Chemical disinfectants

Safe water, sanitation, and hygiene provision and promotion are critical elements of emergency response to ensure human safety, health, and dignity. Disinfectants, such as chlorine, are widely used in emergency response to treat water for drinking. However, excreta is rarely treated in emergencies; the current focus of response activities is to provide safe, clean, and private sanitation facilities. In this chapter, we provide a summary of knowledge on disinfection of excreta in emergencies and recommendations for future research. In particular, we recommend the need to prioritize disinfection of waste in emergencies to prevent ongoing transmission of disease and to work with responders and beneficiaries to develop appropriate, low-cost, transportable, acceptable, and easy-to-use excreta disinfection solutions. Chemical disinfectants inactivate pathogens by chemically degrading their building blocks or disrupting their metabolism. The efficacy of chemical disinfectants thus depends strongly on their reactivity with biomolecules. In addition, both the disinfectant concentration throughout the treatment, as well as the duration of the disinfection treatment (exposure time) are important parameters determining the disinfection efficiency. To be applicable in the context of sanitation, chemical disinfections must have several basic characteristics: they must be active against a wide range of pathogens; be sufficiently cost-effective to be applied frequently and in large quantities; be reasonably safe to produce, store and apply; and create a final product that is safe to be handled by humans or to be discharged into the environment. This chapter focuses on two groups of chemicals that meet these requirements, namely oxidants (mainly free chlorine) and bases (ammonia and lime). Oxidants are well-studied in the context of drinking water disinfection, though less information is available for the disinfection of sanitation-relevant matrices. Ammonia and lime are treatments that are exclusively used in the context of sanitation. For these chemical disinfectants, we have conducted a literature survey and collected kinetic data on their inactivation efficiencies in sanitation-relevant matrices. We have considered all pathogenic organisms described in part 3 of the GWPP, though data were only available for a subset of these organisms. In addition, we have included indicator organisms typically used to mimic the fate of pathogens during disinfection. The collected data were analyzed and visualized to provide an overview over the disinfection efficiency of chlorine, ammonia and lime toward different pathogen groups or individual organisms. In addition, whenever possible, the data were scrutinized with respect to the effects of important matrix properties, namely temperature, solids content, ammonia and organic matter content. We furthermore aimed to identify the least susceptible, process-limiting pathogens for each treatment, and to suggest suitable indicator organisms. Finally, treatment recommendations are provided, and we highlight major knowledge gaps that need to be addressed in order to refine these recommendations.