Aeration Improvements to Save Energy

The City of San Jose at its San Jose/Santa Clara Water Pollution Control Plant has embarked on a series of projects to reduce energe consumption and provide operational savings, and aeration system upgrading is one of the key projects. The plant was converted in 2000 from a coarse bubble, cross-roll in 2000 to fine bubble membrane tube diffusers, which produced significant savings. In 2009 a second project was initiated to develop an even more cost effective alternative using a greater number of diffusers in slightly different geometries. Off-gas testing was performed to confirm aeration efficiency. An economic analysis was used to determine the most cost effective alternative. Upgrading the original year-2000 retrofit with diffusers having more active surface area provided a pay back of approximately one year. The economic analysis also confirmed that the decision to upgrade the original coarse bubble system with fine bubble diffusers was sound and would provide a payback of 3 to 6 months using current costs, One counter-institutive result was the inadequacy of the original coarse bubble diffuser air piping. The in-tank headers were able to provide even air distribution for coarse bubble diffusers but were unable to do so with fine pore diffusers, which operate at much lower air flow rate. Upgrading options are continuing and addional energy conservation activities will occur.