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S Y S T E M A T I C R E V I E W Open Access
Drainage systems, an occluded source of
sanitation related outbreaks
Background: Drainage systems and its role in sanitation related outbreaks are evident but still occluded once it has
been installed. This current review evaluates if drainage systems can cause infections and thus be of clinical concern.
Method: A review of the literature was analyzed. Papers, guidelines, and quality management systems have been
Results: Adequate sanitation is fundamental and a prerequisite for safe life and productivity. In contrast,
malfunctioning sanitation has been reported to cause outbreaks all over the world. In areas with no sanitation,
diarrheal mortality is high and has been shown to decrease by 36% after interventions to improve sanitation. Often,
infections are faeces associated and when present in wastewater and sewage sludge poses a high risk of infection
upon exposure. Hence, there are working safety guidelines and in industries where infection reduction is essential
strict quality assurance systems, i.e. HACCP (hazard analysis critical control points) and GMP (Good Manufacturing Practice)
must be complied. Healthcare has recently taken interest in the HACCP system in their efforts to reduce healthcare
associated infections as a response to increasing number of ineffective antibiotics and the threat of mortality rate like the
pre-antibiotic era. The last few years have called for immediate action to contain the emergence of increasing resistant
microorganisms. Resistance is obtained as a result of overuse and misuse of antibiotics in both healthcare and agriculture.
Also, by the discharge of antibiotics from manufacturers, healthcare and society. One mechanism of development of
novel resistant pathogens has been shown to be by effortless sharing of genetic mobile elements coding for resistance
from microbes in the environment to human microbes. These pathogens have been sampled from the drainage systems.
These were noticed owing to their possession of an unusual antibiotic resistance profile linking them to the outbreak.
Often the cause of sanitation related outbreaks is due to inadequate sanitation and maintenance. However, in general
these infections probably go unnoticed.
Conclusion: Drainage systems and its maintenance, if neglected, could pose a threat in both community and healthcare
causing infections as well as emergence of multi-resistant bacteria that could cause unpredictable clinical manifestations.
Keywords: Sanitation, Drains, Outbreaks, Infections, Resistance, Pathogens
Sanitation is defined by the World Health Organization
(WHO) as: “Sanitation generally refers to the provision of
facilities and services for the safe disposal of human
urine and faeces. Inadequate sanitation is a major cause
of disease world-wide and improving sanitation is known
to have a significant beneficial impact on health both in
households and across communities. The word ‘sanitation’
also refers to the maintenance of hygienic conditions,
through services such as garbage collection and wastewater
Sanitation is in general inadequate in rural areas and
in developing countries [1,2] while regarded as safe in
the developed countries in the community as well as in
healthcare. However, it is not sufficient to have access to
water and modern drainage systems unless adequate
sanitation is maintained. Quality assurance maintenance
work is implemented in pharmaceutical and food industry
in order to reduce the risk of exposure to the hazards
(e.g. pathogens causing clinical manifestations) in the
disposals. However, in the community or in healthcare,
Medibiome AB, 431 53 Mölndal, Sweden
ARCHIVES OF PUBLIC HEALT
© 2015 Blom.; licensee BioMed Central. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution , and
reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain
Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article,
unless otherwise stated.
Blom Archives of Public Health (2015) 73:8
sanitation is not prioritized and often forgotten , despite
that wastewater disposal contains increased level of
human microbes and that there are several reports
implicating drains as a source of infection (Table 1).
For instance, in the community the severe acute respiratory
syndrome (SARS) outbreak in 2003 at Amoy Garden was
reported by WHO to likely have been caused by faulty
plumbing due to lack of maintenance causing dry out traps
 and in healthcare, Starlander and Melhus re-
ported in 2012 of a minor outbreak of extended
spectrum β-lactamase (ESBL) producing Klebsiella
pneumoniae due to contaminated sink drains . Indeed,
drains are implicated as being a source of microbes
causing infection both in community and healthcare
[6,7]. Breathnach et al. further pointed out that proper
design and maintenance of the wastewater system are
essential to prevent infections at intensive care units
(ICU) . However, its impact on infection rates has not
yet been fully elucidated.
