Determinants of diarrhoeal infections among users of shared sanitation in informal settlements in Durban, South Africa.

Diarrhoeal disease continues to be a major health problem in many parts of the world, especially in developing countries, mainly due to the lack of access to sanitation, water, and hygienic living conditions. Identifying the determinants of diarrhoeal infections continues to be a challenge in developing countries. In this study, we ascertained the factors behind diarrhoea among inhabitants of informal settlements in the city of Durban, South Africa. Prevalence of diarrhoea in the study area varied between 7-year historical clinical records and data collected during the current study (primary data), with the primary data giving the highest monthly prevalence odds ratio (POR) up to 18.1 (±1.6)%. The main factors associated with diarrhoeal infections were open defaecation (POR = 1.8; 95% confidence interval (CI): 0.9-3.12), use of shared sanitation (POR = 1.7; 95%; CI: 1.05-2.26), and exposure to faecal matter around the homes (POR = 1.69; 95% CI: 1.25-3.10). Several other factors were also determined to be associated with diarrhoeal infections, such as hygiene practices in the communities, the non-treatment of water before use, and the presence of solid waste and faecal materials around the households. This study shows that diarrhoeal disease infections in informal settlements could be multifactorial; therefore, a multifactorial approach is needed to reduce these infections. These could include improving education on hygiene practices within the home setting as well as in public places, such as the community ablution blocks.

Rheological characteristics of faecal sludge from VIP latrines and implications on pit emptying.

This work aims at characterizing the rheological properties of faecal sludge from Ventilated Improved Pit (VIP) latrines and their implication on pit emptying. Faecal sludge was sampled from 3 pit latrines located in the eThekwini Municipality (Durban, South Africa). Samples were taken at different positions within the pit. For each of the samples, measurements in the rheometer in triplicates were performed in order to determine their rheological properties, and their moisture and ash content were measured also in triplicates. Experiments in the rheometer were performed for samples for which its moisture content was modified. In order to better understand the influence of water addition into the pit. During pit emptying, calculations were carried out from the experimental data, based in the criteria set in the Omni-Ingestor initiative, carried out by the Bill & Melinda Gates Foundation. Faecal sludge exhibited a shear thinning behaviour, i.e. a decrease in viscosity with increasing shear rate, and presented a yield stress comprised between 500 to 1000 Pa. This needs to be surpassed in order to overcome the elastic resistance of the sludge to flow. Similar viscosities were found for the samples from the different pits, irrespective of the position within the pit, except for the sample from the bottom of one of the pits for which it was not possible to induce a flow. This sample had a considerably lower moisture content (67% wet basis) compared to the other samples (around 80% wet basis), probably due to a higher biodegradation as it was the most aged sludge in the pit. According to the experimental results and calculations, the pumping requirements during pit emptying will decrease drastically by increasing the moisture content of the sludge. The addition of water into the pit would then facilitate the pit emptying operation by reducing the head and power required for pumping. However, this practice would require employing considerable amounts of water and handling higher volumes of sludge, which would lead to longer pit emptying times and increase the difficulty of the operation. For example, increasing the moisture content of the sludge from 75 to 90% will reduce the head and power of the pump by a factor 100, but will triplicate the amount of water in the sludge and, consequently, the time for pit emptying. Therefore, a compromise has to be made between increasing the pumping feasibility and adding water to the pit.

The anaerobic baffled reactor (ABR) treating communal wastewater under mesophilic conditions: a review.

