Breakpoint Chlorination to Control Nitrification

[Brick583]

I am working on a project where a chloramined drinking water system is experiencing low chlorine residual in some parts. I think that if i identify some of the sources of accelerated chloramine degradation in the system i will hopefully be able to improve the CR in the system without addition of a Booster Chlorination Station. One problem that i think is occuring significantly in the system is nitrification, based on our water testing data, Im not sure. Through reading all the AWWA manuals and reports i understand what can happen in systems and how it happens, but i am still having trouble with the major problem of what exactly is happening chemically in this system.

The major questions i still have are
-Where does our water system fit on the breakpoint curve? (i.e. why does our data show combined, free chlorine and free ammonia residual all together)

-Is our observed increase in nitrates/nitrites enough to be significant nitrification

-If we were to use breakpoint chlorination what steps would we have to follow to safely control the free chlorine residual.

I have included our water testing data.

I am stumped at this point any and all help will be greatly appreciated.

 

[kjmastaw]

Hi Brick583, I'm wondering if you're creating chloramines which are then being picked up in the nitrate/nitrite tests? Superchlorination would help. I've attached a link to the wikipedia article about chloramines.

Regards,
Kevin

 

[kjmastaw]

Take a look at lowering your pH. Nitrite/Nitrate formation will be significant above pH 9 s.u.

 

[bimr]

It is a common problem to have poor chlorine residual at dead ends in a water distribution system.

The operator of the water distribution system should be able to identify these areas.

You will still have the problem even if you use breakpoint chlorination.