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.

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.

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.

Effect of Solid Retention and Hydraulic Retention Times on Membrane Fouling in Membrane Bioreactor

In this bench scale submerged membrane bioreactor, effect of solid retention time and hydraulic retention time on membrane fouling propensity has been studied. This experiment is carried out at different solid retention time of 5, 10, 30, 70 and 98 days; and fouling behavior of membrane bioreactor is investigated. Average effluent quality is found to be 88.14%-94.38%. The experiment with different hydraulic retention is carried for 3 to 4 days and fouling behavior has been investigated. The effluent quality at different hydraulic retention time of 1, 2, 3, 5, 10 and 24 hours has been investigated. This paper aims to search optimal values of solid and hydraulic retention times at which lower fouling and higher organic removal efficiency can be obtained. This study has been mainly focused on operating parameters rather than microbial structure, effect and analysis of activated sludge to membrane fouling.

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.

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对硫自养反硝化脱氮性能及微生物群落结构的影响

为探究水力停留时间(HRT)对单质硫源驱动下硫自养反硝化系统的影响,构建了硫自养反硝化UASB反应器,研究不同HRT下单质硫自养反硝化系统脱氮性能,并从微生物群落结构的角度分析系统种间协同竞争作用。结果表明:①不同HRT,单质硫自养反硝化系统脱氮性能存在差异,HRT下降到16 h后NO_(3)^(-)-N去除率从75%降低到20%;②HRT=48 h,出水SO_(4)^(2-)浓度低于理论值,发生硫酸盐还原反应;③Thiobacillus为反应器中的优势菌属,相对丰度达到26.3%,随HRT降低,反应器中脱氮微生物丰度降低,部分菌属丰度降低到0%;④硫酸盐还原菌在HRT=48 h大量富集,反应器内部存在硫循环过程。本实验为硫自养反硝化脱氮提供技术支持,对硝酸盐污染控制具有重要的指导价值。

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。

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。

改良型A^(2)O-MBR工艺处理低碳氮比污水的实验研究

为强化A^(2)O-MBR工艺脱氮除磷效果,对国家管网集团某场站点生活污水进行实验研究,进行工艺工况调整和条件优化。分析碳氮比、回流比、水力停留时间对出水水质的影响。实验结果表明,在碳氮比为6~7,膜池直接回流到缺氧池条件下,改良型A^(2)O-MBR工艺的最终COD出水为13.54 mg/L,TN和TP的平均去除率达到了80.26%和80.13%,出水水质完全满足地表水环境质量标准(GB 3838—2002)地表准Ⅳ类水的要求。实验表明,该工艺在脱氮除磷方面有显著效果,在降解污染和整体达标排放方面发挥着重要的作用,且能为厂站小型生活污水处理站提标改造的技术参数选择提供参考。

反硝化生物滤池处理乡镇污水厂尾水的脱氮效能研究

针对乡镇污水厂尾水碳源不足的特点,通过模型试验研究了HRT、碳氮比(C/N)、碳源种类对反硝化生物滤池(DNBF)深度脱氮效果的影响。结果表明,在HRT为60~80 min,C/N为4.5~5.5,以玉米芯浸泡液作为碳源时,DNBF具有良好的脱氮效果,出水水质稳定且能满足《四川省岷江、沱江流域水污染物排放标准》DB 51/2311-2016的排放限值。DNBF处理效能与原水C/N和工艺HRT显著相关,当HRT降至40 min以下时,出水COD明显升高;当C/N降至4.5以下时,填料层内出现不同程度的NO_(2)^(-)-N积累问题。DNBF最佳运行参数为HRT=60 min、C/N=5.5、以玉米芯浸泡液为碳源,此条件下其出水TN、NO_(3)^(-)-N、NH_(4)^(+)-N、COD、TP平均浓度分别为7.77、3.98、1.13、24.23、0.27 mg/L,对应的平均去除率分别为67.18%、68.46%、47.95%、74.04%、38.99%,脱氮效果以及对其它污染物的去除效果良好。