In the current paper, different aspects supporting the
role of drainage systems and sanitation to cause infections
and emergence of resistance are delineated. Aspects
considered are from past and recent outbreaks, from
developing and developed countries, and also, the ways to
prevent spread of bacteria in the working environment, at
wastewater treatment plants, and food industry. Presented
data will hopefully contribute to a better understanding of
the importance of proper sanitation and its maintenance
to prevent infections.
1907 using key words such as sanitation, infection, trans-
mission, drains, sinks, outbreaks, drainage systems, sewage,
wastewater treatment plants, bacteria, virus, resistance,
antibiotics, biofilm, infection prevention, and health care
associated infections. The fact that contamination on
surfaces, transmission of pathogens, and infections must be
prevented not only in health care but also in industry and
in the community led to that experiences from these
disciplines were explored if useful also to health care.
Internet was searched to find news from community
cases and guidelines on what conditions and requirements
that e.g. food industry must comply with as well as workers
at risk of exposure to sewage. Guidance documents were
found at the databases of e.g. World Health Organization,
Health and Safety Executive (UK), Centers for Disease
Control and Prevention (CDC), Atlanta, GA and quality
management systems were found by searching God
Manufacturing Practice and hazard analysis critical
control points (HACCP). Also, regulations from authorities
such as Environmental Protection Agency were considered
Table 1 Reports implicating drains as the source of outbreaks
Microorganism Reservoir Location References
SARS Dry U-traps Community, Amoy Garden, Hong Kong WHO 
Multidrug resistant Pseudomonas aeruginosa Faulty drains Hospital-wide and medical unit, England Breathnach et al.
Carbapenem resistant Enterobacteriaceae Sink drains ICU, Melbourne, Australia Kotsanas et al. 
Several different fungi Drains in bathrooms
Drains in kitchen sinks
Community, Osaka, Japan Hamada et al. 
Pseudomonas aeruginosa Sink drains Whirlpool drains ICU at Burn hospital, Cincinnati, OH Edmonds et al.
Pseudomonas aeruginosa Sink drains Medical-Surgical ICU, Chicago, IL Levin et al. 
Pseudomonas aeruginosa Toilets Out patients, Tübingen, Germany Döring et al. 
Fusarium spp. Plumbing drains 131 buildings from 8 states, US Short et al. 
Sink drains Cardiac-Surgical ICU, France Kac et al.
Pseudomonas aeruginosa Sink drains Hematology unit, Lund, Sweden Dagens Nyheter 
ESBL Klebsiella pneumoniae Sink drains Neurosurgical ICU, Uppsala, Sweden Starlander et al.
Klebsiella pneumonia Carbapenem resistant Sink drains ICU, Sørlandet, Norway Tofteland et al. 
Pseudomonas aeruginosa Drains ICU, Edinburgh, UK Gillespie et al. 
ESBL Enterobacteriaceae Sink drains ICU, Tours, France Roux et al. 
Carbapenem-resistant P. aeruginosa Unsealed drain Urology ward, Barcelona, Spain Peña et al. 
P. aeruginosa with unusual antibiogram Drains Neurosurgery ICU, Clichy, France Bert et al. 
ESBL Klebsiella oxytoca Sink drains Hospital, Toronto, Canada Lowe et al. 
Foot Mouth Disease virus Leaking drains Community, Pirbright, UK HSE 
P. aeruginosa Grooved drainage design Haemotology, Singapore Ling and How 
Carbapenem resistant Klebsiella oxytoca Drainpipes, traps ICU, Spain Vergeres -Lopez et al. 
Blom Archives of Public Health (2015) 73:8 Page 2 of 8
to be relevant to assess the risk to be exposed to sewage.
The search outcome, 71 references, is summarized in this
review and describes aspects that support the finding that
drainage systems if not properly installed or designed and
maintained shall be considered as hazardous that may
cause infections and emergence of pathogens armed with
additional resistance and virulence as well as other diseases
e.g. allergies against mold.
