Effect of carbon source and nitrate concentration on denitrifying phosphorus removal by DPB sludge

Effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by DPB sludge was systematically studied using batch experiments, at the same time the variation of ORP was investigated.Results showed that the denitrifying and phosphorus uptake rate in anoxic phase increased with the high initial anaerobic carbon source addition. However once the initial COD concentration reached a certain level, which was in excess to the PHB saturation of poly-P bacteria, residual COD carried over to anoxic phase inhibited the subsequent denitrifying phosphorus uptake. Simultaneously, phosphate uptake continued until all nitrate was removed, following a slow endogenous release of phosphate. High nitrate concentration in anoxic phase increased the initial denitrffying phosphorus rate. Once the nitrate was exhausted, phosphate uptake changed to release. Moreover, the time of this turning point occurred later with the higher nitrate addition. On the other hand, through on-line monitoring the variation of the ORP with different initial COD concentration, it was found ORP could be used as a control parameter for phosphorus release, but it is impossible to utilize ORP for controlling the denitrificaion and anoxic phosphorus uptake operations.     

Effect of carbon source on the denitrification in constructed wetlands

The ability of constructed wetlands with di erent plants in nitrate removal were investigated. The factors promoting the rates of denitrification including organic carbon, nitrate load, plants in wetlands, pH and water temperature in field were systematically investigated. The results showed that the additional carbon source (glucose) can remarkably improve the nitrate removal ability of the constructed wetland. It demonstrated that the nitrate removal rate can increase from 20% to more than 50% in summer and from 10% to 30% in winter, when the nitrate concentration was 30–40 mg/L, the retention time was 24 h and 25 mg/L dissolved organic carbon (DOC) was ploughed into the constructed wetland. However, the nitrite in the constructed wetland accumulated a little with the supply of the additional carbon source in summer and winter, and it increased from 0.15 to 2 mg/L in the e uent. It was also found that the abilities of plant in adjusting pH and temperature can result in an increase of denitrification in wetlands. The seasonal change may also impact the denitrification.     

Determination of operational parameters of anaerobic phase for enhanced phosphorus removal in MBR

Two runs of experiments were carried out to obtain an understanding of phosphorus release and uptake under the anaerobic condition and then the aerobic condition respectively. Under anaerobic condition, it was found that the extent of phosphorus release appeared to increase with the increase of the initial organic loading rate when the initial organic loading rate was up to 0. 1 gSCOD/gMLSS.When the initial organic loading rate was higher than 0. 1 gSCOD/gMLSS, the amount of phosphorus release per unit mass of MLSS reached heady a same stationary value, and it seemed this is not affected by organic loading rate when there is extemal available substrate remained. In addition, the effect of NOx-N on the phosphorus release and uptake was also investigated, it was proved that the denitrifiers has an advantage over polyphosphate accumulating bacteria in competition for organic substrate under anoxic condition. Therefore, the existence of NOx-N is disadvantageous to the phosphorus release. Based upon the above investigations, the process configuration of membrane bioreactor(MBR) in combination with anaerobic phase was proposed to enhance the removal of phosphorus in treating domestic wastewater. Dunng the experimental period of four months, average removals of 92.50%, 84.25%, 100%, 94.09% and 85.33% were achieved for COD, TP, SS, NH3-N and TN respectively.     

Comparison of biochemical characteristics between PAO and DPAO sludges

A successful enhanced biological phosphorus removal(EBPR) was observed in both anaerobicaerobic sequencing batch reactor(An-Ox SBR) to induce growth of phosphorus accumulating organism(PAO) and anaerobic-anoxic(An-Ax) SBR to induce growth of denitrifying PAO(DPAO).Although the EBPR performance of An-Ox SBR was higher by 11.3% than that of An-Ax SBR,specific phosphorus release rates in the An-Ax SBR(22.8 ± 3.5 mg P/(g VSS·hr)) and the An-Ox SBR(22.4 ± 4.8 mg P/(g VSS·hr)) were similar. Specific phosphorus uptake rates under anoxic and aerobic conditions were 26.3 ± 4.8 mg P/(g VSS·hr)(An-Ax SBR) and 25.6 ± 2.8 mg P/(g VSS·hr)(An-Ox SBR), respectively, which were also similar. In addition, an analysis of relationship of poly-β-hydroxyalkanoates(PHA) synthesized under anaerobic conditions with phosphorous release(Preleased/PHAsynthesized) and of PHA utilized under anoxic and aerobic conditions with phosphorous uptake(Puptaked/PHAutilized) verified that biological activities of EBPR per unit biomass between DPAO and PAO were similar. An analysis of the specific denitrification rate of DPAO showed that NO-3-N can be denitrified at a rate that does not substantially differ from that of an ordinary denitrifier without additional consumption of organic carbon when the PHA stored inside the cell under anaerobic conditions is sufficiently secured.     

