Air stripping was adopted to treat nickel ammonia complex ion-containing wastewater in order to remove nickel and ammonia simultaneously in one technological process.The relationship among pH,the concentration of nick...Air stripping was adopted to treat nickel ammonia complex ion-containing wastewater in order to remove nickel and ammonia simultaneously in one technological process.The relationship among pH,the concentration of nickel ammonia complex ion and total ammonia concentration was analyzed theoretically.Influence of pH value,water temperature,airflow rate and time on air stripping was studied in detail by static experiment in laboratory.The results show that at pH 11,temperature of 60℃and airflow rate of 0.12 m3/h,NH3 and Ni 2+concentrations remained in wastewater are less than 2 and 0.2 mg/L,respectively,after blowing for 75 min,which reaches the standard of the state discharge.When the tail gas is absorbed by 0.5 mol/L H2SO4 in order to avoid the secondary pollution,the absorption rate can achieve 70%.展开更多
The influencing factors and kinetics of oxidative degradation of ammonia nitrogen in high salinity wastewater by sodium hypochlorite oxidation( Na Cl O) were studied. The results showed that the degradation process of...The influencing factors and kinetics of oxidative degradation of ammonia nitrogen in high salinity wastewater by sodium hypochlorite oxidation( Na Cl O) were studied. The results showed that the degradation process of ammonia nitrogen by sodium hypochlorite accorded with a pseudo first-order kinetics model,and the influencing factors included Na Cl O dosage,initial concentration of ammonia nitrogen,salinity,temperature,and so on. When Na Cl O dosage was 0. 6%( MCl∶ MN= 13. 76),the reaction rate constant was up to 0. 015 75 min^(-1). The higher the initial concentration of ammonia nitrogen was,the worse the effect of oxidation reaction was. When the initial concentration did not exceed 45 mg/L,the effect on oxidation reaction rate constant increased with the increase of the initial concentration. Low salinity had no effect on ammonia nitrogen oxidation.When salinity was higher than 2. 0%,the inhibition effect on ammonia nitrogen oxidation would increase,and the reaction rate constant decreased obviously with the increase of salinity. The improvement of reaction temperature was beneficial to ammonia oxidation degradation. As temperature increased from 10 to 35 ℃,the reaction rate constant rose from 0. 00188 to 0. 01043 min^(-1).展开更多
This study aimed to investigate the mechanism of nitrogen doping,migration,and conversion during ammonia torrefaction and also explore the evolution law of the chemical structure of cellulose.The results showed that t...This study aimed to investigate the mechanism of nitrogen doping,migration,and conversion during ammonia torrefaction and also explore the evolution law of the chemical structure of cellulose.The results showed that the ammonia torrefaction pretreatment could significantly optimize the distribution of nitrogen and oxygen elements in cellulose.The carbon skeleton first captured the active nitrogenous radicals to form-NHn-N,and pyridine-N and pyrrole-N originated from the conversion of-NHn-N.The existence of C=O played a major role in the immobilization of nitrogen.The nitrogen in bio-oil exists mainly in the form of five-and six-membered heterocycles.The correlation analysis showed that the main precursors for the formation of nitrogenous heterocyclic compounds were five-membered Oheterocyclic compounds.Finally,the product distribution characteristics in the torrefaction-pyrolysis systems were summarized,and the nitrogen doping and conversion mechanisms were proposed.This study expanded the boundaries of cellulose pretreatment and the production of high-value chemicals.展开更多
Nine strains of ammonia nitrogen degradation strains from C1 to C9 were isolated from industrial wastewater to study their degradation and conversion of ammonia nitrogen. The results showed that C2 strain with a high ...Nine strains of ammonia nitrogen degradation strains from C1 to C9 were isolated from industrial wastewater to study their degradation and conversion of ammonia nitrogen. The results showed that C2 strain with a high degradation activiity of ammonia nitrogen, and the ammonia nitrogen degradation rate of the activated C2 strain was 93% within 24 h when the initial concentration of ammonia nitrogen was 200 mg/L under the conditions of inoculation 10%, temperature 35?C, pH 7.0, rotation 200 r/min. And C2 was identified as Bacillus amyloliquefaciens.展开更多
Electrochemical N_(2) reduction reaction(eNRR) over Cu-based catalysts suffers from an intrinsically low activity of Cu for activation of stable N_(2) molecules and the limited supply of N_(2) to the catalyst due to i...Electrochemical N_(2) reduction reaction(eNRR) over Cu-based catalysts suffers from an intrinsically low activity of Cu for activation of stable N_(2) molecules and the limited supply of N_(2) to the catalyst due to its low solubility in aqueous electrolytes.Herein,we propose phosphorus-activated Cu electrocatalysts to generate electron-deficient Cu sites on the catalyst surface to promote the adsorption of N_(2) molecules.The eNRR system is further modified using a gas diffusion electrode(GDE) coated with polytetrafluoroethylene(PTFE) to form an effective three-phase boundary of liquid water-gas N_(2)-solid catalyst to facilitate easy access of N_(2) to the catalytic sites.As a result,the new catalyst in the flow-type cell records a Faradaic efficiency of 13.15% and an NH_(3) production rate of 7.69 μg h^(-1) cm^(-2) at-0.2 V_(RHE),which represent 3.56 and 59.2 times increases from those obtained with a pristine Cu electrode in a typical electrolytic cell.This work represents a successful demonstration of dual modification strategies;catalyst modification and N_(2) supplying system engineering,and the results would provide a useful platform for further developments of electrocatalysts and reaction systems.展开更多
The utilization of aquaculture wastewater as irrigation is an effective way to recycle and reuse water and nitrogen fertilizer resources because it contains numerous nutrients.However,it is still unclear that the patt...The utilization of aquaculture wastewater as irrigation is an effective way to recycle and reuse water and nitrogen fertilizer resources because it contains numerous nutrients.However,it is still unclear that the pattern of substituting aquaculture wastewater irrigation for fertilizer supplementing is conducive to improving the soil nitrogen status,fruit yield and water-fertilizer use efficiency for tomato production.In this context,the experiment was intended to establish the appropriate irrigation regime of aquaculture wastewater in tomato production for freshwater replacement and fertilizer reduction to ensure good yields.Pot experiments were conducted with treatments as farmers accustomed to irrigation and fertilization used as control(CK),1.75 L aquaculture wastewater with base fertilizer(W1),2 L aquaculture wastewater with base fertilizer;and 2.25 L aquaculture wastewater with base fertilizer(W3).We examined the effects of aquaculture wastewater irrigation on soil nitrogen distribution,Nrelated hydrolases,tomato yield,and economic benefits.The results showed that the control treatment had the highest N input,about 24.68%higher than the W3 treatment,while the yield was only about 7.81%higher than W3.This indicated that the overuse of chemical fertilizer was present in the current tomato production.Although the reduction of fertilizer in aquaculture wastewater irrigation caused a decrease in tomato production,this economic loss can be compensated by cost savings in the wastewater disposal.Among aquaculture wastewater treatments,the W3 treatment had the highest overall benefit,achieving 62.63%freshwater savings,37.50%fertilizer input reduction,and an economic return of approximately 19,466 Yuan per hectare higher than the control.Additionally,increasing the irrigation volume of aquaculture wastewater could provide more available nutrients to the soil,which were more prevalent in the form of organic nitrogen.The lower soil nitrate reductase activities(NR)under aquaculture wastewater treatments after harvesting also proved that this pattern was beneficial to reduce soil nitrate nitrogen residues.Overall,the results demonstrate that aquaculture wastewater irrigation alleviates the soil nitrate residues,improves nutrient availability,and results in more economic returns with water and fertilizer conservation for the greenhouse production of tomatoes.展开更多
