A physico-chemical water treatment system for relief agencies

Abstract

Relief agencies that are using surface water sources to supply drinking water to displaced communities and refugees need convenient, reliable and durable treatment systems to alleviate the risk of waterborne disease. Physico-chemical unit processes with terminal disinfection can be the ‘lowest effective technology’ which satisfies rapid response and durability requirements. A physico-chemical water treatment system was developed which has a minimum of power and mechanical plant requirements. The system comprised a pump driving the raw water supply through a spiral pipe flocculator and an upflow clarifier of novel new design fabricated within a standard Oxfam T11 tank. This system was intensively tested and developed in the UK in a joint Department for International Development and Oxfam-funded research and development project. It proved to be reliable and effective when treating raw water with fine colloidal turbidity, consistently providing an effluent with a turbidity of 1–2 nephelometric turbidity units (NTU) with aluminium levels well below the World Health Organisation guideline value. During the research programme an early model of the upflow clarifier was demonstrated in an International Committee of the Red Cross-sponsored Inter-Agency Technical Meeting in Geneva, where it reduced a raw water turbidity of 600 NTU to below 10 NTU, with a measured aluminium residual of only 0·041 mg/l.