ABSTRACT
Biotreatment of industrial pollutants can be performed by their hydrolysis, solubilization, precipitation, volatilization, oxidation, or reduction. The donors of electrons in oxidation–reduction reactions are: (1) organic compounds; (2) reduced inorganic substances such as H2, H2S, S, NH4 +, and Fe2+; (3) H2O in oxygenic photosynthesis. Acceptors of electrons in oxidation-reduction reactions are: (1) a part of the organic molecule in fermentation; (2) NO3 -, NO2 -, Fe3+, SO4 2-, CO2, organic compounds in anoxic respiration; and (3) O2 in aerobic respiration. Co-metabolism is the simultaneous biodegradation of a hazardous organic or inorganic substance that is not used as a source of energy but which is stereochemically similar to another substance, which does serve as a source of energy for microbial cells. To intensify the biotreatment of the hazardous waste, the following pretreatments can be used: (1) mechanical disintegration or suspension of the hazardous hydrophobic substance to improve the reacting surface; (2) removal of the hazardous substance from wastewater; (3) preliminary advanced oxidation of the hazardous substance. A simple way to produce a suitable microbial inoculum is the production of an enrichment culture, which is a microbial community containing one or more dominant strains naturally formed during cultivation in a growth medium modeling the hazardous waste under defined conditions. Genetic engineering of microbial strains can be used to create the ability to biodegrade xenobiotics or to amplify this ability through the amplification of the related genes. Another approach is the construction of hybrid metabolic pathways to increase the range of biodegraded xenobiotics and the rate of biodegradation. Self-aggregated microbial cells of biofilms, flocs and granules, and artificially aggregated cells immobilized on solid particles are often used in the biotreatment of hazardous wastes. A tutorial with solutions and a quiz bank are added to this chapter.
