Organic matter removal in combined anaerobic-aerobic fixed-film bioreactors

A combination of two fixed-film bioreactors (FFB) with arranged media, the first anaerobic and the second aerobic, connected in series with recirculation was fed continuously for 133 days with wastewater from a poultry slaughterhouse. Oxidation of the organic carbon compounds and nitrification were carried out in the aerobic FFB and methanogenesis and denitrification were performed in the anaerobic FFB. The average organic loading rate was 0.39 kg COD/m3d and 92% removal efficiencies of organic matter were achieved. COD-removal occurred mainly in the anaerobic FFB, increasing when the recirculation ratio rose from 1 to 6 due to the increase in the anoxic denitrification. The influence of the C/N ratio of the raw wastewater over the proportion in which the COD-removal was carried out by oxidation in the aerobic FFB, methanogenesis or denitrification in the anaerobic FFB was studied. When the volume of the aerobic FFB became smaller than that of the anaerobic one the fraction of organic matter removed in the anaerobic FFB increased, but also the ratio between the respective volumetric rates (rCODan/rCODae) increased. High recirculation and low C/NO-N ratio in the anaerobic FFB feed favoured the denitrification to the detriment of the methanogenic process. Regarding nitrogen removal for nitrogen applied loads around 0.064 kg TKN/m3d the removal efficiency was of 95%, which decreased to 84% for 0.14 kg TKN/m3d. The stability of the nitrification process was the controlling factor of the nitrogen removal. High ammonia concentration caused by high recirculation ratio, specially when the aerobic FFB volume was smaller, caused nitrification inhibition which destabilised the system.     

好氧颗粒污泥技术用于味精废水处理的研究

以厌氧颗粒污泥为接种污泥,采用人工模拟废水在SBR反应器内培养好氧颗粒污泥,35 d后颗粒污泥成熟,反应器对COD和NH4+-N的去除率分别高于95%和99%。采用该反应器处理味精废水,当COD、NH4+-N的容积负荷分别为2.4、0.24 kg/(m3.d)时,对COD、NH4+-N和TN的去除率分别在90%、99%和85%左右,且颗粒污泥未出现解体的现象。以厌氧颗粒污泥为接种污泥、味精废水为进水,在与上述相同条件下培养好氧颗粒污泥,经过60 d的培养,反应器内的污泥以絮状污泥为主,该系统对COD、NH4+-N和TN的去除率分别为85%、99%和70%。     

Simultaneous carbon and nitrogen removal from high strength domestic wastewater in an aerobic RBC biofilm

High strength domestic wastewater discharges after no/partial treatment through sewage treatment plants or septic tank seepage field systems have resulted in a large build-up of groundwater nitrates in Rajasthan, India. The groundwater table is very deep and nitrate concentrations of 500-750 mg/l (113-169 as NO3(-)-N) are commonly found. A novel biofilm in a 3-stage lab-scale rotating biological contactor (RBC) was developed by the incorporation of a sulphur oxidising bacterium Thiosphaera pantotropha which exhibited high simultaneous removal of carbon and nitrogen in fully aerobic conditions. T. pantotropha has been shown to be capable of simultaneous heterotrophic nitrification and aerobic denitrification thereby helping the steps of carbon oxidation, nitrification and denitrification to be carried out concurrently. The first stage having T. pantotropha dominated biofilm showed high carbon and NH4(+)-N removal rates of 8.7-25.9 g COD/m2 d and 0.81-1.85 g N/m2 d for the corresponding loadings of 10.0-32.0 g COD/m2 d and 1.0-3.35 g N/m2 d. The ratio of carbon removed to nitrogen removed was close to 12.0. The nitrification rate increased from 0.81 to 1.8 g N/m2 d with the increasing nitrogen loading rates despite a high simultaneous organic loading rate. However, it fell to 1.53 g N/m2 d at a high load of 3.35 g N/m2 d and 32 g COD/m2 d showing a possible inhibition of the process. A simultaneous 44-63% removal of nitrogen was also achieved without any significant NO2(-)-N or NO3(-)-N build-up. The second and third stages, almost devoid of any organic carbon, acted only as autotrophic nitrification units, converting the NH4(+)-N from stage 1 to nitrite and nitrate. Such a system would not need a separate carbon oxidation step to increase nitrification rates and no external carbon source for denitrification. The alkalinity compensation during denitrification for that destroyed in nitrification may also result in a high economy.     