This paper presents lab-scale experiment carried out to evaluate the c orrelation between ammonia nitrogen(NH3-N) and p-toluidine using sequencing batc h reactor treating synthetic p-toluidine wastewater. The profiles...This paper presents lab-scale experiment carried out to evaluate the c orrelation between ammonia nitrogen(NH3-N) and p-toluidine using sequencing batc h reactor treating synthetic p-toluidine wastewater. The profiles of NH3-N and p -toluidine were traced under the concentration of sucrose in the influent varied from 0 to 500 mg/L, aerated airflow varied from 0.6 to 1.2 L/min and temperatur e varied from 10 to 25℃, respectively. The results showed that the concentratio n of NH3-N turned from increase to decrease when p-toluidine was nearly complete ly biodegraded, so the profile of NH3-N could clearly indicate the endpoint of p -toluidine biodegradation. And the profile of NH3-N was not influenced by the su crose in the influent, aerated airflow and temperature. It is showed that using ammonia nitrogen as monitoring and control parameter is feasible and reliable an d has promising application in amine wastewater treatment by SBR.展开更多
[Objective]The study aimed to discuss the feasibility and optimal conditions of removing ammonia nitrogen by using microwave coupled with active carbon. [Method]In the study,a novel process,microwave radiation coupled...[Objective]The study aimed to discuss the feasibility and optimal conditions of removing ammonia nitrogen by using microwave coupled with active carbon. [Method]In the study,a novel process,microwave radiation coupled with active carbon,was applied to remove ammonia nitrogen from wastewater,and the influences of solution pH,air conditions,active carbon usage,microwave power and time on the removal effect of ammonia nitrogen were studied. [Result]Microwave coupled with active carbon can remove ammonia nitrogen efficiently,and pumping air into the wastewater can also increase the removal rate of ammonia nitrogen to a certain extent. Higher pH,intensive microwave power and longer treating time could also increase the removal rate of ammonia nitrogen using microwave radiation coupled with active carbon,whereas the usage of active carbon contributed a small impact. It was proved that microwave coupled with active carbon was an effective method for the removal of ammonia nitrogen from wastewater. Meanwhile,the orthogonal experiment results showed that the removal rate of ammonia nitrogen reached 92. 5% under the optimal conditions,that is,the usage of active carbon was 0. 5 g,pH =11,microwave radiation power was 850 W,and microwave action time was 4 minutes. [Conclusion]The research provided a new method to remove ammonia nitrogen from wastewater,namely microwave coupled with active carbon.展开更多
Fluid catalytic cracking (FCC) salty wastewaters, containing quaternary ammonium compounds (QACs), are very difficult to treat by biochemical process. Anoxic/oxic (A/O) biochemical system, based on nitrification and d...Fluid catalytic cracking (FCC) salty wastewaters, containing quaternary ammonium compounds (QACs), are very difficult to treat by biochemical process. Anoxic/oxic (A/O) biochemical system, based on nitrification and denitrification reactions, was used to assess their possible biodegradation. Because of the negative effects of high salt concentration (3%), heavy metals and toxic organic matter on microorganisms’ activities, some techniques consisting of dilution, coagulation and flocculation, and ozonation pretreatments, were gradually tested to evaluate chemical oxygen demand (COD), ammonia-nitrogen (ammonia-N) and total nitrogen (TN) removal rates. In this process of FCC wastewater, starting with university-domesticated sludge, the ammonia-N and TN removal rates were worst. However, when using domesticated SBR’s sludge and operating with five-fold daily diluted influent (thus reducing salt concentration), the ammonia-N removal reached about 57% while the TN removal rate was less than 37% meaning an amelioration of the nitrification process. However, by reducing the dilution factors, these results were inflected after some days of operation, with ammonia-N removal decreasing and TN barely removed meaning a poor nitrification. Even by reducing heavy metals concentration with coagulation/flocculation process, the results never changed. Thereafter, by using ozonation pre-treatment to degrade the detected organic matter of di-tert-butylphenol and certain isoparaffins, COD, ammonia-N and TN removal rates reached 92%, 62% and 61%, respectively. These results showed that the activities of the microorganisms were increased, thus indicating a net denitrification and nitrification reactions improvement.展开更多
The effects of different nitrogen application levels on nutrient uptake and ammonia volatilization were studied with the rice cultivar Zheyou 12 as a material.The accumulative amounts of nitrogen,phosphorus and potass...The effects of different nitrogen application levels on nutrient uptake and ammonia volatilization were studied with the rice cultivar Zheyou 12 as a material.The accumulative amounts of nitrogen,phosphorus and potassium in rice plants across all growth stages showed a trend to increase with increasing nitrogen application levels from 0 to 270 kg/hm 2,but decreased at nitrogen application levels exceeding 270 kg/hm 2.Moreover,the accumulative uptake of nitrogen,phosphorus and potassium by the rice plants was increased by application of organic manure in combination with 150 kg/hm 2 nitrogen.The nitrogen uptake was high during the jointing to heading stages.Correlation analysis showed that rice yield was positively correlated with the accumulative uptake of nitrogen,phosphorus and potassium by the rice plants.The highest correlation coefficient observed was between the amount of nitrogen uptake and rice yield.The rate and accumulative amounts of ammonia volatilization increased with increasing nitrogen fertilizer application level.Compared with other stages,the rate and accumulative amount of ammonia volatilization were higher after base fertilizer application.The ammonia volatilization rates in response to the nitrogen application levels of 270 kg/hm 2 and 330 kg/hm 2 were much higher than those in the other treatments.The loss of nitrogen through ammonia volatilization accounted for 23.9% of the total applied nitrogen at the nitrogen application level of 330 kg/hm 2.展开更多
