重力出流式膜生物反应器污泥浓度的优化控制

采用重力出流式膜生物反应器(Membrane Bioreactor, MBR)工艺对生活污水进行了实验研究. 重力出流式MBR是利用液位水头重力驱动出水,整个系统结构紧凑,操作简便. 结果表明,随着污泥浓度增大(3.9~18.4 g/L),同样的曝气强度对膜表面滤饼层的剪切能力降低,膜通量下降;污泥粘度从5.4 mPa×s上升到680 mPa×s,相应的污泥中的传氧系数与清水中的传氧系数之比a从0.89降到0.10. 因此,从提高膜通量、氧传递速率和降低能耗的角度出发,将MBR的污泥浓度控制在适当范围是非常必要的. 此外,当污泥浓度大于4.8 g/L,污泥浓度的提高对有机物的去除、硝化以及反硝化速率的提高没有明显的贡献. 因此,从MBR的处理能力和运行能耗的双重影响确定MBR的最佳处理污泥浓度值为4~6 g/L,在该浓度区间,生物反应器系统对冲击负荷有较好的抵御能力,同时系统的运行能耗也较低.     

动态膜微滤含污泥水及膜污染特征

以陶瓷管为载体,对高岭土动态膜微滤含污泥水性能及膜污染特征进行了较为详细的研究. 考察了错流速度、跨膜压差及污泥浓度对滤出液通量及水质的影响,结果表明,提高错流速度和增大跨膜压差均使滤液通量增加,但错流速度超过2.0 m/s易引起动态膜脱落;污泥浓度增加,则滤液通量明显降低;过滤进行约30 min后,出水浊度基本为0;60 min后,化学需氧量的去除率基本保持在50%以上. 动态膜层及其截留的污染物阻力占总过滤阻力的90%以上. 对膜面特征污染物成分分析表明,P, Ca为膜面主要污染元素,分别占23.77%和20.60%(w);对陶瓷膜孔中不可逆污染物的化学洗脱液分析表明,膜中总有机碳近4370 mg/m2,Ca, Mg是主要无机污染元素,分别约1240和886 mg/m2. 先后用0.2 mol/L的NaOH水溶液和0.1 mol/L的HCl水溶液清洗膜中不可逆污染物,可使基膜通量恢复至新膜的85%.     

吡啶废水共代谢过程中产生污泥膨胀的机理

通过共代谢法处理吡啶废水,对共代谢过程中产生污泥膨胀的机理进行研究。结果表明,共代谢反应器处理效果在第36-50天内发生恶化,出水吡啶的质量浓度从1.4 mg/L增加到60.7 mg/L,TN去除率从88%降低至46%;污泥容积指数(SVI)从132.8 mL/g增加到595.2 mL/g,污泥的质量浓度从6.324 g/L降低至1.680 g/L,表明发生了污泥膨胀并造成污泥流失。通过胞外聚合物含量和高通量测序分析,发现共代谢反应器中污泥多糖分泌菌Saccharibacteria大量富集,导致VSS中胞外多糖的质量分数从7.1 g/g增加到54.3 g/g,最终产生污泥膨胀。     

聚合氯化铝强化好氧颗粒污泥的形成及污染物去除特性研究

在反应器中分别投加不同质量浓度的聚合氯化铝溶液(分别为0、50、100、400 mg/L废水),作为对照组、低PAC组、中PAC组、高PAC组,培养好氧颗粒污泥。研究发现,培养70天后:除对照组外其余3组均能形成颗粒污泥;随着PAC投加量的增加,4组反应器污泥质量浓度、比重逐渐增高,污泥体积指数、污泥的含水率和不完整性系数逐渐降低;4组反应器的COD去除率分别为95%、98%、98%和98%,氨氮去除率分别为60%、94%、99%和99%,总无机氮去除率分别为58%、84%、79%和78%;投加PAC的3组污泥比好氧速率、硝化速率、反硝化速率均高于对照组,投加PAC的3组中随着PAC投加量的增加,污泥的硝化速率逐渐增高,比好氧速率、反硝化速率逐渐降低。     

