| Currently,the traditional wastewater biological treatment technology had the disadvantages of great amount of surplus sludge volume and high cost of economy.In recent years,the new biological treatment technology has been widely studied and applied in the actual sewage treatment plants,which has a great prospect.This study took aerobic granular sludge and anammox system as the object,on the basis of carbon materials with an excellent adsorptive property in the field of water treatment.It is an attempt to add different carbon materials to new wastewater treatment technology using contrast test to investigate the effects of carbon materials on nitrogen removal performance.The study aimed to improve nitrogen removal efficiency of wastewater treatment system through the combined application of carrier and biological treatment system.（1）Study on the effect of graphene oxide（GO）on the nitrogen removal performance of AGSGO was widely used in different fields and exposed to the water environment inevitably.The effects of different GO concentrations（0,50,100,150,200 mg/L）on nitrogen removal performance,toxicity level and microbial community structure of aerobic granular sludge were investigated.The results showed that the graphene oxide prepared by advanced oxidation of graphite has a lamellar structure with smooth surface and a variety of oxygen-containing functional groups.Contrast with the control group,the layer spacing of GO increased.The nitrification process of AGS was promoted by GO under different concentrations in the short-term,especially under 200 mg/L concentration of GO,the removal rate of NH4+-N within 1.5 h was 89.8%,which was higher than the control group（77%）.At the same time,there were significant differences between control group and experimental groups of lactate dehydrogenase（LDH）release level when GO concentration>100 mg/L,and PN was influenced little by GO in the short-term.Conversely,high concentrations of GO with long-term exposure inhibited the nitrification process of AGS,and microbial enzyme activity showed a similar tendency.At the same time,AMO activity of AGS was 0.146μg NO2--N/（min·mg protein）at 200 mg/L GO.Which was lower than the control group（0.21μg NO2--N/（min·mg protein））.On the 30th day,the release of LDH in 200 mg/L GO reactor was 48.04%higher than control group and the contents of EPS was 30.06%lower than control group,which indicating that high concentrations of GO had a toxic effect on AGS.However,50 mg/L GO did not have harmful effects on AGS system of the whole experiment for it could enhance nitrogen removal efficiency under long-term exposure conditions.Microbial communities have different responses to the stimulation of GO under different concentrations.Nitrospira had a certain tolerance to GO at high concentrations.（2）Biochar and Fe-modified biochar enhances microbial nitrogen removal capability of AnammoxIn view of the existing drawbacks of Anammox process,such as low microbial retention and the time of double population size was long,this study aims to enhance the nitrogen removal performance of Anammox system by adding biochar and Fe-modified biochar.Biochar was prepared by enteromorpha using pyrolysis at high temperature.The results showed that biochar has a variety of functional groups with porous structures which was regular close packing.The specific surface area of Fe-modified biochar was larger than biochar,and the results of XRD showed that Fe-modified composites contained hematite.Batch experiments were conducted to determine the effects of composite materials with different Fe:C mass ratio on the Anammox system.The results showed that the beneficial effects of different Fe:C mass ratios of materials firstly increased and then decreased as the mass of Fe loading increased.The nitrogen removal performance of Anammox system was improved best by Fe-modified biochar when the Fe:C mass ratio was 1:10,the total nitrogen removal rate reached 80.88%.Meanwhile,the batch tests were set to determine the optimal dosage of Fe-modified biochar（Fe:C=1:10）to enhance nitrogen removal capability of Anammox.The results showed that Fe-modified biochar with 5 g/L and 10 g/L in anammox could promote the nitrogen removal,and the total nitrogen removal rate was 78.74%and73.54%,respectively,which were higher than control group（70.11%）.At the same time,the total nitrogen removal rate of 20 g/L Fe-modified biochar of Anammox was slightly lower than control group（68.73%）.After determining the optimum Fe:C mass ratio of Fe-modified composite materials and the optimal dosage for Anammox system,a long-term stable operation using contrast experiment was conducted to explore the effects of biochar and Fe-modified on Anammox.The control group,the group with biochar and the group with Fe-modified biochar of Anammox were set to improve nitrogen loading rate（NLR）gradually and explore the strengthening effect of adding different materials on Anammox.Compared with the control group,the addition of BC and Fe BC could promote the removal efficiency of NH4+-N and NO2--N,and intensified the nitrogen removal performance of Anammox system.In the whole operation process,the average NRR of BC and Fe BC was0.367 kg/（m3·d）and 0.364 kg/（m3·d）,respectively,which was significantly higher than CK reactor(0.346 kg/（m3·d）.As the results of stoichiometric ratio of Anammox showed that Fe-BC has the advantage to remove NO2--N from anammox reactor.Specific anammox active（SAA）showed that the addition of biochar and Fe-modified biochar could improve the metabolic activity of An AOB,and there was significant difference between control group and experimental groups in theⅣphase.The results of EPS showed that the addition of biochar and Fe-modified biochar did not stimulate An AOB produced PN and PS.In general,the application of biochar and Fe-modified biochar materials could successfully achieve the purpose of enhancing the nitrogen removal performance of Anammox. |