This study aimed to present a novel clay/biochar composite adsorption particle, which made from abandoned reed straw and clay to remove ammonia nitrogen(NH4^+-N) from micro-contaminated water. The removal performance ...This study aimed to present a novel clay/biochar composite adsorption particle, which made from abandoned reed straw and clay to remove ammonia nitrogen(NH4^+-N) from micro-contaminated water. The removal performance of NH4^+-N by composite adsorption particle was monitored under different raw material proportions and initial NH4^+-N concentration. Besides, adsorption kinetics and adsorption isotherms were investigated to reveal the adsorption mechanisms. The results showed that NH4^+-N was effectively removed under optimal proportion of biochar, foaming agent and crosslinker with 20%, 3%, and 3%, respectively. The optimal contact time was 150 min and the best removal efficiency was 88.6% at initial NH4^+-N concentration of 20 mg L^-1. The adsorption performance was well described by the second order kinetic model and Freundlich model. The novel clay/biochar composite adsorption particle in this study demonstrated a high potential for NH4^+-N removal from surface water.展开更多
In this study,a three-stage biological aerated filter(BAF) system was proposed for the enhancement of nitrogen removal in the treatment of low carbon-to-nitrogen ratio(C/N ratio) municipal wastewater.Operational param...In this study,a three-stage biological aerated filter(BAF) system was proposed for the enhancement of nitrogen removal in the treatment of low carbon-to-nitrogen ratio(C/N ratio) municipal wastewater.Operational parameters were studied for each process for maximum nitrite accumulation in the nitrification step and nitrite adaptation in the denitrification step.Nitrite accumulation during nitrification could be controlled by the dissolved oxygen(DO) concentration,presenting a mean value of 40% at around 1.0 mg DO/L.Denitrification could be adapted to nitrite and the process was stable if nitrite in the reactor was keep low.Once the operational parameters were established,the process was stable and a steady state was maintained for over 30 days,and the various indexes of discharged water were up to the Discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002) Level-one A.It was concluded that the three-stage BAF system proposed in this study was excellent in nitrogen removal performance by employing three-column functioning as short-cut nitrification,short-cut denitrification and secondary nitrification,respectively.展开更多
We conducted field trials of rice grown in sandy soil and clay soil to determine the effects of nitrogen application levels on the concentration of NH4+-N in surface water,loss of ammonia through volatilization from p...We conducted field trials of rice grown in sandy soil and clay soil to determine the effects of nitrogen application levels on the concentration of NH4+-N in surface water,loss of ammonia through volatilization from paddy fields,rice production,nitrogen-use efficiency,and nitrogen content in the soil profile.The concentration of NH4+-N in surface water and the amount of ammonia lost through volatilization increased with increasing nitrogen application level,and peaked at 1-3 d after nitrogen application.Less ammonia was lost via volatilization from clay soil than from sandy soil.The amounts of ammonia lost via volatilization after nitrogen application differed depending on the stage when it was applied,from the highest loss to the lowest:N application to promote tillering > the first N topdressing to promote panicle initiation(applied at the last 4-leaf stage) > basal fertilizer > the second N topdressing to promote panicle initiation(applied at the last 2-leaf stage).The total loss of ammonia via volatilization from clay soil was 10.49-87.06 kg/hm2,equivalent to 10.92%-21.76% of the nitrogen applied.The total loss of ammonia via volatilization from sandy soil was 11.32?102.43 kg/hm2,equivalent to 11.32%-25.61% of the nitrogen applied.The amount of ammonia lost via volatilization and the concentration of NH4+-N in surface water peaked simultaneously after nitrogen application;both showed maxima at the tillering stage with the ratio between them ranging from 23.76% to 33.65%.With the increase in nitrogen application level,rice production and nitrogen accumulation in plants increased,but nitrogen-use efficiency decreased.Rice production and nitrogen accumulation in plants were slightly higher in clay soil than in sandy soil.In the soil,the nitrogen content was the lowest at a depth of 40-50 cm.In any specific soil layer,the soil nitrogen content increased with increasing nitrogen application level,and the soil nitrogen content was higher in clay soil than in sandy soil.In terms of ammonia volatilization,the amount of ammonia lost via volatilization increased markedly when the nitrogen application level exceeded 250 kg/hm2 in the rice growing season.However,for rice production,a suitable nitrogen application level is approximately 300 kg/hm2.Therefore,taking the needs for high crop yields and environmental protection into account,the appropriate nitrogen application level was 250-300 kg/hm2 in these conditions.展开更多
A Florida wastewater treatment facility studied how Simultaneous Nitrification Denitrification (SND) coupled with traditional nitrogen removal would be used to meet the state’s current advanced wastewater treatment n...A Florida wastewater treatment facility studied how Simultaneous Nitrification Denitrification (SND) coupled with traditional nitrogen removal would be used to meet the state’s current advanced wastewater treatment nutrient criterion. This study examined the effect of these combined processes on the fate and transport of the nitrogen species during the treatment process. The effectiveness of nitrogen removal within the full scale sequential batch reactor system (SBR) and the extent of SND compared to nitrification and denitrification in the nitrogen removal process was also evaluated. Finally, the overall performance of the municipal wastewater treatment facility utilizing these combined processes was evaluated. Overall, this application reduced the total nitrogen to almost 6% of the permitted concentration of 3.0 mg/L. The combination of both processes also resulted in an actual ?concentration 93.7% lower than the acceptable theoretical ?concentration, which also resulted in effluent Total Inorganic Nitrogen nearly 80% lower than the permitted 3.0 mg/L effluent concentration. Further, the process produced a composite Total Nitrogen concentration that was 74% lower than the permitted concentration. This coupling of SND with traditional nitrogen removal resulted in a highly effective process to reduce nitrogen in the municipal wastewater effluent which is also attractive for potential implementation due to the low cost expenditure incurred in its utilization.展开更多
The characteristics of the zeolite modified by microwave and sodium acetate and its sorption of ammonia-nitrogen from simulated water sample were investigated.The results show that the modified zeolite by microwave-so...The characteristics of the zeolite modified by microwave and sodium acetate and its sorption of ammonia-nitrogen from simulated water sample were investigated.The results show that the modified zeolite by microwave-sodium acetate(SMMZ)has a high sorption efficiency and removal performance.The ammonia-nitrogen removal rate of SMMZ reaches 92.90%.The surface of SMMZ becomes loose and some pores appear,the specific surface area,total pore volume and average pore diameter increase after modification.Compared to the natural zeolite,SMMZ has a more concentrated pore size distribution in the range of 0-10 nm.The cation exchange capacity(CEC)of SMMZ is higher than that of the natural zeolite.And the ammonia nitrogen removal rate is consistent with the change of CEC.The SMMZ possesses rapid sorption and slow balance characteristics and ammonia-nitrogen sorption is consistent with both Langmuir adsorption isotherm model and Freundlich adsorption isotherm model.The adsorption kinetics of ammonia-nitrogen follows the pseudo-second order kinetic model.展开更多
