Comparison of nitrification performance and microbial community between submerged membrane bioreactor and conventional activated sludge system.

A submerged membrane bioreactor (SMBR) and a conventional activated sludge system (CAS) were compared in parallel over a period of more than 260 days on treating synthetic ammonia-bearing inorganic wastewater without sludge purge under decreased hydraulic retention times (HRTs). Conversion of NH4(+)-N to NO3(-)-N was achieved with an efficiency of over 98% at an HRT > or = 10 h in the SMBR, while similar performance was obtained at an HRT > or = 20 h in the CAS. Denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplified 16S rDNA was used to monitor variations of community structures in the two systems. With the prolongation of operation, the number of DGGE bands in the SMBR gradually increased from the initial 11 bands to the final 22 bands, whereas that in the CAS varied in a range between 13 and 183 Sequence analysis indicates that Nitrosomonas sp. and Nitrospira sp. were the dominating nitrification species responsible for ammonia and nitrite oxidation, respectively. Heterotrophic bacteria like Pseudomonas sp. and Flavobacteria sp. existed in both of the systems although only inorganic wastewater was fed. Substantive accumulation of extracellular polymeric substances (EPS) in the SMBR was confirmed by scanning electron microscopy and EPS analysis.     

循环式活性污泥法工程设计方法探讨

分析了CASS与CAST工艺的异同点,指出SBR工艺可以模拟多种不同的连续处理工艺,而CAST可以根据连续流A2/O工艺的设计方法进行设计.通过定义(进水 反应)阶段占每个运行周期的比例(§),引入有效污泥龄与有效水力停留时间的概念,分析了CAST同步硝化反硝化功能对主反应区DO的控制要求及对好氧SRT的影响,推荐采用CAST处理城市污水时使用经验值θc厌∶θc缺∶θc好=1∶2∶17;强调系统生物量的衰减由系统总SRT决定,调整(§)即可调整总污泥龄,并影响总产率系数.最后,给出了设计步骤和计算实例.当采用平均日流量设计时,建议采用较长的运行周期(6 h),便于在峰值流量时增加周期数,以保持CAST运行的灵活性.     

Nitrogen removal and sludge reduction in a symbiotic activated sludge system between anaerobic archaea and bacteria.

The possible symbiosis between bacteria and anaerobic archaea was investigated in intermittent aeration (I/A) systems. Archaea solution added to I/A reactor might play an important role in biological activities as well as in improvement of mineralization of organic matter. I/A reactor with archaea solution (I/A-arch) could increase both nitrification and denitrification rate and also reduce the sludge yield remarkably. These results indicate the possibility of the symbiotic activated sludge system with anaerobic archaea by controlling the DO level in the aeration tank. In this study, DO was controlled by intermittent aeration schemes and a successful symbiotic activated sludge system was achieved to reach the following conclusions. 1) SOUR of I/A-arch system was 2.9 mg-O2/g-VSS x min. SOUR and nitrification rate of the sludge from I/A-arch was higher than those from the I/A and A/S reactors. 2) Removal efficiencies of organic matter (TCOD(Cr)) in I/A-arch, I/A and conventional activated sludge (A/S) reactors were 93, 90 and 87%, respectively. 3) Nitrification occurred successfully in each reactor, while denitrification rate was much higher in the I/A-arch reactor. Efficiencies of TN removal in A/I-arch, I/A and A/S reactors were 75, 63 and 33%, respectively. 4) Observed yield coefficients of I/A-arch, I/A and A/S reactors were 0.28, 0.41 and 0.37 g-VSS/g-COD.     

Fe3+对活性污泥系统的影响

通过小试研究了微量Fe3+对活性污泥系统的影响.将浓度为3 mg/L,5 mg/L,10 mg/L,20 mg/L,30 mg/L,50 mg/L和80 mg/L的Fe3+分别投加到活性污泥系统中,反应4 h后测定系统出水COD、活性污泥的SVI、脱氢酶活性及其EPS组分.结果表明,Fe3+浓度小于50 mg/L时对活性污泥的脱氢酶活性具有促进作用,浓度为10 mg/L时促进作用最强;Fe3+浓度在80 mg/L以下均具有良好的絮凝作用,浓度在30 mg/L以下时絮凝作用最强.两种作用的共同结果影响系统对COD的去除效果.对活性污泥EPS组分的测定表明,Fe3+的絮凝作用对SVI的影响是主要的.     