Results and discussion
Wastewater as a source of infection
In particular developing countries and to some extent also
developed countries, rural areas predominantly, sanitation
is inadequate resulting in diseases such as infections . It
is estimated that there are over 4 billion diarrheal cases
per year resulting in 2.2 million deaths . The major
cause is exposure to excreta and wastewater where Vibrio
cholerae and Salmonella typhi are notable causes of diar-
rheal diseases [25,26]. Interventions focusing on sanitation
has shown to reduce the percentage in diarrheal morbidity
with 36% . Other benefits with improved sanitation
are economic and environmental gains . In numbers,
the return of investment is huge. Every US$1 invested on
sanitation brings a $5.50 return by keeping people healthy
and productive. In comparison, poor sanitation, costs
countries between 0.5 and 7.2% of their gross domestic
product (GDP) . The potential savings and need for
better quality in life has resulted in e.g. the UN-Water
wastewater task force involving different stakeholders
working to improve sanitation .
Working environment at wastewater treatment plants
In excreta disposal there is a high load of microorgan-
isms such as viruses, bacteria, fungi, and protozoa that
could cause infections [30,31]. Based on the study of
Korzeniewska and Harnisz, the load of enteric bacteria is
probably underestimated due to insufficient detection
methods . Furthermore, it has been shown that both
air and water are contaminated by bacteria in the sewage
at Wastewater Treatment Plants (WWTP) jeopardizing
the health of both plant workers and surrounding
population . Clearly human excreta must be managed
in a safe way to minimize the risk of exposure to microbes
of clinical significance. This condition is further realized
in regulations and guidance documents by e.g. the Centers
for Disease Control and Prevention (CDC), Health Safety
Executive (HSE) in UK, and Environmental Protection
Agencies (EPA) to assure safe working environment for
workers exposed to excreta disposal [33-35]. Sadly, despite
abolition of manual scavenging in India, about 1.2 million
scavengers work as sanitary workers and face numerous
health hazards among them infections .
In food industry, food safety is essential and regulated.
Regulations have been spawn from risk impact assessments
(RIA) and cost-benefit analysis . The production is run
applying two different systems, hazard analysis critical con-
trol points (HACCP) and Good Manufacturing Practice
(GMP) intended to assure the safety of food. A major focus
is on the reduction of microbes. Noteworthy, is the
architectural demands of GMP. GMP focus on e.g. that the
facilities must be built and the work must be done so that
the risk of contamination is minimized and the quality of
the product can be assured. In practice, sinks must be
placed strategically to ease the drainage of water during
cleaning, and in clean rooms or sterile rooms with the
highest clean air requirements, sinks or floor drains are not
allowed. Pipes must be made of certain materials and their
dimensions must differ from those drainage design
requirements in ordinary buildings. Floor drains should be
kept to a minimum and must be free from debris, giving
off no offensive odors. In addition, all building drains must
be cleaned and sanitized on a regular basis. Their design
must prevent the possibility of backflow. Open channels
should be easy to clean and disinfect. These drains must
always be filled with water as a physical barrier and their
covers must remain intact. Maintenance must be recorded
and continuously monitored. Furthermore, it is essential
and mandatory to continuously monitor and include
environmental sampling. In the food industry, it has been
suggested that if one organism is found in the preparation
environment, then there is a 70% chance of it getting into
the food (Chris Griffith at IAFP Rome 2007). If this
principle holds, then the risk of cross-contamination from
the building’s drainage systems to other surfaces and/or
individuals at hospitals is indeed high. However, GMP
systems are not applied in healthcare. Although, HACCP
has been evaluated for its applicability to reduce infections
but only a handful studies have been found . Thus,
practices or maintenance programs considering the
Wastewater as a source of emerging novel pathogens
Sewage sludge can end up on landfills but this is problem-
atic since the leakages from the landfill may reach the
groundwater . WWTP then offer better management
of the sewage since it has to go through different
stabilization treatments in order to produce safe sewage
sludge . However, WWTPs are focusing mainly on sta-
bilizing organic residues and heavy metals while microbes
are neglected. Sewage sludge commonly contains high
load of microbes that are able to infect both humans and
animals but currently ways of accurate detection and
treatment are lacking [32,41]. Detection with conventional
plate count technique is most likely not working since
bacteria can exist in viable but non-culturable stage and
Blom Archives of Public Health (2015) 73:8 Page 3 of 8
hence the load will be underestimated . These reser-
voirs of microbes could then go undetected and be spread
to the environment and infect crops, animals, and humans
. Yet another spread from the environment to the
microbiome can be genetic information coding for resist-
ance and virulence [44-46]. This mode of genetic transfer
is most likely to have occurred in the case of the rise of
the German isolate of Escherichia coli (E. coli) that was
found to have two different mechanisms of virulence .