Effect of the C:N:P ratio on the denitrifying dephosphatation in a sequencing batch biofilm reactor (SBBR)

A series of investigations were conducted using sequencing batch biofilm reactor(SBBR) to explore the influence of C:N:P ratio on biological dephosphatation including the denitrifying dephosphatation and the denitrification process.Biomass in the reactor occurred mainly in the form of a biofilm attached to completely submerged disks.Acetic acid was used as the source of organic carbon.C:N:P ratios have had a significant effect on the profiles of phosphate release and phosphate uptake and nitrogen removal.The highest rates of phosphate release and phosphate uptake were recorded at the C:N:P ratio of 140:70:7.The C:N ratio of 2.5:1 ensured complete denitrification.The highest rate of denitrification was achieved at the C:N:P ratio of 140:35:7.The increase of nitrogen load caused an increase in phosphates removal until a ratio C:N:P of 140:140:7.Bacteria of the biofilm exposed to alternate conditions of mixing and aeration exhibited enhanced intracellular accumulation of polyphosphates.Also,the structure of the biofilm encouraged anaerobic–aerobic as well as anoxic–anaerobic and absolutely anaerobic conditions in a SBBR.These heterogeneous conditions in the presence of nitrates may be a significant factor determining the promotion of denitrifying polyphosphate accumulating organism(DNPAO) development.     

Effect of dissolved oxygen on nitrate removal using polycaprolactone as an organic carbon source and biofilm carrier in fixed-film denitrifying reactors

Nitrate-nitrogen(NO_3~--N) always accumulates in commercial recirculating aquaculture systems(RASs) with aerobic nitrification units. The ability to reduce NO_3~--N consistently and confidently could help RASs to become more sustainable. The rich dissolved oxygen(DO)content and sensitive organisms stocked in RASs increase the difficulty of denitrifying technology. A denitrifying process using biologically degradable polymers as an organic carbon source and biofilm carrier was proposed because of its space-efficient nature and strong ability to remove NO_3~--N from RASs. The effect of dissolved oxygen(DO) levels on heterotrophic denitrification in fixed-film reactors filled with polycaprolactone(PCL) was explored in the current experiment. DO conditions in the influent of the denitrifying reactors were set up as follows: the anoxic treatment group(Group A, average DO concentration of 0.28 ± 0.05 mg/L), the low-oxygen treatment DO group(Group B, average DO concentration of 2.50 ± 0.24 mg/L) and the aerated treatment group(Group C, average DO concentration of 5.63 ± 0.57 mg/L). Feeding with 200 mg/L of NO_3~--N, the NO_3~--N removal rates were 1.53, 1.60 and 1.42 kg/m3PCL/day in Groups A, B and C, respectively. No significant difference in NO_3~--N removal rates was observed among the three treatments. It was concluded that the inhibitory effects of DO concentrations lower than 6 mg/L on heterotrophic denitrification in the fixed-film reactors filled with PCL can be mitigated.     

Phosphorus accumulation by bacteria isolated from a ontinuous-flow two-sludge system

In this article, polyphosphate-accumulating organisms （PAOs） from a lab-scale continuous-flow two-sludge system was isolated and identified, the different phosphorus accumulation characteristics of the isolates under anoxic and aerobic conditions were investigated. Two kinds of PAOs were both found in the anoxic zones of the two-sludge system, one of them utilized only oxygen as electron aeceptor, and the other one utilized either nitrate or oxygen as electron aeceptor. Of the total eight isolates, five isolates were capable of utilizing both nitrate and oxygen as electron acceptors to uptake phosphorus to some extent. And three of the five isolates showed good phosphorus accumulative capacities both under anoxic or aerobic conditions, two identified as Alcaligenes and one identified as Pseudomonas. Streptococcus was observed weak anoxic phosphorus accumulation because of its weak denitrification capacity, but it showed good phosphorus accumulation capacity under aerobic conditions. One isolates identified as Enterobacteriaceae was proved to be a special species of PAOs, which could only uptake small amounts of phosphorus under anoxic conditions, although its denitrification capacity and aerobic phosphorus accumulation capacity were excellent.     

