The Role of Micro-organisms in wastewater treatment
There are two types of microorganisms at work in an activated sludge sewage treatment plant. They both work to clean the water and produce energy:
Aerobic bacteria work on the raw sewage in the presence of oxygen to produce carbon dioxide and more bacteria. Sewage contains fecal matter and organics such as food waste, ammonia, soaps, oils, carbohydrates, and protiens. To humans this is waste. To aerboic bacteria it is food. Essentially they “burn up” the sewage with their metabolic processes. Going into the aerobic chambers the waste water contains fecal matter and dissolved organics. Leaving the area it contains only microbes and water. Next the flows are separated by gravity into clean water and the heavier microbes. The clean water is treated further so it can be use for irrigation, and the microbes are returned to the front of the plant to do it all over again. sent off for recycling or disposal.
The collected aerobic bacteria are directed into anaerobic (no air) digestors where a colony of anaerobic bacteria live, The anaerobes eat the aerobic bacteria reducing them to methane which is burned to power the plant and an inert organic mass which can be disposed of by incorporation into the soil or incineration. CAWD disposes of its bisolids by application to cotton fields in southern California.