Indiana Water Environment Association
2016 Annual Conference
Abstract
Putting the spin on sludge to increase capacity and reduce O&M costs
Harry Lawson, Evansville Water & Sewer Utility
Joseph Teusch, P.E., Greeley and Hansen
As a part of the Renew Evansville initiative, the Evansville Water and Sewer Utility (EWSU) analyzed its solids handling process in an effort to improve the cost-effectiveness of its biosolids management operations and to improve the work environment for operations staff. EWSU owns and operates two (2) water resource recovery facilities with solids stabilization provided by anaerobic digestion. The biosolids processes include dewatering, storage and disposal.
The existing solids handling equipment was approaching the end of its service life. As such, belt filter press and centrifuge technologies were compared on chemical usage; operation and maintenance; and sludge disposal costs using a triple bottom line approach to determine which technology would serve them best going forward.
The existing solids handling building contained four (4) 2-meter belt filter presses. The firm capacity of the belt filter press process capacity was 450 gpm. In contrast, centrifuges could provide more solids processing capacity for the same or less foot print making it a more sustainable and cost-effective option. Three (3) centrifuges, each with a capacity of 250 gpm, could meet the capacity requirements today while providing room for the addition of another centrifuge when needed without the need to expand the current building. Further, the implementation of the Integrated Overflow Control Plan (IOCP) will increase the solids loading to the WRRFs during wet weather so the ability to handle more solids is important.
Other benefits EWSU has derived from the change to centrifuge technology is the higher cake solids concentration achieved at the same or reduced chemical usage to belt filter presses. The higher cake solids and reduced sludge disposal more than off-set the increased power cost for the centrifuge operation. Centrifuges operate in a closed process which is cleaner and less odorous for operations staff. Belt filter presses are an open process that contributes to high humidity and release of odors.
The presentation will discuss the technology evaluation and provide operational results between belt filter presses and the new centrifuges with respect to chemical usage, power costs, and disposal costs.