We investigated the communities of ammonia-oxidizing bacteria(AOB) in activated sludge collected from eight wastewater treatment systems using polymerase chain reaction(PCR) followed by terminal restriction fragment l...We investigated the communities of ammonia-oxidizing bacteria(AOB) in activated sludge collected from eight wastewater treatment systems using polymerase chain reaction(PCR) followed by terminal restriction fragment length polymorphism(T-RFLP),cloning,and sequencing of the α-subunit of the ammonia monooxygenase gene(amoA).The T-RFLP fingerprint analyses showed that different wastewater treatment systems harbored distinct AOB communities.However,there was no remarkable difference among the AOB TRFLP profiles from different parts of the same system.The T-RFLP fingerprints showed that a full-scale wastewater treatment plant(WWTP) contained a larger number of dominant AOB species than a pilot-scale reactor.The source of influent affected the AOB community,and the WWTPs treating domestic wastewater contained a higher AOB diversity than those receiving mixed domestic and industrial wastewater.However,the AOB community structure was little affected by the treatment process in this study.Phylogenetic analysis of the cloned amoA genes clearly indicated that all the dominant AOB in the systems was closely related to Nitrosomonas spp.not to Nitrosospira spp.Members of the Nitrosomonas oligotropha and Nitrosomonas communis clusters were found in all samples,while members of Nitrosomonas europaea cluster occurred in some systems.展开更多
Ammonia oxidation, the first and rate-limiting step of nitrification, is carried out by both ammonia-oxidizing bacteria(AOB) and ammonia-oxidizing archaea(AOA). However, the relative importance of AOB and AOA to nitri...Ammonia oxidation, the first and rate-limiting step of nitrification, is carried out by both ammonia-oxidizing bacteria(AOB) and ammonia-oxidizing archaea(AOA). However, the relative importance of AOB and AOA to nitrifi cation in terrestrial ecosystems is not well understood. The aim of this study was to investigate the effect of the nitrogen input amount on abundance and community composition of AOB and AOA in red paddy soil. Soil samples of 10-20 cm(root layer soil) and 0-5 cm(surface soil) depths were taken from a red paddy. Rice in the paddy was fertilized with different rates of N as urea of N1(75 kg N ha-1 yr-1), N2(150 kg N ha-1 yr-1), N3(225 kg N ha-1 yr-1) and CK(without fertilizers) in 2009, 2010 and 2011. Abundance and community composition of ammonia oxidizers was analyzed by real-time PCR and denaturing gradient gel electrophoresis(DGGE) based on amoA(the unit A of ammonia monooxygenase) gene. Archaeal amoA copies in N3 and N2 were signifi cantly(P<0.05) higher than those in CK and N1 in root layer soil or in surface soil under tillering and heading stages of rice, while the enhancement in bacterial amoA gene copies with increasing of N fertilizer rates only took on in root layer soil. N availability and soil NO3--N content increased but soil NH4+-N content didn't change with increasing of N fertilizer rates. Otherwise, the copy numbers of archaeal amoA gene were higher(P<0.05) than those of bacterial amoA gene in root lary soil or in surface soil. Redundancy discriminate analysis based on DGGE bands showed that there were no obvious differs in composition of AOA or AOB communities in the field among different N fertilizer rates. Results of this study suggested that the abundance of ammonia-oxidizers had active response to N fertilizer rates and the response of AOA was more obvious than that of AOB. Similarity in the community composition of AOA or AOB among different N fertilizer rates indicate that the community composition of ammonia-oxidizers was relatively stable in the paddy soil at least in short term for three years.展开更多
Three new bacteria HS-03, HS-043 and HS-047 isolated from different ec osystems were found capable of aerobic denitrification. The potential applicatio n of these strains in wastewater treatment under aerobic conditio...Three new bacteria HS-03, HS-043 and HS-047 isolated from different ec osystems were found capable of aerobic denitrification. The potential applicatio n of these strains in wastewater treatment under aerobic conditions was investig ated. These three bacteria all presented high nitrogen removal from wastewater t hat more than 98% of 10 mmol/L nitrate could be removed in 12—24 h by adding ch eap external carbon source and low concentration of iron as well as molybdate. T he mechanism at molecular level was analyzed. The success of this aerobic denitr ification applied to wastewater treatment may serve as an alternative to enhance the practical nitrogen removal from wastewater. Main biochemical and physiologi cal features of these strains were characterized. The 16S rDNA sequences were co mpared with the published data in GenBank by using BLAST. The results of phenoty pe and genotype proved that strain HS-03 and HS-047 belonged to Pseudomonas stut zeri and Pseudomonas pseudoalcaligenes respectively. Strain HS-043 was identifie d as Delftia acidovorans of which denitrifying activity has not previously been explored.展开更多
The distillery wastewater of Guangdong Jiujiang Distillery, which is c haracteristic of containing high organic matters and rich total nitrogen, was tr eated by a combination of methane fermentation and denitrificatio...The distillery wastewater of Guangdong Jiujiang Distillery, which is c haracteristic of containing high organic matters and rich total nitrogen, was tr eated by a combination of methane fermentation and denitrification/nitrification processes. 80% of COD in the raw wastewater was removed by methane fermentation at the COD volumetric loading rate of 20 kg COD/(m3·d) using the expanded gra nule sludge bed (EGSB) process. However, almost all the organic nitrogen in the raw wastewater was converted into ammonia by ammonification there. Ammonia and v olatile fatty acids (VFA) remaining in the anaerobically treated wastewater were simultaneously removed utilizing VFA as an electron donor by denitrification oc curring in the other EGSB reactor and nitrification using PEG-immobilized nitrif ying bacteria with recirculation process. An aerobic biological contact oxidizat ion reactor was designed between denitrification/nitrification reactor for furth er COD removal. With the above treatment system, 18000—28000 mg/L of COD in raw wastewater was reduced to less than 100 mg/L. Also, ammonia in the effluent of the system was not detected and the system had a high removal rate for 900—1200 mg/L of TN in the raw wastewater, only leaving 400 mg/L of nitrate nitrogen.展开更多
基金Project(08SK1002)supported by the Major Project of Scientific and Technological Department of Hunan Province,ChinaProject(50508044)supported by the National Natural Science Foundation of China
文摘Air stripping was adopted to treat nickel ammonia complex ion-containing wastewater in order to remove nickel and ammonia simultaneously in one technological process.The relationship among pH,the concentration of nickel ammonia complex ion and total ammonia concentration was analyzed theoretically.Influence of pH value,water temperature,airflow rate and time on air stripping was studied in detail by static experiment in laboratory.The results show that at pH 11,temperature of 60℃and airflow rate of 0.12 m3/h,NH3 and Ni 2+concentrations remained in wastewater are less than 2 and 0.2 mg/L,respectively,after blowing for 75 min,which reaches the standard of the state discharge.When the tail gas is absorbed by 0.5 mol/L H2SO4 in order to avoid the secondary pollution,the absorption rate can achieve 70%.
