Simultaneous nitrogen and phosphorus removal under low dissolved oxygen conditions

A full-scale test was operated by using low dissolved oxygen activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of CODCr, TN and TP varied in a range of 352.9 mg/L-1338.2 mg/L, 34.4 mg/L-96.3 mg/L, and 2.21 mg/L-24.0 mg/L, the average removal efficiencies were 94.9%, 86.7% and 93.0%, respectively. During the test period of two months, effluent meas of CODCr,, BOD5, NH3-N, TN and TP were below 50 mg/L, 25 mg/L, 10 mg/L and 1.0 mg/L respectively. The low dissolved oxygen activated sludge process has a simple flow sheet, fewer facilities and high N and P removal efficiency. It is very convenient to retrofit the conventional activated sludge process with the above process.

Novel strategy of nitrogen removal from domestic wastewater using pilot Orbal oxidation ditch

A pilot-scale Orbed oxidation ditch was operated for 17 months to optimize nitrogen removal from domestic wastewater of average COD to total nitrogen ratio of 2.7, with particular concern about the roles of dissolved oxygen （DO）, mixed liquor suspended solids （MLSS） and return activated sludge （RAS） recycle ratio. Remarkable simultaneous nitrification and denitrification （SND） was observed and mean total nitrogen （TN） removal efficiency up to 72.1% was steadily achieved, at DO concentration in the out, middle and inner channel of 0.1, 0.4 and 0.7 mg/L, respectively, with an average M LSS of 5.5 g/L and RAS recycle ratio of 150%. Although the out channel took the major role in TN removal, the role of middle channel should never be ignored. The denitrification potential could be fully developed under low DO, high MLSS with adequate RAS ratio. The sludge settleability was amazingly improved under low DO operation mode, and some explanations were tried. In addition, a scries of simplified batch tests were done to determine whether novel microorganisms could make substantial contribution to the performance of nitrogen removal. The results indicated that the SND observed in this Orbal oxidation ditch was more likely a physical phenomenon.

Effects of low temperature on sludge settleability and nutrients removal performance treating domestic wastewater

In order to investigate the effect of temperature on activated sludge systems,sludge settleability,nitrogen and phosphorus removal processes were investigated by changing temperature variation patterns using 4 sequencing batch reactors (SBR).The results showed that no matter temperature changes in the range of 15-22 ℃ (decrease or increase) gradually or sharply,it has little effect on nitrogen and phosphorus removal processes.But when temperature decreases to 12 ℃,biochemical reactions will be inhibitted obviously.At least 1 sludge retention time (SRT) is needed for nitrification adapt to new temperature envirionment,and more time is necessary for phosphorus removal process.When temperature increases from 12 ℃ to 22 ℃ sharply,nitrification process deteriorates seriously,but phosphorus removal process shows no change.In addition,sludge settleability deteriorates when temperature changes sharply (decrease or increase),but the reasons are different.Under temperature decrease condition,it is mainly caused by the increase of accumulated extracellular polymeric substances (EPS).Under temperature increase condition,the loosing sludge flocs' configuration is the main reason.It should be pointed out that the filamentous bacteria content during the entire experiment keeps almost constant,and the sludge settleability variations are the reflection of the change of sludge physicochemical characteristics.

Nitrogen removal for low-carbon wastewater in reversed A^2/O process by regulation technology

Full scale experimental study on nitrogen removal for low-carbon wastewater was conducted in reversed A2/O process in Jiguanshi waste water treatment plant in Chongqing,in order to aid the operation and maintenance of similar WWTP. When the proposed measures,such as using 0.1% (volume fraction of wastewater) landfill leachate,shortening HRT by 2/3 in the primary sedimentation tank and controlling DO at 0.5 mg/L in the 3rd section of aerobic zone,are applied,15% of the carbon source can be complemented,the favorable property of activated sludge is achieved,and the nitrogen removal effect is significantly improved. The effluent NH3-N is 2 mg/L and the removal rate is 90%. The effluent TN is 17 mg/L and the removal rate is 54%. The up-to-standard discharge of the effluent is achieved. And after the optimization,the unit electricity consumption also reaches 0.21 kW/h and saves 20%.

