New Water Main Disinfection. 1

[Pump2005]

I am looking for a listing of steps for disinfecting a new water main installation. I work in NJ and would like to find a standard that applies to NJ. I'm okay with the 24hr chlorination period but after flushing the new main after that period and achieving a system level residual is the coliform test taken then or does the main have to sit again?

 

[RWF7437]

try Googling this:

New Jersey Department of Environmental Protection,
Bureau of Safe Drinking Water
N.J.A.C. 7:10-11.6(d)

good luck

 

[semo]

Get AWWA C651 "Disinfecting Water Mains".

It should apply anywhere in the U.S.

I've not been able yet to find copies of AWWA standards on-line without a subscription; but, you can do a search and get on-line subscriptions.

 

[Pump2005]

The main question I can't seem to find information on is this, if the main has been flushed and you still have a high chlorine residual above the normal system level do you have to:

A: shut it down for another 24hrs, flush again and if the cl2 is okay take the bacti test.

B: Keep flushing until the residual is close to system level and then take a bacti test.

 

[RWF7437]

Almost certainly, doesn't "b" make the most sense ?

 

[bimr]

You should note that the technique of taking the sample is important as well. It is simple to contaminate the sample when an unexperienced person is sampling.

 

[Pump2005]

I would think "B" would be fine but I'm told "A" is the way to do it. I can't find any written listings of these procedures.

 

[semo]

If the level was held above 10 mg/l for 24 hours, then it wasn't flushed long enough. It should be flushed until the residual is at the normal level.

B should work.

The method of chlorinating could have an effect on this. If tablets are used, they may not totally dissolve within the 24 hour period. If that is the case, allowing the line to set an additional period could dissolve the tablets so they can be flushed out.

 

[bimr]

It is probably similar to this:

Standard Specifications for Water and Sewer Main Construction in Illinois

41-2.141 Repetition of Flushing and Testing

Should the initial result in an unsatisfactory bacterial test, the original chlorination procedure shall be repeated by the Contractor until satisfactory results are obtained on successive samples taken at least 24 hours apart.

I believe this is the same as AWWA Standard C651-92.

 

[rconner]

While I don't know if it has anything to do with the present situation, but for any not aware I believe C651 also contains the caveat, "Do not use calcium hypochlorite intended for swimming pool disinfection, as this material has been sequestered and is extremely difficult to eliminate from the pipe after the desired contact time has been achieved."

 

[Pump2005]

One problem was that I don't know how they chlorinated. I do the monthly samples for the town and that is pretty much how I got involved.
The engineer tested the residual after sitting 24 hrs and gave the okay to flush and left. I don't know how long they flushed but the residual was over 1ppm (1.10 mg/l)when I sampled it. With that being way over normal system levels it was decided to flush the main longer, increasing the flow. After an hour the residual was at .35 mg/l and decided to take the bacti test then. The test results were all negative. It pissed me off having to do what is the contractors job and the town being too cheap in not having an engineer on-site.