MBR工艺处理啤酒废水的工程应用

根据啤酒废水的特点,考察了采用膜生物反应器(MBR)技术深度处理啤酒废水过程中的水质指标与设备运行参数,并对污泥浓度进行测定,从而对污泥负荷以及膜污染状况进行研究,工程运行结果表明:在进水CODCr642～1626mg/L、NH4+-N15～35mg/L、TP0.6～14mg/L、TN19.5～41.1mg/L情况下,MBR产水CODCr50mg/L、NH4+-N5mg/L、TP0.3mg/L、TN2.3mg/L。水质达到国家景观用水标准(GB/T18921—2002);好氧池DO控制在2～4mg/L,可有效提高氨氮的去除率;适当调整排泥量,使膜池污泥质量浓度维持在6～8g/L可缓解膜污染速度。     

好氧颗粒污泥处理啤酒废水的研究

以葡萄糖模拟废水培养出的好氧颗粒污泥为接种体,通过啤酒废水驯化,考察该污泥处理啤酒废水的可行性。实验结果表明,葡萄糖好氧颗粒污泥经驯化后能够迅速适应这种以糖类有机污染物为主的啤酒废水,驯化前后的污泥形态、生物活性差别不明显,相应的比耗氧速率分别为41.90和39.54g[O2]/(kg[MLSS].h)。驯化后的MLSS的质量浓度为8.23g/L左右,反应器的有机负荷稳定在4.3g[COD]/(L.d),而出水COD的质量浓度保持在45mg/L以下。因此,采用好氧颗粒污泥处理易生化的中低浓度工业废水有良好的应用前景。     

膜浓缩污泥的流变学特性研究

研究了污泥质量浓度ρ、温度T和剪切速率对膜浓缩污泥流变学特性的影响。结果表明,在温度15～35℃和污泥质量浓度4～35 g/L时,膜浓缩污泥的粘度μ与质量浓度、温度的关系可采用复合指数模型描述,lnμ与1/T和ρ呈现二元线性关系;与温度相比,污泥浓度对粘度的影响更为明显。膜浓缩污泥呈现剪切稀化特性,在低质量浓度(<10 g/L)下的流变性更接近于宾汉模型,而高质量浓度(>10 g/L)下的流变性则接近于幂律模型。幂律模型拟合得到的流型指数均<1,说明膜浓缩污泥属于假塑性流体。宾汉模型和幂律模型的稠度系数与污泥质量浓度的关系均可采用指数模型进行描述。     

无纺布膜临界通量及其在洗浴废水处理中的应用研究

以无纺布平板膜生物反应器为试验装置,采用通量阶梯式递增法的临界通量进行了测定,研究了混合液污泥浓度(MLSS)对无纺布膜临界通量的影响,考察了膜通量对无纺布平板膜生物反应器长期运行的影响。试验结果表明,无纺布膜的临界通量与MLSS浓度成反比,当MLSS的质量浓度从3 g/L增长到9 g/L时,无纺布膜临界通量从17 L/(m2·h)下降到13 L/(m2·h)。在MLSS的质量浓度控制为5 g/L,膜通量低于临界通量15 L/(m2·h)的条件下,无纺布平板膜生物反应器可连续稳定运行130 d,且反应器出水各项指标均可满足GB/T 18920—2002《城市污水再生利用城市杂用水水质》标准的要求。     

动态膜生物反应器技术进展

该文介绍了动态膜生物反应器(dynamic membrane bio-reactor,DMBR)的成膜机理、膜结构形态、过滤模型及阻力特性,讨论了基网选择、污泥浓度(MLSS)、出水水头、错流速度对动态膜生物反应器运行特性的影响,对DMBR的应用前景进行了展望。     

