Biotrickling Filter and Chemical Scrubber Combination Meets Perth's Stringent Odor Control Requirements

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 H2S as high as 80ppm to less than 0.5ppm. Odor reduction was 99 percent with an outlet odor of 700OU. Data collected during the 10-day performance test of the chemical scrubbers showed inlet H2S as high as 37ppm reduced to less than 0.05ppm. 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 operated in polishing mode with lower inlet loads.