计算机模拟在大型污水处理厂升级改造中的应用研究

以ASM1模型为理论基础,利用经参数校准后的GPS-X计算机模拟软件,结合天津市某污水处理厂工艺现状及新的污水排放标准要求,对悬浮填料生物膜A/O工艺、三级A/O工艺及两点进水三级A/O工艺等几种可能的升级改造方案进行模拟分析。基于计算机模拟结果,提出了能够达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级排放标准的改造方案。     

多模式A~2/O工艺的内涵分析与优化

多模式A2/O工艺是我国工程技术人员总结开发,并且应用较为广泛的污水处理工艺。典型的多模式A2/O工艺通常包括正置A2/O和倒置A2/O两种模式,但是由于不同工作模式的应用条件并没有明确的界定,使得设计和运行人员无法全面认识这一集成性很高的工艺,导致多模式A2/O工艺的处理能力得不到充分的发挥。从多模式A2/O工艺开发思路的源头出发,通过深入分析多模式A2/O工艺的内涵,确定多模式A2/O工艺的设计和运行要点,并结合ASM2D仿真模拟平台,构建完整的多模式A2/O优化运行策略。     

浅析几种城市污水处理工艺

针对城市污水的特点,根据污水处理工艺时应遵循的原则,介绍了城市污水处理的A2/O工艺、AB法工艺、卡鲁塞尔氧化沟工艺、改良的SBR类工艺、生物曝气过滤工艺、一体化氧化沟工艺、奥贝尔氧化沟工艺等7种常用城市污水处理工艺原理、工艺流程,并对各种工艺的优缺点进行了分析.     

基于ASM2D模型对龙王嘴污水处理厂的工艺模拟

目前比较成熟的包括脱氮除磷过程的活性污泥模型为ASM2D,但该模型由于参数和过程较多,限制其应用于实际污水处理工艺中。以ASM2D模型为基础,对采用改良型A2/O工艺的武汉市龙王嘴污水处理厂进行稳态和动态模拟。通过调整进水组分百分比与参数,在应用Matlab/Simulink软件后,所得仿真结果与实测值均较吻合,成功验证了模型的有效性与实用性,并可在此基础上实现对污水处理厂的进一步控制研究。     

寒冷地区污水处理低温生化改良型脱氮除磷工艺的应用

在污水处理厂出水标准逐步提高的前提下,改良型A2/O工艺是优先选择的脱氮除磷技术之一,但在东北寒冷地区的低温生化条件下,污水处理的参数和运行经验仍有待总结和归纳。结合某改良型A2/O工艺污水处理工程的设计和运行实践,对实际工程应用和技术参数进行了总结。     

分点进水多级A/O污水处理工艺设计计算探讨

介绍了分点进水多级A/O污水处理工艺主要设计参数的理论推导和选取方法,通过实际工程设计,分别对多级A/O工艺的反应器级数、反应器流量比例系数(Ri=Qi/Q)、反应器缺氧区和好氧区容积等进行了详细计算,并与单级A/O工艺进行了比较.分点进水多级A/O工艺具有系统污泥浓度高、硝酸盐浓度低、BOD5浓度均衡、节省反应池容积、无需内回流装置等优点.     

北京周边地区小城镇污水处理厂规模及工艺研究

分析了北京周边地区小城镇污水量和污水水质的特点,为小城镇污水处理工程的设计提供参考。并根据小城镇的类型对污水处理厂规模及处理工艺的确定做了初步探讨,得出北京周边地区城市卫星镇的备选工艺优化排序是A2/O、氧化沟、SBR、曝气生物滤池;旅游型小城镇和工业型小城镇的备选工艺优化排序是氧化沟、A2/O、SBR、曝气生物滤池。     

污水处理厂优化设计与运行经验介绍

近年来随着污水处理厂建设速度的加快和污水处理工艺的不断发展,污水处理厂的优化设计与运行已成为污水处理领域关注的问题.以A/O、A2/O、SBR及其衍生工艺为例,介绍了污水处理厂在优化设计与运行中的若干经验,并在此基础上进行了工艺流程选择、预处理和一级处理设施选择的分析探讨.     

Unitank工艺的改良设计

介绍Unitank工艺改良设计在污水处理中的应用，工艺设计中池内没有专门的厌氧池，完善了除磷效果，并可根据BoD5负荷的大小，进行A/O法运行，池水耐冲击负荷较强。     

我国城镇污水处理厂脱氮除磷工艺的应用现状

介绍了我国水环境的氮磷污染现状和来源、国家控制水体氮磷污染的水环境标准、提高污水处理厂脱氮除磷能力的紧迫性以及相应污水处理工艺的应用和发展.脱氮除磷工艺如A/O工艺、A2/O 工艺、氧化沟工艺,SBR及其变型工艺(ICEAS、DAT-IAT、CASS)和UNITANK.工艺在我国都有应用.我国自主开发的倒置A2/O工艺,A-A2/O和改进AB工艺也有很好的发展前景.     

