大型污水处理厂工艺改造与应用对比分析

污水处理厂出水氮、磷标准的提高,促使污水处理厂必须进行脱氮除磷改造。结合重庆某大型污水处理厂二期工程工艺调整与三期工程工艺改造,对详细的调整、改造内容,改造前后的出水水质进行了对比分析。     

UNITANK系统生物——化学联合除磷工艺中试研究

以诸暨市水样进行的中试研究表明,采用生物—化学联合除磷工艺对UNITANK系统进行常规改进得不偿失。但可以考虑采用生物—化学联合除磷工艺作为UNITANK系统应对TP冲击负荷的应急处理工艺。     

传统活性污泥法污水处理厂脱氮除磷改造技术研究

随着受纳水体富营养化日益严重,污水处理厂尾水N、P排放成为迫切需要解决的问题.针对传统活性污泥工艺的实际情况,在脱氮除磷改造中,最大限度地利用原有处理构筑物,提出增加厌氧池或缺氧池以确保生物除磷或脱氮效果.改造采用基于两段A/O的生物处理工艺,工艺论证采用IWA使用的ASMs系列模型进行模拟,模型参数使用污水处理厂多年运行数据进行率定,模拟结论可信.此方法可广泛运用于污水处理厂的改造和设计中,特别是对污水处理运行诊断和实际运行节能减排过程优化具有优势.通过合理调整运行工艺参数,改造后污水处理厂尾水可达到<城镇污水处理厂污染物排放标准(GB 18918-2002)二级标准.     

化学除磷在城市污水处理中的应用

阐述了城市污水处理中除磷的重要性和迫切性,而在普遍采用的生物除磷技术不能满足出水磷的排放标准时可考虑采用化学除磷技术.系统分析了化学除磷的原理、方法、工艺、研究进展及应用前景,并指出了现阶段化学除磷技术研究与发展的目标.     

污水中生物除磷技术的应用进展

阐述了化学除磷的原理和传统的生物除磷原理,重点介绍了倒置A2/O工艺、DEPHANOX工艺、BCFS工艺、A2NSBR工艺等几种经济、高效的生物除磷新技术的原理和特点,并展望了除磷技术的发展方向。     

太湖流域城镇污水处理厂与排水管网优化技术研究与示范

针对太湖流域城镇污水处理厂所面临的水质提标改造、排水管网运行管理急需优化等重大问题,结合河网地区城镇污水处理厂与排水管网的运行过程与特征,对污水处理厂脱氮除磷工艺的优化运行与排水管网的运行管理进行研究,并进行技术的集成与示范.主要成果包括:提出了适合太湖流域污水处理厂提标改造的优化运行方案;建立生物处理系统的协同化学除磷控制技术示范;建立管网系统GIS数据库和优化调度决策支持系统的示范;以及相关的中试研究与设备开发.     

污水处理厂工艺模型的开发及工程应用

以Biowin软件为模拟平台,利用补充的实测数据(如μmax,20和溶解氧)对初步校正的模型进行了二次校正,并利用历史数据对二次校正后的模型进行了验证,结果显示模拟效果更加可靠。然后,使用经校正和验证的模型以高明污水处理厂满足《城镇污水处理厂污染物排放标准》(GB 18918—2002)出水一级B升级到一级A为目标进行了升级改造的策略分析,通过对内回流比、外回流量、泥龄、溶解氧等单因素分析出水达标的可行性。利用这些因素的敏感性确定了一个最优的组合方案,并针对高效生物除磷前提下的化学除磷效果进行了探讨。     

城市污水处理厂运行除磷效果影响因素分析

针对西安市第四污水处理厂倒置A2/O工艺实际运行除磷效果差、出水TP不能达标排放的问题,通过监测污水处理厂实际进出水水质和生化反应池运行参数,分析除磷效果差的主要原因,并研究其解决措施,寻求最优的运行参数和工程改造措施,提出优化厌氧区水力停留时间、强化污泥处理系统污泥水的处理,以及启动污水处理厂已建成的化学除磷系统等措施。     

