Cutting phosphorus levels in wastewater effluent

In Sweden, treated water from the Sundet wastewater treatment plant has historically been released into the Norra Bergundasjön lake. Due to a very sensitive lake, a significant reduction in phosphorus was required.

DynaSand® filters offer a very effective solution that enabled the plant to significantly reduce phosphorus levels below some of the most stringent targets. The DynaSand filters have consistently delivered lower phosphorus content than the 0.2 mg/l consent, with effluent concentrations regularly below 0.1 mg/l.

“The DynaSand system has enabled the treatment plant to reach some lowest consent levels in the world. We have even achieved annual averages of 0.05 mg/l, an almost perfect result for the environment.”

Mattias Feldthusen, Director Product Management, Water Treatment Solutions

The challenge
The community of Växjö in southern Sweden faced considerable environmental issues caused by excessive phosphorus levels in the local lake systems. During the planning of a new wastewater treatment plant a new filtration stage was required to ensure the effluent passing into the lake would achieve phosphorus levels below 0.2 mg/l. As one of the lowest consent levels in the world, achieving this target was a considerable challenge using the technology available.

The solution
Phosphorus is removed in two stages. First, chemical precipitation and sedimentation, then in-line precipitation that significantly removes phosphorus by filtration through continuous sand filters. In this case, 60 DynaSand filters are divided into six separate treatment lines, one of which is used for development of new processes. The solid phosphates are removed by passing the sand through an integral sand washer.

Customer benefit
The filtration system is designed to handle a maximum flow of 3’000 m³/h, which ensures the equipment is not overwhelmed, even during high flow rates. The real benefits are experienced by the environment, especially the local lake, which now has a thriving aquatic ecosystem.

As a continuous flow system, there is no downtime for cleaning and no operator intervention is required, saving time and money for the municipality.