2001 Effect of operating conditions on solid velocity in the spout, annulus and fountain of spouted

Power MOSFET（金属氧化物半导体场效应晶体管）是一种常用的功率器件，广泛应用于电源电子设备中。

它具有低开关损耗、高效率和快速开关速度的特点，因此被广泛应用于交流至直流转换器、逆变器、电源放大器等领域。

而功率MOSFET的工作频率则是影响其性能的重要参数之一。

1. 功率MOSFET的工作频率是指MOSFET在工作状态下正常工作的频率范围。

一般来说，功率MOSFET的工作频率要高于普通MOSFET，因为它用于处理更高功率的电信号，需要更快的响应速度和开关速度。

2. 工作频率的提高可以提高功率MOSFET的工作效率和开关速度，从而提高整个电源系统的性能。

在选择功率MOSFET时，工作频率是需要进行考虑的重要因素之一。

3. 功率MOSFET的工作频率受到多种因素的影响，包括MOSFET的内部结构、材料特性和电路设计等。

其中，MOSFET的结构参数和材料特性是决定工作频率的关键因素。

4. 功率MOSFET的工作频率还受到外部工作条件的影响，如输入电压、电流负载等。

在实际应用中，需要根据具体的工作条件来选择合适的功率MOSFET，以确保其在正常工作条件下可以达到预期的性能。

5. 为了提高功率MOSFET的工作频率，可以采取一些措施，如优化MOSFET的内部结构、改进材料工艺、提高散热设计等。

这些措施可以有效提高功率MOSFET的工作频率，使其适用于更高频率的电源系统中。

功率MOSFET的工作频率是影响其性能的重要参数之一，对于提高电源系统的效率和性能具有重要意义。

在实际应用中，需要根据具体的工作条件和要求来选择合适的功率MOSFET，并通过优化设计和材料工艺来提高其工作频率，以满足不同应用的需求。

Power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a widely used power device,monly used in power electronic equipment. It is known for its low switching loss, high efficiency, and fast switching speed, making it suitable for applications in AC to DC converters, inverters, power amplifiers, and other power-related fields. The operating frequency of a power MOSFET is a crucial parameter that influences its performance.1. The operating frequency of a power MOSFET refers to the frequency range at which the MOSFET operates normally while in use. Generally, the operating frequency of a power MOSFET is higher than that of a regular MOSFET, as it is used to handle higher power signals, requiring a faster response and switching speed.2. Increasing the operating frequency can enhance the efficiency and switching speed of a power MOSFET, subsequently improving the overall performance of the power system. Therefore, when choosing a power MOSFET, the operating frequency is an important factor to consider.3. The operating frequency of a power MOSFET is influenced by multiple factors, including the internal structure, material characteristics, and circuit design of the MOSFET. Among these, the structural parameters and material characteristics of the MOSFET are key determinants of the operating frequency.4. Additionally, the operating frequency of a power MOSFET is also affected by external operating conditions, such as input voltage, current load, etc. In practical applications, it is essential to select the appropriate power MOSFET based on specific operating conditions, ensuring that it can deliver the expected performance under normal working conditions.5. To enhance the operating frequency of a power MOSFET, measures can be taken, such as optimizing the internal structure of the MOSFET, improving material processes, and enhancing heat dissipation design. These measures can effectively boostthe operating frequency of the power MOSFET, making it suitable for higher-frequency power systems.In conclusion, the operating frequency of a power MOSFET is an important parameter that influences its performance and plays a significant role in enhancing the efficiency and overall performance of a power system. In practical applications, selecting the right power MOSFET based on specific operating conditions and requirements, as well as optimizing its design and material processes to increase its operating frequency, is crucial to meet the diverse needs of various applications.。

Nutrient removal in an A2O-MBR reactor with sludgereductionABSTRACTIn the present study, an advanced sewage treatment process has been developed by incorporating excess sludge reduction and phosphorous recovery in an A2O-MBR process. The A2O-MBR reactor was operated at a flux of 77 LMH over a period of 270 days. The designed flux was increased stepwise over a period of two weeks. The reactor was operated at two different MLSS range. Thermo chemical digestion of sludge was carried out at a fixed pH (11)and temperature (75℃) for 25% COD solubilisation. The released pbospborous was recovered by precipitation process and the organics was sent back to anoxic tank. The sludge digestion did not have any impact on COD and TP removal efficiency of the reactor. During the 270 days of reactor operation, the MBR maintained relatively constant transmembrane pressure. The results based on the study indicated that the proposed process configuration has potential to reduce the excess sludge production as well as it didn't detonated the treated water quality.Keywords: A2O reactor; MBR; Nutrient removal; TMP1. IntroductionExcess sludge reduction and nutrients removal are the two important problems associated with wastewater treatment plant. MBR process has been known as a process with relatively high decay rate and less sludge production due to much longer sludge age in the reactor (Wenet al., 2004). Sludge production in MBR is reduced by 28-68%, depending on the sludge age used (Xia et al.,2008). However, minimizing the sludge production by increasing sludge age is limited due to the potential adverse effect of high MLSS concentrations on membrane (Yoon et al., 2004). This problem can be solved by introducing sludge disintegration technique in MBR (Young et al., 2007). Sludge disintegration techniques have been reported to enhance the biodegradability of excess sludge (Vlyssides and Karlis, 2004). In overall, the basis for sludge reduction processes is effective combination of the methods for sludge disintegration and biodegradation of treated sludge. Advances in sludge disintegration techniques offer a few promising options including ultrasound (Guo et al., 2008), pulse power (Choi et al.,2006), ozone (Weemaes et al., 2000), thermal (Kim et al., 2003), alkaline (Li et al., 2008) acid (Kim et al., 2003) and thermo chemical(Vlyssides and Karlis, 2004). Among the various disintegration techniques, thermo chemical was reported to be simple and cost effective (Weemaes and Verstraete, 1998). In thermal-chemical hydrolysis, alkali sodium hydroxide was found to be the most effective agent in inducing cell lysis (Rocker et al., 1999). Conventionally, the nutrient removal was carried out in an A2O process. It has advantage of achieving, nutrient removal along with organic compound oxidation in a single sludge configuration using linked reactors in series (Tchobanoglous et al., 2003). The phosphoroes removal happens by subjecting phosphorous accumulating organisms (PAO) bacteria under aerobic and anaerobic conditions (Akin and Ugurlu, 2004). These operating procedures enhance predominance PAO, which are able to uptake phosphorous in excess. During the sludge pretreatment processes the bound phosphorous was solubilised and it increases the phosphorousconcentration in the effluent stream (Nishimura, 2001).So, it is necessary to remove the solubilised phosphorus before it enters into main stream. Besides, there is a growing demand for the sustainable phosphorous resources in the industrialized world. In many developed countries, researches are currently underway to recover the phosphoroes bound in the sludge's of enhanced biological phosphorus removal system (EBPR). The released phosphorous can be recovered in usable products using calcium salts precipitation method. Keeping this fact in mind, in the present study, a new advanced wastewater treatment process is developed by integrating three processes, which are: (a) thermo chemical pretreatment in MBR for excess sludge reduction (b) A2O process for biological nutrient removal (c) P recovery through calcium salt precipitation. The experimental data obtained were then used to evaluate the performance of this integrated system.2. Methods2.1. WastewaterThe synthetic domestic wastewater was used as the experimental influent. It was basically composed of a mixed carbon source, macro nutrients (N and P), an alkalinity control (NaHCO3) and a microelement solution. The composition contained (/L) 210 mg glucose, 200 mg NH4C1, 220 mg NaHCO3, 22一34 mg KH2PO4, microelement solution (0.19 mg MnCl2 4H20, 0.0018 mg ZnCl22H2O,0.022 mg CuCl22H2O, 5.6 mg MgSO47H2O, 0.88 mg FeCl36H2O,1.3 mg CaCl2·2H2O). The synthetic wastewater was prepared three times a week with concentrations of 210±1.5 mg/L chemical oxygen demand (COD), 40±1 mg/L total nitrogen (TN) and 5.5 mg/L total phosphorus (TP).2.2. A2O-MBRThe working volume of the A2O-MBR was 83.4 L. A baffle was placed inside the reactor to divide it into anaerobic (8.4 L) anoxic (25 L) and aerobic basin (50 L). The synthetic wastewater was feed into the reactor at a flow rate of 8.4 L/h (Q) using a feed pump. A liquid level sensor, planted in aerobic basin of A2O-MBR controlled the flow of influent. The HRT of anaerobic, anoxic and aerobic basins were 1, 3 and 6 h, respectively. In order to facilitate nutrient removal, the reactor was provided with two internal recycle (1R). IRl (Q= 1)connects anoxic and anaerobic and IR 2 (Q=3) was between aerobic and anoxic. Anaerobic and anoxic basins were provided with low speed mixer to keep the mixed liquid suspended solids (MLSS) in suspension. In the aerobic zone, diffusers were used to generate air bubbles for oxidation of organics and ammonia. Dissolved oxygen (DO) concentration in the aerobic basin was maintained at 3.5 mg/1 and was monitored continuously through online DO meter. The solid liquid separation happens inaerobic basin with the help of five flat sheet membranes having a pore size of 0.23 pm. The area of each membrane was 0.1 m2. They were connected together by a common tube. A peristaltic pumpwas connected in the common tube to generate suction pressure. In the common tube provision was made to accommodate pressure gauge to measure transmembrane pressure (TMP) during suction. The suction pump was operated in sequence of timing, which consists of 10 min switch on, and 2 min switch off.2.3. Thermo chemical digestion of sludgeMixed liquor from aerobic basin of MBR was withdrawn at the ratio of 1.5% of Q/day and subjected to thermo chemical digestion. Thermo chemical digestion was carried out at a fixed pH of 11(NaOH) and temperature of 75℃for 3 h. After thermo chemical digestion the supernatant and sludge were separated. The thermo-chemicallydigested sludge was amenable to further anaerobic bio-degradation (Vlyssides and Karlis, 2004), so it was sent to theanaerobic basin of the MBR2.4. Phosphorus recoveryLime was used as a precipitant to recover the phosphorous in the supernatant. After the recovery of precipitant the content was sent back to anoxic tank as a carbon source and alkalinity supelement for denitrification.2.5. Chemical analysisCOD, MLSS, TP, TN of the raw and treated wastewater were analyzed following methods detailed in (APHA, 2003). The influent and effluent ammonia concentration was measured using an ion-selective electrode (Thereto Orion, Model: 95一12). Nitrate in the sample was analyzed using cadmium reduction method (APHA, 2003).3. Results and discussionFig. 1 presents data of MLSS and yield observed during the operational period of the reactor. One of the advantages of MBR reactor was it can be operated in high MLSS concentration. The reactor was seeded with EBPR sludge from the Kiheung, sewage treatment plant, Korea. The reactor was startup with the MLSS concentration of 5700 mg/L. It starts to increase steadily with increase in period of reactor operation and reached a value of 8100 mg/L on day 38. From then onwards, MLSS concentration was maintained in the range of 7500 mg/L by withdrawing excess sludge produced and called run I. The observed yields (Yobs) for experiments without sludge digestion (run I) and with sludge digestion were calculated and given in Fig. 1. The Yobs for run I was found to be 0.12 gMLSS/g COD. It was comparatively lower than a value of 0.4 gMLSS/g CODreported for the conventional activated sludge processes (Tchoba-noglous et al., 2003). The difference in observed yield of these two systems is attributed to their working MLSS concentration. At high MLSS concentration the yield observed was found to be low (Visva-nathan et al., 2000). As a result of that MBR generated less sludge.The presently used MLSS ranges (7.5一10.5 g/L) are selected on the basis of the recommendation by Rosenberger et al. (2002). In their study, they reported that the general trend of MLSS increase on fouling in municipal applications seems to result in no impact at medium MLSS concentrations (7一12 g/L).It is evident from the data that the COD removal efficiency of A2O system remains unaffected before and after the introduction of sludge digestion practices. A test analysis showed that the differences between the period without sludge digestion (run I) and with sludge digestion (run II and III) are not statistically significant.However, it has been reported that, in wastewater treatment processes including disintegration-induced sludge degradation, the effluent water quality is slightly detonated due to the release of nondegradable substances such as soluble microbial products (Ya-sui and Shibata, 1994; Salcai et al., 1997; Yoon et al., 2004). During the study period, COD concentration in the aerobic basin of MBR was in the range of 18-38 mg/L and corresponding organic concentration in the effluent was varied from 4 to 12 mg/L. From this data it can be concluded that the membrane separation played an important role in providing the excellent and stable effluent quality.Phosphorus is the primary nutrient responsible for algal bloom and it is necessary to reduce the concentration of phosphorus in treated wastewater to prevent the algal bloom. Fortunately its growth can be inhibited at the levels of TP well below 1 mg/L (Mer-vat and Logan, 1996).Fig. 2 depicts TP removal efficiency of the A2O-MBR system during the period of study. It is clearly evident from the figure that the TP removal efficiency of A/O system was remains unaffected after the introduction of sludge reduction. In the present study, the solubilised phosphorous was recovered in the form of calcium phosphate before it enters into main stream. So, the possibility of phosphorus increase in the effluent due to sludge reduction practices has been eliminated. The influent TP concentration was in the range of 5.5 mg/L. During thefirst four weeks of operation the TP removal efficiency of the system was not efficient as the TP concentration in the effluent exceeds over 2.5 mg/L. The lower TP removal efficiency during the initial period was due to the slow growing nature of PAO organisms and other operational factors such as anaerobic condition and internal recycling. After the initial period, the TP removal efficiency in the effluent starts to increase with increase in period of operation. TP removal in A2O process is mainly through PAO organisms. These organisms are slow growing in nature and susceptible to various physicochemical factors (Carlos et al., 2008). During the study period TP removal efficiency of the system remains unaffected and was in the range of 74-82%.。

Until recently most historians spoke very critically of the Industrial Revolution.They1that in the long run industrialization greatly raised the standard of living for the2man.But they insisted that its3results during the period from1750to1850were widespread poverty and misery for the4of the English population.5contrast,they saw in the preceding hundred years from 1650to1750,when England was still a6agricultural country,a period of great abundance and prosperity.This view,7,is generally thought to be wrong.Specialists8history and economics,have 9two things:that the period from1650to1750was10by great poverty,and that industrialization certainly did not worsen and may have actually improved the conditions for the majority of the populace.1.［A］admitted［B］believed［C］claimed［D］predicted2.［A］plain［B］average［C］mean［D］normal3.［A］momentary［B］prompt［C］instant［D］immediate4.［A］bulk［B］host［C］gross［D］magnitude5.［A］On［B］With［C］For［D］By6.［A］broadly［B］thoroughly［C］generally［D］completely7.［A］however［B］meanwhile［C］therefore［D］moreover8.［A］at［B］in［C］about［D］for9.［A］manifested［B］approved［C］shown［D］speculated10.［A］noted［B］impressed［C］labeled［D］markedIndustrial safety does not just panies1low accident rates plan their safety programs,work hard to organize them,and continue working to keep them2and active.When the work is well done,a3of accident free operations is established4time lost due to injuries is kept at a minimum.Successful safety programs may5greatly in the emphasis placed on certain aspects of the program.Some place great emphasis on mechanical guarding.Others stress safe work practices by6 rules or regulations.7others depend on an emotional appeal to the worker.But,there are certain basic ideas that must be used in every program if maximum results are to be obtained.There can be no question about the value of a safety program.From a financial standpoint alone, safety8.The fewer the injury9,the better the workman’s insurance rate.This may mean the difference between operating at10or at a loss.1.［A］at［B］in［C］on［D］with2.［A］alive［B］vivid［C］mobile［D］diverse3.［A］regulation［B］climate［C］circumstance［D］requirement4.［A］where［B］how［C］what［D］unless5.［A］alter［B］differ［C］shift［D］distinguish6.［A］constituting［B］aggravating［C］observing［D］justifying7.［A］Some［B］Many［C］Even［D］Still8.［A］comes off［B］turns up［C］pays off［D］holds up9.［A］claims［B］reports［C］declarations［D］proclamations10.［A］an advantage［B］a benefit［C］an interest［D］a profitIf a farmer wishes to succeed,he must try to keep a wide gap between his consumption and his production.He must store a large quantity of grain1consuming all his grain immediately.He can continue to support himself and his family2he produces a surplus.He must use this surplus in three ways:as seed for sowing,as an insurance3the unpredictable effects of bad weather and as a commodity which he must sell in order to4old agricultural implements and obtain chemical fertilizers to5the soil.He may also need money to construct irrigation6and improve his farm in other ways.If no surplus is available,a farmer cannot be7.He must either sell some of his property or8extra funds in the form of loans.Naturally he will try to borrow money at a low9 of interest,but loans of this kind are not10obtainable.1.［A］other than［B］as well as［C］instead of［D］more than2.［A］only if［B］much as［C］long before［D］ever since3.［A］for［B］against［C］of［D］towards4.［A］replace［B］purchase［C］supplement［D］dispose5.［A］enhance［B］mix［C］feed［D］raise6.［A］vessels［B］routes［C］paths［D］channels7.［A］self-confident［B］self-sufficient［C］self-satisfied［D］self-restrained8.［A］search［B］save［C］offer［D］seek9.［A］proportion［B］percentage［C］rate［D］ratio10.［A］genuinely［B］obviously［C］presumably［D］frequentlyThe government is to ban payments to witnesses by newspapers seeking to buy up people involved in prominent cases1the trial of Rosemary West.In a significant2of legal controls over the press,Lord Irvine,the Lord Chancellor,will introduce a3bill that will propose making payments to witnesses4and will strictly control the amount of5that can be given to a case6a trial begins.In a letter to Gerald Kaufman,chairman of the House of Commons media select committee,Lord Irvine said he7with a committee report this year which said that self regulation did not8 sufficient control.9of the letter came two days after Lord Irvine caused a10of media protest when he said the11of privacy controls contained in European legislation would be left to judges12to Parliament.The Lord Chancellor said introduction of the Human Rights Bill,which13the European Convention on Human Rights legally14in Britain,laid down that everybody was15to privacy and that public figures could go to court to protect themselves and their families.“Press freedoms will be in safe hands16our British judges,”he said.Witness payments became an17after West was sentenced to10life sentences in1995.Up to 19witnesses were18to have received payments for telling their stories to newspapers.Concerns were raised19witnesses might be encouraged exaggerate their stories in court to20guilty verdicts.1.［A］as to［B］for instance［C］in particular［D］such as2.［A］tightening［B］intensifying［C］focusing［D］fastening3.［A］sketch［B］rough［C］preliminary［D］draft4.［A］illogical［B］illegal［C］improbable［D］improper5.［A］publicity［B］penalty［C］popularity［D］peculiarity6.［A］since［B］if［C］before［D］as7.［A］sided［B］shared［C］complied［D］agreed8.［A］present［B］offer［C］manifest［D］indicate9.［A］Release［B］Publication［C］Printing［D］Exposure10.［A］storm［B］rage［C］flare［D］flash11.［A］translation［B］interpretation［C］exhibition［D］demonstration12.［A］better than［B］other than［C］rather than［D］sooner than13.［A］changes［B］makes［C］sets［D］turns14.［A］binding［B］convincing［C］restraining［D］sustaining15.［A］authorized［B］credited［C］entitled［D］qualified16.［A］with［B］to［C］from［D］by17.［A］impact［B］incident［C］inference［D］issue18.［A］stated［B］remarked［C］said［D］told19.［A］what［B］when［C］which［D］that20.［A］assure［B］confide［C］ensure［D］guarantee2002年考研英语完型真题Comparisons were drawn between the development of television in the20th century and the diffusion of printing in the15th and16th centuries.Yet much had happened1.As was discussed before,it was not2the19th century that the newspaper became the dominant pre-electronic 3，following in the wake of the pamphlet and the book and in the4of the periodical.It was during the same time that the communications revolution5up,beginning with transport,the railway,and leading6through the telegraph,the telephone,radio,and motion pictures7the 20th century world of the motor car and the air plane.Not everyone sees that Process in8.It is important to do so.It is generally recognized,9,that the introduction of the computer in the early20th century, 10by the invention of the integrated circuit during the1960s,radically changed the process,11 its impact on the media was not immediately12.As time went by,computers became smaller and more powerful,and they became“personal”too,as well as13,with display becoming sharper and storage14increasing.They were thought of,like people,15generations, with the distance between generations much16.It was within the computer age that the term“information society”began to be widely used to describe the17within which we now live.The communications revolution has18both work and leisure and how we think and feel both about place and time,but there have been19 view about its economic,political,social and cultural implications.“Benefits”have been weighed 20“harmful”outcomes.And generalizations have proved difficult.1.［A］between［B］before［C］since［D］later2.［A］after［B］by［C］during［D］until3.［A］means［B］method［C］medium［D］measure4.［A］process［B］company［C］light［D］form5.［A］gathered［B］speeded［C］worked［D］picked6.［A］on［B］out［C］over［D］off7.［A］of［B］for［C］beyond［D］into8.［A］concept［B］dimension［C］effect［D］perspective9.［A］indeed［B］hence［C］however［D］therefore10.［A］brought［B］followed［C］stimulated［D］characterized11.［A］unless［B］since［C］lest［D］although12.［A］apparent［B］desirable［C］negative［D］plausible13.［A］institutional［B］universal［C］fundamental［D］instrumental14.［A］ability［B］capability［C］capacity［D］faculty15.［A］by means of［B］in terms of［C］with regard to［D］in line with16.［A］deeper［B］fewer［C］nearer［D］smaller17.［A］context［B］range［C］scope［D］territory18.［A］regarded［B］impressed［C］influenced［D］effected19.［A］competitive［B］controversial［C］distracting［D］irrational20.［A］above［B］upon［C］against［D］with2003年考研英语完型真题Teachers need to be aware of the emotional,intellectual,and physical changes that young adults experience.And they also need to give serious1to how they can best2such changes. Growing bodies need movement and3,but not just in ways that emphasize competition.4 they are adjusting to their new bodies and a whole host of new intellectual and emotional challenges, teenagers are especially self-conscious and need the5that comes from achieving success and knowing that their accomplishments are6by others.However,the typical teenage lifestyle is already filled with so much competition that it would be7to plan activities in which there are more winners than losers,8，publishing newsletters with many student-written book reviews,9 student artwork,and sponsoring book discussion clubs.A variety of small clubs can provide10 opportunities for leadership,as well as for practice in successful11dynamics.Making friends is extremely important to teenagers,and many shy students need the12of some kind of organization with a supportive adult13visible in the background.In these activities,it is important to remember that the young teens have14attention spans.A variety of activities should be organized15participants can remain active as long as they want and then go on to16else without feeling guilty and without letting the other participants 17.This does not mean that adults must accept irresponsibility.18they can help students acquire a sense of commitment by19for roles that are within their20and their attention spans and by having clearly stated rules.1.[A]thought[B]idea[C]opinion[D]advice2.[A]strengthen[B]accommodate[C]stimulate[D]enhance3.[A]care[B]nutrition[C]exercise[D]leisure4.[A]If[B]Although[C]Whereas[D]Because5.[A]assistance[B]guidance[C]confidence[D]tolerance6.[A]claimed[B]admired[C]ignored[D]surpassed7.[A]improper[B]risky[C]fair[D]wise8.[A]in effect[B]as a result[C]for example[D]in a sense9.[A]displaying[B]describing[C]creating[D]exchanging10.[A]durable[B]excessive[C]surplus[D]multiple11.[A]group[B]individual[C]personnel[D]corporation12.[A]consent[B]insurance[C]admission[D]security13.[A]particularly[B]barely[C]definitely[D]rarely14.[A]similar[B]long[C]different[D]short15.[A]if only[B]now that[C]so that[D]even if16.[A]everything[B]anything[C]nothing[D]something17.[A]off[B]down[C]out[D]alone18.[A]On the contrary[B]On the average[C]On the whole[D]On the other hand19.[A]making[B]standing[C]planning[D]taking20.[A]capability[B]responsibility[C]proficiency[D]efficiency2004年考研英语完型真题Many theories concerning the causes of juvenile delinquency(crimes committed by young people)focus either on the individual or on society as the major contributing influence.Theories 1on the individual suggest that children engage in criminal behavior2they were not sufficiently penalized for previous misdeeds or that they have learned criminal behavior through 3with others.Theories focusing on the role of society suggest that children commit crimes in 4to their failure to rise above their socioeconomic status,5as a rejection of middle-class values.Most theories of juvenile delinquency have focused on children from disadvantaged families,_6 the fact that children from wealthy homes also commit crimes.The latter may commit crimes7 lack of adequate parental control.All theories,however,are tentative and are8to criticism.Changes in the social structure may indirectly9juvenile crime rates.For example, changes in the economy that10to fewer job opportunities for youth and rising unemployment 11make gainful employment increasingly difficult to obtain.The resulting discontent may in12 lead more youths into criminal behavior.Families have also13changes these years.More families consist of one-parent households or two working parents;14，children are likely to have less supervision at home15was common in the traditional family16.This lack of parental supervision is thought to be an influence on juvenile crime rates.Other17causes of offensive acts include frustration or failure in school,the increased18of drugs and alcohol,and the growing19of child abuse and child neglect.All these conditions tend to increase the probability of a child committing a criminal act, 20a direct causal relationship has not yet been established.1.[A]acting[B]relying[C]centering[D]commenting2.[A]before[B]unless[C]until[D]because3.[A]interaction[B]assimilation[C]cooperation[D]consultation4.[A]return[B]reply[C]reference[D]response5.[A]or[B]but rather[C]but[D]or else6.[A]considering[B]ignoring[C]highlighting[D]discarding7.[A]on[B]in[C]for[D]with8.[A]immune[B]resistant[C]sensitive[D]subject9.[A]affect[B]reduce[C]chock[D]reflect10.[A]point[B]lead[C]come[D]amount11.[A]in general[B]on average[C]by contrast[D]at length12.[A]case[B]short[C]turn[D]essence13.[A]survived[B]noticed[C]undertaken[D]experienced14.[A]contrarily[B]consequently[C]similarly[D]simultaneously15.[A]than[B]that[C]which[D]as16.[A]system[B]structure[C]concept[D]heritage17.[A]assessable[B]identifiable[C]negligible[D]incredible18.[A]expense[B]restriction[C]allocation[D]availability19.[A]incidence[B]awareness[C]exposure[D]popularity20.[A]provided[B]since[C]although[D]supposing11。

ENVIRONMENTAL BIOTECHNOLOGYOne-stage partial nitritation/anammox at15°Con pretreated sewage:feasibility demonstration at lab-scale Haydée De Clippeleir&Siegfried E.Vlaeminck&Fabian De Wilde&Katrien Daeninck&Mariela Mosquera&Pascal Boeckx&Willy Verstraete&Nico BoonReceived:26November2012/Revised:28January2013/Accepted:30January2013#Springer-Verlag Berlin Heidelberg2013Abstract Energy-positive sewage treatment can beachieved by implementation of oxygen-limited autotrophicnitrification/denitrification(OLAND)in the main water line,as the latter does not require organic carbon and thereforeallows maximum energy recovery through anaerobic diges-tion of organics.To test the feasibility of mainstreamOLAND,the effect of a gradual temperature decrease from29to15°C and a chemical oxygen demand(COD)/Nincrease from0to2was tested in an OLAND rotatingbiological contactor operating at55–60mg NH4+–NL−1 and a hydraulic retention time of1h.Moreover,the effectof the operational conditions and feeding strategies on thereactor cycle balances,including NO and N2O emissionswere studied in detail.This study showed for the first timethat total nitrogen removal rates of0.5g NL−1day−1can bemaintained when decreasing the temperature from29to15°Cand when low nitrogen concentration and moderate CODlevels are treated.Nitrite accumulation together with elevatedNO and N2O emissions(5%of N load)were needed to favoranammox compared with nitratation at low free ammonia(<0.25mg NL−1),low free nitrous acid(<0.9μg NL−1),and higher DO levels(3–4mg O2L−1).Although the total nitrogen removal rates showed potential,the accumulation of nitrite and nitrate resulted in lower nitrogen removal efficiencies (around40%),which should be improved in the future. Moreover,a balance should be found in the future between the increased NO and N2O emissions and a decreased energy consumption to justify OLAND mainstream treatment. Keywords Energyself-sufficient.Nitrospira.Nitricoxide. Nitrous oxide.DeammonificationIntroductionCurrently,around40full-scale one-stage partial nitrita-tion/anammox plants are implemented to treat highly loaded nitrogen streams devoid in carbon(Vlaeminck et al.2012). This process,known under the acronyms oxygen-limited autotrophic nitrification/denitrification(OLAND)(Kuai and Verstraete1998),deammonification(Wett2006),com-pletely autotrophic nitrogen removal over nitrite(Third et al. 2001),etc.,showed highly efficient and stable performance when treating digestates from sewage sludge treatment plants and industrial wastewaters(Wett2006;Abma et al. 2010;Jeanningros et al.2010).For clarity,one-stage partial nitritiation/anammox processes will be referred to as OLAND in this work.From an energy point of view,the implementation of the OLAND process for the treatment of sewage sludge digestate decreased the net energy consump-tion of a municipal wastewater treatment plant(WWTP)by 50%,with a combination of a lower aeration cost in the side stream and the opportunity to recover more organics from the mainstream(Siegrist et al.2008).Moreover,when co-digestion of kitchen waste was applied,an energyneutral Electronic supplementary material The online version of this article(doi:10.1007/s00253-013-4744-x)contains supplementary material,which is available to authorized users.H.De Clippeleir:S.E.Vlaeminck:F.De Wilde:K.Daeninck:M.Mosquera:W.Verstraete:N.Boon(*)Laboratory for Microbial Ecology and Technology(LabMET),Ghent University,Coupure Links653,9000Gent,Belgiume-mail:Nico.Boon@UGent.beP.BoeckxLaboratory of Applied Physical Chemistry(ISOFYS),Ghent University,Coupure Links653,9000Gent,BelgiumAppl Microbiol BiotechnolDOI10.1007/s00253-013-4744-xWWTP was achieved(Wett et al.2007).To fully recover the potential energy present in wastewater,a first idea of a new sustainable wastewater treatment concept was reported (Jetten et al.1997).Recently,a“ZeroWasteWater”concept was proposed which replaces the conventional activated sludge system by a highly loaded activated sludge step (A-step),bringing as much as organic carbon(chemical oxygen demand(COD))as possible to the solid fraction, and a second biological step(B-step)removing the residual nitrogen and COD with a minimal energy demand (Verstraete and Vlaeminck2011).Subsequently,energy is recovered via anaerobic digestion of the primary and sec-ondary sludge.For the B-step in the main line,OLAND would potentially be the best choice as this process can work at a low COD/N ratio,allowing maximum recovery of COD in the A-step.Moreover,it was calculated that if OLAND is implemented in the main water treatment line and a maximum COD recovery takes place in the A-step,a net energy gain of the WWTP of10Wh inhabitant equivalent (IE)−1day−1is feasible(De Clippeleir et al.2013).To allow this energy-positive sewage treatment,OLAND has to face some challenges compared with the treatment of highly loaded nitrogen streams(>250mg NL−1).A first difference is the lower nitrogen concentration to be removed by OLAND.Domestic wastewater after advanced concen-tration will still contain around30–100mg NL−1and113–300mg CODL−1(Metcalf and Eddy2003;Tchobanoglous et al.2003;Henze et al.2008).High nitrogen conversion rates(around400mg NL−1day−1)by the OLAND process can be obtained at nitrogen concentrations of30–60mg N L−1and at low hydraulic retention times(HRT)of1–2h(De Clippeleir et al.2011).A second challenge is the low tem-perature at which OLAND should be operated(10–15°C compared with34°C).Several studies already described the effect of temperature on the activity of the separate micro-bial groups(Dosta et al.2008;Guo et al.2010;Hendrickx et al.2012).Only a few studies showed the long-term effect of a temperature decrease below20°C on the microbial bal-ances of anoxic and aerobic ammonium-oxidizing bacteria (AnAOB and AerAOB)and nitrite-oxidizing bacteria (NOB)at nitrogen concentrations above100mg NL−1 (Vazquez-Padin et al.2011;Winkler et al.2011).However, the combination of low temperature and low nitrogen con-centration was never tested on a co-culture of AerAOB, AnAOB,and NOB before.At temperatures around15°C, maintaining the balance between NOB and AnAOB and the balance between NOB and AerAOB will get more challeng-ing since the growth rate of NOB will become higher than the growth rate of AerAOB(Hellinga et al.1998). Therefore,it will not be possible to wash out NOB based on overall or even selective sludge retention.The third and main challenge in this application will therefore be the suppression of NOB at temperature ranges of10–20°C and at nitrogen concentration ranges of30–60mg NL−1 (low free ammonia and low nitrous acid),which was not shown before.A final fourth challenge will include the higher input of organics at moderate levels of90–240mg biodegradable CODL−1in the wastewater.Depending on the raw sewage strength,COD/N ratios between2and3are expected after the concentration step,which is on the edge of the described limit for successful OLAND(Lackner et al. 2008).The presence of organics could result in an extra competition of heterotrophic denitrifiers with AerAOB for oxygen or with AnAOB for nitrite or organics,since certain AnAOB can denitrify consuming organic acids (Kartal et al.2007).In this study,the challenges2to4,were evaluated in an OLAND rotating biological contactor(RBC).This reactor at 29°C was gradually adapted over24,22,and17to15°C under synthetic wastewater conditions(60mg N L−1, COD/N of0).Additionally,the COD/N ratio of the influent was increased to2by supplementing NH4+to diluted sewage to simulate pretreated sewage.The effect of the operational conditions and feeding strategies on the reactor cycle balan-ces,including gas emissions and microbial activities were studied in detail.An alternative strategy to inhibit NOB activity and as a consequence increase AnAOB activity at low temperatures based on NO production was proposed. Materials and methodsOLAND RBCThe lab-scale RBC described by De Clippeleir et al.(2011) was further optimized at29°C by an increase in the influent nitrogen concentration from30to60mg NL−1and a limitation of the oxygen input through the atmosphere by covering the reactor before this test was started.The reactor was based on an air washer LW14(Venta,Weingarten, Germany)with a rotor consisting of40discs interspaced at 3mm,resulting in a disc contact surface of1.32m2.The reactor had a liquid volume of2.5L,immersing the discs for 55%.The latter was varied over the time of the experiment. The reactor was placed in a temperature-controlled room. The DO concentration was not directly controlled.In this work,continuous rotation was applied at a constant rotation speed of3rpm,which allowed mixing of the water phase. RBC operationThe RBC was fed with synthetic wastewater during phases I to VII.From phase VIII onwards,the COD/N was gradually increased(phases VIII–X)to2(phases XI–XIII).The syn-thetic influent of an OLAND RBC,consisted of(NH4)2SO4 (55–60mg NL−1),NaHCO3(16mg NaHCO3mg−1N),andAppl Microbiol BiotechnolKH2PO4(10mg PL−1).Pretreated sewage was simulated by diluting raw sewage of the communal WWTP of Gent, Belgium(Aquafin).The raw wastewater after storage at 4°C and settlement contained23–46mg NH4+–NL−1, 0.2–0.4mg NO2−–NL−1,0.4–2.7mg NO3−–NL−1,23–46mgKjeldahl–NL−1,3.8–3.9mg PO43−–PL-1,26–27mg SO42−–S L−1,141–303mg COD tot L−1,and74–145mg COD sol L−1.The raw sewage was diluted by factors2–3to obtain COD values around110mg COD tot L−1and by addition of(NH4)2SO4to obtain final COD/N values around2.The reactor was fed in a semi-continuous mode:two periods of around10min/h for phases I–XI and one period of20min/h for phases XII and XIII.The influent flow range varied from47to65Lday−1and the reactor volume from3.7to2.5L(during78and55% submersion,respectively).Corresponding HRTare displayed in Tables1and2.Reactor pH,DO,and temperature were daily monitored and influent and effluent samples were taken at least thrice a week for ammonium,nitrite,nitrate,and COD analyses. Detection of AerAOB,NOB,and AnAOB with FISHand qPCRFor NOB and AnAOB,a first genus screening among the most commonly present organisms was performed by fluo-rescent in-situ hybridization(FISH)on biomass of days1 (high temperature)and435(low temperature and COD presence).A paraformaldehyde(4%)solution was used for biofilm fixation,and FISH was performed according to Amann et al.(1990).The Sca1309and Amx820probes were used for the detection of Cand.Scalindua and Cand. Kuenenia&Brocadia,respectively,and the NIT3and Ntspa662probes and their competitors for Nitrobacter and Nitrospira,respectively(Loy et al.2003).This showed the absence of Nitrobacter and Scalindua(Table S1in the Electronic supplementary material(ESM)).Biomass sam-ples(approximately5g)for nucleic acid analysis were taken from the OLAND RBC at days1,60,174,202,306,385, 399,and413of the operation.DNA was extracted using FastDNA®SPIN Kit for Soil(MP Biomedicals,LLC), according to the manufacturer’s instructions.The obtained DNA was purified with the Wizard®DNA Clean-up System (Promega,USA)and its final concentration was measured spectrophotometrically using a NanoDrop ND-1000spec-trophotometer(Nanodrop Technologies).The SYBR Green assay(Power SyBr Green,Applied Biosystems)was used to quantify the16S rRNA of AnAOB and Nitrospira sp.and the functional amoA gene for AerAOB.The primers for quantitative polymerase chain reactions(qPCR)for detection of AerAOB,NOB,and AnAOB were amoA-1F–amoA-2R (Rotthauwe et al.1997),NSR1113f–NSR1264r(Dionisi et al. 2002),and Amx818f–Amx1066r(Tsushima et al.2007),re-spectively.For bacterial amoA gene,PCR conditions were: 40cycles of94°C for1min,55°C for1min,and60°C for 2min.For the amplification of Nitrospira sp.16S rRNA gene, 40cycles of95°C for1min,50°C for1min,and60°C for 1min were used while for AnAOB16S rRNA the PCR temperature program was performed by40cycles of15s at 94°C and1min at60°C.Plasmid DNAs carrying NitrospiraTable1Effect of temperature decrease on the operational conditions and performance of OLAND RBC reactorPhase I II III IV V VI VIIPeriod(days)1–2122–3536–6162–210210–263263–274275–306 Immersion level(%)78787878557855 Temperature(°C)29±224±122±0.617±1.216±0.915±0.814±0.4 Operational conditionsDO(mg O2L−1) 1.1±0.2 1.3±0.2 1.4±0.1 1.7±0.3 2.8±0.4 2.4±0.2 3.1±0.2 pH(−)7.5±0.17.5±0.17.5±0.17.6±0.17.7±0.17.7±0.17.8±0.1 HRT(h) 1.85±0.04 1.84±0.09 1.73±0.04 1.86±0.11 1.09±0.02 1.57±0.02 1.09±0.02 FA(mg NL−1)0.35±0.180.36±0.180.34±0.140.36±0.130.25±0.160.33±0.170.13±0.04 FNA(μg NL−1)0.3±0.10.3±0.20.4±0.20.4±0.10.9±0.40.6±0.10.9±0.2 PerformanceTotal N removal efficiency(%)54±552±549±934±936±936±942±4 Relative NO3−prod(%of NH4+cons a)7±17±17±114±618±916±321±4 Relative NO2−accum(%of NH4+cons)2±43±45±515±530±826±631±5 AerAOB activity(mg NH4+–NL−1day−1)267±38267±49260±52260±53811±229460±44986±71 NOB activity(mg NO2–NL−1day−1)0±00±00±09±1260±9420±585±25 AnAOB activity(mg N tot L−1day−1)412±38403±37368±76248±67448±117305±74529±75DO dissolved oxygen,HRT hydraulic retention time,F A free ammonia,FNA free nitrous acid,cons consumption,prod production,accum accumulation,tot totala NH4+consumption is corrected for nitrite accumulationAppl Microbiol Biotechnoland AnAOB16S rRNA gene and AerAOB functional AmoA gene,respectively,were used as standards for qPCR.All the amplification reactions had a high correlation coefficient (R2>0.98)and slopes between−3.0and−3.3.Detailed reactor cycle balancesFor the measurements of the total nitrogen balance,including the NO and N2O emissions,the OLAND RBC was placed in a vessel(34L)which had a small opening at the top(5cm2).In this vessel,a constant upward air flow(around1ms−1or0.5L s-1)was generated to allow calculations of emission rates.On the top of the vessel(air outlet),the NO and N2O concentra-tion was measured,off-and online,respectively.NH3emis-sions were negligible in a RBC operated at about2mg NH3–NL−1(Pynaert et al.2003).Since FA levels in the currentstudy are about ten times lower,NH3emissions were not included.In the water phase,ammonium,nitrite,nitrate,hy-droxylamine(NH2OH),N2O,and COD concentrations were measured.Moreover,DO concentration and pH values were monitored.The air flow was measured with Testo425hand probe(Testo,Ternat,Belgium).Chemical analysesAmmonium(Nessler method)was determined according to standard methods(Greenberg et al.1992).Nitrite and nitrate were determined on a761compact ion chromatograph equipped with a conductivity detector(Metrohm,Zofingen, Switzerland).Hydroxylamine was measured spectrophoto-metrically(Frear and Burrell1955).The COD was determined with NANOCOLOR®COD1500en NANOCOLOR®COD 160kits(Macherey-Nagel,Düren,Germany).The volumetric nitrogen conversion rates by AerAOB,NOB,and AnAOB were calculated based on the measured influent and effluent compositions and the described stoichiometries,underestimat-ing the activity of AnAOB by assuming that all COD removed was anoxically converted with nitrate to nitrogen gas (Vlaeminck et al.2012).DO and pH were measured with respectively,a HQ30d DO meter(Hach Lange,Düsseldorf, Germany)and an electrode installed on a C833meter (Consort,Turnhout,Belgium).Gaseous N2O concentrations were measured online at a time interval of3min with a photo-acoustic infrared multi-gas monitor(Brüel&Kjær, Model1302,Nærem,Denmark).Gas grab samples were taken during the detailed cycle balance tests for NO detec-tion using Eco Physics CLD77AM(Eco Physics AG, Duernten,Switzerland),which is based on the principle of chemiluminescence.For dissolved N2O measurements,a1-mL filtered(0.45μm)sample was brought into a7-mL vacutainer(−900hPa)and measured afterwards by pressure adjustment with He and immediate injection at21°C in a gas chromatograph equipped with an electron capture detector (Shimadzu GC-14B,Japan).Table2Effect of COD/N increase on the operational conditions and performance of OLAND RBC reactorPhase VIII IX X XI XII XIIIPeriod(days)355–361362–369370–374375–406407–421422–435 Immersion level(%)555555555555COD/N(-)0.51 1.5222 Feeding regime(pulsesh−1)222211 Operational conditionsDO(mg O2L−1) 2.9±0.3 2.5±0.6 2.4±0.3 3.0±0.7 3.6±0.3 3.2±0.3 pH(−)7.8±0.027.7±0.17.6±0.027.6±0.17.6±0.27.6±0.1 HRT(h) 1.06±0.11 1.03±0.020.92±0.020.94±0.05 1.10±0.05 1.06±0.2 FA(mg NL−1)0.10±0.050.04±0.050.15±0.050.21±0.100.23±0.120.04±0.02 FNA(μg NL−1)0.4±0.10.2±0.20.2±0.010.3±0.10.2±0.10.6±0.2 PerformanceTotal N removal efficiency(%)36±545±1823±328±623±1342±3 Relative NO3−prod(%of NH4+cons a)42±543±1263±250±662±1846±6 Relative NO2−accum(%of NH4+cons)20±410±105±18±37±413±6 AerAOB activity(mg NH4+–NL−1day−1)592±15446±31238±28352±73289±138600±204 NOB activity(mg NO2−–NL−1day−1)257±19294±81465±60352±84427±115394±76 AnAOB activity(mg N tot L−1day−1)385±86452±205262±39355±73281±159481±73COD removal rates were negligible in all phasesDO dissolved oxygen,HRT hydraulic retention time,F A free ammonia,FNA free nitrous acid,cons consumption,prod production,accum accumulation,tot totala NH4+consumption is corrected for nitrite accumulationAppl Microbiol BiotechnolResultsEffect of temperature decreaseDuring the reference period (29°C),a well-balanced OLAND performance (Fig.1;Table 1)was reached with minimal nitrite accumulation (2%)and minimal nitrate production (7%).This was reflected in an AerAOB/AnAOB activity ratio of 0.6(Table 1,phase I).The total nitrogen removal rate was on average 470mg N L −1day −1or 1314mg Nm −2day −1,and the total nitrogen removal efficiency was 54%.Decreasing the temperature from 29to 24°C and further to 22°C over the following 40days,did not result in anysignificant changes of the operational conditions (Table 1;phases I –III),performance of the reactor (Fig.1)or abun-dance of the bacterial groups (qPCR;Fig.S1in the ESM ).However at 17°C,a decrease in total nitrogen removal efficiency was observed (Table 1;phase IV).An imbalance between the AerAOB and the AnAOB was apparent from a stable AerAOB activity yet a declining AnAOB activity.Moreover,NOB activity was for the first time detected in spite of free ammonia (FA)and free nitrous acid (FNA)con-centrations did not change (Table 1;phase IV).Moreover,no significant differences in abundance of NOB,AerAOB,and AnAOB could be detected with qPCR (Fig.S1in the ESM ).However,DO concentrations started to increase during that period from 1.4to 1.7mg O 2L −1.As the availabilityofFig.1Phases I –VII:effect of temperature decrease on the volumetric rates (top )and nitrogen concentrations (bottom )Appl Microbiol Biotechnoloxygen through the liquid phase did not seem to be satisfac-tory to counteract the decrease in ammonium removal effi-ciency,the immersion level was lowered to55%to increase the availability of oxygen through more air-biofilm contact surface.Consequently,the volumetric loading rate increased (factor1.7)due to the decrease in reactor volume(day210, Fig.1).This action allowed higher ammonium removal effi-ciencies due to higher AerAOB activities(factor3).AnAOB activity increased with a similar factor as the volumetric loading rate(1.8compared with1.7)consequently resulting in an increased imbalance between these two groups of bac-teria(Table1;phase V).Moreover,although the FNA in-creased with a factor2,the NOB activity increased with a factor7,resulting in a relative nitrate production of30% (Table1;phase V).As NOB activity prevented good total nitrogen removal efficiencies,the immersion level was in-creased again to78%(day263;Fig.1).This resulted indeed in a lower NOB activity(Table1;phase VI).However,also the AerAOB activity decreased with the same factor,due to the lower availability of atmospheric oxygen.Therefore,the reactor was subsequently operated again at the lower immer-sion level(55%)to allow sufficient aerobic ammonium conversion.The latter allowed a stable removal efficiency of 42%.The AnAOB activity gradually increased to a stable anoxic ammonium conversion rate of529mg NL−1day−1. During the synthetic phase,no changes in AerAOB, AnAOB,and NOB abundance were measured with qPCR (Fig.S1in the ESM).The effluent quality was however not optimal as still high nitrite(around15mg NL−1)and nitrate (around13mg NL−1)levels were detected.Effect of COD/N increaseThe synthetic feed was gradually changed into pretreated sewage by diluting raw sewage and adding additional nitro-gen to obtain a certain COD/N ratio.During the first3weeks of this period(Fig.2),the COD/N ratio was gradually increased from0.5to2.Due to the short adaptation periods (1week per COD/N regime),the performance was unstable (Fig.2;Table2,phases VIII–XI).Compared with the end of the synthetic period(phase VII),operation at a COD/N ratio of2(phase XI)resulted in a sharp decrease in nitrite accu-mulation(Fig.2)and an increase in the ammonium and nitrate levels.This indicated increased NOB activity(factor 4),decreased AerAOB(factor3)and decreased AnAOB (factor2)activity(Tables1and2).To allow higher nitrogen removal rates,the HRT was increased from0.94to1.1h,by decreasing the influent flow rate.Moreover,the feeding regime was changed from two pulses of10min in1h to one period of20min/h.These actions did not significantly decrease the effluent nitrogen concentration(Fig.2)and did not influence the microbial activities(Table2,phase XII). Therefore the loading rate was again increased to the levels before phase XII.However,the single-pulse feeding wasmaintained.This resulted in high ammonium removal effi-ciencies and therefore low ammonium effluent concentra-tion around dischargeable level(4±1mg NH4+–NL−1; Fig.2).Nitrate and nitrite accumulation were not counter-acted by denitrification as only0.02mg CODL−1day−1wasremoved.Therefore,nitrite and nitrate levels were still toohigh to allow effluent discharge.The total nitrogen removalefficiency(42%)and rate(549±83mg NL−1day−1or1,098±106mgNm−2day−1)at COD/N ratios of2wassimilar as during the synthetic period(phase VII).Comparedwith the reference period at29°C,the total nitrogen removalrate did not changed significantly(470±43versus549±83mgNL−1day−1at high and low temperatures,respectively).The22%lowered removal efficiency was merely due to anincreased nitrogen loading rate.Nitratation and NO/N2O emissionsAt the end of the synthetic phase(phase VII)and the end ofthe experiment(phase XIII),the total nitrogen balance of thereactor was measured.A total nitrogen balance was obtainedby measuring all nitrogen species(NH4+,NO2−,NO3−,NH2OH,and N2O)in the liquid phase and N2O and NO inthe gas phase.A constant air flow,diluting the emitted N2Oand NO concentrations was created over the reactor tomeasure gas fluxes over time.The effect of the loading rate,feeding pattern,and concentration of nitrite and ammoniumon the total nitrogen balance in the reactor were tested(Table3).NH2OH measurements showed low concentra-tions(<0.2mg NL−1)in all tests,making it difficult to linkthe profiles with the N2O emission.Lowering the loading rate by increasing the HRT(Table3,test B)increased the DO values and allowed higherDO fluctuations over time at synthetic conditions.Moreover,NOB activity increased significantly resultingin lower total nitrogen removal efficiencies and high levelsof nitrate in the effluent(Table3,test B).The relative N2Oemissions did not change and were relatively high(6%of Nload).However,the concentration of N2O in the liquid andin the gas phase decreased with a factor2(Table3).When pretreated sewage was fed to the reactor,theOLAND RBC was operated at lower nitrite concentration,while similar ammonium and nitrate concentrations wereobtained(Table3,test C).The lower nitrite concentrationshowever did not result in lower N2O emission rates.Whenthe feeding regime was changed to a more continuous-likeoperation(4pulses/h),the N2O emission increased signifi-cantly,while NO emission remained constant(Table3,testD).Due to the lower ammonium removal efficiency(65compared with81%),but similar relative nitrite and nitrateaccumulation rate,the total nitrogen removal efficiencydecreased.Appl Microbiol BiotechnolWhen a nitrite pulse was added just after feeding,about 20mg NO 2−–NL −1was obtained in the reactor.This did increase the NO and N 2O emissions significantly (p <0.05)compared with the same feeding pattern (Table 3,tests C –E).Although similar constant total nitrogen removal efficien-cies were obtained during this operation,a significant (p <0.05)decrease in the relative nitrate production was observed.The latter was mainly caused by a global increase in AnAOB activity.In the last test (F),the influent ammo-nium concentration was doubled,leading to higher ammo-nium and also FA concentrations (1±0.4mg N L −1compared with 0.1±0.4mg NL −1).Due to overloading of the system,the total nitrogen removal efficiency decreased.However,at these conditions a lower relative nitrate pro-duction was obtained;due to a decrease in NOB and in-crease in AnAOB activity (Table 3,test F).Together with this,increased NO and N 2O emissions were observed.As the influence of the nitrogen loading and DO concentration could be considered minor in this test range (Fig.S2in the ESM ),these tests show a relation between increased NO emissions and decreased relative nitrate productions (Table 3).When the activity during the feeding cycle was studied in more detail,it could be concluded that the highest nitrogen conversion rates took place during the feeding period,which was characterized by a high substrate availability and high turbulence (Fig.3).As the HRT is only 1h,the reactor volume is exchanged in 20min.During this phase,ammo-nium increased,while nitrite and nitrate concentrations de-creased due to dilution (Figs.S3,S4,and S5in the ESM ).The NOB/AnAOB ratio was around 1,which means that NOB were able to take twice as much nitrite thanAnAOBFig.2Phases VIII –XIII:effect of COD/N increase on the volumetric rates (top )and nitrogen concentrations (bottom ).Data during the N balance tests (days 424–431)were not incorporated in the figure but are shown in Table 3Appl Microbiol BiotechnolTable 3Operational parameters and nitrogen conversion rates during the six different RBC operations which differ from feeding composition and feeding regime (volume at 2.5L and 50%immersion of the discs,days 307–309for synthetic feed,and days 424–431)Reactor phaseVII (synthetic)XIII (pretreated sewage)Test A a B C a D E -F Additive––––NO 2−NH 4+Feeding regime (pulses/h)221411Total N loading rate (mg NL −1day −1)1,1695851,3401,5541,7372,718Temperature water (°C)15±0.316±0.2*14±0.415±0.1*16±0.1*15±0.4DO (mg O 2L −1) 2.9±0.1 3.7±0.6* 4.0±0.1 3.2±0.1* 3.3±0.1* 3.2±0.1*pH (-)7.6±0.067.6±0.057.6±0.047.6±0.017.6±0.027.8±0.02*Ammonium out (mg NL −1)9±1 1.4±1*11±319±3*12±158±4*Nitrite out (mg NL −1)14±213±16±16±0.418±2*9±0.3*Nitrate out (mg NL −1)17±337±6*18±216±1*18±0.420±0.4NH 4+oxidation rate (mg NL −1day −1)895±22509±2*1,051±73957±891,053±161,285±93*Relative nitrite accumulation (%)25±320±1*14±315±18±4*15±1Relative nitrate production (%)36±876±6*48±147±342±2*34±3*Total efficiency (%)38±417±4*35±328±4*32±227±4*AerAOB activity (mg NH 4+–NL −1day −1)658±88469±17*827±44781±57795±30938±46*NOB activity (mg NO 2−–NL −1day −1)174±59299±28*375±38342±24*362±13277±18*AnAOB activity (mg N tot L −1day −1)205±3849±13*234±20218±29263±15*354±49*N 2O in liquid (μg NL −1)64±4630±22*78±12104±29*61±1374±4NO emission (mg Nday −1)0.53±0.03n.d.0.66±0.060.74±0.08 1.65±0.18*0.82±0.1*N 2O emission (mg Nday −1)151±2893±23*170±19179±6*274±37*202±18*%N 2O emission on loading5.1±1.06.4±1.6*5.0±0.64.5±0.2*6.2±0.8*3.0±0.3*aReference period for synthetic and pretreated sewage*p <0.05,significant differences compared with referenceperiod Fig.3Detailed NO/N 2Omonitoring during the reference test (Table 3,test C)and when nitrite was pulsed (Table 3,test E)and effect on AerAOB,AnAOB,and NOB activity during the different phases of the feeding cycle.Significant differences in AerAOB,AnAOB,NOB,and NO/N 2O concentration compared with the reference period areindicated with asterisks ,circles ,double quotation mark ,and plus sign ,respectivelyAppl Microbiol Biotechnol。

装备环境工程第20卷第12期·128·EQUIPMENT ENVIRONMENTAL ENGINEERING2023年12月××飞机滑轨内腔的加速腐蚀试验环境谱制定樊伟杰1，张勇1，朱彦海2，杨文飞1，孟莉莉2，褚贵文3（1.海军航空大学青岛校区，山东 青岛 266041；2.中国航空制造技术研究院，北京 100010；3.山东科技大学，山东 青岛 266590）摘要：目的对运行环境逐渐复杂的××飞机滑轨内腔进行加速腐蚀试验的研究。

考虑到外部环境对滑轨内腔的腐蚀影响，旨在提出一种适用于江津地区的加速腐蚀试验环境谱，以更好地模拟实际运行条件下滑轨内腔的腐蚀过程。

方法设计江津地区滑轨内腔的加速腐蚀试验环境谱，以外露部位防护涂层加速腐蚀试验环境参考谱以及相应环境的分析为依据，根据参考谱的参数制定方法，针对江津地区的特定环境条件，设计本环境谱的编制依据。

进一步确定湿热、紫外暴露、温度冲击、低气压以及盐雾等参数，得出系统的××飞机滑轨内腔的加速腐蚀试验环境谱。

结果成功形成了系统的××飞机滑轨内腔的加速腐蚀试验环境谱，综合考虑了江津地区的环境特点，并参考了外露部位防护涂层加速腐蚀试验环境谱的相关参数，通过对湿热、紫外暴露、温度冲击、低气压以及盐雾等参数的确定，能够更准确地模拟滑轨内腔在实际运行条件下的腐蚀过程。