Organic removal by denitritation and methanogenesis and nitrogen removal by nitritation from landfill leachate

A system consisting of a two-stage UASB and anoxic-oxic reactor was used to enhance COD and nitrogen removal from landfill leachate. To improve denitrification efficiency, the raw leachate with recycled final effluent was pumped into the first-stage UASB (UASB1) to carry out simultaneous denitrification and methanogenesis. The results over 180 d show that the maximum organic removal rate in UASB1 and UASB2 was 12.5 and 8.5 kgCODm(-3)d(-1) in the oxic zone of the A/O reactor, respectively. The COD and biochemical oxygen demand (BOD5) removal efficiency of the system was 80-92% and about 99%, respectively. Without controlling temperature (17-30 degrees C) and dissolved oxygen (0.5-4.0 mgL(-1)), the maximum NH4+-N removal rate was 0.68 kg NH4+-Nm(-3)d(-1), and about 99% of NH4+-N removal was obtained by nearly complete nitritation. The 81-93% total nitrogen removal was obtained by complete denitrification in the UASB1 and in the anoxic zone of the A/O reactor. Fluorescence in situ hybridization (FISH) analysis of the sludge samples from A/O reactor showed that ammonia oxidizing bacteria (AOB) consisted 4% of the eubacterium, while nitrite oxidizing bacteria (NOB) counted less than 0.2% of that. The study shows that the main factors achieving and maintaining nitritation are a proper range of free ammonia concentration obtained by dilution recycled final effluent that inhibits NOB but not AOB; effective control on aeration time by indication of "ammonia valley" on pH profile; and highly efficient denitrification and its reproducing alkalinity to result in pH above 8.5.     

间歇膨胀复合厌氧工艺用于处理抗生素废水

采用间歇膨胀复合厌氧/A-O-SBR工艺处理高浓度制药废水,在进水有机负荷为2.134～11.488 kgCOD/(m3.d)、pH值为4.5～6的常温条件下,厌氧反应器COD去除率>70%,容积负荷可达到9.075 kgCOD/(m3.d)。厌氧出水经A-O-SBR及混凝气浮处理后,出水COD、氨氮、总磷、pH值分别为130 mg/L、4.4 mg/L、2.39 mg/L、7.8,完全满足企业所在地的纳管排放要求。     

Integrated anaerobic-aerobic fixed-film reactor for slaughterhouse wastewater treatment

An integrated anaerobic-aerobic fixed-film pilot-scale reactor with arranged media was fed during 166 days with slaughterhouse wastewater. Operation temperature was 25 degrees C and the anaerobic-aerobic volume ratio was decreased from 4:1 to 3:2 and finally to 2:3. Overall organic matter removal efficiencies of 93% were achieved for an average organic loading rate of 0.77 kg COD/m3 d, and nitrogen removal efficiencies of 67% were achieved for nitrogen loading rates of 0.084 kg N/m3 d. The high internal recirculation associated to the air-lift effect linked to the aeration of a part of the reactor section caused high mixing between the anaerobic and aerobic zones, so that most organic matter was removed aerobically. The nitrification process achieved an efficiency of 91% for nitrogen loads of 0.15 kg N/m3 d when the anaerobic-aerobic volume ratio was 2:3 and was limited by dissolved oxygen concentration below 3 mg/l. The influence of the heterotrophic biomass growing in the outer biofilm was checked. Denitrification only implied the 12-34% of the total nitrogen removal and was limited by dissolved oxygen concentration in the anaerobic zone above 0.5 mg/l caused by the mixing regime. Most removed nitrogen was employed in synthesis of heterotrophic bacteria.     

