Effect of Substances Released from Sediment on Artificial Instream Aeration

Artificial instream aeration is an economical method to increase river dissolved oxygen content and to improve water quality in rivers. However, there were unsteady aeration effects when sediment disturbed by the aeration flow. In order to investigate the effect of sediment disturbed on artificial instream aeration efficiency, artificial aeration tests in clearance bubble form were carried out at laboratory. The test results show the dissolved oxygen consumed by the sediment could be ignored for the aeration tests in which sediment do not be disturbed and the dissolved oxygen raised and the chemical oxygen demand dropped obviously after the aeration stopped. If sediment is observably disturbed in the aeration tests, a lot of suspended solid get into waters from the sediment and the aeration efficiency decrease with increase of suspended solid content in the waters. And after the aeration stopped, dissolved oxygen in the waters decreases rapidly with time in exponential form due to the oxygen demand of inorganic reduction substances in suspended solid. It is recognized by the test that the instream aeration forms not to disturb sediment are suitable for the natural rivers with thicker sediment.