Studies On Microorganism Functional Groups And The Relationship Between Microorganism And Plant In The Constructed Wetland In Subtropical China

Constructed wetlands are a natural alternative to technical methods of wastewater treatment, and have consequently been widely applied for water quality amelioration. An integrated vertical flow constructed wetland was built in Hangzhou Botanical Garden, Zhejiang Province, China, to purify light eutrophic water from Jade fish-seeing pond. In this paper, the rhizosphere microorganism quantity and activity were determined by applying the research techniques of soil microorganism. On the basis of seasonal performances, we estimated the role of microorganisms in nitrogen removal together with the purifying effects of constructed wetland for wastewater.The nitrifying bacteria were lower in winter than in summer. There were greatly significant differences in Canna indica and Phalaris arundinacea in water down flow chambers (DFC), Phalaris arundinacea in water up flow chambers (UFC) (P<0.01);The nitrification in winter was higher than in summer, which was different from the nitrifying bacteria, and there was greatly significant difference between winter and summer (P<0.01);The denitrifying bacteria, as the same as the nitrifying bacteria, was lower in winter than in summer, there was greatly significant difference in in Canna indica in UFC (P<0.01), and significant difference in Canna indica in DFC (P<0.05);The denitrification was lower in winter than in summer, and there was greatly significant difference between winter and summer (P<0.01).The number of rhizosphere microorganisms (include ammonifying bacteria, nitrifying bacteria and denitrifying bacteria) was larger than in blank sand: In winter, there was greatly significant difference in ammonifying bacteria between blank sand and Phalaris arundinacea (P<0.01), in nitrifying bacteria between blank sand and Canna indica (P<0.01), blank sand and Phalaris arundinacea (P<0.01), in denitrifying bacteria between blank sand and Canna indica (P<0.01), blank sand and Phalaris arundinacea (P<0.01), significant difference in denitrifying bacteria between Canna indica and Phalaris arundinacea (P<0.05);In summer, there was significant difference in ammonifying bacteria between blank sand and Phalaris arundinacea (P<0.05), greatly significant difference in nitrifying bacteria between Canna indica and Phalaris arundinacea (P<0.01). The activity of rhizosphere microorganisms (include ammonification, nitrification and denitrification) was higher than in blank sand: In winter, there was greatly significant difference in nitrification between blanksand and Canna indica (PO.01), blank sand and Phalaris arundinacea (PO.01), in dinitrification between blank sand and Canna indica (PO.01), blank sand and Phalaris arundinacea (P<0.01);In summer, there was greatly significant difference in denitrification between blank sand and Canna indica (PO.01), blank sand and Phalaris arundinacea (PO.01), Canna indica and Phalaris arundinacea (PO.01).The number of rhizosphere ammonifying bacteria was larger in DFC than in UFC, by contraries, the denitrifying bacteria was lower, and there was significant difference in denitrifying bacteria in summer (PO.05);Different from the number microorganisms, the ammonification was higher in DFC than in UFC, the nitrification and denitrification were lower in DFC than in UFC, but there was no significant difference.The relationship between number and activity of rhizosphere microorganisms indicated: There was significant negative correlation between number of nitrifying bacteria and nitrification (r=-0.691, pO.Ol);and significant positive correlation between number of denitrifying bacteria and denitrification (r=0.484, pO.05).The relationship between activity of rhizosphere microorganisms and removal rates indicated: There was no significant correlation between nitrification and removal rates of NH4-N, NO3-N, TN, TP, COD, BOD5;But there was significant positive correlation between dinitrification and removal rate of NO3-N (r=0.952, pO.05), between dinitrification and removal rate of BOD5 (r=0.912, pO.05).By comparing with a natural pond, the study demonstrated that the purifying results changed with the alternation of seasons. In spring, the concentrations of ammonia nitrogen (NH4-N), nitrate nitrogen (NO3-N), total nitrogen (TN), chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) lowered obviously;the removal rates of TP and COD reached the highest (70.07% and 77.36%, respectively). In summer, there was significant difference in the content reduction of TN (PO.05), and the removal rate of NH4-N reached by 56.07%, the content of NH4-N met the standard of first grade surface water. In autumn, the concentration of total phosphorus (TP) was greatly brought down, and there was significant difference in the content reduction (PO.05). In winter, the concentration of NH4-N in fish pond was higher than the compared pond while other parameters were lower. The results indicated the concentrations of NH4-N> TP (in winter and spring) > COD and BOD5 in the effluent of the constructed wetland met the standard of first grade surface water.The whole study analyzed the physical and chemic characteristics of constructed wetland, relativity between rhizosphere microorganism quantity and activity, relativity between microorganism activity and removal rate, relationship between plants and rhizosphere microorganisms. This study established the theoretical basis of rhizosphere microorganisms for new constructed wetland, and also provided reference for treating environment with constructed wetland.