A review concerning the anaerobic baffled reactor (ABR) treating communal wastewater under mesophilic conditions is presented. Existing studies indicate strong resilience of the reactor towards loading variations and shock-loads. The compartmentalisation of the ABR is a strongly stabilising factor with feed fluctuations being evened out across reactor chambers. Significant chemical oxygen demand (COD) reduction occurs almost exclusively in the first three chambers. The hydraulic rather than the organic loading rate is treatment limiting. Laboratory-scale studies show high treatment efficiencies of above 80% COD removal. It was found that most laboratory-scale studies do not factor in important aspects of field operation, such as diurnal fluctuations of feed characteristics, adequate start-up periods and periods of constant loading and optimised chamber outlet design, and never studied the effect of loading on sludge digestion. Performance data on full-scale ABR implementations, however, are extremely scarce, and existing studies are without exception affected by site-specific treatment-limiting factors hindering the extrapolation of generally valid conclusions. In view of a large-scale roll-out, communal ABRs are not sufficiently understood. Current challenges concerning the optimisation of reactor design require numerous well-monitored long-term full-scale reactor investigations. Existing ABR investigations yield encouraging results, supporting that the ABR may be one of the solutions answering the global call for low-maintenance, robust treatment systems.

Viscous heating effect on deactivation of helminth eggs in ventilated improved pit sludge.

Viscous heating by extrusion of faecal material obtained from ventilated improved pit (VIP) latrines can be used to deactivate soil-transmitted helminth (STH) eggs by increasing the temperature of faecal sludge uniformly. Viscous heating can deactivate STH eggs present in sludge to make the material safer to transport, dispose of, or use in agricultural applications or as an energy source. The mechanical energy required to generate the shear rate can originate from any source. No other heat source or additive is required. Here we determined a baseline for the deactivation of STH eggs using viscous heating. To characterize equipment performance, three parameters were investigated: (1) minimum temperature required for deactivation; (2) local maximum temperatures for various flow rates and moisture contents (MCs); and (3) thermal efficiency. Excess water is undesirable since low viscosities require extended residence time and increased energy input. The minimum temperature to achieve greater than 90% helminth egg deactivation is 70 °C. For the laboratory-scale equipment tested, the maximum allowable mass flow rate for VIP sludge with 77% MC was found to be 3.6 g/s.

Ancient water and sanitation systems - applicability for the contemporary urban developing world.

The idea of implementing ancient water and wastewater technologies in the developing world is a persuasive one, since ancient systems had many features which would constitute sustainable and decentralised water and sanitation (WATSAN) provision in contemporary terminology. Latest figures indicate 2.6 billion people do not use improved sanitation and 1.1 billion practise open defecation, thus there is a huge need for sustainable and cost-effective WATSAN facilities, particularly in cities of the developing world. The objective of this study was to discuss and evaluate the applicability of selected ancient WATSAN systems for the contemporary developing world. Selected WATSAN systems in ancient Mesopotamia, the Indus Valley, Egypt, Greece, Rome and the Yucatan peninsula are briefly introduced and then discussed in the context of the developing world. One relevant aspect is that public latrines and baths were not only a part of daily life in ancient Rome but also a focal point for socialising. As such they would appear to represent a model of how to promote use and acceptance of modern community toilets and ablution blocks. Although public or community toilets are not classified as improved sanitation by WHO/UNICEF, this is a debatable premise since examples such as Durban, South Africa, illustrate how community toilets continue to represent a WATSAN solution for urban areas with high population density. Meanwhile, given the need for dry sanitation technologies, toilets based on the production of enriched Terra Preta soil have potential applications in urban and rural agriculture and warrant further investigation.

Effect of ageing on the physicochemical properties of human faeces in the context of onsite sanitation.

Sanitation systems involving onsite storage of faecal matter cause excreta to undergo transformation and primary treatment in-situ. However, little is known about the transformation pathway followed by fresh faeces while contained in situ. The current paper investigated this transformation under ambient conditions during a 16-week in-situ-storage period. Moisture content, drying kinetics, rheological, physicochemical, and thermal properties were analysed to determine the effects of ageing. The faeces experienced dehydration, mainly affecting moisture-dependent characteristics. Moisture content decreased from 79%wt to 26%wt, and water activity of 0.67, which corresponds mainly to the removal of interstitial bound water, reducing mass by 72%. The decreasing moisture content expectantly reduced drying ability, flowability and thermal properties (heat capacity and thermal conductivity). During this period, negligible biodegradation was recorded (volatile solids reduced by 3%), resulting in consistent chemical oxygen demand, particle size, carbon content and calorific values. Ammonium and nitrates decreased, but total nitrogen remained unchanged. Therefore, ageing affects nitrogen chemical forms and not nutrient composition. The findings demonstrate the benefits of source separation and in particular ventilated storage as a passive way to pre-treat and recover resources from faecal material.

