Nitrogen and phosphorus removal in pilot-scale anaerobic-anoxic oxidation ditch system

To achieve high efficiency of nitrogen and phosphorus removal and to investigate the rule of simultaneous nitrification and denitrification phosphorus removal （SNDPR）, a whole course of SNDPR damage and recovery was studied in a pilot-scale, anaerobicanoxic oxidation ditch （OD）, where the volumes of anaerobic zone, anoxic zone, and ditches zone of the OD system were 7, 21, and 280 L, respectively. The reactor was fed with municipal wastewater with a flow rate of 336 L/d. The concept of simultaneous nitrification and denitrification （SND） rate （rSND） was put forward to quantify SND. The results indicate that： （1） high nitrogen and phosphorus removal efficiencies were achieved during the stable SND phase, total nitrogen （TN） and total phosphate （TP） removal rates were 80% and 85%, respectively; （2） when the system was aerated excessively, the stability of SND was damaged, and rSND dropped from 80% to 20% or less; （3） the natural logarithm of the ratio of NOx to NH4^＋ in the effluent had a linear correlation to oxidation-reduction potential （ORP）; （4） when NO3^- was less than 6 mg/L, high phosphorus removal efficiency could be achieved; （5） denitrifying phosphorus removal （DNPR） could take place in the anaerobic-anoxic OD system. The major innovation was that the SND rate was devised and quantified.

An innovative integrated oxidation ditch with vertical circle(IODVC) for wastewater treatment

The oxidation ditch process is economic and efficient for wastewater treatment, but its application is limited in case where land is costly due to its large land area required. An innovative integrated oxidation ditch with vertical circle(IODVC) system was developed to treat domestic and industrial wastewater aiming to save land area. The new system consists of a single channel divided into two ditches(the top one and the bottom one by a plate), a brush, and an innovative integral clarifier. Different from the horizontal circle of the conventional oxidation ditch, the flow of IODVC system recycles from the top zone to the bottom zone in the vertical circle as the brush is running, and then the IODVC saved land area required by about 50% compared with a conventional oxidation ditch with an intrachannel clarifier. The innovative integral clarifier is effective for separation of liquid and solids, and is preferably positioned at the opposite end of the brush in the ditch. It does not affect the hydrodynamic characteristics of the mixed liquor in the ditch, and the sludge can automatically return to the down ditch without any pump. In this study, experiments of domestic and dye wastewater treatment were carried out in bench scale and in full scale, respectively. Results clearly showed that the IODVC efficiently removed pollutants in the wastewaters, i.e., the average of COD removals for domestic and dye wastewater treatment were 95% and 90%, respectively, and that the IODVC process may provide a cost effective way for full scale dye wastewater treatment.

Numerical simulation of a combined oxidation ditch flow using 3D k-ε turbulence model

The standard three dimensional（3D） k-ε turbulence model was applied to simulate the flow field of a small scale combined oxidation ditch. The moving mesh approach was used to model the rotor of the ditch. Comparison of the computed and the measured data is acceptable. A vertical reverse flow zone in the ditch was found, and it played a very important role in the ditch flow behavior. The flow pattern in the ditch is discussed in detail, and approaches are suggested to improve the hydrodynamic performance in the ditch.

Enhanced biological nutrients removal using an integrated oxidation ditch with vertical circle from wastewater by adding an anaerobic column

Compared to conventional oxidation ditches, an integrated oxidation ditch with vertical circle （IODVC） has the characters of concise configuration, simple operation and maintenance, land saving and automatical sludge returning. By the utilization of vertical circulation, an aerobic zone and an anoxic zone can be unaffectedly formed in the IODVC. Therefore, COD and nitrogen can be efficiently removed. However, the removal efficiency of phosphorus was low in the IODVC. In the experiment described, a laboratory scale system to add an anaerobic column to the IODVC has been tested to investigate the removal of phosphorus from wastewater. The experimental results showed that the removal efficiency of TP with the anaerobic column was increased to 54.0% from 22.3% without the anaerobic column. After the acetic sodium was added into the influent as carbon sources, the mean TP removal efficency of 77. 5 % was obtained. At the same time, the mean removal efficiencies of COD, TN and NH3-N were 92.2%, 81.6% and 98.1%, respectively, at 12 h of HRT and 21-25 d of SRT. The optimal operational conditions in this study were as follows： recycle rate = 1.5-2.0, COD/TN 〉 6, COD/TP 〉 40, COD loading rate = 0.26-0.32 kgCOD/（kgSS· d）, TN loading rate = 0. 028-0. 034 kgTN/（ kgSS·d） and TP loading rate = 0.003-0.005 kgTP/（kgSS· d）, respectively.

