Challenge
Dairy facilities in Tulare—including Nestlé-Dreyer’s, Saputo Cheese, Kraft USA, and Land O’Lakes—produce large volumes of high-strength industrial wastewater, which is sent to the city for treatment. In 1989 the city selected an ADI-BVF® anaerobic digester as an efficient means of treating the wastewater to meet state regulations. This technology allowed Tulare to comply with the discharge limits, but also carried the additional opportunity of converting waste to energy as part of the anaerobic treatment process.
Energy conservation is extremely important to both the City of Tulare and the wastewater treatment facility. Since biogas can be used as fuel to generate electricity, the city wanted a means to reliably collect biogas from the BVF® reactor to recover the energy while also controlling odors and reducing greenhouse gas emissions.
Solution
To address the City of Tulare’s needs, Evoqua’s Geomembrane Technologies designed, manufactured, and installed a floating gas collection cover over the complete 4 acre surface of the city’s digester. The cover is designed to be gastight so that it contains all the biogas generated by the BVF reactor, thereby eliminating odors.
The cover is chemical- and UV-resistant to withstand the tough environment of the digester and the California sun. It is strong and stable, allowing personnel to walk across the BVF reactor for operations and maintenance. Rainwater that pools on the cover surface is collected and drained.