非线性规划在活性污泥法系统方案优化设计中的应用

将常规的活性污泥法工艺系统方案设计过程整合为一个最优化的非线性规划问题 ,提出了一种活性污泥法工艺方案的最优化设计方法。对优化原理、寻优求解的序列二次规划方法 (SQP)以及其Matlab的实现方法进行了介绍。设计算例表明 ,经优化后的设计方案较之传统的设计方案 ,在满足出水水质标准的基础上 ,可极大提高设计方案的经济可行性。     

生物捕食污泥减量化系统的污泥特性

通过中试分析了以减量化为目的的微型动物捕食系统中活性污泥的特性.结果表明,细菌分散培养段的悬浮污泥浓度比原生动物捕食段约高15%,比大型微型动物捕食段约高40%;微型动物的捕食作用在减少剩余污泥产率的同时,可以提高悬浮污泥的沉降性能约36%,轮虫可作为该系统污泥沉降性能的指示生物;低底物浓度下,大型微型动物的捕食活动可以增强污泥的活性.     

SBBR自养型短程硝化的实现及其影响因素研究

采用序批式生物膜反应器(SBBR)以及模拟无碳源的理想生活污水,对系统内各参数进行反复调试,在一个月内实现了自养型短程硝化系统的启动,氨氮去除率为98%,亚硝态氮积累率为95.29%。当温度控制在20～35℃时都会实现短程硝化,而30℃时短程硝化的效果最佳;系统其他条件不变的情况下DO为1.5 mg/L时,短程硝化的效果最好;系统具有一定的承受有机负荷的能力,在进水中外加COD_(Cr)浓度不超过75 mg/L时,不会对系统产生影响且COD_(Cr)的去除率为50%。     

A pilot study on a step-feeding anoxic/oxic activated sludge system.

A four stage pilot plant of step-feed biological nutrient removal (BNR) was employed to investigate reactor performance and process stability. The results obtained showed that step-feed BNR is efficient and cost-effective for nitrogen and carbonaceous removal from municipal wastewater. The total average removal efficiencies of COD, NH3-N, TN and TP could reach as high as 89.5, 97.8, 73 and 75%, respectively, with 50% of return activated sludge (RAS), 9 h of hydraulic retention time (HRT) and 20 d of sludge retention time (SRT). Step-feed BNR is an alternative and effective technology of nutrient removal for municipal wastewater treatment.     

Analysing sludge balance in activated sludge systems with a novel mass transport model

In activated sludge systems the mechanically treated wastewater is biologically cleaned by biomass (activated sludge). The basic requirement of an efficient biological wastewater treatment is to have as a high biomass concentration in the biological reactor (BR) as possible. The activated sludge balance in activated sludge systems is controlled by the settling, thickening, scraper mechanism in the secondary settling tank (SST) and sludge returning. These processes aim at keeping maximum sludge mass in the BR and minimum sludge mass in the SST even in peak flow events (storm water flow). It can be, however, only reached by a high SST performance. The main physical processes and boundary conditions such as inhomogeneous turbulent flow, geometrical features of the SST, wastewater treatment plant (WWTP) load, return sludge flow, sludge volume index etc. all influence settling thickening and sludge returning. In the paper a novel mass transport model of an activated sludge system is presented which involves a 2-dimensional SST model coupled with a mixed reactor model of the biological reactor. It makes possible to investigate different sludge returning strategies and their influence on the sludge balance of the investigated activated sludge system, furthermore, the processes determining the flow and concentration patterns in the SST. The paper gives an overview on the first promising model results of a prevailing peak flow event investigation at the WWTP of Graz.     

Short circuiting in a denitrifying activated sludge tank.

The presence of a short circuit flow in a denitrifying activated sludge tank was identified and modelled. Tracer tests with pulse addition of lithium salt were used to investigate the hydraulics of the tank. The lithium concentration in the effluent was detected and residence time distribution (RTD) curves were generated. Hydraulic models based on completely stirred tank reactors (CSTRs) in series were generated from the RTD curves and the models were compared. The short circuit problem was successfully described using the Martin model, where the inflow is divided into two strands. Each strand was modelled as a number of CSTRs in series. At a normal flow the results of the model show that the tank has 12.8% dead volume, 85.8% main volume and 1.3% short circuiting volume. The inflow was divided into 91.9% entering the main volume and 8.1% entering the short circuiting volume. The mean velocity of the short circuiting stream was estimated to 0.4 m/s. At maximum flow the short circuiting stream was even larger and handled 24.3% of the flow. The short circuiting stream was identified in the upper part of the tank due to the position of the inlet and the outlet. The configuration of a tank including the use of baffles, the geometry of the inlet and mixer configuration should be considered carefully if short circuiting is to be avoided.     

