A properly designed injection system employs:

a. solution feed that is proportional to flow.

b. mixing (such as a static mixer) to insure that the fed solution is completely dispersed throughout the water stream being treated

c. sufficient contact time for the reaction to occur completely

d. a test kit capable of verifying proper feed rate.

 

Your friend may not be aware that item b. can't substituted for item c.

 

For coliform, I recommend you consult with your state, county or regional disrict's health authority and follow the contact time guidelines they have established.  These will vary with water temp. and pH.

 

Also, if possible, use a contact tank that is manifolded or baffled in such a way as to make use of the entire tank volume.  If your water enters and/or exsits the tank through a single-point fitting, the water stream will take a short-circuit path of least resistance  between inlet and outlet.  In this case you may only be using a fraction of the available retention tank volume and achieve only a fraction of the contact time.

 

The two most popular fiberglass retention tanks on the market that I am aware of can be fitted with some internal manifolding.  Steel tanks generally can't without difficulty.

 

I have seen advertisements for 'chemical mixing tanks' that claim to reduce retention time.  In my opinion, that is not the case, but I would change my opinion if reliable test data validated that.

 

Treatment processes other than disinfection - such as coagulation of suspended material or oxidation of iron, etc. each have their own application-specific reaction times that you will get a feel for over time.

 

Best of luck,

 

Allen

REx;

I have to concur with the above posts, the statix mixer will help  fully mix the chemical in a solution and create more suface area for adaquate contact with the water, but the kill time for bacteria still remains 20 minutes its a mater of physics. The fact is without the mixer you may not be getting proper chemical mixing to allow the contact time to be effective.

Iron and H2S have a lower contact time so it is possible to see positve results without a mixer on a 120 gallon tank but may be able to use a 40 or 80 gallon tank, with a mixer to get the same results.

So to answer your question Statix mixers do help reduce contact times for some parameters by providing complete mixing, but its better to use the full 20 minutes when bacteria is involved.