Evaluation of pollutant removal in a constructed irrigation pond |
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Authors: | Tasuku Kato Hisao Kuroda Hideo Nakasone Hirohide Kiri |
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Institution: | (1) College of Agriculture, Ibaraki University, 3-21-1 Chuoh, Ami, Inashiki Ibaraki, 300-0393, Japan;(2) National Institute for Rural Engineering, 2-1-6 Kannondai, Tsukuba Ibaraki, 305-8609, Japan |
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Abstract: | A year-long study on the water quality and hydrology was carried out to investigate the characteristics of the pollutant concentrations
and pollutant removal in a constructed irrigation pond. The pond is part of a circular irrigation system for paddy fields
within Lake Kasumigaura watershed, Japan. The average concentrations of the total nitrogen (TN), chemical oxygen demand (COD),
total phosphorus (TP), and suspended solids (SS) at the pond outlet were 7.4, 8.6, 0.2, and 18.8 mg L−1, respectively. The average removed loads for the same indices were 0.14, 2.47, 0.11, and 24.2 g m−2 day−1, respectively. The percentages of pollutant removals from the inflow loads for the same indices were 3, 26, 42, and 63%,
respectively. The pond discharged the TN loads of 128 kg due to sediments stirred by operation of a pump for April and May.
The average TN removal was 19% from June to August and was smaller than that reported in published literatures (40–50%). Major
reasons were considered to be that the turnover of water in the pond was rapid (86% per day) and that the TN concentration
of inflow water was relatively low (5.9 mg L−1). The percentages of pollutants that flowed into the pond to the outflow loads from the study site were 6.6, 4.8, 1.6, and
1.1% for TN, COD, TP, and SS loads, respectively. The pollutant removal will be increased if the design of the circular irrigation
system is reconsidered to utilize a pollutant removal function in the irrigation pond. |
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Keywords: | COD Mass balance Nitrogen Phosphorus Suspended solids Water balance Water quality |
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