好氧颗粒污泥处理垃圾渗滤液的效能

利用SBR反应器,以曝气量作为主要控制条件、以垃圾渗滤液作为培养基质来培养好氧颗粒污泥,研究好氧颗粒污泥的培养以及对垃圾渗滤液的处理效果.结果表明:在0.08、0.003 m3/h两种曝气量下均成功培养出好氧颗粒污泥,但其形态存在较大差别,高曝气量下形成的颗粒污泥结构紧密、粒径小、沟壑和孔道较多,而低曝气量下形成的颗粒污泥结构松散、沟壑和孔道较少,但粒径较大.当进水COD为900～1 200 mg/L时,低曝气量系统对COD的去除率可达93%左右,高曝气量系统的为80%;在不同的曝气量下,对TP的去除率均在60%左右;曝气量对硝化的影响较大,高曝气量下好氧颗粒污泥对氨氮的去除率能达到90%,高于低曝气量下对氨氮的去除率;与低曝气量下形成的颗粒污泥相比,高曝气量下形成的好氧颗粒污泥能更好地适应垃圾渗滤液中的高浓度游离氨.     

间歇曝气脱氮系统的影响因素研究

通过观察间歇曝气生物脱氮系统在不同水温、C/N值下的脱氮效率以及好氧/缺氧一周期内的硝化和反硝化过程,分析了温度和缺氧期C/N值对硝化和反硝化速度的影响,探讨了冬季所需外加碳源量。试验结果表明,秋、冬季提高缺氧期C/N值是保障间歇曝气脱氮系统运行效率的有效措施;在TN负荷为0.034kg/(kgMLVSS·d),水温为15℃时最适C/N值为7,10℃时最适C/N值为9。为了降低冬季运行费用,有必要寻找廉价的外碳源。     

短程硝化反硝化AOOA工艺处理老龄垃圾渗滤液

采用厌氧/好氧/好氧/厌氧(AOOA)中试系统处理老龄垃圾渗滤液,通过控制DO在0. 1～0. 5 mg/L等条件成功实现了短程硝化反硝化。在低溶解氧和碱度充足的条件下,O1池的NO-2-N积累率稳定在90%以上,系统对NH+4-N和TN的去除率分别高于95%和66. 5%,有效解决了老龄垃圾渗滤液的脱氮难题。在控制溶解氧为0. 3～0. 5 mg/L的条件下,O1池进行亚硝化的限制条件是实际水力停留时间(AHRT),宜控制在13. 9 h以上。在正常运行阶段,A1池中的优势菌种为反硝化菌,而O1池的优势菌为AOB。此外,O1/O2池实现了NO-2-N的积累,并在一定程度上形成了同步亚硝化反硝化(SND)体系。     

曝气方式对氧化沟工艺脱氮效果的影响

采用混合反应器模拟氧化沟运行的方式,探讨曝气方式对其脱氮效果的影响.结果表明:分点曝气的溶氧效率高,好氧区长,而分段曝气的氧有效利用(用于硝化)率高,两者的硝化率相当,但采用分点曝气时好氧区的整体DO水平偏低,其硝化菌活性不如分段曝气的,两者的硝化菌活性分别为4.55和4.89 mgNH4 - N/(gMLVSS·h).两种方式下对有机物的去除效果相当,去除率分别为91.01％和92.19％,出水COD皆在30 mg/L以下,但在分段曝气中有机物主要用于反硝化脱氮,反硝化效率高,而在分点曝气方式下只有一小部分有机物用于反硝化,脱氮率低,出水硝态氮浓度高.分点曝气的污泥沉降性能较好,但运行稳定性不如分段曝气系统,好氧区与缺氧区的比例受进水水质的影响较大,从而影响处理效果.     

