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.

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 penetrates 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 of 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 the 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).

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 no restorable 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).

Chemical Disinfection 
The processes 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 by 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 that 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%), phenolic (0.5 to 5%), iodophors (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 the phenolic and glutaraldehydes, leave a residue that continues to suppress microbial growth for some time after treatment.