Lessons Learned from 20-years of Low-Level Phosphorus Removal

The lessons learned from more than two decades of planning, design, construction and operation of numerous add-on treatment facilities of varying sizes to meet low-level phosphorus (P) will assist communities that are just now receiving phosphorus limits in their discharge permits. Numerous technologies have proven capable of achieving much lower levels of phosphorus than thought possible 20 years ago. This allows technologies to be selected based on cost criteria and non-cost criteria other than process performance. Overall considerations related to permit language, the impacts of soluble non-reactive phosphorus, coagulant selection and mixing, metals limits, and the use of real-time analyzers for process optimization should be investigated during planning and design since they can be just as critical to achieving treatment goals as the process selected.