应用SBR实现有机废水厌氧氨氧化生物脱氮的研究

采用SBR反应器,以硝化污泥和厌氧氨氧化(ANAMMOX)颗粒污泥的混合污泥为接种污泥,以有机模拟废水为研究对象,进行了厌氧氨氧化生物脱氮工艺研究。结果表明,在控制温度为25℃,水力停留时间为12 d,pH值为7.2～8.5,进水NH4+-N为220 mg/L左右、NO2--N为138 mg/L左右、COD为294 mg/L的条件下成功启动了SBR反应器。在高氨氮、低有机物浓度的条件下,ANAMMOX菌和异养反硝化菌能够实现共存,且ANAMMOX菌仍能成为优势菌属,AN-AMMOX反应是反应器中的主导反应。镜检发现,优势菌尺寸约为1μm,呈圆形或椭圆形,成簇聚生,表面可观察到明显的漏斗状缺口,具有典型的厌氧氨氧化菌特征。污泥中形成了以厌氧氨氧化球状菌为主、其他杆状菌和丝状菌共存的微生物混培体。     

SBR中好氧颗粒污泥的培养与除污效能

以普通絮状活性污泥为种泥，采用人工配水，通过控制运行条件在SBR中成功地培养出了好氧颗粒污泥。研究表明，该好氧颗粒污泥具有良好的同步硝化反硝化和去除COD的性能。好氧颗粒污泥成熟后平均直径为4～5mm，沉速为72～90m／h，反应器中MLSS为7．8g／L，使反应器对COD和NH3-N的去除率分别达到了95％～98％和75％～90％。     

Biological nitrogen removal from municipal landfill leachate: low-cost nitrification in biofilters and laboratory scale in-situ denitrification

The slow leaching of nitrogen from solid waste in landfills, resulting in high concentrations of ammonia in the landfill leachate, may last for several decades. The removal of nitrogen from leachate is desirable as nitrogen can trigger eutrophication in lakes and rivers. In the present study, a low-cost nitrification-denitrification process was developed to reduce nitrogen load especially in leachates from small landfills. Nitrification was studied in laboratory and on-site pilot aerobic biofilters with waste materials as filter media (crushed brick in upflow filters and bulking agent of compost in a downflow filter) while denitrification was studied in a laboratory anoxic/anaerobic column filled with landfill waste. In the laboratory nitrification filters, start-up of nitrification took less than 3 weeks and over 90% nitrification of leachate (NH4-N between 60 and 170mg N l(-1), COD between 230 and 1,300 mg l(-1)) was obtained with loading rates between 100 and 130 mgNH4-N l(-1) d at 25 degrees C. In an on-site pilot study a level of nitrification of leachate (NH4-N between 160 and 270 mg N l(-1), COD between 1,300 and 1,600 mg l(-1)) above 90% was achieved in a crushed brick biofilter with a loading rate of 50mg NH4-N l(-1) d even at temperatures as low as 5-10 degrees C. Ammonium concentrations in all biofilter effluents were usually below the detection limit. In the denitrification column. denitrification started within 2 weeks and total oxidised nitrogen in nitrified leachate (TON between 50 and 150mg N l(-1)) usually declined below the detection limit at 25 degrees C, whereas some ammonium, probably originating from the landfill waste used in the column, was detected in the effluent. No adverse effect was observed on the methanation of waste in the denitrification column with a loading rate of 3.8 g TON-N/t-TS(waste) d. In conclusion, nitrification in a low-cost biofilter followed by denitrification in a landfill body appears applicable for the removal of nitrogen in landfill leachate in colder climates.     