Addition of anaerobic tanks to an oxidation ditch system to enhance removal of phosphorus from wastewater

The oxidation ditch has been used for many years all over the world as an economic and efficient wastewater treatment technology. It can remove COD, nitrogen and a part of phosphorus efficiently. In the experiment described, a pilot scale Pasveer oxidation ditch system has been tested to investigate the removal of phosphorus from wastewater. The experimental results showed that influent total phosphorus(TP) was removed for 35%-50%. After this, two anaerobic tanks with total volume of 11 m 3 were added to the system to release phosphorus. As a result, the TP removal efficiency increased by about 20%. At an anaerobic HRT of about 6 hours, a TP removal efficiency of 71% was achieved.

Variation of biological and hydrological parameters and nitrogen removal optimization of modified Carrousel oxidation ditch process

To enhance the nitrogen removal,a systemic monitoring of the biological and hydrological parameters of Carrousel oxidation ditch in Chongqing Jingkou Wastewater Treatment Plant was carried out to study the feasibility of simultaneous nitrification and denitrification(SND).The variation and distribution of parameters such as flow velocity,concentration of dissolved oxygen(DO) and mixed liquor suspended solids(MLSS) in oxidation ditch were monitored and analyzed,which were major control factors for SND.The results showed that,the dimensional distribution of flow velocity,DO and MLSS were affected significantly by the operation condition of the aeration wheels.With all the four aeration wheels being in operation,DO and flow velocity were higher and the mixing of MLSS was sufficient.With three aeration wheels being in operation,the flow velocity in most of the bottom areas was enough to meet the basic requirements of no deposition,and the anaerobic region and aerobic region could exist simultaneously in one oxidation ditch,which was helpful to the process of SND.According to spatial distribution characteristics of the flow velocity,DO and soluble components under optimized condition,different functional zones of biochemical reaction in the Carrousel oxidation ditch system were defined,which might contribute to the optimization control and SND of Carrousel oxidation ditch.

Evaluation on the performance of triple oxidation ditch system treating municipal wastewater

The oxidation ditch system in Handan WWTP is the biggest triple oxidation ditch system (T O.D.) treating municipal wastewater in China with a service population of 350000. The system can perform three functions, aerobic, anoxic and precipitation process in different ditch by alternating the operation mode, and the simultaneous removal of nitrogen and organic substances can be attained. Statistic analysis of data from past five year operation in the WWTP was presented, and investigations on COD, nitrogen, phosphorus removal in system were carried out in the field. The optimum number of aerated brush to meet satisfied nitrification and denitrification was determined on basis of field experiment. The effluent is reused as cooling water for a electricity power plant, and excess sludge is utilized as fertilizer. The concept of an ecological WWTP is put forward by the example of Handan WWTP.

Numerical study on hydraulic performance of submerged propellers in oxidation ditch

The submerged propeller is an efficient diving mix device,which is applicable for oxidation ditch treatment in industry,city and village wastewater-treatment plant. The impeller structure and reasonable rotating speed are important factors that determine flow field distribution and energy conversion efficiency. So it is necessary to use modern design methods to develop new kinds of high efficiency submerged propellers,and research the flow field characteristics of submerged propellers. On the basis of the existing form drawing,three-dimensional model of submerged propellers and unstructured tetrahedral mesh were generated. Based on Navier- Stokes equations and standard k- ε turbulence model,the flow was simulated by using a simple algorithm. Through changing some design parameters of propellers,the corresponding numerical simulation results reveal that for the same impeller diameter and service area of submerged propellers,the power consumption could be reduced effectively by optimizing blade mounting angle,which can determine the best blade mounting angle and most suitable rotational speed under given conditions. The study can provide theoretical and project guidance for submerged propellers design.

