Novel strategy of nitrogen removal from domestic wastewater using pilot Orbal oxidation ditch

A pilot-scale Orbed oxidation ditch was operated for 17 months to optimize nitrogen removal from domestic wastewater of average COD to total nitrogen ratio of 2.7, with particular concern about the roles of dissolved oxygen （DO）, mixed liquor suspended solids （MLSS） and return activated sludge （RAS） recycle ratio. Remarkable simultaneous nitrification and denitrification （SND） was observed and mean total nitrogen （TN） removal efficiency up to 72.1% was steadily achieved, at DO concentration in the out, middle and inner channel of 0.1, 0.4 and 0.7 mg/L, respectively, with an average M LSS of 5.5 g/L and RAS recycle ratio of 150%. Although the out channel took the major role in TN removal, the role of middle channel should never be ignored. The denitrification potential could be fully developed under low DO, high MLSS with adequate RAS ratio. The sludge settleability was amazingly improved under low DO operation mode, and some explanations were tried. In addition, a scries of simplified batch tests were done to determine whether novel microorganisms could make substantial contribution to the performance of nitrogen removal. The results indicated that the SND observed in this Orbal oxidation ditch was more likely a physical phenomenon.     

A novel approach to treat combined domestic wastewater and excess sludge in MBR

Domestic wastewater was treated by combined anaerobic biofilm-aerobic membrane bioreactor(MBR) process, and part biomass in MBR was withdrawn, to treat with ozone, then the ozonated sludge was returned to anaerobic inlet. In aerobic MBR, MLSS and DO were controlled at 3000—3500 mg/L and 0.8 mg/L respectively. Comparing the experimental results of two stages, it was noticed that ozonation did not affect the removal efficiency for organics but had a significant influence on the removals of NHs-N and TN. During the ozonation period of two months, no excess sludge was wasted, and a zero sludge yield was obtained.     

Control of membrane fouling during hyperhaline municipal wastewater treatment using a pilot-scale anoxic/aerobic-membrane bioreactor system

Membrane fouling limits the effects of long-term stable operation of membrane bioreactor (MBR). Control of membrane fouling can extend the membrane life and reduce water treatment cost effectively. A pilot scale anoxic/aerobic-membrane bioreactor (A/O-MBR, 40 L/hr) was used to treat the hyperhaline municipal sewage from a processing zone of Tianjin, China. Impact factors including mixed liquid sludge suspension (MLSS), sludge viscosity (μup), microorganisms, extracellular polymeric substances (EPS), aeration intensity and suction/suspended time on membrane fouling and pollution control were studied. The relationships among various factors associated with membrane fouling were analyzed. Results showed that there was a positive correlation among MLSS, sludge viscosity and trans-membrane pressure (TMP). Considering water treatment efficiency and stable operation of the membrane module, MLSS of 5 g/L was suggested for the process. There was a same trend among EPS, sludge viscosity and TMP. Numbers and species of microorganisms affected membrane fouling. Either too high or too low aeration intensity was not conducive to membrane fouling control. Aeration intensity of 1.0 m³/hr (gas/water ratio of 25:1) is suggested for the process. A long suction time caused a rapid increase in membrane resistance. However, long suspended time cannot prevent the increase of membrane resistance effectively even though a suspended time was necessary for scale off particles from the membrane surface. The suction/suspended time of 12 min/3 min was selected for the process. The interaction of various environmental factors and operation conditions must be considered synthetically.     

Simultaneous nitrification and denitrification in step feeding biological nitrogen removal process

The simultaneous nitrification and denitrification in step-feeding biological nitrogen removal process were investigated under different influent substrate concentrations and aeration flow rates.Biological occunenee of simultaneous nitrification and denitrification was verified in the aspect of nitrogen mass balance and alkalinity.The experimental results also showed that there was a distinct linear relationship between simultaneous nitrification and denitrification and DO concentration under the conditions of low and high aeration flow rate.In each experimental run the floc sizes of activated sludge were also measured and the results showed that simultaneous nitrification and denitriflcation could occur with very small size of floc.     

Study on membrane fouling of submerged membrane bioreactor in treating bathing wastewater

A pilot-scale submerged membrane bioreactor (MBR) was used to treat the bathing wastewater for more than 90 d. Several factors affecting membrane fouling were studied, including the variation in transmembrane pressure (TMP), changes in extracellular polymeric substance (EPS), and distribution of membrane resistance (R). The relationships between R and EPS concentration were found to be R = 0.00008(EPSS)2.915 in the mixed liquor (EPSS) and R = 0.2853(EPSm) - 0.824 on the membrane surface (EPSm). The constant...     

Treating both wastewater and excess sludge with an innovative process

The innovative process consists of biological unit for wastewater treatment and ozonation unit for excess sludge treatment. An aerobic membrane bioreactor( MBR ) was used to remove organics and nitrogen, and an anaerobic reactor was added to the biological unit for the release of phosphorus contained at aerobic sludge to enhance the removal of phosphorus. For the excess sludge produced in the MBR, which was fed to ozone contact column and reacted with ozone, then the ozonated sludge was returned to the MBR for further biological treatment. Experimental results showed that this process could remove organics, nitrogen and phosphorus efficiently, and the removals for COD, NH3-N, TN and TP were 93.17%, 97.57%, 82.77% and 79.5%, respectively. Batch test indicated that the specific nitrification rate and specific denitrifieation rate of the MBR were 1.03 mg NH3-N/(gMLSS^ h) and 0.56 mg NOx-N/(gMLSS^ h), and denitrification seems to be the rate-limiting step. Under the test conditions, the sludge concentration in the MBR was kept at 5000--6000 rng/L, and the wasted sludge was ozenated at an ozone dosage of 0.10 kgO3/kgSS. During the experimental period of two months, no excess sludge was wasted, and a zero withdrawal of excess sludge was implemented. Through economic analysis, it was found that an additional ozonation operating cost for treatment of both wastewater and excess sludge was only 0. 045 RMB Yuan( USD 0.0054)/m^3 wastewater.     

Bioaugmentation with a pyridine-degrading bacterium in a membrane bioreactor treating pharmaceutical wastewater

The bacterial strain Paracoccus denitrificans W12, which could utilize pyridine as its sole source of carbon and nitrogen, was added into a membrane bioreactor （MBR） to enhance the treatment of a pharmaceutical wastewater. The treatment efliciencies investigated showed that the removal of chemical oxygen demand, total nitrogen, and total phosphorus were similar between bioaugmented and non-bioaugmented MBRs, however, significant removal of pyridine was obtained in the bioaugmented reactor. When the hydraulic retention time was 60 hr and the influent concentration of pyridine was 250-500 mg/L, the mean effluent concentration of pyridine without adding W12 was 57.2 mg/L, while the pyridine was degraded to an average of 10.2 mg/L with addition of W12. The bacterial community structure of activated sludge during the bioaugmented treatment was analyzed using polymerase chain reaction-denaturing gradient gel electrophoresis （PCR-DGGE）. The results showed that the W12 inoculum reversed the decline of microbial community diversity, however, the similarity between bacterial community structure of the original sludge and that of the sludge after bioaugmentation decreased steadily during the wastewater treatment. Sequencing of the DNA recovered from DGGE gel indicated that sp., Sphingobium sp., Comamonas sp., and Hyphomicrobium sp. were the dominant organisms in time sequence in the bacterial community in the bioaugmented MBR. This implied that the bioaugmentation was affected by the adjustment of whole bacterial community structure in the inhospitable environment, rather than being due solely to the degradation performance of the bacterium added.     

Coagulation efficiency and flocs characteristics of recycling sludge during treatment of low temperature and micro-polluted water

Drinking water treatment sludge, characterized as accumulated suspended solids and organic and inorganic matter, is produced in large quantities during the coagulation process. The proper disposal, regeneration or reuse of sludge is, therefore, a significant environmental issue. Reused sludge at low temperatures is an alternative method to enhance traditional coagulation efficiency. In the present study, the recycling mass of mixed sludge and properties of raw water (such as pH and turbidity) were systematically investigated to optimize coagulation efficiency. We determined that the appropriate dosage of mixed sludge was 60 mL/L, effective initial turbidity ranges were below 45.0 NTU, and optimal pH for DOMs and turbidity removal was 6.5--7.0 and 8.0, respectively. Furthermore, by comparing the flocs characteristics with and without recycling sludge, we found that floc structures with sludge were more irregular with average size growth to 64.7 μupm from 48.1 μupm. Recycling sludge was a feasible and successful method for enhancing pollutants removal, and the more irregular flocs structure after recycling might be caused by breakage of reused flocs and incorporation of powdered activated carbon into larger flocs structure. Applied during the coagulation process, recycling sludge could be significant for the treatment of low temperature and micro-polluted source water.     

Test of membrane bioreactor for waste water treatment in a petrochemical complex

Membrane bioreactor (MBR) used in water and waste water treatment is a developing technique for water pollution control and water reuse. This paper describes a membrane-bioreactor for treatment of waste water in a petrochemical complex. The experimental MBR was a lab scale one composed of an activated sludge bioreactor unit and an ultrafiltration membrane unit. The relationship of COD removal with MLSS and HRT in this MBR was studied. The effects of crossflow velocity, backwash interval and volume of flush liquid on the flux were discussed. The results showed that average removal of COD, oil, SS and turbidity in petrochemical waste water by the MBR was 91%, 86%, 92% and 99% respectively. The average removal of NH₃-N and total phosphorous was 85% and 82%. A coefficient of COD removal, k, was 0.017-0.080 L/(mg.d). The membrane flux maintained higher than 60 L/hm2 bar for 34 days without chemical cleaning when the velocity of crossflow was 3.5-3.9 m/s and the backwash interval was 30 minutes and backwash duration at 20 seconds. The results indicated that it is feasible for MBR technology to be used in petrochemical waste water treatment. The treated water could be considered as a source used to make up water for industrial cooling system or to be reused for other purposes.     

Start-up of the anammox process from the conventional activated sludge in a hybrid bioreactor

The anaerobic ammonium oxidation (anammox) process was successfully started up from conventional activated sludge using a hybrid bioreactor within 2 months. The average removal efficiencies of ammonia and nitrite were both over 80%, and the maximum total nitrogen removal rate of 1.85 kg N/(m³.day) was obtained on day 362 with the initial sludge concentration of 0.7 g mixed liquor suspended solids (MLSS)/L. Scanning electron microscope (SEM) observation of the granular sludge in the hybrid reactor clearly showed a high degree of compactness and cell sphericity, and the cell size was quite uniform. Transmission electron microscope photos showed that cells were round or oval, the cellular diameter was 0.6--1.0 μupm, and the percentage of the anammoxosome compartment was 51%--85% of the whole cell volume. Fluorescence in situ hybridization analysis (FISH) indicated that anammox bacteria became the dominant population in the community (accounting for more than 51% of total bacteria on day 250). Seven planctomycete 16S rRNA gene sequences were present in the 16S rRNA gene clone library generated from the biomass and affiliated to Candidatus Kuenenia stuttgartiensis and Candidatus Brocadia sp., a new anammox species. In addition, the average effluent suspended solid (MLSS) concentrations of outlets I (above the non-woven carrier) and II (below the non-woven carrier) were 0.0009 and 0.0035 g/L, respectively. This showed that the non-woven carrier could catch the biomass effectively, which increased biomass and improved the nitrogen removal rate in the reactor.     

