Reducing Sludge Formation in the Activated Sludge Process
The activated sludge process was discovered by Ardern and Lockett in the years 1913– 1914. In the slightly more than 100 years since its discovery, it has become the most widely used process for the biological treatment of both domestic and industrial wastewaters in developed and developing countries. At its most basic, the process consists of an aerated reactor basin connected to a settling unit. The effluent stream leaving the reactor enters the settling unit where particulate matter settles under the action of gravity to the bottom of the unit. From here, it can be recycled into the reactor unit. The recycling of particulate matter is the key to improving the efficiency of the process, as enmeshed within it are micro-organisms. This particulate matter is known as sludge and consequently sludge is good. However, too much sludge is bad; disposal of excess sludge can account for between 50 and 60% of the typical operating costs of the activated sludge process.This chapter provides a historical overview of the activated sludge process and two methods for reducing the amount of sludge: disintegration through the use of a sludge disintegration unit and a biological approach based upon the use of predators that graze upon the sludge.
KeywordsActivated sludge process Predation Sludge reduction
The author thanks the organizers of the Forum “Math-for-Industry” 2016 for the invitation to give a presentation at the workshop “Agriculture as a metaphor for creativity in all human endeavors” (Queensland University of Technology, Brisbane, Australia; November 21st–23, 2016).
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