Characteristics of the bioreactor landfill system using an anaerobic-aerobic process for nitrogen removal

A sequential upflow anaerobic sludge blanket (UASB) and air-lift loop sludge blanket (ALSB) treatment was introduced into leachate recirculation to remove organic matter and ammonia from leachate in a lab-scale bioreactor landfill. The results showed that the sequential anaerobic-aerobic process might remove above 90% of COD and near to 100% of NH4+ -N from leachate under the optimum organic loading rate (OLR). The total COD removal efficiency was over 98% as the OLR increased to 6.8-7.7 g/l d, but the effluent COD concentration increased to 2.9-4.8 g/l in the UASB reactor, which inhibited the activity of nitrifying bacteria in the subsequent ALSB reactor. The NO3- -N concentration in recycled leachate reached 270 mg/l after treatment by the sequential anaerobic-aerobic process, but the landfill reactor could efficiently denitrify the nitrate. After 56 days operation, the leachate TN and NH4+ -N concentrations decreased to less than 200 mg/l in the bioreactor landfill system. The COD concentration was about 200 mg/l with less than 8 mg/l BOD in recycled leachate at the late stage. In addition, it was found that nitrate in recycled leachate had a negative effect on waste decomposition.     

基于好氧反硝化及反硝化聚磷菌强化的低温低碳氮比生活污水生物处理中试研究

【背景】低碳氮比生活污水很难达标处理,多级A/O工艺、生物强化技术及生物膜技术的有机结合可有效解决这一问题。【目的】开发出一种泥膜共生多级A/O工艺并进行中试研究,驯化出高效脱氮除磷菌剂并对系统进行生物强化。【方法】通过测定中试设备出水及污水处理厂出水化学需氧量(Chemical oxygen demand,COD)、氨氮(NH_4~+-N)、硝氮(NO_3~--N)、总氮(Total nitrogen,TN)、总磷(Total phosphorus,TP)对比分析两种工艺的污染物去除效能,利用高通量测序技术对比生物强化技术对系统微生物群落结构的影响。【结果】中试设备对COD、NH_4~+-N、NO_3~--N、TN、TP的去除效果均优于污水处理厂的处理工艺;驯化的低温好氧反硝化菌TN去除率最大值可达84.21%,驯化的低温反硝化聚磷菌群对磷的去除率最高可达85.75%;利用驯化菌群对中试设备进行生物强化后较好地改善了系统NH_4~+-N、NO_3~--N、TN、TP的去除效果;经生物强化后,具有好氧反硝化和反硝化聚磷功能的Pseudomonas菌群明显增多。【结论】泥膜共生多级A/O工艺对于低碳氮比生活污水的处理具有很好的效果,利用生物强化技术可有效提高低温条件下系统污染物去除效能。     

Assessing the feasibility of achieving biological nutrient removal from wastewater at an Irish food processing factory

In Ireland, wastewaters emanating from the food industry typically contain elevated levels of nitrogen and phosphorus before treatment. Two pilot scale studies were performed to determine the feasibility of achieving biological N and P removal on-site at a food ingredients plant. The wastewater treated by the pilot reactors was that which resulted from the day-to-day production in the full-scale food ingredients plant. Both reactors were of the anaerobic/anoxic/oxic (A/A/O) design, however the sizing of the zones was varied in this study. In the first pilot study, while treating a wastewater of the following strength: 1008 mg COD/l; 30.1 mg NH4-N/l and 26.7 mg P/l, removal efficiencies of 93%, 99% and 98% were obtained for COD, NH4-N and P, respectively. In the second study, while operating at reduced hydraulic retention times and lower recycle rates, the pilot plant treated a wastewater of the following strength: 1757 mg COD/l; 62 mg NH4-N/l and 57 mg P/l, with removal efficiencies of 94%, 97% and 75% obtained for COD, NH4-N and P, respectively. This work showed that biological nutrient removal could be successfully applied to treatment of food industry wastewaters.     

