垃圾焚烧厂渗滤液处理设施运行优化

好氧膜生物反应器(MBR)工艺是垃圾焚烧厂处理渗滤液的常用工艺之一,使用中膜污染及膜通量下降是制约MBR系统处理能力的主要因素。该文分析了上海某垃圾焚烧厂渗滤液处理设施、处理效果及实际影响因素,对离心出水的可行性进行了理论分析和试验研究,并提出了切实可行的运行优化方案,有效缓解了膜污染及膜通量下降等问题对整个MBR系统处理能力的制约。     

水解酸化-膜生物反应器处理印染废水的试验研究

研究了水解酸化与膜生物反应器组合工艺对印染废水的处理效能。当进水CODCr为3500～4500mg/L、NH4+-N为55～60mg/L、色度为600倍时,经UASB-MBR系统处理后出水CODCr为120～150mg/L、NH4+-N为4～8mg/L、色度小于50倍,出水水质达到《纺织染整工业水污染物排放标准》的一级标准要求。试验结果表明,UASB-MBR系统运行良好,用于印染废水处理是可行的。     

A/A/O-MBR组合工艺强化去除氨氮及其硝化速率

将PVDF帘式中空纤维膜组件与A/A/O工艺结合,构建"A/A/O-MBR"强化生物脱氮的中试系统,用于处理太湖流域城镇污水。针对组合工艺的脱氮效果,以组合工艺MBR池内活性污泥的硝化速率为研究对象,分析了溶解氧(DO)浓度、进水氨氮浓度和温度对硝化速率的影响。结果表明,组合工艺在夏季和冬季的氨氮平均去除率分别稳定为96.56%和96.68%;低温(T15℃)条件下,进水氨氮浓度对硝化速率影响不大;温度升高硝化速率加快,温度为30.5℃时组合工艺的硝化速率为11.8℃时的2.6倍;与常规工艺相比,组合工艺的硝化速率是氧化沟工艺的2.3倍。组合工艺两级硝化空间形成的较长水力停留时间和MBR内膜的截留作用补偿了低温对硝化速率的影响。     

Study of a membrane bioreactor with glass fiber flat grille modules and the modules' optimization based on the local critical flux theory

A novel flat grille membrane module using inorganic glass fibers as filter media is proposed for use in a membrane bioreactor for wastewater treatment. A model which integrates the concepts of back transport velocity, spatial local critical flux and temporal variation of the local flux has been developed. The membrane module was optimized based on experimental results and calculations using the model. The optimized parameters include the volume ratio of membrane solution for the surface modification of glass fibers, the fiber inner diameter and fiber length. The optimal values were 1:2 and 5 mm respectively but the length had little effect on the performance of the module. The critical time was then calculated with the model and an equation developed. The result was in very good agreement with the observed one. Finally, the performance of the glass fiber MBR was monitored. The effluent quality and stability of the system were comparable to that of conventional MBRs. This MBR will be a promising technique for wastewater treatment given its low cost, high strength and good effluent quality.     

Effect of disintegrated sludge recycling on membrane permeability in a membrane bioreactor combined with a turbulent jet flow ozone contactor

We have combined a turbulent jet flow ozone contactor (TJC) with a membrane bioreactor (MBR) to establish a zero-discharge system in terms of excess sludge in the MBR. The TJC-MBR system was compared with the conventional MBR (Control-MBR) with respect to i) the size and zeta potential of the sludge particles, ii) the loosely bound extra-cellular polymeric substances (EPSs) and tightly bound EPS of the microbial flocs, iii) the porosity and biovolume of the bio-cake accumulated on the membrane, and iv) the membrane permeability. The TJC system generated the ozonated sludge with a negligible amount of loosely bound EPS and a positive zeta potential. As a result, when such ozonated sludge was recycled, the average size of the sludge particles (e.g., microbial flocs) increased in the TJC-MBR. Consequently the bio-cake formed in the TJC-MBR had greater porosity than that in the Control-MBR, giving rise to higher membrane permeability in the TJC-MBR.     

Activated sludge model (ASM) based modelling of membrane bioreactor (MBR) processes: A critical review with special regard to MBR specificities

Membrane bioreactors (MBRs) have been increasingly employed for municipal and industrial wastewater treatment in the last decade. The efforts for modelling of such wastewater treatment systems have always targeted either the biological processes (treatment quality target) as well as the various aspects of engineering (cost effective design and operation). The development of Activated Sludge Models (ASM) was an important evolution in the modelling of Conventional Activated Sludge (CAS) processes and their use is now very well established. However, although they were initially developed to describe CAS processes, they have simply been transferred and applied to MBR processes. Recent studies on MBR biological processes have reported several crucial specificities: medium to very high sludge retention times, high mixed liquor concentration, accumulation of soluble microbial products (SMP) rejected by the membrane filtration step, and high aeration rates for scouring purposes. These aspects raise the question as to what extent the ASM framework is applicable to MBR processes. Several studies highlighting some of the aforementioned issues are scattered through the literature. Hence, through a concise and structured overview of the past developments and current state-of-the-art in biological modelling of MBR, this review explores ASM-based modelling applied to MBR processes. The work aims to synthesize previous studies and differentiates between unmodified and modified applications of ASM to MBR. Particular emphasis is placed on influent fractionation, biokinetics, and soluble microbial products (SMPs)/exo-polymeric substances (EPS) modelling, and suggestions are put forward as to good modelling practice with regard to MBR modelling both for end-users and academia. A last section highlights shortcomings and future needs for improved biological modelling of MBR processes.     