填埋场间歇微氧渗滤液回灌技术工程研究

以规模为100 t/d的某生活垃圾填埋场渗滤液处理工程为依托,开发了有效的渗滤液回灌结构,最大水力负荷达0.45 m3/(m2·d).设计了单层间歇曝气、双层间歇曝气、连续曝气3种微氧运行工况,分析了不同水力负荷、曝气负荷对渗滤液中COD、NH3-N去除效果的影响.结果表明:最佳间歇微氧渗滤液回灌运营工况是单层间歇曝气,其中水力负荷为0.45 m3/(m2·d)、曝气负荷为6.75 m3风量/(m3垃圾·d).回灌处理出水水质稳定,受进水浓度影响较小,出水COD＜1 500 mg/L、NH3-N＜900 mg/L,最低出水NH3-N达400 mg/L.该负荷条件下加大曝气量,如双层间歇曝气、连续曝气对COD的去除效果影响不大,对NH3-N的去除效果略有提高.     

SBR反应器短程同步硝化反硝化处理垃圾渗滤液

采用序批式活性污泥法(SBR)处理垃圾渗滤液,在控制系统温度为(28±1)℃、进水pH值为7.9~8.2、MLSS为4 000~4 500 mg/L,并保持进水COD为900~1 000 mg/L、NH+4-N为480~500 mg/L的条件下,考察DO对短程硝化反硝化的影响。结果表明,在80~120 L/h的曝气量下能快速实现稳定的短程同步硝化反硝化,对NH+4-N的平均去除率可达92.5%,NO-2-N的平均积累率为89.3%;系统的最佳曝气量为120 L/h,此时对氨氮的去除率为96.9%,亚硝酸盐积累率为97.2%,好氧段对总氮的去除率为74.7%。     

曝气模式对序批式生物膜法脱氮效能的影响

研究了不同的曝气模式对序批式生物膜法脱氮效能的影响.结果表明,与连续低氧(DO=0.9-1.1 mg/L)曝气模式相比,连续好氧(DO=2.5-3.2 mg/L)曝气模式可加速挂膜过程;在序批式运行期间,连续低氧模式较好氧/低氧模式的脱氮效率更高;以脱氮效能为衡量标准,采用连续低氧曝气模式进行挂膜、运行操作,更能促进生物膜内好氧、缺氧分区结构的稳定,更易于实现同时硝化反硝化或短程反硝化过程,提高脱氮效率.     

厌氧同时反硝化产甲烷工艺的应用及进展

厌氧同时反硝化产甲烷工艺能够充分利用废水中的有机碳源,在实现生物脱氮的同时产生甲烷,其关键是如何减小或消除硝态氮（NO^- -N）对产甲烷茵的抑制作用。目前,解决该问题的主要手段有培养同时反硝化产甲烷颗粒污泥和生物膜等方法。研究表明,厌氧同时反硝化产甲烷反应器串联好氧硝化反应器（SDMR—ANR）系统,适于处理早期的垃圾渗滤液、屠宰废水等含高浓度有机物和高NH4＋ -N的废水,其中进水COD／N03- -N和好氧反应器出水回流比是影响其运行效果的关键因素。此外,还介绍了厌氧同时反硝化产甲烷工艺的微生物种群结构及进一步的功能扩展。     

好氧反硝化在短程硝化反硝化工艺中的作用研究

采用SBR反应器处理垃圾渗滤液，研究了短程硝化反硝化过程中好氧反硝化的作用。结果表明，SBR反应器的亚硝化效果良好，氨氮几乎完全被氧化为NO2^- -N；该系统的活性污泥中同时存在能还原NO3^- -N和NO2^- -N的好氧反硝化菌，还原NO3^- -N的好氧反硝化菌和氨氧化菌的数量及其总活性高于NO2^- -N氧化菌，这是SBR反应器能够长期维持亚硝化状态的重要原因；有机物浓度越高则好氧反硝化速率越快，此时氨氮均被氧化为NO2^- -N，当有机物浓度达到某临界值时，好氧反硝化速率几乎保持不变；溶解氧浓度越低则好氧反硝化速率越快，释放出的OH^-会导致pH值升高。好氧反硝化对于维持和促进SBR反应器的短程硝化反硝化具有重要的作用。     

