Physical stability and biological activity of biofilms under turbulent flow and low substrate concentration
نویسنده
چکیده
The paper focuses on bio®lms subject to turbulent ̄ow and high liquid velocity (of the order of 1 m s) which can be found in heat exchangers, water distribution systems and in some wastewater reactors. An overall model describing bio®lm development is presented, which includes the effects of biomass detachment due to the hydrodynamic forces. A methodology for estimating substrate consumption from data obtained through continuous monitoring of bio®lm growth is presented. Results show that the physical stability of the bio®lm increases with the liquid velocity, while the rate of substrate consumption decreases. List of symbols 1/b (s) mechanical strength of the bio®lm Jp (kgbio®lm/m 2 s) bio®lm production ̄ux Jr (kgbio®lm/m 2 s) bio®lm detachment or removal ̄ux Kp (W m )1 K) thermal conductivity of the perspex wall Kf (W m )1 K) thermal conductivity of the bio®lm mf (kgbio®lm/m 2 bio®lm) mass of bio®lm per unit surface area mf * (kgbio®lm/m 2 bio®lm) maximum mass of bio®lm per unit surface area mfa (kgactive layer/m 2 bio®lm) mass of active layer per unit surface area Rf (m 2 K W) thermal resistance of the bio®lm t (s) time T1 (K) temperature of thermocouple 1 T2 (K) temperature of thermocouple 2 T3 (K) temperature of thermocouple 3 U (W mK) overall heat transfer coef®cient YX/S (kgbiomass/kgsubstrate) biomass yield Greek symbols (lp (kgbio®lm produced/ bio®lm speci®c production kgbio®lm on the surface s) rate (lp)a (kgbio®lm produced/ bio®lm speci®c production kgbio®lm on the surface s) rate of the active layer qf (dry kgbio®lm/m 3 bio®lm) dry density of the bio®lm (dry mass per unit volume) qf (wet kgbio®lm/m 3 bio®lm) wet density of the bio®lm
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