A critical review of experimental and predicted methane generation from anaerobic codigestion.

Anaerobic digestion is increasingly being considered as a treatment option for an extensive range of waste biomass, due to the potential for energy recovery, in the form of methane production, and lower sludge volumes relative to aerobic treatment processes. Furthermore, when two substrates are codigested (i.e. digested together), added benefits are foreseeable, such as increased methane production and detoxification of toxic compounds via cometabolic degradation pathways. The objectives of this study were to compare experimental and predicted methane production from codigestion literature studies in order to objectively evaluate digester performance. Two predictive methods were used, both assuming methane yields are additive: literature values for digestion of single substrates and a stoichiometric method using model substrates to represent different substrates. Waste sources included in the analysis were primary sewage sludge, waste activated sludge, cow manure, waste paper, grease trap sludge, fat oil and grease and algal sludge. It was found that methane production could approximately be predicted using both methods, with literature methane yields from the same study being the most accurate predictor. One important finding from this study was that the assumption that methane yields are additive is a reasonable one. Furthermore, both predictive methods may be usefully employed as a screening tool to compare methane yields between different types and blends of substrates.

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.

Moistube irrigation fouling due to anaerobic filtered effluent (AF) and horizontal flow constructed wetland (HFCW) effluent.

The study assessed the suitability of two effluent types, namely anaerobic filtered (AF) and horizontal flow constructed wetland (HFCW) effluent for Moistube irrigation (MTI). Secondary to this, the study determined the plugging coefficients (α) on MTI for the respective effluents. The feed water was supplied from a raised tank (3.5 m), and mass-flow rates were recorded at 15 min intervals using an electronic balance. The effluent feed water concentrations and experimental room temperature (25 °C ± 1 °C) were continuously monitored and kept constant. Hermia's models based on the [Formula: see text] coefficient was used to select the best fitting fouling mechanism model and, consequently, the plugging coefficients. In addition, microbial colony analysis and scanning electron microscopy (SEM) analysis was carried out to assess the composition of the deposited sediment (DS) and adhered bacterial film (ABF) onto the MTI lateral. The study revealed that MTI pore blocking was a complex phenomenon described by complete pore-blocking model ([Formula: see text] ≥ 0.50). Discharge followed an exponential decay with early fouling observed on AF effluent because of a high concentration of total suspended solids (TSS) and dissolved organic matter (DOM). Discharge declined by 50% after 20 and 10 h of intermittent operation for AF and HFCW effluent, respectively. The α for each effluent (foulant) were [Formula: see text] = 0.07 and [Formula: see text] = 0.05, respectively, for AF and HFCW. The microbial analysis revealed bacterial aggregation structures that contributed to pore blocking. SEM imaging revealed complete surface coverage by deposited sediment. It is concluded that water quality determines the operation life span of MTI, and the two effluents promote accelerated MTI pore fouling or blocking. Continuous use without flushing the MTI will promote membrane degradation and reduced discharge efficiency. Additional filtration can potentially mitigate the membrane degradation process.

Effect of drying on the physical and chemical properties of faecal sludge for its reuse.

This work explores the effect of drying on the chemical and physical properties of faecal sludge, and evaluates the reuse potential of the dried material. For the purpose of this study, the nutrient content, calorific value and thermal properties were determined for faecal sludge samples dried at different moisture contents and under different drying and operating conditions. The results show that drying does not affect the nutrient content and calorific value, but it induces modifications of the chemical form of nitrogen and the thermal properties. The dried product was demonstrated to be suitable for reuse as an agricultural product and biofuel. In agriculture, dried faecal sludge could be used as an organic fertilizer with a particularly high phosphorous content and a slow release of nitrogen and phosphorous. As a biofuel, dried faecal sludge would have similar characteristics as wood.

The effect of moisture content and alkalinity on the anaerobic biodegradation of pit latrine sludge.

