Sewage Remediation Suggestions for Effective Cleaning

Recently, IET worked on several projects where sewage remediation contractors had difficulty achieving a sufficient level of cleanliness or sanitation to pass a “clearance” test. This would apply to contamination associated with a sewage backflow or other IICRC Category 3 “black water” event.  These projects are, by their very nature, challenging.  This article attempts to provide some sewage remediation suggestions for more effective and efficient project completion, addressing the areas where IET has often observed remediators having difficulty accomplishing.   

IICRC S500 standardNote:  The standard of care applied by the conscientious remediator should always be that outlined in the current edition of IICRC S500 Standard and Reference Guide for Professional Water Damage.  This is at present the Fourth or 2015 edition.  This article is intended to supplement S500-2015 and emphasize certain of its recommendations that we have found particularly important in achieving satisfactory results, not to conflict with or replace S500.




Objective for Sewage Remediation

As with all restoration/remediation, the goal is to return the property/environment to “normal” or sanitary conditions as quickly and efficiently as possible.  All actions should contribute to achieving this objective. Those that do not so contribute should be reconsidered.

Do No Harm

This is a key principle of sewage remediation.  It has two primary applications in remediating fecally-contaminated environments:

  • Health and Safety must be the single most critical issue from start to finish of the project. An environment of this type represents significant health and safety risks, more so than even a “normal” water damaged structure, which is already a hazardous environment.  Safety includes protecting workers as well as occupants to the extent the sewage remediator has control of the project, and, if necessary, deciding whether he wishes to be involved in a project where he does not have sufficient control to ensure safety.  This includes implementing both Engineering Controls, which reduce the risk directly, and Personal Protective Equipment (PPE), which protect workers against risks that cannot be eliminated with Engineering Controls.

NOTE:  A truly significant safety issue on such projects involves sharps on the biohazardjobsite.  When performing demolition, sharps capable of penetrating skin are always present, and on a sewage remediation project those sharps are very likely to be coated with pathogenic bacteria. A cut or puncture can cause these bacteria to be injected below the skin or even directly into the bloodstream.  This is a potentially life-threatening hazard! Special efforts should be made to protect against skin penetrations, especially for hands and feet.  Any cut or penetration must be handled as a medical emergency, not just a first aid issue.

  • By the time the remediator arrives on-site, contamination has already occurred and has spread to some extent.  The sewage remediation contractor cannot know, on arrival, exactly how far contamination may have spread, since it

    A containment/engineering control to help prevent tracking

    can become aerosolized  and often significant tracking by occupants has already occurred and detecting such contamination normally requires sampling and laboratory analysis.  However, the remediator is obligated, to the best of his ability, to prevent further spread of contaminants once he has some control over the project.  Containment should address all possible forms of spreading, including both tracking and aerosolization of contaminants.  This often requires erection of containment barriers and maintaining negative pressure in the work zone.


It is a good idea, when dealing with a Category 3 water damage event, to avoid thinking of it primarily as “water damage restoration,” which normally deals primarily with the drying of wet materials.  The 2015 edition of S500 makes very clear a point that was sometimes only implicit in earlier versions:  the primary issue on a sewage remediation project is removal of contamination and sanitization of the environment.

In other words, such a project is primarily a decontamination project, with drying often only a relatively small part of the project.  Normally, decontamination should be performed, returning the project to sanitary condition, and only then should aggressive drying of any materials that are still at elevated moisture content be implemented.  Among other corollaries of this principle, air movement should never be used as a drying tool.  In fact, air movement in the affected area should be kept to a minimum to help prevent aerosolization and spread of contaminants.

Determining the Scope of Work for Sewage Remediation

Since the removal of contaminants is the primary objective, it is critical to determine how far those contaminants may have spread.  If arriving shortly after discovery, moisture meters and infrared imaging can provide excellent information on how far primary contamination with liquid water has spread.  This should be done as soon as initial safety issues have been addressed and can help to determine appropriate containment.

sewage remediation post test

Swab sampling for fecal contamination

However, the possibility of tracked and/or aerosolized contaminants must also be addressed.  This is normally done by surface sampling for the presence/absence of indicator sewage organisms.  See below and Sewage Testing Methods after Remediation for Fecal Contamination.   Such sampling, per S500, should be done by a qualified Indoor Environmental Professional  (IEP).  This will normally result in a minimum 48 to 72 hours turnaround time from the taking of samples.  During this time work that is known to be needed, such as removal of contaminated porous materials, can proceed.  When sample results have been received, IET and the remediator can work together to develop a comprehensive scope of work, which may be significantly more extensive than originally thought.

