Helpful USEPA Papers and Links

Here are three very helpful USEPA papers written by the Office of Ground Water and Drinking Water between 2002 and 2006.

Finished Water Storage Facilities August 15, 2002

 https://www.epa.gov/sites/production/files/2015-09/documents/2007_05_18_disinfection_tcr_whitepaper_tcr_storage.pdf

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2.1.1 Sediment

Sediment accumulation occurs within storage facilities due to quiescent conditions which promote particle settling. Potential water quality problems associated with sediment accumulation include increased disinfectant demand, microbial growth, disinfection by-product formation, and increased turbidity within the bulk water. Instances of microbial contamination and disinfection by-product formation due to storage facility sediments are described in the Pathogen Contamination and Microbial Growth section and the Disinfection By-Product formation section, respectively.

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Comprehensive inspections are performed to evaluate the current condition of storage facility components. These inspections often require the facility to be removed from service and drained unless robotic devices or divers are used. The need for comprehensive inspections is generally recognized by the water industry. AWWA Manual M42 (1998) recommends that tanks be drained and inspected at least once every 3 years or as required by state regulatory agencies. Most states do not recommend inspection frequencies thereby leaving it to the discretion of the utility. States that do have recommendations are Alabama (5 years), Arkansas (2 years), Missouri (5 years), New Hampshire (5 years), Ohio (5 years), Rhode Island (external once per year; internal, every five years), Texas (annually), and Wisconsin (5 years). Kirmeyer et al. (1999) recommend that comprehensive inspections be conducted every 3 to 5 years for structural condition and possibly more often for water quality purposes.

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Kirmeyer et al. (1999) recommended that covered facilities be cleaned every three to five years, or more often based on inspections and water quality monitoring, and that uncovered storage Prepared by AWWA with assistance from Economic and Engineering Services, Inc. 12facilities be cleaned once or twice per year. Commercial diving contractors can be used to clean and inspect storage facilities that cannot be removed from service. AWWA Standard C652-92 provides guidelines for disinfection of all equipment used to clean storage facilities.

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On December 2006 Office of Ground Water and Drinking Water. Total Coliform Rule Issue Paper. Inorganic Contaminant Accumulation in Potable Water Distribution Systems.

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Health Risks from Microbial Growth and Biofilms in Drinking Water Distribution Systems June 17, 2002

Health Risks From Microbial Growth and Biofilms in Drinking Water Distribution Systems.

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G. Sediment Accumulation

Significant microbial activity may occur in accumulated sediment (USEPA, 1992b). Organic and inorganic sediments can also accumulate in low-flow areas of the distribution system, and enhance microbial activity by providing protection and nutrients (USEPA, 1992b). Biofilms that slough can accumulate in the periphery of distribution systems leading to sediment accumulation and the proliferation of some microorganisms (van der Kooij, 2000). Sediments may be an important source of nutrients in open finished water reservoirs, by accumulating slowly biodegrading materials which are then broken down and released into the water column (LeChevallier, 1999b). The opportunities for biofilm development may be more abundant in storage tanks than in distribution system piping. Frequently, water is drawn from storage tanks only when water demand is high, such as during drought, fire flow, and flushing operations. This intermittent use results in prolonged storage times that may lead to increased sediment accumulation and lack of a disinfectant residual in the finished water storage vessel. Biological and aesthetic effects can be observed following the release of accumulated sediments from low flow areas of the distribution system (Geldreich, 1990).

Many studies have identified microbes in accumulated sediments, including both pathogens and non-pathogens. These include bacteria, viruses, protozoa, algae, fungi and invertebrates. Opportunistic pathogens that have been detected, and can multiply in sediments, include Legionella andmycobacteria (van der Kooij, 2000). Some primary pathogens can also survive for some time in sediments. Hepatitis A virus survived more than four months in sediments at both 5/C and 25/C (Sobsey et al., 1986). Other opportunistic pathogens found in sediments include Pseudomonas fluorescens and Flavobacterium spp. (Berger et al., 1993). Sediments can also release nutrients into the water which stimulate biofilm growth downstream (LeChevallier, 1999b).

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I. Proper Storage Vessel Management and Alteration

Proper storage vessel management and alteration, when necessary, can prevent contamination of the distribution system. Following TCR violations in 1996 in Washington D.C., one measure that proved effective in bringing the system back into compliance was the cleaning, inspection and disinfection of storage tanks and reservoirs (Clark, et al., 1999). To reduce pathogen presence and biofilm development, systems should have a scheduled program to rehabilitate all water storage facilities (USEPA, 1997). Proper operation and maintenance of storage tanks and reservoirs is listed as a BAT in the TCR (USEPA, 1992b). Storage tanks and standpipes should be pressure flushed or steam cleaned, then disinfected before returned to service (USEPA, 1992b), preferably with a disinfectant solution. This may not only remove microbial contamination from the vessel’s inner surface, but also nutrients that may be present. Proper operation of storage vessels can also reduce excessive residence times, which can lead to microbial survival and growth, and biofilm formation. Properly designed inlets and outlets, and the overall system design can improve problems caused by dead ends (Trussell, 1999). Pathogen contamination due to air introduction can be reduced by installing air filters to guard against pollution entering covered water reservoirs (USEPA, 1992b). Covering finished water reservoirs can protect against contamination from airborne sources, surface runoff, accidental spills and animals, such as insects and birds (USEPA, 1992b). EPA’s Uncovered Finished Water Reservoirs Guidance Manual describes recommended contamination control measures related to birds and other animals, human activity, algal growth and insects and fish (USEPA, 1999b). An understanding of the storage hydraulics and operation is important in reducing contamination of the finished water.

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If you need assistance inspecting or cleaning water storage tanks or towers call

Ron Perrin Water Technologies toll free at 1-888-481-1768.

