Characteristics of and selection criteria for support materials for cell immobilization in wastewater treatment

For treatment of wastewater with immobilized cells, support materials need to meet the following criteria: insoluble, not biodegradable, high mechanical stability, high diffusivity, simple immobilization procedure, high biomass retention, minimal attachment of other organisms and preferably a low cost price. In order to compare which support materials are the most suitable, characteristics of several natural and synthetic materials have been determined. For this, both literature and experimental data were used. The immobilization procedures of natural gel materials, like alginate and carrageenan, are mild and cells grow well in these supports. Furthermore, the effective diffusion coefficients of substrates are close to those in water. These supports, however, appeared to be soluble, biodegradable and liable to abrasion. Synthetic gels, on the contrary, have better mechanical properties, but mostly lower substrate diffusion coefficients. Immobilization conditions are less mild resulting in low biomass retention. For application of entrapped nitrifying cells in wastewater-treatment systems synthetic gels, however, are promising.