Temperature effects on biological nutrient removal system with weak municipal wastewater

The wastewater characteristics of low organic strength coupled with low temperature would be considerable variables for design and operation of biological nutrient removal (BNR) systems. But temperature studies have mostly been focused on individual process with biological phosphorus removal, nitrification and denitrification, respectively. Overall temperature effects on BNR system may not be fully represented by sum of results of separated studies on biological nutrient removal steps. The operating result of a retrofitted full scale unit along with laboratory-scale BNR unit indicated 90% of nitrification was possible at temperature as low as 8°C. However, the denitrification was turned out to be a key step to regulate the overall nutrient removal efficiencies. When the operating temperature dropped down, a rapid decrease of phosphorus removal efficiencies was observed by the nitrate in return sludge. If nitrification was not well developed, phosphorus removal returned to the normal efficiency even at low temperature of 5°C. The phosphorus removal mechanism was not influenced at this low temperature.     

Survey of filamentous populations in nutrient removal plants in four European countries

A joint EU research project aimed at solving activated sludge bulking in nutrient removal plants was initiated in 1993. The project started with a survey of the size and composition of the filamentous population in nutrient removal plants in Denmark, Germany, Greece and the Netherlands.The results show that biological nutrient removal process conditions indeed favour filamentous microorganisms in their competition with floc forming organisms. An increase in the size of the filamentous population resulted in a deterioration of the settling properties of the biomass, except for plants with Bio-P removal conditions. It is assumed that in the latter case the dense clusters of Bio-P bacteria increase the weight of the flocs, and compensate for the effect of the larger number of filaments.Although exceptions frequently occur, the following sequence in decreasing filamentous organism population size was observed for the process conditions indicated:

• -completely mixed + simultaneous denitrification;
• -completely mixed + intermittent aeration/denitrification;
• -alternating anoxic/oxic process conditions, with an anaerobic tank for biological phosphate removal (Bio-Denipho);
• -alternating anoxic/oxic process conditions (Bio-Denitro);
• -predenitrification

The surveys provided little information about the effect of nutrient removal in plants with plug flow aeration basins. Simultaneous precipitation with aluminium salts nearly always resulted in a low number of filaments and a good settling sludge.The size of the filamentous organism population showed a seasonal pattern with a maximum in winter/early spring and a minimum during summer (in Greece: during autumn). This seasonal variation is primarily caused by the effect of the season on the population sizes of M. parvicella, N. limicola and Type 0092.M. parvicella is by far the most important filamentous species in nutrient removal plants. In Denmark only, Type 0041 also frequently dominates the filamentous population, but seldom causes severe bulking. Considering their frequency of occurrence, approx. 10 other filamentous micro-organisms are of minor importance. Growth of some of these species, viz. those which use soluble substrate, can be prevented by the introduction of Bio-P process conditions.M. parvicella and Type 0041 (and probably also Actinomycetes and the Types 1851 and 0092) seem to compete for the same substrates i.e. the influent particulate fraction. Most of the differences in composition of the filamentous microorganism population can be explained by whether or not premixing of influent and recycled sludge is used. In general, premixing for a short period of time followed by anoxic conditions favours Type 0041. M. parvicella seems to proliferate if the particulate fraction is first hydrolysed or if it enters the plant via an oxic zone. It is concluded that bulking in nutrient removal plants is mainly caused by filamentous species requiring the particulate fraction for their growth.     

市政污水生物除磷效能和功能微生物分布特征

调研了4座市政污水处理厂的除磷效能、污泥活性以及微生物分布特征。结果表明出水总磷均达到《城镇污水处理厂污染物排放标准》(GB18918—2002)一级标准,但污泥性能差异显著。活性污泥厌氧释磷率和好氧聚磷率范围分别是0.224～7.77mg/(gVSS.h)和0.386～7.9mg/(gVSS.h)。聚磷假丝酵母菌(Accumulibacter)比例较低,为3.8%～8.7%,聚糖假丝酵母菌(Competibacter)为3.2%～9.1%。进水乙酸含量和乙酸吸收率,厌氧释磷率和好氧聚磷率间都存在很好的线性相关性,表明污水中可利用碳源的数量和磷素的比例极大影响污泥除磷性能。故控制工业废水排入,适当添加碳源,或设置独立的前置反硝化池有望增加污水处理厂的除磷效能。     

Calibration and simulation of two large wastewater treatment plants operated for nutrient removal.