内循环UASB处理酒精废水及其颗粒污泥特性

针对传统UASB反应器在启动时颗粒污泥形成缓慢的问题,采用内循环UASB反应器作为厌氧单元对酒精废水进行处理。其以低负荷启动,启动完成后容积负荷为7.9 kg/(m3.d),对COD的去除率可达80%,整个试验阶段对NH3-N的平均去除率为16.38%。扫描电镜显示颗粒污泥中的优势菌开始为短杆菌,随着培养时间的延长则出现了球菌;而现有UASB反应器中颗粒污泥的优势菌为丝状菌。对沼气成分进行分析,CH4含量最高为81.61%,N2含量则随着颗粒污泥培养时间的延长由3.68%增加至18.59%。     

SMSBR去除焦化废水中有机物及氮的特性

选用一体化膜—序批式生物反应器 (SubmergedMembraneSequencingBatchReac tor ,简称SMSBR)处理焦化废水 ,考察了能否通过膜分离的强化作用提高生物处理系统对焦化废水的处理效果 ,使出水COD达到新的排放标准 ( <10 0mg/L) ,并提高脱氮效率。研究结果表明 :在HRT为 32 .7h ,平均COD容积负荷为 0 .4 5kg/ (m3·d)的条件下 ,出水COD可以稳定在 10 0mg/L以下 (平均为 86.4mg/L) ;要使COD达到新的排放标准 ,进水COD容积负荷应低于 0 .67kg/ (m3·d) (该负荷下出水COD在 10 0mg/L上下波动 ,平均为 10 6.3mg/L) ;好氧段存在明显的反硝化现象 ,使COD的去除得到强化 ;在保证系统温度、碱度、溶解氧和不受进水COD负荷冲击的情况下 ,出水NH3-N可低于 1mg/L ,但泥龄太长所产生的微生物代谢产物抑制了硝化反应过程中的硝酸盐细菌 ,使好氧段出水NO2 -N/NOx-N平均为 91.1% ,因此系统获得极其稳定高效的短程硝化作用 ,有利于进一步脱氮 ;按“缺氧 1—好氧—缺氧 2”方式运行时 ,若“缺氧 2”的HRT>8.4 4h ,可实现 81.34 %的反硝化率 (外加碳源 :COD/N为 2 .1g/g) ,平均TN去除率为 87.2 % ,最高达 90 .2 %。     

Piggery wastewater treatment using Alcaligenes faecalis strain No. 4 with heterotrophic nitrification and aerobic denitrification

Alcaligenes faecalis strain No. 4, which has heterotrophic nitrification and aerobic denitrification abilities, was used to treat actual piggery wastewater containing high-strength ammonium under aerobic conditions. In a continuous experiment using a solids-free wastewater (SFW) mixed with feces, almost all of the 2000 NH4+ -N mg/L and 12,000 COD mg/L in the wastewater was removed and the ammonium removal rate was approximately 30 mg-N/L/h, which was 5-10 times higher than the rates achieved by other bacteria with the same abilities. The denitrification ratio was more than 65% of removed NH4+ -N, indicating that strain No. 4 exhibited its heterotrophic nitrification and aerobic denitrification abilities in the piggery wastewater.     

Macroscale and microscale analyses of nitrification and denitrification in biofilms attached on membrane aerated biofilm reactors

A membrane aerated biofilm reactor (MABR), in which O(2) was supplied from the bottom of the biofilm and NH(4)(+) and organic carbon were supplied from the biofilm surface, was operated at different organic carbon loading rates and intra-membrane air pressures to investigate the occurrence of simultaneous chemical oxygen demand (COD) removal, nitrification and denitrification. The spatial distribution of nitrification and denitrification zones in the biofilms was measured with microelectrodes for O(2), NH(4)(+), NO(2)(-), NO(3)(-) and pH. When the MABR was operated at approximately 1.0 g-COD/m(2)/day of COD loading rate, simultaneous COD removal, nitrification and denitrification could be achieved. The COD loading rates and the intra-membrane air pressures applied in this study had no effect on the start-up and the maximum rates of NH(4)(+) oxidation in the MABRs. Microelectrode measurements showed that O(2) was supplied from the bottom of the MABR biofilm and penetrated the whole biofilm. Because the biofilm thickness increased during the operations, an anoxic layer developed in the upper parts of the mature biofilms while an oxic layer was restricted to the deeper parts of the biofilms. The development of the anoxic zones in the biofilms coincided with increase in the denitrification rates. Nitrification occurred in the zones from membrane surface to a point of ca. 60microm. Denitrification mainly occurred just above the nitrification zones. The COD loading rates and the intra-membrane air pressures applied in this study had no effect on location of the nitrification and denitrification zones.     

