Performance Testing of a Biotrickling Filter/Chemical Scrubber Odor Control System at Western Australia's Largest WTTP

In 2006 the Water Corporation of Western Australia formed the W2W Alliance (W2WA) to deliver a five-year 352 million program of upgrades to the State's three largest metropolitan wastewater treatment plants (WWTPs). At the Woodman Point WWTP, W2WA was tasked with installing best practice odor control to achieve a 50 percent reduction in odor emmissions. The Stage 1 odor control improvements involve new covers of the grit tanks, sealing existing covers at the primary treatment area, and new covers and extraction systems for sludge treatment areas and SBR anoxic zones. Biotrickling filters followed by chemical scrubbers offered the best solution for treating the extracted air. The Stage 1 commissioning in 2009 was very successful with no odor incidents during startup of the facilities. The biotrickling filters acclimated faster than expected and reduced inlet hydrogen sulfide (H2S) as high as 80 parts per million (ppm) to less than 0.5ppm. Biotrickling filter performance testing showed outlet odor ranging from 1,020 to 3,160 Odor Units (OU), which met the requirment of 5,000 OU. The odor reduction goal of greater than 95 percent was also achieved. Chemical scrubber performance testing showed inlet H2S as high as 37ppm reduced to less than 0.05ppm, which met the 0.1ppm requirement. Odor removal was relatively good, but some stack outlet samples were above the 1,000OU goal. When the combined system is tested, it is expected that the outlet odor goal can be met when the chemical scrubber is receiving lower inlet loads.