Effect of hydraulic retention time and pH on oxidation of ferrous iron in simulated ferruginous acid mine drainage treatment with inoculation of iron-oxidizing bacteria

The effect of hydraulic retention time (HRT) and pH on the biooxidation of ferrous iron during simulated acid mine drainage (AMD) treatment was investigated.The simulated AMD was highly acidic (pH 2.5), rich in iron (about 1700 mg/L) and copper (about 200 mg/L), and contained high concentrations of sulfate (about 4700 mg/L).The biooxidation of ferrous iron was studied in a laboratory-scale upflow packed bed bioreactor (PBR).The HRT was shortened stepwise from 40 h to 20 h, 13 h, and 8 h under the acidic environment at a pH value of 2.2.Then, the influent pH value was changed from 2.2 to 1.2 at a constant suitable HRT.Physiochemical and microbial community structure analyses were performed on water samples and stuffing collected from the bioreactor under different conditions.The results indicate that the efficiency of ferrous iron oxidation gradually decreased with the decrease of HRT, and when the HRT exceeded 13 h, ferrous iron in AMD was almost completely oxidized.In addition, the best efficiency of ferrous iron oxidation was achieved at the influent pH value of 1.8.Microbial community structure analyses show that Leptospirillum is the predominant genus attached in the bioreactor, and low influent pH values are suitable for the growth of Leptospirillum.

Effects of hydraulic retention time, temperature, and effluent recycling on efficiency of anaerobic filter in treating rural domestic wastewater

With rural population expansion and improvement of the socio-economic standard of living, treatment of rural domestic wastewater has rapidly become a major aspect of environmental concern. Selection of a suitable method for treatment of rural domestic wastewater depends on its efficiency, simplicity, and cost-effectiveness. This study investigated the effects of hydraulic retention time （HRT）, temperature, and effluent recycling on the treatment efficiency of an anaerobic filter （AF） reactor. The first round of experimental operations was run for three months with HRTs of one, two, and three days, temperatures of 18℃, 21℃, and 24℃, and no effluent recycling. The second round of experimental operations was conducted for another three months with HRTs of three and four days; temperatures of 30.67℃, 30.57℃, and 26.91 ℃ ; and three effluent recycling ratios of 1：1, 1：2, and 2：1. The first round of operations showed removal rates of 32% to 44% for COD, 30% to 35% for TN, 32% to 36% for NH4-N, 19% to 23% for NO3-N, and 12% to 22% for TE In the second round of operations, the removal rates varied from 75% to 81% for COD, 35% to 41% for TN, 31% to 39% for NH4-N, 30% to 34% for NO3-N, and 41% to 48% for TP. The average gas production rates were 6.72 L/d and 7.26 L/d for the first and second rounds of operations, respectively. The gas production rate increased in the second round of operations as a result of applied effluent recycling. The best removal efficiency was obtained for an optimum HRT of three days, a temperature of 30℃, and an effluent recycling ratio of 2：1. The results show that the removal efficiency of the AF reactor was affected by HRT, temperature, and effluent recycling.

Determination and discussion hydraulic retention time in membrane bioreactor system

Based on the microorganism kinetic model, the formula for computing hydraulic retention time in a membrane bioreactor system (MBR) is derived. With considering HRT as an evaluation index a combinational approach was used to discuss factors which have an effect on MBR. As a result, the influencing factors were listed in order from strength to weakness as: maximum specific removal rate K , saturation constant K s, maintenance coefficient m , maximum specific growth rate μ m and observed yield coefficient Y obs . Moreover, the formula was simplified, whose parameters were experimentally determined in petrochemical wastewater treatment. The simplified formula is θ=1.1(1/β-1)(K s +S)/KX 0, for petrochemical wastewater treatment K and K s equaled 0 185 and 154.2, respectively.

Influence of hydraulic retention time on efficiencies of high concentration PAC-MF bioreactor treating slightly polluted surface water

In this study,the influence of hydraulic retention time on feasibility,efficiency and membrane foul- ing of slightly polluted surface water treatment by a high concentration PAC-MF bioreactor were investigated. During three months operation,TOC,NH4 + -N,nitrobenzene,and TMP were measured to evaluate the MBR performance. The results show that,when HRT reduces from 3 h to 1 h,removal efficiency of TOC and ammonia-nitrite decrease a little. However,there is little effect of HRT on nitrobenzene. And the optimal hydraulic retention time is 1 h.