Simulation of liquid-gas flow in full-scale Caroussel oxidation ditch with surface aeration

A model for liquid-gas flow(MLGF),considering the free movement of liquid surface,was built to simulate the wastewater velocity field and gas distribution in a full-scale Caroussel oxidation ditch with surface aeration.It was calibrated and validated by field measurement data,and the calibrated parameters and sections were selected based on both model analysis and numerical computation.The simulated velocities of MLGF were compared to that of a model for wastewater-sludge flow(MWSF).The results show that the free liquid surface considered in MLGF improves the simulated velocity results of upper layer and surface.Moreover,distribution of gas volume fraction(GVF) simulated by MLGF was compared to dissolved oxygen(DO) measured in the oxidation ditch.It is shown that DO distribution is affected by many factors besides GVF distribution.

Flow characteristic and wastewater treatment performance of a pilot-scale airlift oxidation ditch

A pilot-scale airlift oxidation ditch using bubble diffuser and baffle as aerator was operated in a wastewater treatment plant(WWTP)to investigate its flow characteristic and wastewater treatment performance.Compared with the conventional oxidation ditch process,effective depth and oxygen utilization efficiency of this new process was improved by underwater aeration.Furthermore,it had a reversed velocity distribution,which decreased from the bottom to the top on vertical section.Velocity measurement showed that a velocity over 0.2 m/s at the bottom was sufficient to prevent sludge settlement during long term operation.Application of these concepts would save land area and energy consumption by about 25%–50%and 55%,respectively.In this new system,organic biodegradation and nitrification could be well achieved.Denitrification could occur steadily in the straight part by adjusting the airflow rate.An average TN removal rate of 63%was achieved with dissolved oxygen(DO)concentrations between 0.6 mg/L and 1.5 mg/L.The main pollutants in the effluent could meet the strictest discharge standard(COD<50 mg/L,NH4_(+)^(–)N<5 mg/L,and TN<15 mg/L)in China now.

剥离黏液层改性污泥回用对污泥颗粒化过程的影响

胞外聚合物(Extracellular polymeric substances,EPS)的资源化回收已经得到了广泛研究,但关于剥离EPS后污泥就地回用至污水生物处理系统的研究甚少。通过对剥离黏液层改性后的污泥进行考察发现,改性后的污泥仍具有良好的微生物活性,具备较好的底物降解能力;且相较于原泥,改性污泥的胞外蛋白质与胞外多糖质量比[m(PN)/m(PS)]由1.37提升至1.84,Zeta电位绝对值降低了25.97%,絮凝性能提升,因此改性污泥可回用于污水生物处理系统,并改善其性能。进一步地,研究了改性污泥连续回用至DE型氧化沟系统对其性能及污泥性质的影响,结果表明,随着回用天数的增加,污泥的m(PN)/m(PS)升高,系统内污泥开始颗粒化,粒径大于200μm的颗粒污泥占比达到了30%以上,污泥颗粒化持续增强。因此,连续回用剥离黏液层改性污泥至DE型氧化沟系统,可以促使系统内污泥颗粒化,从而为连续流氧化沟系统的污泥颗粒化提供了新方法。

基于两相流的氧化沟推流器分布特性研究

针对氧化沟污水处理技术中可能存在的能耗大、污泥淤积的问题,将活性污泥的黏度和沉降速率通过用户自定义函数导入Fluent软件,对某污水处理厂的标准氧化沟进行水-活性污泥两相流数值计算,得到氧化沟中推流器功率、速度分布情况及污泥分布情况,并对其进行分析比较,选出最优电机功率及推流器分布。对氧化沟内流场特性进行深入分析,将数值模拟及试验测得断面流速进行比较,结果表明各测点数据吻合程度较好,因此认为数值模拟能够较好地预测出真实流场中各点的流速,且速度死区率大的区域污泥质量浓度一般较高。

广东某污水处理厂氧化沟工艺提质增效改造工程设计

广东省某污水处理厂一期工程原采用氧化沟为主体的工艺,提标改造后要求出水指标达到《城镇污水处理厂污染物排放标准》(GB 18918-2002)一级A标准及《广东省地方标准水污染物排放限值》(DB44/26-2001)的第二时段一级标准的两者较严值,实际出水部分指标(如COD、SS、TP、TN)已临近排放限值,BOD_(5)、NH_(3)-N常有超标现象。提质增效工程旨在对原有生化池、消毒池等进行改造优化,并在二沉池后端新增“高效沉淀+滤布滤池”深度处理单元。提质增效后的运行数据表明,出水COD≤14 mg/L、BOD_(5)≤3.1 mg/L、ρ(TN)≤9.5 mg/L、ρ(TP)≤0.24 mg/L、ρ(SS)≤5.1 mg/L,去除率均>90%,出水水质稳定达到设计标准,同时氧化沟曝气单位能耗降低25%,单位成本低于同类型项目水平。