This isolate belonged to enteroaggregative E. coli (EAEC)
carrying virulence factors on a plasmid (a mobile genetic
material) and it obtained the shiga toxin gene carried on a
phage (a mobile genetic element) from a shiga toxin
producing E. coli (STEC). It caused unpredictable novel
clinical manifestations in a severe outbreak in Germany
2011 with nearly 7,000 reported cases and 18 deaths due
to gastroenteritis and 35 deaths due to hemolytic uremic
syndrome . The ease by that bacteria can share genetic
information on mobile elements and the knowledge that
genes coding for resistance is coded by mobile genetic
elements probably will present further unwanted surprises
. The fear of creation of multi-resistant bacteria is
enforced by the fact that antibiotics are discharged from
manufacturers and hospitals and will stress the bacteria in
the sewage or environment to develop and disseminate
resistance [46,49,50]. Evidence was presented at the 51st
Interscience Conference on Antimicrobial Agents and
Chemotherapy that hospital sewage is breeding ground
for genetic exchange of resistance between bacteria in the
environment and clinical isolates . Furthermore, it was
recently proven that resistance cassettes against five
classes of antibiotics (β-lactams, aminoglycosides, ampheni-
cols, sulfonamides, and tetracyclines) had a perfect genetic
match in a clinical relevant bacteria and an environmental
bacteria . This study explained the mechanism of lateral
spread but also how antibiotic resistance disseminate and
can have clinical implications. In the era of increased anti-
biotic resistance and less available effective therapies, it is
increasingly difficult to treat infections. Still with effective
antibiotics, infections remain a primary cause of morbidity
and mortality in the developed world . Predictions say
that unless immediate and consorted actions are taken we
will face mortality rate like the pre-antibiotic era. In relation
to this dark prediction, the WHO has stated that:
“Antibiotic resistance is one of the greatest threats to
global health security extending far beyond the human
health sector”. The future looks dark also in respect to the
possibility of finding the substance that will kill and not
provoke resistance . Therefore the return of in-
vestment to develop novel antibiotics is judged not
worth the effort, hence few drugs are in the pipeline
[54,55]. Instead, focus has been directed to preventive
measurements. Infection prevention programs have
been enforced by the World Health Organization
(WHO), European Commission and the US, and national
Drains as source of infection
The clinical impact of drains as reservoirs of microor-
ganisms has not yet been fully explored although it is
widely established that human excretions such as faeces,
urine, oral-nasal aerosols, and skin flakes will carry
microbial burden consisting of bacteria and/or virus. For
instance, there are 120 different viruses in human faeces
. It is also reported that patient flora can be detected
in sinks and building drains [10,12,60]. In a new long-
stay hospital, it was discovered that identical strains were
found in the sinks as well as in the admitted patients
. The major correlating strains were pathogens such
as the Escherichia coli, Klebsiella,Pseudomonas and
Acinetobacter species, all being gram-negative bacteria,
with higher correlation to strains isolated from the
throats and intestines of patients. Actually, the major
reservoir of multi-drug resistant Gram-negative bacilli is
the gut of man and animals. At hospitals, discharge of
antibiotics are also high . Clearly, drains are reser-
voirs for microbes and antibiotic residues. It is also clear
that microbes in drains and pipes adheres to the surfaces
of drains and draining pipes as microbial biofilms, creating
a complex ecosystem of different microbes that are fed by
organic and inorganic matters . Hota et al.elegantly
showedthepresenceofPseudomonas aeruginosa (P.
