Continuous electricity generation from domestic wastewater and organic substrates in a flat plate microbial fuel cell

A microbial fuel cell (MFC) is a device that converts organic matter to electricity using microorganisms as the biocatalyst. Most MFCs contain two electrodes separated into one or two chambers that are operated as a completely mixed reactor. In this study, a flat plate MFC (FPMFC) was designed to operate as a plug flow reactor (no mixing) using a combined electrode/proton exchange membrane (PEM) system. The reactor consisted of a single channel formed between two nonconductive plates that were separated into two halves by the electrode/PEM assembly. Each electrode was placed on an opposite side of the PEM, with the anode facing the chamber containing the liquid phase and the cathode facing a chamber containing only air. Electricity generation using the FPMFC was examined by continuously feeding a solution containing wastewater, or a specific substrate, into the anode chamber. The system was initially acclimated for 1 month using domestic wastewater orwastewater enriched with a specific substrate such as acetate. Average power density using only domestic wastewater was 72+/-1 mW/m2 at a liquid flow rate of 0.39 mL/min [42% COD (chemical oxygen demand) removal, 1.1 h HRT (hydraulic retention time)]. At a longer HRT = 4.0 h, there was 79% COD removal and an average power density of 43+/-1 mW/m2. Power output was found to be a function of wastewater strength according to a Monod-type relationship, with a half-saturation constant of Ks = 461 or 719 mg COD/L. Power generation was sustained at high rates with several organic substrates (all at approximately 1000 mg COD/L), including glucose (212+/-2 mW/ m2), acetate (286+/-3 mW/m2), butyrate (220+/-1 mW/ m2), dextran (150+/-1 mW/m2), and starch (242+/-3 mW/ m2). These results demonstrate the versatility of power generation in a MFC with a variety of organic substrates and show that power can be generated at a high rate in a continuous flow reactor system.     

High-rate aerobic treatment of winery wastewater using bioreactors with free and immobilized activated sludge

COD (chemical oxygen demand) removal rate and efficiency of winery wastewater (WW) aerobic treatments were evaluated in an air-bubble column bioreactor using self-adapted microbial populations either free or immobilized on polyurethane particles and in a packed-bed bioreactor immobilized on Raschig rings. The bioreactors were fed continuously for up to 12 months using WW of different origins and with different pollution loads (COD range, 0.8-11.0 kg.m(-3)): the maximum loading rate was approx. 8.8 kg-COD m(-3).d(-1). The highest COD removal rate (6.6 kg.m(-3).d(-1)) was obtained with free activated sludge in the bubble column bioreactor; treatment efficiency and hydraulic retention time were >90% and approx. 0.8 d, respectively. The microbial populations in the three reactors were characterized.     

改进型AGSFB处理麦草制浆中段废水

用改进型AGSFB(厌氧颗粒污泥流化床)处理麦草制浆中段废水,在常温(23±3)℃条件下,研究讨论HRT、回流比以及上升流速、容积负荷等因素对中段废水处理的影响。在停留时间为20h、回流比为5:1、上升流速为2.3m·h-1、容积负荷为0.92kgCOD·(m3·d)-1的条件下,CODCr、色度的去除率分别为53%、40%,可以有效地去除麦草浆中段废水的COD和色度。     

新型(IC)厌氧反应器处理酒厂废水的试验研究

采用新型的内循环(IC)厌氧反应器处理酒厂废水,研究了水力条件、进水方式和温度对IC厌氧反应器形成内循环和运行性能以及COD去除率的影响,进而确定IC厌氧反应器最适宜的容积负荷率。研究结果表明:最佳的进水方式是以切线方向从底部进入,这时,在一定的进水速度下,可形成缓慢的上升旋流和保持良好的内循环,从而能达到较好的污泥膨胀率和较高的COD去除率;最佳的水力停留时间为6h;最适宜的进水温度为35℃,这时的污泥膨胀率为68%,COD去除率为80%;IC厌氧反应器最适宜容积负荷率为20kg(/m3.d),此时COD去除率为80%左右。     

Membrane fouling in pilot-scale membrane bioreactors (MBRs) treating municipal wastewater

