| Nutrient enrichment, mainly with nitrogen (N), is the major reason causing massive growth of alga and river eutrophication. In order to solve the problems of river eutrophication, deterioration of water quality and water ecological system damage. In this paper, we first selected a typical inflow lake river (Qinshui River) to investigate the ecological remediation effect under the different ecological remediation methods. Then we studied ecological remediation effects of Elodea nuttallii and immobilized nitrogen cycling bacteria (FNCB) technology, analyzed river surface sediment denitrification, anaerobic ammonia oxidation (ANAMMOX), N species cycling etc. We also applied nitrogen cycling bacteria-submerged macrophyte-biological carrier integrated remediation technology in our river remediation project. At last we provided the scientific evidence of control of river eutrophication, and offered method to control the pollution of other similar river. By the study, the primary conclusions are as follows:(1) The presence of macrophytes enhanced the oxygen penetration depth, about 16mm. Simultaneously, the technology changed the pH microenvironment in surface water-sediment, creating suitable condition for nitrogen cycling processes (the co-function of denitrification and ANAMMOX).(2) From the 15N IPT experiment analysis of simulation experiment cores, the highest production of N2 of denitrification and ANAMMOX processes were about 656.2 μmol·N2·m-2·h-1 and 353.1 μmol·Ni·m-2·h-1 after Elodea nuttallii and immobilized nitrogen cycling bacteria (E-INCB) existed stably. Also, the production of N2O fluxes was about 476.8μg·m-2·h-1. E-INCB technology awaked the joint activities of denitrification and ANAMMOX processes.(3) As the Q-PCR analysis showed, the technology of E-INCB enhanced the functional genes abundance of nitrogen cycling bacteria. Compared the different functional genes:nirK, nirS, nosZ, Ca. Scalindua 16S rRNA, and hzo, the abundance of functional genes reflecting ANAMMOX bacteria was about 1.8×107 copies·g-1, and denitrification bacteria was about 1.28×1010 copies·g-1.(4) We used the high-throughput sequencing technology to study the nitrogen bacteria community structure. The genera related to the ANAMMOX in our experiment cores were Planctomyces, Candidatus Brocadia and Candidatus Scalindua. The genera related to denitrification were Achromobacter sp. And Thauera. The diversities of nitrogen cycling bacteria were enhanced, which offset the disadvantage of low diversities and activities of nitrogen cycling bacteria in situ river sediment.(5) Compared the porewater N species distribution in 5 cm sediment of four different ecological remediation treatment groups. As the co-function of Nitrogen cycling bacteria and submerged macrophytes (Elodea nuttallii), changed the vertical concentration distribution of TN, NH4+-N, NO3--N and NO2--N. In the sediment depth between 0-2cm, the concentration of NH4+-N, NO3--N reduced, NO2--N increased. The effects balanced the distribution of different N species, and provided the reaction substrate. Simultaneously, the concentration of TN decreased significantly, and the water quality was improved.(6) The submerged macrophytes-nitrogen cycling bacteria-biological carrier assemblage technology was used to conduct the ecological remediation project in situ Qinshui River. We took full advantage of co-function of submerged macrophytes and immobilized nitrogen cycling bacteria to strength the nitrogen removal ability of the river. The DO content was increased, and the pH condition was improved. The TN removal rate was 56%; NH4+-N removal rate was 59.67%; N03’-N removal rate was 58.61%; TP removal rate was 61.87%; COD removal rate was 66.42%. The result of one year water quality (from 2014.8.1 to 2015.11.1) showed that submerged macrophyte and nitrogen cycling bacteria assemblage technology can improve river water quality significantly. |
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