Water treatment

Clean water through lava filter


A number of ornamental plant growers have solved the problem of mineral oils in their basin water by using a lava filter. They have even noticed an increase in production and quality.


Mario van Vliet


A number of years ago, rose grower John van Os from De Kwakel started experiencing major cultivation problems. “Something was clearly going on. We tried everything, but the quality, length and production were substantially lower than that of comparable growers in the Westland.” Van Os joined forces with seven other growers in the region, forming a group to investigate the problems all of them were experiencing.


Chemicals in rainwater

The growers tested the rainwater and discovered that the concentration of mineral oils was high, especially during dry summers when the small amounts of rainwater in seemed to collect large amounts of ‘chemicals’ when falling to earth. The growers have not yet investigated what these chemicals are and what the concentrations are in other parts of the country.


The high concentration of mineral oils was sufficient reason for the growers to take appropriate measures. Some of them chose to mix osmosis water through their basin water, others decided to aerate their basin water more and a few covered their basin with a tarpaulin. In all cases this resulted in fewer cultivation problems.


From 170 to 210 pieces per m2

Van Os chose the ABF System, a lava filter (see box). He claims this solved his problems. To illustrate this, one of his rose plants produced 170 pieces per m2 per year. When he decided to use osmosis water in 2003, production increased to 180 pieces. After acquiring the ABS System, production increased further to 210 pieces per m2. “And by then it was an old plant.”


Eurocactus, a nursery in Nieuwveen, also bought the ABF System. For a number of summers the company had had problems with root formation, explains managing director Harry van der Hoorn. “We had already conducted a number of tests to improve the quality of the potting soil and had also adjusted the fertilization schedule and the greenhouse climate. But all to no avail. Another possible cause of our problems was the rainwater. By introducing an aerating system and adding PoCo we noticed spectacular improvements in the summer months. After installing the ABF System we saw even more improvements in the quality and cleanliness of the water. Thanks to these measures, most of the problems were solved. Root formation is good and the plant is stronger and of a better quality.”



All growers with problems seem to live in the Schiphol area. A direct link has not yet been established, but Van der Hoorn has his suspicions: “I don’t know if the quality of the rainwater has anything to do with Schiphol. But since we are located right under an approach route, it may not be a coincidence.”


Managing director Wim van Etten of Van Etten Techniek claims that the quality of the air, and therefore the quality of the rainwater in the Netherlands, leaves much to be desired. “There’s more going on than you think. There are substances in our basins you’d rather not encounter.”


According to Guus Meis of DLV Bouw Milieu Techniek, however, there is no hard evidence that vehicle or aircraft exhaust gases cause the cultivation problems. “A number of growers suspect that oil in the basin water causes these problems. Although potting soil may also contain oil, it usually has a different composition. Further investigation into the composition of the oil in basin water is necessary in order to determine the source and thus the harmfulness to the plant.”


Whether products like lava filters are really so effective has not been proven. But for now, Van de Hoorn is convinced. “Most of the pollution is removed from my rainwater.”


ABF System

The ABF System (Automatic Biological Filter) was introduced three years ago by Van Etten Techniek and Wise Use. Two ornamental plant growers have now purchased the ABF System. It is a biological filter that cleans rainwater, drain water and surface water. The system pumps dirty water to a separate silo, where it is filtered by lava granules. Bacteria collect in the granules and break down the harmful substances. To speed up bacterial action, PoCo (a herbal and plant extract from Wise Use) is added. The water in the silo is circulated rapidly to increase the frequency of contact with the lava granules. Clean water is collected at the bottom of the silo and transported to another silo.


Depending on the filter version, the system purifies between 0.5 and 42 m2 of water per hour. “This provides a supply of clean water for one or two days,” says Wim van Etten, managing director of Van Etten Techniek. He estimates that a system suitable for ornamental plant cultivation costs at least €17,000, depending on the size.


Photograph: A lava filter can break down harmful substances in the basin water of growers located under Schiphol approach routes.

Vakblad voor de Bloemisterij 32 (2005)