Co-conditioning and dewatering of alum sludge and waste activated sludge.

Co-conditioning and dewatering behaviors of alum sludge and waste activated sludge were investigated. Two different sludges were mixed at various ratios (2:1; 1:1; 1:2; 1:4) for study. Capillary suction time (CST) and specific resistance to filtration (SRF) were utilized to assess sludge dewaterability. Relatively speaking, waste activated sludge, though of higher solid content, was more difficult to be dewatered than alum sludge. It was found that sludge dewaterability and settlability became better with increasing fraction of alum sludge in the mixed sludge. Dosage required of the cationic polyelectrolyte (KP-201C) for dewatering was reduced as well. It is proposed that alum sludge acts as skeleton builder in the mixed sludge, and renders the mixed sludge more incompressible which is beneficial for sludge dewatering. Implications of the results of the study to the sludge management plan for Taipei City that generates both alum sludge and waste activated sludge at significant amount are also discussed. The current sludge treatment and disposal plan in Metropolitan Taipei could be made more cost-effective.     

多级高浓度活性污泥法脱氮除磷中试研究

多级高浓度活性污泥法在不征地、不增加处理构筑物的情况下,以提高活性污泥浓度为指导思想,对现有城市污水处理厂进行升级改造,达到脱氮除磷的目的。中试研究表明,在试验条件下,出水CODCr为33～43mg/L,去除率92%左右;NH3-N为3～5mg/L,去除率90%左右;TP为1～1.7mg/L,去除率72%左右。系统保证了良好的脱氮除磷效果。     

Dynamical modelling of an activated sludge system of a petrochemical plant operating at high temperatures.

The Mexican petrochemical industry, Morelos S.A. de C.V., is one of the biggest and more important petroleum industries in Mexico and Latin America. It has an activated sludge system to treat its wastewater flow, which is approximately 7,000 m3/d. The wastewater contains volatile organic carbon substances classified as toxics. The old surface aeration system was changed for fine bubble diffusers; however, one major drawback of the new aeration system is that the temperature in the bioreactor has increased due to the compression of the air, which at the compressor exit reaches 85 degrees C. This effect results in the temperature in the bioreactor attaining 32 degrees C during the fall, whereas in the spring and summer, the bioreactor temperature reaches higher values than 40 degrees C. The high temperatures reduce the microorganism activity and cause a higher volatilisation rate of volatile compounds, among other effects, which affect the performance of the biological treatment. This work was performed to obtain a better modelling of the wastewater treatment from the petrochemical industry. The model describes the effect of the temperature on the performance of the biological treatment. The model was obtained from tests that were carried out in laboratory reactors with 14 L capacity, which were operated at different temperatures (from 30 to 45 degrees C), with the same wastewater and conditions as the actual system.     

Protein analysis as a measure of active biomass in activated sludge

Conventional methods to determine the biomass in activated sludge are the measurement of total suspended solids (TSS) and volatile suspended solids (VSS). Such methods do not distinguish between active biomass and inactive organic material. In this study, biomass was determined with both conventional methods and also through measuring the protein content with the modified Lowry method. In order to investigate the relationship between activity and biomass concentration in terms of TSS, VSS and protein content, some starvation experiments were conducted. It was found that the protein fraction of VSS differs under different starvation conditions. The biological activity of the activated sludge was measured as oxygen uptake rate (OUR). The strongest correlation could be measured between protein and OUR under various conditions. The results show that protein is an appropriate parameter for the measurement of the biological activity.     

Dynamics of dewaterability and bacterial populations in activated sludge

Relationships of bacterial populations and extracellular polymer substances (EPS) to dewaterability of activated sludge were studied on three laboratory-scale activated sludge reactors fed with synthetic wastewater. Dewaterability of activated sludge was evaluated by a novel method developed by the authors, in which small amount of sludge was centrifugally dewatered, and its water content was measured. Bacterial populations during the reactor operation were analyzed by the polymerase chain reaction/terminal-restriction fragment length polymorphism (PCR/T-RFLP) targeted at a partial 16S rRNA gene. Extracellular polymeric substances (EPS) were extracted using cation exchange resin (CER), and polysaccharides and total protein in EPS were determined. Some of the dominant terminal-restriction fragments (T-RFs) were observed to have significant relationships with dewaterability of sludge, and it was suggested that bacterial species corresponding to those peaks significantly affected dewaterability. On the other hand, significant relationships were not found between EPS concentration and dewaterability of sludge.     

