Streamline - Spring 2013 - (Page 27)

Is the Tank Contaminating the Water? BY ERIKA HENDERSON, PITTSBURG TANK & TOWER Something as simple as a damaged screen on a vent or overflow pipe could allow the water in the tank to become contaminated. operators realize the risks for contaminated water, but pathogenic microorganisms that create water borne diseases are still sometimes found in public water systems. Pathogenic microorganisms are in human and animal feces, and they invade the body when water contaminated with them is consumed. An infection is often created by the bacteria, virus, fungi or protozoa. These infections can spread rapidly, and sometimes even create an epidemic. So how do these pathogenic microorganisms get into the drinking water system? Is there anything that can be done to prevent their invasion? MANY WATER SYSTEM Water is treated and tested for microorganisms during the water treatment process. But, if the clean and healthy water is stored in a contaminated water tank, then all the water becomes contaminated, and people’s lives may be put at risk. If the water stored in the water tank is not tested and treated regularly, then the risk for waterborne diseases increases. But how did the water in the tank become contaminated if only healthy treated water is stored there? Well, something as simple as a damaged screen on a vent or overflow pipe could allow the water in the tank to become contaminated. Birds and insects can easily get into a tank through a defective screen. If birds are in the tank, then there are also bird feces and probably dead birds in the tank. The dead birds and insects attract other animals, and, before long, the water tank could contain a party of growing bacteria and toxins created from the feces and decomposing animal parts. The most disturbing part is that usually, a damaged screen is not noticed until an inspection is performed on the water tank. E-coli, cholera, dysentery, salmonellosis, campylobacteriosis, leptospirosis, botulism and vibrio are just some bacteria that could be present in the tank water. Tank openings and animals are not the only way the water in a water tank could become contaminated. Stagnant water containing parasites can also cause parasitic infections to occur in those who encounter the contaminated water. Dracunculiasis, taeniasis, fasciolopsiasis, hymenolepiasis, echinococcosis, coenurosis, ascariasis and enterobiasis are parasitic infections that could occur from stagnant water. Stagnant water can occur in water that has become stratified, or separated into layers. These layers are normally arranged according to density, with the least dense and warmer water sitting above the denser cooler layers of water coming in. The layers are caused by differences in temperature, pressure, and pH. These unmixed layers cause water quality to deteriorate and age, increasing bacterial growth. Many water tanks are getting mixing systems installed to prevent this stratified water. Water temperature can be checked every five foot during the inspection to determine whether stratification is a problem. If a mixing system is needed or desired, it should be designed according to the tank’s unique dimensions and needs. Water from the bottom of the tank should be pulled to the surface, and mixed with the incoming water. This process should increase contact time and prevent the development of biofilms. It should also reduce the level of trihalomethane (TTHM) and halo-acetic acids (HAA) which are formed easily by chlorination in slightly acidic water, or water with high organic matter content and elevated temperatures. Deaths and illnesses occur daily from unhealthy water, and water operators can lose their license to operate a water system if unhealthy water is found in their system. The best way to prevent the spread of infection and diseases linked to drinking water is to have public water storage tanks inspected, cleaned, and disinfected regularly to prevent the growth of pathogenic microorganisms. America Water Works Association (AWWA) states that, “Tanks should be washed out and inspected at least once every three years, and where water supplies have sediment problems, annual washouts are recommended” (AWWAM42-88). 27

Table of Contents for the Digital Edition of Streamline - Spring 2013

From the President
From the Executive Director
What If?
Stormwater Management
Soapbox Farewell
Water and Wastewater Certifi cation Exam Test Taking Tips
Past 25 Years of VRWA
Proactive vs. Reactive
Asset Management and Drought Management
Is the Tank Contaminating the Water?
Committed to the Future of Rural Communities
Standard Operating Procedure For Leak Detection Using the Pressure Hold Method
The Virginia RATES Program is at Your Service
Ergs, Joules and Other Stuff
Employee Introductions
VRWA 25th Annual Exposition Agenda
Wastewater Math
eLearning Benefits
Do You Know What Your VRWA Benefi ts Are?
Membership Application
Throwing My Loop
VRWA Mailbag
Welcoming New Members
Training Calendar
Board Of Directors
VRWA Committees
Index To Advertisers/

Streamline - Spring 2013