Effects of cell entrapment on growth rate and metabolic activity of mixed cultures in biological wastewater treatment

The effects of cell entrapment on the growth rate and metabolic activity of mixed cultures in biological municipal wastewater treatment were investigated. Three different cell entrapment media (alginate, carrageenan and polyvinyl alcohol) and three cell-to-matrix ratios (2.5%, 5% and 15%, w/v) were examined. Free (non-entrapped) mixed culture cells were included in the study for comparative purpose. Results indicated that the entrapment, type of entrapment media, and cell-to-matrix ratio had significant effects on the growth and metabolic activity of the mixed culture cells. In most cases, polyvinyl alcohol entrapped cells had the highest specific growth and specific substrate utilization rates while alginate entrapped cells provided the lowest or second lowest rates. The specific growth and specific substrate utilization rates decreased as cell-to-matrix ratio increased from 2.5% to 5% or 15%. This study enhances the fundamental understanding about the physiological behaviors of entrapped cells in wastewater treatment environment. It provides results that are useful for increasing the performances of entrapped cells for wastewater treatment.