Kinetics of biofilm growth and substrate uptake in model drinking water systems.

摘要

The effects of different substrates on kinetics of biofilm growth and substrate uptake in model drinking water systems were investigated. Biofilm were grown using rotating annular reactors at 20°C and influent substrate concentrations from 500 to 2000 mug C/L. Substrate groups were amino acids, carbohydrates, humic substances and a mix of the three (mixed substrates). Two reactors were operated in parallel; one was the control and the other was chlorinated.; Growth rates were determined using three methods: (1) mass balance for biomass and substrate across reactors, (2) batch cultures using suspended biofilm cells and, (3) uptake of 3H-leucine by attached biofilm on reactor sample slides. Substrate uptake and yield were evaluated for biofilm in reactors and batch culture.; Specific growth rates based on mass balances for chlorinated reactors were greater than for the control. Chlorinated reactors using carbohydrates or mixed substrates had growth rates greater than for amino acids and humic substances. Growth rates based on mass balance for the control reactor biofilm were statistically the same for all substrates except humic substances, which had the lowest growth rate.; Kinetic parameters determined using biofilm cells in batch culture did not generally apply to biofilm in reactors. Removing cells from the biofilm structure alters important parameters such as mass transfer, impact of nutrients that attach to the biofilm matrix, cell physiology, and the influence of chlorine.; Growth rates determined using leucine uptake were comparable to those based on mass balance for control reactor biofilm, but much less than mass balance based growth rates for the chlorinated biofilm. Chlorination may influence the ability of biofilm cells to utilize amino acids such as leucine.; Fractional carbon removal across reactors was constant by substrate and reactor type over the range of substrate concentrations used. Substrate uptake normalized to biomass was greater for chlorinated biofilm than for control. Yield was less for chlorinated biofilm than for control. Although chlorination reduced biomass in the biofilm, the biomass had greater rates of growth and substrate uptake than in the control. Lower yield in chlorinated biofilm may indicate biofilm cells' need to produce additional exopolymeric substances.