Dosing Sodium Hypochlorite in Raw Municipal Sewage

[Watro]

Hello Peers,

We are working on a project and need some clarity. What will be the dosage rate of NaOCl if this is injected in raw sewage to maintain a free residual chlorine of 0.5 mg/l. Injection directly in to an ATM tank with a retention of 1 hour. I believe ammonia will consume some hypo, what else and what shall be the basis for dosing rate.
Further, what will be the coli form bacteria reduction due hypo injection. Can we expect a reduction to <3000 MPN/100ml by just dosing hypo? There is no treatment as such other than HYPO dosing

Thank you
NM

 

[ashtree]

It is impossible to estimate the dose as there are many variable in this proposal.
In addittion to the ammonia , iron , manganese, sulphides and a whole list of organics will all consume chlorine. In theory it should be possible to get a 100% coli form reduction if you inject enough hypo but the amount dosed could be huge. Sewerage has so much variation though to do this reliably is going to be difficult.There is also going to be all sorts of complex compounds formed as a resu;lt of the disinfection process that may compromise the "safety" of the water being produced.

This does not seem like a very good idea.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[Watro]

In fact, the idea is to discharge the sewage from an offshore deck directly in to Sea by just disinfecting them. (Apologies, I missed to add this data)

I agree, there are several consumers of Hypo, but would like to know if there is any way to estimate them.
The HYPO will generated on site, so the high dosage is not an issue, but not sure, it is 10 or 100 or 1000 mg/l of dosage. If there is any article to highlight this will help or any past experience

Thanks and Regards
NM

 

[MartinLe]

May I ask why you disinfect the sewage? Especially since there's no other treatment.

 

[ashtree]

There are so many variables in sewerage to give you a number some of which are very site specific . If you had a very detailed analysis it might be able to be calculated from first principles.

If i had to make an order of magnitude estimate I would say 500mg/l.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[Watro]

The discharge to marine environment criteria require 0.5 mg/l of FRC

Thank you Martin and Ash

Best Regards
NM