Enhanced nitrogen removal at low temperature with mixed anoxic/oxic process

Different hydraulic retention times(HRTs)were tested in a mixed anoxic/oxic(A/O)system at 5C and 10C to investigate the effects of HRT and carrier on nitrogen removal in wastewater at low temperatures.The results showed that the addition of the fillers improved the treatment effect of each index in the system.With an optimal HRT of 7.5 h at 5C,the removal efficiencies of NHþ4-N and total nitrogen(TN)reached 91.2%and 75.6%,respectively.With an HRT of 6 h at 10C,the removal efficiencies of NHþ4-N and TN were 96.7%and 82.9%,respectively.The results of high-throughput sequencing showed that the addition of the suspended carriers in the aerobic zone could improve the treatment efficiency of nitrogen at low temperatures.The microbial analysis indicated that the addition of the suspended carriers enhanced the enrichment of nitrogen removal bacteria.Nitrospira,Nitrotoga,and Nitrosomonas were found to be the bacteria responsible for nitrification,and their relative concentrations on the biofilm at 5C and 10C accounted for 98.11%,92.79%,and 69.98%of all biological samples,respectively.

NO reduction by CO over TiO_2-γ-Al_2O_3 supported In/Ag catalyst under lean burn conditions

TiO2/γ-Al2O3 supported In/Ag catalysts were prepared by impregnation method,and investigated for NO reduction with CO as the reducing agent under lean burn conditions.The microscopic structure and surface properties of the catalysts were studied by N2 adsorption-desorption,X-ray diffraction,transmission electron microscopy,X-ray photoelectron spectroscopy,ultraviolet-visible spectroscopy,H2 temperature-programmed reduction and Fourier transform infrared spectroscopy.TiO2/γ-Al2O3 supported In/Ag is a good catalyst for the reduction of NO to N2.It displayed high dispersion,large amounts of surface active components and high NO adsorption capacity,which gave good catalytic performance and stability for the reduction of NO with CO under lean burn conditions.The silver species stabilized and improved the dispersion of the indium species.The introduction of TiO2 into the γ-Al2O3 support promoted NO adsorption and improved the dispersion of the indium species and silver species.

Process Adaption and Modifications of a Nutrient Removing Wastewater Treatment Plant in Sri Lanka Operated at Low Loading Conditions

The Sri Lankan national water authority, that is The National Water Supply and Drainage Board (NWS&DB) has taken a new wastewater treatment plant into operation at Ja Ela, North of Colombo. The plant has been in operation since September 2011. In April 2012, it was concluded how a test of the aeration efficiency and a performance test should be carried out. The tests have been based on the actual loading of the plant and the analysis results from the daily process control. The evaluation of the aeration efficiency is not reported in this paper. The paper presents the overall performance of the water treatment part of the plant during start-up conditions, from fall 2011 through the first five months of 2012. The results from the operation are found in Table 1. An important circumstance at the plant is the current very low loading in comparison with the design load. This fact has resulted in an introduction of an intermittent mode of the aeration (nitrification) reactor. Based on operation figures, during more than a month (May 2012), it has been possible to give a realistic assessment of the overall performance. The most striking results are summarized as follows: 1) The intermittent operation has enabled an energy efficient operation of the plant. By the introduction of the intermittent aeration, the energy consumption has been reduced by around 75%, compared with the continuous operation mode;2) The plant performance during the intermittent operation has been improved with respect to virtually all important pollution variables. The most striking improvement is the discharge total P level, reflecting that a substantial enhanced biological phosphorus removal takes. The typical discharge levels found during May 2012, were compared with the earlier obtained values. It is important to underline that the loading on the plant has slightly increased during May as compared with the previous operation period.

