All water tanks accumulate sediment over time. The soft sediment in the floor of water tanks and towers becomes a safe habitat for bacteria, protozoa and even VIRUSES! *** see reference at bottom of the page.
Out of sight out of mind-
No one thinks about the sediment. Most have no idea it is even there.
Not the water utility administrators, not the mayor not the elected city council members. Many times elected officials vote to clean or repaint the exterior of a water tower and never consider the inside condition. The popular view is that Pure Treated drinking water is pumped into the water storage tank or tower where it is held, until the end user opens a tap at their kitchen sink and gets a glass of crystal clean water.
The Truth-
All water distribution systems accumulate sediment in tanks over time.
The water is often tested daily, if the chlorine residual goes down – operators do not ask why, they just add more chlorine, over time the additional chlorine breaks down and itself becomes a contaminate in the tank that can cause cancer. *** See References below
Instead of constantly adding more and more treatment chemicals, simply cleaning the sediment from the floor of the tanks is the solution.
A countless number of biological contaminates can use the sediment in the floor of water tanks and towers to get a foot hold in a municipal drinking water system and grow into a real health concern. Why should we care what is on the bottom of a water storage tank?
We drink off the bottom of water storage tanks! Of course like many things the adverse health effects are unequally distributed to poor communities where drinking store bought bottled water is not a given, It is also these communities who have underfunded water systems that suffer from lack of maintenance.
Many utility systems that can afford inspection and cleaning of their systems simply do not allocate the funds for it because there are no regulations requiring them to do so.
In Texas yearly inspections of water storage tanks and towers are required.
Tanks get inspected in Texas. The problem in this state is there is no rule or regulation requiring tanks to be cleaned. So while thanks get inspected every year, most are seldom if ever cleaned.
The AWWA (American Water Works Association) recommends that water storage tanks be cleaned every 3 to 5 years or as needed. The EPA has published multiple white papers about contamination public water systems and the importance to keep tanks free of sediment.
Few ever read EPA white papers and AWWA recommendations are largely ignored when there are no rules or regulations backing them up.
Of course there is always someone who is doing the right thing out there, just because it is the right thing to do. In this case that would be the City of Arlington, Texas.
According to surveys conducted by the Environmental Working Group, Arlington, Texas has The best water in the United States, probably making it the best water in the world. Arlington is located in the middle of the DFW metroplex getting its water from the same source as 50 other systems. The water is treated in two water plants using similar treatment chemicals and methods as surrounding systems.
What sets them apart? For the past 18 years But they have made a commitment to keep their tanks clean, Every year a Potable Water Dive crew is contracted to vacuum the tanks clean while they remain full of treated drinking water. The divers literarily clean dust from the floor of water storage tanks, while surrounding cities allow multiple inches to accumulate before cleaning.
Too many water utilities in this country have no idea how much sediment if any is in the floor of their water storage tanks because they have never hired an inspection crew with underwater cameras to check it out. It is never thought of so they stay caught in the cycle of adding more and more treatment chemicals when contamination is detected.
Lack of regulations in this overlooked undervalued part of our infrastructure is needlessly putting millions of people at risk for illness, cancer and even death. When the solution is as simple as cleaning the floor of a storage area. It just so happens that this area stores water, and it is often 150 foot or more up in the air.
The City of Arlington has proven the effectiveness of keeping water storage tanks clean,
According to the research I did for my book “Inspecting and Cleaning Potable Water Storage” the majority of states do not have regulations requiring inspection or cleaning.
Do you think the EPA should require tanks to be Cleaned?
Take the poll : CLICK HERE AND TAKE THE POLL AT THE BOTTOM OF THIS BLOG
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This is a vastly complicated subject, that can be pulled down to three very simple terms.
- If you have a water storage tank or tower in your town there is sediment in it.
- Sediment bad,
- Remove Sediment and you remove the inorganic contaminates the habitat that organic contaminates can grow in.
See: Disinfection byproducts list at: http://water.epa.gov/drink/contaminants/index.cfm#Byproduc
Reference: Health Risk From Microbiological Growth and Biofilms in Drinking water Systems. Published by the EPA office of Water June 17, 2002.
http://www.epa.gov/ogwdw/disinfection/tcr/pdfs/whitepaper_tcr_biofilms.pdf
QUOTE:
PAGE 26 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 and mycobacteria (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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Page 34 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).
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Ron Perrin Clean Water Tank Project 