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Eighty Dutch growers will purify collectively

More than eighty glasshouse horticulture companies in 's-Gravenzande, the Netherlands, are participating in a pilot project in centralized wastewater collection and treatment of wastewater flows. The companies unanimously agreed with the business case on 10 May. From the wastewater, collected via an existing central water drainage system (CAD-system), with modern techniques plant protection products, fertilisers, such as nitrogen and phosphate will be removed.

For glasshouse horticulture companies a mandatory purification duty for wastewater flows will apply from January 1st 2018. The water must be clean before it can be discharged into the surface water. With a collective strategy it is possible, under certain conditions, to receive a deferral until January 1st 2021 to realise the necessary installation. However, a business plan needs to be submitted to the authorized body before the end of this year.

Purification system

The glasshouse horticultural companies in that region are already connected to the CAD-system, a separate sewerage system. As a result the waste flow of these companies can be collected easily at a central point. Aqua-Terra Nova developed the purification system and the business case. One way in which this water is biologically purified is by slow sand filtration and with active carbon filtration for the removal of plant protection products.

Annual costs low
The investment for the pilot project for almost 164 ha glass in the Westland amounts to 1,1 million euros. The municipality of the Westland and Hoogheemraadschap of Delfland not only help to consider the project, but also contribute financially and aid with manpower. For the remaining amount the CAD association needs to take a loan.

Cluster purification of the CAD-water is the solution least costly to the participating companies to comply with the legally mandatory purification. The annual costs for the companies will be between the 700 and 1,000 euros per hectare. For growers which are purifying their water by themselves, the annual costs will amount to 3,000 euros per hectare. The annual costs for the cluster purification can be reduced even further when over a few years the water after desalination will be fed back to the companies.


For the construction of the wastewater treatment plant they need to acquire land. With the agreement of the members of the association they can start. The planned date for the implementation of the installation is mid 2017.

For more information:
Zuidweg 79
2671 MP Naaldwijk
Tel: 0174 - 625246
Fax: 0174 - 62 97 44
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