固定化微生物处理模拟污染地表水

以聚乙烯醇和海藻酸钠为包埋剂、驯化后的活性污泥为包埋菌剂,制备固定化微生物颗粒,其中包埋剂与包埋菌剂的比例为2:1。将该固定化微生物颗粒按20%的填充率装填到自制反应器中,用于处理模拟污染地表水,研究该固定化微生物的性能特点及其对模拟污染地表水的净化效果。结果表明:固定化微生物反应器的最佳水力停留时间为10h,最佳进水COD负荷为1.15～1.85g·L-1·d-1。在水温为20～29℃、溶解氧为3～4mg·L-1、水力停留时间为10h的条件下,当进水COD浓度为70.58～91.76mg·L-1、铵氮浓度为13.68～17.82mg·L-1时,COD去除率>62.3%,铵氮去除率>90.6%,表明固定化微生物能够有效地去除污染地表水中的COD和铵氮。     

间歇曝气对微污染源水生物接触氧化修复系统脱氮性能的影响

针对寡营养生境下生物脱氮过程碳源不足等问题,开展不同间歇曝气方式对微污染源水生物接触氧化修复系统脱氮性能的影响研究,探究修复系统短程硝化反硝化的可行性与过程机理.结果表明:在停曝-曝气时间为8 h-16 h的间歇曝气方式(Ⅰ)下启动的生物接触氧化修复系统,其铵态氮(NH+4-N)、高锰酸盐指数(CODMn)、总氮(TN)的平均去除率分别稳定在93.0%、78.1%、19.4%;而在停曝-曝气时间为16 h-8 h的间歇曝气方式(Ⅱ)下运行修复系统,其NH+4-N、CODMn平均去除率仍能分别维持在81.2%、76.4%,体系内NO-2-N发生积累,TN去除率增至50%以上.对工况Ⅱ下修复系统周期内氮素转化特性分析发现,在确保出水NH+4-N、溶解氧(DO)浓度达标的前提下,缩短曝气时间可将体系DO长时间控制在0.5～1.5 mg·L-1,亚硝酸氧化菌(NOB)生长及其活性受到抑制,NO-2-N明显累积,最终实现了微污染源水生物接触氧化修复系统的短程生物脱氮.     

Simultaneous nitrification and formaldehyde biodegradation in an activated sludge unit

The simultaneous removal of formaldehyde and ammonium in a lab-scale activated sludge unit was investigated. The unit was operated at a hydraulic retention time of 2.4 days with an ammonium concentration in the influent of 350 mg NH4+-N/L, maintaining the ammonium loading rate at 0.15 g NH4+-N/Ld during the operation time. However, the applied organic loading rate was increased stepwise by increasing the formaldehyde concentration from 26 up to 3168 mg/L, corresponding to 0.01-1.40 g COD/Ld. High formaldehyde removal efficiencies, around 99.5% (+/-0.38), were maintained at all the formaldehyde concentrations. Ammonium removal was also very high during the operation period, around 99.9% (+/-0.01). The ammonium concentration in the effluent was lower than 0.1 mg NH4+-N/L at all applied organic loading rates, indicating that there was no inhibition of nitrification by formaldehyde.     

Evaluation of relative importance of different microbial reactions on organic matter removal in horizontal subsurface-flow constructed wetlands using a 2D simulation model

In this study, we used a two-dimensional (2D) mechanistic mathematical model in order to evaluate the relative contribution of different microbial reactions to organic matter removal (in terms of COD) in horizontal subsurface-flow constructed wetlands that treated urban wastewater. We also used the model to analyse the effect of increasing or decreasing the organic loading rate (changing the hydraulic loading rate (HLR) at a constant influent organic matter concentration, or changing the organic matter concentration at a constant HLR) on both the removal efficiency and the relative importance of the microbial reactions. The model is based on the code RetrasoCodeBright, which we modified to include the main microbial processes related to organic matter and nitrogen transformations in the wetlands: hydrolysis, aerobic respiration, nitrification, denitrification, sulphate reduction and methanogenesis. The model was calibrated and validated with data from two wetlands (each with a surface area of 55 m²) located in a pilot plant near Barcelona (Spain). According to the simulations, anaerobic processes (methanogenesis and sulphate reduction) are more widespread in the wetlands and contribute to a higher COD removal rate (60–70%) than anoxic (denitrification) and aerobic reactions do. These model results are confirmed by experimental observations. In all the cases tested, the reaction that most contributed to COD removal was methanogenesis (33–52%). According to our simulations, decreasing the HLR (for example, from 40 to 25 mm/d) while maintaining a constant COD influent concentration has a clear positive impact on COD removal efficiency (which increases from 65% to 89%). Changing influent COD concentration (for example, from 290 to 190 mg/L) while maintaining a constant HLR has a smaller impact, causing efficiency to increase from 79% to 84%. Changes in influent COD concentration (at a constant HLR) affect the relative contribution of the microbial reactions to organic matter removal. However, this trend is not seen when the HLR changes and the COD influent concentration remains constant.     

Anaerobic digestion of a petrochemical effluent using an anaerobic hybrid digester

Summary An anaerobic hybrid reactor was used in the anaerobic treatment of an acidic petrochemical effluent. An organic loading rate of 20.04 kg COD/(m³d) at a HRT of 17 hours was obtained with a volatile fatty acid removal of 91%, and COD removal of 84%. A final reactor effluent containing 44 mg/l ammonia nitrogen and 12.3 mg/l PO₄-P was produced.     

限氧自养硝化-反硝化生物脱氮新技术

限氧自养硝化—反硝化是部分硝化与厌氧氨氧化相耦联的生物脱氮反应过程,通过严格控制溶解氧在0．1～0．3mg·L^-1,实现硝化反应控制在亚硝酸阶段,然后以硝化阶段剩余的NH4^+作为电子供体,在厌氧条件下实现反硝化,该反应过程是完全的自养硝化—反硝化过程,具有能耗低、脱氮效率高、反应系统占地面积小等优点,适用于处理COD／NH4^+—N低的废水,是一种非常有应用前景的生物脱氮技术,文中详细介绍了限氧自养硝化—反硝化生物脱氮反应过程的研究进展,讨论了其微生物学机理及应用前景。     

para-Chlorophenol inhibition on COD, nitrogen and phosphate removal from synthetic wastewater in a sequencing batch reactor

COD, nitrogen, phosphate and para-chlorophenol (4-chlorophenol, 4-CP) removal from synthetic wastewater was investigated using a four-step sequencing batch reactor (SBR) at different sludge ages and initial para-chlorophenol (4-CP) concentrations. The nutrient removal process consisted of anaerobic, oxic, anoxic and oxic phases with hydraulic residence times (HRT) of 1/3/1/1 h and a settling phase of 0.75 h. A Box-Wilson statistical experiment design was used considering the sludge age (5-25 days) and 4-CP concentration (0-400 mg l(-1)) as independent variables. Variations of percent COD, NH4-N, PO4-P and 4-CP removals with sludge age and initial 4-CP concentration were investigated. Percent nutrient removals increased with increasing sludge age and decreasing 4-CP concentrations. Low nutrient removals were obtained at high initial 4-CP concentrations especially at low sludge ages. However, high sludge ages partially overcome the adverse effects of 4-CP and resulted in high nutrient removals. COD, NH4-N, PO4-P and 4-CP removals were 76%, 72%, 26% and 34% at a sludge age of 25 days and initial 4-CP concentration of 200 mg l(-1). Sludge volume index (SVI) also decreased with increasing sludge age and decreasing 4-CP concentrations. An SVI value of 104 ml g(-1) was obtained at a sludge age of 25 days and initial 4-CP of 200 mg l(-1).     

Improvement in post-treatment of digested swine wastewater

The performance of sequencing batch reactor (SBR) during post-treatment of digested effluent of swine wastewater was investigated. While operating SBR to treat the digested effluent directly, the performance was very poor with COD removal rate about 10%, and NH4+-N removal rate nearly 50%, with a scarce removal of total phosphorus. The performance apparently improved after adding raw swine wastewater or alkali to digested effluent. Although similar results for NH4+-N removal were achieved adopting both measures, the addition of raw wastewater proved superior in removing total nitrogen and total phosphorus. The addition of raw wastewater obtained effluent COD around 300 mg/L which was lower than that after alkali addition i.e. around 550 mg/L. Judged from the investment, oxygen demand, sludge yield, biogas production and running cost, the traditional combined anaerobic-SBR process is unfeasible to treat swine wastewater, while the combined anaerobic-SBR process with addition of raw swine wastewater can be a suitable biotechnology.     

Novel application of oxygen-transferring membranes to improve anaerobic wastewater treatment

Anaerobic biological wastewater treatment has numerous advantages over conventional aerobic processes; anaerobic biotechnologies, however, still have a reputation for low-quality effluents and operational instabilities. In this study, anaerobic bioreactors were augmented with an oxygen-transferring membrane to improve treatment performance. Two anaerobic bioreactors were fed a synthetic high-strength wastewater (chemical oxygen demand, or COD, of 11,000 mg l(-1)) and concurrently operated until biomass concentrations and effluent quality stabilized. Membrane aeration was then initiated in one of these bioreactors, leading to substantially improved COD removal efficiency (> 95%) compared to the unaerated control bioreactor (approximately 65%). The membrane-augmented anaerobic bioreactor required substantially less base addition to maintain circumneutral pH and exhibited 75% lower volatile fatty acid concentrations compared to the unaerated control bioreactor. The membrane-aerated bioreactor, however, failed to improve nitrogenous removal efficiency and produced 80% less biogas than the control bioreactor. A third membrane-augmented anaerobic bioreactor was operated to investigate the impact of start-up procedure on nitrogenous pollutant removal. In this bioreactor, excellent COD (>90%) and nitrogenous (>95%) pollutant removal efficiencies were observed at an intermediate COD concentration (5,500 mg l(-1)). Once the organic content of the influent wastewater was increased to full strength (COD = 11,000 mg l(-1)), however, nitrogenous pollutant removal stopped. This research demonstrates that partial aeration of anaerobic bioreactors using oxygen-transferring membranes is a novel approach to improve treatment performance. Additional research, however, is needed to optimize membrane surface area versus the organic loading rate to achieve the desired effluent quality.     

