Sewage Circulating Reactor - An Approach to Recirculating Wastewater in Sewers

Abstract

This study deals with recirculation of wastewater so that a portion of the conveyance conduit works as a circulating biological reactor (referred to as Sewage Circulating Reactor). Experiments were performed with a pilot scale unit made of 87.12 m long galvanized iron channel in which wastewater was recirculated back to the starting point. Surface reaeration was the only source of oxygen and the unit was first fed with synthetic wastewater at Chemical Oxygen Demand (COD) and Total Nitrogen (TN) loading rates of 16.81–62.02 and 1.8–7.84 gm−2d−1 respectively. Later campus wastewater was fed in at loading rates of 15.73–19.06 gCODm−2d−1 and 4.66–5.44 gTNm−2d−1. An optimal TN removal of 0.77 gNm−2d−1 was obtained at a TN loading rate of 3.78 gTNm−2d−1. The corresponding COD loading and removal rates were 27.45 and 22.0 gCODm−2d−1 respectively. A distinct decrease in DO level in the system was observed with increasing loading rates. This resulted in decrease in nitrification rates at higher loadings. In the ca...