Nitrogen removal via nitrite from municipal landfill leachate

A system consisting of a two-stage up-flow anaerobic sludge blanket (UASB), an anoxic/aerobic (A/O) reactor and a sequencing batch reactor (SBR), was used to treat landfill leachate. During operation, denitrification and methanogenesis took place simultaneously in the first stage UASB, and the e uent chemical oxygen demand (COD) was further removed in the second stage UASB. Then the denitrification of nitrite and nitrate in the returned sludge by using the residual COD was accomplished in the A/O reactor, and ammonia was removed via nitrite in it. Last but not least, the residual ammonia was removed in SBR as well as nitrite and nitrate which were produced by nitrification. The results over 120 d (60 d for phase I and 60 d for phase II) were as follows: when the total nitrogen (TN) concentration of influent leachate was about 2500 mg/L and the ammonia nitrogen concentration was about 2000 mg/L, the shortcut nitrification with 85%–90% nitrite accumulation was achieved stably in the A/O reactor. The TN and ammonia nitrogen removal e ciencies of the system were 98% and 97%, respectively. The residual ammonia, nitrite and nitrate produced during nitrification in the A/O reactor could be washed out almost completely in SBR. The TN and ammonia nitrogen concentrations of final e uent were about 39 mg/L and 12 mg/L, respectively.     

Simultaneous nitrogen and phosphor removal in an aerobic submerged membrane bioreactor

Simultaneous nitrification and denitrification （SND） effect and phosphor removal were investigated in a one-staged aerobic submerged membrane bioreactor on pilot-scale with mixed liquor suspended solids （MLSS） 19--20 g/L. The effects of DO concentration, sludge floc size distribution on SND were studied. Test results suggested that SND was successfully performed in the membrane bioreactor （MBR） and about 70% total nitrogen removal efficiency was achieved when DO concentration was set to 0.2-- 0.3 mg/L. The main mechanisms governing SND were the suitable sludge floc size and the low DO concentration which was caused by low oxygen transfer rate with such a high MLSS concentration in the MBR. In the meantime, phosphor removal was also studied with polymer ferric sulfate （PFS） addition and 14 mg/L dosage of PFS was proper for the MBR to remove phosphor. PFS addition also benefited the MBR operation owing to its reduction of extracellular polymer substances （EPS） of mixed liquor.     

Removal of nitrogen and phosphorus in a combined A2/O-BAF system with a short aerobic SRT

A bench-scale anaerobic/anoxic/aerobic process-biological aerated filter （A^2/O-BAF） combined system was carded out to treat wastewater with lower C/N and C/P ratios. The A^2/O process was operated in a short aerobic sludge retention time （SRT） for organic pollutants and phosphorus removal, and denitrification. The subsequent BAF process was mainly used for nitrification. The BAF effluent was partially returned to anoxic zone of the A^2/O process to provide electron acceptors for denitrification and anoxic P uptake. This unique system formed an environment for reproducing the denitdfying phosphate-accumulating organisms （DPAOs）. The ratio of DPAOs to phosphorus accumulating organisms （PAOs） could be maintained at 28% by optimizing the organic loads in the anaerobic zone and the nitrate loads into the anoxic zone in the A^2/O process. The aerobic phosphorus over-uptake and discharge of excess activated sludge was the main mechanism of phosphorus removal in the combined system. The aerobic SRT of the A^2/O process should meet the demands for the development of aerobic PAOs and the restraint on the nitrifiers growth, and the contact time in the aerobic zone of the A^2/O process should be longer than 30 min, which ensured efficient phosphorus removal in the combined system. The adequate BAF effluent return rates should be controlled with 1--4 mg/L nitrate nitrogen in the anoxic zone effluent of A^2/O process to achieve the optimal nitrogen and phosphorus removal efficiencies.     