A new membrane bioreactor generation for wastewater treatment application: Strategy of membrane aeration management by sequencing aeration cycles

Polymem is developing in the past few years a new membrane bioreactor concept using external module membranes. The membranes are hollow fibers. They are housed in carters and work in outside/in filtration mode. Permanent air scouring is provided at the bottom of the module to control the accumulation of sludge on the membrane surface. In other words, the membrane carters look like bubble columns with hollow fiber membranes inside.The main advantages of this concept are the easy maintenance of the external modules; the total independence of the bioreactor from the membrane filtration part, which facilitates plant retrofitting and upgrading; the high membrane compacity (up to 500 m²/m3), and better efficiency of membrane air scouring thanks to a dedicated coarse bubbles aeration system inside the module vessel.The first part of this paper deals with the quantification of the specific aeration demand of the system. Aeration demand was compared to conventional MBR systems. The study shows that with this optimised geometry of module concept, the aeration flow rate is lowered compared with conventional processes.In the second part of this paper, an optimisation of the aeration demand was carried out by sequencing the cycle of aeration by incorporating a syncope in the aeration. Ratios of the time-on and time-off from 1/2 to 1/5 were tested for various instantaneous aeration flow rates. Impacts on both short term fouling and long term fouling were evaluated and quantified in terms of permeability decrease. The advantages of the location of the membrane in an external cylindrical carter have been demonstrated in terms of operating cost savings with a reduction of specific aeration demand for membranes scouring at 100 to 250 Nl/h m², which is half the classical consumption of the submerged MBR today.     

Optimising mixing and nutrient removal in membrane bioreactors: CFD modelling and experimental validation

Membrane Bioreactors (MBRs) have been used successfully in biological wastewater treatment to solve the perennial problem of effective solids-liquid separation. The optimisation of MBRs requires knowledge of the membrane fouling, mixing and biokinetics. MBRs are designed mainly based on the biokinetic and membrane fouling considerations even though the hydrodynamics within an MBR system is of critical importance to the performance of the system. Current methods of design for a desired flow regime within the MBR are largely based on empirical techniques (e.g. specific mixing energy). However, it is difficult to predict how vessel design in large scale installations (e.g. size and position of inlets, baffles or membrane orientation) affects hydrodynamics, hence overall performance. Computational Fluid Dynamics (CFD) provides a method for prediction of how vessel features and mixing energy usage affect the hydrodynamics and pollutant removal and subsequently allowing optimisation of MBR design and performance. In this study, a CFD model was developed which accounts for aeration and biological nutrient removal. The modelling results are compared against experimental results of two full scale MBRs for the hydrodynamics and against a modelling benchmark for the biological nutrient removal component of the model.     

Greywater recycling in Vietnam — Application of the HUBER MBR process

Greywater is the part of domestic wastewater that is free of faeces. The volume and concentration of this separately collected wastewater flow depend on the consumer behaviour and vary according to its source. The average amount of greywater produced per day in a German household is 70 l per person, which is more than 50% of the total wastewater production [5]. This figure corresponds with the average figures provided for Chinese households (80 l per person/day, GB/T 50331-2002), but significantly exceeds the South African average of 20 l per person and day [1].Compared to domestic wastewater, greywater generally contains less organic pollutants, less nutrients but a high amount of tensides. The effluent from bath tubs, showers or wash hand basins contains for example a by approx. two decimal orders lower number of total and faecal coliform bacteria (Escherichiacoli) [2] and [6].Due to its relatively low content of pollutants, greywater is easy to treat with MBRs. The pollutants contained are decomposed by the bacteria of the activated sludge tank. The following membrane filtration unit separates the treated greywater from the activated sludge. The treated greywater is of high quality and hygienically safe so that it can be reused, alone or combined with rain water, for toilet flushing water, laundry washing or for irrigation purposes.Within the scope of the SANSED II research project HUBER has been successful in adapting the MBR system for greywater treatment to the specific conditions in Vietnam and testing the system in operation in a small city in the Mekong delta, South Vietnam. The wastewater from kitchen sinks and the bathrooms of a dormitory on the campus of Can Tho University was clarified in the HUBER GreyUse^® plant over a period of three months. The project aim was the production of high quality service water from greywater for safe reuse as toilet flush water.     

Application of MBR for hospital wastewater treatment in China

In China, the number of hospitals has increased to 19,712 in 2008, with the production of hospital wastewater reaching 1.29 × 10⁶ m³/d. Membrane bioreactor (MBR) technology presents a more efficient system at removing pathological microorganism compared with existing wastewater treatment systems. In the past 8 yr, over 50 MBR plants have been successfully built for hospital wastewater treatments, with the capacity ranging from 20 to 2000 m³/d. MBR can effectively save disinfectant consumption (chlorine addition can decrease to 1.0 mg/L), shorten the reaction time (approximately 1.5 min, 2.5-5% of conventional wastewater treatment process), and attain a good effect of inactivation of microorganism. Higher disinfection efficacy is achieved in MBR effluents at lower dose of disinfectant with less disinfection by-products (DBPs). Moreover, when capacity of MBR plants increases from 20 to 1000 m³/d, their operating cost decreases sharply.