Rough Cleaning, Initial Sanitization and Demolition

Note:  Rough cleaning to remove gross contamination as well as an initial application of appropriate sanitizers is usually appropriate before starting demolition.  This application of sanitizer is an engineering control intended to reduce (not eliminate!) risk for workers.  See discussion of Sanitizing below.

As a rule, porous materials directly contacted by Category 3 water should be removed and discarded.  This includes carpet, cushion, tackless strip, insulation, etc.  It also includes many contents items.

Semi-porous materials, primarily wood framing, can often be cleaned and decontaminated.

Non-porous materials such as vinyl flooring or ceramic tile can often be effectively cleaned and decontaminated, unless contaminated water has penetrated under or behind them, in which case they must be removed to access the contaminated surfaces for remediation.

Note: S500-2015 Reference Guide Chapter 17 has extensive tables outlining in detail procedures appropriate for cleaning and sanitizing a wide variety of materials and assemblies.  However, keep in mind that every situation is different, and that no standard can ever adequately address every possibility.  Professional judgment in applying the principles of S500 to individual situations remains key.  This should not be considered carte blanche to do whatever the remediator wants to.  Whenever deviating from specifics outlined in S500-2015, the remediator should document a logical reason for the deviation.

Detailed Cleaning

After rough cleaning, initial sanitizing and demolition, the next and in many ways most important step in decontamination is detailed cleaning.  Cleaning is defined as the removal of contaminants from a surface.  Proper detailed cleaning not only helps to reduce the fecal organism load dramatically, but it also helps remove other constituents of sewage with possible health effects, such as endotoxins and allergens.

Rough or gross cleaning is often required on the project as one of the first steps, and it is usually obvious how to do it.  Cleaning in several steps, each bringing the assembly closer to “clean,” is usually more effective than attempting to bring an assembly or environment from heavily soiled to very clean in a single process.

Micrograph of a “smooth” concrete surface

In mold remediation, we generally perform cleaning using as little water or other solutions as possible.  For sewage remediation this approach is often counter-productive.  The contaminants were carried in water, so they penetrated wherever the water penetrated.  Since the contaminated materials being cleaned are often irregular (concrete and stone) and/or semi-porous (unfinished wood), and the contaminants in question are often sub-micron in size, it is very difficult to remove contaminants effectively using low-moisture methods.  Effective cleaning methods for such surfaces often involve the use of a relatively large amount of water-based cleaning solutions, which means a key aspect of effective processing is keeping this water under control so adjacent materials aren’t overwetted.  “Spray and wipe,” while often convenient, may tend to clean across the top of the irregularities, leaving the soils and contaminants embedded in the irregularities themselves largely unaffected.  A process such as, “flood with solution, scrub aggressively, then soak or vacuum up solution” is much more likely to achieve the desired degree of sanitation.   Repeating such cleaning “rounds,” perhaps with sanitizer application between rounds, is often highly effective.

Effective sewage remediation should, whenever possible, incorporate sanitizing agents into the solution to reduce micro-organism counts.  What sanitizing agents are appropriate will of course vary greatly with the surface being cleaned, but IET’s experience has been that a solution of chlorine bleach and detergent is highly effective at both cleaning and sanitizing.  A chlorine bleach and water solution, without detergent, may not be nearly as effective, due to the lack of surfactant action, which helps bring soils into solution for removal.  The detergent used must be compatible with chlorine bleach to prevent generation of toxic fumes.  Keep in mind that chlorine bleach is not appropriate for many surfaces and assemblies, even beyond the obvious concerns with bleaching of finish materials.  It is especially a poor idea for use where it could contact ferrous and other metals, such as fasteners, due to long-term corrosion problems.

There are many other cleaning/sanitizing products available, including many based on quaternary ammonium chloride compounds.

Where possible, cleaning/sanitizing products should be EPA registered for this specific use.  These products should always be used in strict compliance with directions, most notably as to dwell time and whether rinsing is required.  EPA:  Selected EPA-registered Disinfectants.

The irregular nature of many surfaces makes detailed cleaning challenging.  A method that has often proven effective for final, as opposed to initial gross cleaning, is “low-pressure washing.”  This approach involves “pressure washing” at relatively low pressures of 20 to 40 psi.  The water jet is more effective at getting into irregular surfaces than a cloth wiping across the surface. High-pressure washing should be avoided in most situations because it produces massive splattering and aerosolization of contaminants, unless contained in a vacuum shroud, in which case it can be highly effective for aggressive cleaning of concrete floors, tile and grout, and similar surfaces. Low-pressure washing should be done with a spraying system designed specifically for this use and the remediator should have special systems in place to prevent over-wetting of adjacent surfaces and materials.