The main obstacle for wider use of membrane bioreactors (MBRs) for wastewater treatment is membrane fouling (i.e., deterioration of membrane permeability),which increases operating costs. For more efficient control of membrane fouling in MBRs, an understanding of the mechanisms of membrane fouling is important. However, there is a lack of information on membrane fouling in MBRs, especially information on features of components that are responsible for the fouling. We conducted a pilot-scale experiment using real municipal wastewater with three identical MBRs under different operating conditions. The results obtained in this study suggested that the food-microorganisms ratio (F/M) and membrane filtration flux were the important operating parameters that significantly influenced membrane fouling in MBRs. Neither concentrations of dissolved organic matter in the reactors nor viscosity of mixed liquor, which have been thought to have influences on fouling in MBRs, showed clear relationships with membrane fouling in this study. Organic substances that had caused the membrane fouling were desorbed from fouled membranes of the MBRs at the termination of the operation and were subjected to Fourier transform infrared (FTIR) and 13C nuclear magnetic resonance (NMR) analyses. These analyses revealed that the nature of the membrane foulant changes depending on F/M. It was shown that high F/M would make the foulant more proteinaceous. Carbohydrates were dominant in membrane foulants in this study, while features of humic substances were not apparent.     

Novel functionalized nano-TiO2 loading electrocatalytic membrane for oily wastewater treatment

Membrane fouling is a critical problem in membrane filtration processes for water purification. Electrocatalytic membrane reactor (ECMR) was an effective method to avoid membrane fouling and improve water quality. This study focuses on the preparation and characterization of a novel functionalized nano-TiO(2) loading electrocatalytic membrane for oily wastewater treatment. A TiO(2)/carbon membrane used in the reactor is prepared by coating TiO(2) as an electrocatalyst via a sol-gel process on a conductive microporous carbon membrane. In order to immobilize TiO(2) on the carbon membrane, the carbon membrane is first pretreated with HNO(3) to generate the oxygen-containing functional groups on its surface. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS) analyses are used to evaluate the morphology and microstructure of the membranes. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements are employed to illustrate the eletrochemical activity of the TiO(2)/carbon membrane. The membrane performance is investigated by treating oily wastewater. The oil removal rate increases with a decrease in the liquid hourly space velocity (LHSV) through the ECMR. The COD removal rate was 100% with a LHSV of 7.2 h(-1) and 87.4% with a LHSV of 21.6 h(-1) during the treatment of 200 mg/L oily water. It suggests that the synergistic effect of electrocatalytic oxidation and membrane separation in the ECMR plays a key role.     

多孔载体生物膜反应器深度处理皮革废水的试验研究

本试验采用自制多孔载体生物膜反应器对某皮革厂经物化、生化处理后的出水进行深度处理。研究结果表明:在水中溶解氧DO为2.0~3.0 mg/L,水力停留时间HRT为8 h,进水COD为176.5~256.6 mg/L、氨氮为39.2~58.9 mg/L、总氮为51.9~76.5 mg/L的条件下,经过本反应器处理之后的出水平均COD为75.8 mg/L,平均氨氮质量浓度为8.8 mg/L,平均总氮质量浓度为22.9 mg/L,出水水质达到《污水综合排放标准》(GB8978-1996)中的一级排放标准。     

Nanofiltration for the recovery of caustic cleaning-in-place solutions: robustness towards large variations of composition

In the dairy industry re-use and multi-use cleaning-in-place (CIP) systems are operated by circulating chemicals and water without taking the equipment apart. The solutions, which become polluted due to the removal of fouling compounds, are drained periodically when they are considered to be too polluted. This work shows the large variations in composition (pollution, surface tension, etc) of the industrial caustic solutions coming from milk standardization and pasteurization plant CIP throughout their life time (7 days) and from 1 week to another. The work is also intended to show how nanofiltration (1 kg mol(-1) molecular weight cut-off) was robust and performed well, with good recovery of caustic solutions, even when faced with large variations of solutions composition: high caustic yield, permeation flux (J) in the range 42-110 l h(-1) m(-2), average chemical oxygen demand (COD) reduction equal to 0.58 and low surface tension change. Equations have been established for the prediction of J as a function of initial membrane hydraulic resistance (Rm) caustic concentration, volume reduction ratio (VRR) and initial soluble COD. When VRR increased, both J and pollution retention decreased despite the increase in irreversible fouling induced by the increase of soluble pollution concentration in retentate. The higher the initial soluble COD, the sharper the decrease in J vs. VRR. Since irreversible fouling was usually small (0.1-3.4 x 10(13) m(-1), that is to say of the same order of magnitude as Rm), the membrane cleaning could be efficiently performed by using single phase sodium hypochlorite alternately with a more expensive acid-base cleaning sequence. The obtained permeate was a clear regenerated cleaning solution with low soluble COD (0.2-3.5 g/l) and surface tension (56-30 mJ m(-2)) which could be successfully exploited owing to its cleaning potential.     

