Water and Sewage Clean up | Suggested Guidelines & Recommendations

Suggested Guidelines for Remediation of
Damage from Sewage Backflow into Buildings

Michael A. Berry, Ph.D.; Jeff Bishop; Claude Blackburn; Eugene C. Cole, Dr.P.H.; William
G. Ewald; Terry Smith; Nathan Suazo; and Steve Swan. Mr. William G. Ewald Health
Scientist Environmental Criteria and Assessment Office, U.S. Environmental Protection
Agency (MD-52) Research Triangle Park, NC 27711

Abstract

Sewage backflows are serious health threats to humans indoors. The purpose of this
paper is to summarize what is known about health effects associated with sewage backflow
into indoor environments and to make technical recommendations for safe, effective
restoration. Risks to health from specific pathogens are considered, and the classes of
disinfectants and their properties are discussed. The recommendations for remediation
are based largely on the characteristics of the contaminated material and the length of
time of the contamination.

Introduction

Water is the single most long term destructive substance in the indoor environment. It
dissolves or weakens many materials and supports the growth of microorganisms on
others. Because it flows, water has the capability to carry with it a wide variety of
pathogens and allergens harmful to humans. (1). In the best of worlds, buildings would be
designed so that flooding would never occur; however, in the real world, water sometimes
gets out of control in every building. When a water emergency occurs, quick reaction to
seepage, spillage, flooding, or backups has many benefits. Quick reaction often saves
valuable property from direct water damage as well as destruction from microbial growth.
The longer any kind of water damage goes untreated, the greater the damage. Immediate
response to a water emergency saves time and money, and protects property and health.
The primary objectives of controlling water damage are well known to professional
restorers and public health professionals. These objectives are to protect public health,
immediately remove harmful substances that enter in the environment with flowing water,
restore the environment to a dry state, and salvage valuable property. The objectives are
even more critical when flood waters contain animal or human body fluids or wastes (e.g.,
raw sewage) or other organic contaminants.

Sewage poses a very significant threat to human health. However, the severity of the
health threat depends on the content of the sewage and the degree and extent of
penetration into the building environment. The degree of penetration is dependent on the
porosity of contaminated materials, the quantity of sewage, and the amount of time the
sewage remains in contact with materials. Consider three examples of sewage spilling into
an indoor environment; the restoration response may be different in each situation.

Situation 1. A very limited quantity of waste that originates in the built environment is
deposited or flows slightly beyond the confines of the sewage system. In this situation, the
waste is found in one specific location, is contained, and does not penetrate the building
structure. A limited amount of contact time has occurred. An example of this situation
might be waste that overflows in a bathroom and is deposited on and confined to a tile
floor. In this situation, there is a limited quantity of waste, which is contained and does not
contact absorbent materials. Decontamination, which includes water extraction, cleaning,
and disinfection, can be effective in reducing this particular potential health risk.

Situation 2. Waste that originates in the built environment is deposited or flows beyond the
confines of the building’s disposal system. In this case, there is limited or confined
flooding, but water and waste penetrate the structure and furnishings of the building. For
example, flooding occurs in a men’s room of an office building, water flows under a wall and
into the carpet of an adjacent hallway. In this case, there is a limited amount of waste that
is confined to a relatively small area of the building, but it penetrates regions of the
environment that have complex surfaces and are difficult to restore. Effective restoration
involves decontamination (as in Situation 1) as above and drying all surfaces that have
been in contact with the sewage. In the case of stretch-in carpet, lifting and cleaning the
contaminated carpet, disposing of the cushion, and treating both sides of the carpet
thoroughly with a disinfectant are all necessary. Affected porous wall materials need to be
treated with a disinfectant and evaluated for replacement. Because of the confinement of
the sewage spill, aggressive, comprehensive treatment can be effective.

Situation 3. Waste that originates in the built environment, along with other wastes from
the main line of the sewage system, is backed up into the immediate environment, where
the waste is widely dispersed and penetrates both the structure and its furnishings. In this
situation, there is extensive risk because humans can be exposed to pathogenic raw
wastes that have penetrated and become contained by the building and its furnishings. If
flooding is from this kind of primary outside sewage system, occupants should be
evacuated, and restoration should begin immediately. In this situation, cleaning and
restoration professionals should be protected by using respirators with high-efficiency
particulate air (HEPA) cartridges, rubber boots, gloves, splash goggles, and protective
garments. Extreme care should be taken to avoid puncture wounds during the restoration
process. Restoration staff who have cuts or open sores should not be allowed to work on
this kind of restoration project. The principles of restoration of this situation are outlined in
the last section of this paper, which contains specific recommendations for techniques.
The main discussion of this paper focuses on the potential health risks posed by a sewage
backup similar to Situation 3.