中空纤维膜无泡充氧特性研究

使用材质为聚四氟乙烯(PTFE)和聚-4-甲基-1-戊烯(PMP)的两种中空纤维膜组件进行无泡充氧特性研究，分析回流量、进气压力和温度等因素对氧传质系数、氧传质速率(OTR)的影响。结果表明：当操作模式为错流，回流量为100 L/h，温度为34℃，进气压力为2、3 k Pa时，PTFE中空纤维膜的氧传质系数分别为0.302 4、0.388 9 h^-1,OTR分别为0.107、0.133 g/(m²·h),PMP中空纤维膜组件的氧传质系数分别为0.248 2、0.302 4 h^-1,OTR分别为0.085、0.102 g/(m²·h)，两种膜组件的氧传质系数和OTR都随着进气压力的增大而增大；当进气压力为3 k Pa时，在回流量为25～100 L/h、温度为4～34℃范围内，随着回流量和温度的增大，氧传质系数与OTR均增大；实验选用的PTFE和PMP两种中空纤维膜组件无泡充氧性能，均明显优于传统微孔曝气方式，可为新型曝气方式的开发提供参考。     

膜生物反应器处理垃圾渗滤液问题分析

针对目前垃圾渗滤液用膜生物反应器（MBR）系统处理效果不佳、运行不稳定的问题,通过理论模型预测分析了渗滤液系统MBR的污泥浓度及其构成。结果表明垃圾焚烧厂的渗滤液MBR存在污泥浓度过高（22．0g／L）的问题,如果采用厌氧微网预处理则能将污泥浓度降低约50％,可大大提高MBR的运行稳定性。填埋场渗滤液MBR则存在处理年轻期渗滤液污泥浓度过高,而污泥浓度和污泥活性会随填埋龄增加迅速下降的问题,建议采取必要的预处理措施降低年轻期渗滤液的污染物负荷,改善中、老年期渗滤液的可生化性能,提高以MBR为主体的垃圾渗滤液处理工艺的运行稳定性。     

双酚A在膜生物反应器中的去除及转化分析

通过小试考察了MBR去除双酚A(BPA)的机理及转化规律。结果表明,BPA的加入未对MBR的运行产生明显影响。随着MBR运行压力的升高,出水BPA含量呈现下降的趋势。出水初期平均压力为4.8 kPa,出水平均BPA的质量浓度为3.98 mg/L,运行后期出水平均压力为46.4 kPa,出水平均BPA的质量浓度为1.67 mg/L。对反应池内污泥、膜清洗洗脱液中BPA的检测发现,BPA在反应池内污泥、膜滤饼层和凝胶层中具有很高的含量分布。BPA的3种主要降解产物在反应器中的含量与出水含量相差不大,但在膜面的凝胶层和滤饼层中有一定程度的积累。在70 d的运行时间内,MBR去除BPA的主要机理是膜面滤饼层和凝胶层通过截留已吸附BPA的污泥而形成强化去除作用。只有部分BPA通过生物降解作用转化为其产物,生物降解作用在本研究中属于次要地位。     

MBR工艺处理PTA废水的工业化模拟试验

介绍了某PTA企业生产废水的处理现状以及采用MBR工艺改造废水处理系统的工业化模拟试验。包括MBR的启动和污泥的驯化,以及在不同的CODCr负荷下的运行情况。当污泥的质量浓度在6.5g/L左右,溶解氧质量浓度控制在2mg/L,HRT在15h时,CODCr的平均去除率能达到93.80%;氨氮和总磷的平均去除率达到90.28%和89.37%。试验期间,还考察了非常态下膜的污染耐受性以及微生物的恢复能力。     

Effect of Sludge Retention Time on Membrane Bio‐Fouling Intensity in a Submerged Membrane Bioreactor

