5.6 Adequacy in emergency settings

The decision to install a disinfection technology depends mainly on quality requirements for desired end-use and/or national standards. Other factors to consider are effluent characteristics, budget, availability of materials, and operation and maintenance capacity. Disinfection can only be applied effectively after a functioning secondary or tertiary treatment. Pathogens tend to be masked by suspended solids in unfiltered secondary effluent. As disinfection by-products can form, chlorine should not be used if water contains significant amounts of organic matter.  

An important consideration is the accessibility of the required material to establish a disinfection treatment. Materials such as chlorine, UV lamps, and filter materials such as activated carbon may be challenging to access. Accessing chlorine may also be a sensitive matter as it can be used for the construction of chemical weapons.  

Tertiary filtration processes like Slow Sand Filters (SSF) have the potential to substitute for or render chlorination unnecessary when operating effectively. However, in high population density areas or locations experiencing elevated water-related morbidity, it is advisable to combine slow sand filtration with chlorination. To prevent any interference with the treatment performance of the SSF, chlorination is recommended to occur after the water has passed through the sand filter. This strategic combination ensures comprehensive water treatment and addresses specific challenges associated with varying population densities.

SSFs need several weeks to mature and develop the biofilm on top of the filter, which is essential for treatment efficiency. Therefore, SSFs are not considered suitable for the acute response phase of emergency but for the stabilisation and recovery phases.