改进的MBR对渗滤液的脱氮效果及机理分析

垃圾渗滤液因组成复杂、浓度高而较难处理。对膜生物反应器(MBR)进行改进,并开展了处理渗滤液的研究。该MBR对渗滤液中TN和NH3-N的平均去除率分别达72.98%和90.1%,由试验数据和现象推断同步硝化反硝化是TN和NH3-N得以去除的最主要原因。同步硝化反硝化的发生在于3个方面:①膜的截留作用使世代时间较长的硝化菌和反硝化菌得以富集;②在时间和空间上反复经历缺氧、好氧的环境;③有利的操作条件,如维持MLSS为8 500 mg/L左右、温度为22～30℃、pH值为7.0～7.5、升流区的DO为2～2.5 mg/L等。     

无外加碳源SBBR脱氮工艺及其控制方法研究

为提高脱氮效果并实现利用内碳源进行反硝化,开展了SBBR（以好氧-缺氧方式运行）处理生活污水的脱氮研究.在好氧阶段,SBBR中的生物膜能创造缺氧微环境并吸收、储存碳,实现了同步硝化反硝化,降低了硝态氮的浓度;在缺氧阶段,可利用内碳源实现剩余硝态氮的反硝化.溶解氧浓度的大小对好氧时间、好氧剩余硝态氮浓度和缺氧反应时间有较大影响,因而可以利用在线检测的DO作为曝气量控制参数.DO、pH和ORP值的变化具有规律性,反映了生物脱氮过程中耗氧和供氧、产酸和产碱、氧化和还原过程的变化.为准确判断好氧和缺氧反应过程的终点,并减少控制的滞后时间,建议以pH值的＂氨谷＂和ORP的＂硝酸盐膝＂作为主控制特征点分别指示硝化和反硝化的终点,而以ORP的＂氨肘＂和pH值的＂硝酸盐峰＂作为参考或辅助控制特征点.     

In situ nitrogen management in controlled bioreactor landfills

The characteristics of leachate from landfills vary according to site-specific conditions. Leachates from “old” landfills are often rich in ammonia nitrogen due to the hydrolysis and fermentation of the nitrogenous fractions of biodegradable substrates, with decreases in concentration mainly attributable to leachate washout. At landfills where leachate containment, collection and recirculation is practiced to accelerate decomposition of readily biodegradable organic constituents, leachate ammonia nitrogen concentrations may accumulate to higher levels than during conventional single pass leaching, thereby creating an ultimate leachate discharge challenge. Landfill leachate treatment options include complex and often costly sequences of external physical–chemical and biological processes for removal of high-strength organics and inorganics, including nitrogen. Therefore, this paper focuses on investigations with bioreactor landfill simulations to demonstrate the potential for in situ nitrogen removal in dedicated nitrification/denitrification zones. Using leachate recirculation, associated system modifications provided separate aerobic and anoxic zones for ammonia nitrogen transformations to nitrate and nitrogen gas, respectively. Results from the three simulated optional stages of methanogenesis, nitrification and denitrification indicated that nitrogen conversion and removal was dependent on the operational stage. Both separate and combined reactor operation with internal leachate recycle provided 95% nitrogen conversion. In contrast, combined reactor operation with single pass leaching provided a conversion efficiency per cycle ranging between 30–52% for nitrification and 16–25% for denitrification, thereby indicating the efficacy of using the landfill itself for attenuation of leachate ammonia nitrogen concentrations to levels acceptable for ultimate discharge.     

Baffled membrane bioreactor (BMBR) for efficient nutrient removal from municipal wastewater

Submerged membrane bioreactors (MBRs) are now widely used for various types of wastewater treatment. One drawback of submerged MBRs is the difficulty in removing nitrogen because intensive aeration is usually carried out in the tank and the MBRs must therefore be operated under aerobic conditions. In this study, the feasibility of treating municipal wastewater by a baffled membrane bioreactor (BMBR), particularly in terms of nitrogen removal, was examined. Simultaneous nitrification/denitrification in a single and small reaction tank was possible by inserting baffles into a normal submerged MBR as long as wastewater was fed in the appropriate way. To examine the applicability of the BMBR, pilot-scale experiments were carried out using real municipal wastewater. Although neither external carbon addition nor mixed liquor circulation was carried out in the operation of the BMBR, average removal rates of total organic carbon (TOC), total phosphorus (T-P) and total nitrogen (T-N) reached 85%, 97% and 77%, respectively, with the hydraulic retention time (HRT) of 4.7h. Permeability of the membrane could be maintained at a high level throughout the operation. It was found that denitrification was the limiting step in removal of nitrogen in the BMBR in this study. Various types of monitoring carried out in the BMBR also demonstrated the possibility of further improvements in its performance.     