Description of the Primary Problem

When a building is contaminated with sewage backing up from the septic lines, or flooding
of a building occurs that involves sewage or a heavy load or organic matter, as in the case
of river flooding, a serious threat to human health exists. Without appropriate action,
extensive damage to materials will occur immediately or in time. Several days may elapse
before the cause of the backup is determined, the problem is corrected, and flooding
subsides. This allows extensive permeation and contamination of absorbent (hygroscopic)
materials such as wood, gypsum, paper, and concrete to occur. This penetration with
water and organic matter leads to the growth of potentially disease-causing (or
opportunistic) microorganisms. These Organisms may pose a serious health risk to
occupants of the building. Organic matter and water-saturated materials can be used as
substrate for growth of microorganisms (such as gram-negative bacteria and toxigenic
fungi) that can produce substances toxic to humans and damaging to materials. A large
amount of water inside a building will cause high humidity, which can also contribute to
microbial growth on structural materials and contents (2).

Questions To Be Raised After Sewage Contamination

Some of the questions to be answered in this situation include the following: What are the
effects of the initial contamination of the building, its contents, and the health and welfare
of its occupants? What is needed to thoroughly clean up the contamination and repair the
damage? Should the entire building or a portion of the building be evacuated and, if so,
for how long? Can semi porous materials be decontaminated, or should they be
replaced? What are the consequences of using inadequate measures to remediate the
damage? What are the indicators that help determine when the building is safe or not safe
for occupancy? What methods should be used to test for these indicators? What is the
effect of the sewage damage on other systems, especially the air changing systems (ACS)
and the heating, ventilating, and air conditioning (HVAC) systems in the build environment?

Issues of Concern Associated with the Problem

There are several factors bearing on the remediation of the problem. Among these are
the nature of the contamination, the types of water-damaged materials (organic or
synthetic; porous, semi porous, or nonporous), the sewagemicroflora (pathogens and
allergens), organic matter load, water volume, and impact of ambient outdoor temperature
and humidity on the indoor environment. Of major concern are the survival of sewage-
borne micro flora (viral, bacterial, fungal, parasitic, and their potential transmission to
humans. The potential exists for some fungal and bacterial contaminants to establish an
ecological niche and present a health risk from chronic exposure for some time after the
event.

Scope of These Guidelines

The discussions within this paper will address the immediate and longer term effects of
sewage-flooding contamination on the building’s structural materials and contents; the
potential effects on occupants; and the steps to remove contamination to include flushing
with clean water and detergent solutions, vacuuming, dehumidification, and disinfection.
The potential health threats presented at each stage of remediation will be discussed.
These include the production of bioaerosols during removal of gross contamination, the
long-term effects of residual moisture and organic matter on the building and occupants,
and the colonization and growth of non-sewage-borne species of microorganisms such as
molds and other fungi.

Assessment of Damage and Danger to Health

The factors that determine the extent of contamination within the building include the
volume and the solids content of the sewage backflow, whether flooding is isolated to the
basement or involves other levels as well, and how long the contamination has been in
place.

The assumption must be that potential pathogens are present in the contamination. Such
microbial contamination includes bacteria, fungi, viruses, and parasites. Table 1 lists the
micro flora that may be found in raw, untreated sewage and the diseases that these
organisms have the potential to cause (3). Also, hypersensitivity lung disease has been
shown to be caused by repeated flooding of homes with sewer water (4).

The routes of exposure of the building occupants to these pathogens are contact,
ingestion, and inhalation. An incomplete or inadequate job of cleaning and disinfection
may leave residue that can be a substrate for disease-causing microorganisms.
Occupants may be infected by contacting contaminated surfaces, with inadvertent
transmission from hands to mouth, or aerosolization of contamination may result in the
inhalation of microorganisms or their products (e.g., endotoxins). Residue and microbial
contaminants also can be tracked by occupants’ feet to other parts of the building.