This high-pressure washing system is contained in a vacuum shroud. Highly effective for hard surface floors. Photo courtesy of EDIC.

A cleaning method with significant potential is true steam cleaning (not hot water extraction).  The vaporous nature of steam means it penetrates easily into irregular surfaces and semi-porous materials.  Steam cleaning usually does not use any chemicals for cleaning, relying on the high energy of the steam for soil removal.  It also has obvious sanitizing effects, though this should not be relied on for primary sanitization on most surfaces.  Steam cleaning machines vary greatly in cost, in the heat and volume of the steam produced, in how dislodged soils are collected, etc.  They range from inexpensive home models that aren’t very effective to industrial equipment that is very effective indeed.  Note:  Steam cleaning, like high-pressure washing, can aerosolize and splatter contaminants.  The system must be able to effectively contain and collect dislodged soils.


IET will use this term to refer to all processes primarily intended to reduce the number of fecal organisms present by killing or inactivating them.  As noted in the previous section, cleaning, by definition, has sanitizing effects, and those effects increase when cleaning/sanitizing solutions are used.

S500-2015 recommends a copious application of an EPA-registered sanitizer or disinfectant as one of the first steps.  This is NOT intended to provide complete disinfection, and will not accomplish it.  However, it is an effective engineering control for reducing (not eliminating) the number of fecal and potentially pathogenic organisms present.  Repeated application of sanitizing agents as new materials are exposed while performing demolition is also a good idea, for similar reasons.

The final and most critical application of sanitizing agent is performed after all detailed cleaning has been completed.  Effective cleaning removes most organic soils, which tend to deactivate most sanitizers.  For this step, a disinfectant registered with the EPA specifically for black water decontamination should always be used and it should be applied carefully per directions, with special attention to dwell time and rinsing, if required.

The Sewage Remediation Process (very rough outline, not necessarily in exact chronological order)
  1. Initial application of sanitizer.
  2. Containment of area believed to be affected, often with negative pressure to prevent escape of any aerosolized contaminants, and with special precautions to prevent tracking.
  3. Gross cleaning and water removal (extraction, etc.). Obvious unsalvageable wet materials removed, such as wet drywall, carpet and cushion.  Detailed cleaning started in known affected areas.
  4. Dehumidification to control humidity and help prevent mold growth.
  5. Inspection and sampling by IEP to determine true scope of work.
  6. Finalization and approval of remediation plan after lab results have been received.
  7. Containment redesign and installation, if needed.
  8. Any additional needed demolition is performed.
  9. Final detailed cleaning. (May require several “rounds” of cleaning.)
  10. Final sanitization.
  11. Post-Remediation Verification (PRV) by an IEP to document successful completion of remediation and return of the environment to sanitary condition.
  12. Needed reconstruction. This work is performed in a now-sanitary environment and can proceed as with any other remodeling work.
Adjustments to sewage remediation processes based on Post-test method

There are two methods that are widely used for determining whether remediation has been successful at decontaminating the environment:

  • Testing surfaces for presence/absence of indicator fecal organisms
  • Testing surfaces for adenosine tri-phosphate ATP concentrations

See Sewage Testing Methods after Remediation for Fecal Contamination for a detailed explanation of these processes and how they differ.

Since they measure different things, the emphasis of an effective remediation strategy may vary somewhat depending on which method will be used for testing in the PRV.


Enterococcus, one of the indicator organisms often used

Presence/Absence of indicator organisms

This method tests for viable indicator organisms, so remediation efforts should focus on ensuring they will be Absent.  This can be done by careful cleaning and thorough, detailed and repeated application of effective disinfectants/sanitizers.  Aggressive cleaning of irregular surfaces such as concrete slabs is helpful, as it helps ensure that the sanitizing agents contact the organisms, which may be deep in the surface irregularities.

Absolute cleanliness, as such, is not as critical as for the ATP test method.

ATP concentration test method

This method essentially tests for absolute cleanliness, the attainment of which should be the primary focus, with use of sanitizing and disinfecting agents of course a key part of the cleaning/sanitizing process.  We have found that irregular surfaces such as concrete slabs and semi-porous materials such as wood subfloors or framing are especially difficult to clean thoroughly enough to meet the clearance criteria.  See above for discussion of specific cleaning methods that may make cleaning more effective.

True steam cleaning might be very helpful, due to its ability to potentially remove soils from highly irregular surfaces.  Where it can safely be used, chlorine bleach appears to be one of the more effective sanitizing solutions for this test method.

When possible, ATP testing should be performed immediately after cleaning, to prevent possible recontamination, such as by aerosolized soils.

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