Microbial fuel cells for simultaneous carbon and nitrogen removal

The recent demonstration of cathodic nitrate reduction in a microbial fuel cell (MFC) creates opportunities for a new technology for nitrogen removal from wastewater. A novel process configuration that achieves both carbon and nitrogen removal using MFC is designed and demonstrated. The process involves feeding the ammonium-containing effluent from the carbon-utilising anode to an external biofilm-based aerobic reactor for nitrification, and then feeding the nitrified liquor to the MFC cathode for nitrate reduction. Removal rates up to 2 kg COD m(-3)NCC d(-1) (chemical oxygen demand: COD, net cathodic compartment: NCC) and 0.41 kg NO(3)(-)-Nm(-3)NCC d(-1) were continuously achieved in the anodic and cathodic compartment, respectively, while the MFC was producing a maximum power output of 34.6+/-1.1 Wm(-3)NCC and a maximum current of 133.3+/-1.0 Am(-3)NCC. In comparison to conventional activated sludge systems, this MFC-based process achieves nitrogen removal with a decreased carbon requirement. A COD/N ratio of approximately 4.5 g COD g(-1) N was achieved, compared to the conventionally required ratio of above 7. We have demonstrated that also nitrite can be used as cathodic electron acceptor. Hence, upon creating a loop concept based on nitrite, a further reduction of the COD/N ratio would be possible. The process is also more energy effective not only due to the energy production coupled with denitrification, but also because of the reduced aeration costs due to minimised aerobic consumption of organic carbon.     

Application of response surface methodology for simultaneous carbon and nitrogen (SND) removal from dairy wastewater in batch systems

The application of batch systems to the direct treatment of dairy wastewater was investigated. Batch experiments were conducted to study the organics removal and simultaneous nitrification and denitrification (SND) process. The experiment was conducted by varying four independent parameters (mixed liquor suspended solids, chemical oxygen demand [COD]/N ratio, aeration time and cycling time), using a central composite design under response surface methodology. The process responses of five dependent parameters (COD, Total kjehldahl nitrogen (TKN), NO₃ ^?, effluent NO₃ ^? and effluent total nitrogen) were studied, and in each case, the percentage removal in batch runs was determined with each process displayed in contour plots. Finally, after optimizing the process conditions, the best treatment of dairy wastewater under optimized conditions was established and the responses were shown. This study shows that microbial granules cultivated under the alternating aerobic/anaerobic conditions in batch systems could efficiently remove organic carbon and convert all the ammonium to nitrogen gas.     

一体式膜生物反应器同步硝化反硝化性能研究

构建了气升循环一体式膜生物反应器,将其用于处理城市污水,并对其同步硝化反硝化(SND)的形成过程进行了研究。结果表明,反应器内存在明显的好氧区和厌氧区,并利用曝气推动力实现硝化液在各区间的循环,能够形成良好的硝化和反硝化过程;在反应器结构一定的条件下,曝气强度成为制约溶解氧大小和分布的最主要因素,过大或过小的曝气强度对TN的去除都是不利的,当曝气强度控制在50~70 m3/(m2.h)时,系统对TN的去除效果最好,去除率为48.1%~54.0%,实现了较好的同步硝化反硝化效果。     

Biological nitrogen removal from municipal landfill leachate: low-cost nitrification in biofilters and laboratory scale in-situ denitrification

