Sunlight-Blocking Covers Control Algae, Reduce Operational Costs at Santa Clara Utility

May 14, 2015
The Santa Clara Valley Water District of California's Penitencia water treatment plant underwent construction to replace chlorine primary disinfection with ozone. All of the cover styles would block sunlight and thus control algae, but the plant expressed a strong preference for structurally supported covers consisting of a retractable fabric sheet tensioned over supporting aluminum arches. As such, Geomembrane Technologies custom designed nine structurally supported covers for its tube settlers, which were especially prone to algae.

The Santa Clara Valley Water District of California had a vision for a "cleaner, greener, and leaner" operation. To help achieve this, its Penitencia water treatment plant underwent construction to replace chlorine primary disinfection with ozone. This would minimize chlorine feed at the head of the plant and reduce the formation of disinfection byproducts (DBPs). However, past attempts to reduce the chlorine feed resulted in significant algae growth -- a negative side effect that the plant was keen to fix.

(Left) GTI custom-designed nine structurally supported covers for the Penitencia plant's tube settlers. (Below) Aerial view of GTI's structurally supported covers at the Penitencia plant.

District staff knew that algae control and DBP reduction could be accomplished in two ways: either through the use of alternative oxidants to chlorine or by creating a physical barrier to block the sunlight that algae requires to grow. Both solutions are used effectively at water treatment plants, but the District ultimately chose basin covers because the cost could be recovered in about five years through hypochlorite reduction.

The District evaluated three types of basin covers: fabric, fiberglass and aluminum. All of the cover styles would block sunlight and thus control algae, but the Penitencia plant expressed a strong preference for structurally supported covers consisting of a retractable fabric sheet tensioned over supporting aluminum arches. This cover style would be the easiest for operational staff to access and maintain basins and tube settlers.

Geomembrane Technologies Inc. (GTI) custom-designed nine structurally supported covers for the Penitencia plant's tube settlers, which were especially prone to algae. The covers included special features requested by the plant and were designed to fit around the various pipes and light standards existing around the basin openings. The covers were installed in just four days, without having to take the basins out of service.

Operators were able to reduce chlorine feed even before the covers were completely installed. After installation, the covers helped plant operators reduce pre-chlorine feed by more than half. A small amount of chlorine is still used to provide coagulant aid and to control algal growth in uncovered portions of the treatment trains. When plant staff retracted the covers five months after installation, they found the tube settlers to be free of algae.

The Santa Clara Valley Water District is now well positioned to meet demand for a cost-efficient, reliable water supply produced in a more environmentally sensitive manner. In the first six months after installing the covers, the plant saved $24,000 from lower hypochlorite usage compared to the year before. The District is expected to recover the cost of the cover installation and save an additional $500,000 over the lifetime of the covers.

Geomembrane Technologies is exhibiting at AWWA's ACE15 expo in Booth 2016.

More WaterWorld Current Issue Articles
More WaterWorld Archives Issue Articles

Sponsored Recommendations

SmartSights WIN-911 Alarm Notification Software Enables Faster Response

March 15, 2024
Alarm notification software enables faster response for customers, keeping production on track

Automated Fresh Water Treatment

March 15, 2024
SCADA, Automation and Control for Efficient and Compliant Operations

Digital Transformation Enables Smart Water

March 15, 2024
During this webinar we will discuss factors driving the transformation to digital water, water industry trends, followed by a summary of solutions (products & services) available...

Automation for Water Treatment and Distribution Systems

Jan. 31, 2024
Dependable, Flexible Control Solutions to Maximize Productivity