The first reason for getting rid of wastewater solids is the significant energy savings.
When you decrease the solids, you decrease the organic load. As a result there is reduced need for aeration.
Aeration stimulates growth of aerobic bacteria which consume most of the residual organic materials. Less organic matter means less aeration and less energy to run the pumps.
Sometimes there is more than a 50% reduction in expended energy.
Another benefit of removing solids is a significant reduction in CO2 generation from microbial activity. The removed primary sludge that is also has value as bio fuel.
The second reason is that removal of solids cuts down hauling inert secondary sludge to the landfill.
This provides cost savings in transportation and landfill fees.
The third reason to remove solids before treatment is to increase plant capacity without spending money.
It can eliminate the expense of upgrading aeration tanks. Less organic matter enables the plant to process higher volumes of wastewater in the secondary step with less maintenance.
The fourth reason to reduce solids is to enhance membrane performance in the secondary treatment.
Although membranes represent a significant innovation in treatment, they lose effectiveness with the conventional primary process.
When there are a lot of solids entering the secondary process, including fiber, plastic, paper and vegetable waste, the membranes become clogged, work harder and eventually fail.
Removing solids would eliminate fouling, extend membrane life and reduce maintenance costs.
Before the wastewater arrives at the treatment plant, it flows through screens in the sewage tunnels that capture large solid materials.
After arrival at a treatment facility, there are two new methods that efficiently remove solids at a high rate.
One of these is Chemically Enhanced Primary Treatment (CEPT) and the other is mechanical separation.
The CEPT process adds metal salts and polymers prior to the wastewater entering the primary tanks.
Contrary to conventional separation which removes only the readily settled and floating matter, CEPT will coagulate and flocculate all the organic solids into a removable sludge.
Mechanically enhanced removal of solids is an efficient redeployment of existing components.
Fine screening, grit removal, flow equalization and clarification all occur in one primary process tank.
Larger utilities have successfully incorporated the CEPT process. The Flatline ™ enhanced mechanical process requires less horsepower and works better for smaller facilities.
Wastewater treatment plants that aspire reduce their use of energy, emissions and cost, are bringing these enhanced treatments online.
In time, plants may become self-sufficient by using biogas derived from the primary process to power the plant.
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