不同电子受体对反硝化除磷菌缺氧吸磷的影响

利用厌氧/缺氧/好氧交替运行模式培养和富集反硝化除磷污泥,通过在缺氧段分别投加不同浓度的硝酸盐和亚硝酸盐,进行了反硝化除磷菌（DPB）在不同电子受体条件下的缺氧吸磷试验.结果表明,在保证有足够的硝酸盐电子受体的情况下,DPB的缺氧吸磷速率几乎不受硝酸盐浓度的影响,在试验条件下,缺氧阶段每消耗1 mg NO^-₃-N吸收约1 mg PO^３－_４-P;在一定浓度条件下,亚硝酸盐能够作为电子受体参与DPB反硝化吸磷,DPB在较低亚硝酸盐浓度（NO^-₂-N在5～20 mg/L范围）下的缺氧吸磷速率高于以硝酸盐为电子受体时的缺氧吸磷速率,并且缺氧吸磷速率在这个范围内随NO^-₂-N浓度的升高而降低;亚硝酸盐对DPB缺氧吸磷的抑制程度随其浓度的增加而增强,当NO^-₂-N≥35 mg/L时,DPB的缺氧吸磷反应几乎完全停止.     

反硝化除磷污泥的缺氧吸磷性能研究

为探讨反硝化除磷过程中污泥的缺氧吸磷性能,利用厌氧/缺氧强化驯化得到的反硝化除磷污泥,通过间歇性试验考察不同电子受体类型、不同污泥浓度(MLSS)对吸磷过程的影响。试验结果表明,缺氧条件下反硝化除磷菌(DPB)利用硝酸盐作为电子受体能够彻底吸磷,其吸磷速率约为好氧吸磷的59%;若以亚硝酸盐为电子受体,浓度较低时(10.6 mg/L)的吸磷速率与硝酸盐为电子受体时相当,但较高的亚硝酸盐浓度(22.6 mg/L)会抑制反硝化除磷过程;适当提高污泥浓度能加快缺氧吸磷速度,而过高的污泥浓度会降低污泥对氮、磷的比去除速率,故应将MLSS控制在合理的范围内。     

SBR中短程反硝化除磷菌的培养驯化研究

以周期运行培养方式在间隙反应器中驯化以亚硝酸盐作为电子受体的反硝化除磷菌,并比较了硝酸盐和亚硝酸盐作为电子受体时反硝化除磷的效果.结果表明,经厌氧/好氧+厌氧/缺氧(连续投加硝酸盐)+厌氧/缺氧/好氧(连续投加亚硝酸盐)方式成功筛选出能以亚硝酸盐作电子受体的反硝化除磷菌,该系统磷的去除率可达88.62％;在外加硝酸盐,...     

NO-2作为电子受体对反硝化吸磷影响动力学研究

在生物除磷系统中NO-2常被认为是反硝化吸收磷过程的抑制剂,而NO-2对反硝化吸磷抑制过程的抑制剂量的结果差别很大,缺乏动力学研究.本研究应用序批式反应器(SBR)在不同的NO-2浓度和pH梯度下进行了反硝化吸收磷试验,其接种活性污泥取自A2/O氧化沟中试反应器.SBR试验步骤为,取氧化沟好氧区活性污泥,先投加乙酸钠释放磷,然后投加NO-2吸收磷.大量试验发现NO-2和pH共同作用对反硝化吸磷产生了抑制.结果表明,[1]在恒定pH下,比反硝化速率和比吸磷速率与初始NO-2浓度均符合Andrews抑制动力学;[2]在6.5相似文献   

厌氧-缺氧下反硝化除磷对低碳污水的处理性能研究

采用厌氧-缺氧条件运行的序批式移动床生物膜反应器,考察了NO3--N进水浓度及其投加方式对低碳废水(COD=200mg/L)反硝化除磷的影响.经驯化后,反硝化聚磷菌(DPB)在总聚磷菌的份额从15.7%增长到71.3%,富集了DPB.NO3--N的浓度对处理有较大影响.在NO3--N为30mg/L(即C/N=6.7:1)时,COD、PO43--P和NO3--N的去除率分别为97.8%、82.0%和81.2%,实现低碳污水的高效处理.NO3--N较低或较高浓度(20mg/L和40mg/L)时,缺氧段吸磷不充分,PHB由厌氧开始时的2.2mg/g左右分别积累至5.1mg/g和3.5mg/g,影响下一周期磷的释放.1次投加、2次投加和连续流加NO3--N,除对缺氧初期的反硝化吸磷速率有影响外,对反硝化除磷的效率影响不明显.     