This study investigated the effect of additional moisture and/or alkalinity on the rate of anaerobic digestion in samples of material obtained from pit latrines. In modified serum bottle tests it was shown that poor gas production rates were observed from all experiments with material collected at the lower part of one pit. Using material from the top layer of a second pit it was shown that experimental bottles produced significant amounts of gas for all treatments. Analysis of data indicated that treatment with additional alkalinity had no discernible effect on anaerobic gas production rates, but that there was some correlation between moisture content and gas production rate. These results did not support the hypothesis that low pH buffering capacity was a limiting factor in the rate of digestion of pit latrine sludge, but confirmed that low moisture content could reduce the rate of stabilisation. This implies that increasing the moisture content in a pit latrine has the potential to increase biological stabilisation rates in the pit when the material is not already well-stabilised.

The effect of moisture content and alkalinity on the anaerobic biodegradation of VIP contents.

This study investigated the effect of additional moisture and/or alkalinity on the rate of anaerobic digestion in samples of material obtained from pit latrines. In modified serum bottle tests it was shown that poor gas production rates were observed from all experiments with material collected at the lower part of one pit. Using material from the top layer of a second pit it was shown that experimental bottles produced significant amounts of gas with both the addition of water and the addition of alkalinity. The results supports the motivating hypotheses that moisture content and pH buffering capacity obtained in VIP material are low and may be limiting factors in the rate of stabilisation that may occur in these pits. This implies that increasing the moisture content and alkalinity in the pit has the potential to increase stabilisation rate in the pit when the material is not already well-stabilised.

'LaDePa' process for the drying and pasteurization of faecal sludge from VIP latrines using infrared radiation.

This paper studies a faecal sludge treatment process, LaDePa (Latrine Dehydration and Pasteurization), which includes: (i) the characterization of the rheological and plastic behaviour of faecal sludge in the feeding section; (ii) the study of the drying and pasteurization performance of the process using a laboratory-scale prototype; and (iii) an evaluation of the processed faecal sludge for reuse in agriculture or as a biofuel. Experiments conducted using a rheometer show that the faecal sludge exhibits shear thinning behaviour, i.e. viscosity decrease with shear rate increase. Plasticity tests in a cone penetrometer showed that the faecal sludge has a more liquid than plastic behaviour, which may affect extrusion quality, unless a plasticizer is added, as sawdust in this study. The extent of drying and pasteurization of the samples was determined based on moisture content and the presence of viable Ascaris eggs respectively. As the intensity of infrared radiation was increased, drying was faster and more efficient in terms of energy consumption. However, the pellets were thermally degraded at temperatures above 200 °C. After processing in the LaDePa, Ascaris eggs were deactivated or severely damaged so that they would be not able to develop. The last part of the study was conducted by determining the content of nutrients (C, N, P, K) and calorific value. The results showed that the processed pellets have suitable characteristics for reuse in agriculture and as a biofuel: similar nutrient content to manure and compost, and similar calorific value to wood. Drying did not affect the nutrient content and calorific value of the dry bone of faecal sludge.

West Indian punctate keratopathy in a Caucasian.

We present a patient with the picture of corneal white spots, very similar in morphology to those described in native West Indians, occurring here in a Caucasian. Their aetiology remains obscure.

Intraocular melanoma, diabetes, and Turner's syndrome: presentation with proptosis.

A patient with Turner's syndrome and untreated diabetes mellitus presented with a blind, painful, glaucomatous eye and progressive unilateral proptosis. Although a computerised tomographic scan failed to show evidence of a retroocular extension of the presumed choroidal melanoma, the clinical features were so suggestive of extraocular extension that an orbital exenteration was considered. Examination of the enucleated eye for histological conformation of the presence of malignant melanoma showed no extraocular extension, and histology of the retroocular connective tissue revealed only haemorrhage and fibroblastic activity. There are 3 other reported cases of malignant melanoma presenting as proptosis without extraocular extension, so that extreme caution is required when exenteration is deemed necessary on clinical grounds but where computerised scanning fails to reveal direct tumour spread.

