| Farmland water recession usually refers to non-point source pollution caused by excessive use of pesticides,irrational use of chemical fertilizers and water-soil erosion caused by precipitation runoff during agricultural production activities.Due to human activities such as artificial irrigation or natural factors such as precipitation,high-concentration nitrogen and phosphorus sewage caused by underground movements such as farmland drainage,farmland surface runoff and underground leakage enters rivers,lakes and other types of water bodies,leading to larger areas and degrees of water environment pollution.It becomes the main factor that causes water environment pollution.In this paper,experiments were conducted to study the purification effect of aquatic plants,substrate and aquatic plant-substrate combination ecosystem on farmland water recession.Samples were taken for high-throughput sequencing,and microbial composition of the system was analyzed.Considering the pollution characteristics of the eighth drainage of the Duliujian River in Jinghai District,Tianjin,based on the combination technology of aquatic plant-substrate,the purification scheme of farmland water recession was designed.The main conclusions of this paper are as follows:(1)In the purification experiment of aquatic plant on farmland water recession,the six plant treatment groups were set,repectively,A1(6 scallions),A2(6 irises)and A3(3scallions+3 irises),B1(8 scallions),B2(8 irises),B3(4 scallions+4 irises).On the15th day,the removal rate of ammonia nitrogen with all groups was above 90%,much higher than that in CK group(0.36%),and the removal rate of B3 group was the fastest and its average removal rate was the highest.The removal rate of TP with all groups was A2(67.83%)>B3(65.31%)>B2(62.91%)>B1(56.22%)>A3(42.67%)>A1(20.58%)>CK(8.72%).Among them,the removal rate of TP with iris groups(A2,B2)was higher than that of scallion groups(A1,B1).The removal rate of COD with all groups was B3(86.47%)>A3(73.66%)>B2(68.81%)>A2(66.18%)>B1(53.73%)=A1(53.73%)>CK(2.91).Among them,the removal rate of B3 group was optimal and its average removal rate was the highest.(2)In the purification experiment of substrate on farmland water recession,the removal rates of ammonia nitrogen with small volcanic rock,large volcanic rock,zeolite and substrate combination treatment groups ranged from 15.81 to 47.8%,20.96to 54.52%,14.53 to 44.66%,27.60 to 72.69%,respectively.The removal rate of ammonia nitrogen reached a stable level after 25 days,and the removal rate of substrate combination treatment group was the highest and was the fastest to enter a stable state.The average removal rates of COD with small volcanic rock,large volcanic rock,zeolite and substrate combination treatment groups were 64.17%,63.52%,57.93%and68.32%,respectively.The removal rate of COD ranged from 14.49%to 89.13%,13.19%to 90.39%,8.41%to 80.43%,17.39%to 90.50%,respectively,and all treatment groups reached a stable level after 17 days.The removal rate of TP with small volcanic rock,large volcanic rock,zeolite and substrate combination treatment group ranged from 5.06 to 59.47%,4.95 to 58.85%,5.06 to 59.47%,5.06 to 69.31%,and the removal rate of substrate combination treatment group was higher and reached a stable level soon.(3)In the purification experiment of farmland water recession by aquatic plant-substrate combination,after the continuous operation and monitoring for 30 days,it showed that the removal rate of ammonia nitrogen of farmland water recession by the system combination was between 93.54%and 98.13%when HRT=3d,and the purification effect was better;the removal rate of TP ranged from 44.30%to 55.09%;the removal rate of COD was between 83.71%and 93.72%,and the purification effect was better.(4)The microbial sequencing results showed that the top three dominant microbial groups with relative abundance were Proteobacteria(58.45%),Firmicutes(23.05%),Bacteroidetes(11.53%),Actinobacteria(2.19%)and Acidobacteria(1.01%)at the phylum level;and top ten microbial groups with maximum relative abundance were Niveibacterium(23.90%),Pseudomonas(6.89%),Cellvibrio(5.17%),Ralstonia(4.12%),Clostridium sensu stricto 1(2.86%),Vibrio(2.43%),Lactobacillus(1.82%),Flavobacterium(1.71%),Staphylococcus(1.53%)and Zoogloea(1.42%)at a genus level.(5)Considering the pollution characteristics of the eighth drainage of the Duliujian River in Jinghai District,Tianjin,this paper designed a subsurface flow wetland and ecological surface flow wetland scheme based on the combination technology of aquatic plant-substrate.The scheme utilized surrounding ponds for reconstruction,with a project area of approximately 75220 m~2.Scallion and iris at a 1:1 ratio were planted about 195200 plants in total,and zeolite and volcanic rock were needed about 14976m~3. |
PDF Full Text Request