The Effect of Hydraulic Retention Times and Loading Rates on the Removal of Pollutants from Fish Processing Wastewater by Anaerobic Process

Anaerobic treatment model treats fish processing wastewater to be necessary for a small and medium factory that is very popular in Vietnam and other countries.Several techniques have been proposed.However,they are quite expensive and hard to operate,especially in remote areas.In this study,the hydraulic retention times(HRT)including 3,5,and 7 hours with a various organic loading rate of 1.5 to 6.5 kg COD/m3/day were investigated.Biomass concentration as mix-liquor volatile suspended solid(MLVSS)in the model is at 6,000 to 9,000 mg/L.On the basis of the result the optimal HRT with a 4.0 kg COD/m3/day organic loading rate was 8 hours which BOD5,COD removal efficiency were 92.18,87.36 percent respectively.By the end of the optimal hydraulic retention times,the total methane gas volume as a by-product was collected with 2.6 liters.

长/短HRT交替培养同步硝化反硝化除磷颗粒

为快速实现颗粒化同时富集反硝化聚磷菌(denitrifying phosphate accumulating organisms,DPAOs),在接种絮状活性污泥和长期低温储存的颗粒污泥后,以人工配水为处理对象,分别以恒定水力停留时间(hydraulic retention time,HRT,t_(HR))和不同比的长/短HRT交替模式运行4组序批式活性污泥反应器(sequencing batch reactor,SBR),探究长/短HRT交替运行下的饥饿作用对于富集DPAOs和造粒等方面的影响。结果表明,长/短HRT交替运行下的颗粒污泥均具有更高的DPAOs占比和脱氮除磷率,沉降性能良好且颗粒致密。其中,在12 h/6 h的长/短HRT交替模式下,同步硝化反硝化除磷颗粒的污染物去除性能最好,其长周期内COD、TN和TP的去除率分别达93%、96%和98%,短周期内的去除率为95%、90%和93%,这主要是大粒径颗粒内形成的缺氧区、饥饿条件下胞外聚合物的分泌以及反硝化菌对可溶性微生物产物(soluble microbial products,SMP)的利用等因素综合作用的结果;当HRT比提高至13.5 h/4.5 h时,过高水平的SMP积累和过短的厌氧时间会使得出水COD和TP质量浓度超标;而当HRT比降低至10.5 h/7.5 h时,反硝化聚磷菌的占比下降了18%,出水TN去除率也有所下降,表明12 h/6 h是采用长/短HRT交替运行的可参考值。

Effects of loading rate and hydraulic residence time on anoxic sulfide biooxidation

The optimal operation conditions in an anoxic sulfide oxidizing (ASO) bioreactor were investigated. The maximal removal rates for sulfide and nitrate were found to be 4.18 kg/(m3·d) and 1.73 kg/(m3·d), respectively. The volumetrical volumetric loading rates (LRs) observed through decreasing hydraulic retention time (HRT) at fixed substrate concentration are higher than those by increasing substrate concentration at fixed HRT. The sulfide oxidation in ASO reactor was partially producing both sulfate and sulfur; but the amount of sulfate produced was approximately one third that of sulfur. The process was able to tolerate high sulfide concentration, as the sulfide removal percentage always remained near 99% when influent concentration was up to 580 mg/L. It tolerated relatively lower nitrate concentration because the removal percentage dropped to 85% when influent con- centration was increased above 110 mg/L. The process can tolerate shorter HRT but careful operation is needed. Nitrate conversion was more sensitive to HRT than sulfide conversion since the process performance deteriorated abruptly when HRT was decreased from 3.12 h to 2.88 h. In order to avoid nitrite accumulation in the reactor, the influent sulfide and nitrate concentrations should be kept at 280 mg/L and 67.5 mg/L respectively. Present biotechnology is useful for removing sulfides from sewers and crude oil.

HRT对组合式填料SBBR脱氮性能和EPS的影响

研究了水力停留时间(HRT)对组合式填料序批式生物膜反应器(SBBR)处理模拟生活废水性能的影响。考察了不同HRT(16、12、8 h)的条件下SBBR的脱氮性能、脱氮速率和胞外聚合物(EPS)质量分数的变化。结果表明,HRT对COD去除率没有显著影响;缩短HRT抑制生物膜上微生物的活性,使紧密胞外聚合物(TB-EPS)和疏松胞外聚合物(LB-EPS)质量分数增加30.25%、29.88%,脱氮速率降低至64.1%;实验得出的最佳HRT为12 h。