不同水力停留时间对新疆油田压裂返排液COD去除及微生物菌群特征研究

针对新疆油田压裂返排液较难处理的现状,采用生物膜法作为处理工艺的主要单元,探究不同水力停留时间(HRT)对化学需氧量(COD)去除的影响,通过高通量测序和功能预测确定不同水力停留时间下的微生物群落特征.结果表明:水力停留时间48 h是生物膜法处理新疆油田压裂返排液的适宜水力停留时间,COD去除效率最高,进水COD平均去除率46.77%,平均去除速率83.33 mg·(L·d)^(-1).相对于水力停留时间36、72 h,水力停留时间48 h的微生物多样性更高,群落组成更丰富,且形成以Proteobacteria(变形菌门)、Firmicutes(厚壁菌门)、Campylobacterota(弯曲菌门)、Bacteroidota(拟杆菌门)和Desulfobacterota(脱硫菌门)为主要优势菌的微生物群落.微生物菌群具有难降解物质代谢的功能基因,可促进新疆油田压裂返排液的生物降解.

Effects of hydraulic retention time on net present value and performance in a membrane bioreactor treating antibiotic production wastewater

A cost sensitivity analysis was performed for an industrial membrane bioreactor to quantify the effects of hydraulic retention times and related operational parameters on cost.Different hydraulic retention times(72-24 h)were subjected to a flat-sheet membrane bioreactor updated from an existing 72 h oxidation ditch treating antibiotic production wastewater.Field experimental data from the membrane bioreactor,both full-scale(500 m/d)and pilot(1.0 m3/d),were used to calculate the net present value(NPV),incorporating both capital expenditure(CAPEX)and operating expenditure.The results showed that the tank cost was estimated above membrane cost in the 38.2%,where capital expenditure contributed 24.2%more than operational expenditure.Tank construction cost was decisive in determining the net present value contributed 62.1%to the capital expenditure.The membrane bioreactor has the advantage of a longer lifespan flat-sheet membrane,while flux decline was tolerable.The antibiotics decreased to 1.87±0.33 mg/L in the MBR effluent.The upgrade to the membrane bioreactor also benefited further treatments by 10.1%-44.7%lower direct investment.

Modelling the thresholds of nitrogen/phosphorus concentration and hydraulic retention time for bloom control in reclaimed water landscape

The risks posed by algal blooms caused by nitrogen and phosphorus in reclaimed water used in urban water landscapes need to be carefully controlled.In this study,the combined effects of the nitrogen and phosphorus concentrations and the light intensity and temperature on the specific growth rates of algae were determined using Monod,Steele,and Arrhenius models,then an integrated algal growth model was developed.The algae biomass,nitrogen concentration,and phosphorus concentration mass balance equations were used to establish a new control model describing the nitrogen and phosphorus concentration and hydraulic retention time thresholds for algal blooms.The model parameters were determined by fitting the models to data acquired experimentally.Finally,the control model and numerical simulations for six typical algae and mixed algae under standard conditions were used to determine nitrogen/phosphorus concentration and hydraulic retention time thresholds for landscape water to which reclaimed water is supplied(i.e.,for a reclaimed water landscape).

水力停留时间对牛粪和白菜尾菜混合厌氧发酵的影响

厌氧发酵产沼气是处理有机废弃物的有效手段。牛粪是常见的农业废弃物,由于厌氧发酵过程中降解大量难降解组分需要较高的水力停留时间(HRT),导致发酵效率较低。与易降解的白菜尾菜混合发酵可以有效提高甲烷产量,降低HRT可以提高系统的甲烷发酵的效率。为此,研究采用全混式反应器(CSTR)模拟沼气工程发酵罐运行,考察了HRT(25、20、15、10、8、5 d)对牛粪和尾菜混合厌氧发酵的影响。结果表明:HRT为25 d时,甲烷产率最高为185 mL·g^(-1),降低HRT造成甲烷产率显著降低;HRT降至5 d时,由于挥发性有机酸的大量累积,导致反应器运行失败。采用本系统的极限HRT为8 d,此时系统的容积甲烷产率最高,为0.86 L·(L·d)^(-1)。研究结果可为实际沼气工程中处理牛粪和尾菜时协调甲烷产率和容积甲烷产率,进而为选择合适的HRT提供参考。

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。