Photocatalysts Hold Hopes for Sustainable Hydroponic Tomato Growing

Purified wastewater in hydroponic growing can bring more crops than untreated one, according to the Research Center for Advanced Science and Technology of the University of Tokyo, and the Kanagawa Agricultural Technology Center. Both centers jointly studied the use of photocatalysts for water purification in hydroponic tomato growing systems between 2002 and 2005.

In the hydroponic cultivation of tomatoes, rock wool has been widely used as the growing media. Rock wool is a wool-like insulation made from natural minerals and because of its non-degradable properties, the disposal of it has posed environmental concerns, prompting the search for alternative organic media, such as coco fibers and rice husks. With these organic materials, however, a hydroponic nutrient solution has to be treated and disinfected before being recycled, in order to degrade organic pollutants leaching from the materials and prevent the spread of disease. In addition, the nutrient solution, dissolved with inorganic fertilizer rich in nitrogen and phosphorous, is dripped over the plants, leaving 20 to 30 percent of it unabsorbed and drained out as waste.

To reuse this wastewater, the agriculture center conducted experiments using titanium dioxide (TiO2) photocatalysis from sunlight to water treatment for the organic hydroponic system. Using TiO2 filters, total organic carbon (TOC) was monitored in the solution being treated, recovered and sent to a supply tank. The results showed that the TOC values of the treated water remained as low as those of water being supplied to the drip irrigation system, demonstrating the filter's ability to remove organic matter.

It was also confirmed that the treated water allows plant seedlings to grow faster, produce more leaves, and yield more tomatoes than untreated water. The center plans to conduct further tests leading to the commercial application of this technology, in collaboration with the University of Tokyo, the Kanagawa Academy of Science and Technology, and manufacturers in the hydroponics industry.

http://www.rcast.u-tokyo.ac.jp/en/

Posted: 2006/12/15 06:28:28 PM
Japanese version