Preliminary study of a suspended growth predenitrification system

A laboratory study has been conducted to obtained preliminary process information of a suspended growth Predenitrification (SGPDN)system. System performance was evaluated, in terms of chemical oxygen demand (COD) removal, NH(3)-N removal, system biomass yield and inventory, and effluent qualities, at different solids retention times (SRTs) and recycle ratios. Chemical oxygen demand removal in an SGPDN system occurs mainly in the anoxic reactor, which accounts for 94% of total COD removal. The overall COD removal rate is independent of recycle ratio (ranging from 2-5) used in this study; however, effluent COD increase with increasing recycle ratio. The observed anoxic and aerobic COD removal rates decrease with increasing SRT. The NH(3)-N removal in an SGPDN system is induced by two mechanisms: assimilatory NH(3)-N requirement for biomass production in the anoxic reactor and nitrification in the aerobic reactor. The observed anoxic NH(3)-N removal rate relates directly to the anoxic COD removal rate and agrees fairly well with the assimilatory NH(3)-N requirement theoretically predicted. The overall NH(3)-N removal rate is independent of SRTs and recycle ratios used in this study. Biomass yield in an SGPDN system occurs mainly in the anoxic reactor. However, uniform distribution of biomass throughout the entire system is obtained because of the high recycle rate used. The observed biomass yield (Y(O)) decreases with increasing STR. Tertiary treatment efficiency can be achieved in an SGPDN system. More than 90% reduction in feed COD., feed NH(3)-N, and NO(2) + NO(3)-N is obtained at all SRTs and recycle ratios used in this study. Higher MLVSS loading rates can be applied to a final clarifier without impairing its separation efficiency because of the excellent settleability of the Predenitrification activated sludge.     

Effects of monocot and dicot types and species richness in mesocosm constructed wetlands on removal of pollutants from wastewater

The effects of planting type and species richness on removal of BOD5, COD, nitrogen and phosphorus were studied in mesocosms with monocot alone (M), dicot alone (D) and mixed planting of M+D, where each planting type had four species richness levels. Above- and below-ground plant biomasses increased with the M and M+D species richness as shown by one-way ANOVA. The M+D type had the highest above-ground biomass, whereas the M type had the highest below-ground biomass among planting types. Carbon, nitrogen and phosphorus in the microbial biomass increased with the richness of the M and M+D type. Removals of BOD5, COD, inorganic P and total P did not change with the richness, but removals of NH4-N, NO3-N increased. Planting type impacted only removal of inorganic P, with higher removal of inorganic P in the M type.     

石灰石滤柱出水回流曝气生物滤池系统的处理效能及微生物群落多样性

[背景]曝气生物滤池(Biological Aerated Filter,BAF)对有机物和氨氮的处理效果较好,但除磷效果不佳.[目的]提高BAF系统的除磷效能.[方法]在缺氧/好氧滤柱后设置了部分采用石灰石滤料的滤柱(未添加石灰石滤料的系统作为对照组),对比分析了使用石灰石滤柱出水回流BAF系统的处理效能,通过最大或...     

The effect of an anoxic zone on biological phosphorus removal by a sequential batch reactor

Nitrate can affect phosphate release and lead to reduced efficiency of biological phosphorus removal process. The inhibition effect of remaining nitrate at the anaerobic/anoxic phases was investigated in a lab scale sequencing batch reactor. In this study the influence of denitrification process on reactor performance and phosphorus removal was examined. The experiments were carried out through simultaneous filling and decanting, mixing, mixing-aeration and settling modes. Glucose and acetate were used as carbon sources. The proposed treatment system was capable of removing approximately 80% of the influent PO4-P, 98% NH4-N and 97% COD at a SRT of 25 days. In the fill/decant phase, anoxic and anaerobic conditions prevailed and a large quantity of nitrate was removed in this stage. In the anoxic phase the remaining nitrate concentration was quickly reduced and a considerable amount of phosphate was released. This was attributed to the availability of acetate in this stage. For effective nitrogen and phosphate removal, a short anoxic phase was beneficial before an aerobic phase.     

