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
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
second protocol was the coagulation/flocculation of suspended solids using
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.
|Date of Award||2016|