Another aspect of health impact is that the conditions caused by sewage backflow or
flooding are conductive to the growth of nonsewage microorganisms. These conditions
include wetness, humidity, and organic matter. Microorganisms, which exist in various life
stages in both indoor and outdoor environments, would then have the opportunity for
exponential population growth. These species (see Table 2) can produce bioaerosols,
which are potential sources for disease. For example, mold allergy is a common source of
indoor air symptoms and complaints (5).

In regard to the susceptibility of building occupants, those individuals whose immune
systems are in some way compromised (i.e., immunocompromised), or who are otherwise
susceptible due to age, medication, or underlying illness, are considered to be at greater
risk of contracting potentially fatal infections than those individuals who are healthy.

Fundamental Considerations for Remediation

The factors to be considered in remediation include the types of materials affected,
assessment of the degree of damage, the extent of contaminated absorbent material, the
total contact time, the humidity, and the amount of ventilation available. The primary goal
of remediation must be the complete removal and disposal of water and contamination
using the sanitary sewer system if possible. Wet extraction systems should be used to
completely remove sewage and water used for cleaning. As part of this phase of the
operation, removal of affected contents and structural materials may be necessary. These
items could include carpet, wall covering porous wallboard, and insulation, and other
substrates with the potential for mold growth. Disposal of nonrestorable contaminated
materials requires that the materials be confined in plastic bags and transported to
appropriate disposal facilities. In all cases, workers must be provided with appropriate
personal protective equipment such as respirators, boots, gloves, splash goggles, and
coveralls, and with equipment with which to remove contamination (6).

In order to speed the drying process, both mechanical and natural dehumidification should
be employed as the gross contamination is removed and during restoration. An indoor
humidity target of 40% relative humidity (RH) or less should be attained as quickly as
possible (7). If possible, depending on the design of the contaminated space and the
outdoor weather conditions, there should be ventilation with fans and evaporation of indoor
water by introducing outside air. The use of dehumidifiers for removal of moisture from
inside building surfaces and air is recommended. The ACS and HVAC systems may be
considered as dehumidifiers, depending on the systems’ mechanical capacity versus the
extent of moisture load over time. Rapid drying that stresses proper management of
temperature, airflow, and dehumidification is essential for success.

Desiccant dehumidifiers, using silica-gel or lithium chloride, could be employed as an
adjunct to disinfection to reduce RH to as low a level as possible (8). Moisture content
measurements of reclaimed materials is an important criterion of the success of adequate
drying and the remediation process.

Chemical Disinfection

The process of decontamination and disinfection will be important to ensure the elimination
of pathogens and organisms that were contained in the sewage or that grew during the
period of contamination. Even concrete can be colonized and broken down my
microorganisms if it is allowed to remain wet and contaminated by organic matter.
Chemicals categorized as disinfectants are appropriate in this application. A disinfectant
may be defined as an agent that reduces significant numbers of pathogens on inanimate
objects to a level below the expected to cause disease. Disinfectants may not kill spores,
however, and, because some bacterial and fungal spores will always be present in the
environment, it would not be feasible to attempt to kill all of the spores in an affected area.
Emphasis instead should be placed on removal of the substrates, water, and organic
matter needed for the growth of spores.

Choice of disinfectants depends on the degree of microbial killing required, the nature of
surfaces to be treated, application safety, and the cost and ease of use of available
agents. It is recommended that disinfectants be used in accordance with the manufacturer’
s instructions for use and dilution.

Classes of disinfectants and their common-use dilutions include alcohols (60 to 90% in
water), quaternary ammonium compounds (0.4 to 1.6%), phenolics (0.5 to 5%),
iodophores (75 ppm), glutaraldehydes (2%), household bleach (sodium hypochlorite,
diluted 10%), and hydrogen peroxide (3 to 6%). The advantages and disadvantages of
each of these disinfectants are given in Table 3. For example, the use of iodophores or
low-concentration chlorine compounds would require that little organic matter be present
on surfaces, a condition that may be difficult to achieve. Caution should be used in mixing
some disinfectants. For example, mixing chlorine-containing solutions with ammonia or
amine solutions will produce extremely toxic vapors, and could have lethal effects on
workers or building occupants. Of critical importance is “contact time”. Contact time is the
length of time that the disinfectant is permitted to work on the contaminated surface. The
contact time must be at least 15 min before additional cleaning and removal of the
disinfectant is undertaken. Some disinfectants, such as phenolics and glutaraldehydes,
leave a residue that continues to suppress microbial growth for some time after treatment.

