Aerobic and anaerobic microbial treatment alternatives for shellfish processing wastewaters in continuous culture

Abstract

AbstractShellfish processing wastewaters were characterized and subjected to laboratory‐scale treatability investigations using continuous flow chemostats operated under both aerobic and anaerobic conditions with and without biological solids recycle. System operation and evaluation employed hydraulic retention time as the controlled variable with substrate removal and biomass production as dependent variables. Additional variables specific to anaerobic operation included total and methane gas production rate and volatile acids generation. Application of a kinetic model incorporating the Monod substrate concentration– growth rate function allowed estimation of kinetic coefficients μmax, kd, Y, and Ks.Aerobic treatment of the wastewaters could be adequately described by the kinetic model presented. However, total efficiencies were notably affected by the inherent morphological differences induced by changing hydraulic flows as reflected by poor solids separation at lower and higher retention times. Anaerobic treatment, although not amenable to kinetic description by the model and data presented, exhibited a limited potential for wastewater stabilization in that soluble substrate removals and methane production occurred at all retention times. Difficulties in successfully describing the system kinetically stemmed from an inability to quantify influent solids liquifaction rates. Moreover, evidence of some substrate associated inhibition of methanogenesis was apparent. Solids recycle tended to reduce the inhibitory influences and to increase treatment efficiencies in both the aerobic and anaerobic processes.