城市污水处理中不同活性污泥法设计和运行效果的对比分析

通过对城市污水处理中的不同活性污泥法进行了设计和运行效果的对比分析。同时,比较生物脱氮除磷工艺、序批式活性污泥法、生物吸附氧化法和氧化沟工艺,发现它们在处理效率、运行稳定性、抗冲击能力和经济性方面存在差异。进一步分析了影响活性污泥法运行效果的因素,如进水水质、曝气方式、污泥龄和温度。研究结果对优化活性污泥法的设计和运行具有重要意义,有助于提高城市污水处理的效率和可持续发展。

卡鲁塞尔2000型氧化沟生物除磷的效果分析

针对卡鲁塞尔2000型氧化沟的生物除磷开展的污水厂的阶段性检测实验研究,通过沿程分析总磷去除效果,总结污水厂生物除磷的运行效果,为污水厂提高和控制生物除磷效果提供实验数据支持,同时也为降低化学除磷成本提出了思路。

苏州市横扇生活污水处理厂提标改造工程设计

苏州市吴江横扇污水处理厂提标改造工程规模0.5万m^(3)/d,改造内容包括新建二级提升泵房、反硝化深床滤池、消毒池、污泥浓缩池、除臭生物滤池、鼓风机房及配电间等设施。同时对现状AAO氧化沟进行改造,由转碟曝气改为底部鼓风曝气。工程建设完成后,出水水质优于地表准Ⅳ类标准,有效地改善了周边的水体环境。

Carrousel氧化沟+MBR在城镇生活污水处理中的应用

针对河北省某城镇生活污水处理设施能力不足,出水污染物不达标等问题,在原废水处理设施上进行改造,设计处理能力为15000 m~3/d,采用卡鲁塞尔氧化沟工艺+MBR作为此次污水处理的核心工艺。介绍了工艺流程及主要设计参数,考察了组合工艺对污水处理效果,分析了建设投资及运行费用。运行结果表明:该工艺出水稳定,水质提升效果明显,对主要污染物COD、BOD_(5)、SS、TN、TP的平均去除率分别为92.1%、93.2%、95%、87.7%和71.8%,经卡鲁塞尔氧化沟工艺+MBR工艺处理后,其出水主要污染物指标均达到《城镇污水处理厂污染物排放标准》(GB18918-2002)一级A标准。

乙酸碳源对氧化沟工艺处理低碳氮比工业废水脱氮性能的影响

为解决污水处理厂进水碳氮比偏低、碳源不足,导致生物反硝化效果不理想这个困扰业界的难题,采用改良型Carrousel氧化沟耦合工艺处理低B/C比、低碳氮比的某混合工业废水,投加乙酸碳源,其他按照污水厂日常运行参数运营,结果表明,投加乙酸碳源对该工业污水处理厂改良型Carrousel氧化沟去除总氮、氨氮和pH等效果理想,出水完全达到《城镇污水处理厂污染物排放标准》(GB 19918—2002)一级A标准.低碳氮比的工业污水处理可以选用乙酸作碳源以强化生物脱氮,乙酸实际合适的平均投加量为211.97 mg/L,投加成本为0.254元/t,该工艺的稳定运行为低碳氮比的工业污水处理系统优化设计及提标改造提供了有益的参考和借鉴.

低碳氮比进水条件下一体化氧化沟在高原污水处理中的应用及调试

为揭示一体化氧化沟在高原环境下消纳城市生活污水的特性与机制,以贵州某污水厂的一体化氧化沟污水处理设施为研究对象,通过对该设施在同条件下实现提标改造的可行性进行研究。结果表明,在低进水负荷条件下(ρ(BOD)/ρ(COD)为0.25~0.3),控制氧化沟曝气池中pH值及DO的质量浓度(分别为7.3~7.6,2.1~2.4 mg/L),氧化沟出水即可满足GB 3838-2002一级A标准,后续可从调整污泥回流比、加长污泥泥龄、控制前置厌氧池流速等方面采取措施以提高其脱氮除磷效率。