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The water and sanitation needs of the poor in developing countries are huge. To meet the target of water and sanitation for all by the end of 2025, some 2.9 billion people will have to receive improved water supplies, and 4.2 billion improved sanitation. The technologies used must be appropriate and, in particular, simple, affordable and sustainable.
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The effect of phosphate addition in drinking water was tested under static conditions as batch tests and under dynamic conditions using continuously fed reactors. Phosphate supplements in batch tests from 0.1 to 2 mg P-PO4 L(-1) did not show any relationship between bacterial growth and phosphate concentration. Dynamic tests in slightly corroded reactor (stainless steel) treated at 1 mg P-PO4 L(-1) showed only a moderate improvement in the growth of microorganisms. On the contrary, phosphate treatment applied to the highly corroded reactor (unlined cast iron) led to an immediate, drastic drop in iron oxide release and bacterial production. Phosphate uptake by the reactor wall was less than 14% with the stainless-steel reactor and 70-90% with the corroded cast iron reactor. Moreover, about 5% of the phosphate associated to corroded iron pipe walls was released for 20 days after the end of treatment.
Corrosion scales play an important role in modifying water quality in drinking water distribution systems. The corrosion scales from old iron/steel pipes were analyzed for their structure and composition. Scales were studied both before and after drying. and goethite, magnetite and lepidocrocite were identified as the primary constituents of the dried samples. High concentrations of readily soluble ferrous phases were detected in wet-scale samples. The corrosion scales had a shell-like, enveloping layer, covering porous deposits of iron oxide phases. Our studies were able to identify important differences between corrosion scales found in two different water distribution systems. Further studies are needed to establish the role of corrosion scales in the mechanism of iron release from corroded pipes.
The effect of direct exposure to solar radiation on the migration of vinyl chloride monomer (VCM) from unplasticized polyvinyl chloride (uPVC) pipes was investigated using locally manufactured and imported pipes. Specimens 33 cm long were used throughout the research. The investigation was carried out, at different times of exposure, by exposing one part of the specimens to the direct sunlight, while keeping the other part in the shade. The VCM concentration in the water was evaluated using the gas chromatography (GC)/head-space technique. A VCM concentration of 2.5 microg/l was detected after 30 days of exposure in direct sunlight. The original initial VCM concentration in the uPVC was predicted, and the diffusion rate of VCM from uPVC pipes was expressed as a function of time.
Little is known about how the growth of halogenated disinfection by-products (DBPs) in drinking water is affected by time spent in a distribution system. Experiments were performed to compare the rate of trihalomethane and haloacetic acid production in a simulated pipe environment to that observed for the same water held in glass bottles. Results showed that although the rate of chlorine consumption in the pipe was much greater than in the bottle, there was no decrease in the amount of haloacetic acids produced and that trihalomethane levels actually increased by an average of 15%. Separate tests confirmed that this increase was due to a reservoir of organic precursor material associated with deposits on the pipe wall. This work suggests that the rate of DBP production in a distribution system will not necessarily be reduced by increased chlorine consumption due to non-DBP producing reactions with deposits on the pipe wall.
Surface water storage for the drinking water supply can be used for different purposes. 1. To bridge periods, in which no or not enough water can be withdrawn from the river (periods of low flow). 2. To bridge periods in which direct use of surface water is impossible because of: * a calamity in the upstream area * the concentration of certain polluting substances in the surface water is higher than the norms or acceptable levels (for instance in periods of low flow). 3. As a first step in the treatment process, quality improvement can be achieved by * levelling the concentration of non degradable substances * lowering the level of degradable substances. The reduction can often be approximated with degradation models of zero or first order. * selective intake. The design of the reservoirs must be such that the object(s) in view are achieved as good as possible. The installation and management must take care to prevent quality deterioration and if possible to contribute to an improved quality of the final drinking water.
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BACKGROUND: Inadequate water and sanitation adversely affect the health of children in developing countries. We aimed to assess the effects of water and sanitation on childhood health in a birth cohort of Peruvian children. METHODS: We followed up children once a day for diarrhoea and once a month for anthropometry, and obtained data for household water and sanitation at baseline. FINDINGS: At 24 months of age, children with the worst conditions for water source, water storage, and sanitation were 1.0 cm (95% CI 0.1-0.8) shorter and had 54% (-1 to 240) more diarrhoeal episodes than did those with the best conditions. Children from households with small storage containers had 28% (1-63) more diarrhoeal episodes than did children from households with large containers. Lack of adequate sewage disposal explained a height deficit of 0.9 cm (0.2-1.7) at 24 months of age. Better water source alone did not accomplish full health benefits. In 24-month-old children from households with a water connection, those in households without adequate sewage disposal and with small storage containers were 1.8 cm (0.1-3.6) shorter than children in households with sewage and with large storage containers. INTERPRETATION: Our findings show that nutritional status is a useful endpoint for water and sanitation interventions and underscores the need to improve sanitation in developing countries. Improved and more reliable water sources should discourage water storage at risk of becoming contaminated, decrease diarrhoeal incidence, and improve linear growth in children.
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