Pollution Engineering - April 2009 - (Page 35) Primary Factors for Activated Sludge in Industrial Applications Activated sludge applications have been used by Activated sludge applications have been used by municipalities for some time. Perhaps more industrial applications should be taking a look at this technology. By DR. WESLEY ECKENFELDER, technical director, AquAeTer Inc. ver the years, many models have been developed to define the performance of the activated sludge process. Most of these have related to municipal wastewater systems. However, the recent Eckenfelder model targets a multi-component basin in industrial wastewater. The primary factors that define the design of an activated sludge process treating industries’ wastewaters are (1) the active biomass under aeration, (2) the biodegradability of the organic mixture, (3) the aeration power density, and (4) the temperature in the aeration basin. The biomass undergoes endogenous respiration in the aeration tank, and as a result the active fraction of the biomass decreases as a function of sludge age. This is shown in Figure 1. O Aged sludge Figure 1 The active fraction of the biomass decreases as a function of sludge age. The influent degradable volatile suspended solids (VSS) are degradable as a function of sludge age. For example, primary VSS in municipal wastewater will be essentially completely degraded in a sludge age of 10 days. Influent non-degradable VSS will accumulate in the mixed liquor as a function of sludge age. This will reduce the active biomass so that it is essential to reduce the primary influent VSS as much as possible. Most industrial wastewaters are composed of multiple organics with variable degrada- tion rates and concentrations. Under acclimated conditions, these organics will degrade at different rates. The total concentration in terms of biological oxygen demand (BOD) or chemical oxygen demand (COD) will follow a pseudo first order reaction. In the complete mix mode, the BOD removal rate is proportional to the fraction of BOD remaining under aeration since the degradability decreases with concentration. APRIL2009 www.pollutionengineering.com 35 http://www.pollutionengineering.com
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