Control and optimisation of plant processes has become a priority for WWTP managers. The calibration and verification of a mathematical model provides an important tool for the investigation of advanced control strategies that may assist in the design or optimization of WWTPs. This paper describes the calibration of the ASM2d model for two full scale biological nitrogen and phosphorus removal plants in order to characterize the biological process and to upgrade the plants' performance. Results from simulation showed a good correspondence with experimental data demonstrating that the model and the calibrated parameters were able to predict the behaviour of both WWTPs. Once the calibration and simulation process was finished, a study for each WWTP was done with the aim of improving its performance. Modifications focused on reactor configuration and operation strategies were proposed.     

Upgrading of wastewater treatment plants for nutrient removal under optimal use of existing structures.

Upgrading of wastewater treatment plants under maximum use of existing structures is often an important requirement, but also useful due to a number of aspects. Because of a change in legal effluent requirements, a number of plants in Austria, typically aged 20+ years, were required to be extended. The two stage activated sludge HYBRID-process often provides an interesting design alternative for such plant upgrades, especially in case an anaerobic sludge treatment stage already exists. It provides high nutrient removal capacity at low area demand. The latter is especially important in cases where no or very limited extension area is available making it the key factor to preserve a site for future use. Based on two full stage case studies the adaptation of the plant layout, first operation results and a synthetic cost comparison to a conventional (single stage) plant extension are given.     

我国城市污水处理厂能耗规律的统计分析与定量识别

采用描述统计、聚类分析、非参数检验、相关分析、非线性回归分析等方法,对我国559座城镇污水处理厂2006年的能耗状况及其影响因素进行了统计分析和定量规律识别.目前我国城镇污水处理厂平均电耗为0.290 kW·h/m3,82%以上的污水处理厂电耗不超过0.440 kW·h/m3,相当于发达国家20世纪初或更早期的水平,仍存在一定节能潜力.对能耗有显著影响的因素包括:污水处理厂所处地区的自然环境条件和社会经济总体能耗水平、污水处理工艺类型、污水处理量、污染物去除量、所接纳的工业废水比例等.研究结果得出我国9种主要污水处理工艺的能耗排序,污水处理量、6类污染物去除量与电耗之间的定量关系,以及进水中工业废水比例对能耗的影响程度.     

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.     

BNR—MBR组合工艺处理生活污水研究进展

目前城市污水处理工艺多采用生物营养盐去除工艺(BNR),引入膜生物反应器(MBR)组成BNR—MBR组合工艺,可以提高出水水质,实现水资源的回用。与传统的BNR工艺相比,组合工艺的某些运行条件和工艺参数发生了改变。概述了BNR—MBR工艺应用在生活污水处理中的工艺特征,分析和探讨了组合工艺对氮、磷的去除特性以及膜污染控制。     

Nitrogen removal by recycle water nitritation as an attractive alternative for retrofit technologies in municipal wastewater treatment plants.

The recycle water from sludge processing in municipal wastewater treatment plants causes many serious problems in the efficiency and stability of the mainstream process. Thus, the design approach for recycle water is an important part of any biological nutrient removal system design when a retrofit technology is required for upgrading an existing plant. Moreover, the application of nitrogen removal from recycle water using the nitritation process has recently increased due to economic reasons associated with an effective carbon allocation as well as the minimization of aeration costs. However, for the actual application of recycle water nitritation, it has not been fully examined whether or not additional volume would be required in an existing plant. In this paper, the addition of recycle water nitritation to an existing plant was evaluated based on a volume analysis and estimation of final effluent quality. It was expected that using the reserve volume of the aeration tank in existing plants, recycle water nitritation could be applied to a plant without any enlargement. With the addition of recycle water nitritation, it was estimated that the final effluent quality would be improved and stabilized, especially in the winter season.     

Automatic control and remote monitoring system for biological nutrient removal on small wastewater treatment plants in Korea.

Many small-size wastewater treatment plants in Korea's rural communities are designed to remove organic and suspended matter only, and they generally show a large fluctuation in the influent loading compared to municipal wastewater treatment plants (MWWTPs). They also have no professional engineers stationed for efficient operation against mechanical breakdown. For those reasons, the wastewater treatment plants have low efficiency in treatment of nitrogen and phosphorus as well as organic matter. In order to solve those problems, this study developed an automatic control system and RMS (remote monitoring system), which can keep efficiency stable despite any change in the small plants' loading rates and are capable of removing nutrient materials such as nitrogen or phosphorus. According to the results of the Experimental SBR system of the automatic control program, complete nitrification was made under oxic conditions and denitrification occurred as NO3-N concentration decreased by 0.5 mg/l in anoxic conditions and excellent nitrogen removal efficiency was seen generally. The Experimental SBR system created "phosphate release and uptake" effectively and displayed phosphate-removing efficiency up to more than 80% as the concentration of effluent was kept low by 0.4 mg/l. RMS developed in this study transmits a plant's data and operation states to clients in remote locations in real-time interval through the Internet. Therefore, although you are in a remote location, it allows you to see if a plant is properly operated or there is any breakdown.     

