Effects of pH on boron accumulation in cattail (Typha latifolia) shoots, and evaluation of floating islands and upward flow mesocosms for the removal of boron from wastewater
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The objectives of this research were to determine the optimal pH for maximizing boron (B) accumulation in cattail (Typha latifolia) shoots, and to develop treatment systems for the removal of B from wastewater.
We performed a hydroponic experiment to examine the effects of pH on shoot B accumulation in cattail plants. Cattails were grown in nutrient solutions containing B at three concentrations (25, 75, and 125 mg B L−1, in the form of H3BO3), supplied at seven pH levels ranging from 4.0 to 10.0. In addition, we compared the effectiveness of B removal by cattails cultured in floating islands and in upward-flow mesocosms.
The effects of pH on growth and B accumulation, although significant, were relatively small compared to the effect of B on the relationship between shoot growth and shoot B accumulation. Cattail floating islands and cattail upward-flow mesocosms reduced concentrations of B in the solutions by 12.5–21.4 % and 12.2–21.3 %, respectively, in the first cycle, and by 11.0–14.2 % and 4.0–13.4 %, respectively, in the second cycle. The higher B removal efficiencies of the floating islands occurred at lower B concentrations, whereas the opposite was observed for the upward-flow mesocosms. Cattails can regenerate rapidly after harvesting of the upper shoots; however, B concentrations in the regenerative upper shoots were found to be lower than that in the first-growth upper shoots.
Optimal pH for shoot B accumulation by cattails is 6.0. Although direct comparisons between the effectiveness of B removal by floating islands and upward-flow mesocosms are difficult, we concluded that upward-flow mesocosms are more suitable for the treatment of B-contaminated wastewater.
KeywordsFloating island Boron removal Upward-flow mesocosm Typha latifolia Wastewater treatment
This work was supported by the Electric Power Research Institute, the National Natural Science Foundation of China (Grant No. 41101303), and the China Scholarship Council. We are grateful to Prof. Norman Terry and Dr. Amanda R. Stiles (Department of Plant and Microbial Biology, University of California, Berkeley, USA) for English editing and valuable comments that improved the manuscript.
Compliance with ethical standards
The authors declare that they have no conflict of interest.
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