Intelligent control system based on blackboard concept for wastewater treatment processes

An intelligent control system for wastewater treatment processes has been developed and applied to full-scale, high-rate, activated sludge process control. In this control system, multiple software agents that model the target system using their own modeling method collaborate by using data stored in an abstracted database named ‘blackboard’. The software agents, which are called ‘expert modules’, include a fuzzy expert system, a fuzzy controller, a theoretical activated sludge model, and evaluators of raw data acquired by various online sensors including a respirometer. In this paper, the difficulties of controlling an activated sludge system by using a single conventional strategy are briefly reviewed, then our approach to overcome these difficulties by using multiple modeling methods in the framework of an ‘intelligent control system’ is proposed. Case studies of applications to a high-rate activated sludge process that treats BOD and nitrogen of human excrement are also presented.     

Integration of performance,molecular biology and modeling to describe the activated sludge process

To study process performance and population dynamics in activated sludge, a pilot-scale Membrane Bioreactor (MBR) was installed in a municipal wastewater treatment plant (Aubergenville, France). Since no solids losses occur in the MBR effluent, the sludge residence time (SRT) can be: i) easily controlled by means of the sludge withdrawal, and ii) dissociated from the hydraulic residence time (HRT). A complete characterization of this activated sludge system was performed at three sludge ages (5, 10 and 20 days). Raw and treated wastewater quality, as well as sludge concentration, was analyzed, nucleic probe analysts was performed to determine the heterotrophic and nitrifier populations, and the results were compared to the output from a multispecies model that integrates substrate removal kinetics and soluble microbial products (SMP) production/consumption. This paper presents an integrated analysis of the activated sludge process based on chemical, molecular biology, and mathematical tools. The model was able to describe the MBR system with a high degree of accuracy, in terms of COD removal and nitrification, as well as sludge production and population dynamics through the ratio of active nitrifters/bacteria. Both steady-state and transient conditions could be described accurately by the model, except for technical problems or sudden variations in the wastewater composition.     

A nitrate biosensor based methodology for monitoring anoxic activated sludge activity.

An improved methodology based on a nitrate biosensor is developed and applied successfully for in-depth monitoring and study of anoxic activated sludge activities. The major advantages of the methodology are its simplicity, reliability and high data quality. The resulting data allowed for the first time to monitor anoxic respiration rate of activated sludge (nitrate uptake rate (NUR)) at a high time resolution making it clearly comparable with high frequency oxygen uptake rate (OUR) measurements obtained under aerobic conditions. Further, the anoxic respiration data resulting from a pulse addition of carbon source to endogenously respiring anoxic activated sludge shows a clear start-up phenomenon and storage tail that is usually also observed in high-frequency OUR measurements. Finally, the improved methodology can be expected to serve as an anoxic respirometer for activated sludge treatment plants where denitrification process occurs in single-step. Further, it can be used for a variety of purposes e.g. for toxicity and activity monitoring, process control and parameter estimation of the activated sludge process, similar to the aerobic respirometers.     

Model-based evaluation of nitrogen removal in a tannery wastewater treatment plant.

Computer modelling has been used in the last 15 years as a powerful tool for understanding the behaviour of activated sludge wastewater treatment systems. However, computer models are mainly applied for domestic wastewater treatment plants (WWTPs). Application of these types of models to industrial wastewater treatment plants requires a different model structure and an accurate estimation of the kinetics and stoichiometry of the model parameters, which may be different from the ones used for domestic wastewater. Most of these parameters are strongly dependent on the wastewater composition. In this study a modified version of the activated sludge model No. 1 (ASM 1) was used to describe a tannery WWTP. Several biological tests and complementary physical-chemical analyses were performed to characterise the wastewater and sludge composition in the context of activated sludge modelling. The proposed model was calibrated under steady-state conditions and validated under dynamic flow conditions. The model was successfully used to obtain insight into the existing plant performance, possible extension and options for process optimisation. The model illustrated the potential capacity of the plant to achieve full denitrification and to handle a higher hydraulic load. Moreover, the use of a mathematical model as an effective tool in decision making was demonstrated.     

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.     

