Alternating shortcut nitrification-denitrification for nitrogen removal from soybean wastewater by SBR with real-time control

A novel treating technology for nitrogen removal from soybean wastewater was studied. The process for nitrogen removal was achieved by alternating aeration and mixing, combined with real\|time control strategies. Results showed that the COD and total nitrogen removal rates are more than 90% and 92% at COD and total nitrogen loads of 1\^0-1\^2 kg COD/(kgMLSS·d) and 0\^20-0\^27 kg TN/(kgMLSS·d), respectively. In addition, it could improve sludge settling property. SVI value is less than 70 g/ml during the whole cycles. The method not only may be adapted to treat soybean wastewater with high nitrogen, but also may be applied to treat other high nitrogen wastewater.

An innovative membrane bioreactor and packed-bed biofilm reactor combined system for shortcut nitrification-denitrification

An innovative shortcut biological nitrogen removal system, consisting of an aerobic submerged membrane bioreactor （MBR） and an anaerobic packed-bed biofilm reactor （PBBR）, was evaluated for treating high strength ammonium-bearing wastewater. The system was seeded with enriched ammonia-oxidizing bacteria （AOB） and operated without sludge purge with a decreased hydraulic retention time （HRT） through three phases. MBR was successful in both maintaining nitrite ratio over 0.95 and nitrification efficiency higher than 98% at HRT of 24 h, and PBBR showed satisfactory denitrification efficiency with very low effluent nitrite and nitrate concentration （both below 3 mg/L）. By examining the nitrification activity of microorganism, it was found that the specifc ammonium oxidization rate （SAOR） increased from 0.17 to 0.51 g N/（g VSS.d） and then decreased to 0.22 g N/（g VSS.d） at the last phase, which resulted from the accumulation of extracellular polymers substances （EPS） and inert matters enwrapping around the zoogloea. In contrast, the average specific nitrite oxidization rate （SNOR） is 0.002 g N/（g VSS.d）, only 1% of SAOR. Because very little Nitrobactor has been detected by fluorescence in situ hybridization （FISH）, it is confirmed that the stability of high nitrite accumulation in MBR is caused by a large amount of AOB.

Evaluation of the stability of shortcut nitrification-denitrification process based on online specific oxygen uptake rate monitoring

Shortcut nitrification-denitrification(SCND)is widely concerned because of its low energy consumption and high nitrogen removal efficiency.However,the current difficulty lies in the stable maintenance of SCND performance,which leads to the challenge of large-scale application of this new denitrification technology.In this study,the nitrogen removal pathway from complete nitrification-denitrification(CND)to SCND was rapidly realized under high free ammonia(FA),high pH and low dissolved oxygen(DO)conditions.The variations of specific oxygen uptake rate(SOUR)of activated sludge in both processes were investigated by an online SOUR monitoring device.Different curves of SOUR from CND to SCND process were observed,and the ammonia peak obtained based on SOUR monitoring could be used to control aeration time accurately in SCND process.Accordingly,the SOUR ratio of ammonia oxidizing bacteria(AOB)to nitrite oxidizing bacteria(NOB)(SOURAOB/SOURNOB)was increased from 1.40 to 2.93.16S rRNA Miseq high throughput sequencing revealed the dynamics of AOB and NOB,and the ratio of relative abundance(AOB/NOB)was increased from 1.03 to 3.12.Besides,SOURAOB/SOURNOB displayed significant correlations to ammonia removal rate(P<0.05),ammonia oxidation rate/nitrite oxidation rate(P<0.05),nitrite accumulation rate(P<0.05)and the relative abundance of AOB/NOB(P<0.05).Thus,a strategy for evaluation the SCND process stability based on online SOUR monitoring is proposed,which provides a theoretical basis for optimizing the SCND performance.

Taxonomic and functional variations in the microbial community during the upgrade process of a full-scale landfill leachate treatment plant-from conventional to partial nitrification-denitrification

Because of the low access to biodegradable organic substances used for denitrification,the partial nitrification-denitrification process has been considered as a low-cost,sustainable alternative for landfill leachate treatment.In this study,the process upgrade from conventional to partial nitrificationdenitrification was comprehensively investigated in a full-scale landfill leachate treatment plant(LLTP).The partial nitrification-denitrification system was successfully achieved through the optimizing dissolved oxygen and the external carbon source,with effluent nitrogen concentrations lower than 150 mg/L.Moreover,the upgrading process facilitated the enrichment of Nitrosomonas(abundance increased from 0.4%to 3.3%),which was also evidenced by increased abundance of amoA/B/C genes carried by Nitrosomonas.Although Nitrospira(accounting for 0.1%-0.6%)was found to stably exist in the reactor tank,considerable nitrite accumulation occurred in the reactor(reaching 98.8 mg/L),indicating high-efficiency of the partial nitrification process.Moreover,the abundance of Thauera,the dominant denitrifying bacteria responsible for nitrite reduction,gradually increased from 0.60%to 5.52%during the upgrade process.This process caused great changes in the microbial community,inducing continuous succession of heterotrophic bacteria accompanied by enhanced metabolic potentials toward organic substances.The results obtained in this study advanced our understanding of the operation of a partial nitrification-denitrification system and provided a technical case for the upgrade of currently existing full-scale LLTPs.

