How does the sewage treatment process work?
Gravity helps sewage flow through the mains to the treatment plant. When sewage first reaches the treatment plant, the influent spiral lift pumps raise the sewage to the elevation of the treatment plant. Then it passes through a bar screen which catches large objects and empties into grit tanks. Huge blowers aerate the liquid in these tanks. Scrapers and chain and bucket collectors remove the grit (sand) which settles to the bottom of these tanks. Next, it is on to the primary clarifiers. The flow is slowed in these tanks to allow the sludge to settle to the bottom. Then a chain and flight system, similar to the apron in the bottom of a manure spreader, pushes the sludge to one end to be pumped to the anaerobic digesters. The anaerobic digester allows bacteria to break down the sludge in a closed container without oxygen. The aeration tanks, which are where the liquids from the primary clarifiers go next, allows the bacteria to break down the sewage in an oxygen environment. Liquid flo
