Reduction of pressure on groundwater through reuse of water from dairy plants in agriculture

Reuse of water and nutrients

Groundwater users are competing with each other for the available water, while the total demand for water is growing. The consumption of drinking water in the Netherlands is increasing as a consequence of a rising population. Moreover, the east of the country is battling drought, while the west is facing subsurface salinisation. To limit the negative impact of these problems as much as possible, drinking water utilities and Water Authorities want to accelerate the transition to a climate-robust water system. Climate adaptation is central to this transition.

The reuse of industrial residual water offers a possible solution to both drought and salinisation. Such water reuse would result in a net increase in groundwater availability for other purposes, such as drinking water production and for nature. Dairy farmers are faced with the consequences of drought, while dairy plants produce large quantities of wastewater. The reuse of this wastewater could allow for a considerable reduction in the volumes of groundwater abstracted for agriculture and horticulture, which at the moment amount to 664 million m³/year.

We currently do not know which water streams are available from dairy plants, nor what conditions would apply to their possible reuse.  By separating the different water streams from a plant, a case-by-case assessment can be made as to whether they can be reused, and what associated treatment would be required. In making the choice, the presence of nutrients in the water streams is an important precondition, since these nutrients can possibly be reused. The transport of reused residual water to the agricultural sector implies that farmers need to pump up less groundwater in dry periods. As a result, the impact of drought conditions on the surrounding area is diminished.

Resource loop closure: missing elements

This project involves all stakeholders in the safe and economical closure of the water resource loop. Besides the province and water utilities, it concerns industry, Water Authorities and farmers.

We are researching the following missing elements:

• quality of industrial wastewater in the dairy industry;
• best available technology for the food-processing industry for wastewater reuse;
• consequences for the environment (water systems);
• pathogen routes of waterborne diseases in the cow-dairy-wastewater-fodder-cows route;
• legal and underwriting risks;
• cost-benefit analysis of recommended solution.

Conditions for responsible reuse

The research contributes to a robust and climate-adaptive water system that better retains water in dry periods, thereby reducing the need to abstract groundwater. Water utilities can join regional stakeholders in discussing the challenges of a sustainable water system and possible solutions. This creates a support base for measures and system choices.

A concrete project output will be an overview of the water streams that can be provided to the agricultural sector. This includes the conditions under which this provision is feasible: technological, water-quality and -quantity, health-risk management, water-system impact, and financial. The case-study results can be translated into general terms, to make them applicable to other dairy locations. Water utilities can help their business clients with knowledge about the conditions for water reuse.