Phosphorus reduction by the direct addition of aluminum sulfate in the aeration chamber: of an activated sludge waste treatment plant

The College View Utility District operates a small extended aeration package waste sewage plant in the LaPorte-Deer Park vicinity. A stringent 2 mg/1 phosphosus effluent limit was set by the Texas Water Quality Board. A new waste treatment plant incorporating tertiary methods could meet the effluent parameters but would require approximately one million dollars to construct. A method of injecting liquid alum directly into the aeration chamber of the existing unit was devised and tested simultaneously with plant operations. Satisfactory effluent phosphorus levels were achieved, using this approach at estimated final cost of less than l/50th the cost of the new plant. Previous work had described injection of alum near the end of the aeration section and preferably in the effluent channel from the aeration tank. Thus, this technique represents a departure from current methods of phosphorus reduction using alum injection. This process provides a method of upgrading existing waste treatment plants for phosphorus removal at a reasonable cost.