基金Supported by Project for Achievement Transformation of High and New Technology in Shanghai City(201405267)
文摘The influencing factors and kinetics of oxidative degradation of ammonia nitrogen in high salinity wastewater by sodium hypochlorite oxidation( Na Cl O) were studied. The results showed that the degradation process of ammonia nitrogen by sodium hypochlorite accorded with a pseudo first-order kinetics model,and the influencing factors included Na Cl O dosage,initial concentration of ammonia nitrogen,salinity,temperature,and so on. When Na Cl O dosage was 0. 6%( MCl∶ MN= 13. 76),the reaction rate constant was up to 0. 015 75 min^(-1). The higher the initial concentration of ammonia nitrogen was,the worse the effect of oxidation reaction was. When the initial concentration did not exceed 45 mg/L,the effect on oxidation reaction rate constant increased with the increase of the initial concentration. Low salinity had no effect on ammonia nitrogen oxidation.When salinity was higher than 2. 0%,the inhibition effect on ammonia nitrogen oxidation would increase,and the reaction rate constant decreased obviously with the increase of salinity. The improvement of reaction temperature was beneficial to ammonia oxidation degradation. As temperature increased from 10 to 35 ℃,the reaction rate constant rose from 0. 00188 to 0. 01043 min^(-1).
基金sponsored by the National Natural Science Foundation of China(52176193)the National Key Research and Development Program of China(2019YFD1100602)+1 种基金the Shandong Provincial Natural Science Foundation,China(ZR2020ME184)the SDUT & Zhangdian City Integration Development Project(2021JSCG0013)。
文摘This study aimed to investigate the mechanism of nitrogen doping,migration,and conversion during ammonia torrefaction and also explore the evolution law of the chemical structure of cellulose.The results showed that the ammonia torrefaction pretreatment could significantly optimize the distribution of nitrogen and oxygen elements in cellulose.The carbon skeleton first captured the active nitrogenous radicals to form-NHn-N,and pyridine-N and pyrrole-N originated from the conversion of-NHn-N.The existence of C=O played a major role in the immobilization of nitrogen.The nitrogen in bio-oil exists mainly in the form of five-and six-membered heterocycles.The correlation analysis showed that the main precursors for the formation of nitrogenous heterocyclic compounds were five-membered Oheterocyclic compounds.Finally,the product distribution characteristics in the torrefaction-pyrolysis systems were summarized,and the nitrogen doping and conversion mechanisms were proposed.This study expanded the boundaries of cellulose pretreatment and the production of high-value chemicals.
文摘Nine strains of ammonia nitrogen degradation strains from C1 to C9 were isolated from industrial wastewater to study their degradation and conversion of ammonia nitrogen. The results showed that C2 strain with a high degradation activiity of ammonia nitrogen, and the ammonia nitrogen degradation rate of the activated C2 strain was 93% within 24 h when the initial concentration of ammonia nitrogen was 200 mg/L under the conditions of inoculation 10%, temperature 35?C, pH 7.0, rotation 200 r/min. And C2 was identified as Bacillus amyloliquefaciens.
基金supported by the Climate Change Response Project (NRF-2019M1A2A2065612)the Brainlink Project (NRF2022H1D3A3A01081140)+3 种基金the NRF-2021R1A4A3027878 and the No. RS-2023-00212273 funded by the Ministry of Science and ICT of Korea via National Research Foundationresearch funds from Hanhwa Solutions Chemicals (1.220029.01)UNIST (1.190013.01)supported by the Institute for Basic Science (IBS-R019-D1)。
文摘Electrochemical N_(2) reduction reaction(eNRR) over Cu-based catalysts suffers from an intrinsically low activity of Cu for activation of stable N_(2) molecules and the limited supply of N_(2) to the catalyst due to its low solubility in aqueous electrolytes.Herein,we propose phosphorus-activated Cu electrocatalysts to generate electron-deficient Cu sites on the catalyst surface to promote the adsorption of N_(2) molecules.The eNRR system is further modified using a gas diffusion electrode(GDE) coated with polytetrafluoroethylene(PTFE) to form an effective three-phase boundary of liquid water-gas N_(2)-solid catalyst to facilitate easy access of N_(2) to the catalytic sites.As a result,the new catalyst in the flow-type cell records a Faradaic efficiency of 13.15% and an NH_(3) production rate of 7.69 μg h^(-1) cm^(-2) at-0.2 V_(RHE),which represent 3.56 and 59.2 times increases from those obtained with a pristine Cu electrode in a typical electrolytic cell.This work represents a successful demonstration of dual modification strategies;catalyst modification and N_(2) supplying system engineering,and the results would provide a useful platform for further developments of electrocatalysts and reaction systems.
基金supported by the Ningbo Public Welfare Science and Technology Program (No.2022S097)the Fundamental Research Funds for the Central Universities (Nos.2019B17914,B210206006).
