In 2016, Zuvamesa converted its wastewater treatment plant from an aerobic to an anaerobic digestion process, in order to generate biogas. The biogas is used within the plant to substitute for natural gas combustion. The system used is a Downflow Anaerobic Carrier System (DACS), whose main advantage is the use of carriers as media for the microorganisms’ attachment. As a result, the performance of this system is greater than that of conventional anaerobic systems. The efficiency of Zuvamesa’s system is 85%. The AD plant processes 25 mT COD per day, and each year generates biogas equivalent to 6.5 GWh. There has been a 20% reduction in overall natural gas consumption as a result of the investment. The investment in the AD plant of between 800,000 and 1 million euros took about four years to pay back through savings on energy bills.
Figure 1: Waste water treatment and anaerobic digestion plant at Zuvamesa’s juice factory, Valencia, Spain (Source: Zuvamesa)