生物产氢余煤再产甲烷的有利因素研究

厘定生物产氢后的余煤再产甲烷的有利因素,对于提高煤联产第二阶段甲烷产气效率具有重要的理论和实际意义。以内蒙古白音华露天矿煤为发酵底物,改变通气条件和水力停留时间(HRT),讨论不同条件下厌氧发酵产氢余煤再产甲烷量和煤结构的动态变化趋势。结果表明:(1)对比其他气氛条件,CO_(2)组产甲烷效果最好,单位气体生成量为4.72 mL/g,而HRT增加使产气效果逐渐降低。(2)氢化酶活性与产气量的变化规律具有一致性,反应结束后菌液化学需氧量值(COD)均偏低,认为CO_(2)可促进菌体酶活性增强,使CO_(2)甲烷化过程更明显,而较长的HRT不利于微生物菌群存活,建议在后期的工程实践中,设置较短的HRT工艺条件。(3)对厌氧发酵后的余煤进行XRD和FTIR监测,发现通CO_(2)后煤的芳香碳层间距最大,煤中一些活性官能团如羧基、羟基等均有所减少,HRT为3 d条件下微晶结构和官能团变化较显著,而随着HRT时间延长,煤结构变化愈加不明显。(4)通入CO_(2)不仅能提高产气率,还可以改变煤大分子结构和孔隙结构,达到煤层自身的增透、增扩、增渗和增解的目的,实现CO_(2)地质封存和煤层气生物工程的融合。

HRT对城市污水厂尾水反硝化深度脱氮的影响

污水厂尾水回用作为水源时,其ρ(TN)较高是亟待解决的问题.在调研污水厂尾水水质的基础上,利用MBBR(移动床生物膜反应器)对其进行深度脱氮,并考察HRT(水力停留时间)对不同填料(聚乙烯和陶粒)的MBBR运行效果的影响.结果表明,NO3--N是尾水中氮的主要形态,其质量浓度约占ρ(TN)的80.8%±8.4%.HRT分别为12、8和4 h时,对NO3--N去除率影响不大,均能达到90%以上,但反硝化能力随着HRT的缩短而成倍增加;HRT为4 h时各反应器的反硝化能力最大,聚乙烯和陶粒MBBR中分别为(28.4±14.5)和(27.4±14.3)mg(L·d)(以NO3--N计).随着HRT的减少,CODCr去除率呈降低趋势.三维荧光分析表明,进、出水中均含有类富里酸和类蛋白质等DOM物质.HRT为8 h时MBBR对DOM的去除率最高,聚乙烯填料MBBR对有机污染物的去除效果略优于陶粒填料.综合考虑氮和有机污染物去除效能,聚乙烯和陶粒填料MBBR优化HRT均为8 h.

厌氧段HRT对A_2N工艺反硝化除磷脱氮效果的影响

为了考察厌氧段水力停留时间(HRT)对A2N工艺反硝化除磷脱氮效果的影响,采用连续流双污泥反硝化除磷脱氮装置以生活污水为处理对象,研究了厌氧段在不同HRT时系统的除磷脱氮效果,以及厌氧段不同HRT对系统处理过程的影响。结果表明,厌氧段是A2N工艺实现反硝化除磷脱氮的关键阶段。当厌氧段的HRT过长时,虽然溶解性PO43-的总释放量增加,但是后续的缺氧吸磷量和总氮的去除量并没有相应地增加。厌氧段的HRT时间过短,反硝化聚磷菌(DPB)在此对进水中易降解COD(CODRB)吸收不完全,导致后续缺氧吸磷量下降,同时影响了系统的除磷和脱氮效果。在处理实际生活污水水质时,厌氧段的HRT为2h即可满足除磷和脱氮要求。

HRT对瓷粒BAF处理生活污水效能的影响

通过实验室模型试验研究了瓷粒曝气生物滤池处理生活污水的效能,分析了在气水比一定的条件下,水力停留时间(HRT)变化对曝气生物滤池处理效能及运行特性的影响规律。考察了不同HRT运行下,COD、NH4+-N、NO2--N、NO3--N、TN、SS等指标的变化,结果表明,当进水COD为280～320mg/L,气水比为3:1,HRT为10h的条件下,处理效果最好,其中COD、NH4+-N、TN、SS的平均去除率分别为92.6%、97.8%、34.7%、84.2%。当HRT逐渐降低时,以上指标的去除效果都有所下降,但去除效能的下降与HRT的降低不呈线性关系。当HRT降至3h,去除效能有一定程度的上升,COD、NH4+-N、TN、SS的去除率有所增加。

