quantities of the existing soil and be replaced by quarry dust since quarry dust is a waste product from crushing of stones. Lastly, about 30% of the existing soil should be replaced by either the mixture of lateritic soil and quarry dust or the soil there should be used as subbase which may not be economical.