For a fast quote Fax your tank information to 817-246-1740.

Or e-mail your tank information:

Out of Texas contact Robert at perrinsales@gmail.com

Texas Water Utilities please contact Debi Wheelan at tankinspections@aol.com

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The EPA is considering New Rules for tank Inspection & Cleaning

On July 14th 2010 the The U.S. Environmental Protection Agency  Posted this notice under / Proposed Rules

2. Storage Tank Inspection and Cleaning

EPA requests comment on the value and cost of  periodic storage tank inspection and cleaning . There are instances of storage tanks being the source of waterborne disease outbreaks at PWSs. In December 1993, aSalmonella typhimurium outbreak in Gideon, Missouri resulted in over 600 people affected by diarrhea, 31 cases of laboratory-confirmed salmonellosis and seven deaths of nursing home residents who had exhibited diarrheal illness (four deaths were confirmed by culture). The larger of the two storage tanks had a breach in the roof hatch that allowed pigeon droppings to be carried into the tank and likely accumulated in the several inches of sediment. This contaminated sediment, more than likely, was pulled into the distribution system by a flushing program that  drained the tank (Clark et al. 1996). Salmonella typhimuriumwas isolated from the sediment of one of the towers, and tap water tested positive for fecal coliforms (CDC 1996). In March 2008, Alamosa, Colorado (with a population of about 9,000 people) experienced a waterborne disease outbreak associated withSalmonella. The report released by the Colorado Department of Public Health and Environment (Falco and Williams 2009) indicated that the outbreak resulted in 442 reported cases of illnesses, 122 of which were laboratory confirmed, and one fatality. The State epidemiologist estimated that a total of 1,300 people may have been ill. Two storage tanks in Alamosa had several inches of sediment and breaches; one tank had breaches large enough for birds and animals to enter. Some of the key factors that contributed to these two outbreaks include significant levels of sediment (several inches to feet) and the presence of breaches of the integrity of the storage tank. Sediment accumulation occurs within storage facilities due to quiescent conditions which promote particle setting. Over time sediment continues to accumulate in a tank, even if the finished water is consistently treated tobelow 0.1 nephelometric turbidity unit(NTU). For surface water systems, it isnot uncommon to have 1⁄4 to 1⁄2 inch or more of sediment accumulate after two to three years (Kirmeyer et al. 1999).

While there are no turbidity regulations for ground water systems (except for ground water under the direct influence of surface water (GWUDI)), the levels of turbidity can be significant in the water pumped from an aquifer. Sand particles, if allowed to accumulate, provide pore spaces that house diverse populations ofbiota (which may include pathogenic microorganisms) (Kirmeyer et al. 1999; van der Kooij 2003). Periodic high flows in the storage tank may scour, stir up, and suspend the sediment (along with entrapped bacteria and pathogens) and carry it into the distribution system, with greater accumulation of sediment being a more significant concern. Other water quality problems associated with sediment accumulation include increased disinfectant demand and disinfection byproduct formation. The storage tank’s vulnerability to contamination increases when breaches of the storage tank allow insects, animals, and birds and their associated diseases to enter. Contamination from bird and other animal excrement can potentially transmit disease-causing organisms to the finished water.  Waterfowl, for example, are known carriers of many different waterborne pathogens including Vibrio cholerae(Ogg et al. 1989). Based on the potential public health implications associated with poorly maintained storage tanks (e.g., as indicated by significant sediment accumulation and breaches), EPA is interested in receiving comments and supporting information regarding the state and condition of tanks that have been cleaned and inspected, costs of storage tank inspection and cleaning, and how public health can be better protected. EPA requests information on whether there are States that recommend or require periodic inspection and cleaning of storage tanks. If so, what are the requirements, the frequency of inspection and cleaning, and how successful are they? Are inspections and cleaning done by individual PWSs or by contractors?

DATES: Comments must be received onor before September 13, 2010.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA–HQ–OW–2008–0878, by one of the following methods:

• Federal eRulemaking Portal: http://. www.regulations.govFollow the on-line instructions for submitting comments.

• Mail:

Water Docket, Environmental Protection Agency, Mailcode: 4101T, 1200 Pennsylvania Ave., NW., Washington, DC 20460, Attention

Docket ID No. EPA–HQ–OW–2008–0878. In addition, please mail a copy of your comments on the information collection provisions to the Office of Information and Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th St., NW., Washington, DC 20503.

The Importance of Cleaning Water Storage Tanks

Safe municipal drinking water has been with us so long that it is easy to forget that even today the World Health Organization estimates that over a billion people do not have access to clean drinking water.  Administrators who manage water systems know that the luxury of having safe drinkable water comes at a cost.  It is a constant struggle to maintain the aging infrastructure and keep up with the most effective water treatment options.

Although water treatment chemicals and treatment methods have taken great leaps forward over the years there is still a basic element of sanitation in our water systems that is often overlooked.  Simple sediment build up in the bottom of a water storage tank can undermine the best plans and most advanced chemical treatments. In a municipal water system sediment builds up over time.  With 10 years of inspecting water storage tanks behind us and thousands of tanks inspected, we have found that three inches of sediment or less is common across Texas, but we have found some tanks with many times that and even multiple feet of sediment.

Keeping your water storage tanks clean may be one of the most overlooked maintenance procedures in the drinking water industry.  Out of sight and out of mind, sediment in the bottom of your water storage tanks is never seen and rarely thought of.   The sediment that builds up in almost all potable water tanks can be a habitat for bacteria and other contaminates like cryptosporidium that devastated the city of Milwaukee in the spring of 1993.

Read the full article here:

https://tankdiver.wordpress.com/importance-of-clean-water-storage-tanks/

See a video of a tank being cleaned by a dive crew here: