三种两段缺氧A~3/O-MBR工艺脱氮除磷效率分析

以太湖流域3座采用两段缺氧的A3/O—MBR工艺的城市污水处理厂(城北污水处理厂、硕放污水处理厂及太湖国家度假区污水处理厂)为研究对象,介绍其工程概况和主要运行参数。通过对这3座污水处理厂运行效果的分析比较,初步研究其脱氮除磷效率。结果表明,各污水处理厂的氮磷去除效果均较好,出水水质稳定达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)中的一级A排放标准,增加后置缺氧段的A2/O/A—MBR工艺强化了脱氮除磷功能,去除效果明显优于其他2座污水处理厂。     

内回流混合液溶解氧对工艺脱氮影响及其工程控制措施

针对高排放标准城镇污水处理厂运行中普遍存在内回流混合液携带溶解氧进入缺氧池导致工艺脱氮效能下降的实际问题,以太湖流域某市典型高排放标准城镇污水处理厂为例进行了分析,结果表明:太湖流域典型高排放标准城镇污水处理厂混合液内回流点溶解氧浓度较高,平均值为3.22mg/L,可导致工艺系统脱氮量平均下降2.41mg/L,内回流混合液溶解氧对工艺系统脱氮效能的不利影响显著。另外,提出了相应的工程控制措施——基于消氧池的强化脱氮方法,并提出消氧池的设计水力停留时间为0.5~1h。     

复合A/O硅藻精土工艺在小型城镇污水处理厂的应用

复合A/O硅藻精土工艺是将缺氧池、好氧池、沉淀池合建成一个复合A/O处理池,以减小占地面积,并在运行过程中投加硅藻精土,实现脱氮除磷的新型城镇污水处理工艺。广东省江门鹤山市古劳镇污水处理厂采用该工艺设计,运行数据表明,该工艺运行稳定,具有良好的脱氮除磷效果,出水水质稳定达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级B标准,适用于我国南方城镇污水处理厂进水水质浓度偏低的情形。     

CWSBR工艺在夏家河污水处理厂的应用

大连夏家河污水处理厂一期工程采用连续进出水的CWSBR(恒水位SBR)新工艺,经过两个多月的污泥培养和试运行,出水水质达到《城镇污水处理厂污染物排放标准》(GB18918—2002)一级A标准。采用单池一个循环周期多次进水的方式,有效强化了系统的抗冲击负荷能力和脱氮除磷性能,稳定运行阶段出水CODCr小于30mg/L,NH3—N连续为0,TN小于5mg/L,TP小于0.5mg/L。并通过采取较有效的应对措施缓解了低温条件对调试运行的不利影响,为CWSBR工艺在寒冷地区的应用积累了经验。     

溶解氧对低碳源污水一体化处理工艺脱氮除磷的影响

通过试验对比,研究了溶解氧对低碳源污水一体化工艺脱氮除磷效果的影响。结果表明,平均溶解氧为0.18mg/L时,系统出水可以稳定达到GB 18918—2002一级A标准,溶解氧过高或过低都会降低系统脱氮除磷效果。在平均溶解氧为0.18mg/L的工况下,系统存在反硝化吸磷、同时硝化反硝化及全程反硝化3种脱氮方式,且反硝化吸磷和同时硝化反硝化脱氮量占氮总去除量的66.7%,可以较大程度降低脱氮除磷过程所需碳源量并节省耗氧量,提高低碳源污水脱氮除磷效果。     

厌氧+立体循环脱氮除磷中试研究

我国新颁布的《城镇污水处理厂污染物排放标准》(GB18918—2002)明确规定了城市污水处理厂较为严格的磷酸盐和氨氮排放标准。因此现有的城市二级污水处理厂面临脱氮除磷改造的问题。     

我国城镇污水处理设施脱氮除磷能力现状分析及对策建议

分析了我国城镇污水处理设施脱氮除磷现状以及国外污水处理厂氮磷排放标准及处理工艺情况,通过对现行脱氮除磷主流技术的评价,提出针对我国城镇污水处理设施的脱氮除磷技术及管理对策建议。     

城镇污水处理厂强化生物脱氮试验研究

针对二级城镇污水处理厂提标改造时出水氮、磷指标很难同时达到一级A标准的实际情况,提出通过优化工艺运行参数,包括优先利用碳源进行生物脱氮、增加缺氧反硝化池容、降低回流混合液DO等方式,进行强化生物脱氮,首先使出水氮指标达到一级A标准,然后在深度处理单元采用化学方法除磷,使出水水质全面达到一级A标准。并通过生产性试验,探讨了强化生物脱氮的效果。试验结果表明,对于采用UNITANK工艺的污水处理厂,经过强化生物脱氮,出水氮指标能够稳定达到一级A的排放标准。     

城市污水处理厂脱氮除磷调控参数的研究

通过两年多对酒仙桥和清河污水处理厂脱氮除磷工作的实践,结合运行数据摸索最佳的工艺参数并及时进行调控,分析2006年两个污水处理厂的生产运行数据,总结出提高污水处理厂脱氮除磷水平的控制参数,以及出水达到<城镇污水处理厂污染物排放标准>(GB 18918-2002)一级A标准的控制策略.     

城市污水处理广氮磷达标排放新方法的研究

应用改性硅藻土陶粒填料滤池对城市污水处理厂尾水进行末端脱氮除磷深度处理,通过试验确定了改性硅藻土陶粒填料滤池设计参数,处理后出水水质可稳定达到<城镇污水处理厂污染物排放标准(GB 18918-2002)一级A标准,达到回用水和景观用水标准.改性硅藻土陶粒和生物脱氮除磷与化学除磷相比具有投资省、占地小、运行费用低等优点,具有广阔的应用前景.     

Treatment of slaughterhouse plant wastewater by using a membrane bioreactor

The use of a membrane bioreactor (MBR) for removal of organic substances and nutrients from slaughterhouse plant wastewater was investigated. The chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) concentrations of slaughterhouse wastewater were found to be approximately 571 mg O2/L, 102.5 mg/L, and 16.25 mg PO4-P/L, respectively. A submerged type membrane was used in the bioreactor. The removal efficiencies for COD, total organic carbon (TOC), TP and TN were found to be 97, 96, 65, 44% respectively. The COD value of wastewater was decreased to 16 mg/L (COD discharge standard for slaughterhouse plant wastewaters is 160 mg/L). TOC was decreased to 9 mg/L (TOC discharge standard for slaughterhouse plant wastewaters is 20 mg/L). Ammonium, and nitrate nitrogen concentrations of treated effluent were 0.100 mg NH4-N/L, and 80.521 mg NO3-N/L, respectively. Slaughterhouse wastewater was successfully treated with the MBR process.     

A novel wastewater treatment process: simultaneous nitrification, denitrification and phosphorus removal.

Simultaneous nitrification and denitrification (SND) via the nitrite pathway and anaerobic-anoxic enhanced biological phosphorus removal (EBPR) are two processes that can significantly reduce the COD demand for nitrogen and phosphorus removal. The combination of these two processes has the potential of achieving simultaneous nitrogen and phosphorus removal with a minimal requirement for COD. A lab-scale sequencing batch reactor (SBR) was operated in alternating anaerobic-aerobic mode with a low dissolved oxygen concentration (DO, 0.5 mg/L) during the aerobic period, and was demonstrated to accomplish nitrification, denitrification and phosphorus removal. Under anaerobic conditions, COD was taken up and converted to polyhydroxyalkanoates (PHA), accompanied with phosphorus release. In the subsequent aerobic stage, PHA was oxidized and phosphorus was taken up to less than 0.5 mg/L at the end of the cycle. Ammonia was also oxidised during the aerobic period, but without accumulation of nitrite or nitrate in the system, indicating the occurrence of simultaneous nitrification and denitrification. However, off-gas analysis found that the final denitrification product was mainly nitrous oxide (N2O) not N2. Further experimental results demonstrated that nitrogen removal was via nitrite, not nitrate. These experiments also showed that denitrifying glycogen-accumulating organisms rather than denitrifying polyphosphate-accumulating organisms were responsible for the denitrification activity.     

Alternate anoxic/aerobic operation for nitrogen removal in a membrane bioreactor for municipal wastewater treatment

A large pilot-scale membrane bioreactor (MBR) with a conventional denitrification/nitrification scheme for municipal wastewater treatment has been run for one year under two different aeration strategies in the oxidation/nitrification compartment. During the first five months air supply was provided according to the dissolved-oxygen set-point and the system run as a conventional predenitrification MBR; then, an intermittent aeration strategy based on effluent ammonia nitrogen was adopted in the aerobic compartment in order to assess the impact on process performances in terms of N and P removal, energy consumption and sludge reduction. The experimental inferences show a significant improvement of the effluent quality as COD and total nitrogen, both due to a better utilization of the denitrification potential which is a function of the available electron donor (biodegradable COD) and electron acceptor (nitric nitrogen); particularly, nitrogen removal increased from 67% to 75%. At the same time, a more effective biological phosphorus removal was observed as a consequence of better selection of denitrifying phosphorus accumulating organisms (dPAO). The longer duration of anoxic phases also reflected in a lower excess sludge production (12% decrease) compared with the standard pre-denitrification operation and in a decrease of energy consumption for oxygen supply (about 50%).     

Outcomes of a 2-year investigation on enhanced biological nutrients removal and trace organics elimination in membrane bioreactor (MBR).

Two configurations of membrane bioreactors were identified to achieve enhanced biological phosphorus and nitrogen removal, and assessed over more than two years with two parallel pilot plants of 2m3 each. Both configurations included an anaerobic zone ahead of the biological reactor, and differed by the position of the anoxic zone: standard pre-denitrification, or post-denitrification without dosing of carbon source. Both configurations achieved improved phosphorus removal. The goal of 50 microgP/L in the effluent could be consistently achieved with two types of municipal wastewater, the second site requiring a low dose of ferric salt ferric salt < 3 mgFe/L. The full potential of biological phosphorus removal could be demonstrated during phosphate spiking trials, where up to 1 mg of phosphorus was biologically eliminated for 10 mg BOD5 in the influent. The post-denitrification configuration enabled a very good elimination of nitrogen. Daily nitrate concentration as low as 1 mgN/L could be monitored in the effluent in some periods. The denitrification rates, greater than those expected for endogenous denitrification, could be accounted for by the use of the glycogene pool, internally stored by the denitrifying microorganisms in the anaerobic zone. Pharmaceuticals residues and steroids were regularly monitored on the two parallel MBR pilot plants during the length of the trials, and compared with the performance of the Berlin-Ruhleben WWTP. Although some compounds such as carbamazepine were persistent through all the systems, most of the compounds could be better removed by the MBR plants. The influence of temperature, sludge age and compound concentration could be shown, as well as the significance of biological mechanisms in the removal of trace organic compounds.     

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.     

Comparative study of MBR and activated sludge in the treatment of paper mill wastewater.

The study was based on a full scale activated sludge plant (AS) compared to a parallel operated pilot membrane bioreactor (MBR) with flat sheets membranes. Both systems received their influent from an anaerobic bioreactor treating paper mill wastewater. MBR produced an effluent of much better quality than AS in terms of suspended solids, containing 1 mg/L or less in 80% of the monitoring time, while the AS effluent contained 12 mg/L. This could save the necessity of further treatment by filtration in the case of MBR. Other effluent quality parameters, such as organic matter (COD and BOD), phosphorus and ammonia nitrogen, did not indicate substantial differences between AS and MBR. Calcium carbonate scaling and formation of a bacterial layer on the membrane caused severe flux reduction. The membrane blockage because of scaling and biofouling proved to be very serious, therefore, it required proper and more complicated maintenance than the AS system. This study leads to the conclusion that in the case of paper mill wastewater, after anaerobic biotreatment, if there is no need for excellent effluent quality in terms of suspended solids, the replacement of the AS by the MBR would not be strongly justified, mainly because of maintenance cost.     

Long term operation of high concentration powdered activated carbon membrane bio-reactor for advanced water treatment.

A pilot scale experiment was conducted to evaluate the performance of a membrane bioreactor filled with high concentration powdered activated carbon. This hybrid system has great potential to substitute for existing GAC or O3/BAC processes in the drinking water treatment train. The system was installed at a water treatment plant located downstream of the Nakdong river basin, Korea. Effluent of rapid sand filter was used as influent of the system which consists of PAC bio-reactor, submerged MF membrane module and air supply facility. PAC concentration of 20 g/L was maintained at the beginning of the experiment and it was increased to 40 g/L. The PAC has not been changed during the operational periods. The membrane was a hollow fiber type with pore sizes of 0.1 and 0.4 microm. It was apparent that the high PAC concentration could prevent membrane fouling. 40 g/L PAC was more effective to reduce the filtration resistance than 20 g/L. At the flux of 0.36 m/d, TMP was maintained less than 40 kPa for about 3 months by intermittent suction type operation (12 min suction/3 min idling). Adsorption was the dominant role to remove DOC at the initial operational period. However the biological effect was gradually increased after around 3 months operation. Constant DOC removal could be maintained at about 40% without any trouble and then a tremendous reduction of DBPs (HAA5 and THM) higher than 85% was achieved. Full nitrification was observed at the controlled influent ammonia nitrogen concentration of 3 and 7 mg/L. pH was an important parameter to keep stable ammonia oxidation. From almost two years of operation, it is clear that the PAC membrane bioreactor is highly applicable for advanced water treatment under the recent situation of more stringent DBPs regulation in Korea.     

BICT biological process for nitrogen and phosphorus removal.

An updated biological nitrogen and phosphorus removal process--BICT (Bi-Cyclic Two-Phase) biological process--is proposed and investigated. It is aimed to provide a process configuration and operation mode that has facility and good potential for optimizing operation conditions, especially for enhancing the stability and reliability of the biological nutrient removal process. The proposed system consists of an attached-growth reactor for growing autotrophic nitrifying bacteria, a set of suspended-growth sequencing batch reactors for growing heterotrophic organisms, an anaerobic biological selector and a clarifier. In this paper, the fundamental concept and operation principles of BICT process are described, and the overall performances, major operation parameters and the factors influencing COD, nitrogen and phosphorus removal in the process are also discussed based on the results of extensive laboratory experiments. According to the experimental results with municipal sewage and synthetic wastewater, the process has strong and stable capability for COD removal. Under well controlled conditions, the removal rate of TN can reach over 80% and TP over 90% respectively, and the effluent concentrations of TN and TP can be controlled below 15 mg/L and 1.0 mg/L respectively for municipal wastewater. The improved phosphorus removal has been reached at short SRT, and the recycling flow rate of supernatant between the main reactors and attached-growth reactor is one of the key factors controlling the effect of nitrogen removal.     

Experiences on dual media filtration of WWTP effluent

This research is legislation driven by the European Water Framework Directive (WFD) and the Dutch Fourth Memorandum on Water Management. The objective of this research is to achieve the removal of total nitrogen and total phosphorus by Dual Media Filtration. The target value during this research for total nitrogen is 2.2 mg/L and for total phosphorus 0.15 mg/L. The results show that for NOx-N concentrations in the WWTP effluent up to 10 mg/L, a stable operation of the process can be reached with removal rates of 80% to 90%. The maximum nitrogen removal rate was 3.5 kg N/(m3.d). Above 10 mg/L a risk of filter bed clogging occurred. When the orthophosphorus concentration in the WWTP effluent exceeds the maximum of 0.3 mg/L, the total phosphorus concentration in the filtrate water will exceed the target value of 0.15 mg P-total/L. Temperature has a large impact in the phosphorus removal; the optimum temperature range is within 13 degrees C-18 degrees C. In conclusion, Dual Media Filtration is capable of producing reusable water with total phosphorus concentrations of <0.15 mg/L, under the condition that the wastewater treatment plant produces WWTP effluent with steady concentrations for orthophosphorus (<0.3 mg PO4-P/L). To reach total nitrogen concentrations in the filtrate water of <2.2 mg/L a NOx-N removal efficiency of nearly 100% is required.     

Effect of phosphorus concentration on phosphorus removal and biomass

Membrane bioreactor (MBR) process was employed to study the effect of biological phosphorus removal (bio-P removal) and P-content in treated sludge with increased phosphorus concentration present in the wastewater. Further, the following four test fractions of raw wastewaters was obtained having different P-concentrations viz., run 1: P-20 mg/L, run 2: P-40 mg/L, run 3: P-60 mg/L, run 4: P-80 mg/L. The effective P-removal obtained for these four test fractions were found to be 23.07 mg/L (98.17%), 41.35 mg/L (88.16%), 45.75 mg/L (72.04%) and 55.80 mg/L (66.82%) respectively for run 1, 2, 3 and 4 fractions. Moreover, the similar increase in phosphorous concentration i.e., from 20 to 80 mg/L caused an apparent increase in total solid (TS) values from 7 to 8.3 g TS/L, whereas the total volatile solid (TVS) content remained constant (i.e. 4.5 g TVS/L). These results inferred that the proportion of TVS in the TS decreased from 70 to 55%. Moreover, by increasing the initial P-concentration from 20 to 80 mg/L, the corresponding P-proportion of excess sludge was increased from 2 to 6.2%.