DO对SBR短程硝化系统的短期和长期影响

采用实际的生活污水,在SBR反应器内分别考察了溶解氧(DO)对短程硝化效果及污泥种群结构的短期和长期影响.结果表明,通过采用实时控制曝气时间,高ρDO(ρ(DO)=(3±0.5)mg/L)与低ρDO(ρ(DO)=(0.5±0.1)mg/L)条件下SBR系统的亚硝酸盐积累率均能达到90%以上,而低ρDO相对于高ρDO更利于提高系统的同步硝化反硝化(SND)效果,两者的平均同步硝化反硝化率(SND率)分别为45.5%和9.5%,低ρDO下最高SND率达86%.FISH的检测结果表明,实时控制模式下反应器内亚硝酸氧化菌(NOB)逐渐被淘洗,而氨氧化细菌(AOB)变为优势硝化菌群.在高ρDO运行末期,稳定的短程污泥中AOB和NOB的相对数量分别为8%～10%和不足0.5%;在低ρDO运行末期,AOB数量出现了微弱上升,增至10%～12%,而NOB进一步被淘汰,基本检测不出.可见,采用好氧曝气时间实时控制,能对短程硝化系统内污泥种群起到优化作用,且在高、低ρDO下均能实现稳定的短程硝化效果,而低ρDO更有利于系统内亚硝酸氧化菌(NOB)的淘洗、短程硝化率的提高以及系统SND效果的加强.

低DO下曝气方式对分段进水脱氮工艺的影响

采用分段进水生物脱氮工艺处理小区生活污水，考察了在低DO条件下，不同曝气方式对硝化率及污泥沉降性能的影响。结果表明，在曝气量为0．27m^3／h、MLSS平均为2700mg／L左右、好氧区的DO为0．26～2．5mg／L的条件下，当进水氨氮为44～55mg／L时，对氨氮的去除率保持在95％以上，对COD的去除率〉90％；当控制好氧区第1、2格室的DO分别为0．5～0．7和1．0～1．2mg／L时，系统的硝化率维持在90％以上，出水中的氨氮〈2mg／L；在恒定曝气量下，向进水中投加有机碳源，当水质改变较快时，容易引起丝状菌污泥膨胀，但通过恒DO曝气控制，可使污泥的沉降性能得到改善。

分段进水A/O工艺在低DO下处理生活污水研究

采用小试规模的三段进水A／O生物脱氮工艺，在低DO下处理低COD／TN值（2～3）的小区生活污水，考察了对COD、氨氮和TN的去除效果以及污泥的沉降性能。结果表明，系统对COD的去除效果稳定，平均去除率为87．9％。当系统的水力停留时间（HRT）为10h时，对氨氮的去除率〉98％；将HRT缩短至8h后，对氨氮的去除率仍大于95％，出水氨氮〈5mg／L。由于系统内形成了稳定的同步硝化反硝化（SND），使得在进水COD／TN值仅为2～3的条件下，系统对TN的去除率仍可达80％以上，平均去除率为72．4％。此外，在90d的运行中污泥的沉降性能较好，镜检未发现丝状菌。

低DO含量MBR工艺的脱氮及运行特性研究

采用浸没式MBR工艺,以城市污水为研究对象,研究了在低DO含量条件下对污染物的去除效果。结果表明,在DO的质量浓度分别为0.8～1.2、0.2～0.5、0.5～0.8mg·L-13个工况条件下,系统对COD的去除效果没有明显差异,但DO对氨氮和TN的去除率有显著的影响。DO的质量浓度在0.8～1.2mg·L-1时,氨氮去除率能达到90%以上,TN去除率约为70%;DO的质量浓度降低到0.2～0.5mg·L-1时,氨氮和TN的去除率约为50%;当DO为0.5～0.8mg·L-1时,TN去除率达到85%以上。在不同工况运行条件下,研究了DO对活性污泥SVI、丝状菌膨胀的影响,通过对膜过滤压降的测定,证实了丝状菌膨胀对膜污染有较大的影响。