Health-Based Recommendation for Restoration

The following specific guidelines are presented with a goal of restoring the contaminated
area such that the health of occupants is protected from any risk of pathogen-caused
disease.

•        Remediation should begin as soon as possible. The longer the contamination is
allowed to persist, the greater the potential for microbial growth and resultant damage.

•        Unprotected occupants and workers should be evacuated from the affected areas
during the initial stages of decontamination, cleaning, and disinfection (e.g., until sewage
has been removed and disinfectants applied).

•        Technicians in the vicinity of the sewage during the initial stages of decontamination,
cleaning, and disinfection should be equipped with an organic vapor HEPA respirator,
rubber gloves, splash goggles, and boots. In the case of overhead contamination,
technicians should also be equipped with goggles, hard hats, and protective suits.
Technicians should report any wounds that occur during restoration and take care to avoid
“cross-contamination” from affected to unaffected areas by foot traffic or material handling.

•        After water removal, all affected materials should be decontaminated by spraying
with a disinfectant solution. It is not the intent of this prespray to effect full disinfection
because the presence of organics precludes this. The objective is to initiate the reduction
and containment of microorganisms as quickly as possible.

•        All affected materials should be evaluated for porosity (permeance). From this
inspection, materials should be rated as highly porous (saturated), semi porous, and
nonporous. Some materials may exhibit varying degrees of porosity, depending on the
exposed surfaces. For example, the surface of painted drywall has very low porosity, yet
the base of the wall may be unpainted or have exposed gypsum paper that is highly
porous.

•        Highly porous (permeance factor >10) materials that have been exposed to sewage
backflow and have a value that exceeds the cost of restoration such as high-value rugs
and carpet, upholstery, and other textiles should be removed and restored off site. Highly
porous materials with low cost or replacement value, such as carpet cushion, carpet,
cardboard, tackless strip, wicker, and straw, should be removed and discarded as soon as
possible. Other materials, such as saturated mattresses and cloth upholstery, regardless
of value, cannot be restored and should be discarded. If disposal is necessary, these
materials should be bagged in plastic for removal to a proper disposal site.

•        Semi porous (permeance factor of >1 to 10) materials, including items such as
linoleum, vinyl wall covering and upholstery, and hardboard furniture, along with
construction materials such as wood, painted drywall and plaster, should be cleaned,
disinfected, or replaced as part of the initial restoration process.    If these materials are
not removed or properly disinfected, they can become reservoirs for growth of
microorganisms.

•        Nonporous materials (permeance factor £1) such as Formica™, linoleum, vinyl, and
tile finishing materials can be inspected for subsurface contamination with a
nonpenetration moisture meter. Although these materials may be rated as nonporous,
they must be evaluated carefully because contamination can migrate from the perimeter
and become trapped below the surface. If migration of contamination below the surface
has not occurred, these materials may be fully restored.

•        Heavy organic matter, especially raw sewage and silt, must be physically removed by
any safe means available. This may include the use of shovels, squeegees, septic pump
trucks, wet vacuums, and moisture-extraction machines. Water must also be extracted
from floor-covering fabrics such as carpet and rugs. All tools and machines, especially
recovery tanks, wands, and hoses, must be cleaned and disinfected after use.

•        Residual organic matter in cracks and crevices can be removed by pressure washing
with a disinfectant solution. The solution then must be recovered with an extraction unit,
immediately after application, to prevent further migration or saturation of contaminants
into other porous materials.

•        After removing heavy organics, affected materials must be cleaned before a second
application of disinfectant takes place. Use of many cleaning agents, such as soaps and
detergents, will solubilize most organic matter.

•        After thoroughly cleaning all contaminated materials, a second application of
disinfectant may be applied.

•        Chemicals classified as disinfectants are appropriate for use in areas exposed to
sewage backflow. These chemicals are defined as being capable of inactivating potential
pathogenic microorganisms on inert substrates.

