[Oxygen transfer efficiency of four kinds substrates applied in artificial aeration vertical-flow wetland]

In subsurface flow constructed wetlands, artificial aeration plays an important role in enhancing the ability of pollutant removal. Oxygenation capacity of four substrates, limestone, vesuvianite, 500 grade ceramisite and high-strength ceramisite, are tested under three kinds of gas volume [0.19, 0.38, 0.76 m3 x (m2 x h)(-1)] in artificial aeration vertical-flow wetland. When the gas volume is 0.19 m3 x (m2 x h)(-1), the results demonstrate that the oxygen utilization of 500 grade ceramisite and high-strength ceramisite are highest as 14.39% and 14.21%, and the oxygen utilization of limestone and vesuvianite are 11.68% and 13.11% respectively. With the increase of aeration intensity, oxygen transfer efficiency parameter KLa rises accordingly. However, the oxygen utilization of vesuvianite and two other kinds of ceramisite decreases with the increase of aeration intensity. The oxygen utilization of vesuvianite, 500 grad ceramisite and high-strength ceramisite are lower as 7.67%, 10.46% and 10.77% respectively when the aeration intensity is 0.76 m3 x (m2 x h)(-1). On the contrary, the oxygen utilization of limestone get its maximum value of 14.04% as the aeration intensity is 0.38 m3 x (m2 x h)(-1).