In situ nitrogen management in controlled bioreactor landfills

The characteristics of leachate from landfills vary according to site-specific conditions. Leachates from “old” landfills are often rich in ammonia nitrogen due to the hydrolysis and fermentation of the nitrogenous fractions of biodegradable substrates, with decreases in concentration mainly attributable to leachate washout. At landfills where leachate containment, collection and recirculation is practiced to accelerate decomposition of readily biodegradable organic constituents, leachate ammonia nitrogen concentrations may accumulate to higher levels than during conventional single pass leaching, thereby creating an ultimate leachate discharge challenge. Landfill leachate treatment options include complex and often costly sequences of external physical–chemical and biological processes for removal of high-strength organics and inorganics, including nitrogen. Therefore, this paper focuses on investigations with bioreactor landfill simulations to demonstrate the potential for in situ nitrogen removal in dedicated nitrification/denitrification zones. Using leachate recirculation, associated system modifications provided separate aerobic and anoxic zones for ammonia nitrogen transformations to nitrate and nitrogen gas, respectively. Results from the three simulated optional stages of methanogenesis, nitrification and denitrification indicated that nitrogen conversion and removal was dependent on the operational stage. Both separate and combined reactor operation with internal leachate recycle provided 95% nitrogen conversion. In contrast, combined reactor operation with single pass leaching provided a conversion efficiency per cycle ranging between 30–52% for nitrification and 16–25% for denitrification, thereby indicating the efficacy of using the landfill itself for attenuation of leachate ammonia nitrogen concentrations to levels acceptable for ultimate discharge.     

准好氧填埋场氮素形态变化及转化特性研究

通过实验室填埋柱模拟实验,考察了准好氧生物反应器填埋场稳定化过程中氮素的形态变化和转化特性.根据渗滤液水质及N2O气体浓度变化特性,将垃圾降解过程分为4个阶段,即初期(2~50d)、中期(52~138d)、后期(140~214d)和末期(216~262d).研究了渗滤液中NH+4-N、TKN、TN、有机氮(Org-N)、NO-2-N、NO-3-N及气体N2O在垃圾降解过程中的变化规律,并依据氮素的变化规律探讨了这4个阶段中氮素的转化途径.结果表明:初期氮的转化途径主要是氨化作用和反硝化作用;中期主要是氨化作用和同时硝化反硝化作用;后期和末期硝化作用强于反硝化作用.     

Simultaneous organic and nitrogen removal from municipal landfill leachate using an anaerobic-aerobic system

An anaerobic-aerobic system including simultaneous methanogenesis and denitrification was introduced to treat organic and nitrogen compounds in immature leachate from a landfill site. Denitrification and methanogenesis were successfully carried out in the anaerobic reactor while the organic removal and nitrification of NH4+,-N were carried out in the aerobic reactor when rich organic substrate was supplied with appropriate hydraulic retention time. The maximum organic removal rate was 15.2 kg COD/m3 d in the anaerobic reactor while the maximum NH4+-N removal rate and maximum nitrification rate were 0.84kg NH4+-N/m3/d and 0.50kg NO3--N/m3/d, respectively, in the aerobic reactor. The pH range for proper nitrification was 6-8.8 in the aerobic reactor. The organic compounds inhibited nitrification so that the organic removal in the anaerobic reactor could enhance the nitrification rate in the following aerobic reactor. The gas production rate was 0.33 m3/kg COD and the biogas compositions of CH4, CO2, and N2 were kept relatively constant, 66-75, 22-32, and 2-3%, respectively.     

Removal of ammoniacal nitrogen from landfill leachate by irrigation onto vegetated treatment planes.

Leachate is a contaminated liquor resulting from the disposal of solid and liquid wastes at landfill sites that must be treated before discharge. Vegetated leachate treatment planes have been used at landfill sites in the UK but have received little scientific attention. This paper describes studies of model leachate treatment planes with a focus on the removal of ammoniacal nitrogen (NH3-N). Small-scale and field-scale experimental treatment planes were constructed. filled with clay loam soil and vegetated with grass (Agrostis stolonifera). Landfill leachate was applied at hydraulic loading rates ranging from 17-217l/m2/d. An exponential relationship was used to characterise the pattern of NH3-N removal. No relationship was observed between the hydraulic loading rate and the NH3-N removal rate constants (R2 = 0.0039). The daily specific NH3-N mass removal rate was found to be linearly related to the NH3-N concentration at the start of that day of treatment (R2 = 0.35). Possible causes of variation in the rate of NH3-N removal between experiments are discussed. A simple inorganic nitrogen balance indicated that the mass of N-H3-N and NO2-N removed was not accounted for by NO3-N production. Explanations for this apparent nitrogen deficit are discussed.     