文摘The utilization of aquaculture wastewater as irrigation is an effective way to recycle and reuse water and nitrogen fertilizer resources because it contains numerous nutrients.However,it is still unclear that the pattern of substituting aquaculture wastewater irrigation for fertilizer supplementing is conducive to improving the soil nitrogen status,fruit yield and water-fertilizer use efficiency for tomato production.In this context,the experiment was intended to establish the appropriate irrigation regime of aquaculture wastewater in tomato production for freshwater replacement and fertilizer reduction to ensure good yields.Pot experiments were conducted with treatments as farmers accustomed to irrigation and fertilization used as control(CK),1.75 L aquaculture wastewater with base fertilizer(W1),2 L aquaculture wastewater with base fertilizer;and 2.25 L aquaculture wastewater with base fertilizer(W3).We examined the effects of aquaculture wastewater irrigation on soil nitrogen distribution,Nrelated hydrolases,tomato yield,and economic benefits.The results showed that the control treatment had the highest N input,about 24.68%higher than the W3 treatment,while the yield was only about 7.81%higher than W3.This indicated that the overuse of chemical fertilizer was present in the current tomato production.Although the reduction of fertilizer in aquaculture wastewater irrigation caused a decrease in tomato production,this economic loss can be compensated by cost savings in the wastewater disposal.Among aquaculture wastewater treatments,the W3 treatment had the highest overall benefit,achieving 62.63%freshwater savings,37.50%fertilizer input reduction,and an economic return of approximately 19,466 Yuan per hectare higher than the control.Additionally,increasing the irrigation volume of aquaculture wastewater could provide more available nutrients to the soil,which were more prevalent in the form of organic nitrogen.The lower soil nitrate reductase activities(NR)under aquaculture wastewater treatments after harvesting also proved that this pattern was beneficial to reduce soil nitrate nitrogen residues.Overall,the results demonstrate that aquaculture wastewater irrigation alleviates the soil nitrate residues,improves nutrient availability,and results in more economic returns with water and fertilizer conservation for the greenhouse production of tomatoes.
文摘This paper presents lab-scale experiment carried out to evaluate the c orrelation between ammonia nitrogen(NH3-N) and p-toluidine using sequencing batc h reactor treating synthetic p-toluidine wastewater. The profiles of NH3-N and p -toluidine were traced under the concentration of sucrose in the influent varied from 0 to 500 mg/L, aerated airflow varied from 0.6 to 1.2 L/min and temperatur e varied from 10 to 25℃, respectively. The results showed that the concentratio n of NH3-N turned from increase to decrease when p-toluidine was nearly complete ly biodegraded, so the profile of NH3-N could clearly indicate the endpoint of p -toluidine biodegradation. And the profile of NH3-N was not influenced by the su crose in the influent, aerated airflow and temperature. It is showed that using ammonia nitrogen as monitoring and control parameter is feasible and reliable an d has promising application in amine wastewater treatment by SBR.
基金Supported by National Key Project of Science and Technology of Water Pollution Control and Management(2009ZX07212-001-04)
文摘[Objective]The study aimed to discuss the feasibility and optimal conditions of removing ammonia nitrogen by using microwave coupled with active carbon. [Method]In the study,a novel process,microwave radiation coupled with active carbon,was applied to remove ammonia nitrogen from wastewater,and the influences of solution pH,air conditions,active carbon usage,microwave power and time on the removal effect of ammonia nitrogen were studied. [Result]Microwave coupled with active carbon can remove ammonia nitrogen efficiently,and pumping air into the wastewater can also increase the removal rate of ammonia nitrogen to a certain extent. Higher pH,intensive microwave power and longer treating time could also increase the removal rate of ammonia nitrogen using microwave radiation coupled with active carbon,whereas the usage of active carbon contributed a small impact. It was proved that microwave coupled with active carbon was an effective method for the removal of ammonia nitrogen from wastewater. Meanwhile,the orthogonal experiment results showed that the removal rate of ammonia nitrogen reached 92. 5% under the optimal conditions,that is,the usage of active carbon was 0. 5 g,pH =11,microwave radiation power was 850 W,and microwave action time was 4 minutes. [Conclusion]The research provided a new method to remove ammonia nitrogen from wastewater,namely microwave coupled with active carbon.
文摘Fluid catalytic cracking (FCC) salty wastewaters, containing quaternary ammonium compounds (QACs), are very difficult to treat by biochemical process. Anoxic/oxic (A/O) biochemical system, based on nitrification and denitrification reactions, was used to assess their possible biodegradation. Because of the negative effects of high salt concentration (3%), heavy metals and toxic organic matter on microorganisms’ activities, some techniques consisting of dilution, coagulation and flocculation, and ozonation pretreatments, were gradually tested to evaluate chemical oxygen demand (COD), ammonia-nitrogen (ammonia-N) and total nitrogen (TN) removal rates. In this process of FCC wastewater, starting with university-domesticated sludge, the ammonia-N and TN removal rates were worst. However, when using domesticated SBR’s sludge and operating with five-fold daily diluted influent (thus reducing salt concentration), the ammonia-N removal reached about 57% while the TN removal rate was less than 37% meaning an amelioration of the nitrification process. However, by reducing the dilution factors, these results were inflected after some days of operation, with ammonia-N removal decreasing and TN barely removed meaning a poor nitrification. Even by reducing heavy metals concentration with coagulation/flocculation process, the results never changed. Thereafter, by using ozonation pre-treatment to degrade the detected organic matter of di-tert-butylphenol and certain isoparaffins, COD, ammonia-N and TN removal rates reached 92%, 62% and 61%, respectively. These results showed that the activities of the microorganisms were increased, thus indicating a net denitrification and nitrification reactions improvement.
基金supported by the Major Science and Technology Program of Zhejiang Province,China(Grant No. 2009C12001)the National Natural Science Foundation of China (Grant No. 31172030)the International Science and Technology Cooperation Program (Grant No. 2011DFA91190)
文摘The effects of different nitrogen application levels on nutrient uptake and ammonia volatilization were studied with the rice cultivar Zheyou 12 as a material.The accumulative amounts of nitrogen,phosphorus and potassium in rice plants across all growth stages showed a trend to increase with increasing nitrogen application levels from 0 to 270 kg/hm 2,but decreased at nitrogen application levels exceeding 270 kg/hm 2.Moreover,the accumulative uptake of nitrogen,phosphorus and potassium by the rice plants was increased by application of organic manure in combination with 150 kg/hm 2 nitrogen.The nitrogen uptake was high during the jointing to heading stages.Correlation analysis showed that rice yield was positively correlated with the accumulative uptake of nitrogen,phosphorus and potassium by the rice plants.The highest correlation coefficient observed was between the amount of nitrogen uptake and rice yield.The rate and accumulative amounts of ammonia volatilization increased with increasing nitrogen fertilizer application level.Compared with other stages,the rate and accumulative amount of ammonia volatilization were higher after base fertilizer application.The ammonia volatilization rates in response to the nitrogen application levels of 270 kg/hm 2 and 330 kg/hm 2 were much higher than those in the other treatments.The loss of nitrogen through ammonia volatilization accounted for 23.9% of the total applied nitrogen at the nitrogen application level of 330 kg/hm 2.
