As one article in a four-part PLoS Medicine series on water and sanitation, Paul Hunter and colleagues argue that much more effort is needed to improve access to safe and sustainable water supplies.

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Water Supply and Health

Dissolved effluent organic matter: Characteristics and potential implications in wastewater treatment and reuse applications.

State of the art of produced water treatment.

Dissolved air flotation and me.

A review on the applicability of integrated/hybrid membrane processes in water treatment and desalination plants

Seawater pretreatment for reverse osmosis: chemistry, contaminants, and coagulation.

An end-use model for residential water demand and return flow is presented in this paper. The model requires a unique description of a single residential stand in terms of all its end-uses. The end-uses include toilet flushing, bathing and showering, garden watering, pool water use, leaks, et cetera. Various parameters describe each of the end-uses. The model predicts five components relating to water use and wastewater flow at a residence: indoor water demand, outdoor water demand, hot water demand, wastewater flow volume and concentration of total dissolved solids in the wastewater. The large number of input parameters in an end-use model allow for powerful and detailed analysis of water demand. The various parameters required to populate the model are discussed, guideline values are presented and possible methods for calibration of the model to measured results are proposed. The model calculates 12 monthly results, for each of the five components, to provide a typical seasonal pattern as well as an annual value. WaterSA Vol.30 (3) 2004: 293-304

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Structure and data requirements of an end-use model for residential water demand and return flow

Water and sanitation services provide a cost-effective solution for alleviating the impact of water-borne diseases. Actually, for water supply projects a top-down approach is followed, giving priority to deliver sufficient quantities of water, increasing its availability by investment in new systems. Little attention is paid to the functioning of these systems on the long-term, and its maintenance and operational constraints. In this paper, a methodology was developed to technically assess water supply systems based on four criteria, namely availability, capacity, continuity and condition. The practicality of the approach is demonstrated by a technical assessment of a number of water supply systems in the Vhembe District in South Africa. The systems consist of piped distribution systems with public standpipes, mostly fed by groundwater. In general, it can be concluded that the performance of the systems, although relatively new, is poor. The availability (criterion 1) of the drinking water is a problem due to poorly constructed boreholes or disagreement on the payment of the operational cost after construction. In most villages the capacity (criterion 2) of the installed infrastructure is sufficient, although storage volume is in some villages too small. The continuity (criterion 3) of the water supply is threatened by disputes about payment of diesel for the pump and maintenance and repair of the pump. Finally, the condition (criterion 4) is poor mostly due to taps at the standpipes which are damaged and require frequent replacement. Despite the simplicity of the proposed assessment methodology, it provides rapid insight in the state of a system and is ideal for bench marking the performance of different systems in different regions. Furthermore, the quantitative measures of the four different criteria allow system operators and planners to rapidly pinpoint the reasons for poor performance and to take the appropriate corrective action. The used weighting factors in this demonstration are arbitrary – different users could adapt them to their own specific situations without invalidating the overall approach to technical assessment suggested in this paper.

A tool for technical assessment of rural water supply systems in South Africa

A biosand filtration (BSF) unit is an intermittently operated slow sand filter designed for household use. This paper reviews the practical application of B S F , identifies the important design considerations and proposes a systematic design procedure. The media properties, water requirements, filter cycle time and water temperature are identified as the most important design input parameters. The resultant specifications are the water dosage volume, water production rate and media bed dimensions. We propose two parameters for characterising the filtration rate, namely the initial and average clean bed filtration rate. Mathematical expressions for these two parameters and the filtration time are derived. Guideline values for the filtration rate and the ratio of the pore volume to the water dosage volume are established and used as design checks. It is noted that the filtration rate is determined solely by the properties of the water temperature and the media—customary constraints posed by the bed area and the bed depth had been eliminated. Therefore the heart of BSF design lies in the careful and appropriate selection of the filter media. The design procedure proposed is illustrated with an example for a typical rural household in Venda, South Africa.

Rational design of domestic biosand filters

The structure and data requirements of an end-use model for residential water demand and return flow are presented in a companion paper. This paper focuses on the practical application of the model. The model is first applied to confirm a few commonly observed water demand patterns: Seasonal variation in demand, the positive correlation between average annual daily water demand and stand size, and the increase in water demand, hot water demand and wastewater flow with an increase in household size. The convergence between the predicted model results and independently observed values by others encourages practical use of the model. Secondly, the effects of some specific water demand management measures are evaluated by adjusting selected model parameters. The measures include xeriscaping, the installation of dual-flush toilets and low-flow showerheads, pool ownership and pool cover use. The model provides a rapid means to obtain first estimates of the likely effects of different water demand management measures.

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Johannes Haarhoff

Papers

Seawater pretreatment for reverse osmosis: chemistry, contaminants, and coagulation.

Structure and data requirements of an end-use model for residential water demand and return flow

A tool for technical assessment of rural water supply systems in South Africa

Rational design of domestic biosand filters

Application of a residential end-use model for estimating cold and hot water demand, wastewater flow and salinity