Microbial fuel cells for simultaneous carbon and nitrogen removal

The recent demonstration of cathodic nitrate reduction in a microbial fuel cell (MFC) creates opportunities for a new technology for nitrogen removal from wastewater. A novel process configuration that achieves both carbon and nitrogen removal using MFC is designed and demonstrated. The process involves feeding the ammonium-containing effluent from the carbon-utilising anode to an external biofilm-based aerobic reactor for nitrification, and then feeding the nitrified liquor to the MFC cathode for nitrate reduction. Removal rates up to 2 kg COD m(-3)NCC d(-1) (chemical oxygen demand: COD, net cathodic compartment: NCC) and 0.41 kg NO(3)(-)-Nm(-3)NCC d(-1) were continuously achieved in the anodic and cathodic compartment, respectively, while the MFC was producing a maximum power output of 34.6+/-1.1 Wm(-3)NCC and a maximum current of 133.3+/-1.0 Am(-3)NCC. In comparison to conventional activated sludge systems, this MFC-based process achieves nitrogen removal with a decreased carbon requirement. A COD/N ratio of approximately 4.5 g COD g(-1) N was achieved, compared to the conventionally required ratio of above 7. We have demonstrated that also nitrite can be used as cathodic electron acceptor. Hence, upon creating a loop concept based on nitrite, a further reduction of the COD/N ratio would be possible. The process is also more energy effective not only due to the energy production coupled with denitrification, but also because of the reduced aeration costs due to minimised aerobic consumption of organic carbon.     

Purification capacity of a highly loaded laboratory scale tidal flow reed bed system with effluent recirculation

The purification capacity of a laboratory scale tidal flow reed bed system with final effluent recirculation at a ratio of 1:1 was investigated in this study. In particular, the four-stage reed bed system was heavily loaded with strong agricultural wastewater. Under the hydraulic and organic loading rates of 0.43 m3/m2.d and 1055 gCOD/m2.d, respectively, the average removal efficiencies obtained for COD, BOD5, SS, NH4-N and P were 77%, 78%, 66%, 62% and 38%, respectively. Even with the high loading rates, approximately 30% of NH4-N was converted into NO2-N and NO3-N from the mid-stage of the system where nitrification took place. The results suggest that the multi-stage reed bed system could be employed to treat strong wastewater under high loading, especially for the substantive mass removal of solids, organic matter and ammoniacal-nitrogen. Tidal flow combined with effluent recirculation is a favourable operation strategy to achieve this objective.     

Continuous biotransformation and removal of nitrophenols under denitrifying conditions

The effect of COD/NO(3)(-)-N ratio on the biotransformation and removal of 2-nitrophenol (2-NP), 4-nitrophenol (4-NP), and 2,4-dinitrophenol (2,4-DNP) was studied in bench scale upflow anaerobic sludge blanket (UASB) reactors. Sodium acetate and sodium nitrate were used as electron donor (substrate) and electron acceptor, respectively. Nitrate nitrogen loading was increased from 0.098 to 0.6 kg/m(3)d in order to keep COD/NO(3)(-)-N ratio as 20.8, 14.3, 9.8, 5.0, 4.0 and 3.33. Throughout the study, input nitrophenolic concentration and hydraulic retention time (HRT) were kept constant as 30 mg/l and 24h, respectively. 2-Aminophenol (2-AP), 4-aminophenol (4-AP) and 2-amino,4-nitrophenol (2-A,4-NP) were found as the major intermediate metabolite of 2-NP, 4-NP and 2,4-DNP, respectively. Removal of all the three nitrophenols increased with lowering of COD/NO(3)(-)-N ratio. However, nitrophenols removal got adversely affected when COD/NO(3)(-)-N ratio was reduced below 5. Maximum removal achieved were 91.63%, 90.17% and 86.10% for 2-NP, 4-NP and 2,4-DNP, respectively at a COD/NO(3)(-)-N ratio of 5. Simultaneous denitrification and methanogenesis was observed in all the reactors throughout the study.     

