21 Years of O&M Experience with Hybrid Anaerobic Treatment
In 1983, the NutraSweet Company (NSC) commissioned a hybrid anaerobic treatment system for treating the high-strength wastewater at the site. The anaerobic treatment system has operated continuously from start-up in 1984. The anaerobic treatment facility consists of two upflow reactors with an open or suspended-growth zone in the lower section of the reactor and structural media in the upper part of the reactor. In 2002, a study showed that the hydraulic retention time in both anaerobic reactors had declined significantly. In 2003, NSC decided to remove an anaerobic reactor from service to enable it to be inspected and rehabilitated. The rehabilitation consisted of removing and replacing the media, removing and dewatering sludge, replacing the internal piping, and reseeding the reactor. The project required approximately five months to complete. The rehabilitation of the anaerobic reactor improved the COD removal from 63% observed before the shutdown to 93% observed after start-up of the rehabilitated reactor.