Bio scrubber technology

Abstract

Waste gases from food, animal and fish feed industries, rendering plants, chemical production, composting plants, waste handling and wastewater treatment processes, produce undesirable odors, which contribute significantly to atmosphere icpollution. In wastewater treatment plants (WWTP s), odors are mainly generated during anaerobic biodegradation of sewage. Other odors associated with WWTP s come directly from industrial wastewater-containing solvents, petroleum derivatives, and volatile organic compounds (VOC s). Odors are generated by a number of chemical components, the most significant beingthe sulfur compounds, hydrogen sulfide (H2S) and mercaptan (Burgess et al.2001). Domestic sewage contains 3-6 mgl1 of organic S, mainly arising from proteinaceous materials, about 4 mgl1 of sulfonates arising from household detergents, and 30-60 mg inorganic sulfur as sulfates. While nitrogen-basedodor compounds and the organics associated with wastewater treatment are important, H2S is the predominant odor-causing compound, and is also corrosive to mild steel and concrete (Jensen and Webb 1995).In order to mitigate the nuisance impact, odorous emissions generated at the open sources such as inlet works, primary sedimentation units, aeration tanks, final clarifiers, sludge processing units, and wastewater channels are being contained by covering and conveying the waste gas for treatment before discharging to the open atmosphere. Industrial waste gases have traditionally been treated by physico-chemical methods such as condensation adsorption, absorption, scrubbing, and oxidation. Selection of a particular technology, or combination of technologies, is dependenton factors such as site characteristics, treatment objectives, waste gasairflow rates and characteristics, and concentration of odorous compound. Various technologies available for the treatment of odors and air pollutionare described in Table 8.1. Physical removal is typically by adsorption or absorption. However, physical processes only transfer the VOC s to anotherphase (solid or liquid), which still requires treatment or disposal. Chemical removal is typically mediated by thermal or catalytic oxidation. In biological systems, the pollutants diffuse into the liquid phase where microorganisms degrade them into CO2 and H2O. Biological waste gas treatment has become an attractive, new treatment alternative in the last two decades(Ottengraf and Diks 1992; Shareefdeen and Baltzis 1994; Edwards and Nirmalakhandan1996; Kennes and Thalasso 1998; Burgess et al. 2001). Threemajor bioreactor designs are usually considered for the treatment of air pollutants, i.e., the bio filter, the bio trickling filter, and the Bio scrubber, although other design alternatives have been proposed (Ottengraf 1987; van Groenestijn and Hesselink 1993; Kennes and Thalas so 1998; Share efdeen et al.2002). © Springer-Verlag Berlin Heidelberg 2005.