Comparison of hydrolytic enzyme systems in pure culture and activated sludge under different electron acceptor conditions

Enzymatic hydrolysis under different electron acceptor conditions in nutrient removal activated sludge treatment processes is a weak link in the Activated Sludge Model no. 2 (Henze et al., 1995). An experimental study was undertaken to gain insight into the hydrolysis process with specific focus on hydrolysis kinetics and rates under different electron acceptor conditions. Two pure cultures, Bacillus amyloliquefaciens (Gram positive) and Pseudomonas saccharophila (Gram negative) were chosen for the study. In addition, activated sludge grown in an anaerobic-aerobic system was tested for enzymatic activity using starch as the model substrate. The hydrolytic enzymes were found to be released into the bulk in pure cultures whereas the enzyme activity was found to be mainly associated with the cell surfaces in activated sludge. Further, it was observed that the development of the hydrolytic enzyme system in Bacillus amyloliquefaciens and P. saccharophila is strongly suppressed under anoxic and anaerobic conditions. However, the effect of anaerobic and aerobic incubation on hydrolytic enzyme activity in activated sludge was found to be small. Starch hydrolysis kinetic data from batch experiments with activated sludge followed substrate saturation kinetics that were linear with biomass concentration. Finally, the similar hydrolytic enzyme activities observed under anaerobic and aerobic phases of a sequencing batch reactor are explained by considering the aspects of enzyme location and enzyme system development under aerobic and anaerobic phases. It is proposed that the floc bound enzymes are recycled in a single sludge system so that an equilibrium exists between enzyme loss and synthesis at steady state.     

Reduction of coagulant amount added to activated sludge for phosphorus removal.

Adding coagulant to the activated sludge process is effective in maintaining the stability of phosphorus removal. However, the precise mechanisms of the reaction and behavior of coagulants and phosphorus are not well known. By introducing a new phosphorus removal model (PRM), the behavior of coagulant and phosphorus in the process could be described. The experimental data of the effluent phosphorus concentration and Fe content in the activated sludge agreed with the values calculated by PRM. The amount of coagulant addition to the activated sludge process for phosphorus removal is reduced with the enhanced biological phosphorus removal process. It is suggested that the amount of reduction is determined by using PRM.     

Enhanced nutrient removal MBR system with chemical addition for low effluent TP

A pilot study was conducted to test an membrane bioreactor (MBR) process for combined biological and chemical P removal to achieve a very low effluent total phosphorus (TP) concentration of 0.025 mg P/L. With the data from the pilot test, a simulation study was performed to demonstrate that: (1) the pilot system behaviour (effluent quality, MLSS, etc.) can be modelled accurately with an activated sludge model combined with a chemical precipitation model; and (2) with the calibrated model, simulation scenarios can be performed to further understand the pilot MBR process, and provide information for optimizing design and operation when applied at full-scale. Results from the pilot test indicated that the system could achieve very low effluent TP concentration through biological P removal with a limited chemical addition, and chemical addition to remove P to very low level did not affect other biological processes, i.e., organic and nitrogen removal. Simulation studies indicate that the process behaviour can be modelled accurately with an activated sludge model combined with a chemical precipitation model, and the calibrated model can be used to provide information to optimize system design and operation, e.g., chemical addition control under dynamic loading conditions is important for maintaining biological P removal.     

The use of immersed membranes for upgrading wastewater treatment plants

Membranes can be installed in the clarifier (or aeration tank) of an existing activated sludge plant to enhance the biomass separation function of the system, thereby effectively overcoming any operating constraints associated with sludge settleability. The resulting upgraded plant can be operated at high biomass concentrations (10–20 gMLSS/L), leading to an increase in its treatment capacity. The membranes also ensure a treated water consistently free of suspended solids and a superior disinfection performance. The system offers an enhanced operating flexibility, and allows to operate at high sludge ages leading to a low excess sludge production.Such an immersed membrane activated sludge process (BIOSEP^®) has been developed and applied to the treatment of raw sewage. When treating screened raw sewage with this process, with a sludge concentration of 15 gMLSS/L and a volumetric loading of 1.2 kgCOD/m³/d, a 96% COD reduction and a 95% Total Kjeldahl Nitrogen (TKN) reduction have been obtained. The disinfection performance of the system was over 6 Log removal for fecal coliforms. The resulting production of sludge was 0.20 kgMLSS/kgCOD.Two desk case studies are given for 900 m³/day upgraded plants. In one case, the primary objective was to increase the treatment efficiency and develop nutrient removal for the original plant, while in the other case the primary objective was to increase the capacity of the original 460 m³/day plant.