Dr. Robert Smith
Recent events have demonstrated that excess phosphorus in receiving waters can create many serious problems including impairment of drinking water supplies. For this reason and others, incorporation of phosphorus limits into NPDES discharge permits is occurring in many states.
Many facilities are being required to remove phosphorus for the first time and will need to add a process to the flow sheet. A discharge limit of 1.0 mg/L may be achieved most cost-effectively with chemical addition. Enhanced biological treatment may be needed to meet lower limits down to 0.5 mg/L and below. Additionally, biological treatment has other potential benefits.
Regardless of the treatment method, continuous monitoring is essential. Critical parameters include orthophosphate, dissolved oxygen, oxidation-reduction potential (ORP), total suspended solids, and nitrate.