Abstract

The submerged membrane bioreactor (sMBR) is being increasingly applied for municipal and industrial wastewater treatment. This paper examines the role of sludge retention time (SRT), an important operating parameter of the MBR as it affects the biological characteristics of the sludge and therefore influences membrane fouling. Well controlled runs were carried out at short SRT (10days) and moderate SRT (30days) in a 30 L submerged MBR equipped with KUBOTA flat‐sheet membranes. At steady operation, the mixed liquor suspended solids (MLSS) stabilized at approximately 5–6 g/L and 8.5–10 g/L for SRT 10 and 30days respectively. The DGGE profiles suggested a shift in the dominant bacterial community with the prolonged SRT. The soluble microbial products (SMP) were 9.3 mg/L and 5.4 mg/L at the SRTs of 10days and 30days respectively. The total amount of extracellular polymeric substance (EPS) extracted from the floc and the supernatant was approximately constant at the two SRTs under the same organic loading rate. However, the polysaccharide concentration in the supernatant was about 100% higher for the SRT of 10days than that for 30days. The viscosity of the biomass increased with the prolonged SRT, while the estimated average air induced water velocity was similar for the two SRTs. The results of flux stepping tests showed that the membrane fouling rate (dTMP/dt) at SRT 10days was always higher than that at 30days at each flux step. Similarly, long term experimental runs at a constant flux of 20 L/m²·h clearly showed more severe membrane fouling for the SRT of 10days than that at 30days. This implies that fouling is more influenced by the concentration of SMP and Polysaccharides than the MLSS.     

MLSS concentration: Still a poorly understood parameter in MBR filterability

In this paper Membrane Bioreactor (MBR) activated sludge is obtained from full scale MBRs and submitted to cross-flow filtration using always the same membrane and operational conditions. Samples are diluted in order to create suspensions with different Mixed Liquor Suspended Solids (MLSS) concentrations. MLSS values varied between 3.6 and 18.3 g/L. Contrary to literature results filterability did not present a continuous increase with decreasing MLSS concentrations. Activated sludge with MLSS concentration exceeding 10 g/L originated dilution samples with worse filterability. The dilution caused an increase of particles in the range 10 to 20 μm and a decrease in the range 30 to 100 μm. The activated sludge samples had non- Newtonian viscosity and Soluble Microbial Products (SMP) concentrations varied between 60 and 11 mg/L. Activated sludge samples with MLSS concentrations exceeding 10 g/L are entrapping particles smaller than 20 μm in the activated sludge bulk that therefore are not contributing to the increase of resistance on the membrane. Activated sludge samples with lower MLSS concentrations do not show the capability to entrap particles. These different behaviours suggest that are optimal MLSS concentration ranges for MBR operation.     

The effect of COD/N ratio on process performance and membrane fouling in a submerged bioreactor

Influent chemical oxygen demand/nitrogen (COD/N) ratio is used to control fouling in membrane bioreactor (MBR) systems. However, COD/N also affects the physicochemical and biological properties of MBR biomass. The current study examined the relationship between COD/N ratio in feed wastewater and extracellular polymeric substances (EPS) production in MBRs. Two identical submerged MBRs with different COD/N ratios of 10:1 and 5:1 were operated in parallel. The cation concentration and floc-size of the sludge were measured. The composition and characteristics of bound EPS and soluble microbial products (SMP) under each COD/N ratio were also examined. Batch tests were conducted in 1000 mL bottles to study the process of the release of foulants from the sludge when 1 g of (NH₄⁺-N)/L was added. Results showed that the influent COD/N ratio could change the physicochemical properties of EPS and SMP. Moreover, excessive NH₄⁺ in the supernatant could facilitate the role of NH₄⁺ as a monovalent cation, the replacement of the polyvalent cation in bound EPS, and even the extraction of EPS components from the surface of the sludge to form new SMP.     

两级序批式MBR膜污染控制方法研究

针对MBR在实际应用过程中存在的同步脱氮除磷效果不佳、膜污染严重等问题,提出两级序批式MBR工艺,对该工艺的膜污染影响因素及控制方法进行了试验研究.结果表明,在MBR中保持适宜的污泥质量浓度对于膜污染的控制有重要的作用,当污泥质量浓度稳定在6～7g·L~(-1)时,膜比流量基本稳定,随着污泥质量浓度的增加,膜比流量逐步降低,当污泥质量浓度超过10g·L~(-1)以后,膜比流量直线下降;投加PAC至1 g·L~(-1)可以增加污泥粒径,减少大分子有机物在膜表面沉积,从而有助于延缓膜污染;序批式间歇运行与空曝相结合的运行方式可以有效降低泥饼层污染及凝胶层污染,使系统在更高膜通量下运行,而膜污染速率却远低于连续流单级好氧MBR系统.     

