Reusing residual water from the dairy industry can contribute to the water transition

The two dairy factories studied in Veghel and Borculo are located in the high-lying areas with sandy soils, a region that has had dry summers in recent years. It emerged from the project “Reuse of Residual Water from the Dairy Industry for Agriculture and the Water System” that the two factories produce enough residual water in theory to meet the irrigation needs of agriculture in the surrounding area during the summer months. If the residual water is reused as much as possible in the factory process, it can have a positive effect on the water system throughout the year. In addition, some of the residual water could be used to replenish the water system (indirect reuse).

Additional treatment required depending on the stream

It emerged from the study that the quality of the various residual water streams varies considerably. Residual water from reverse osmosis (RO permeate) proves to be most suitable for reuse because of the large volume and relatively low fouling burden. Additional water treatment is required for water reuse. If the water is for reuse in-house, a combination of coagulation, activated sludge treatment, ultrafiltration, RO, UV treatment and disinfection may be required.

Further research into the impact on the water system

Reusing residual water can reduce pressure on the groundwater system, which is extremely important during dry periods. The internal or external reuse of residual water can help to reduce demand for groundwater and reduce the pressure on drinking water supplies. Further research is needed to clarify the costs and benefits of water reuse and the precise effects on the regional water system. Important factors here are the availability of data about the volumes and water quality of the various residual streams.

Legal framework for the reuse of residual water

This study also shows that there is currently no appropriate legal framework for reuse: industrial residual water is not covered by the new EU regulation for the reuse of domestic wastewater for agricultural purposes. A clear and applicable legal framework is needed to make the large-scale reuse of industrial wastewater possible.