Mitigating Low Chloramine Residuals

[MJSMPE]

Hello,

I was wondering if anyone came across low chloramine residuals at the end of an extensive distribution system? A client (County) purchases potable water from another muncipality (City)and is connected to the city's disitribution system. The chloramine residual is readily maintained in the summer but drops off in the winter during periods of low water usage. The chloramine residual declines along the pipeline enough that by the time it reaches the last two communities on the 50 km PVC pipeline, the total chlorine residual is below the regulated level(0.5 mg/L). Is boosting the chloramine residual somewhere along the pipeline possible? I realize that you will have determine the background ammonia at the point and then add chlorine to ammonia at a 4:1 ratio. If the ammonia residual is too low both chlorine and ammonia would have to be added. It is prefered to maintain a chloramine residual and not over chlorinate to pass the breakpoint.

Some additional information is that the PVC pipeline is less than a year old and that any pipe gasket lubricant that was not removing during the flushing may be eating the residual. The County could maintain a flushing program to increase the residual but it is costly to waste water that they paid for at the end of the pipeline.

 

[hydrae]

MJSMPE

It is possible to boost a chloramine residual back to the original dose, generally additional ammonia will not be required, I would suggest a pilot study to observe the effects in your system, be careful, realy old water may have the ammonia decomposing to a nitrate.
Look at the AWWARF studies on chloromines for more information.

Hydrae