The slow leaching of nitrogen from solid waste in landfills, resulting in high concentrations of ammonia in the landfill leachate, may last for several decades. The removal of nitrogen from leachate is desirable as nitrogen can trigger eutrophication in lakes and rivers. In the present study, a low-cost nitrification-denitrification process was developed to reduce nitrogen load especially in leachates from small landfills. Nitrification was studied in laboratory and on-site pilot aerobic biofilters with waste materials as filter media (crushed brick in upflow filters and bulking agent of compost in a downflow filter) while denitrification was studied in a laboratory anoxic/anaerobic column filled with landfill waste. In the laboratory nitrification filters, start-up of nitrification took less than 3 weeks and over 90% nitrification of leachate (NH4-N between 60 and 170mg N l(-1), COD between 230 and 1,300 mg l(-1)) was obtained with loading rates between 100 and 130 mgNH4-N l(-1) d at 25 degrees C. In an on-site pilot study a level of nitrification of leachate (NH4-N between 160 and 270 mg N l(-1), COD between 1,300 and 1,600 mg l(-1)) above 90% was achieved in a crushed brick biofilter with a loading rate of 50mg NH4-N l(-1) d even at temperatures as low as 5-10 degrees C. Ammonium concentrations in all biofilter effluents were usually below the detection limit. In the denitrification column. denitrification started within 2 weeks and total oxidised nitrogen in nitrified leachate (TON between 50 and 150mg N l(-1)) usually declined below the detection limit at 25 degrees C, whereas some ammonium, probably originating from the landfill waste used in the column, was detected in the effluent. No adverse effect was observed on the methanation of waste in the denitrification column with a loading rate of 3.8 g TON-N/t-TS(waste) d. In conclusion, nitrification in a low-cost biofilter followed by denitrification in a landfill body appears applicable for the removal of nitrogen in landfill leachate in colder climates.     

Application of the 15N technique to determine the contributions of nitrification and denitrification to the flux of nitrous oxide from aerated pig slurry.

In order to elucidate and quantify nitrogen transformations occurring during aerobic treatment of pig slurry, two laboratory experiments were carried out with contrasting levels of aeration, high level (experiment 1) and low level (experiment 2) of aeration. During these experiments, after reaching steady-state conditions, a single pulse of NO3(-)-15N tracer was added directly to the reactor. When nitrification conditions were prevailing (experiment 1), no transformation of added NO3(-)-15N occurred (98.7% 15N-recovery as nitrates in the liquid slurry). Moreover, the unlabelled nitrous oxide (N2O) measured (7.4% of the total nitrogen content of the raw slurry) strongly demonstrated that the source of N2O emitted was nitrification. During simultaneous nitrification and denitrification conditions (experiment 2), the added NO3(-)-15N was found in gaseous nitrogen forms (N2O-15N: 27%; N2-15N: 18%) and in the liquid (TN-15N: 54%). From this result, it was evident that N2O was mainly emitted by denitrification process. Using the decrease of the isotopic excess of the NO3(-)-15N we calculated that 92% of NO2(-)-N was directly denitrified (as gaseous forms) without any previous oxidation to nitrate.     

The effect of decreased ambient temperature on the biological nitrification and denitrification of a high ammonia landfill leachate

This research investigated the nitrogen removal capabilities of a pre- and post-denitrification process, when treating sanitary landfill leachate containing an ammonia concentration of over 2200 mg N/L, at operating temperatures down to 10 degrees C. The treatment system employed is generally known as a 4-Stage Bardenpho process. Two parallel systems were operated throughout the study; each system had an aerobic solids retention time of 20 days and an external recycle ratio (return activated sludge) of about 3:1. During the entire experimental period, one system used an internal recycle ratio of about 4:1, while the other system used one of 3:1. Methanol was used as supplementary carbon source for denitrification. When operating temperature was decreased from 20 to 17 degrees C, an approximate 15% decrease in denitrification was immediately experienced within both systems, with no noticeable affect on nitrification. This was an unexpected result. Subsequently, the temperature was further decreased to 14 degrees C, and finally to 10 degrees C. With the temperature at 14 degrees C, aerobic wasting was also stopped and methanol loading was progressively decreased to match actual denitrification requirements. At 10 degrees C, both systems suffered major nitrification and denitrification inhibition. Changes in operating parameters, such as a decrease in influent ammonia and methanol loading, as well as an increase in ambient temperatures, from 10 to 15 degrees C, did not significantly improve overall system performance, within a reasonable time frame. Both denitrification and nitrification problems were mainly attributed to decreased ambient temperature, although other possible factors were noted; at project completion, about 50% of the incoming ammonia was being removed across the system.