The Study Of Horizontal Flow Constructed Wetland And Veritical Flow Constructed Wetland To Treat River Pollution

The technology of constructed wetland is a new kind of sewage controlledtechnology which developed since the1970s and stems from the nature wetlands. Thetechnology purifies sewage depending on the synergistic effect of padding, plants andmicroorganism which are strengthened by designing by human. In this experiment, thetreatment effect of constructed wetlands with two different padding including zeoliteand slag were compared, the transformation of nutrient substances of constructedwetlands with different current form including vertical flow and horizontal flow werediscussed and the treatment effect of constructed wetland systems with different waterlevel, concentration of pollutants and influent load were researched. The residence timedistributions were researched by pulse tracer method to analysis the characteristics offlow regimes through using the parameters of normal distribution fitted by residencetime distribution function. And the main conclusions are:(1) The COD removal efficiency of slag horizontal flow constructed wetland ishigher than zeolite horizontal flow constructed wetland, and the removal rate of slagvertical flow constructed wetland is about88%which is higher than77%of zeolitevertical flow constructed wetland; the COD removal capacity of horizontal flowconstructed wetland is a little higher than vertical flow one with same padding. So CODremoval rate is influenced by padding but has little relationship with current form. Thetotal phosphorus (TP) removal rate of zeolite constructed wetland can reach to75%andof slag constructed wetland maintains below70%; likewise, the TP removal rate ofhorizontal flow constructed wetland is higher. The removal rates of ammonia nitrogen(AN) in different current forms are close; but the AN removal rate of zeolite constructedwetland is about20%higher than slag constructed wetland. As to the removal rate ofnitrate, the reactor flow pattern is the main influencing factors. The nitrate removal rateof horizontal flow constructed wetland is about85%while it’s just30%of vertical flowconstructed wetland. It is not obvious of the influence of different padding to nitrateremoval rate.(2) The increase of influent concentration of COD, phosphorus and ammonianitrogen would cause fluctuating of the removal rate of wetland system, and the effluentconcentration can restore to the original level after a certain time. However, the changes of nitrate nitrogen concentration in influent impact the removal rate of vertical flowwetland greatly and even lead to the phenomenon that the effluent concentration ofnitrate surpasses the influent. The effluent nitrate concentration maintains about15mg/lwhen the nitrate concentration in influent increases from12mg/l to16mg/l. And effluentnitrate concentration is6mg/l which is two times of influent when influentconcentration changes to3mg/l.(3) As to vertical flow wetland, the semi-submerged water level is a betteroperational model because the reactor not only ensures the high removal rate ofammonia nitrogen but also can maintain a reasonable effect to remove nitrate. Theremoval rate of ammonia nitrogen and nitrate respectively is90%and50%of verticalflow wetland with semi-submerged water level. As to horizontal flow wetland, thesubmerged condition is a better operation mode in order to take complete use of thepadding. The submerged horizontal flow wetland has a relative high removal rate ofnitrate is above95%and the removal rate of ammonia nitrogen is about60%.(4) There are a “short flow” in the side close to outlet and a “dead zone” in lowerzone close to inlet in slag vertical flow constructed wetland; and there are someblockings located in the upper zone close to influent pool and the lower zone close toeffluent pool in slag horizontal flow constructed wetland.