The Mendocino Wastewater Treatment Plant sits on a jutted-out piece of land on California’s north coast, overlooking Mendocino Bay to the south and Headlands State Park to the north.

This 35 mgd (average) activated sludge facility’s coastal location presents a unique challenge because the damp salt air tends to be corrosive, creating a higher propensity for damage to equipment. In addition, Mendocino County has to account for planned water shortages during dry summer months.

While these challenges are endemic to the location, the plant also must deal with clogs to pumps and other equipment caused by debris in the influent. “We always had a problem disposing of the debris that would come down through the collection system, plugging things up and causing problems in the clarifier,” notes Mike Kelley, former superintendent of the Mendocino City Community Services District.

The facility staff solved the debris problem by installing an Aqualitec Screentec vertical bar screen with an automated rake.

Scenic location

Mendocino County (population 87,000) stretches along the California coast between the Oregon border to the north and San Francisco three hours south. The area is attractive to residents and tourists seeking rest and recreation. This area is classified as the world’s largest temperate rainforest ecoregion, attracting visitors from all over the world to enjoy the dense redwood forest and breathtaking Lost Coast.

Team members at the wastewater treatment facility enjoy a stunning view of beaches, islets and cliffs. The Town of Mendocino was established in 1851, but the first water treatment facility was not built for another 120 years. Finally, in 1971, the Mendocino City Community Services District was created as a solution to the area’s wastewater and water issues. 

Dealing with debris

Without a bar screen, team members had to remove debris manually by entering the wet well, a dangerous and time-consuming process. Unless removed, the debris would clog and eventually damage pumps, costing up to $100,000 for replacement, an unacceptable expense for a relatively small community.

The Aqualitec Screentec bar screen proved to be a cost-effective solution, Kelley observes. The vertical bar screen filter system is designed to remove any solid objects from wastewater, while also protecting pumps and other downstream equipment from clogging.

The unit’s vertical design enables it to fit headworks, pump stations, lift stations, wet wells and manholes. A stainless steel rake collects debris at the bottom of the frame. The material is then ejected upward and prepared for disposal.

This screen was well suited for the Mendocino facility because it can be retrofitted for any well size. “It just fits right into our existing headworks without making any changes to the channel or to the concrete structure,” says Kelley. “It’s a perfect solution.”

The screen became the first level of filtration in the wastewater treatment process and extended pump life cycles while also improving the quality of treatment. With no moving parts at the bottom of the frame, it can safely be operated from the top. Looking back at the time he ordered the device, Kelley says, “It was like a eureka moment. It actually worked perfectly.”

Affordable and versatile

The bar screen’s design for versatility made Mendocino’s installation easy. The unit eliminated the risks of manual debris removal while protecting high-value equipment.

“After a short period of time using the bar screen, it was obvious that it was removing everything,” Kelley says. “We no longer saw any debris in the clarifier. It was a big deal because it reduced the manpower it took to clean up the clarifier. It has definitely cut down our costs and freed up manpower for other types of maintenance.”

The system has been a good investment, saving money and improving operating efficiency. Since installation in 2011, the facility has spent only $800 on maintenance fees. “The cost was low for the unit compared to many of the other ones I looked at,” Kelley says. “The Screentec unit doesn’t require much maintenance, and I expect it will continue to operate well for the district well into the future.”