臭氧作用改善膜-生物反应器混合液膜过滤性

提出了利用臭氧作为调控膜-生物反应器中活性污泥混合液的方法,采用小膜过滤装置测定臭氧作用后混合液的膜过滤性变化,并通过测定混合液MLSS、胞外多聚物(EPS)含量、絮体粒径、上清液胶体有机物浓度、黏度的变化,探讨了混合液膜过滤性变化的原因.结果表明,当臭氧投加量低于8.5mg/L条件下,混合液的膜过滤性得到改善.臭氧对混合液的主要作用是氧化污泥絮体表面的部分EPS,使污泥絮体表面性质发生改变,引起絮体再絮凝,絮体粒径增大,上清液胶体有机物浓度和黏度减少,从而改善混合液的膜过滤性质.     

移动床膜生物反应器同步硝化反硝化特性

采用挂膜填料代替传统膜生物反应器(MBR)的活性污泥,构建一种新型的移动床膜生物反应器 (MBMBR),考察其处理模拟生活污水的效果及同步硝化反硝化(SND)特性.结果表明,移动床膜生物反应器运行67 d,对模拟生活污水表现出良好的去除有机物及同步硝化反硝化能力.进水COD浓度为573.5～997.7 mg/L时,膜出水COD去除率为88.3%～99.2%.进水氨氮浓度为45.5～99.2 mg/L时,膜出水氨氮去除率为72.1%～99.8%,总氮去除率为62.0%～96.3%.批式实验结果表明,生物膜去除总氮的最佳溶解氧浓度为1 mg/L,其中氨氮和总氮去除率分别为100%和60%.生物膜系统内可能存在好氧反硝化现象.DO为3 mg/L且有机碳源充足时,生物膜总氮去除率为99.0%,SND率达到99.8%.扫描电镜对生物膜的观察发现生物膜内部存在着明显的孔隙,有利于溶解氧和有机基质从外界向生物膜内部传递.     

膜生物反应器处理高浓度含酚废水研究

将膜生物反应器(MBR)用于高浓度含酚废水的处理中,探讨了进水中苯酚浓度、水力停留时间和污泥浓度对膜生物反应器处理含酚废水效果的影响。实验结果表明:经过42d驯化后,可以在高浓度含酚废水中正常运行,MBR系统对COD和氨氮的去除率分别可达98%和80.6%。当苯酚浓度为134mg/L时,处理的最佳水力停留时间为3h,最佳污泥浓度(MLSS)为7367mg/L。     

溶解氧对膜生物反应器处理高氨氮废水的影响

采用膜生物反应器(MBR)处理高氨氮有机废水,探讨了溶解氧(DO)对有机物、氨氮、总氮等去除效果的影响。当进水COD1500mg/L,NH4+-N150mg/L,TP为15mg/L,pH7.5～8.0,MLSS控制在6000～7000mg/L,DO在0.5～4mg/L时对COD的去除效果没有明显影响,都可高达95%;在DO为4.0和2.0mg/L时对NH4+-N的去除率都很高,最高可达99.17%,在DO为0.5mg/L时明显降低,最低降至48.30%。在DO2.0mg/L时,取得了较好的同步硝化反硝化效果,COD、NH4+-N、TN去除率分别高达97%、97%、68%。MBR中硝化反应的比氨氮消耗速率与氨氮浓度成零级反应动力学,比氨氮硝化速率为0.0979/d,比常规处理系统中的污泥硝化活性高。     