Advanced landfill leachate treatment using a two-stage UASB-SBR system at low temperature

A two-stage upflow anaerobic sludge blanket （UASB） and sequencing batch reactor （SBR） system was introduced to treat landfill leachate for advanced removal of COD and nitrogen at low temperature. In order to improve the total nitrogen （TN） removal efficiency and to reduce the COD requirement for denitrification, the raw leachate with recycled SBR nitrification supematant was pumped into the first-stage UASB （UASB1） to achieve simultaneous denitrification and methanogenesis. The results showed that UASB1 played an important role in COD removal and UASB2 and SBR further enhanced the nutrient removal efficiency. When the organic loading rates of UASB1, UASB2 and SBR were 11.95, 1.63 and 1.29 kg COD/（m^3.day）, respectively, the total COD removal efficiency of the whole system reached 96.7%. The SBR acted as the real undertaker for NH4^＋-N removal due to aerobic nitrification. The system obtained about 99.7% of NH4^＋-N removal efficiency at relatively low temperature （14.9-10.9℃）. More than 98.3% TN was removed through complete denitrification in UASB 1 and SBR. In addition, temperature had a significant effect on the rates of nitrification and denitrification rather than the removal of TN and NH4^＋-N once the complete nitrification and denitrification were achieved.

Advanced nitrogen and phosphorus removal in A^(2)O-BAF system treating low carbon-to-nitrogen ratio domestic wastewater

A laboratory-scale anaerobic-anoxic-aerobic process(A^(2)O)with a small aerobic zone and a bigger anoxic zone and biologic aerated filter(A^(2)O-BAF)system was operated to treat low carbon-to-nitrogen ratio domestic wastewater.The A^(2)O process was employed mainly for organic matter and phosphorus removal,and for denitrification.The BAF was only used for nitrification which coupled with a settling tank Compared with a conventional A^(2)O process,the suspended activated sludge in this A^(2)OBAF process contained small quantities of nitrifier,but nitrification overwhelmingly conducted in BAF.So the system successfully avoided the contradiction in sludge retention time(SRT)between nitrifying bacteria and phosphorus accumulating organisms(PAOs).Denitrifying phosphorus accumulating organisms(DPAOs)played an important role in removing up to 91%of phosphorus along with nitrogen,which indicated that the suspended activated sludge process presented a good denitrifying phosphorus removal performance.The average removal efficiency of chemical oxygen demand(COD),total nitrogen(TN),total phosphorus(TP),and NH_(4)^(+)-N were 85.56%,92.07%,81.24%and 98.7%respectively.The effluent quality consistently satisfied the national first level A effluent discharge standard of China.The average sludge volume index(SVI)was 85.4 mL·g^(-1)additionally,the volume ratio of anaerobic,anoxic and aerobic zone in A^(2)O process was also investigated,and the results demonstrated that the optimum value was 1:6:2.

低温下DO对SMBR脱氮效果的影响研究

利用一体式膜生物反应器(SMBR),考察低温下DO对SMBR系统脱氮效果的影响。取DO为0.5mg/L和1.5mg/L两个条件作对比。结果表明:硝化过程受低温影响较大,是影响TN去除的限制因素;反硝化过程受低温影响稍小。在HRT为2h的短水力停留时间,F/M为0.68～0.77kgCOD/(kgMLSS.d)的高有机物负荷,DO为0.5mg/L的低溶解氧以及低温条件下,SMBR实现了较高的脱氮效率。具有省时高效、占地面积小、污染物去除率高的技术优势。

Disposal of Rural Domestic Sewage in Ecological Wetland System

Pollution brought by rural domestic sewage has become increasingly serious, so it is imperative to fi gure out economical and efficient solutions. On the basis of comparison between rural domestic sewage treatment means in China and abroad, actual conditions of countryside, current situation and features of domestic sewage, this paper adopted the compound ecological wetland system consisting of anaerobic and aerobic units, ecological floating bed and artifi cial wetland, so as to remove nitrogen and phosphorus efficiently, achieve the goal of low operation and construction cost and less land use.