Nutrients removal in MBRs for municipal wastewater treatment.

Owing to increasingly stringent effluent quality requirements, intensifications of the conventional activated sludge process (ASP) are required. Due to high biomass concentrations employed, higher metabolic rates and better nutrient removal are possible in membrane bioreactors (MBRs). Decoupling of hydraulic and solids residence times offers additional possibilities for process design and optimisation. Recently, unconventional concepts like post-denitrification and enhanced biological phosphorus removal in MBRs have emerged. The objective of this paper is to present current knowledge on nutrients removal in MBRs and trends in process optimisation in comparison with conventional ASP.     

Optimising design, operation and energy consumption of biological aerated filters (BAF) for nitrogen removal of municipal wastewater.

The Biofiltration process in wastewater treatment combines filtration and biological processes in one reactor. In Europe it is meanwhile an accepted technology in advanced wastewater treatment, whenever space is scarce and a virtually suspended solids-free effluent is demanded. Although more than 500 plants are in operation world-wide there is still a lack of published operational experiences to help planners and operators to identify potentials for optimisation, e.g. energy consumption or the vulnerability against peakloads. Examples from pilot trials are given how the nitrification and denitrification can be optimised. Nitrification can be quickly increased by adjusting DO content of the water. Furthermore carrier materials like zeolites can store surplus ammonia during peak loads and release afterwards. Pre-denitrification in biofilters is normally limited by the amount of easily degradable organic substrate, resulting in relatively high requirements for external carbon. The combination of pre-DN, N and post-DN filters is much more advisable for most municipal wastewaters, because the recycle rate can be reduced and external carbon can be saved. Exemplarily it is shown for a full scale preanoxic-DN/N/postanoxic-DN plant of 130,000 p.e. how 15% energy could be saved by optimising internal recycling and some control strategies.     

德国城镇污水处理厂运行概况

介绍了目前德国污水处理厂的总体概况、出水标准、出水水质等级的划分,并对2004年和2008年德国污水处理厂的进、出水水质情况进行了对比。同时也比较分析了上海市城镇污水处理厂的进、出水水质情况。     

Where is biological nutrient removal going now?

With more than 30 years of experience multiple options exist for removal of nitrogen and phosphorus from wastewater. Communities that were exempt from nutrient removal for many years must now comply with imposed nutrient limits, and in areas where technology-based nutrient limits have been in place communities are now faced with more stringent mass-based limits that are becoming more difficult to meet as their populations increase. Recent efforts in the industry have been focused on getting more out of existing plants, or in many cases where land is not available, in intensifying existing processes to increase capacity and/or level of treatment. This paper will discuss some of these methods and the general direction in which biological nutrient removal is developing to address these new challenges.     

Re-use of winery wastewaters for biological nutrient removal.

The aim of this study was to evaluate the feasibility of the re-use of the winery wastewater to enhance the biological nutrient removal (BNR) process. In batch experiments it was observed that the addition of winery wastewater mainly enhanced the nitrogen removal process because of the high denitrification potential (DNP), of about 130 mg N/g COD, of the contained substrates. This value is very similar to that obtained by using pure organic substrates such as acetate. The addition of winery wastewater did not significantly affect either phosphorus or COD removal processes. Based on the experimental results obtained, the optimum dosage to remove each mg of N-NO3 was determined, being a value of 6.7 mg COD/mg N-NO3. Because of the good properties of the winery wastewater to enhance the nitrogen removal, the viability of its continuous addition in an activated sludge pilot-scale plant for BNR was studied. Dosing the winery wastewater to the pilot plant a significant increase in the nitrogen removal was detected, from 58 to 75%. The COD removal was slightly increased, from 89 to 95%, and the phosphorus removal remained constant.     

Biological nutrient removal in membrane bioreactors: denitrification and phosphorus removal kinetics.