正渗透膜污染的影响因素及清洗效果研究

为研究正渗透(FO)浓缩过程中的膜通量衰减规律,本文以牛血清白蛋白(BSA)为特征污染物,研究了正渗透过程中原料液的离子强度及BSA浓度、膜方位等参数不同时FO膜的污染规律,以提高膜通量和截留率为目标,对驱动液的种类、浓度,料液流速进行了优化,并优化了适宜的膜清洗方案.结果表明:原料液中离子强度越大,FO膜的初始通量越...     

Gaseous hexane biodegradation by Fusarium solani in two liquid phase packed-bed and stirred-tank bioreactors

Biofiltration of hydrophobic volatile pollutants is intrinsically limited by poor transfer of the pollutants from the gaseous to the liquid biotic phase, where biodegradation occurs. This study was conducted to evaluate the potential of silicone oil for enhancing the transport and subsequent biodegradation of hexane by the fungus Fusarium solani in various bioreactor configurations. Silicone oil was first selected among various solvents for its biocompatibility, nonbiodegradability, and good partitioning properties toward hexane. In batch tests, the use of silicone oil improved hexane specific biodegradation by approximately 60%. Subsequent biodegradation experiments were conducted in stirred-tank (1.5 L) and packed-bed (2.5 L) bioreactors fed with a constant gaseous hexane load of 180 g x m(-3)(reactor) x h(-1) and operated for 12 and 40 days, respectively. In the stirred reactors, the maximum hexane elimination capacity (EC) increased from 50 g x m(-3)(reactor) x h(-1) (removal efficiency, RE of 28%) in the control not supplied with silicone oil to 120 g x m(-3)(reactor) x h(-1) in the biphasic system (67% RE). In the packed-bed bioreactors, the maximum EC ranged from 110 (50% RE) to 180 g x m(-3)(reactor) x h(-1) (> 90% RE) in the control and two-liquid-phase systems, respectively. These results represent, to the best of our knowledge, the first reported case of fungi use in a two-liquid-phase bioreactor and the highest hexane removal capacities so far reported in biofilters.     

Enhanced treatment efficiency of an anaerobic sequencing batch reactor (ASBR) for cassava stillage with high solids content

Cassava stillage is a high strength organic wastewater with high suspended solids (SS) content. The efficiency of cassava stillage treatment using an anaerobic sequencing batch reactor (ASBR) was significantly enhanced by discharging settled sludge to maintain a lower sludge concentration (about 30 g/L) in the reactor. Three hydraulic retention times (HRTs), namely 10 d, 7.5 d, 5 d, were evaluated at this condition. The study demonstrated that at an HRT of 5 d and an organic loading rate (OLR) of 11.3 kg COD/(m³ d), the total chemical oxygen demand (TCOD) and soluble COD (SCOD) removal efficiency can still be maintained at above 80%. The settleability of digested cassava stillage was improved significantly, and thus only a small amount of settled sludge needed to be discharged to maintain the sludge concentration in the reactor. Furthermore, the performance of ASBR operated at low and high sludge concentration (about 79.5 g/L without sludge discharged) was evaluated at an HRT of 5 d. The TCOD removal efficiency and SS in the effluent were 61% and 21.9 g/L respectively at high sludge concentration, while the values were 85.1% and 2.4 g/L at low sludge concentration. Therefore, low sludge concentration is recommended for ASBR treating cassava stillage at an HRT 5 d due to lower TCOD and SS in the effluent, which could facilitate post-treatment.     

