Batch water treatment consists of the intermittent use of settling tanks for water clarification, and is a common treatment practice during emergency relief efforts. This article presents simple improvements to coagulant dosing and water quality based on experience gained in the aftermath of the 2005 South Asian earthquake.
Alum is widely used in water treatment because of its many advantages, of which its relative low cost and worldwide availability have ensured it to be the coagulant of choice for emergency water treatment. However, in certain circumstances, its use may leave an undesirable coagulant aluminium residual in the finished water. Such residuals can generate (unwarranted) fear over the use of this useful coagulant (particularly among the misinformed). This article is focused on clarifying topics related to aluminium residuals, such as its occurrence, health risks, significance in emergency water treatment, measurement, and control strategies. These issues are discussed in view of the practical constraints faced in the field during emergencies and where appropriate contrasted with conventional (non-emergency) practice. Emergency water treatment sludge disposal and alternative coagulants to alum are also addressed.
As humanitarians we must be deeply concerned about using the most effective solutions for saving lives and reducing morbidity, whilst working within reasonable cost envelopes. In this respect it is critical to place the brightest spotlight upon the practice of using bulk water treatment units (BWTU), as witnessed most recently on a massive scale in the Pakistan floods of 2010. There, as in other huge crises, many BWTUs were deployed by donors and other agencies, sometimes as a knee-jerk reaction to an overwhelming crisis. These appear to offer neat ‘plug and play’ solutions that also happen to be very media friendly. However, some of the BWTUs sent to flood-affected areas of Pakistan in 2010 demonstrate that there is an absence of appropriate selection criteria for BWTUs and the significant limitations on their use are not fully understood. Though the evidence gathered is partial, there is enough to suggest that some agencies are engaging in poor practice.