HRT对UASB-SMBR(PTFE)组合工艺处理某油田含油废水性能的影响

利用升流式厌氧污泥床(UASB)与膜生物反应器(MBR)组合工艺处理含油废水,在不同的水力停留时间(HRT)下考察了系统对NH3-N、石油类污染物和挥发酚去除以及COD和浊度降低的效果,也考察了膜污染和清洗情况。结果表明,该组合工艺对各种污染物质都有很好的去除效果,出水水质能够满足国家污水综合排放一级标准,NH3-N、石油类污染物、挥发酚的平均去除率以及COD和浊度的降低率分别达到98.58%、98.33%、99.83%、95.00%和99.84%;污染物的去除效率随着水力停留时间的缩短而降低。在实验过程中还发现,在不同水力停留时间下会产生不同程度的膜污染,且水力停留时间的长短与膜污染的速率呈反相关关系;采用四步法清洗后,聚四氟乙烯(PTFE)膜的透水性基本完全恢复。UASB-SMBR(PTFE)组合工艺能够稳定运用于含油废水的处理。

HRT对一体式PTFE膜生物反应器运行效果的影响

针对垃圾渗滤液高COD、高NH4-N,低生化性的特点,开发UASB/缺氧/好氧-膜生物反应器组合处理工艺.在不同水力停留时间(HRT)下,考察了系统对污染物去除效果及其膜污染特性.结果表明,在不同的HRT条件下,UASB/缺氧/好氧-膜生物反应器组合工艺处理垃圾渗滤液出水水质良好且稳定.出水COD除率随HRT的升高先增加后降低,且HRT为12.8h时达到最大值94.96%;系统对NH4-N的平均去除率随HRT的延长而升高;膜污染实验结果显示:较低的HRT条件下意味着膜通量较高,会加剧膜污染进程.通过实验得出结论当HRT=15h时,对膜污染的控制最为有利.对膜进行清洗,并进行扫描电镜分析.分析结果显示凝胶层的形成是膜透水性下降的主要原因.

MBBR中HRT与pH对短程硝化反硝化的影响

为了开发经济高效的生物脱氮工艺,在MBBR中进行了短程硝化反硝化的研究,考察了HRT与pH对短程硝化反硝化的影响。结果表明,在短程硝化反硝化过程中,在室温、不控制溶解氧的条件下,NH_4^+-N与COD去除率随着HRT的延长而增大,出水NO_2^--N随着HRT的延长先增大后减少,当HRT为8h时出水NO_2^--N最高;当pH由5增加到10时,COD去除率的变化较小,NH_4^+-N去除率和出水NO_2^--N则随着pH的增大先增大后减小,pH在8~9时对NH_4^+-N的处理效果最好,出水NO_2^--N最高。

HRT对折流板式厌氧生物反应器处理印染废水的影响

针对印染废水水质水量变化大、ρ(BOD5)/ρ(CODCr)低、色度高的特点,以苏南某污水厂(印染废水比例大于90%)调节池出水为研究对象,开展ABR(折流板式厌氧生物反应器)处理印染废水试验,处理规模为2 L/h,重点考察不同HRT(水力停留时间)下ABR对CODCr、色度的去除和对ρ(BOD5)/ρ(CODCr)的提升效果.结果表明:1当进水平均ρ(CODCr)为517 mg/L、色度为380倍、ρ(BOD5)/ρ(CODCr)为0.20时,随着HRT(32、24、18、14和10 h)的缩短,CODCr平均去除率由46.1%降至22.5%,色度平均去除率由60.6%降至51.0%,出水ρ(BOD5)/ρ(CODCr)由0.39降至0.30.2随着格室数量的增加,ρ(CODCr)和色度逐渐降低,其中第1格室的CODCr和色度的去除率分别占总去除率的20.0%和51.0%,紫外-可见吸收光谱扫描也证明了这一点.3经过ABR厌氧水解后污染物种类明显减少,说明ABR厌氧水解作用较好,可为后续好氧工艺奠定基础.