基金supported by the National Major Project of Water Pollution Control and Management Technology in China (No.2013ZX07202-007)the Shenzhen Science and Technology Project (No.GRCK2017042116092660)the National Natural Science Foundation of China (No.51308066)。
文摘This study aimed to present a novel clay/biochar composite adsorption particle, which made from abandoned reed straw and clay to remove ammonia nitrogen(NH4^+-N) from micro-contaminated water. The removal performance of NH4^+-N by composite adsorption particle was monitored under different raw material proportions and initial NH4^+-N concentration. Besides, adsorption kinetics and adsorption isotherms were investigated to reveal the adsorption mechanisms. The results showed that NH4^+-N was effectively removed under optimal proportion of biochar, foaming agent and crosslinker with 20%, 3%, and 3%, respectively. The optimal contact time was 150 min and the best removal efficiency was 88.6% at initial NH4^+-N concentration of 20 mg L^-1. The adsorption performance was well described by the second order kinetic model and Freundlich model. The novel clay/biochar composite adsorption particle in this study demonstrated a high potential for NH4^+-N removal from surface water.
基金Sponsored by the National Basic Research Program of China (973 Program)(Grant No. 2004CB418505)
文摘In this study,a three-stage biological aerated filter(BAF) system was proposed for the enhancement of nitrogen removal in the treatment of low carbon-to-nitrogen ratio(C/N ratio) municipal wastewater.Operational parameters were studied for each process for maximum nitrite accumulation in the nitrification step and nitrite adaptation in the denitrification step.Nitrite accumulation during nitrification could be controlled by the dissolved oxygen(DO) concentration,presenting a mean value of 40% at around 1.0 mg DO/L.Denitrification could be adapted to nitrite and the process was stable if nitrite in the reactor was keep low.Once the operational parameters were established,the process was stable and a steady state was maintained for over 30 days,and the various indexes of discharged water were up to the Discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002) Level-one A.It was concluded that the three-stage BAF system proposed in this study was excellent in nitrogen removal performance by employing three-column functioning as short-cut nitrification,short-cut denitrification and secondary nitrification,respectively.
基金supported by the National Natural Science Foundation of China (Grant No.30671223)the 11th 5-year Major Project of National Science and Technology Support Plan (GrantNo. 2006BAD02A03)
文摘We conducted field trials of rice grown in sandy soil and clay soil to determine the effects of nitrogen application levels on the concentration of NH4+-N in surface water,loss of ammonia through volatilization from paddy fields,rice production,nitrogen-use efficiency,and nitrogen content in the soil profile.The concentration of NH4+-N in surface water and the amount of ammonia lost through volatilization increased with increasing nitrogen application level,and peaked at 1-3 d after nitrogen application.Less ammonia was lost via volatilization from clay soil than from sandy soil.The amounts of ammonia lost via volatilization after nitrogen application differed depending on the stage when it was applied,from the highest loss to the lowest:N application to promote tillering > the first N topdressing to promote panicle initiation(applied at the last 4-leaf stage) > basal fertilizer > the second N topdressing to promote panicle initiation(applied at the last 2-leaf stage).The total loss of ammonia via volatilization from clay soil was 10.49-87.06 kg/hm2,equivalent to 10.92%-21.76% of the nitrogen applied.The total loss of ammonia via volatilization from sandy soil was 11.32?102.43 kg/hm2,equivalent to 11.32%-25.61% of the nitrogen applied.The amount of ammonia lost via volatilization and the concentration of NH4+-N in surface water peaked simultaneously after nitrogen application;both showed maxima at the tillering stage with the ratio between them ranging from 23.76% to 33.65%.With the increase in nitrogen application level,rice production and nitrogen accumulation in plants increased,but nitrogen-use efficiency decreased.Rice production and nitrogen accumulation in plants were slightly higher in clay soil than in sandy soil.In the soil,the nitrogen content was the lowest at a depth of 40-50 cm.In any specific soil layer,the soil nitrogen content increased with increasing nitrogen application level,and the soil nitrogen content was higher in clay soil than in sandy soil.In terms of ammonia volatilization,the amount of ammonia lost via volatilization increased markedly when the nitrogen application level exceeded 250 kg/hm2 in the rice growing season.However,for rice production,a suitable nitrogen application level is approximately 300 kg/hm2.Therefore,taking the needs for high crop yields and environmental protection into account,the appropriate nitrogen application level was 250-300 kg/hm2 in these conditions.
文摘A Florida wastewater treatment facility studied how Simultaneous Nitrification Denitrification (SND) coupled with traditional nitrogen removal would be used to meet the state’s current advanced wastewater treatment nutrient criterion. This study examined the effect of these combined processes on the fate and transport of the nitrogen species during the treatment process. The effectiveness of nitrogen removal within the full scale sequential batch reactor system (SBR) and the extent of SND compared to nitrification and denitrification in the nitrogen removal process was also evaluated. Finally, the overall performance of the municipal wastewater treatment facility utilizing these combined processes was evaluated. Overall, this application reduced the total nitrogen to almost 6% of the permitted concentration of 3.0 mg/L. The combination of both processes also resulted in an actual ?concentration 93.7% lower than the acceptable theoretical ?concentration, which also resulted in effluent Total Inorganic Nitrogen nearly 80% lower than the permitted 3.0 mg/L effluent concentration. Further, the process produced a composite Total Nitrogen concentration that was 74% lower than the permitted concentration. This coupling of SND with traditional nitrogen removal resulted in a highly effective process to reduce nitrogen in the municipal wastewater effluent which is also attractive for potential implementation due to the low cost expenditure incurred in its utilization.
