Waste Water Treatment Plants
In 1980, Los Angeles began exploring alternatives to control the H2S concentration in the digester gas produced at the Hyperion Waste Water Treatment Plant (WWTP), which treats nearly 420 MGD, wastewater generating over 475 tons of raw sludge per day. The digester gas H2S concentration had to be controlled so that the SOx emissions from the on-site combustion of the gas could be kept within acceptable regulatory limits, allowing the gas to be burned on-site to generate steam for heat or electricity or sold to local utilities. The Stretford process was chosen for desulfurization and the plant went into operation in 1985. The next several years saw numerous problems arise, most concerning the inability of the unit to effectively treat higher levels of H2S and the plugging of the packed columns with solid sulfur. Hyperion spent many years trying to solve the problems but met another obstacle — the vanadium catalyst used in the Stretford process. Vanadium in the sulfur cake was making disposal increasingly difficult and becoming an environmental problem, so the City decided to investigate alternatives.