During a one year study, four tertiary treatment units were tested and evaluated. Three of the units were deep-bed filters which were used to treat secondary plant effluent. The types of filters used were: (1) an upflow filter with a sand media, (2) a downflow gravity filter with mixed-media consisting of anthracite, sand, and garnet, and (3) a downflow pressure filter utilizing dual-media of anthracite and sand. The fourth unit was a continuous flow ion exchanger that employed activated alumina to remove phosphate from microscreened secondary effluent. The filtration studies indicate that comparable effluents were produced by all three filters with filtration rates from 2-6 gpm/sq ft. Filter effluents generally contained about 4-7 mg/l suspended solids in the above flow range. The results of the ion exchange study indicated that sodium hydroxide successfully regenerated an exhausted activated alumina bed. In a 9-hour test, the ion exchange column removed 73% of the influent phosphorus, using 0.4N sodium hydroxide as the regenerant.

Performed by Metropolitan Sanitary District of Greater Chicago under EPA grant no. FWPCA WPRD 92-01-68. Project officers: Arthur N. Masse and James F. Kreissl. "EPA-600/2-76-264." "December 1996."