植物净化低C/N污水时根系DOC释放与氮磷去除规律研究

由于缺乏碳源,低C/N比废水中氮磷无法被有效去除。因此,本研究将空心菜作为功能性植物,以提高C/N比来提高氮磷去除效果。在3种不同的C/N比(3:1、3.5:1、4:1)和2种NH_(4)~+/NO_(3)~-比 (2:1和1:2)下,研究根系DOC释放情况与氮磷去除规律。结果表明,根系DOC浓度、氮磷净化效果随C/N比增大而增大,NH_(4)~+/NO_(3)~-为2:1大于NH_(4)~+/NO_(3)~-为1:2;在C/N比为4:1且NH_(4)~+/NO_(3)~-比为2:1时的根系DOC浓度及氮磷去除最大,第8 d,根系DOC浓度为11.79 mg/L,氮磷去除率分别为74.1%,88.3%,出水浓度为5.18 mg/L、0.009 mg/L。根系DOC与氮磷净化效果呈显著正相关,根系DOC分泌浓度越大,氮磷去除效果越好。研究表明,空心菜能有效净化低C/N比污水,使出水水质满足城市污水再生利用-城市杂用水水质标准(GB/T 18920-2002)。

低氨氮质量浓度废水DPR-SNAD脱氮除磷效能研究

针对低氨氮废水单级自养脱氮系统副产物硝氮残留,有机物耐受能力差,以及缺乏除磷功能等问题,提出反硝化除磷(Denitrifying Phosphorus Removal,DPR)-单级自养脱氮(Simultaneous Partial Nitrification,Anaerobic Ammonium Oxidation and Denitrification,SNAD)组合处理技术,重点考察氨氮负荷对单级自养脱氮工艺(Single-stage Nitrogen Removal Using Anammox And Partial Nitritation,SNAP)系统、泥龄对DPR系统构建的影响,以及低氨氮废水DPR-SNAD组合处理系统的脱氮除磷效能与微生物种群。研究结果显示:采用氨氮质量浓度梯度递减方式,氨氮负荷为0.20 kg N/(m^(3)·d)的低氨氮质量浓度的SNAP系统构建时间为63 d,较负荷为0.05 kg N/(m^(3)·d)的系统缩短了37 d。泥龄对构建的DPR系统效能影响显著,泥龄为35 d的系统除磷脱氮效能较高,PO_(4)^(3-)-P、NO_(3)^(-)-N、COD去除率分别为86.25%、98.00%、92.00%,系统释磷、吸磷、反硝化脱氮速率分别达4.60 mg/(L·h)、4.13 mg/(L·h)、5.53 mg/(L·h)。DPR-SNAD组合处理系统的氨氮(NH_(4)^(+)-N)、总氮(Total Nitrogen,TN)、总磷(Total Phosphorus,TP)、化学需氧量(Chemical Oxygen Demand,COD)去除率分别为100%、98.64%、86.00%、93.30%。TN、TP去除率较对照组SNAP分别提高了19.20百分点和86.00百分点。16S rRNA高通量测序结果显示,组合系统脱氮除磷功能菌属主要有Rhodobacter、Candidatus_Brocadia、Nitrosomonas、Gemmobacter,SNAD系统中厌氧氨氧化菌(Anaerobic Ammonia Oxidation,AnAOB)相对丰度显著高于对照组SNAP系统,DPR促进SNAD提高了系统脱氮效能。