aeruginosa) biofilm in drainage systems and their role
in the propagation of an outbreak . It is also
known that bacteria such as S. aureus promote the
transfer of antibiotic resistance to other bacteria when
present in biofilm . Certainly, drains seem to act
as cradles to the emergence of bacteria armed with
abilities to resist multiple antibiotics. The development of
resistance is probably enhanced at hospitals due to that
more bacteria and more antibiotics are flushed down the
drains due to the very nature of hospitals constantly
caring for numerous different patients that are ill and
treated with antibiotics. Thus, biofilm in building drains,
not properly maintained, have the potential of spreading
even more resistant bacteria. This was indicated in the
extended non-frequent outbreak of Carbapenem resistant
Klebsiella pneumonia (KPC) at an ICU . The source
of transmission was found to be drains that was detected
by molecular profiling to be the only source to harbor
KPC, persistently. Outbreak with P. aeruginosa, revealed
that patients were not colonized on admittance, but ac-
quired a multi-resistant P. aeruginosa during hospitalization
. By running antibiogram and molecular profiling,
drains were found to be the only source. Therefore these
reservoirs are crucial to control. Maintenance of proper
sanitation must then be guarded where seepage and back-
flow never should occur. However, it seems that the
Blom Archives of Public Health (2015) 73:8 Page 4 of 8
management of maintenance is more difficult in practice
than in theory. The difficulty of eradicating antibiotic resist-
ant bacteria from sink drains at an intensive care unit
(ICU) was recently reported . Several different cleaning
methods were tried including hypochlorite, mechanical,
and pressurized steam at a temperature of 170°C. However,
none of these methods worked. This highlights the need for
physical barriers such as water seals for drains that prevent
the exposure to microbes in the drains and a way to control
the integrity of the barrier.
The impact of malfunctioning plumbing
The malfunctioning plumbing was recognized as a prob-
lem already during the cholera outbreak in London by J.
Snow in the 19
century . Later in 1907, it was shown
in a sham study that malfunctioning plumbing created
aerosols with microorganisms that could be transmitted
to humans both indirectly through environmental surfaces
and directly through aerosols and cause disease .
Sham studies, also in present time support earlier findings
and stress the importance of a physical barrier by a water
seal between the drainage systems and surroundings .
The creation of aerosols has been shown to occur when
the plumbing is not correctly designed or if there are
leakages, stops or by dried U-traps. Also, aerosols can be
created upon flushing the toilet or in situations when
water is poured from taps to sinks and drains [66,67]. As
shown in the SARS outbreak at Amoy Gardens, aerosols
can enter the ventilation system and be spread to all the
other connected rooms igniting a fearsome spread .
The outbreak at Amoy Gardens highlights the need for
good maintenance practices and water safety programs
with recommended actions . In the event of backflow
or flooding from the drainage systems of wastewater into
the building, prompt actions must be taken to protect
health and property . Among public health profes-
sionals, it is well known that if wastewater leaks to
structures and furnishing harmful substances such as
gases and pathogenic microorganisms can enter as
well as increased humidity that can promote environ-
mental microorganisms to multiply and cause diseases
and mold-associated allergies . Therefore, it is essen-
tial that the properties are restored to a dry state as
quickly as possible . In recommended guidelines by
EPA in the US, these highlight the increased safety risks
due to the high threat of infection, in the event of sewage
backflow into buildings . Consequences of malfunc-
tioning plumbing can indeed cause outbreaks . In one
outbreak in London, 85 patients became infected during
2005 and 2011, with overall mortality at 40%, but for
patients with sepsis, mortality was 78%. Yet another
outbreak occurred in Southern England with four
cases and no deaths. Both outbreaks were caused by
multidrug-resistant P. aeruginosa. There had been 391
notifications of blockages in the wastewater system at
the hospitals each year. Blockages had been due to
patient wipes and paper towels causing backflow to
toilets and showers, leakages, etc. near clinical areas
. It was first after re-plumbing, replacing toilet bowls,
and etc., the infection rates were notably reduced. The
authors stressed the importance of hospital design and
engineering in controlling and preventing infection, a
factor that highlights the need for engagement from the
clinical staff, engineers, and janitors. Also, to consider,
these outbreaks were identified due to the unusual
antibiogram of organisms and could thus be linked to the
hospital wastewater systems. Clearly, hospital wastewater
system could be a source of many cases of infection with
different bacteria. Breathnach et al. concluded: “However,
unless the organisms are distinctive in some way, such as
being multiply resistant, or several cases with the same
species linked in time or place, it is likely that the source
of many such infections will remain unrecognized”.
