Biodegradation process attack

Aerobic biodegradation processes often show unsatisfying results because a number of azo dyes are resistant to aerobic microbiological attack. The main process for removal of dyes in the aerobic part of a CWWT is based on an adsorption of the dyes on the biomass. Further problems in the destruction of chromophores result during the treatment of phthalocyanine dyes, anthraquinoid dyes, and vat and sulfur dyes, which contain rather persistent chromophores. 

The biodegradation processes of both xenobiotics such as aromatic compounds, plastics, such as poly(vinyl alcohol), polyesters, poly-(ethylene), and nylon, as weU as pol5mciers with biological origin, and blends of both types have been reviewed (3). S5mthetic materials with groups susceptible to hydrolytic microbial attack have also been dealt with. 

In this process, which has been in existence as a concept for at least 30 years and is often referred to as a microbial process, chemolithiotrophic bacteria in aqueous suspensions in the presence of oxygen can be nsed to selectively attack the sulfur crosslinks in the snrface of waste rnbber crumb particles. The process can also be regarded as a type of biodegradation process, the by-prodncts of which can inclnde elemental sulfur, sulfates, sulfides and snlfnric acid. Specific examples of the bacteria that have been used to devulcanise rubber in this way inclnde species of Thiobacillus, e.g., T. thiooxidans. 

To increase the usefulness of bioremediation as an effective field remedial tool, significant investments have been made towards the development of means to remove sorbed PAHs, attack sources of NAPL, and subsequently increase the aqueous solubility/bioavailability, and thus the biodegradability, of targeted compounds. To date, one of the most effective ways to accomplish these tasks involves the use of surface active agents (i.e., surfactants). A variety of synthetic surfactants have been shown effective in increasing the bioavailability of PAHs and other hydrophobic contaminants (Kile Chiou, 1989, 1990 Edwards et al., 1991 Liu et al., 1991). Although the solubilization process is not completely understood, these studies showed that a variety of ionic and nonionic surfactants could significantly increase the water solubility of monitored chemicals. 

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