Research On Heavy Metal Wastewater Treatment With Constructed Wetland

With the development of industry and agriculture, the discharge of heavy metalwastewater has been a harm to the environment. In order to offer some valuablereference for practice project, in this study, the wavy subsurface flow constructedwetland(W-SFCW) was used to dispose the heavy metal wastewater which containedmanganese, zinc, cadmium, copper and nickel. By doing this, we studied the treatmenteffect of heavy metal wastwater and the variation along the reactor of different kindsof pollutants in the wetland system. And the migration of the heavy metals interceptedin the wetland was studied as well.The dynamic monitoring results showed thaw W-SFCW had stable removaleffect on different kinds of pollutants which existed in the heavy metal wastewater.The average removal rate of Zn, Cd, Cu and Ni were all more than90%, the averageremoval rate of Mn was69.105%. The average removal rate of CODCr, TN, NH4+-Nreached81.947%,73.865%,70.936%, respectively.By analysising the variation of various pollutants along the reactor in the wetland,we found that the alkaline environment played an important role for the heavy metals’removal. Most of Zn, Cd, Cu and Ni was removed in the first part half of the system.In the first half of the system, the removal of Mn was mainly affected by pH, while inthe latter half part of the system, it was mainly affected by the dessolved oxygen. Theprocess of nitrogen’s removal in the W-SFCW manily occured in the downward flowwhich denitrification was very strong. In the upward flow, nitrogen’s removal mainlydepended on the absorption of the plants.Finally, we analysised the migrtion of the heavy metals in the supporting mediaand plants. The results of the dipping experiment showed that, the heavy metals thatremained in the system were immobilized well. And the wetland system couldprecipitate the leaching heavy metals again. By detecting the content of the heavymetals in the body of plants, we found that in the1st and the2nd plants, most heavymetals were enriched in the leaves. But in the3rd to6th plants’ bodies, Zn, Cd, Cuand Ni were mainly enriched in the roots, while Mn was mainly enriched in theleaves.