Effects of seawater salinity on nitrite accumulation in short-range nitrification to nitrite as end product

The effect of seawater salinity on nitrite accumulation in short-range nitrification to nitrite as the end product was studied by using a SBR. Experimental results indicated that the growth of nitrobacteria was inhibited and very high levels of nitrite accumulation at different salinities were achieved under the conditions of 25—28℃, pH 7.5? ?.0 , and the influent ammonia nitrogen of 40—70 mg/L when seawater flow used to flush toilet was less than 35%(salinity 12393 mg/L, Cl - 6778 mg/L) of total domestic wastewater flow, which is mainly ascribed to much high chlorine concentration of seawater. Results showed that high seawater salinity is available for short-range nitrification to nitrite as the end product. When the seawater flow used to flush toilet accounting for above 70% of the total domestic wastewater flow, the removal efficiency of ammonia was still above 80% despite the removal of organics declined obviously(less than 60%). It was found that the effect of seawater salinity on the removal of organics was negative rather than positive one as shown for ammonia removal.

Influence of influent on anaerobic ammonium oxidation in an Expanded Granular Sludge Bed-Biological Aerated Filter integrated system

Shortcut nitrification-denitrification,anaerobic ammonium oxidation(ANAMMOX),and methanogenesis have been successfully coupled in an Expanded Granular Sludge Bed-Biological Aerated Filter(EGSB-BAF)integrated system.As fed different synthetic wastewater with chemical oxygen demand(COD)of 300-1200 mg·L^(-1)and NH_(4)^(+)-N of 30-120 mg·L^(-1)at the outer recycle ratio of 200%,the influence of influent on ANAMMOX in the integrated system was investigated in this paper.The experimental results showed that higher COD concentration caused an increase in denitrification and methanogenesis but a decrease in ANAMMOX;however,when an influent with the low concentration of COD was used,the opposite changes could be observed.Higher influent NH_(4)^(+)-N concentration favored ANAMMOX when the COD concentration of influent was fixed.Therefore,low COD=NH_(4)^(+)-N ratio would decrease competition for nitrite between ANAMMOX and denitrification,which was favorable for reducing the negative effect of organic COD on ANAMMOX.The good performance of the integrated system indicated that the bacterial community of denitrification,ANAMMOX,and methanogenesis could be dynamically maintained in the sludge of EGSB reactor for a certain range of influent.

Treatment of coking wastewater using oxic-anoxic-oxic process followed by coagulation and ozonation

An oxic-anoxic-oxic(O-A-O)system followed by coagulation and ozonation processes was used to study the treatment of coking wastewater.In the O-A-O process,the removals of NH4+-N,total nitrogen and COD were 91.5-93.3%,91.3-92.6%and 89.1-93.8%,respectively when employing hydraulic residence times of 60 h for the biochemical system.High removal of NH4+-N was obtained due to the placement of an aerobic tank in front of A-O system which can mitigate the inhibitory effect of toxic compounds in coking wastewater on nitrifying bacteria.Addition of methanol into the anoxic reactor greatly increased the removal of total nitrogen,indicating that denitrifiers can hardly use organic compounds in coking wastewater as carbon source for denitrification.COD values of the effluent from the O-A-O system were still higher than 260 mg/L even with a prolonged time of 160 h mainly due to the high refractory properties of residual compounds in the effluent.The subsequent coagulation and ozonation processes resulted in the COD removal of 91.5%-93.3%and reduced the relative abundance of large molecular weight(MW)organics(>1 kDa)from 55.8%to 20.93%with the ozone,PAC and PAM dosages of 100,150 and 4 mg/L respectively.Under these conditions,the COD value and concentration of polycyclic aromatic hydrocarbons in the final effluent were less than 80 and 0.05 mg/L,respectively,which meet the requirement of the Chinese emission standard.These results indicate that the combined technology of O-A-O process,coagulation and ozonation is a reliable way for the treatment of coking wastewater.

Enhancing nitrogen removal from low carbon to nitrogen ratio wastewater by using a novel sequencing batch biofilm reactor

Removing nitrogen from wastewater with low chemical oxygen demand/total nitrogen （COD/TN） ratio is a difficult task due to the insufficient carbon source available for denitrification. Therefore, in the present work, a novel sequencing batch biofilm reactor （NSBBR） was developed to enhance the nitrogen removal from wastewater with low COD/ TN ratio. The NSBBR was divided into two units separated by a vertical clapboard. Alternate feeding and aeration was performed in the two units, which created an anoxie unit with rich substrate content and an aeration unit deficient in substrate simultaneously. Therefore, the utilization of the influent carbon source for denitrification was increased, leading to higher TN removal compared to conventional SBBR （CSBBR） operation. The results show that the CSBBR removed up to 76.8%, 44.5% and 10.4% of TN, respectively, at three tested COD/TN ratios （9.0, 4.8 and 2.5）. In contrast, the TN removal of the NSBBR could reach 81.9%, 60.5% and 26.6%, respectively, at the corresponding COD/TN ratios. Therefore, better TN removal performance could be achieved in the NSBBR, especially at low CODfrN ratios （4.8 and 2.5）. Furthermore, it is easy to upgrade a CSBBR into an NSBBR in practice.