Optimization of Activated Sludge Diffusion for Hydrogen Sulfide and Volatile Organic Compounds Removal

Abstract

A combination of design configurations (tall vs. short aeration tanks and coarse vs. fine air diffusion) was tested at pilot scale for optimum H 2 S removal by activated sludge diffusion (ASD). The effects of H 2 S diffusion on the wastewater treatment performance, in terms of biological oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS) and ammonia (NH 3 ) removal, were also evaluated, in eight four-week trials. The results showed that although all combinations of configurations gave 85 − 100% removal of up to 25 ppmv H 2 S, a combination of fine bubble diffusers in tall or short tanks gave the best results with regard to H 2 S removal (94 and 99%, respectively). This suggests that aeration tank height has no impact on H 2 S removal when using fine bubble diffusers. However, tank height was important in the configurations with coarse bubble diffusers, with 85% removal being obtained for a short tank and 99% for a tall tank configuration. The configuration with fine bubble diffusers in short tanks gave best treatment performance (75, 72 and 80% mean removal rates for BOD, COD and NH 3 , respectively, at the highest dosing period, compared with 72, 71 and 68% for the control). A brief suspension in nitrification was observed soon after commencement of ASD of H 2 S in the configuration with fine bubble diffusers in tall tanks and that with coarse bubble diffusers in short tanks. The configuration with fine bubble diffusers in short tanks also gave the best mixed liquor suspended solids (MLSS) maintenance and was therefore chosen for further studies to investigate removal of H 2 S peaks of up to 150 ppmv. These studies showed no effects of H 2 S diffusion on the wastewater treatment performance, when the plant was fully stabilized and the microbial biomass was well acclimated.

Applying odor control technologies using reliability and sustainability criteria – examples of full-scale outcomes

“…The bio-trickling filter system is reduced because a portion (the most odorous foul air) is first treated in the activated sludge reactors. The plant utilizes fine bubble diffusers in the activated sludge reactors, which have proven to be much more effective than coarse bubble diffusers at removing odorous compounds (Barbosa et al, 2004).…”