Paul H. King

The stimulation of filamentous microorganisms in activated sludge by high oxygen concentrations

A laboratory study was conducted to compare the response of an activated sludge culture proliferating in an environment where the DO concentration was maintained between 8-9 mg l−1 to that of a culture in an environment where the DO concentration was 2 mg l−1 when both systems were subjected to identical loading fluctuations. It was observed that in the high DO system, filamentous microorganisms became the predominate form when the suspended solids concentration dropped below a value near 4000 mg l−1. However, no filamentous growth appeared in the alternate system until the suspended solids level dropped below 500 mg l−1. A model is developed which proposes to explain this observation.

A Proposed Structure of an Aluminum-Phosphate Species of Importance in Wastewater Treatment

Abstract A laboratory study was conducted to determine the nature of the hydroxy-aluminum phosphate species present in wastewater treatment processes employing aluminum salts for the removal of phosphorus. At pH 5.0 the aluminum to phosphate molar ratio for optimum phosphorus removal was 1.44. Although several species may be formed, the chemical formula determined for the principal complex proposed by the authors is Al13 (OH)30 (H2PO4)9 · 18H2O. A postulated structure for this precipitate is presented.