Potential of activated sludge ozonation.

The disposal of sewage sludge and the agricultural use of stabilised sludge are decreasing due to more stringent regulations in Europe. An increasing fraction of sewage sludge must therefore be dewatered, dried, incinerated and the ashes disposed of in landfills. These processes are cost-intensive and also lead to the loss of the valuable phosphate resources incorporated in the sludge ash. The implementation of processes that could reduce excess sludge production and recycle phosphate is therefore recommended. Partial ozonation of the return sludge of an activated sludge system significantly reduces excess sludge production, improves the settling properties of the sludge and reduces bulking and scumming. The solubilised COD will also improve denitrification if the treated sludge is recycled to the anoxic zone. However, ozonation partly kills nitrifiers and could therefore lead to a decrease of the effective solid retention time of the nitrifier, thus reducing the safety of the nitrification. This paper discusses the effect of ozonation on sludge reduction, the operating stability of nitrification, the improvement of denitrification and also presents an energy and cost evaluation.     

Potential of activated sludge disintegration.

The disposal of sewage sludge and the agricultural use of stabilised sludge are decreasing due to more stringent regulations in Europe. An increasing fraction of sewage sludge must therefore be dewatered, dried, incinerated and the ashes disposed of in landfills. These processes are cost-intensive and also lead to the loss of valuable phosphate resources incorporated in the sludge ash. The implementation of processes that could reduce excess sludge production and recycle phosphate is therefore recommended. Disintegration of biological sludge by mechanical, thermal and physical methods could significantly reduce excess sludge production, improve the settling properties of the sludge and reduce bulking and scumming. The solubilised COD could also improve denitrification if the treated sludge is recycled to the anoxic zone. However, disintegration partly inhibits and kills nitrifiers and could therefore shorten their effective solid retention time, thus reducing the safety of the nitrification. This paper discusses the potential of disintegration on sludge reduction, the operating stability of nitrification, the improvement of denitrification and also presents an energy and cost evaluation.     

基于LabVIEW的推流式活性污泥法动态仿真研究

介绍了利用LabVIEW6.1及其数学子模板中一阶微分方程组的龙格库塔算法函数,根据活性污泥法1号数学模型一阶微分方程组的特征,开发出适用于推流式活性污泥法仿真系统的方法。应用该仿真系统模拟了重庆某污水处理厂的实际运行记录,结果表明仿真效果良好。该方法降低了软件的编程难度。     

Simultaneous biological removal of sulphide and nitrate by autotrophic denitrification in an activated sludge system.

The feasibility of an autotrophic denitrification process in an activated sludge reactor, using sulphide as the electron donor, was tested for simultaneous denitrification and sulphide removal. The reactor was operated at nitrate (N) to sulphide (S) ratios between 0.5 and 0.9 to evaluate their effect on the N-removal efficiency, the S-removal efficiency and the product formation during anoxic oxidation of sulphide. One hundred per cent removal of both nitrate and sulphide was achieved at a NLR of 7.96 mmol N-L(-1) x d(-1) (111.44 mg NO3- -N x L(-1) x d(-1)) and at a N/S ratio of 0.89 with complete oxidation of sulphide to sulphate. The oxygen level in the reactor (10%) was found to influence the N-removal efficiency by inhibiting the denitrification process. Moreover, chemical (or biological) oxidation of sulphide with oxygen occurred, resulting in a loss of the electron donor. FISH analysis was carried out to study the microbial population in the system.     

活性污泥水解技术的发展与应用

如何在进水中易生物降解有机物(rbCOD)和挥发性脂肪酸(VFAs)低的情况下实现污水的强化生物脱氮除磷,是当今污水生物处理工艺中的一个难题.介绍了一种在丹麦有良好应用的新工艺--活性污泥水解技术,在阐述其工艺原理的基础上,分析了该技术的应用类型、影响因素以及在丹麦污水处理厂中的应用情况,并指出其在我国的应用前景.