金属膜生物反应器处理生活污水膜污染的影响因素

采用浸没式平板金属膜生物反应器处理模拟生活污水,考察好氧与缺氧/好氧(anoxic/oxic, A/O) 2种运行模式下ρ(MLSS)和污泥粒径分布对膜过滤性能的影响及膜过滤阻力的组成. 结果表明,对于好氧膜生物反应器,存在一个能获得良好膜过滤性能的ρ(MLSS)范围; 好氧模式下膜过滤阻力主要为滤饼层阻力,且滤饼层能通过在线药洗或机械清洗较好地去除,系统在膜通量为0.80～1.00 　m3/(m2·d)下未进行离线药洗连续运行115 d. A/O模式下膜过滤阻力主要为内部阻力; A/O循环导致污泥破碎解体,产生大量微小粒子,在膜孔内形成吸附和堵塞,使膜过滤性能急剧下降,为维持系统运行,A/O阶段将膜通量从1.00 　m3/(m2·d)降至0.50 　m3/(m2·d),并进行了15次膜清洗.      

浸没板式MBR处理生活污水造成膜堵塞的关键因素

采用浸没板式膜生物反应器对大学学生宿舍与食堂混合排水进行处理,试验系统应用A/O工艺,设置硝化槽与反硝化槽,日处理生活污水4 m3.当进水ρ(BOD₅)和ρ(COD_Cr)分别为90～450和120～900 mg/L时,出水ρ(BOD₅)和ρ(CODCr)分别为5～25和8～45 mg/L,去除率均较高.同时对膜污染进行了试验研究,阐述了ρ(MLSS),污泥粒径分布以及原水成分造成膜污染的机理.发现污泥粒径分布随ρ(MLSS)变化而发生改变,当ρ(MLSS)达到20.000 g/L以上时,污泥粒径明显减小,同时可导致膜污染的细微颗粒分布相对增高,这一现象得到ρ(MLSS)超过20.000 g/L时膜污染加剧的试验验证.      

UASB-膜生物反应器处理抗生素废水的研究

采用UASB-膜生物反应器对抗生素废水进行处理研究。结果表明,UASB具有很强的抗冲击能力,当UASB和膜生物反应器的容积负荷分别为10.9kgCOD/m3·d和4.62kgCOD/m3·d时,系统COD去除率仍有96.47%。污泥浓度对膜生物反应器的COD去除率有较大影响,当MLSS保持在3000～4000mg/L时,膜生物反应器COD去除率为85%左右,高于MLSS保持在7500～7800mg/L时为68%左右。在不排泥运行时膜生物反应器中MLVSS和MLSS比值比排泥运行时低。     

好氧颗粒污泥膜生物反应器的运行特性

以人工合成模拟废水对好氧颗粒污泥膜生物反应器(MBR)的运行特性和膜污染进行了研究.结果表明:在HRT为6h,溶氧浓度为4～6mg.L^-1,COD的容积负荷为7.24kg·(m³·d)^-1的条件下,COD的去除率可达96%以上.当NH₃-N的容积负荷为0.17kg·(m³·d)^-1时,NH₃-N的去除率可达60%.COD/N比的变化,对好氧颗粒污泥MBR的COD及NH₃-N去除率基本没有影响.稳定运行过程时,MBR中好氧颗粒污泥浓度(MLSS)基本维持在14～16mg·L^-1.较高的污泥浓度和颗粒污泥内部缺氧和厌氧环境的存在,使MBR中硝化和反硝化过程能同时存在.同时,比较了2种不同形态的活性污泥(颗粒污泥和絮状污泥)在MBR运行过程中膜通量的变化趋势,结果表明,颗粒污泥MBR膜通量的下降速度明显比絮状污泥MBR的下降速度慢很多,且通过空气反冲或用水清洗即可使通量基本恢复.     

一体式膜-生物反应器同步硝化反硝化中试试验

当污泥浓度维持在19~20g/L时,一体式平板膜-生物反应器运行112d,通量稳定在25.2~25.7L/(m2.h),运行过程除正常曝气以保持对膜进行水力冲刷外没有进行任何物理和化学清洗。试验考察不同DO浓度对同步硝化反硝化效果的影响,结果表明,反应器内有较好的硝化反硝化效应,当温度在18~12℃变动时,膜生物反应器的硝化反硝化效果基本不受温度的影响。