Chemically Mediated Phosphorus Removal to Low Levels: Analysis and Interpretation of Data

Multidimensional data, from experiments designed to simulate a range of conditions for chemically mediated phosphorus removal, are analyzed. The experiments involve different sample matrices from deionized water to raw wastewater, and different experimental techniques in terms of equilibration times and mixing conditions. The experimentally manipulated variables include coagulant type, coagulant dose, and initial phosphorus concentration, and the measured variables include pH, alkalinity, conductivity and residual phosphorus after treatment. To visualize the multidimensional data, normalization techniques are applied. This data reduction, together with principal component analysis, showed that even with the variable experimental conditions, consistent observations can be made from the data. Higher molar doses yield lower residual P and there is an optimal pH range between pH 4 and 6 for phosphorus removal; with significant removal up to pH values around 8. Existing literature models, including the equilibrium WEF and Surface Complexation (SCM) models, were used to describe the data, and the SCM model was more successful in describing trends over the entire data set. The implications from this analysis is that future experiments must be designed with wastewater treatment operation parameters specifically in mind and that SCM models are a reasonable starting place to model chemical P processes on the treatment plant.