DPB污泥浓度对反硝化除磷的影响

为了进一步了解反硝化聚磷菌（DPB）污泥质量浓度（MLSS）对反硝化除磷过程的影响,进行一系列厌氧、缺氧模拟试验．研究考察DPB污泥的MLSS对厌氧释磷、缺氧反硝化吸磷的影响。结果表明：MLSS越高,释、吸磷速率及反硝化速率越高;MLSS对释、吸磷比速率和反硝化比速率的影响较小;厌氧总释磷量由污水中可利用COD的多少决定,DPB污泥的MLSS只影响到达释磷平衡的时间：污水中含氮量偏低引起反硝化吸磷段NO3^-不足时,DPB污泥厌氧释磷量高于反硝化吸磷量．MLSS越高经缺氧反硝化吸磷处理后水中含磷量越高。     

强化生物除磷体系中反硝化聚磷菌的选择与富集

采用SBR反应器 ,对以硝酸盐作为电子受体的反硝化聚磷菌的选择和富集作了研究 .结果表明 ,反硝化聚磷菌存在于传统的强化生物除磷体系之中 .经过 3个阶段的选择和富集 ,反硝化聚磷菌在聚磷菌中的比例从 15 %上升到 73% .稳定运行的强化反硝化生物除磷体系具有良好的强化生物除磷和反硝化脱氮性能 ,缺氧结束时体系中磷浓度小于 1mg L ,除磷和脱氮效率分别大于 94 %和 95 % .     

A~2O-BAF工艺反硝化聚磷效果的影响因素

为了提高系统的反硝化除磷脱氮效率,采用静态试验考察了厌氧反应时间和厌氧段COD对A2O-BAF工艺反硝化聚磷效果的影响,同时对缺氧阶段反硝化聚磷量与脱氮量之间的关系进行了探讨.试验结果发现,在试验范围内,随着厌氧反应时间和厌氧段COD的增加,厌氧释磷量均增加,反硝化聚磷量,净聚磷量和硝氮去除量亦都随之增加,但是反硝化聚磷量与释磷量的比值基本维持不变.在2组8个不同的试验条件下,缺氧段反硝化聚磷量和脱氮量之间均呈现出良好的线性关系,系数为1.007~1.053,R2为0.992~0.997,反映了A2O-BAF系统中污泥的固有特性.     

反硝化除磷污泥的厌氧释磷与缺氧吸磷特性研究

为研究厌氧释磷过程中的影响因素,以连续流A 2N双污泥中试污泥为样品,考察了碳源种类、碳源浓度、pH值以及温度对反硝化除磷污泥厌氧释磷的影响。结果表明:乙酸为碳源时释磷效果最佳,其次是葡萄糖,甲醇为碳源时释磷效果较差。MLSS为1 200 mg/L左右时,投加200 mg/L的COD即可保证充分释磷。pH值为6.3~8.8,对厌氧释磷效果影响不大,适当提高pH值有利于提高释磷速率。温度为20~30℃,释磷效果较好。另外,实验同时研究了反硝化除磷污泥分别利用不同电子受体(硝氮、氧气)的吸磷特性。以硝氮为电子受体的反硝化吸磷过程中,前15min的反硝化吸磷脱氮速率最高,吸磷速率与反硝化速率分别为11.5、10.4 mgN/gVSS·h;以氧气为电子受体的好氧吸磷过程中,前15 min的好氧吸磷速率最高,达到20.4 mgP/gVSS·h,大约为反硝化吸磷的2倍。     

利用亚硝酸盐的反硝化除磷菌及影响因素

反硝化聚磷菌(DPB)是一类能够在厌氧状态下释磷,缺氧存在硝酸盐(NO3-)或亚硝酸盐(NO2-)的情况下聚磷,并同时反硝化的聚磷菌。实验证明:传统A2/O工艺缺氧段污泥确实存在利用亚硝酸盐的反硝化聚磷菌,PO、PON和PONO各占聚磷菌的40.7%、38.5%,20.8%。最佳的进水C/N/P为16∶4∶1且COD<200mg/L;pH值为7～7.5。聚磷菌在ORP<-80mV开始吐磷,在ORP值在-150mV左右能较好地吐磷,投加亚硝盐使ORP>-80mV,开始反硝化聚磷。