The Hatfield Township, Pennsylvania, Water Pollution Control Plant was designed to encompass primary chemical treatment, secondary combined activated sludge and nitrification facilities, tertiary chemical tube clarification and mixed media filtration. The operation of the facility demonstrated that the use of flow equalization facilities improves plant operations by reducing and standardizing chemical concentrations. Phosphorus is removed efficiently in a combined primary-tertiary phase with operations personnel having the flexibility to optimize each process. Lime feed control by pH is easily accomplished, although recirculation of primary sludges is not always necessary. Tube clarifiers and mixed media filters combine to produce a highly polished effluent. Nitrification was observed to some extent in this modified facility, however, it was extremely difficult to control.

"Program element no. 1BB043." Report prepared by Tracy Engineers, Inc., Camp Hill, Pennsylvania. Includes bibliographical references (pages 161-163). "Report date September 1975."