Effect Of Combination Of Biochar And Magnesium Salt On The Purification Capacity Of Black Odorous Water In Floating Wetlands

Biochar has good adsorption capacity on pollutants in water,and struvite reaction is a cost-effective method for the simultaneous recovery of nitrogen and phosphorus.In this study,biochar and magnesium oxide was added to the floating wetland to research their effect on purifying the black and smelly sewage.The main results are shown as follows:(1)The removal of ammonia nitrogen is mainly depending on the adsorption of biochar,and removal of phosphorus mainly was related to struvite reaction of magnesium oxide.When biochar and magnesium oxide mixed in a certain proportion,it can Simultaneously remove nitrogen and phosphorus from water.When mixed material(0.15 g of biochar mixing with 0.008 g of magnesium oxide)was added to solution containing ammonia nitrogen(30mg/L)and phosphorus(20mg/L),the removal effiencicy of ammonia nitrogen and phosphorus can reach 18.6% and 90.6%,respectively.(2)The combination of apricot shell biochar,with vermiculite has the best effect on the germination rate of Oryza sativa L.and Lolium perenne L.seeds.Low content of magnesium oxide can promote the development of root of Lolium perenne L,while high content of magnesium oxide shows a significant inhibitory effect on Oryza sativa L.and Lolium perenne L.(3)Both biochar and magnesium oxide increased the total nitrogen and total phosphorus content in the wetland substrate.In floating wetlands planted with Canna indica L,compared with wetland without biochar and magnesium oxide(S),total nitrogen in substrates of the wetlands with biochar and different content of magnesium oxide added increased by 173.0%,220.0% and 276.8%(P <0.05);the total phosphorus increased by 2.0%,132.1% and 22.9%,respectively.(4)When biochar and magnesium oxide were added into the floating wetland,the content of dissolved oxygen,the removal rate of ammonia nitrogen,total nitrogen as well as total phosphorus increased,while the removal rate of CODcr decreased.On the 9th day of operation,in wetlands planted with Canna indica L.,when biochar and magnesium oxide(1.6g,3.2g and 6.4g respectively)were added to the substrates,the removal rate of total nitrogen increased by 20.4%,30.2% and 36.1%,respectively(P<0.05),and in the wetlands added with biochar and magnesium oxide(3.2g and 6.4g respectively),the removal rate of total phosphorus increased significantly by 13.3% and 13.4%,respectively(P <0.05).