Operation of Membrane Bioreactor with Powdered Activated Carbon Addition

Abstract

The effect of powdered activated carbon (PAC) addition to the activated sludge (AS) in a membrane bioreactor (MBR) has been investigated. The long term nature of the tests allowed the PAC to gradually incorporate into the biofloc forming biologically activated carbon (BAC). One series of tests involved 4 bench scale (2 L) MBRs operated at sludge retention times (SRTs) of 30 days with PAC inventories of 0, 1, 3 and 5 g/L and steady state biomass concentrations of 12.0±1.0 g/L. The characteristics of the mixed liquors (MLSS) from the 4 reactors were compared. Short term filtration tests, including measurement of specific cake resistance (SCR), flux decline profile, and irreversible fouling resistance in an unstirred cell and “sustainable” flux (by monitoring transmembrane pressure (TMP) rise) in a crossflow cell all showed better filtration performance for the MLSS with BAC compared with the AS alone. In terms of SCR and flux decline profile the 1 g/L PAC addition performed best, but in terms of minimizing irreversible membrane fouling and maximizing “sustainable” flux the 5 g/L PAC was best. All 4 systems showed lower total organic carbon (TOC) in the permeate compared to the bioreactors, but the lowest permeate TOC (and the best removal) was for the highest PAC loading.

The benefit of PAC addition was confirmed in a second series of tests with two 20 L MBRs with submerged hollow fibers, one operated without PAC, the MBR(AS), and the other with 5 g/L PAC, the MBR(BAC). For an SRT of 30 days (which involved 3.3% sludge wastage per day and 3.3% new PAC addition per day) and a fixed flux of 21 L/m²hr the MBR(AS) showed a TMP rise of about 2.4 kPa/day whereas the MBR(BAC) showed a rise of only 0.8 kPa/day. However when the MBRs were operated without wastage the performance of the MBR(BAC) was worse than the MBR(AS). Thus the improved performance of the MBR(BAC) requires regular replenishment of aged BAC with fresh PAC.     

New configuration of a membrane bioreactor for effective control of membrane fouling and nutrients removal in wastewater treatment

Excess aeration to membrane surface is common for controlling membrane fouling in a submerged membrane bioreactor (MBR) system, but significant energy is consumed for excess air production. Therefore, an alternative strategy for membrane fouling control is currently needed. A new configuration of MBR was proposed in this study to control membrane fouling effectively. To reduce biosolids concentration near the membrane surface, the position of the membrane module in MBR was elevated from the bottom to the top in the reactor. This could divide the reactor to two different zones: upper and lower zone. Air was not supplied at the lower zone whereas aeration was given to the upper zone where the membrane filtration was carried out. Biosolids concentration was reduced in the upper zone because the mixed liquor was settled down to the lower zone. Membrane fouling could be lessened in the upper zone due to the reduced biosolids concentration. Therefore, to verify if this new configuration of MBR could mitigate membrane fouling, the effect of changing vertical position of the membrane module in MBR on membrane fouling was investigated. Prior to verification the effect of elevation of membrane module on membrane fouling, influence of MLSS concentration on membrane fouling was investigated first. Transmembrane pressure (TMP) increase became steep as MLSS concentration increased. And the immersed membrane module was elevated from the bottom to the top of the MBR. When the upper membrane was located in the bioreactor, less membrane fouling was observed. This could demonstrate a possibility of new MBR design to control membrane fouling. In addition, reduced dissolved oxygen level in the returned sludge to anoxic tank could increase denitrification efficiency if this configuration is directly applied to biological nutrient removal processes.