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.     

好氧反硝化在短程硝化反硝化工艺中的作用研究

采用SBR反应器处理垃圾渗滤液，研究了短程硝化反硝化过程中好氧反硝化的作用。结果表明，SBR反应器的亚硝化效果良好，氨氮几乎完全被氧化为NO2^- -N；该系统的活性污泥中同时存在能还原NO3^- -N和NO2^- -N的好氧反硝化菌，还原NO3^- -N的好氧反硝化菌和氨氧化菌的数量及其总活性高于NO2^- -N氧化菌，这是SBR反应器能够长期维持亚硝化状态的重要原因；有机物浓度越高则好氧反硝化速率越快，此时氨氮均被氧化为NO2^- -N，当有机物浓度达到某临界值时，好氧反硝化速率几乎保持不变；溶解氧浓度越低则好氧反硝化速率越快，释放出的OH^-会导致pH值升高。好氧反硝化对于维持和促进SBR反应器的短程硝化反硝化具有重要的作用。     

UASB/吹脱塔/SBR/纳滤工艺处理生活垃圾渗滤液

采用UASB/吹脱塔/SBR/纳滤工艺处理垃圾渗滤液,处理规模为800m3/d,垃圾渗滤液COD为8 000～12 000mg/L、BOD5为3000～5 500mg/L、SS为500～800mg/L、NH3-N为1 000～2 000 mg/L,出水COD≤l00mg/L、BOD5≤30 mg/L、SS≤30 mg/L、NH3-N≤25 mg/L,达到国家新建<生活垃圾填埋场污染控制标准>(GB 16889-2008).运行结果表明,该工艺运行稳定,处理效果好.     

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.     

Nitrogen loss and oxygen paradox in full-scale biofiltration for drinking water treatment

The nitrogen loss and DO paradox in full-scale biofiltration for drinking water treatment and the possible pathway responsible for them were investigated. A highly contaminated source water was treated at Pinghu Surface Water Plant using four biofilters, which resulted in a steady removal of NH(4)(+)-N (2.67mg/L), a great DO consumption (8.86 mg/L) and an increase in the concentration of NO(3)(-)-N (1.77mg/L). The nitrogen and DO balances indicated that about 13 NH(4)(+)-N was lost and the actual DO consumption was about 30% lower than the theoretical DO demand if nitrification was regarded as the only pathway to remove NH(4)(+)-N. The analysis of correlation coefficients analysis between several factors and the nitrogen loss suggested that "Aerobic deammonification", the coupling of shortcut nitrification and the anaerobic ammonia oxidation (Anammox) in an aerobic environment, might be the most probable pathways to explain the occurrence of these phenomena. According to this mechanism, about 57% NH(4)(+)-N was removed through complete nitrification and about 21.5% NH(4)(+)-N was incompletely nitrified into NO(2)(-)-N. The latter then involved in Anammox as the electron acceptor with the remaining NH(4)(+)-N as the electron donor. Since the Anammox reaction is anaerobic, the nitrogen loss and DO paradox can be justified.     

Treatment of landfill leachate by combined aged-refuse bioreactor and electro-oxidation

Two-stage aged-refuse bioreactor (ARB) was applied to treat landfill leachate in Shanghai Waste Laogang Disposal Plant. The removal efficiencies of chemical oxygen demand (COD), biological oxygen demand (BOD), total organic carbon (TOC), total nitrogen (TN) and ammonia nitrogen (NH(3)-N) of landfill leachate treated by the two-stage bioreactor system were 98.5%, 99.9%, 98.0%, 64.2% and 99.9%, respectively. The COD and BOD in the second stage effluent were 239 and 7 mg l(-1), respectively. Thus three types of electrolysis were employed to further treat the second effluent, undivided electrolysis (UDE), divided electrolysis (DE) with Ti/PbO(2) cathode and DE with gas diffusion cathode. All electrolysis processes possessed good color removal effect, while the DE with gas diffusion cathode had the best TOC removal effect. The optimum electrolysis time of leachate was 30 min. The TOC removal efficiencies were 51.4% and 39.7% in anolyte and catholyte, respectively, after 30 min electrolysis at 5 V. In addition, the DE with gas diffusion cathode showed the least energy consumption of 9.8 k Whm(-3) at 30 min. The organic pollutants in the leachate were analyzed through a gas chromatography coupled with mass spectrometry (GC-MS) system. Through the two-stage ARB, the species and concentrations of organic pollutants in landfill leachate reduced greatly. Several chlorinated organic compounds were detected in the effluent after the UDE and the anolyte of the DE. In addition, the concentration of absorbable organic halogens (AOX) increased greatly during the electrolysis. Hence, careful consideration should be given in the application of electro-oxidation into the treatment of chloride-containing wastewater.     

