SEKRENS

Secondary purification with chemical precipitation: Optimization with process control, oxidation processes and biofilm processes in small partial streams.

Main objective: Verify possibilities for achieving the secondary treatment requirement in mechanical-chemical wastewater treatment plants, through optimization of the precipitation step in combination with advanced oxidation processes.

The Norwegian Environment Agency has required many mechanical-chemical treatment plants with discharges from the Swedish border to Lindesnes (sensitive areas) to take measures so that the secondary treatment requirement in the Pollution Regulations is satisfied. The Directorate plans to continue the requirement to also apply to normal areas with particularly sensitive freshwater recipients. Mechanical-chemical treatment plants remove phosphorus and particulate organic matter well, but dissolved organic matter less well. A secondary treatment requirement can therefore lead to the need to expand many treatment plants with a biological treatment stage to better remove dissolved organic matter. Establishing biological, in addition to mechanical-chemical cleaning, entails a significant additional cost for the facilities. Certain facilities, however, have experience that it is possible to achieve the secondary purification requirement for longer periods, without using biological processes.

In this project, the aim is therefore to analyze alternatives for establishing biological cleaning processes in the main stream, namely:

1. Advanced management of the precipitation process via real-time monitoring and control that almost complete removal of colloidal and particulate organic matter can be achieved

2. Switch to new and more efficient precipitation chemicals

3. Treat a substream of incoming wastewater or a sludge stream with biofilm processes.

4. Establish post-treatment with chemical oxidation processes

The SEKRENS project’s ambition is to analyze each of these alternatives or combinations of them with a view to achieving the Norwegian Environment Agency’s requirements in a cheaper way than introducing a biological step in the main stream. This could save Norwegian society several hundred million kroner in investment. Søndre Follo treatment plant (Vestby) has received requirements for secondary treatment and is collaborating with DOSCON AS, SET AS and NMBU in the project. The project includes a subject that concerns many treatment plants that have received, or will receive, secondary treatment requirements with a short implementation deadline. It will therefore be appropriate to communicate the project’s positive results along the way. The project group plans to present the project’s results through dissemination activities, e.g. under the auspices of Norsk Vann, the Norwegian Water Association, etc. The results will also be interesting for the European water industry. The project’s ambitious activities expect valuable results of interest to international researchers and user groups, and therefore the aim is to present in international conferences, e.g. under the auspices of IWA (International Water Association) and EWA (European Water Association).