Finer filtration

recently won the annual Engineering Achievement Award from the

(CWEA), Santa Clara Valley Section, for a new filtration approach that could significantly improve filtration performance in wastewater treatment, thereby reducing operations and maintenance costs.

The new filtration approach involves the use of a relatively large-diameter filter medium in conjunction with air-enhanced backwash procedures. According to the firm, the method has performed beyond expectations in an ongoing plant-scale study at the South Bayside System Authority (SBSA) wastewater treatment plant. The SBSA processes approximately 20 million gallons of wastewater per day and serves the cities of Menlo Park, Redwood City, Atherton, Portola Valley, Woodside, San Carlos, and Belmont.

Typically, solids are removed from wastewater using granular filters in a dual medium configuration of anthracite (coal) and sand. The configuration for this project uses a monobed (single-layer) anthracite that is approximately 2.5 times larger in diameter than SBSA’s existing media.

“No one else has tried to utilize media this coarse to filter wastewater,” explained Kennedy/Jenks engineer Kapil Verma, who helped lead the study. “We also found that employing an air-water combination instead of a water-only method to clean the filter during backwash procedures is much more efficient.” During the plant-scale study, the use of the new media has significantly increased treatment run times while producing effluent that complies with SBSA’s National Pollutant Discharge Elimination System (NPDES) permit, and with Title 22 requirements for recycled water production.

“If these results are confirmed, the industry could significantly lower operations and maintenance costs by implementing this new coarse monobed configuration,” said Verma.

A team of Kennedy/Jenks engineers, including Mike Joyce, Mark Minkowski, Mike O’Neil, Lily Zhu, Craig Thompson, Joe Drago, Val Frenkel, Darija Borkovic, and Anna Yen, began analysing the SBSA’s dual-media filters in 1998 in hopes of improving their performance.