Flocculation prior to the belt filter - France - Case Study
Cazaux sewage treatment plant - wastewater sludge flocculation
Cazaux - FRANCE (33)
This plant uses a biological treatment process, “extended aeration activated sludge”, followed by a water clarifier. The sludge is treated by a belt filter, which produces a product consisting of 83% water and 17% dry matter.
Flocculation is used to improve the mechanical sludge dewatering process. Without good flocculation, the sludge cannot be mechanically thickened and dewatered using a belt filter.
When continuously mixing polymer powder, a precise water/powder ratio is required and there is a risk of lumps forming if the powder wetting and mixing process is not adjusted to the correct and optimal setting.
The Cazaux plant has a 5,000 population- equivalent capacity and was commissioned in 1987.
In order to increase efficiency, Eloa Bay (Arcachon) opted for a liquid polymer to treat their sewage sludge. To do this, they had to modify the existing polymer mixing unit by removing the powdered polymer mix and integrating a Dosatron proportional pump that was specifically adapted to the polymer.
They chose a polymer dosing pump that mixes the polymer with the water to obtain a homogenous solution for maturing the sludge before it is sent to the belt filter.