Bioremediation may also involve aerobic or anaerobic microbial activities. Aerobic degradation often
involves introduction of oxygen atoms into the reactions mediated by monooxygenases, dioxygenases,
hydroxylases, oxidative dehalogenases, or chemically reactive oxygen atoms generated by enzymes such
as ligninases or peroxidases. Anaerobic degradations of contaminants involve initial activation reactions
followed by oxidative catabolism mediated by anoxic electron acceptors. The technique used to reduce
the mobilization of heavy metals from contaminated sites by changing the physical or chemical state of
the toxic metals is called immobilization. Solidification treatment involves mixing of chemical agents at