OPERATION CHARACTERISTICS RESEARCH OF URBAN SEWAGE TREATMENT DURING THE START-UP PROCESS IN CONSTRUCTED WETLANDS

Seven subsurface flow constructed wetlands were constructed through different combinations of four plants (iris, bulrush, radix ophiopogonis and canna) and three substrates (slag, zeolite and gravel), aiming at studying the operation characteristics of urban sewage treatment during the wetlands' start-up under the conditions of different plants, same substrate as well as different substrates, same plant. The results indicated that regarding the average removal rates of CODCr, gravel>slag>zeolite, canna>iris>bulrush>radix ophiopogonis; regarding the average removal rates of TN, zeolite>gravel>slag, canna>bulrush>radix ophiopogonis>iris; as for the average removal rates of NH4+-N zeolite>gravel>slag, bulrush>canna>radix ophiopogonis>iris; as for the average removal rates of TP, slag>gravel>zeolite, bulrush>canna>iris>radix ophiopogonis. There were no significant differences regarding the removal rates of CODCr among the three substrate wetlands with or without plants; as for the removal rates of TN and NH4+-N, zeolite was far better than slag and gravel. After planting, the removal rates of TP by the three substrates were all about 10.75%. The removal rates of CODCr by three plants (iris, radix ophiopogonis and canna) increased with the operation time, while the removal rate of CODCr by bulrush declined due to its bad growing situation. The removal rate of TN by canna wetland was higher than that by the other three; the differences among plant wetlands on the removal rates of Na-4(+)-N were not significant. The removal rates of TP by the four plants were around 9.24%.