Wastewater treatment with bacteria immobilized onto a ceramic carrier in an aerated system

Biological treatment of the wastewater discharged from a food processing factory was continuously carried out in a packed bed bioreactor under aerobic conditions. The bacterium isolated from the wastewater was immobilized onto a new type of ceramic carrier by a vacuum method and high numbers of bacteria were colonized onto the carrier (2.9 x 10(9) cfu/g of dry ceramic carrier). The effect of the hydraulic retention time (HRT) and aeration rate on the removal of the chemical oxygen demand (COD) was investigated. The system was able on average to remove more than 82% of the influent COD during 160 d of operation and more than 87% of the influent COD on average was removed when the HRT was 30.17 h and the aeration rate was 2.0 vvm. Aeration rates in the range of 0.4 to 2.0 vvm do not affect the COD removal efficiency.     

浮石和碎石填料的厌氧过滤塔对果胶废水处理的比较

<正> 前言 长期以来,水果加工厂的废水均含有高浓度的BOD。采用生物厌氧过滤塔法进行废水的前处理,可以大大降低废水处理的总费用。 厌氧过滤塔是一种高效率的生物反应器。水中的有机物在反应器内被吸附在填料表面或游离在填料之间的微生物所分解。然而关于厌氧过滤塔填料种类对果胶等有机废水处理效果的影响等问题却很少为人所知。本文对浮石和碎石填料的上层排放式厌氧过滤塔原理、处理方法和能力进行了研究。     

Membrane-aerated biofilm reactor for the treatment of acetonitrile wastewater

A membrane-aerated biofilm reactor (MABR) was studied for the treatment of wastewater containing acetonitrile, a typical organonitrile compound. The MABR used hydrophobic hollow fiber membranes as the diffusers for bubbleless aeration as well as the carriers for biofilm growth. The objectives were to prevent the stripping-loss of acetonitrile during aeration and to achieve acetonitrile biodegradation plus nitrogen removal simultaneously in a single biolfilm on the membranes. In the MABR, oxygen and substrates were supplied to the biofilm from opposite sides, in contrast to those from the same side in conventional biofilm bioreactors. Operational factors, including surface loading rate and upflow fluid velocity in the bioreactor, on the effect of acetonitrile biodegradation performance were examined. The profiles of dissolved oxygen concentration and microbial activities and populations in the biofilm were investigated. Experimental results showed that, with the adapted microorganisms, removal of acetonitrile at approximately 98.6 and 83.3%, in terms of total organic carbon and total nitrogen, were achieved at a surface loading rate (in terms of membrane surface) of up to 11.29 g acetonitrile/ m2 x d with an upflow fluid velocity of 12 cm/s and a hydraulic retention time of 30 h. The biofilm on the membranes developed an average thickness of about 1.6 mm in the steady state and consisted of oxic/anoxic/anaerobic zones that provided different functions for acetonitrile degradation, nitrification, and denitrification. The acetonitrile-degrading bacteria in the MABR appeared to secrete more extracellular polymeric substances that enhanced the attachment and development of the biofilm on the membranes. The study demonstrated the potential of using the MABR for the treatment of organonitrile wastewater.     

Interrelated effects of aeration and mixed liquor fractions on membrane fouling for submerged membrane bioreactor processes in wastewater treatment

The interactions of mixed liquor fractions and their impacts on membrane fouling were examined at different sparging aeration intensities for submerged hollow-fiber membrane bioreactors (MBR) in wastewater treatment. The mixed liquor samples were fractioned by size into MLSS, colloids quantified by colloidal TOC, and dissolved solutes. The experimental results showed that their significance in membrane fouling was strongly related to aeration intensity. In the absence of sparging aeration, both MLSS and colloids contributed to membrane fouling which was further enhanced by their interactions. For the tested membrane module operated at the vigorous aeration intensity typically employed in practice, however, the deposition of colloids was identified as the most important mechanism controlling membrane fouling rates. In contrast, much fewer effects were exerted by MLSS: the overall fouling rates were increased initially, and then reduced with increasing concentration of MLSS. Thus, the aeration-induced turbulence should be considered for properly assessing the mixed liquor fouling potential for wastewater MBR processes. Finally, little difference in fouling rates was observed with the use of cyclic aeration mode as compared to continuous aeration mode.     

