| Constructed wetland is an efficient and a low-cost wastewater ecological treatment technology which integrates ecology,landscape and environment.However,in the actual operation of wetlands,its traditional nitrification and denitrification capacity for high nitrogen wastewater was limited to a certain level.And plenty of carbon source materials was required in the traditional anaerobic denitrification process,which resulted in a high cost of treatment.In view of this situation,a new way what was the increasingly mature anaerobic ammonia oxidation process in recent years was provided to solve this problem.But,due to the slow growth rate,high environmental requirements and weak impact load resistance of anaerobic ammonia oxidation bacteria,the combination of constructed wetland treatment technology and anaerobic ammonia oxidation technology can be used to construct a low carbon,stable and simple anaerobic ammonia oxidation system for high nitrogen wastewater in constructed wetlands and was important and meaning.In the project,the coupling relationship between anaerobic ammonia-oxidizing bacteria and environmental factors in sediments of different depths in natural wetlands was the basis for the study of wastewater treatment with high nitrogen of constructed wetlands.Then three groups of vertical flow constructed wetlands were constructed with gravel（CW1）,zeolite（CW2）and oyster shell（CW3）as a single substrate respectively.After the wetland system was stable,anaerobic ammonia oxidation sludge（SV=8%）was inoculated into the wetland with the help of bio-augmentation technology,and the influent nitrogen load was gradually increased to enrich anaerobic ammonia oxidizing bacteria.The denitrification capacity of the wetland for high nitrogen wastewater and the existence characteristics of anaerobic ammonia oxidizing bacteria were investigated.The results showed that:（1）Sediments from 0-65 cm depth in mangrove wetlands were collected and determined.The results showed that anammox bacteria genes was detected in the all samples from the mangrove wetland sediment at 0-65 cm depth.Although the obvious distribution regulation of anammox bacteria genes absolute abundance and relative abundance along with the increase of distance from sewage outlet and depth was not be found,the correlation analysis showed that the spatial abundance and relative abundance distribution of anammox bacteria genes was closely related to environmental factors.In term of absolute abundance,anammox bacteria genes abundance was significantly positively correlated with total nitrogen（TN）,total carbon（TC）and total organic carbon（TOC）,and ammonia nitrogen（NH4+-N）,nitrite nitrogen（NO2--N）,nitrate nitrogen（NO3--N）and Electrical conductivity（EC）can also affect the abundance of anammox bacteria genes.In term of relative abundance,the relative abundance of anammox bacteria genes was significantly positively correlated with C:P and N:P ratio,and total carbon（TC）,C:N ratio and Electrical conductivity（EC）can also affect the relative abundance of anammox bacteria genes.（2）Constructed wetland denitrification system enhanced by anaerobic ammonia-oxidizing bacteria was operated continuously.the result showed that anaerobic ammonia oxidation process was discovered in wetland system at 173 days,which realized simultaneous removal of ammonia nitrogen and nitrous nitrogen.When the hydraulic load rate（HLR）was 2 cm/d and TN was 767±46.3 mg/L,the TN removal rate of CW1,CW2and CW3 was 69.3±5.1%,74.9±2.9%,80.2±2.8%respectively,and the removal load was99.8±13.1 mg/（L·d）,111.5±11.3 mg/（L·d）and 133.5±13.9 mg/（L·d）respectively,and the removal effect of TN was presented by CW3>CW2>CW1.When HLR was 4 cm/d and TN was 814.2±53.6 mg/L,high removal efficiency of TN was still maintained in CW1and CW3,with removal rate of 62.9±6.9%,67.7±8.5%respectively,and removal load rate of 198.6±27.3 mg/（L·d）and 248.2±41.7 mg/（L·d）respectively.The removal efficiency of TN was worst in CW2,with removal rate of 43.3±9.4%and removal load of 142.9±39.3 mg/（L·d）,in which the removal effect of TN was presented by CW3>CW1>CW2.From the overall effect of TN removal,the removal efficiency and stability of nitrogen pollutants in constructed wetlands based on oyster shells are better than gravel and zeolite.（3）The absolute abundance of anaerobic ammonia-oxidizing bacteria in CW1,CW2and CW3 wetlands system at 308 days was reached 1.49×109 copies/g,6.37×108copies/g and 1.04×109 copies/g,respectively,and the relative abundance of anaerobic ammonia-oxidizing bacteria was 7.00×10-1,4.99×10-1 and 2.26×10-1,respectively,what indicated that anaerobic ammonia-oxidizing bacteria had become the dominant bacteria for nitrogen removal in every wetland system.The result also showed that the relative abundance of anaerobic ammonia oxidizing bacteria is not the appropriate factor to characterize the denitrification effect of anaerobic ammonia oxidizing bacteria in wetland.（4）Anaerobic ammonia-oxidizing bacteria have been successfully enriched and gradually become dominant bacteria after 308 days of operation,which indicates that the internal environment of wetland was more suitable for its growth,and the experimental system of enhanced denitrification has been successfully launched and constructed.During the whole operation of wetland system,anammox bacteria and denitrifying bacteria was coexisted and accumulated in each wetland.Overall,oyster shell and gravel are suitable substrates for anaerobic ammonia oxidation enrichment in constructed wetlands for the treatment of high nitrogen wastewater. |
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