| Due to a large number of bait and fertilization of the traditional aquaculture,its residual bait and the excreta of the breeding objects will be transformed into nitrite,ammonia nitrogen and hydrogen sulfide,which pollutes the aquaculture water,but also directly endangers the breeding objects.Pond sediments are an important part of the pond ecosystem,sediment accumulation in aquaculture ponds.On the one hand,the adsorption of nitrogen,phosphorus and other biological nutrients and the formation of nutrients trap,the other hand,the sediment will gradually corrupt the quality of aquaculture ponds,increase the incidence of breeding animals.Nowadays,nitrogen removal of water bodies has become the focus of global sewage treatment.Corresponding biological nitrogen removal research has also become a hot research field.The biological nitrogen removal research has been discovered include denitrification,anaerobic ammonium-oxidizing?Anammox?.Nitrogen cycle in aquacultureenvironmentmainlyincludes nitrogenfixation,ammonification,nitrification,denitrification and anaerobic ammonia oxidation.Microbes play a major role in the nitrogen cycle.Most studies have shown that denitrification and anammox are the main ways of denitrification in ponds,the concentration of nitrogen substrates?nitrite nitrogen?,carbon concentration and temperature were the main factors affecting nitrogen removal.Therefore,it is of great significance to study the effects of main factors on denitrification and anammox and their microbe inaquaculture sediments,which can be used to solve the problem of ecological environment.In order to master the influence characteristics of main factors affecting denitrification and anammox in pond sediments,TOC analyzer,UV spectrophotometer and other equipment and fluorescence quantitative PCR,high-throughput sequencing,construction of gene cloning library technology and 16S rRNA species identification technology were used,to study effect nitrogen substrate?nitrite nitrogen?concentration,carbon source of concentration and temperature on anaerobic ammonium oxidation and denitrification,microbial activity and nitrogen removal efficiency in samples.Using statistical methods,analysis of anaerobic ammonium oxidation and denitrification and microbial activity of parameter range.The main research results are as follows:1.Organic carbon had a significant promoting effect on the removal of NO2--N and NO3--N and the increase of denitrifying bacteria abundance.The removal efficiencies of NO2--N and NO3--N were the highest at the concentration of 150 mg·L-1,which were98.90%and 99.86%,respectively.The removal efficiencies of NO2--N and NO3--N without starch were 86.25%and 79.22%,respectively.At the starch concentration of150 mg·L-1,the biomass of denitrifying bacteria was the largest with the fastest growth rate.When the concentration of starch was 50 mg·L-1,NH4+-N removal efficiency was the largest,NH4+-N removal efficiency decreased with the increase of starch concentration,while Anammox bacteria showed a slowly increasing trend without starch addition.After adding different concentrations of starch,the anammox bacteria generally showed a decreasing trend.Organic carbon had a significant positive effect on the diversity of denitrifying bacteria and the increase of species richness,of which undifferentiated and?-Proteobacteria denitrifying bacteria had a dominant position in aquaculture sediments.2.The removal temperature of NO2--N,NO3--N and NH4+-N increased with the increase of temperature and reached the peak of 99.42%at 28?.The NO3--N.The removal efficiency of NO2--N was the same as that of NO2--N removal efficiency.The removal efficiency of NO3--N was 88.56%at 28?and the content of NO3--N was less than 1 mg·L-11 was 28?.The content of NO3-N was higher than 1 mg·L-11 at other temperature gradients.The removal rate of NH4+-N is far less than the removal rate of NO2--N and NO3--N,but its removal rate increases with the increase of temperature,which is the highest at 34?and 47.31%.The removal rates of NO2--N and NO3--N and the denitrifying bacteria reached their maximum at 28?.The removal rates of NH4+-N and the anammox bacteria reach the maximum at 34?,however,the abundance of denitrifying bacteria was significantly higher than that of anaerobic ammonium oxidizing bacteria.3.Nitrite can promote the removal of NO2--N,NO3--N and NH4+-N.The removal rate of NO2--N increases with the increase of nitrite concentration.When the concentration of nitrite is 150.The removal efficiency of NO3--N was similar to that of NO2--N removal efficiency.When the concentration of nitrite was 150 mg·L-1,the removal efficiency was the highest.With the highest rate of 87.53%.With the continuous increase of nitrite concentration,the removal rate of NH4+-N also increased,but when the concentration of nitrite was 300 mg·L-1,the removal rate was the highest47.5%.The removal rates of NO2--N and NO3--N and the denitrifying bacteria reached the maximum at the nitrite concentration of 150mg·L-1,and the removal rates of NH4+-N and the anaerobic ammonium oxidizing bacteria were in the range of 300mg·L-1reached its maximum value,but the denitrifying bacteria abundance was significantly higher than that of anaerobic ammonium oxidizing bacteria.4.In denitrification and anammox device,the synchronous reaction conditions of organic carbon,temperature and nitrite were studied.The removal efficiency of NO2--N in denitrification device reached 99.82%,the removal efficiency of NO3--N was 86.10%,the removal efficiency of NH4+-N was 45.74%and the removal efficiency of TOC was70.76%.The total abundance of denitrifying bacteria was 2.43×10111 copies·g-1,the total anaerobic bacteria abundance was 6.16×108 copies·g-1.Betaproteobacteria class is the most dominant group,and the level includes Dechloromonas,Burkholderiaceae,Thiothrix,Thauera,Azoarcus,Brachymonas,Azospirillum,etc.In anaerobic ammonium oxidation device,the removal efficiencies of NO2--N,NO3--N,NH4+-N and TOC were97.99%,93.05%,54.92%and 58.82%,respectively.The total abundance of denitrifying bacteria and anaerobic bacteria were 2.04×10111 copies·g-1,9.49×108 copies·g-1.Dominant population was Candidatus brocadia.The removal efficiency of NO2--N and TOC in denitrification device was significantly higher than that of anaerobic Ammonia oxidation device,anaerobic ammonia oxidation device NO3--N and NH4+-N removal efficiency was significantly higher than the denitrification device.Under the suitable organic carbon,temperature and nitrite conditions,the denitrification efficiency and the diversity of denitrifying bacteria in denitrification device was relatively higher.Under the suitable anaerobic ammonia oxidation conditions,the ammonia oxidation reaction in anaerobic ammonia oxidation device was obvious,and the diversity of the anaerobic ammonia oxidizing bacteria wasrelatively higher.The above results provide a theoretical basis for the regulation of denitrification and anammox in the sediments of pond culture. |
PDF Full Text Request