Recycling Type of Water Purification System with Hydroponic Culture to Apply the Floating Type of Aquatic Plants of Water Spinach Under the Influence of Global Warming in Kochi, Japan

M. Fujimaki^*, A. Chikami^**, T. Mouri^***, S. Nishimura^* and M. Murakami^*
*School of Environmental Science and Engineering; Kochi University of Technology Tosayamada-cho, Kami-city, Kochi 782-8502 Japan
^**Sanyu Consultants Inc., Daiichi Fuji Bldg. Daikan-cho Higashi-ku Nagoya 461-0002 Japan
^***Japan Agricultural Cooperatives, Ohte-cho Chiyoda-ku Tokyo 100-6837 Japan

Abstract

The purpose of this study is to evaluate the effect of artificial wetland water purification system with specific aquatic plant of vegetable such as water spinach (Convolvulus) treating the wastewater from hydroponic culture which uses liquid chemical fertilizer. It is a serious problem for hydroponic culture at warm temperate region in the south western part of Japan to discharge the deteriorated liquid chemical fertilizer with very high concentration of nutrients (N, P) from the farm into the river system without any treatment. A new treatment system is applied at Tai farm to reduce the concentration of the nutrients in the deteriorated liquid fertilizer. Water purification system using aquatic plant of water spinach has been examined to reduce the treatment cost of the wastewater. A series of field observation and water quality measurement were carried out to evaluate the capability of water purification by aquatic plant. The water spinach has a high capability of reducing 85% of T-N and 83% of PO4-P. Cost and benefit analysis suggests the advantage of hydroponic culture with water spinach to cover the installation and operation and maintenance cost (C) with substantial benefit (B) with B/C ratio of 2.6.

Key words: water purification; nutrients removal; hydroponic culture; water spinach