Abstract
In a conventional activated sludge aeration tank, organic nitrogen was almost completely converted to ammonium but very little was converted to oxidized forms of nitrogen (nitrite and nitrate) . Nitrification and denitrification in the aerated unit process, though, was achieved by using three submerged cells with porous sides consisting of nonwoven materials for retention of biomass. When synthetic wastewater with nitrogen only in organic form was fed directly into a cell (as opposed to the surrounding aeration tank), T-N decreased from 42 to 30 mg/l and TOC levels, from 110 to 10 mg/l. Because virtually all activated sludge was attached to cell walls, there was essentially no excess sludge wastage over 100 days of operation. Denitrification efficiency using the novel apparatus was shown to be effected by TOC and alkalinity in the influent wastewater as well as dissolved oxygen levels and the method of influent feed. When wastewater was fed simultaneously into two cells, versus only one, the T-N removal efficiency improved from 34% to 45%. Effluent T-N was shown to decrease with a decrease in DO in the aeration tank and careful control of TOC and alkalinity levels in the wastewater feed allowed for nitrogen removal efficiencies as high as 75%.