基于短周期调控的SPNPR-A系统脱氮除磷研究

建立了短周期循环调控低浓度亚硝酸盐(NO_(2)^(-)-N)的短程硝化同步除磷耦合厌氧氨氧化(SPNPR-A)系统,SPNPR系统以厌氧/好氧模式运行,通过短周期运行时长调控系统内NO_(2)^(-)-N浓度用以淘洗亚硝酸盐氧化菌(NOB),同步富集氨氧化菌(AOB)和聚磷菌(PAOs),最终实现同步脱氮除磷功能.结果表明:SPNPR系统内NO_(2)^(-)-N浓度维持在10mg/L左右时可有效抑制NOB活性.70d后SPNPR系统2个短周期的亚硝酸盐积累率(NAR)分别达到90.40%和88.93%,SPNPR-A系统总氮(TN)、总磷(TP)、有机物(COD)的平均去除率分别为87.45%、84.30%和94.26%.第60d时,比氨氧化速率(SAOR)和AOB的比氧利用速率(SOUR_(AOB))分别为8.47mgN/(gMLVSS·h)和12.71mgO_(2)/(gMLVSS·h);比硝态氮生成速率(SNPR)和NOB的比氧利用速率(SOUR_(NOB))分别为0.82mgN/(gMLVSS·h)和0.41mgO_(2)/(gMLVSS·h).高通量测序结果表明,第70d时SPNPR系统属水平上的AOB功能菌属Nitrosomonas(6.46%)和Nitrosospira(0.64%),丰度远高于NOB功能菌属Nitrospira(0.14%)和Nitrobacter(0.01%),同时聚磷菌属Candidatus_Accumulibacter(1.61%)和Tetrasphaera(0.89%)得到富集,使得SPNPR-A系统具备同步脱氮除磷性能.

9个裸燕麦品种苗期耐低氮性评价

为探究裸燕麦在低氮条件下的生长和生理响应情况,评价不同品种的耐低氮能力,本研究以9个裸燕麦品种为试验材料,设置全氮(4 mmol/L,CK)和1/10 N(0.1 mmol/L,低氮)两个氮浓度,在苗期处理21 d后对裸燕麦的形态指标和生理指标进行测定。结果表明:在低氮条件下,相比对照组:(1)裸燕麦的根长、生物量均有不同程度下降,其中WDY5的地上部干重降幅最大,同时裸燕麦的株高除ZY8呈上升趋势外其他均呈下降趋势;(2)裸燕麦的硝态氮、硝酸还原酶、谷氨酰胺合成酶、谷氨酸脱氢酶活性、渗透调节物质的含量均呈下降趋势,谷氨酸合成酶活性、超氧阴离子、过氧化氢、丙二醛含量指标呈上升趋势,其中QY3的丙二醛含量升幅最小;(3)主成分分析将21个测定指标转换为5个主成分,累计方差贡献率为91.76%;并进行聚类分析,结果将9个裸燕麦品种划分为3个类群:耐低氮品种3个、中等耐低氮品种5个、低氮敏感型品种1个;计算耐低氮Z值对其耐低氮性进行综合评价,筛选出耐低氮品种为QY3,氮敏感品种为WDY5。

低温对含盐食品污水深度处理性能与微生物群落的影响

固体碳源被广泛应用于污水深度处理,但是低温条件下对含盐食品污水的处理性能还缺乏评估,微生物特性也需要揭示。以聚丁二酸丁二醇酯为固体碳源,考察了不同温度条件下的脱氮性能、微生物群落结构以及基因富集特征。结果表明:常温(25~28℃)条件下的固体碳源反应器出水可以满足《污水综合排放标准》一级标准。低温(5~9℃)对脱氮性能抑制显著,NH_(4)^(+)-N、NO_(3)^(-)-N去除率仅为30.17%、73.51%,并且运行初期存在出水有机物超标的风险。固体碳源体系中unclassified_Comamonadaceae、Acidovorax分别是主要的硝化、反硝化菌属,但容易受低温影响而丰度降低。此外,温度降低还会导致硝化基因(amoA、amoB、amoC)和反硝化基因(narG、narH、narI)丰度降低。