TORPEY RECIRCULATION PROCESS (TRP) FOR INCREASED DIGESTER CAPACITY

摘要

The City of Phoenix, Arizona (City) is implementing the Torpey Recirculation Processrn(TRP) at its 23rd Avenue Wastewater Treatment Plant (WWTP) as part of thernMechanical Sludge Processing Facilities project. TRP was developed by WilburrnTorpey in the 1960s and successfully operated full-scale at the City of New YorkrnBowery Bay WWTP. Since then, very few plants have implemented TRP and thernprocess has not appeared in the literature for many years. TRP is defined herein asrnthe recirculation of digested sludge from anaerobic digesters to an upstreamrnthickening process before it reenters the digester. The primary effect of TRP is thernthickening of digested sludge in the digester, with excess water returned to the liquidrntreatment facilities. The digested sludge may or may not be co-thickened with anotherrnprocess sludge flow such as primary sludge or waste activated sludge (WAS).rnThe 23rd Avenue WWTP digester expansion faced both site and budgetaryrnconstraints and TRP allowed the City to provide the required digestion capacity withrnfour digesters in lieu of five digesters. By using TRP, the plant operators will be ablernto manage the SRT in the digesters to maintain adequate stabilization over varyingrnloading conditions with a smaller total digester volume than by using a conventionalanaerobic high-rate digestion process. Digester performance, volatile solidsrndestruction and gas production, is expected to improve with TRP, without adversernimpacts on operations or process stability.