立体式厌氧/好氧反应池处理垃圾渗滤液的工程应用

介绍了某垃圾焚烧发电厂渗滤液厌氧出水的处理工程,采用立体式厌氧/好氧反应池处理工艺。对反应池启动和调试过程中污染物的去除效果进行了分析。结果表明,当处理负荷为COD 1.8 kg/(m3·d)和NH3-N 0.36 kg/(m3·d)左右时,出水COD和NH3-N质量浓度分别低于1 900 mg/L和180 mg/L,两者去除率分别高达80%和90%左右。经过120 d满负荷运行,反应池展现出较好的抗冲击负荷能力,出水指标均达到设计要求,经过后续MBR处理可以达到3级排放标准。该工程能够有效节约占地面积。     

Characterization of cake layer in submerged membrane bioreactor

Cake layer formation on the membrane surface has been a major challenge in the operation of membrane bioreactors (MBRs). In this study, the cake layer formation mechanism in an MBR used for synthetic wastewater treatment was investigated. The major components of cake layer were systematically examined by particle size analyzer (PSA), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray fluorescence (XRF), energy-diffusive X-ray analyzer (EDX), and Fourier transform infrared (FTIR) spectroscopy. The results indicate that the small particles in sludge suspension had a strong deposit tendency on the membrane surface. The SEM and CLSM analysis exhibited that bacterial clusters and polysaccharides were significant contributors to membrane fouling. The main components of biopolymers were identified as proteins and polysaccharide materials by the FTIR. The examination by EDX and XRF demonstrated that Mg, Al, Ca, Si, and Fe were the major inorganic elements in fouling cake. Furthermore, the results suggest that bridging between deposited biopolymers and inorganic compounds could enhance the compactness of fouling layer. During the operation of MBRs, the biopolymers and inorganic elements in the bioreactor should be controlled to minimize membrane fouling.     

厌氧接触-膜生物反应器处理白酒黄水的研究

对发酵培养菌丝体后的黄水利用厌氧接触-膜生物反应器工艺进行了试验研究.结果表明,进水CODCr浓度为10.03g/L～14.36g/L时,厌氧接触池对废水CODCr的去除率为53.5%～69.6%;厌氧反应停留时间14h～16h较为合适.溶氧控制在2.0mg/L～3.5mg/L,MBR对CODCr去除率在91.4%以上,出水CODCr210.65mg/L～277.89mg/L,NH3-N去除率37.3%～54.2%;MBR对CODCrNH3-N的去除率随污泥浓度的增大先增加后减少,合适的MLSS值应控制在8g/L～10g/L.     

有机负荷对CSTR-UASB两相厌氧系统的影响

采用连续流CSTR-UASB两相厌氧反应装置,CSTR以人工配制的红糖水作为发酵底物,其液相末端产物作为UASB的反应底物,污水处理厂剩余污泥作为反应器的启动污泥,反应器实现稳定运行（CSTR为乙醇型发酵）后,在其它参数不变的情况下,通过改变有机负荷,研究其对CSTR-UASB两相厌氧系统的影响.有机负荷从12 kg/（m^3·d）提升至32 kg/（m^3·d）的过程分为六个阶段,结果表明厌氧活性污泥产氢能力持续升高,在有机负荷为32 kg/（m^3·d）时,最大产氢量为12.8L/d,较初始有机负荷12 kg/（m^3·d）时提高了71.9％;产甲烷量随有机负荷的升高先增大后减小,在有机负荷为24 kg/（m^3·d）时,最大产甲烷量为18.5L/d;当有机负荷提高至28 kg/（m^3·d）时,总COD去除率达最大值72％.因此,CSTR-UASB两相厌氧系统对红糖废水具有较好的降解效果,同时能源回收效率较高.     

超滤/纳滤技术深度处理肠衣废水的研究

采用超滤/纳滤技术对肠衣废水进行深度处理,研究操作压力和处理时间对膜性能的影响。结果表明,适宜的超滤压力为0.25MPa,运行1h后,肠衣废水的COD(chemical oxy-gen demand)、BOD(biochemical oxygen demand)的平均去除率分别大于60%和35%,平均膜通量大于580L/(m2.h);适宜的纳滤压力为1.4～1.6MPa,连续运行3h后,肠衣废水COD、BOD和氯离子的平均去除率分别大于70%、90%和98%,平均膜通量大于60L/(m2.h);最终出水的水质可以达到中水回用的要求。