Microorganisms immobilized in chitosan crosslinked with lignosulphonate for purification of waste water

Abstract

Microorganisms which may be in the form of homogenated anaerobic sludge are immobilized in a polymeric gel matrix containing chitosan and lignosulphonate. A mixture of chitosan solution and a microorganism is added dropwise to a solution of lignosulphonate to crosslink chitosan droplets and form beads of chitosan/lignosulphonate matrix membrane encapsulating the microorganism. Alternatively, the mixture is added to a water-insoluble organic phase to form chitosan beads in an emulsion, and to the emulsion is added a lignosulphonate solution to crosslink the beads and form a chitosan/lignosulphonate matrix membrane encapsulating the microorganism. In another embodiment, anaerobic bacteria in the form of granules are encapsulated in the chitosan/lignosulphonate matrix membrane and the membrane contains another bacterial specie(s). Waste water containing biodegradable polychlorinated aliphatic hydrocarbons is purified by contacting with microorganisms including anaerobic and methanotrophic species encapsulated in beads of the chitosan/lignosulphonate matrix membrane. Reductive dechlorination is effected by the anaerobic species and aerobic mineralization of intermediates is effected by the methanotrophic species which may produce methane monooxygenase.

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