How are phosphate dosages controlled?
Since phosphates do not change water chemistry, measuring phosphate in the raw and finished water is necessary to monitor the dosage rate. Orthophosphate ion (PO4 -) is the most common species used to measure the initial and total quantity of phosphate in the water. Orthophosphate can be measured on a coldwater sample, while the total phosphate requires a digestion step to break down all other forms of phosphate to the orthor form. Simple field test kits or laboratory analytical equipment can be used to monitor all forms. Subtracting the initial orthophosphate quantity from the total phosphate yields the quantity of polyphosphate present in the finished water (Total-Ortho=Poly).
