Part 8 of 8: Microbial Viability The last growth pressure that we will discuss in this series is the viability of the biological population. In many ways the quantity and quality of the aeration basin microbiological population is the result of the other growth pressures. The system will only contain as many bacteria as the [...]

Part 7 of 8: Temperature Another important growth pressure is temperature. The growth of microorganisms is a direct result of metabolic re-actions, most of which are catalyzed by enzymes. As with all chemical reactions, temperature has an effect on the rate of these reactions. As the temperature increases, so does the rate of reac ­tion, [...]

Part 6 of 8: Nutrients Microorganisms consume organic matter to get the energy they need for cell maintenance and reproduction. The bio ­chemical work done by the cell is called metabolism. Some of the molecules are broken down to provide energy. Others are used as building blocks in the manufacture of new cell parts, a [...]

Part 5 of 8: Retention Time and Flow Patterns Time is the bacteria’s friend. Long reten ­tion times reduce the system’s dependence on bacterial reproduction and reduce nutrient requirements. Retention time is also critical so that log growth can be completed and endogenous respiration is reached. This allows the soluble Biochemical Oxygen Demand (BOD) conversion [...]

Part 4 of 8: Dissolved Oxygen Dissolved oxygen is a critical growth pressure. The pres ¬ence or absence of dissolved oxygen determines the type of me ¬tabolism. Much has been written and discussed about the proper dissolved oxygen residual for Aerated Stabilization Basin (ASB) operation. The text book guidance for proper ASB residual is 1-2 [...]

Part 3 of 8: Toxicity and Inhibition The third growth pressure in this series that we will discuss is toxicity and its weaker counterpart, inhibition. In order for bacteria to thrive in a wastewater environment, the wastewater stream must be free of toxic or inhibitory compounds. Determining whether or not an influent is toxic or [...]

Part 2 of 8: pH In Part 1 of this series, we discussed the role of Biochemical Oxygen Demand (BOD) loading on biological activity in aerated stabilization basins (ASBs). In this article, we will discuss pH in the context of biological growth pressure. The pH of the environment has a profound effect on the rate [...]

Part 1 of 8: BOD Loading or Food Aerated Stabilization Basins (ASBs) are the most prevalent type of wastewater treatment system found in the Pulp and Paper Industry in the Southeastern United States. An overview of this type of system can be found in the EBS article “What’s the Difference – Aerated Stabilization Basins and [...]