Article by Chris Griffin ADEM, Posted on the Alabama Department of Environmental Management web site.
Would you drink from a dirty water glass?
This is a great article that ask a great question. It also points out that the Alabama Department of Environmental Management has certain recommendations about routine water tank and tower maintenance that include tank inspection at least once every five years.
But they have gotten it WRONG. Alabama requires the tank to be inspected by draining and disinfecting the interior a minimum of once every five years.
What is wrong with that you ask?
Disinfecting is NOT CLEANING. We are not all speaking the same language here. Many say disinfecting assuming when that is done the tank will be clean. This is not the case. From the engineers who build water storage tanks down to the managers who run the systems there has been a major break in communications with what is actually in water storage facilities.
The tanks & towers are designed to be CLOSED SYSTEMS, they store the crystal clear clean water that comes from the water plant. When Alabama DEM requires operators to drain & inspect the water storage tanks and then disinfect the interior, that disinfection process is to kill whatever contamination may have been introduced into the tank during the inspection. Sediment that was on the floor of the facility before the inspection is there after the tank is disinfected and placed back into service.
Disinfecting is not Cleaning, if you have contaminates like bacteria, protozoa or even viruses buried in the sediment before the disinfection the majority of them are going to be there after the disinfection. The only way to remove them from the facility is to CLEAN the TANK.
Most tanks and water towers were not designed to be cleaned. There are no handy cleaning ports to open up and wash things into. It was assumed by the designing engineers that only clean water would be stored in these facilities and there was no need.
The reality is that over time sediment accumulates on the floor of water storage tanks and towers. They need to be Cleaned out, not looked at and disinfected.
Once sediment is de-watered a few inches of soft simi -liquid sediment can become 1/2 inch of hard clay like coating stuck on the floor of the tank. An underwater inspection can offer more information about the facility without any disruption in service. Divers deployed to clean the tank can remove everything that is loose in the floor of the facility and provide video documentation confirming the job was done and the floor is now clean.
Washing a tank out after draining it for an inspection is not a viable way to clean a tank. For example on an elevated tower, where is the sediment being washed to? We have seen many cases where it was washed down the center standpipe only to return when the facility is put back in service.
The other option is a bucket and shovel, where even the most dedicated crew can not get 100% of the sediment out. The shovel is also hard on the painted surface of the floor. Divers removing the sediment OUT of the facility and onto the yard of the tank is really the best option. When you consider the disruption in service, man hours and cost of water divers are also the most economical option to clean a water storage tank or tower.
This is a great article that ask a great question. It also points out that the Alabama Department of Environmental Management has certain recommendations about routine water tank and tower maintenance that include tank inspection at least once every five years.
But they have gotten it WRONG. Alabama requires the tank to be inspected by draining and disifecting the interior a minimum of once every five years.
What is wrong with that you ask?
Disinfecting is NOT CLEANING. We are not all speaking the same language here. Many say disinfecting assuming when that is done the tank will be clean. This is not the case. From the engineers who build water storage tanks down to the managers who run the systems there has been a major break in communications with what is actually in water storage facilities.
The tanks & towers are designed to be CLOSED SYSTEMS, they store the crystal clear clean water that comes from the water plant. When Alabama DEM requires operators to drain & inspect the water storage tanks and then disinfect the interior, that disinfection process is to kill whatever contamination may have been introduced into the tank during the inspection. Sediment that was on the floor of the facility before the inspection is there after the tank is disinfected and placed back into service.
Disinfecting is not Cleaning, if you have contaminates like bacteria, protozoa or even viruses burried in the sediment before the disinfection the majority of them are going to be there after the disinfection. The only way to remove them from the facility is to CLEAN the TANK.
Most tanks and water towers were not designed to be cleaned. There are no handy cleaning ports to open up and wash things into. It was assumed that only clean water would be stored in these facilities and there was no need.
The reality is that over time sediment accumilates on the floor of water storage tanks and towers. They need to be Cleaned out, not looked at and disinfected.
Once sediment is de-watered a few inches of soft simi -liquid sediment can become 1/2 inch of hard clay like coating stuck on the floor of the tank. An underwater inspection can offer more information about the facility without any disruption in service. Divers deployed to clean the tank can remove everything that is loose in the floor of the facility and provide video documentation confirming the job was done and the floor is now clean.
Washing a tank out after draining it for an inspection is not a viable way to clean a tank. For example on an elevated tower, where is the sediment being washed to? We have seen many cases where it was washed down the center standpipe only to return when the facility is put back in service.
The other option is a bucket and shovel, where even the most dedicated crew can not get 100% of the sediment out. The shovel is also hard on the painted surface of the floor. Divers removing the sediment OUT of the facility and onto the yard of the tank is really the best option. When you consider the disruption in service, man hours and cost of water divers are also the most economical option to clean a water storage tank or tower.
Potable Water Diver in DRY SUIT
Sand & Sediment being removed from a Potable Water Tank
If you have any more details about rules for inspecting & cleaning water storage tanks in Alabama or any other state contact me- Im always glad to share information.
By Photos by Ron Perrin (c) Ron Perrin 2010 all rights reserved
Ron Perrin Clean Water Tank Project 