Maintenance of sanitation is essential
Facts point at that sanitation is essential to maintain, to
reduce the risk of infection . In a press release from
WHO it stated that in “absence of proper maintenance
and without consistent monitoring, reviewing, enforcing
and updating of building standards and practices,
inadequate plumbing and sewage systems could continue
to enhance the potential of SARS and some other diseases
to spread ”. Numerous cases from both developing
and developed countries describe outbreaks caused by
faulty sanitation  (Table 1). The problem might be
that once sanitation facilities are installed the general
opinion seems to regard it as a self-sustaining system
that is safe. Furthermore, it is easily forgotten since the
drainage systems is out of sight. Thus drainage systems
are neglected as potential reservoirs of transmission of
microorganisms. It is when they cease to function
adequately because of e.g. leakages or blockages that the
threats to health becomes a reality and inspections
followed by reparations or even total exchange of drainage
systems are required [31,69]. The awareness about the
impact of inadequate sanitation seems poor. The illnesses
society, and nations .
Interdisciplinary work is needed in order to establish
guidelines for healthy sanitation in buildings focusing
on the clinical need for infection control supported
by architectural design and maintenance practices. To
accomplish the task, three aspects important for infection
reduction must be evaluated. 1) Detection of pathogen
containing aerosols and surface contaminants should be
done and further analyzed by molecular profiling and
Blom Archives of Public Health (2015) 73:8 Page 5 of 8
antibiograms in order to trace outbreak related pathogens.
2) Current architectural designs should be evaluated if
constructed from an infection reduction perspective. 3)
Also, the different maintenance practices should be evalu-
ated and explored how to optimize. Possibly, the GMP
guideline in food industry and their demands from an
infection reduction perspective could be a good start to
learn from. Also, the building and facility sectors should
be involved to develop what actions are required to main-
tain a safe sanitation system and with what detection
methods maintenance can be surveyed. One detection
method that could meet the demands for accurate moni-
toring of the status in the drainage systems is a technique
based on sonar technology, developed by Gormley et al.
. The need for guidance is especially urgent within
healthcare owing to that at hospitals the majority are
patients that are sick with less fit immune system and
therefore more receptive to infections and thus in need of
antibiotics that are effective.
Further research is needed to explore how aerosols
produced with or without faulty drainage systems can be
disseminated by existing ventilation system and cause
disease. In the case with the SARS outbreak, it was
clearly shown that the spread of the virus containing
aerosols created from the drains was facilitated by the
ventilation system. It was further proven in a sham study
that aerosols were created and spread by the airflow
upon flushing a toilet . Spread of pathogens from
wastewater via the drainage systems and out where no
physical barrier exist has also been proven in yet other
sham studies  evoking further issues such as what
are the consequences of letting out gases and aerosols
through the roof, possibly next to a ventilation inlet, or
if there is a leakage along the drainage systems within
the building ? Leakage or seepage shall be consid-
ered and its consequences analyzed. One possible effect
could be that humidity is increased thus promoting
microbial growth of for e.g. fungi risking mold in the
building and allergies to the inhabitants. The impact of
microscopic sized leakage is also of interest to study if
these would allow microorganisms being microscopically
small; virus being 0.1 μm, bacteria around 1 to 10 μm,
and fungi around 10 μm big, to leak. Results may show
that it is essential that drainage systems must be
completely tight and intact where openings have
Despite good sanitation, problems arise when the sanita-
tion system is not working properly in case of e.g. leak-
age and backflow caused by blockages or dried out traps.
It is beyond proof that wastewater, sewages, or drains
act as cradles for emerging new microorganisms with
increasing ability to resist antibiotics and possibly armed
with virulence factors obtained from other encountered
species [47,50,51]. The cradles consist of microbial
biofilm, where transfer of genes coding resistance and
virulence is promoted [47,62]. The pressure for selection
of resistant microbes is probably higher in healthcare
settings due to the turnover of many sick patients
shedding along with administered antibiotics down the
drains. Drains have been reported to be the source of
several outbreaks. However, outbreaks are not often
linked to the environment unless the outbreak isolate
possesses an unusual multi-resistant profile . The
threat of mortality rate equaling the pre-antibiotic era is
immediate and not for future. If no efficient antibiotics,
current infections can’t be treated and sensitive inter-
ventions will not be possible to pursue. Therefore, pre-
ventive actions are urgent and must be taken to reduce
infections causing us to focus on the fundamental need
for a safe and maintained sanitation system.
Dr. Kristina Blom is a consultant to many different companies and has for
this study been sponsored by Dyteqta Ltd.
Received: 13 October 2014 Accepted: 2 December 2014
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