Intergranular corrosion-fatigue failure of cobalt-alloy femoral stems. A failure analysis of two implants.

Two modular hip implants with a cobalt-alloy head and a cobalt-alloy stem were retrieved after a fracture had occurred in the neck region of the femoral component, eighty-five and seventy months after implantation. Both implants failed less than one millimeter distal to the taper junction between the head and the stem (outside of the taper). The fracture surfaces of the implant were investigated with the use of scanning electron microscopy, to determine the nature of the failure process. The fractures occurred at the grain boundaries of the microstructure and appeared to be the result of three factors: porosity at the grain boundaries; intergranular corrosive attack, initiated both at the head-neck taper and at the free surface; and cyclic fatigue-loading of the stem. The corrosive attack of the free surface was initiated, in part, by the egression of surface grains and by the ingression of fluid into the intergranular regions. Sectioned surfaces showed extensive intergranular corrosive attack in the prosthetic neck localized in the region of the head-neck taper junction and penetrating deeply into the microstructure.

Promoting sustainable industry through waste minimisation clubs.

The concept of waste minimisation clubs was developed in the early 1990s to promote the exchange of experiences between geographically close manufacturers in the implementation of waste minimisation measures. It is a successful approach, resulting not only in a reduction in environmental impact, but also significant financial savings for the companies involved. Two pilot waste minimisation clubs were established in the province of kwaZulu Natal in South Africa in 1998 and 1999, to determine if this approach was a feasible method of promoting sustainable industrial development in South Africa. On conclusion of this project in December 2000, the 20 companies that participated in these clubs had saved a total of US$ 1.7 million, and reduced their water use and effluent discharge by over 2,400 Ml/y.

Life cycle assessment of an industrial water recycling plant.

An industrial water recycling plant was recently commissioned in Durban, South Africa. As with any industrial activity there are environmental burdens associated with water recycling. To assess these burdens a relatively new environmental tool--the life cycle assessment (LCA)--was used. LCA is a systematic way to evaluate the environmental impact of a product or process. This study presents the environmental burdens associated with industrial water and identifies the areas for improvement for the processes involved for recycling water. It was shown that the majority of the environmental burdens for producing industrial water could be traced back to the consumption of electricity for the operation of the plant.

The application of pinch analysis to water, reagent and effluent management in a chlor-alkali facility.

South African industry is coming under increasing pressure to reduce the amount of freshwater it uses and the amount of effluent it produces. Water pinch is a cleaner production technique aimed at reducing the freshwater consumption and effluent production within a chemical complex. The design of water-reuse or water pinch networks as applied to the case study of a chlor-alkali complex is considered. Insights are provided into the analysis and formulation of problems for large-scale industrial systems and the application of present techniques and tools to the formulated problem is illustrated. The features of the problem posed by the chlor-alkali facility are discussed and the limitations of the present theory in dealing with this problem highlighted. The concepts of utility-waterpinch analysis and process-water pinch analysis are introduced.

Toxicity and biodegradability of high strength/toxic organic liquid industrial effluents and hazardous landfill leachates.

Industrial effluents and leachates from hazardous landfill sites were tested for toxicity using the anaerobic toxicity assay. This test was done on several industrial effluents (brewery spent grain effluent, a chemical industry effluent, size effluent), and several hazardous landfill leachates giving vastly different toxicity results. The brewery effluent, spent grain effluent and size effluent were found to be less toxic than the chemical effluent and hazardous landfill leachate samples. The chemical industry effluent was found to be most toxic. Leachate samples from the H:h classified hazardous landfill site were found to be less toxic at high concentrations (40% (v/v)) while the H:H hazardous landfill leachate samples were found to be more toxic even at low concentrations of 4% (v/v). The 30 d biochemical methane potential tests revealed that the brewery effluent, organic spent grain effluent and size effluent were 89%, 63%, and 68% biodegradable, respectively. The leachate from Holfontein hazardous landfill site was least biodegradable (19%) while the chemical effluent and Aloes leachate were 29% and 32% biodegradable under anaerobic conditions.