微电解/组合厌氧好氧/气浮过滤工艺处理糠醛废水

采用微电解/组合厌氧好氧（厌氧反应器、水解酸化、接触氧化）/气浮/过滤工艺处理糠醛废水,验收监测结果表明,COD、BOD5、NH3-N、SS的去除率分别达到99.27%、99.48%、89.22%、54.11%,出水达到《污水综合排放标准》（GB 8978—1996）的二级标准。     

两相厌氧工艺处理高盐纤维素醚废水的研究

采用接种特定污泥的两相厌氧反应器处理高盐纤维素醚废水,重点考察了启动过程及其处理效果。试验结果表明,当产酸相的HRT为18 h时,其所能承受的最大容积负荷为8.18kg/(m3.d),此时其对COD的去除率为20%左右;当产甲烷相的HRT为24 h时,其所能承受的最大容积负荷为5.5 kg/(m3.d),此时其对COD的去除率为35%左右;产甲烷相对COD的去除率与产酸相出水的酸化度呈显著正相关。在产酸相进水COD为6 000 mg/L、产甲烷相进水pH值为7的条件下,当产酸相进水pH值为6、HRT为18 h及产甲烷相的HRT为48 h时,系统的处理效果较佳,出水COD为1 800 mg/L,对COD的总去除率可达70%左右。     

浙江某工业废水处理厂升级改造运行效果解析

浙江某工业废水处理厂升级改造,采用AAO—MBBR复合生物膜工艺,在未新增建设用地和扩建池容的基础上,日处理量由3×10⁴m³/d提高至6×10⁴m³/d。改造后实际运行出水COD、TP、NH₃-N和TN浓度分别为(37.7±6.61)、(0.09±0.03)、(0.25±0.14)和(5.87±1.54)mg/L,出水水质稳定达到一级A标准。实际监测表明,在好氧MBBR区存在TN去除现象,约占TN总去除量的10.36%。系统内的优势硝化菌属为硝化螺旋菌属Nitrospira,其在悬浮载体生物膜和活性污泥中的相对丰度分别为8.98%和0.92%,悬浮载体的投加使硝化细菌得到有效富集;反硝化菌在生物膜中的占比为7.94%,为悬浮载体同步硝化反硝化(SND)效果的发生提供了微观保证,提高了TN去除率。     

Anaerobic treatment of real textile wastewater with a fluidized bed reactor

Anaerobic treatability of a real cotton textile wastewater was investigated in a fluidized bed reactor (FBR) with pumice as the support material. The immobilized biomass or attached volatile solids level on the support material was 0.073 g VSS/g support material at the end of the 128-d start-up period. During the operation period, real cotton textile wastewater was fed to the anaerobic FBR both unsupplemented (in Stages 1 and 2) and supplemented (with synthetic municipal wastewater in Stage 3 and glucose in Stages 4-6). The effect of operational conditions such as organic loading rate (OLR), hydraulic retention time (HRT), influent glucose concentration as the co-substrate, etc. was investigated to achieve the maximum color removal efficiency in the reactor. Results indicated that anaerobic treatment of textile wastewater studied was possible with the supplementation of an external carbon source in the form of glucose (about 2g/l). The corresponding maximum COD, BOD(5) and color removals were found to be around 82%, 94% and 59%, respectively, for HRT of around 24h and OLR of 3 kg COD/m(3)/d. Further increase in external carbon source added to real textile wastewater did not improve the color removal efficiency of the anaerobic FBR reactor.