Wastewater treatment by using kenaf in paddy soil and effect of dissolved oxygen concentration on efficiency

• Published in: Ecological engineering Vol. 29; no. 2; pp. 125 - 132
• Main Authors: Abe, Kaoru, Ozaki, Yasuo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2007
• Subjects: Furrow irrigation; Hibiscus cannabinus; Nitrogen; Phosphorus; Removal; Roots oxidation activity; Removal; Roots oxidation activity; Phosphorus; Furrow irrigation; Hibiscus cannabinus; Nitrogen
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2006.02.003

We previously reported that kenaf ( Hibiscus cannabinus L.) planted in a zeolite-bed filter-ditch system provided highly effective treatment of wastewater. Here we compared that system with treatment in fallow paddy fields irrigated in different ways in a greenhouse. Paddy soil was a useful alternative to zeolite as the bed filter material. The efficiency of removal of N and P under furrow irrigation and flooding was 82–92% of that of the zeolite system. Most kenaf roots were distributed in water with a high dissolved oxygen (DO) concentration and a high redox potential; few roots grew in reducing soil under water. The roots distributed in the water contributed most to wastewater treatment. A low DO concentration (0.3 mg L −1) decreased the efficiency of N and P removal. However, nightly low DO concentration (near 0 mg L −1) alternating with daily high DO concentration did not seriously restrict the efficiency. An increase of alpha-naphthylamine oxidation activity in kenaf roots at low DO concentration is discussed in regard to induction of an oxygen-protective enzyme.