以丝瓜络为碳源的固相反硝化系统性能

构建以丝瓜络为碳源的固相反硝化系统,探究不同水力停留时间(HRT)和进水硝酸盐浓度(INC)下该系统的反硝化性能,为丝瓜络作为水产养殖尾水反硝化碳源的工艺优化提供理论依据。以丝瓜络(LS)为一维反硝化反应器(denitrification reactor,DR)外加碳源,在流场环境下,测定不同HRT(16、20、24和28 h)和INC(50、75、100和125 mg/L)下反硝化系统对硝酸盐氮(NO_(3)^(-)-N)、亚硝酸盐氮(NO_(2)^(-)-N)、氨氮(NH_(4)^(+)-N)、总氮(TN)、总磷(TP)和化学需氧量(CODcr)的去除效果。并采用高通量测序技术对丝瓜络反硝化反应器(LS-DR)在运行初期和末期时的细菌群落结构进行分析。当INC为50 mg/L,HRT为24h时,LS-DR对NO_(3)^(-)-N和TN均有较好的去除效果,去除率分别为98.97%±0.52%和97.84%±0.94%,此时出水NO_(2)^(-)-N浓度也达到较低水平(小于0.5 mg/L);在HRT为24 h的基础上,当INC增加至75、100和125 mg/L时,其NO_(3)^(-)-N去除率和NO_(3)^(-)-N去除速率(NRR)均随INC的增加而显著增加,出水COD则随INC的增加而降低,但均未实现完全反硝化,然而,LS-DR在整个实验期间均能完全去除NH_(4)^(+)-N;扫描电镜结果显示,丝瓜络表面结构有利于微生物附着生长;高通量测序结果显示,LS-DR的优势菌门包括变形菌门、拟杆菌门、弯曲杆菌门、厚壁菌门和疣微菌门;被鉴定的优势菌属中热单胞菌属(1.46%)、陶厄氏菌属(0.55%)、固氮螺菌属(3.32%)、Simplicispira(1.01%)、假黄色单胞菌属(0.39%)、草螺菌属(3.02%)和Uliginosibacterium(0.9%)主要参与反硝化的进行,Cytophaga xylanolytica(1.61%)和Cloacibacterium(2.69%)主要参与了丝瓜络的降解,黄杆菌属(1.17%)和Diaphorobacter(0.64%)既能进行反硝化,也能降解丝瓜络。LS-DR的最佳HRT为24 h,最适宜的INC为50 mg/L。本研究为丝瓜络固相反硝化工艺的优化提供了理论基础,为开发新型缓释碳源在养殖尾水处理中的应用提供参考。

HRT对发酵产氢厌氧活性污泥系统的影响

HRT的改变可对发酵产氢厌氧活性污泥系统产生多方面的影响.在进水COD质量浓度为6 000 mg/L、35℃、不对进水pH值进行调节等条件下,发酵产氢厌氧活性污泥系统HRT从8 h降低为6 h时,其pH值、ALK分别从4.3和250 mg/L降低为4.2和180 mg/L,ORP从-380^-360 mV升高到-330^-300 mV,生物量虽然从8.7 gVSS/L降低到了7.2 gVSS/L,其产氢能力却从0.14 L/(gVSS.d)提高到0.22 L/(gVSS.d),液相末端发酵产物总量从1 106.1 mg/L增加为1 695.1 mg/L,作为乙醇型发酵目的产物的乙醇和乙酸的含量从90%减少为85%.HRT进一步降低为4 h时,系统内生态条件发生剧烈变化,其pH值、ALK、ORP分别为3.7、75 mg/L和-210 mV,生物量锐减至1.1 gVSS/L,同时乙醇型发酵演替为混合酸发酵,产氢能力下降为零.可见,多种因素可对发酵产氢厌氧活性污泥系统产生影响,而其中HRT是直接可控的第一影响因素.

HRT对餐厨垃圾与秸秆混合高温厌氧发酵的影响

以餐厨垃圾和秸秆(按TS比1:1混合)为原料,水力停留时间(HRT)逐级递减至5,3,1.5,1,0.5d,对应有机负荷(OLR)依次为8.0,6.66,3.33,5.0,5.0g VS/(L?d),开展了55d的连续高温发酵试验,并对微生物组成进行分析.实验发现,当HRT由5d缩短到1d的过程中,反应器运行稳定,OLR,挥发性固体(VS)去除率,产气率和容积产气率均维持在较高水平.当HRT降至0.5d时,pH值稳定在7.0左右,并未出现VFA累积,但反应器几乎停止产气,VS去除率仅为5.77%,微生物发生冲刷流失.高通量测试结果表明,当HRT为0.5d时,体系内嗜氢产甲烷菌的比例增加,嗜乙酸产甲烷菌降至0.6%,而Clostridiales等能够与产甲烷菌共生的水解酸化细菌的比例增加了近1倍,推测乙酸氧化菌与嗜氢产甲烷菌共生是乙酸产甲烷的主要途径.