Spent pickle liquor, as a source of ferric ion, was added to primary treatment facilities and found to be effective in removing more than 60% of the phosphorus contained in the sewage. When advanced means for more complete removal of the insolubilized phosphates are available, removals in excess of 90% are indicated. In addition, overall suspended solids removals averaged 61.5% and BOD and COD removals averaged 61.6 and 55.3 percent during a 23 month test period. Required iron dosage ranged from the theoretical minimum of 2.7 to a maximum of approximately 3.1 weights of ferrous iron per weight of phosphorus. The weight increase in sludge solids due to chemical precipitation of phosphorus was 100 lbs/million gallons/mg/liter of phosphorus in the influent. Total costs for treating a raw sewage containing 13 mg/l phosphorus are given.

The magnitude and effects of biological activity in expanded carbon beds used for direct clarification/adsorption treatment of wastewater were investigated. Major aspects of the project involved comparisons of the relative effectiveness of aerobic and anaerobic conditions in the expanded-bed systems, and a comparison of the relative treatment effectiveness of expanded carbon beds of high and low sorptive activity under aerobic operating conditions. The use of short polishing columns to remove traces or organics escaping from on-line adsorbers was also evaluated.