污水处理A2/O 工艺优化与应用研究

通过分析广州市D污水处理厂A~2/O工艺实际应用情况,提出优化措施和改造方向,并应用于新的污水处理工程中,取得良好的效果。研究表明,A~2/O工艺可通过厌氧和缺氧段倒置、外加化学药剂(氯化铝)和调整工艺运行参数等多种措施进行优化改造,其中倒置A~2/O工艺可以显著提高系统的脱氮除磷能力,具有效率高、投资省、见效快等优点,具有很强的推广应用价值。     

基于BioWin软件的ICEAS工艺模拟与升级改造探讨

利用BioWin软件建立了北京某污水处理厂ICEAS工艺的模型,利用污水处理厂实际运行监测数据和原污水中各有机组分的检测结果对模型进行了动态模拟和校正,确定了模型参数,动态模拟运行结果与实际出水检测结果十分接近,所建立的模型能够较好地反应ICEAS工艺的运行状况。针对目前该工艺出水中氮、磷不达标问题,从调整运行参数、改变工艺流程两个方面对现有工艺提出了升级改造方案。利用BioWin软件对改造方案进行了模拟优化,经过模拟预测对比最终确定了最优改造方案。     

Development of MBR with reduced operational and maintenance costs.

To reduce MBR O&M costs, a new MBR process that conducts efficient simultaneous biological nitrogen and phosphorus removal (BNR) was developed. In the development of this process, various approaches were taken, including reduction of power demand, chemical consumption and sludge disposal costs. To address power demand reductions, air supply requirements for membrane cleaning were reduced. The process adopted an improved membrane that requires less air for cleaning than conventional membranes. It also introduced cyclic aeration, which alternately supplies washing air to the two series of membrane units. Adoption of biological phosphorus removal eliminated chemical costs for phosphorus removal and contributed to the reduction of sludge disposal costs. By combining these technologies, compared to conventional MBR processes, an approximately 27% reduction in O&M costs was achieved.     

Modelling and control strategy testing of biological and chemical phosphorus removal at Aved?re WWTP.

The biological phosphorus removal process is often implemented at plants by the construction of an anaerobic bio-p tank in front of the traditional N removing plant configuration. However, biological phosphorus removal is also observed in plant configurations constructed only for nitrogen removal and simultaneous or post-precipitation. The operational experience with this "accidental" biological phosphorus removal is often mixed with quite a lot of frustration, as the process seems to come and go and hence behaves quite uncontrollably. The aim of this work is to develop ways of intentionally exploiting the biological phosphorus process by the use of instrumentation, control and automation to reduce the consumption of precipitants. Means to this end are first to calibrate a modified ASM2d model to a full-scale wastewater treatment plant (WWTP), including both biological and chemical phosphorus removal and a model of the sedimentation process. Second, based on the calibrated model a benchmark model is developed and various control strategies for biological phosphorus removal are tested. Experiences and knowledge gained from the strategies presented and discussed in this paper are vital inputs for the full-scale implementation of a control strategy for biological phosphorus removal at Aved?re WWTP, which is described in another paper. The two papers hence show a way to bridge the gap from model to full implementation.     

Influence of pH on short-cut denitrifying phosphorus removal

Through a series of experiments using denitrifying phosphorus-accumulating sludge in sequencing batch reactors(SBRs), the variations of the intracellular polymers during the anaerobic phosphorus release process at different pH values were compared, the probable reasons for different performances of phosphorus removal were examined, and system operations in a typical cycle were investigated. The results show that the phosphorus removal rate was positively correlated with pH values in a range of 6.5-8.5. When the pH value was 8.0, the anaerobic phosphorus release rate and anoxic phosphorus uptake rate of the activated sludge were 20.95 mg/(g?h) and 23.29 mg/(g?h), respectively; the mass fraction of poly-b-hydroxybutyrate(PHB) increased to 62.87 mg/g under anaerobic conditions; the mass fraction of polyphosphate was 92.67 mg/g under anoxic conditions; and the effluent concentration of total phosphorus(TP) was 1.47 mg/L. With the increase of pH, the mass fraction of acetic acid and PHB also increased, and the absorption rate of acetic acid was equal to the disintegration rate of polyphosphate. When the pH value was above 8.0, biological phosphorus removal was achieved by chemical phosphorus precipitation, and the phosphorus removal rate decreased.     

Experience from 10 years of full-scale operation with enhanced biological phosphorus removal at Oresundsverket.