Effect of salinity and inorganic nitrogen concentrations on nitrification and denitrification rates in intertidal sediments and rocky biofilms of the Douro River estuary, Portugal

The regulatory effects of salinity and inorganic nitrogen compounds on nitrification and denitrification were studied in intertidal sandy sediments and rocky biofilms in the Douro River estuary, Portugal, over a 12-month period. Nitrification and denitrification rates were measured in slurries of field samples and enrichment experiments using the difluoromethane and the acetylene inhibition techniques, respectively. Salinity did not regulate denitrification in either environment, suggesting that halotolerant bacteria dominated the denitrifier communities. However, nitrification rates were stimulated when salinity increased from 0 to 15 practical salinity units. NO3- addition experiments revealed that NO3- availability stimulates denitrification rates in sandy sediments, but not in rocky biofilms; however, in rocky biofilms a positive and linear relationship was observed between denitrification rates and water column NO3- concentrations (r=0.92) during the monthly surveys. The N2O:N2 ratios increased rapidly when NO3- increased from 63 to 363 microM; however, results from monthly surveys showed that environmental parameters other than NO3- availability may be important in controlling the variation in N2O production via denitrification. Ammonium additions to sandy sediments stimulated nitrification rates by 35% for the 20 microM NH4+ addition, but NH4+ appeared to inhibit nitrification at high concentration addition (200 microM NH4+). In contrast, rocky biofilm nitrification was stimulated by 65% when 200 microM NH4+ was added.     

Inter-relationships between nitrogen balance, pH and dissolved oxygen in an oxidation ditch treating farm animal waste

The pathways of N in aerobic farm waste treatment systems are discussed in relation to the dissolved oxygen (DO) and pH of the mixed liquor. The change in pH, DO, oxygen uptake rate and nitrogen balance were monitored under steady, and non-steady, state conditions in an oxidation ditch treating undiluted pig waste. A kinetic analysis of the mass balance for nitrogen allowed an interpretation of the fate of nitrogen under different prevailing conditions. Undesirable accumulations of nitrite were noted in the presence of high levels of free NH₃ and HNO₂. The process was self-promoting and was encouraged by the influx of raw waste. Concentrations of 500 mg 1⁻¹ NO₂-N and 1200 mg 1⁻¹ NO₃-N were the maximum values observed and were considered to be the concentrations at which product inhibition arrested nitrifying activity. Attainment of these levels prevented complete nitrification despite an adequate retention time. pH and DO were inversely related probably through nitrification, but pH appeared to be lowered by accumulation of nitrite and nitrate anions, and thus by the balance between nitrification and denitrification. Considerable N loss through denitrification was found to occur despite apparently aerobic mixed liquors. At low DO simultaneous nitrification-denitrification could eliminate 90 per cent of the soluble-N. NH₃ desorption in laboratory cultures was found to be first order in free NH₃ but was not a significant mode of N loss under field conditions.     

利用畜禽废水中的氨氮驯化矿化垃圾填料氧化填埋场的CH4

探讨通过利用畜禽废水中氨氮实现矿化垃圾中铵氧化菌的富集,再利用其对CH4同等氧化能力实现垃圾填埋场温室气体总量减排。研究结果表明：矿化垃圾对畜禽污水中氨氮具备较强的硝化能力,运行120 d内氨氮去除率高于60%;投加200 mg·kg -1氨氮后的培养研究中,120 h驯化后矿化垃圾硝酸盐氮的生成量分别为原生矿化垃圾样品和粘土样品的2.0倍和3.8倍;矿化垃圾和粘土样品中CH4消耗和CO2的净生成趋势可分别采用一级和零级动力学模型来表征(R 2>0.68);与氮转化趋势类似,基于CO2的净生成速率,120 d驯化后矿化垃圾的CH4氧化能力比粘土样和原生矿化垃圾分别提高了59.3%和10.6%。矿化垃圾经高氨氮畜禽养殖废水驯化可有望提高其对CH4的氧化能力,而污水中其他组分(CODCr、SS及磷素等)富集对CH4氧化过程的影响还亟待进一步研究。     

Simultaneous removal of phenol and ammonia by an activated sludge process with cross-flow filtration

