Low-cost physico-chemical disinfection of human excreta in emergency settings

• Main Author: Emanuele, Sozzi
• Format: Dissertation
• Language: English
• Published: University of Brighton 2016

The operation of a health-care facility, such as a cholera or Ebola treatment centre in an emergency setting, results in the production of pathogen-laden wastewaters that may potentially lead to onward transmission of the disease. The research presented here outlines the results of field and laboratory studies devised to inform the design and operation of a novel full-scale treatment protocol to disinfect pathogen-laden hospital wastewaters in situ, thereby eliminating the need for potentially hazardous road haulage and disposal of human excreta or wastewater to poorly-managed waste facilities. The approach investigated has the potential to provide an effective barrier to disease transmission by means of a novel but simple sanitary intervention. During Phase I of this research, a fieldwork study in Haiti focused on the design and operation, at short notice and within a disaster setting, of a new treatment technology that aimed to obviate the transport of untreated human excreta from emergency cholera treatment centres (CTC) to poorly-managed waste facilities. The results of this fieldwork period were validated and further optimised during Phase II: a detailed laboratory-based study in the UK that assessed the performance of the novel treatment technology in order to improve its efficacy. The performance of two physico-chemical protocols was monitored, first in the field (Port-au-Prince, Haiti), by means of both bench-scale and full-scale batch treatment of real highly-contaminated faecal waste from a cholera treatment centre (Phase I), and subsequently during more detailed laboratory studies (Phase II) using a ‘faecal-waste matrix’ that was created by mixing various municipal wastewaters and sludges in a proportion that aimed to mimic the composition of wastewaters produced at health-care facilities in emergency settings. The two investigated protocols achieved coagulation/flocculation and disinfection by exposure to high– or low–pH environments, using thermotolerant coliforms, intestinal enterococci, and somatic coliphages as indices of disinfection efficacy, and several physico-chemical parameters as indicators of treatment performance. In the high–pH treatment protocol, the addition of hydrated lime resulted in wastewater disinfection and coagulation/flocculation of suspended solids. In the low-pH treatment, disinfection (and partial colloidal destabilization followed by sedimentation) was achieved by the addition of hydrochloric acid, followed by pH neutralisation. A potential further step in this 4 second protocol was the coagulation/flocculation of suspended solids using aluminium sulphate. During Phase II, removal rates achieved for the high pH treatment protocol, in terms of physico-chemical parameters, were: COD > 80%; suspended solids > 85%; turbidity > 85%. Removal rates in terms of microbiological parameters were: thermotolerant coliforms > 5 Log10, intestinal enterococci >2 Log10 and somatic coliphage > 2 Log10. Removal rates achieved for the low-pH treatment protocol in terms of physico-chemical and microbiological parameters were: COD > 80%; thermotolerant coliforms between 0.2 and 1.2 Log10, with a mean removal of 0.75 Log10 and > 3 Log10 removal for intestinal enterococci. The removal of somatic coliphage was in excess of 4 Log10. The quantity and density of the sedimented sludge and several other physicochemical parameters (such as total nitrogen, total phosphorous, ammonia and ammonium, etc.) for the analysis of the supernatant were also monitored. This study represented the first known successful attempt to disinfect wastewater in a disease outbreak setting without resorting to the alternative, untested, approach of ‘super-chlorination’ which, it has been suggested, may not consistently achieve adequate disinfection. In addition, a basic costs analysis demonstrated significant savings in the use of reagent compared with super-chlorination. The approach to sanitation for cholera treatment centres and other disease outbreak settings presented here offers a timely response to a UN call for in situ disinfection of wastewaters generated in such emergencies. Further applications of the method to other emergency settings have been actively explored in discussion with the World Health Organization (WHO) in response to the ongoing Ebola outbreak in West Africa, and with the UK-based non-governmental organization (NGO) Oxfam.