Ten years of full-scale experience with enhanced biological phosphorus removal (EBPR) has been evaluated. During the start-up period lack of carbon source was the main operational problem and a higher level of volatile fatty acids was secured by introducing a primary sludge hydrolysis. Acidic thermal sludge hydrolysis was used as the sludge treatment method at the plant during about three years. One effluent stream, rich in carbon and precipitant, was brought back to the process leading to an improvement of the phosphorus removal both by an improved biological process and chemical precipitation. A quite stable process of EBPR was developed with low levels of effluent phosphorus concentration. Stringent effluent discharge limits during short evaluation periods necessitated a continued work for improvement of the short-term stability. During periods with lack of carbon, such as industrial holiday or rainy periods, both simultaneous precipitation and reduced aeration have been successfully tested as strategies for securing low levels of effluent phosphorus.     

Advanced phosphorus removal for secondary effluent using a natural treatment system

Mechanisms for low concentrations phosphorus removal in secondary effluent were studied, and a process was developed using limestone filters (LF), submerged macrophyte oxidation ponds (SMOPs) and a subsurface vertical flow wetland (SVFW). Pilot scale experimental models were applied in series to investigate the advanced purification of total phosphorus (TP) in secondary effluent at the Chengjiang sewage treatment plant. With a total hydraulic residence time (HRT) of 82.52 h, the average effluent TP dropped to 0.17 mg L(-1), meeting the standard for Class III surface waters. The major functions of the LF were adsorption and forced precipitation, with a particulate phosphorus (PP) removal of 82.93% and a total dissolved phosphorus (TDP) removal of 41.07%. Oxygen-releasing submerged macrophytes in the SMOPs resulted in maximum dissolved oxygen (DO) and pH values of 11.55 mg L(-1) and 8.10, respectively. This regime provided suitable conditions for chemical precipitation of TDP, which was reduced by a further 39.29%. In the SVFW, TDP was further reduced, and the TP removal in the final effluent reached 85.08%.     

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.     

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.     

Experiences with a large-size WWTP based on activated sludge-biofiltration processes: 25 months of operation.

The South-Budapest Wastewater Treatment Plant (SBWWTP) had been operated as a high-load activated sludge (AS) plant since the middle of the 60s. According to the requirements proposed by the water authorities the treatment process had to be upgraded into nutrient (phosphorus and nitrogen) removal. The upgrade of the plant comprised implementation of BIOFOR type nitrifying (NP) and post-denitrifying (DN) biofilters downstream of the AS stage. Phosphorus removal was obtained by chemical precipitation that can be done at five different points for feeding ferric-sulfate (Fe2(SO4)3). Partial flow recirculation was administered from the nitrifying BIOFOR unit ahead of the AS basin for pre-denitrification utilizing raw wastewater as carbon source. The plant performance was monitored since the test operation period for 25 months. Experience revealed that significant nitrification occurs in the high-load activated sludge basin originally designed for carbon removal. During the summer period (characterized by temperature of 20-25 degrees C) about 37-42% ammonium conversion rate was observed in the reactor. The decreasing temperature in the wintertime resulted in lower nitrification rates, of about 6-10%. The combined activated sludge-biofiltration process proved its viability in the removal of organic matter, nitrogen and phosphorus. In this special configuration the AS system plays a key role in the nitrogen and organic matter removal.     

低碳城市污水反硝化除磷若干影响因素的试验研究

广州地区城市污水碳量严重偏低、碳氮磷比例失调,其同步脱氮除磷一直是个难题,为此以SBR法进行反硝化除磷影响因素的试验研究.试验表明:缺氧段硝酸盐负荷决定反硝化吸磷效果,在硝酸盐足量情况下,缺氧除磷率达到99.4%.通过对ORP与pH的在线监测发现,ORP无法作为缺氧吸磷过程的控制参数,pH可以指示缺氧吸磷情况.以亚硝酸盐氮作为电子受体研究发现,15 mg/L以下的亚硝酸盐氮可以作为电子受体进行吸磷作用,当亚硝酸盐氮浓度达到23.8 mg/L时,反硝化吸磷受到了明显的抑制;厌氧初始pH在6～8变化时,厌氧释磷量随着pH的升高而增加,pH变化只影响厌氧释磷量,不影响释磷速率.缺氧初始pH降到6时,反硝化吸磷效果变差,缺氧段pH偏碱性条件下,反硝化除磷仍能够稳定进行.