Danish water utility finds solutions for diluted raw sewage
Following heavy rain overloading the combined sewer systems, diluted raw sewage can potentially overflow to nearby lakes, rivers and seas.
Previous solutions have included separating rainwater and sewage, or the establishment of detention ponds, but these require significant investment.
In a move that could reduce phosphorus discharged into the environmentally sensitive “Swan Lake” from stormwater runoff by 90 percent, Danish water utility Skanderborg Forsyningsvirksomhed upgraded an existing wastewater treatment plant.
Using SUEZ’s Extreme Rate Clarifiers, known as Densadeg XRC for tertiary treatment, the project will serve as the first public global technology reference for this type of application.
A high-rate settling process, the clarifiers use solids contact, ballast addition and solids recirculation to provide enhanced deposition of solids.
The process removes polymer and iron chloride binding phosphorus to solids. Then anthracite is added to ensure a high degree of condensation, which is extracted from the water through lamella separators.
Two lines of Densadeg XRC are used to ensure operation during normal times and during peak flows. Here the utility can experience up to three times normal load, such as during the week of the Skanderborg Festival or extreme rains, which can occur between 10 and 15 times a year.
A video below shows the XRC process: