• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Effect of Sludge Retention Time on the Fate of Proteins and Polysaccharides in AAO Process

    2015-08-11 14:00:37DUYongli杜勇立HUANGManhong黃滿紅ZHENGYu

    DU Yong-li(杜勇立),HUANG Man-h(huán)ong(黃滿紅),ZHENG Yu(鄭 宇)

    1 School of Civil and Architectural Engineering,Central South University,Changsha 410075,China

    2 Hunan Provincial Communications Planning,Survey&Design Institute,Changsha 410008,China

    3 School of Environmental Science and Engineering,Donghua University,Shanghai 201620,China

    Effect of Sludge Retention Time on the Fate of Proteins and Polysaccharides in AAO Process

    DU Yong-li(杜勇立)1,2,HUANG Man-h(huán)ong(黃滿紅)3*,ZHENG Yu(鄭 宇)3

    1 School of Civil and Architectural Engineering,Central South University,Changsha 410075,China

    2 Hunan Provincial Communications Planning,Survey&Design Institute,Changsha 410008,China

    3 School of Environmental Science and Engineering,Donghua University,Shanghai 201620,China

    Effect of sludge retention time(SRT)on the removal of potentialand polysaccharides in an anaerobic/anoxic/aerobic (AAO)process was investigated.The Lowry method and anthrone method were used to detect proteins and polysaccharides.Total removal efficiency of proteins at SRT of 10 to 25 d in the AAO system was higher than 90%.Polysaccharides removal efficiencies were above 80%when SRT was increased from 15 to 25 d,whereas only 81%of polysaccharides was removed at SRT of 10 d.The biodegradation part of proteins and polysaccharides increased from 87.40%to 93%and from 74.22%to 86.94%with increasing SRTs.The ratios of polysaccharides and proteins in extracellular polymer substances(EPSs)were around 1.5-3 in different SRTs.As SRT increasing,polysaccharides and proteins discharged with residual sludge decreased gradually.The amount of EPSs decreased with increasing SRTs.

    protein;polysaccharide;sludge retention time(SRT); anaerobic/anoxic/aerobic (AAO) system; extracellular polymer substances(EPSs)

    Introduction

    Organic matters (OMs) in wastewater are highly heterogeneous,containing substances of various origins[1].Some studies had reported that major chemical fractions in municipal wastewater were proteins and polysaccharides.For instance,the fractions of total proteins and polysaccharides of total chemical oxygen demand(COD)in several catchments areas of Denmark were,on average,28% and 18%[2].Narkis et al.identified soluble organics in a physical-chemical wastewater treatment plant in Israel,revealing that 30%of the total COD was proteins,10% of the total COD was polysaccharides in the influent[3].Though proteins and polysaccharides can comprise a significant portion of organic carbon in wastewater,limited information is available on how these compounds are removed in biological wastewater treatment systems[4-5].

    Anaerobic/anoxic/aerobic(AAO)process for nitrogen and phosphorus removal is widely implemented. Operational parameters,such as sludge retention time(SRT)and internal recycle ratio,have been optimized[6-10].But it is not clear how these operational parameters affect on the fate of proteins and polysaccharides in the wastewater treatment system.Previous studies found thatseveralremovalwaysofproteinsand polysaccharides in wastewater treatment systems:biodegradation or metabolism and adsorption to sludge[11-12].Adsorption is one of the sources of extracellular polymer substances(EPSs),while proteins and polysaccharides in EPSs are postulated to play an important role in flocculation and dewatering[13-15].Thus it is important to quantify the proteins and polysaccharides in the EPS in order to understand the origins of EPSs and the adsorptions of proteins and polysaccharides.

    In this study,the removal characteristics of proteins and polysaccharides in an AAO lab-scale process at different SRTs are presented.Then,the amount of proteins and polysaccharides in the EPS was determined to investigate the fate of proteins and polysaccharides in wastewater.Finally,fate of proteins and polysaccharides in the wastewatertreatmentprocesswere evaluated by mass balance.

    1 Materials and Methods

    1.1 Experimental equipments

    The lab-scale AAO system used in this study consisted of an anaerobic tank(7 L),an anoxic tank(7 L),an aerobic tank (21 L) and a clarifier.These tanks were all made of polyethylene glass.The activated sludge was obtained from a full-scale anoxic-aerobic activated sludge plant treating the local domestic and industrial wastewater in Shanghai,China.The electric stirrers were employed in anaerobic and anoxic tanks.The peristaltic pumps were used to feed the system automatically,recycle the sludge from the bottom of clarifier to the anaerobic tank,and transfer the mixed liquor from the aerobic tank to the anoxic tank.The whole system had been operated for more than two months continuously in a laboratory with the temperature controlled at 25℃.During the experiment,dissolved oxygen (DO)in anaerobic,anoxic and aerobic reactors was in the range of 0-0.3,0-0.5 and 3.3-5.7 mg·L-1,respectively.pH was about 6.5-7.5.

    According to the recommending value of AAO operational parameters[16],the hydraulic retention time(HRT)of the above three reactors was set to 1.6,1.6 and 4.8 h,respectively.The sludge was returned from the bottom of the settling reactor to the anaerobic reactor.The mixed liquor was recycled from the aerobic reactor to the anoxic reactor.The circulation ratio for both the sludge and mixed liquor was 1.The whole system was placed in a temperature-controlled room at 25℃.Low nitrogen removal efficiencies have been found in wastewater treatment plants operating SRTs lower than 10 d[17-18].So in this paper the SRT was changed from 10 d to 25 d,aiming to assess the effect ofSRT variations on the performance ofproteins and polysaccharides removal in AAO system.

    1.2 Wastewater characteristics

    Real domestic wastewater was taken from the wastewater collection station of a large residential area in Shanghai,China.During the experimental period,the fresh wastewater was introduced into feed tank every 4 h,and the total COD,soluble COD(through 0.45 μm filter membrane),total organic carbon (TOC)and total nitrogen(TN)of the wastewater are 204-440,108-372,40-138 and 50-70 mg·L-1,respectively.

    1.3 Analyses of proteins and polysaccharides

    The Lowry method was applied for protein determination.Albumin bovine was used as the standard reagent.The method is described by Raunkj?r et al[19].The absorbance was detected at 750 nm.

    The anthrone method was applied for polysaccharides determination.A modification of the method described by Raunkj?r et al.[19]was used and glucose was used as the standard reagent.Samples were placed in a water bath at 100℃for 10 min and then cooled in a water bath at 4℃ for 5 min.Absorbance at 625 nm was measured.

    1.4 Extraction and amount of EPS

    The system was operated in steady state by acquiring a steady COD removal efficiency.EPSs are the compounds excreted from bacterial metabolism or lysis,or the compounds adsorbed from the wastewater.Two parts were included in EPS: loosely bound biopolymers (LBB) and tightly bound biopolymer(TBB)[20].

    The extraction procedures of LBB are listed as follows.Sludge sample(900 mL)were centrifuged at 6000 r/min at 4℃ for 15 min.Then,the supernatant was discarded and the pellets were transferred to 15 mL 0.85%(m/v)NaCl solution.Several beadings were added to the solution.Then it was stirred in the ultrasonic instrument for 2 min and the suspension was stirred for 10 min at 150 r·min-1.At the end of the stirring period,the suspension was stirred in the ultrasonic instrument for 2 min,and then centrifuged at 8000 r/min at 4℃ for 10 min.The supernatant was collected for analysis.

    After the above pre-treating procedures,the supernatant was discarded and the pellets were transferred to an extraction beaker for determining TBB.A buffer solution at pH 7.0(2.0 mmol·L-1NaH2PO4,1.26 mmol·L-1Na2HPO4,2.5 mmol·L-1NaCl,and 0.5 mmol·L-1KCl)was added to give a final volume of 300 mL 70 g·g-1volatile suspended solids(VSS).Dowex sodium form cation exchange resin was added to the extraction beaker[21].The suspension was stirred at 150 r·min-1for 5 h.At the end of the stirring period,the suspension was centrifuged at 5000 r·min-1at 4℃ for 15 min.The supernatant was collected for analyzing.

    1.5 Other analytical methods

    TOC wasdetermined using a Shimadzu TOC-Vcpn analyzer.COD,total suspended solid(TSS),VSS,mixed liquor suspended solid(MLSS),TN,and total phosphorus (TP)measurements were carried out following APHA standard methods[22].

    1.6 Calculations

    The mass balance calculation was based on Fig.1.Proteins and polysaccharides concentrations in anaerobic,anoxic,and aerobic reactors were calculated according to Eqs.(1)-(3):

    The overall removal efficiency(ORE)of proteins and polysaccharides for the AAO system was calculated according to Eq.(4).

    The totalpercentage ofproteinsand polysaccharides removed from the influent was obtained by summing the percentage of proteins and polysaccharides removed by the anaerobic, anoxic, aerobic and settling reactors. These percentages were calculated using Eq.(5)-(8),respectively:

    In the above equations,ARis the anaerobic removal;AnRis the anoxic removal;AeRis the aerobic removal;SR is the settling removal;Ciis the proteins and polysaccharides concentration in influent,mg·L-1;C1,C2,C3,and Ceare the proteins and polysaccharides concentrations in the effluents from anaerobic,anoxic,aerobic,settling reactors,respectively,mg·L-1;Ce1is the proteins and polysaccharides concentration in the return sludge,mg·L-1;Ci1,Ci2,and Ci3are the proteins and polysaccharides concentrations in mixed liquors in the anaerobic,anoxic,aerobic reactors,respectively,mg·L-1;Q and Qware the influent flow rate(60 mg·d-1) and the waste sludge flow rate,respectively;R and r are the recirculation ratios for activated sludge and mixed liquor,respectively.

    Fig.1 Flow chart of the AAO activated sludge system for mass balance calculation

    2 Results and Discussion

    2.1 Effect of SRT on the removal and fate of the proteins and polysaccharide

    In the conditions of differentSRTs, proteins and polysaccharides removal efficiency in each stage of AAO system was shown in Fig.2.

    From Fig.2,it could be concluded that proteins removal efficiency in AAO system was around 80%-90%,only little proteins discharged with the final effluent.It was particularly evident that the proteins removal efficiency had been improved only a little with SRT increasing from 10 d to 25 d.Polysaccharides removal efficiency in AAO system was exceeds 80%,and the change of SRT had some influence on the total remove efficiency.When SRT was equal to 10 d,thepolysaccharides removal efficiency was 81.85%,which was the lowest in all SRT conditions.

    Fig.2 Removal percentages of the whole process in different SRTs

    Fig.3 Removal percentages of each tank account for the total removal quantity

    In the condition of different SRTs,the amount of proteins removed in anaerobic tank was larger than that of aerobic tank and anoxic tank(as shown in Fig.3).The quantity of proteins removed in anaerobic tank exceeded 40.0%of total removed quantity in AAO system,and it got larger with the longer SRT.Maybe it was due to that proteins could be hydrolyzed to volatile fatty acids in anaerobic condition.

    In the condition ofdifferentSRT,the quantity of polysaccharides removed in anaerobic tank was nearly equal to that of aerobic tank,accounting for about 40.0% of total removed quantity.The removal ratios hadn't varied much with SRT changing.

    2.2 Composition and changes of proteins and polysaccharides in EPS of each tank of AAO system

    The average organic carbon concentrations of EPS in the different conditions,which were the sum of TB and LB,were shown in Fig.4.

    Fig.4 EPS concentration of each tank of AAO system

    Data presented in Fig.4 showed that,in the activated sludge of each reactor,the weight ratio of organic carbon in EPS to volatile suspended solids(VSS)was between 38 and 71 mg·g-1VSS,which agreed with the finding of Benetti[23].The increase in SRT also affected the quantity of EPS.From Fig.3,the amount of EPS in the period of SRT at 10 d was higher than other periods.It appeared that the change of SRT led to the variety of bacterial metabolism or lysis in the system,which was excreted compound to form part of EPS.

    Table 1 Concentrations of proteins and polysaccharides in LB and TB

    Table 1 presented the concentrations of proteins and polysaccharides in LB and TB.Data from Table 1 indicated that amount of polysaccharides and proteins in EPS of anaerobic sludge was higher than that of the aerobic sludge or the anoxic sludge.Protein was the major EPS compound,constituting approximately 50% ofthe organic fraction.Meanwhile,polysaccharides constituted only approximately 10% of the whole EPS.From Table 1,it could also be concluded that LB concentrations decreased as the SRT was increasing and the amount of polysaccharides and proteins in EPS at SRT of 10 d was higher than other periods.

    Fig.5 Proteins/polysaccharide of different SRTs

    Figure 5 gave the ratios of proteins and polysaccharides under different SRTs. The mass ratio of protein to polysaccharide in EPS was around 1.5-3 and it was similar to those obtained by other studies[24-25].From this figure,it could be concluded that the ratios of proteins and polysaccharides tended to increase when the SRT was increased.

    2.3 Mass balance of proteins and polysaccharides in AAO system

    As proteins and polysaccharides are not volatile compounds,it is assumed that their removals are due to biodegradation and sorption in the activated sludge process.Therefore,the possible fates of proteins and polysaccharides in the AAO system include discharging with final effluent and the waste sludge,accumulating in the system and being degraded by microorganisms in the activated sludge.The fates of proteins and polysaccharides were calculated based on the following mass balance:

    where Mi,Mo,and Mware the proteins and polysaccharidesmasses in the inlet sewage,final effluent,and waste sludge.Mbis the proteins and polysaccharides mass degraded by the AAO activated sludge,and Mais the proteins and polysaccharides mass accumulating in the system.They are calculated according to Eq.(10)-(14):

    where V1=3.5 L,V2=3.5 L,V3=10.5 L,and V4=3.5 L are volumes of mixed liquor in the anaerobic,anoxic,aerobic and settling reactor,respectively.

    The amounts of proteins and polysaccharides in different removal ways and their contribution to total removal quantity in this research were listed in Fig.6.

    Fig.6 Fates of proteins and polysaccharides in AAO system

    As shown in Fig.6,when SRT changed from 10 d to 25 d,biodegradation was the main way for removal.The percentage of proteins removed in this way ranged from 87.4%to 93.0%.The percentage of polysaccharides in this way changed from 74.2%to 86.9%.After entering AAO system,the possible removalways of proteins and polysaccharides included discharging with finaleffluent,discharging with residual sludge,accumulating in system,and biodegradation.As SRT increasing,the contribution of the way discharging with residual sludge decreased gradually.Biodegradation at SRT of 10 d was the least of the four SRTs while discharging with final effluent at SRT of 10 d was the highest.

    3 Conclusions

    Theexperimentalstudy was made by using actual municipal wastewater as the inflow raw water to evaluate the performanceofAAO processin removing proteinsand polysaccharides.The conclusions can be summarized as follows.

    (1)Proteins removal efficiency in AAO system was around 80%-90%,while that of polysaccharides exceeded 90% in the conditions of different SRTs.

    (2)The quantity of proteins and polysaccharides removed in anaerobic tank were more than 40%of total removed quantity in AAO system.So anaerobic tank played an important role in removing proteins and polysaccharides.

    (3)The amount of EPS in the condition of SRT at 10 d washigher than otherconditions. The mass ratios of polysaccharides to proteins in EPSs were around 1.5-3.

    (4) Biodegradation was the main way for removing polysaccharides and proteins in AAO wastewater treatment system at SRT of 10 to 25 d.

    [1]Henze M.Characterization ofWastewaterforModeling of Activated-Sludge Processes[J].Water Science&Technology,1992,25(6):1-15.

    [2]Sophonsiri C,Morgenroth E.Chemical Composition Associated with Different Particle Size Fractions in Municipal,Industrial,and Agricultural Wastewaters[J].Chemosphere,2004,55(5):691-703.

    [3]Narkis N,Henefeld-Fourrier S,Rebhun M.Volatile Organic Acids in Raw Wastewater and in Physico-Chemical Treatment[J].Water Research,1980,14(9):1215-1223.

    [4]Chitapornpan S,Chiemchaisri C,Chiemchaisri W,et al.Organic Carbon Recovery and Photosynthetic Bacteria Population in an Anaerobic Membrane Photo-Bioreactor Treating Food Processing Wastewater[J].Bioresource Technology,2013,141(8):65-74.

    [5]Wilén B M,Jin B,Lant P.The Influence of Key Chemical Constituents in Activated Sludge on Surface and Flocculating Properties[J].Water Research,2003,37(9):2127-2139.

    [6]Qi R,Yu T,Li Z,et al.Comparison of Conventional and Inverted A2/O Processes: PhosphorusRelease and Uptake Behaviors[J].Journal of Environmental Sciences,2012,24(4): 571-578.

    [7]Kim H S,Kim Y J,Cheon S P,et al.Evaluation of Model-Based Control Strategy Based on Generated Setpoint Schedules for NH4-N Removal in a Pilot-Scale A2/O Process[J].Chemical Engineering Journal,2012,203(9):387-397.

    [8]Kim H S,Moon T S,Kim Y J,et al.Evaluation of Rule-Based Control Strategies according to Process State Diagnosis in A2/O Process[J].Chemical Engineering Journal,2013,222(4): 391-400.

    [9]Baeza J A,Gabriel D,Lafuente J.Effect of Internal Recycle on the Nitrogen Removal Efficiency of an Anaerobic/Anoxic/Oxic (A2O)Wastewater Treatment Plant(WWTP)[J].Process Biochemistry,2004,39(11):1615-1624.

    [10] Park C,Navak J T.Characterization of Activated Sludge Exocellular Polymers Using Several Cation-Associated Extraction Methods[J].Water Research,2007,41(8):1679-1688.

    [11]Larsen T A,Harremo?s P.Degradation Mechanisms of Colloidal Organic Matter in Biofilm Reactor[J].Water Research,1994,28(6):1443-1452.

    [12]Zhang L L,F(xiàn)eng X X,Zhu N W,et al.Role of Extracellular Protein in the Formation and Stability of Aerobic Granules[J].Enzyme and Microbial Technology,2007,41(5):551-557.

    [13] Zuriaga-Agustí E,Bes-Piá A,Mendoza-Roca J A,et al.Influence of Extraction Methods on Proteins and Carbohydrates Analysis from MBR Activated Sludge Flocs in View of Improving EPS Determination[J].Separation and Purification Technology,2013,112(7):1-10.

    [14]Laspidou C S,Rittmann B E.A Unified Theory for Extracellular Polymeric Substances,Soluble Microbial Products,and Active and Inert Biomass[J].Water Research,2002,36(11):2711-2720.

    [15]Sponza D T.Investigation of Extracellular Polymer Substances (EPS)and Physicochemical Properties of Different Activated Sludge Flocs under Steady-State Conditions[J].Enzyme and Microbial Technology,2003,32(3/4):375-385.

    [16]Tchobanoglous G,Burton F L,Metcalf and Eddy Inc.,et al.Wastewater Engineering:Treatment and Reuse[M].4th ed.New York:McGraw-Hill Press,2003:1633-1676.

    [17]Pai T Y,Wan T J,Tsai Y P,et al.Effect of Sludge Retention Time on Nitrifiers'Biomass and Kinetics in an Anaerobic/Oxic Process[J].Clean-Soil,Air,Water,2010,38(2):167-172.

    [18]Clara N,Kreuzinger N,Strenn B,et al.The Solids Retention Time—a Suitable Design Parameter to Evaluate the Capacity ofWastewater Treatment Plants to Remove Micropollutants[J].Water Research,2005,39(1):97-106.

    [19]Raunkj?r K,Hvitved-Jacobsen T,Nielsen P H.Measurement of Pools of Protein,Carbohydrate and Lipid in Domestic Wastewater[J].Water Research,1994,28(2):251-262.

    [20] Comte S,Guibaud G,Baudu M.Biosorption Properties of ExtracellularPolymeric Substances (EPS) Resulting from Activated Sludge according to Their Type:Soluble or Bound[J].Process Biochemistry,2006,41(4):815-823.

    [21]American Public Health Association(APHA),American Water Works Association,AWWA,Water Environment Federation (WEF).Standard Methods for the Examination of Water and Wastewater[S].20th ed.Washington DC,American Public Health Association,1998:536-538.

    [22]Liu P C,Huang M H,Chen D H,et al.Effect of HRT on Fate of Typical Polycyclic Musk by A2O Process[J].Environment Science,2013,34(8):2735-2740.(in Chinese)

    [23] Benetti A D.Composition,F(xiàn)ate,andTransformationof Extracellular Polymers in Wastewaterand SludgeTreatment Processes[D].USA:Cornell University,2000.

    [24]Frφlund B,Griebe T,Nielsen P H.Enzymatic Activity in the Activated Sludge Floc Matrix[J]. Applied Microbiology Biotechnology,1995,43(4):755-761.

    [25]Bhatia D,Bourven I,Simon S,et al.Fluorescence Detection to Determine Proteins and Humic-like Substances Fingerprints of Exopolymeric Substances (EPS) from BiologicalSludges Performed by Size Exclusion Chromatography(SEC) [J].Bioresource Technology,2013,131(3):159-165.

    X703.1

    A

    1672-5220(2015)03-0401-05

    date:2013-11-01

    s:National Natural Science Foundations of China(Nos.21477018,21007010);Hunan Province Ministry of Transportation Scientific Research Projects,China(Nos.200908,201105);Ministry of Transport Science and Technology Program,China(No.2010353343290)

    *Correspondence should be addressed to HUANG Man-h(huán)ong,E-mail:egghmh@163.com

    免费女性裸体啪啪无遮挡网站| 亚洲成色77777| 亚洲成色77777| 哪个播放器可以免费观看大片| 亚洲一区二区三区欧美精品| 亚洲av福利一区| 最近最新中文字幕免费大全7| 国产国拍精品亚洲av在线观看| 亚洲av电影在线观看一区二区三区| 婷婷色综合www| 久久久精品区二区三区| 另类亚洲欧美激情| 亚洲av国产av综合av卡| 男女国产视频网站| 五月天丁香电影| 亚洲精品国产av蜜桃| 成人午夜精彩视频在线观看| 国产精品 国内视频| 女人精品久久久久毛片| 亚洲精品国产av成人精品| 天天躁夜夜躁狠狠躁躁| 黄色一级大片看看| 精品国产乱码久久久久久小说| 丰满乱子伦码专区| 免费黄色在线免费观看| 国产成人午夜福利电影在线观看| 伊人亚洲综合成人网| 亚洲国产精品专区欧美| 美国免费a级毛片| 自线自在国产av| 国产在线视频一区二区| 最黄视频免费看| 在线观看国产h片| 国产精品久久久久久精品电影小说| 国产色爽女视频免费观看| 久久国产精品大桥未久av| 最黄视频免费看| 精品少妇久久久久久888优播| 少妇人妻精品综合一区二区| 国产不卡av网站在线观看| 精品人妻偷拍中文字幕| 国产精品免费大片| 下体分泌物呈黄色| 人妻 亚洲 视频| 纵有疾风起免费观看全集完整版| 午夜久久久在线观看| 热99国产精品久久久久久7| 国产亚洲精品第一综合不卡 | 国产激情久久老熟女| 99久国产av精品国产电影| 乱码一卡2卡4卡精品| 波野结衣二区三区在线| 日本vs欧美在线观看视频| 久久韩国三级中文字幕| 亚洲少妇的诱惑av| 欧美日韩一区二区视频在线观看视频在线| 亚洲国产欧美在线一区| 国产 精品1| 午夜免费观看性视频| 国产福利在线免费观看视频| 国产精品欧美亚洲77777| 五月天丁香电影| 成人综合一区亚洲| 这个男人来自地球电影免费观看 | 女人精品久久久久毛片| 在线 av 中文字幕| 日韩在线高清观看一区二区三区| 男男h啪啪无遮挡| xxxhd国产人妻xxx| 热re99久久国产66热| 亚洲精品日本国产第一区| 亚洲精品成人av观看孕妇| 女人被躁到高潮嗷嗷叫费观| 极品少妇高潮喷水抽搐| 免费少妇av软件| 国产精品不卡视频一区二区| 少妇高潮的动态图| 纵有疾风起免费观看全集完整版| 欧美日韩视频精品一区| 大片电影免费在线观看免费| 一二三四中文在线观看免费高清| 亚洲欧美中文字幕日韩二区| 韩国精品一区二区三区 | 黄片播放在线免费| 欧美成人精品欧美一级黄| 国产在线免费精品| 十分钟在线观看高清视频www| av电影中文网址| 免费黄频网站在线观看国产| 欧美精品人与动牲交sv欧美| 国产精品女同一区二区软件| 亚洲av综合色区一区| 天天影视国产精品| 人妻一区二区av| 99国产精品免费福利视频| 99视频精品全部免费 在线| 亚洲精品一区蜜桃| 亚洲成人手机| 精品一区二区三区视频在线| 欧美丝袜亚洲另类| 国产不卡av网站在线观看| 男的添女的下面高潮视频| 国产国拍精品亚洲av在线观看| 国产亚洲精品久久久com| 亚洲美女搞黄在线观看| 18禁国产床啪视频网站| 人成视频在线观看免费观看| 极品人妻少妇av视频| 黑人猛操日本美女一级片| 9191精品国产免费久久| 高清欧美精品videossex| 黑人猛操日本美女一级片| 久久影院123| 国产老妇伦熟女老妇高清| 国产精品国产三级国产专区5o| 又黄又粗又硬又大视频| 亚洲精品aⅴ在线观看| 国产精品国产三级专区第一集| 日韩不卡一区二区三区视频在线| 七月丁香在线播放| 草草在线视频免费看| 永久免费av网站大全| 高清黄色对白视频在线免费看| 美女脱内裤让男人舔精品视频| 极品少妇高潮喷水抽搐| 国产xxxxx性猛交| 午夜福利视频在线观看免费| 90打野战视频偷拍视频| 国产黄频视频在线观看| 免费av中文字幕在线| 在现免费观看毛片| 丁香六月天网| 亚洲国产日韩一区二区| 亚洲精品日韩在线中文字幕| 亚洲欧洲日产国产| 国产 精品1| 久久精品熟女亚洲av麻豆精品| 精品国产露脸久久av麻豆| 一级毛片黄色毛片免费观看视频| 黄片无遮挡物在线观看| 国产成人免费观看mmmm| 一级毛片 在线播放| 亚洲精品色激情综合| 欧美精品av麻豆av| 日本av手机在线免费观看| 啦啦啦在线观看免费高清www| 中文字幕最新亚洲高清| av国产精品久久久久影院| 欧美 亚洲 国产 日韩一| 人妻少妇偷人精品九色| 国产69精品久久久久777片| 成年av动漫网址| 久久这里有精品视频免费| 久久久精品免费免费高清| 人妻一区二区av| 人体艺术视频欧美日本| 伊人亚洲综合成人网| 99热网站在线观看| 日本爱情动作片www.在线观看| 男人爽女人下面视频在线观看| 我的女老师完整版在线观看| 国产免费视频播放在线视频| 久久久久久人妻| 十八禁网站网址无遮挡| 日韩一本色道免费dvd| 大片电影免费在线观看免费| av不卡在线播放| 韩国高清视频一区二区三区| 在线观看三级黄色| 综合色丁香网| 久久韩国三级中文字幕| 好男人视频免费观看在线| 999精品在线视频| 亚洲成av片中文字幕在线观看 | 午夜影院在线不卡| 午夜福利网站1000一区二区三区| 国产一区亚洲一区在线观看| 美女大奶头黄色视频| 午夜激情久久久久久久| 国产精品99久久99久久久不卡 | 亚洲欧洲国产日韩| 欧美少妇被猛烈插入视频| 精品午夜福利在线看| videosex国产| 永久免费av网站大全| 婷婷色综合大香蕉| 最近最新中文字幕免费大全7| 亚洲四区av| 免费黄频网站在线观看国产| 午夜福利网站1000一区二区三区| 亚洲欧洲精品一区二区精品久久久 | 国产男人的电影天堂91| 亚洲欧美一区二区三区国产| 涩涩av久久男人的天堂| 亚洲欧美成人精品一区二区| 免费观看在线日韩| 18在线观看网站| 日本午夜av视频| 男女国产视频网站| 亚洲内射少妇av| 亚洲国产色片| 青春草国产在线视频| 国产高清三级在线| 成人亚洲欧美一区二区av| 午夜av观看不卡| 国产精品欧美亚洲77777| 高清欧美精品videossex| 日韩精品有码人妻一区| 一本—道久久a久久精品蜜桃钙片| 美女xxoo啪啪120秒动态图| 毛片一级片免费看久久久久| 亚洲精品成人av观看孕妇| 国产一区有黄有色的免费视频| 99热这里只有是精品在线观看| 纯流量卡能插随身wifi吗| 丝袜喷水一区| 欧美激情 高清一区二区三区| 男人操女人黄网站| av卡一久久| 国产日韩欧美在线精品| 永久免费av网站大全| 成人影院久久| 久久99热6这里只有精品| 80岁老熟妇乱子伦牲交| 日本黄大片高清| 国产国语露脸激情在线看| 国产男女内射视频| 久久久久精品性色| 一个人免费看片子| 肉色欧美久久久久久久蜜桃| 寂寞人妻少妇视频99o| 国产精品人妻久久久影院| 亚洲内射少妇av| 在线观看美女被高潮喷水网站| 一区二区三区四区激情视频| 大香蕉97超碰在线| 国语对白做爰xxxⅹ性视频网站| 亚洲精品aⅴ在线观看| 亚洲av男天堂| 婷婷色综合www| 亚洲人成网站在线观看播放| 两性夫妻黄色片 | 一级黄片播放器| 久热这里只有精品99| 制服诱惑二区| 中文字幕av电影在线播放| 蜜桃国产av成人99| 久久亚洲国产成人精品v| a级毛片在线看网站| 99久久中文字幕三级久久日本| a级毛片在线看网站| 亚洲av电影在线进入| 国产精品久久久久久久电影| 午夜日本视频在线| 观看av在线不卡| 美女内射精品一级片tv| 一区二区日韩欧美中文字幕 | 99热国产这里只有精品6| 日日摸夜夜添夜夜爱| 国产精品一二三区在线看| 精品视频人人做人人爽| 国产免费现黄频在线看| 亚洲一区二区三区欧美精品| 天天躁夜夜躁狠狠久久av| 自拍欧美九色日韩亚洲蝌蚪91| 国产老妇伦熟女老妇高清| 日韩欧美一区视频在线观看| freevideosex欧美| 少妇的丰满在线观看| 美女福利国产在线| 大片免费播放器 马上看| 最黄视频免费看| 亚洲精品久久午夜乱码| 欧美成人午夜免费资源| 全区人妻精品视频| 国产一区二区在线观看av| 高清不卡的av网站| 自线自在国产av| 十八禁网站网址无遮挡| 欧美亚洲 丝袜 人妻 在线| 国产国拍精品亚洲av在线观看| 成人无遮挡网站| 丝袜脚勾引网站| 久热这里只有精品99| 成人手机av| 国精品久久久久久国模美| 日日啪夜夜爽| 狠狠婷婷综合久久久久久88av| 寂寞人妻少妇视频99o| 欧美日韩精品成人综合77777| 黄色怎么调成土黄色| 国产精品蜜桃在线观看| 色94色欧美一区二区| 日韩av免费高清视频| 在线 av 中文字幕| 国产精品麻豆人妻色哟哟久久| 亚洲欧美精品自产自拍| 国产高清国产精品国产三级| 久久人人爽人人片av| 精品人妻熟女毛片av久久网站| 午夜日本视频在线| 两个人看的免费小视频| 久久久久久久大尺度免费视频| 亚洲中文av在线| 亚洲国产av新网站| 韩国av在线不卡| 欧美激情国产日韩精品一区| 国产精品国产三级专区第一集| 亚洲内射少妇av| 老司机影院成人| 成人午夜精彩视频在线观看| 久久免费观看电影| 91在线精品国自产拍蜜月| 欧美日韩亚洲高清精品| 久久国产精品男人的天堂亚洲 | 久久狼人影院| 看十八女毛片水多多多| 色婷婷av一区二区三区视频| 18禁在线无遮挡免费观看视频| 亚洲丝袜综合中文字幕| av在线观看视频网站免费| 国产综合精华液| 三上悠亚av全集在线观看| 九九在线视频观看精品| 色婷婷av一区二区三区视频| 国产亚洲精品久久久com| 久久久欧美国产精品| 国产欧美日韩综合在线一区二区| 免费日韩欧美在线观看| 捣出白浆h1v1| 一区二区av电影网| 精品久久久精品久久久| 丰满饥渴人妻一区二区三| 国产日韩一区二区三区精品不卡| 国产精品嫩草影院av在线观看| 一个人免费看片子| 亚洲精品aⅴ在线观看| 欧美精品av麻豆av| 久久久久久久大尺度免费视频| 在线精品无人区一区二区三| 午夜av观看不卡| 18禁在线无遮挡免费观看视频| 99久久精品国产国产毛片| 欧美日韩视频高清一区二区三区二| 国产日韩欧美视频二区| 99精国产麻豆久久婷婷| 久久久精品94久久精品| 精品99又大又爽又粗少妇毛片| 国产av精品麻豆| 青青草视频在线视频观看| av在线老鸭窝| 蜜臀久久99精品久久宅男| 嫩草影院入口| 日韩精品免费视频一区二区三区 | av片东京热男人的天堂| 少妇熟女欧美另类| 人人妻人人爽人人添夜夜欢视频| 亚洲色图 男人天堂 中文字幕 | 久久人人爽人人片av| 亚洲成av片中文字幕在线观看 | 伦理电影大哥的女人| xxx大片免费视频| 人妻系列 视频| 国产精品人妻久久久久久| 精品国产乱码久久久久久小说| 国产精品久久久久久av不卡| 一边摸一边做爽爽视频免费| 午夜久久久在线观看| 国语对白做爰xxxⅹ性视频网站| 中国美白少妇内射xxxbb| 色吧在线观看| 国产精品一二三区在线看| 亚洲av电影在线进入| 亚洲av福利一区| 青春草国产在线视频| 制服丝袜香蕉在线| 热re99久久国产66热| 欧美变态另类bdsm刘玥| 男人操女人黄网站| 中文字幕精品免费在线观看视频 | 美女国产视频在线观看| 人妻系列 视频| 人体艺术视频欧美日本| 国产国拍精品亚洲av在线观看| 三级国产精品片| 国产探花极品一区二区| 两性夫妻黄色片 | 精品一区二区三区视频在线| 乱码一卡2卡4卡精品| 母亲3免费完整高清在线观看 | 伦精品一区二区三区| 亚洲av综合色区一区| 欧美激情极品国产一区二区三区 | 中文字幕精品免费在线观看视频 | 欧美精品av麻豆av| 老熟女久久久| 亚洲激情五月婷婷啪啪| 啦啦啦中文免费视频观看日本| 新久久久久国产一级毛片| 男女免费视频国产| 最近中文字幕高清免费大全6| 内地一区二区视频在线| 国产黄色免费在线视频| 久久国内精品自在自线图片| a级片在线免费高清观看视频| 国产成人免费观看mmmm| 9热在线视频观看99| 亚洲久久久国产精品| 一本色道久久久久久精品综合| 久久人人爽人人片av| 久久人妻熟女aⅴ| 欧美日韩精品成人综合77777| 18在线观看网站| 亚洲欧美日韩卡通动漫| 午夜视频国产福利| 日韩制服骚丝袜av| 各种免费的搞黄视频| 我要看黄色一级片免费的| 久久精品国产亚洲av涩爱| 又粗又硬又长又爽又黄的视频| 国产欧美日韩一区二区三区在线| 日本-黄色视频高清免费观看| 精品人妻在线不人妻| 成人毛片60女人毛片免费| 日本av手机在线免费观看| 新久久久久国产一级毛片| 久久久久久久久久久久大奶| 9191精品国产免费久久| 尾随美女入室| av视频免费观看在线观看| 久久青草综合色| 国产亚洲av片在线观看秒播厂| 国产精品偷伦视频观看了| 国产精品熟女久久久久浪| 久久久国产精品麻豆| 狂野欧美激情性xxxx在线观看| 性色av一级| 欧美精品一区二区大全| 91精品伊人久久大香线蕉| 国产伦理片在线播放av一区| 一级片'在线观看视频| 在线观看人妻少妇| 亚洲av成人精品一二三区| 99热这里只有是精品在线观看| 亚洲欧美精品自产自拍| 少妇猛男粗大的猛烈进出视频| 熟女av电影| 男女边吃奶边做爰视频| 国产色爽女视频免费观看| 午夜av观看不卡| 国产免费视频播放在线视频| 黑人欧美特级aaaaaa片| 久久久久精品性色| 色94色欧美一区二区| 黄色怎么调成土黄色| 国产精品国产av在线观看| 大码成人一级视频| 精品亚洲成国产av| 亚洲av男天堂| 亚洲伊人色综图| 成人国产麻豆网| 天天躁夜夜躁狠狠躁躁| 久久久久精品久久久久真实原创| 免费看av在线观看网站| 国产精品国产三级专区第一集| 国产老妇伦熟女老妇高清| 国产av精品麻豆| 国语对白做爰xxxⅹ性视频网站| 大陆偷拍与自拍| 日韩欧美精品免费久久| 人体艺术视频欧美日本| 丝袜美足系列| 国产高清不卡午夜福利| 啦啦啦视频在线资源免费观看| 97超碰精品成人国产| 中文字幕最新亚洲高清| 赤兔流量卡办理| 又粗又硬又长又爽又黄的视频| 熟妇人妻不卡中文字幕| 久久久久久人妻| 巨乳人妻的诱惑在线观看| 搡女人真爽免费视频火全软件| 激情视频va一区二区三区| 永久网站在线| 久久97久久精品| 99国产精品免费福利视频| 一边亲一边摸免费视频| 日本欧美视频一区| 亚洲国产精品专区欧美| 女人被躁到高潮嗷嗷叫费观| 国产成人精品在线电影| 亚洲av电影在线观看一区二区三区| 80岁老熟妇乱子伦牲交| 啦啦啦在线观看免费高清www| 男女午夜视频在线观看 | 久久ye,这里只有精品| 亚洲少妇的诱惑av| 亚洲熟女精品中文字幕| av电影中文网址| 久久亚洲国产成人精品v| 久久人人爽av亚洲精品天堂| 欧美老熟妇乱子伦牲交| 午夜久久久在线观看| 天天影视国产精品| 日韩三级伦理在线观看| 亚洲av综合色区一区| 色婷婷久久久亚洲欧美| 精品视频人人做人人爽| 亚洲av.av天堂| 国产精品蜜桃在线观看| 欧美日韩精品成人综合77777| 黄色 视频免费看| 国产成人精品久久久久久| 国产精品久久久久成人av| 国产成人精品久久久久久| 国产精品嫩草影院av在线观看| 免费观看在线日韩| 丰满少妇做爰视频| 大香蕉久久网| 久久99热这里只频精品6学生| 高清视频免费观看一区二区| 自拍欧美九色日韩亚洲蝌蚪91| 老司机影院成人| 在线免费观看不下载黄p国产| 香蕉丝袜av| 少妇猛男粗大的猛烈进出视频| 亚洲精品美女久久av网站| 人人澡人人妻人| 久久久久久久久久成人| 国产精品三级大全| h视频一区二区三区| 久久久国产一区二区| 丁香六月天网| 日韩三级伦理在线观看| 国产xxxxx性猛交| 久久久国产一区二区| 日韩电影二区| 色哟哟·www| 两个人免费观看高清视频| 亚洲欧美成人综合另类久久久| 边亲边吃奶的免费视频| 国产1区2区3区精品| 99国产精品免费福利视频| 9色porny在线观看| 国产毛片在线视频| 在线观看国产h片| 熟女av电影| 一区二区三区四区激情视频| 伦理电影大哥的女人| 久久ye,这里只有精品| 日韩成人伦理影院| 丰满乱子伦码专区| 久热这里只有精品99| 丰满乱子伦码专区| 午夜视频国产福利| 中文字幕最新亚洲高清| 欧美+日韩+精品| 久久综合国产亚洲精品| 久久久久国产精品人妻一区二区| 99久久人妻综合| 亚洲色图 男人天堂 中文字幕 | 精品99又大又爽又粗少妇毛片| av福利片在线| 成人二区视频| 在线免费观看不下载黄p国产| 国产黄色免费在线视频| 99热全是精品| 午夜av观看不卡| 国产无遮挡羞羞视频在线观看| 中文欧美无线码| 久久久久久久国产电影| 亚洲av中文av极速乱| 午夜福利在线观看免费完整高清在| 国产日韩一区二区三区精品不卡| 亚洲,欧美,日韩| 看免费av毛片| 伦理电影大哥的女人| 欧美日韩国产mv在线观看视频| 精品酒店卫生间| 午夜老司机福利剧场| 午夜福利在线观看免费完整高清在| 欧美人与性动交α欧美软件 | 国产片内射在线| 亚洲欧美成人精品一区二区| 黑人欧美特级aaaaaa片| 伦理电影大哥的女人| 我要看黄色一级片免费的| 国产免费一级a男人的天堂| 亚洲精品第二区| 最新的欧美精品一区二区| 亚洲国产欧美日韩在线播放| 亚洲国产av影院在线观看| 黑人巨大精品欧美一区二区蜜桃 | 飞空精品影院首页| 免费观看a级毛片全部| 久久久久久人人人人人| 精品一区二区免费观看| 老熟女久久久| 国产成人91sexporn| 涩涩av久久男人的天堂| 高清av免费在线| 18禁国产床啪视频网站| 免费大片18禁| 亚洲人成77777在线视频| 精品一区二区三区视频在线| 欧美日韩一区二区视频在线观看视频在线| 精品酒店卫生间| 国产精品三级大全| 亚洲成av片中文字幕在线观看 | 亚洲精品视频女| 欧美亚洲日本最大视频资源| 日韩精品有码人妻一区| 久久久久久久亚洲中文字幕| 大码成人一级视频| 亚洲成av片中文字幕在线观看 |