Ferric Dosing Control for P removal

[tipp79]

Does anyone know of a reliable method for controlling ferric dosing for phosphate removal when you have variable phosphate in the influent?

The treatment works in question is a SBR and has been failing to meet its discharge on Total P. The works serves a hotel with a fluctuating population. Ops believe that the high P values in the effluent coincide with dates when high phosphate detergents are discharged from the hotel. At present, ops manually change the dose but this has not been a successful approach. Would it be okay to continuously give a higher than required dose?

 

[FiltrationEngineer]

You can purchase a phosphate analyzer, which would work best on plant effluent, and automatically changed the dose based on conditions. You may want to put the analyzer on influent, but the water needs to be filtered first. Online analyzers are not cheap, but they work. Hach makes one.

Another less expensive option is for the operator to take samples and do a quick colormetric test to monitor phosphate in the influent manually. Then they can change the dose manually on the metering pump to get proper treatment.

Overdosing is an option but probably isn't cost effective.

 

[ch81pc]

We use a PLC to dose ferric at a variable rate depending on the diurnal load entering the works. The speed of the diaphragm pump is controlled by the inlet flow and the stroke changes depending on the pre-programed dose profile.