基金Project(51174017) supported by the National Natural Science Foundation of China
文摘The characteristics of the zeolite modified by microwave and sodium acetate and its sorption of ammonia-nitrogen from simulated water sample were investigated.The results show that the modified zeolite by microwave-sodium acetate(SMMZ)has a high sorption efficiency and removal performance.The ammonia-nitrogen removal rate of SMMZ reaches 92.90%.The surface of SMMZ becomes loose and some pores appear,the specific surface area,total pore volume and average pore diameter increase after modification.Compared to the natural zeolite,SMMZ has a more concentrated pore size distribution in the range of 0-10 nm.The cation exchange capacity(CEC)of SMMZ is higher than that of the natural zeolite.And the ammonia nitrogen removal rate is consistent with the change of CEC.The SMMZ possesses rapid sorption and slow balance characteristics and ammonia-nitrogen sorption is consistent with both Langmuir adsorption isotherm model and Freundlich adsorption isotherm model.The adsorption kinetics of ammonia-nitrogen follows the pseudo-second order kinetic model.
基金supported by the Key Projects in National Science & Technology Pillar Program during the Eleventh Five-Year Plan Period (No.2006BAC19B01-02)the Mega-projects of Science Research for Water (No.2008ZX07313-3)the Program of Introducing Talents of Discipline to Universities
文摘We investigated the communities of ammonia-oxidizing bacteria(AOB) in activated sludge collected from eight wastewater treatment systems using polymerase chain reaction(PCR) followed by terminal restriction fragment length polymorphism(T-RFLP),cloning,and sequencing of the α-subunit of the ammonia monooxygenase gene(amoA).The T-RFLP fingerprint analyses showed that different wastewater treatment systems harbored distinct AOB communities.However,there was no remarkable difference among the AOB TRFLP profiles from different parts of the same system.The T-RFLP fingerprints showed that a full-scale wastewater treatment plant(WWTP) contained a larger number of dominant AOB species than a pilot-scale reactor.The source of influent affected the AOB community,and the WWTPs treating domestic wastewater contained a higher AOB diversity than those receiving mixed domestic and industrial wastewater.However,the AOB community structure was little affected by the treatment process in this study.Phylogenetic analysis of the cloned amoA genes clearly indicated that all the dominant AOB in the systems was closely related to Nitrosomonas spp.not to Nitrosospira spp.Members of the Nitrosomonas oligotropha and Nitrosomonas communis clusters were found in all samples,while members of Nitrosomonas europaea cluster occurred in some systems.
基金the National Natural Science Foundation of China(40801097)the Natural Science Foundation of Fujian Province,China(2012J01107)
文摘Ammonia oxidation, the first and rate-limiting step of nitrification, is carried out by both ammonia-oxidizing bacteria(AOB) and ammonia-oxidizing archaea(AOA). However, the relative importance of AOB and AOA to nitrifi cation in terrestrial ecosystems is not well understood. The aim of this study was to investigate the effect of the nitrogen input amount on abundance and community composition of AOB and AOA in red paddy soil. Soil samples of 10-20 cm(root layer soil) and 0-5 cm(surface soil) depths were taken from a red paddy. Rice in the paddy was fertilized with different rates of N as urea of N1(75 kg N ha-1 yr-1), N2(150 kg N ha-1 yr-1), N3(225 kg N ha-1 yr-1) and CK(without fertilizers) in 2009, 2010 and 2011. Abundance and community composition of ammonia oxidizers was analyzed by real-time PCR and denaturing gradient gel electrophoresis(DGGE) based on amoA(the unit A of ammonia monooxygenase) gene. Archaeal amoA copies in N3 and N2 were signifi cantly(P<0.05) higher than those in CK and N1 in root layer soil or in surface soil under tillering and heading stages of rice, while the enhancement in bacterial amoA gene copies with increasing of N fertilizer rates only took on in root layer soil. N availability and soil NO3--N content increased but soil NH4+-N content didn't change with increasing of N fertilizer rates. Otherwise, the copy numbers of archaeal amoA gene were higher(P<0.05) than those of bacterial amoA gene in root lary soil or in surface soil. Redundancy discriminate analysis based on DGGE bands showed that there were no obvious differs in composition of AOA or AOB communities in the field among different N fertilizer rates. Results of this study suggested that the abundance of ammonia-oxidizers had active response to N fertilizer rates and the response of AOA was more obvious than that of AOB. Similarity in the community composition of AOA or AOB among different N fertilizer rates indicate that the community composition of ammonia-oxidizers was relatively stable in the paddy soil at least in short term for three years.
基金The National Natural Science Foundation of China (No. 30170011)
文摘Three new bacteria HS-03, HS-043 and HS-047 isolated from different ec osystems were found capable of aerobic denitrification. The potential applicatio n of these strains in wastewater treatment under aerobic conditions was investig ated. These three bacteria all presented high nitrogen removal from wastewater t hat more than 98% of 10 mmol/L nitrate could be removed in 12—24 h by adding ch eap external carbon source and low concentration of iron as well as molybdate. T he mechanism at molecular level was analyzed. The success of this aerobic denitr ification applied to wastewater treatment may serve as an alternative to enhance the practical nitrogen removal from wastewater. Main biochemical and physiologi cal features of these strains were characterized. The 16S rDNA sequences were co mpared with the published data in GenBank by using BLAST. The results of phenoty pe and genotype proved that strain HS-03 and HS-047 belonged to Pseudomonas stut zeri and Pseudomonas pseudoalcaligenes respectively. Strain HS-043 was identifie d as Delftia acidovorans of which denitrifying activity has not previously been explored.
文摘The distillery wastewater of Guangdong Jiujiang Distillery, which is c haracteristic of containing high organic matters and rich total nitrogen, was tr eated by a combination of methane fermentation and denitrification/nitrification processes. 80% of COD in the raw wastewater was removed by methane fermentation at the COD volumetric loading rate of 20 kg COD/(m3·d) using the expanded gra nule sludge bed (EGSB) process. However, almost all the organic nitrogen in the raw wastewater was converted into ammonia by ammonification there. Ammonia and v olatile fatty acids (VFA) remaining in the anaerobically treated wastewater were simultaneously removed utilizing VFA as an electron donor by denitrification oc curring in the other EGSB reactor and nitrification using PEG-immobilized nitrif ying bacteria with recirculation process. An aerobic biological contact oxidizat ion reactor was designed between denitrification/nitrification reactor for furth er COD removal. With the above treatment system, 18000—28000 mg/L of COD in raw wastewater was reduced to less than 100 mg/L. Also, ammonia in the effluent of the system was not detected and the system had a high removal rate for 900—1200 mg/L of TN in the raw wastewater, only leaving 400 mg/L of nitrate nitrogen.
