Factors Contributing to Biomass Yield

Treatment and disposal of sludge from wastewater treatment plants have been estimated to account for about half of the 

Handbook of Membrane Separations Chemical, Pharmaceutical, Food and Biotechnological Applications 

Pirt s energy allocation model, in the form of Equation 28.2, is somewhat restricted for application in wastewater treatment. The value of p, the specific growth rate, is difficult to determine due to the variety of physiological states in the biomass and the variety of microbial species, each with different growth rates and substrate affinities. 

Pirt s formulation can also be written in terms of the utilization rate of the substrate (r ), which is the sum of that utilized by anabolism and that utilized by the biomass for maintenance requirements  

It is assumed that Yq and q f are constants for a given system, and it becomes apparent that the rate of biomass synthesis decreases as the biomass concentration is increased. It is, therefore, possible to achieve a state in which the amount of substrate provided is diverted entirely to the maintenance demand if the biomass concentration is sufficiently high and consequently a zero sludge yield is achievable. However, high biomass concentrations may not always be desirable from an operational perspective due to difficulties in meeting oxygen demand and the impact on the membrane fouling rate. 

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