The impact of including membranes for solid liquid separation on the kinetics of nitrogen and phosphorus removal was investigated. To achieve this, a membrane bioreactor (MBR) biological nutrient removal (BNR) activated sludge system was operated. From batch tests on mixed liquor drawn from the MBR BNR system, denitrification and phosphorus removal rates were delineated. Additionally the influence of the high total suspended solids concentrations present in the MBR BNR system and of the limitation of substrate concentrations on the kinetics was investigated. Moreover the ability of activated sludge in this kind of system to denitrify under anoxic conditions with simultaneous phosphate uptake was verified and quantified.The denitrification rates obtained for different mixed liquor (ML) concentrations indicate no effect of ML concentration on the specific denitrification rate. The denitrification took place at a single specific rate (K(2)) with respect to the ordinary heterotrophic organisms (OHOs, i.e. non-PAOs) active mass. Similarly, results have been obtained for the P removal process kinetics: no differences in specific rates were observed for different ML or substrate concentrations. From the P removal batch tests results it seems that the biological phosphorus removal population (PAO) consists of 2 different sets of organisms denitrifying PAO and aerobic PAO.     

Removal of micropollutants in municipal wastewater treatment plants by powder-activated carbon

Micropollutants (MP) are only partly removed from municipal wastewater by nutrient removal plants and are seen increasingly as a threat to aquatic ecosystems and to the safety of drinking water resources. The addition of powder activated carbon (PAC) is a promising technology to complement municipal nutrient removal plants in order to achieve a significant reduction of MPs and ecotoxicity in receiving waters. This paper presents the salient outcomes of pilot- and full-scale applications of PAC addition in different flow schemes for micropollutant removal in municipal wastewater treatment plants (WWTPs). The sorption efficiency of PAC is reduced with increasing dissolved organic carbon (DOC). Adequate treatment of secondary effluent with 5-10 g DOC m(-3) requires 10-20 g PAC m(-3) of effluent. Counter-current use of PAC by recycling waste PAC from post-treatment in a contact tank with an additional clarifier to the biology tank improved the overall MP removal by 10 to 50% compared with effluent PAC application alone. A dosage of 15 g PAC m(-3) to a full-scale flocculation sand filtration system and recycling the backwash water to the biology tank showed similar MP elimination. Due to an adequate mixing regime and the addition of adapted flocculants, a good retention of the fine fraction of the PAC in the deep-bed filter were observed (1-3 g TSS m(-3); TSS: total suspended solids). With double use of PAC, only half of the PAC was required to reach MP removal efficiencies similar to the direct single dosage of PAC to the biology tank. Overall, the application of PAC in WWTPs seems to be an adequate and feasible technology for efficient MP elimination (>80%) from wastewater comparable with post ozonation.     

我国城镇污水处理厂建设及运行现状分析

截至2009年底,全国投运的城镇污水处理设施共1 916座,总设计处理能力10 594万m3/d,平均日处理水量8 132万m3/d,设施平均利用率为76.8%。对污水处理厂设计处理规模的统计分析表明:以小型污水处理厂(5万m3/d以下)增长最为迅速;大型污水处理厂和采用氧化沟工艺的污水处理厂的平均利用率均相对较好;污水处理厂的建设以及污水处理能力存在显著的地域分布特点,除了大西北地区,其他七大区域的平均利用率均在70%以上;城镇污水处理能力与GDP具有较好的线性相关性。污水处理厂的建设应因地制宜地选择合适的主体工艺类型和设计规模,有效提高设施利用率。     

Biosensor-based control of nitrification inhibitor in municipal wastewater treatment plants.

The effect of potassium cyanide (KCN) on nitrification processes in municipal wastewater treatment plants was studied by batch nitrification tests, which indicated that nitrification processes tend to be inhibited at a lower KCN concentration than the present discharge standard to sewerage. The experiment of the biosensor using nitrifying bacteria was also conducted for continuous monitoring of nitrification inhibitor in influent wastewater, and demonstrated that the biosensor can detect KCN at as low as EC10 of the abovementioned batch nitrification test. Moreover, to determine the effectiveness of application of the biosensor to avoid the impact of KCN due to an accidental spillage in a sewerage system, KCN was intentionally injected into the experimental models of activated sludge process equipped both with and without the biosensor. The model with the biosensor that could detect KCN could divert the wastewater including KCN to a refuge tank, which resulted in the avoidance of upset of the activated sludge process. On the other hand, the model without the biosensor was upset in the nitrification process due to KCN. Such differences demonstrate the effectiveness of the biosensor applied to countermeasures of an accidental spillage of toxic chemicals to avoid upset of nitrification in municipal wastewater treatment plants.