Submitted to: Journal of Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 22, 1999
Publication Date: N/A
Interpretive Summary: There is a tremendous need to treat textile wastewaters cost effectively. Most conventional treatment methods remove the dyes that contaminate these wastewaters inefficiently. We previously devised a technology that uses chemically modified biomass (plant residue matter) to remove dyes from wastewater. Now, to make this technology more cost effective, we have developed a method that relies on bacteria to break up the dye and allow the biomass to be used many times. The natural ability of certain bacteria to digest dyes when they lack oxygen was harnessed for the task of cleaning off the dye from the biomass. This new procedure lessens the cost of regenerating the dye-binding capacity of the biomass and minimizes the environmental impact of the process. The technology can be incorporated into certain existing types of wastewater treatment systems. Engineers can use this information in the design of new treatment facilities for textile mills.
Technical Abstract: Cellulosic strong anion exchangers are very effective for decolorizing textile wastewaters. However, the high affinity of dyes for the adsorbent make regeneration with conventional eluants impractical. Previous work demonstrated that chemical reduction of azo dyes bound to cellulosic anion exchangers facilitates adsorbent regeneration. The present study examines whether microbial azo-reductase activity could substitute for inorganic reductants. Anaerobic suspensions of Burkholderia cepacia NRRL B-14803 were tested for their ability to reduce two monoazo dyes, Orange II and hydrolyzed Remazol Red F3B, in a variety of reactor configurations. Inclusion of anthraquinone-2-sulfonate in the reaction medium greatly increased dye reduction rates, as did increased temperature and bacteria concentration. By physically separating the bacteria from the dye adsorbent using a reactor in which the bacteria were confined to a dialysis tube, it was demonstrated that anthraquinone-2-sulfonate mediated the transfer of reducing equivalents from bacteria to adsorbent-bound dye. Furthermore, anaerobic B. cepacia suspensions can drive a large fraction of anthraquinone-2-sulfonate to the reduced state, in the absence of dye, within a 6-hr incubation period. These observations suggested that a spaciotemporal disconnection of the process of adsorbent dye reduction from the azo-reductase activity of bacteria would be feasible. This possibility was confirmed by regenerating an ion exchanger bed with dialysate from a separately housed anaerobic reactor.