•        Fully evaluate all factors that affect the success of decontamination. These include
the organic matter present, extent of prior cleaning, type and level of microbial
contamination, concentration and time of exposure to the disinfectant, and the nature of
the material to be decontaminated.

•        Sources such as Block (9) provide information about the classes of disinfectants.

        Glutaraldehydes: These agents display a broad spectrum of activity and rapid rate
of kill against the majority of microorganisms. Glutaraldehydes are capable of destroying
all forms of microbial life including bacterial and fungal spores, tubercle bacilli, and
viruses. They are excellent sporicides and will not corrode most materials. Disadvantages
include increased peroral, percutaneous, and inhalation toxicity, along with elevated eye
and skin irritation.

        Iodine and Iodine Compounds (Iodophors): These agents are highly effective, have
broad-spectrum antimicrobial capabilities and exhibit some residual properties.
Disadvantages include inactivation by organic matter, and vapors may pose a hazard to
respiratory organs. Some formulations may stain porous materials an orange-yellow color.

        Phenolic Compounds: These agents are stable (less inactivated by organic matter),
broad spectrum (generally include antiviral properties), and readily available, and leave a
residue. Disadvantages include substantially increased peroral, percutaneous, and
inhalation toxicity, along with eye and skin irritation.

        Quaternary Ammonium Chloride Compounds (Quats): These agents have a limited
spectrum of activity but are capable of killing gram-positive bacteria and fungi, and of
inactivating gram-negative bacteria and some viruses. Quats have a naturally pleasant
odor, counteract offensive odors, and are excellent cleaners. Ammonium chloride
compounds are safer to use than most other disinfectants, because they are less toxic and
cause less irritation to the mucus membranes. Quats, when diluted for use, are low in
toxicity and irritation. Disadvantages of this class of agents include the facts that they are
neither sporicidal nor tuberculocidal and that many formulations exhibit poor results
against gram-negative bacteria and some viruses. Also, these compounds are
incompatible with anionic cleaners (i.e., mutual neutralization of disinfectant and cleaner)
and with the dye blockers in stain-resistant carpet.

        Procedures should be implemented to increase the rate of drying. Dampness and
humidity must be reduced as much as possible by using the existing ACS or HVAC system,
auxiliary fans, carpet dryers, and dehumidifiers. The indoor humidity in affected areas
should be reduced to 40% RH as quickly as possible. When flooding has been extensive,
the drying process may require several days or longer to be effective.    Adequate drying
should be evaluated with a moisture meter. The humidity should be monitored with a
hygrometer or a psychrometer.

        Because the use of disinfectants such as glutaraldehydes, iodophors, and
phenolics for disinfection produce irritating vapors, appropriate personal protective
equipment to preclude chemical exposure is required. The type of safety equipment used
will depend on the disinfectant used, the concentration, and the method of application.
The material safety data sheet (MSDS) and label instructions on the chosen disinfectant
will provide more detailed information and must be reviewed before use.

        Environmental monitoring should consist of moisture measurements, rather than
surface or air sampling for the presence of viable microorganisms. After the restoration
process, surveillance of occupants for sickness, allergy, and sensitivity may also provide a
measure of the adequacy of the clean-up operation.

        Area rugs and wall-to-wall carpet that have been extensively saturated with sewage
backup are unlikely to be cost-effectively restored on site. Such rugs and carpet, along
with the cushion, or underlayment, should be removed. Small rugs may be restored
effectively through commercial laundering. If an effort is made to restore the carpet,
extensive cleaning and saturation disinfection of the carpet should take place. All organic
material must be removed, and the complex fibrous surfaces throughout the carpet must
be disinfected. Following treatment, the carpet must be inspected thoroughly for
cleanliness and dryness before being reinstalled in the restored environment. Carpet
cushion must be removed, disposed of, and replaced with new material, without exception.
Sub flooring should be cleaned, disinfected, died, and sealed if necessary before carpet
and rugs are returned to the environment. Under no circumstances should efforts be
made to restore carpet and rugs on site that have been extensively damaged by a
Situation 3 sewage backup.

        In any case where it is deemed cost justifiable to restore carpet contaminated by
sewage, an extraction cleaning method must be employed on all surfaces. Other carpet
cleaning methods, such as absorbent compound, absorbent pad (bonnet), dry foam, or
shampoo cleaning, are not adequate in that they may merely redistribute the
contamination (10).

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