Some high BOD industrial effluents also contain recalcitrant pollutants such as halogenated organic compounds and synthetic dyes. Advanced biological processes using both general microorganisms and specially adapted bacterial strains to remove both BOD and the specific pollutants are being actively researched. Immobilization of special bacterial strains with general microbial cells is the essential step to prevent the loss of biodegradation capability in a continuous flow wastewater treatment process. Immobilization of microbial cells can also offer other advantages such as shorten hydraulic retention time, smaller reactor volume, and better flexibility for environmental fluctuation. Among various immobilization methods, adsorptive immobilization is a common way for biological wastewate...[ Read more ]

Some high BOD industrial effluents also contain recalcitrant pollutants such as halogenated organic compounds and synthetic dyes. Advanced biological processes using both general microorganisms and specially adapted bacterial strains to remove both BOD and the specific pollutants are being actively researched. Immobilization of special bacterial strains with general microbial cells is the essential step to prevent the loss of biodegradation capability in a continuous flow wastewater treatment process. Immobilization of microbial cells can also offer other advantages such as shorten hydraulic retention time, smaller reactor volume, and better flexibility for environmental fluctuation. Among various immobilization methods, adsorptive immobilization is a common way for biological wastewater treatment. Immobilization by cell aggregation with alum flocculation and adsorption on three types of supports were investigated in this work.

Siran beads, cellulose sponges and poly vinyl alcohol (PVA) carriers were employed to investigate the essential conditions for the microbial attachment in bench-top bioreactor and flask cultures. In order to promote biofilm formation on supports, a carrier either in irregular shape or with cavities is preferable. Although thick biofilms will increase biomass concentration in a bioreactor, they may result in mass transfer limitation and hence decrease the specific degradation rate. The problem of thick biofilm formation as well as channelling and clogging in a packed bed reactor could be solved by fluidizing the carriers with recirculation of water through the reactor. For a good dye removal efficiency in a biological process, large pore-size carriers with thin biofilm is suggested. More than 70% microbial activity was lost in cell aggregates formed with alum flocculation. The methods of immobilization by alum-promoted cell aggregation is not recommended.