结论该环境谱可为飞机制造商和维护人员提供重要的参考，以评估滑轨内腔的腐蚀情况，并采取相应的防护措施。

通过更准确地模拟实际运行条件下的腐蚀过程，能够提高飞机结构寿命的预测准确性，从而保障飞机的安全运行和维护。

这项研究对于改进飞机设计、延长使用寿命以及降低维护成本具有重要的实际意义。

关键词：飞机腐蚀；加速腐蚀试验；环境谱；滑轨；腐蚀防护；寿命预测中图分类号：TG172；V216 文献标识码：A 文章编号：1672-9242(2023)12-0128-07DOI：10.7643/issn.1672-9242.2023.12.016×× Environmental Spectra Development for Accelerated Corrosion Testof the Inner cavity of the Aircraft SlideF AN Wei-jie1*, ZHANG Yong1, ZHU Yan-hai2, YANG Wen-fei1, MENG Li-li2, CHU Gui-wen3(1. Qingdao Campus of Naval Aviation University, Shandong Qingdao 266041, China; 2. China Academy of AviationManufacturing Technology, Beijing 100010, China; 3. Shandong University of Science andTechnology, Shandong Qingdao 266590, China)ABSTRACT: The work aims to conduct an accelerated corrosion test for the inner cavity of the×× aircraft slide with complex operating environment, and propose an accelerated corrosion test environment spectrum for Jiangjin area based on the corrosion收稿日期：2023-08-27；修订日期：2023-10-18Received：2023-08-27；Revised：2023-10-18基金项目：国家自然科学基金青年项目（52101392）；山东省青创科技计划（2020KJA014）；山东省自然科学基金青年项目（ZR2020QD081）；山东省自然科学基金面上项目（ZR2020ME130）Fund：The National Natural Science Foundation of China (52101392); Universities of Shandong Province of China (2020KJA014); Shandong Natural Science Foundation (ZR2020QD081); Science and Technology Support Plan for Youth Innovation (ZR2020ME130)引文格式：樊伟杰, 张勇, 朱彦海, 等. ××飞机滑轨内腔的加速腐蚀试验环境谱制定[J]. 装备环境工程, 2023, 20(12): 128-134.FAN Wei-jie, ZHANG Yong, ZHU Yan-hai, et al. ×× Environmental Spectra Development for Accelerated Corrosion Test of the Inner cavity of the Air-craft Slide[J]. Equipment Environmental Engineering, 2023, 20(12): 128-134.第20卷第12期樊伟杰，等：××飞机滑轨内腔的加速腐蚀试验环境谱制定·129·effect of external environment on the inner cavity of the slide, so as to better simulate the corrosion process of the inner cavity of the slide under actual operating conditions. A accelerated corrosion test environment spectrum of the inner cavity of the slide in Jiangjin area was designed based on the reference spectrum of the accelerated corrosion test environment spectrum of the pro-tective coating in the exposed part and the analysis of the corresponding environment. According to the parameter formulation method of reference spectrum and the specific environmental conditions in Jiangjin area, the basis for developing this environ-mental spectrum was designed. Parameters such as humidity and heat, UV exposure, temperature shock, low pressure and salt spray were further determined, and the accelerated corrosion test environment spectrum of the inner cavity of the ××aircraft slide was obtained. A systematic accelerated corrosion test environment spectrum of the inner cavity of the ×× aircraft slide was suc-cessfully formed. Environmental characteristics of Jiangjin area were considered comprehensively, and relevant parameters of the accelerated corrosion test environment spectrum of the exposed protective coating were referred to. By determining parame-ters such as humidity and heat, UV exposure, temperature shock, low pressure and salt spray, the corrosion process of the inner cavity of the slide could be more accurately simulated under actual operating conditions. This environmental spectrum can pro-vide an important reference for aircraft manufacturers and maintenance personnel to evaluate the corrosion of the inner cavity of the slide and take appropriate protective measures. By accurately simulating the corrosion process under actual operating condi-tions, the prediction accuracy of aircraft structural life can be improved, so as to ensure the safe operation and maintenance of aircraft. This research has important practical significance for improving aircraft design, extending service life and reducing maintenance costs.KEY WORDS: ××aircraft corrosion; accelerated corrosion test; environmental spectrum; slide; corrosion protection; life pre-diction随着我国环境的变迁，以及航空装备的发展，××飞机的使用频率逐渐增加，运行环境也逐渐多样化，飞机设备的使用要求也不断提高[1-3]。

2017年第36卷第6期 CHEMICAL INDUSTRY AND ENGINEERING PROGRESS·2051·化 工 进展碳酸氢铵为汲取液正渗透海水淡化研究高婷婷1，解利昕1，徐世昌1，冯丽媛1，杜亚威2，周晓凯1（1天津大学化工学院，天津市膜科学与海水淡化技术重点实验室，天津 300354；2河北工业大学海洋科学与工程学院，海水资源高效利用化工技术教育部工程研究中心，天津 300130）摘要：正渗透技术因低能耗、低膜污染和高回收率等优点逐渐成为膜分离技术的研究热点。

本文以碳酸氢铵溶液为汲取液、0.6mol/L 氯化钠溶液为模拟海水进行了正渗透实验，研究了不同操作条件下正渗透水通量的变化规律和汲取液部分解吸-吸收过程中氨解吸率、氨吸收率以及解吸能耗的变化。

结果表明，提高进料流量和汲取液浓度，正渗透过程水通量增加；提高吸收塔进料流量，氨吸收率增加，操作条件对氨解吸率影响较小；海水淡化正渗透系统能耗主要用于汲取液解吸过程，降低解吸塔进料浓度可以降低解吸过程的能量消耗。

在优化的工艺条件下，正渗透过程水通量为13.6L/(m 2·h)，汲取液回收利用率达到99%，海水淡化产水总溶解固体（TDS ）不高于1000mg/L ，系统吨水耗电量约为195kW·h 。

实验结果对正渗透过程的工业化应用具有指导意义。

关键词：正渗透；脱盐；碳酸氢铵；解吸；吸收中图分类号：P747+.6 文献标志码：A 文章编号：1000–6613（2017）06–2051–06 DOI ：10.16085/j.issn.1000-6613.2017.06.012Study on seawater desalination by ammonium bicarbonate forwardosmosis processGAO Tingting 1，XIE Lixin 1，XU Shichang 1，FENG Liyuan 1，DU Yawei 2，ZHOU Xiaokai 1（1 Tianjin Key Laboratory of Membrane Science and Desalination Technology ，School of Chemical Engineering and Technology ，Tianjin University ，Tianjin 300354，China ；2 Engineering Research Center of Seawater Utilization Technology of Ministry of Education ，School of Marine Science and Engineering ，Hebei University of Technology ，Tianjin 300130，China ）Abstract: Forward osmosis （FO ）is becoming one of the hot spots in the field of membrane technology due to low fouling ，low energy consumption and high water recovery. In the present work ，forward osmosis for seawater desalination was carried out by using ammonium bicarbonate （NH 4HCO 3）solution as draw solution and 0.6mol/L sodium chloride （NaCl ）solution as simulated seawater ，followed by NH 4HCO 3 recovery through partial desorption/absorption. A series of experiments were conducted to investigate the effect of operating conditions on water flux ，ammonia absorption rate ，ammonia desorption rate and specific energy consumption. The results indicated that the water flux of FO system increased with increasing draw solution concentration ，flowrate of draw solution or feed solution. Ammonia absorption rate of the absorption column increased with the increase of draw solution flowrate. The operating conditions had little influence on the ammonia desorption rate in the desorption column. In addition ，the energy consumption of FO desalination system was mainly utilized第一作者：高婷婷（1991—），女，硕士研究生，研究方向为化学工程。

大连理工大学硕士学位论文苯乙烯氧化反应制苯甲醛的研究姓名：马云云申请学位级别：硕士专业：工业催化指导教师：刘靖20060601大连理工大学硕士学位论文格式规范进行的，第二步Ｃｕ（ＯＨ）２脱水生成ＣｕＯ是一个吸热过程，晶化的温度不宜过低否则难以得到理想的样品，也没必要采用高温以免浪费能耗，可降低生产成本，因此可将晶化温度选定为８０℃。

图３．２Ｃ１，－，Ｃ８号ＣｕＯ样品的放大１０，０００倍的扫描电镜图片（ａ—Ｃ１；ｂ－Ｃ２；ｃ－Ｃ３；ｄ—Ｃ４；ｅ—Ｃ５；ｆ－Ｃ６；ｇ—Ｃ７；ｈ－Ｃ８）ＳＥＭｏｆＣｕＯｓａｍｐｌｅＣ１－－，Ｃ８ｏｎ１０，０００ｔｉｍｅｓＦｉｇ．３．２（ａ－Ｃ１；ｂ－Ｃ２；ｃ－Ｃ３；ｄ－Ｃ４；ｅ－Ｃ５；ｆ－Ｃ６；ｇ－Ｃ７；ｈ－Ｃ８）大连理工大学硕士学位论文相同配比时，在１００＂０晶化ｌｈ同晶化３ｈ相比，样品形貌变化不大，但有倾向于团聚的趋势，因此晶化的时间不宜过长，可将晶化时间选定为ｌｈ。

其它合成条件相同，将碱量减半得到的样品仍呈片状但却有轻微的团聚，且尺寸分布不均，生成ＣｕＯ的反应分为两步：Ｃｕ（Ｎ０３）２＋２ＮａＯＨ一２ＮａＮ０３＋Ｃｕ（ＯＨ）２（１）Ｃｕ（ＯＨ）２ｃｓ）＋２０Ｈ。

｛Ｂｑ）－－［Ｃｕ（ＯＨ），］。

（ａｍ—ＣｕＯ（ｓ）＋２０ＩＴ（ａｑ）＋Ｈ２０（２）首先按化学方程式（１）生成Ｃｕ（ＯＨ）２，它能溶解于过量浓碱溶液中，形成深蓝色的四羟基合铜（ＩＩ）离子的溶胶，在一定条件下脱水后最终得到ＣｕＯ晶体。

因此适宜的铜盐，碱（ｍｏｌｒａｔｉｏ）取为１：４，更易于达到溶液的过饱和状态。

通过对比ｃ２４（ｂ）样品与Ｃ８４（ｈ）样品的电镜表征结果，发现其他合成条件相同，增大水量对样品形貌的影响甚微，得到的样品都呈片状，分散均匀，几乎未团聚，但ｃ８比ｃ２略长。

这可能是由于溶液浓度偏高时，沉淀形成快，表面化学反应在极短的时间内进行，可以减弱由表面反应控制的生长而使颗粒的生长受扩散过程控制。

这将使晶核大量快速形成，晶体的多向生长速率差异降低，得到长度较短的薄片。