In situ simultaneous organics and nitrogen removal from recycled landfill leachate using an anaerobic-aerobic process

An anaerobic-aerobic process including a fresh refuse landfill reactor as denitrifying reactor, a well-decomposed refuse reactor as methanogenesis reactor and an aerobic activated sludge reactor as nitrifying reactor was operated by leachate recirculation to remove organic and nitrogen simultaneously. The results indicated that denitrification and methanogenesis were carried out successfully in the fresh refuse and well-decomposed landfill reactors, respectively, while the nitrification of NH(4)(+)-N was performed in the aerobic reactor. The maximum organic removal rate was 1.78 kg COD/m(3)d in the well-decomposed refuse landfill reactor while the NH(4)(+)-N removal rate was 0.18 kg NH(4)(+)-N/m(3)d in the aerobic reactor. The biogas from fresh refuse reactors and well-decomposed refuse landfill reactors were consisted of mainly carbon dioxide and methane, respectively. The volume fraction of N(2) increased with the increase of NO(3)(-)-N concentration and decreased with the drop of NO(3)(-)-N concentration. The denitrifying bacteria mustered mainly in middle layer and the denitrifying bacteria population had a good correlation with NO(3)(-)-N concentration.     

Specific biogas production and role of packing medium in the treatment of rubber thread manufacturing industry wastewater

Wastewater from three rubber thread manufacturing industries collected from three different sampling points was characterised. The acidic wastewater (pH = 3.6 to 4.7) contains high levels of COD, BOD, nitrogen and zinc. The average COD:N:P ratio was 100:3.8:0.4 whereas the BOD:N:P ratio was 100:4.5:0.4 with more than sufficient amounts of N and P for anaerobic digestion using the up-flow anaerobic filter. The specific biogas yield ranged between 0.250 to 0.069 l CH₄/g COD added when the organic loading rate was altered from 2.0 to 14.0 g COD/l/d respectively. The biogas production rate and the biogas yield rate increased from 8.2 to 42.7 l/d and 0.97 to 1.50 l CH₄/l/d respectively, for the same organic loading rate. The N and P utilised ranged between 1.53 to 1.20 and 0.3 to 0.26 mg per 100 mg COD consumed respectively when the organic loading rate was increased from 2.0 to 14.0 g COD/l/d. The optimum COD:N:P ratio obtained for steady state operation of the up-flow anaerobic filter in this study for the rubber thread manufacturing wastewater was 100:1.3:0.3. Attached biomass was responsible for the removal of more than 70% of the COD in the wastewater when PU foam was used as the packing media.     

Effect of carbon source on biological nutrient removal in a sequencing batch reactor

Sequencing batch operation was used for nutrient (COD, NH4-N, NO3-N, PO4-P) removal from synthetic wastewater by using different carbon sources. Operation consisted of anaerobic, anoxic, oxic, anoxic and oxic (An/Ax/Ox/Ax/Ox) phases with durations of 2/1/4.5/1.5/1.5 h. Glucose, acetate and a mixture of glucose/acetate were used as carbon source to yield a COD/N/P ratio of 100/5/1.5 in the feed. Sludge age was kept constant at 10 days. COD, NH4-N, NO3-N and PO4-P removal efficiencies were maximum at the levels of 96%, 87%, 81% and 90% respectively, when a mixture (50/50) of glucose and acetate was used.     

Comparison of long-term performances and final microbial compositions of anaerobic reactors treating landfill leachate

Laboratory scale anaerobic upflow filter, sludge blanket and hybrid bed reactors were operated for 860 days in the treatment of high ammonia landfill leachate. Organic loading was gradually increased from 1.3 to 23.5 kg COD/m3 day in the start-up period and then fluctuated according to the COD concentration of raw leachate. To prevent free ammonia inhibition, influent pH was reduced to 4.5 after Day 181 and consequently COD removal efficiencies above 80% were achieved in all reactors. However, the anaerobic filter and hybrid bed reactor were generally found slightly more efficient and stable than the UASB reactor. In addition to conventional anaerobic reactor control parameters, the complementary techniques of denaturing gradient gel electrophoresis (DGGE), cloning and fluorescent in situ hybridization (FISH) were used to identify and compare the microbial profiles in the reactors at Day 830. Molecular analyses revealed that acetoclastic Methanosaeta species were prevalent in all reactors and configuration did not have an impact on microbial diversity in the long-term.