Attempts were made for removing ammonia from synthetic wastewater under the presence of phenol, which is inhibitory to nitrification, by using a single-stage activated sludge process with cross-flow filtration. Activated sludge biomass which had been acclimated with phenol for over 15 years was used for the inoculum, and synthetic wastewater was continuously supplied to the process retaining biomass at 8000 mg VSS l(-1). Phenol was completely removed, and ammonia was simultaneously nitrified to nitrate; nitrification rate reached 200 mg N l(-1) d(-1) when phenol was removed at a rate up to 300 mg l(-1) d(-1). It was observed that 0-13% of the ammonia was removed via denitrification. Intermittent aeration enhanced the denitrification rate to 160 mg N l(-1) d(-1) by utilizing phenol. and approximately 24% of the denitrified nitrogen was recovered as nitrous oxide. Methanol, which is the most commonly used electron donor in conventional nitrogen removal processes, did not enhance the denitrification rate of the phenol-acclimated activated sludge used in this study, however phenol did. The results suggest that this process potentially works as a space- and energy-saving nitrogen removal process by utilizing substances inhibitory to nitrifiers as electron donors for denitrification.     

A/O短程硝化反应器处理高浓氨氮废水的SND

以垃圾渗滤液的UASB处理出水为研究对象,考察了A/O短程硝化反应器的同步硝化反硝化(SND)效果.当DO为2～5 mg/L时,SND对TN的去除率为5%-30%,去除的TN大致等于硝化过程中减少的TKN与产生的NOx--N的差值.C/N是影响SND去除总氮的决定性因素,随着C/N的提高,对TN的去除率增加.在进水C/N相同的情况下,短程硝化提高了SND对TN的去除率.活性污泥密实的结构和好氧颗粒污泥的存在,可能是发生SND现象的重要原因.     

准好氧生物反应器处理渗滤液系统的驯化研究

将准好氧填埋技术与矿化垃圾技术相结合在实验室内构建了模拟准好氧生物反应器垃圾处理系统,以室内埋龄为3年的矿化垃圾填充准好氧生物反应器,以室内模拟垃圾填埋柱产生的新鲜渗滤液为处理对象,考察了混合培养法、容积负荷渐增法和水力负荷渐增法对反应器内微生物的驯化效果.结果表明,混合培养法较负荷渐增法的驯化效果好,在驯化结束时,采用混合培养法的反应器出水COD为305 mg/L,NH3-N为0.6 mg/L,TN为38.7 mg/L;驯化时间越长则驯化效果越好,同是容积负荷渐增法,经过30 d分阶段驯化和经过20 d分阶段驯化的反应器,其出水COD分别为381 mg/L和1 311 mg/L,NH3-N分别为0.8 mg/L和5.0 mg/L.在准好氧生物反应器处理渗滤液系统的工程应用中,对微生物的驯化可首选混合培养法,同时应保证一定的驯化时间.     

地埋式一体化生物滤池工艺处理农村生活污水

采用地埋式一体化生物滤池工艺处理农村生活污水。该工艺通过设置前置缺氧池进行反硝化脱氮,通过拔风和溅水来强化充氧效果,实现了碳氧化及硝化。中试结果表明,该工艺对COD的平均去除率达63．1％,对NH4^＋ -N的去除率为92．2％,对TN的去除率为68．6％,对TP的去除率为47．5％,出水水质达到了《城镇污水处理厂污染物排放标准》（GB18918-2002）的一级标准。该工艺具有节能、高效和简易的特点,适于在居住分散的农村地区推广。     

MBR在蓬莱市生活垃圾渗滤液处理工程中的应用

结合蓬莱市生活垃圾处理场工程实例,介绍了MBR工艺处理垃圾渗滤液的工艺流程、原理等,分析了MBR工艺处理垃圾渗滤液的特点和优势。垃圾渗滤液经过MBR工艺处理,生化部分采用硝化/反硝化工艺,再经超滤/纳滤工艺等膜分离技术和其他方法处理,最终流出液水质可以达到《生活垃圾填埋场污染控制标准》(GB 16889—2008)。     

垃圾填埋场渗沥液水位壅高及工程控制

 我国垃圾填埋场渗沥液水位普遍壅高,严重影响安全运行。测试和总结垃圾的持水特性、饱和渗透系数以及渗沥液导排层渗透和淤堵特性。通过数值分析,揭示垃圾初始含水率、持水特性以及垃圾和导排层渗透系数对填埋场水位的影响规律。结果表明,垃圾饱和渗透系数随深度和龄期减小、导排层淤堵、垃圾初始含水率高导致水位明显壅高;而垃圾饱和渗透系数较小时,堆体内易形成局部滞水。结合实际工程,验证数值模拟结果,提出并实施水位壅高控制的工程措施,效果十分显著。