Nitrogen removal from wastewater with a low COD/N ratio at a low oxygen concentration

The goal of the study was to determine the effectiveness of nitrification and denitrification and the kinetics of ammonia removal from a mixture of wastewater and anaerobic sludge digester supernatant in an SBR at limited oxygen concentration. In addition, the COD removal efficiency and sludge production were assessed.In the SBR cycle alternating aerobic and anaerobic phases occurred; in the aeration phase the dissolved oxygen (DO) concentration was below 0.7 mg O₂/L. The low DO concentration did not inhibit ammonia oxidation-nitrification and the efficiency was ca. 96-98%. However, a relatively high COD concentration in the effluent was detected. The values of K_m and V_max, calculated from the Michaelis-Menten equation, were 43 mg N-NH₄/L and 15.64 mg N-NH₄/L h, respectively. Activated sludge production was almost stable (0.62-0.66 g MLVSS/g COD). A high net biomass production resulted from a low specific biomass decay rate of 0.0015 d⁻¹.     

Impact of COD/N ratio on nitrous oxide emission from microcosm wetlands and their performance in removing nitrogen from wastewater

Constructed wetlands (CWs) are considered to be important sources of nitrous oxide (N₂O). In order to investigate the effect of influent COD/N ratio on N₂O emission and control excess emission from nitrogen removal, free water surface microcosm wetlands were used and fed with different influent. In addition, the transformation of nitrogen was examined for better understanding of the mechanism of N₂O production under different operating COD/N ratios. It was found that N₂O emission and the performance of microcosm wetlands were significantly affected by COD/N ratio of wastewater influent. Strong relationships exist between N₂O production rate and nitrite (r = 0.421, p < 0.01). During denitrification process, DO concentration crucially influences N₂O production rate. An optimal influent COD/N ratio was obtained by adjusting external carbon sources for most effective N₂O emission control and best performance of the CWs in nitrogen removal from wastewater. It is concluded that under the operating condition of COD/N ratio = 5, total N₂O emission is minimum and the microcosm wetland is most effective in wastewater nitrogen removal.     

进水碳氮比对CANON型人工湿地脱氮性能的影响

通过逐步提高进水中的有机碳源浓度,探讨进水碳氮比(C/N)对基于亚硝化的全程自养脱氮(CANON)型潮汐流人工湿地(TFCW)脱氮效能及其微生物特性的影响.结果表明: 进水C/N可显著影响CANON型TFCW中脱氮功能微生物的数量与活性,进而影响其氮素转化速率.当进水C/N由0.0增至6.0时,TFCW中反硝化功能基因的丰度随之增加,系统反硝化性能提高,TFCW中逐渐形成同步亚硝化、厌氧氨氧化与反硝化(SNAD)耦合反应体系,其脱氮效果得以强化.当进水C/N＞6.0时,好氧氨氧化菌活性受到抑制,数量逐渐减少,TFCW中的厌氧氨氧化作用与反硝化作用受阻,系统脱氮性能恶化.当进水C/N为6.0时,TFCW中的SNAD作用可得到最大限度的强化,其总氮(TN)去除率和去除负荷分别达(93.3±2.3)%和(149.30±8.00) mg·L^-1·d^-1,高于CANON系统中TN去除率的理论值.     

Effects of influent DO/COD ratio on the performance of an anaerobic fluidized bed reactor fed low-strength synthetic wastewater

The effect of influent DO/COD (dissolved oxygen/chemical oxygen demand) ratio on the performance of an anaerobic fluidized bed reactor (AFBR) containing GAC was studied. A high influent DO concentration was found to have adverse impacts on organic removal efficiency, methane production, and effluent suspended solids (SS) concentration. These problems resulted with a DO/COD ratio of 0.12, but not at a lower ratio of 0.05. At first organic removal appeared satisfactory at the higher DO/COD ratio at a hydraulic retention time of 0.30 h, but soon a rapid growth of oxygen-consuming zoogloeal-like organisms resulted, eventually causing high effluent SS concentrations. The influent DO also had an inhibitory effect, resulting in a long recovery time for adequate methanogenic activity to return after influent DO removal began. With the growing interest in anaerobic treatment of low COD wastewaters, the increased possibility of similar adverse DO effects occurring needs consideration.     

普通小球藻对养殖污水脱氮除磷的效果研究

随着我国养殖业的不断发展,养殖污水排放量的日益增加,养殖污水的高氮、磷含量导致水体富营养化问题日趋严重。小球藻是光能自养生物,能有效同化氮、磷,使污水中的氮、磷减少。本研究通过在实验室模拟不同氮、磷含量的养殖污水环境,分析小球藻对氮、磷的去除效果;在此基础上,用小球藻处理某养殖场污水;并联合膨润土与小球藻,探究两者脱氮除磷的协同作用能力及膨润土对小球藻细胞沉降的效果。结果表明,小球藻对模拟污水的氨氮去除率可达80%,对磷酸根的最高去除率接近100%;对养殖污水中的氮、磷也有一定的去除效果;但养殖污水成分复杂,小球藻的生长被抑制。膨润土与小球藻的结合,能够提高污水中的氮磷去除率并帮助藻细胞快速沉降,为污水处理后藻细胞的收集处理提供了有效方法。     

Integration of a Coagulation/Flocculation step in a biological sequencing batch reactor for COD and nitrogen removal of supernatant of anaerobically digested piggery wastewater

The supernatant from mesophilic anaerobic digestion of piggery wastewater is characterised by a high amount of COD (4.1 g COD L(-1)), ammonium (2.3g NH(4)(+)-NL(-1)) and suspended solids (2.5 g SS L(-1)). This effluent can be efficiently treated by means of a Sequencing Batch Reactor (SBR) strategy for biological COD, SS and nitrogen removal including a Coagulation/Flocculation step. Total COD and SS reduction yields higher than 66% and 74%, respectively, and a total nitrogen removal (via nitrite) of more than 98% were reached when working with HRT 2.7 days, SRT 12 days, temperature 32 degrees C, three aerobic/anoxic periods, without external control of pH and under limited aeration flow. The inhibition of nitrite oxidizing biomass was achieved by the working free ammonia concentration and the restricted air supply (dissolved oxygen concentration below 1 mg O(2)L(-1)). Since a part of the total COD was colloidal and/or refractory, a Coagulation/Flocculation step was implemented inside the SBR operating strategy to meet a suitable effluent quality to be discharged. Several Jar-Tests demonstrated that the optimal concentration of FeCl(3) was 800 mg L(-1). A respirometric assay showed that this coagulant dosage did not affect the biological activity of nitrifying/denitrifying biomass.     

Simultaneous removal of carbon and nitrogen from municipal-type synthetic wastewater using net-like rotating biological contactor (NRBC)

The treatment of municipal-type synthetic wastewater was carried out using a three stages net-like rotating biological contactor (NRBC). The results indicated that, compared with conventional rotating biological contactor (RBC), NRBC have several advantages, such as quick start-up, high biomass concentration and can handle high organic loading rates. The COD and total nitrogen removal rates achieved were 78.8–89.7% and 40.2–61.4%, respectively, in aerobic treatment of low COD municipal-type wastewater at hydraulic retention times (HRT) from 5 to 9 h. The COD removal rate achieved 80–95% when organic loading varied between 16 and 40 gCOD/m² d. A large amount of nematodes were found in the NRBC system, which made the NRBC system produce relatively low amounts of waste sludge, due to their grazing.     

Effects of different carbon supplements on phosphorus removal in low C/P ratio industrial wastewater

This study focuses on the effects of different carbon supplements on biological phosphorus removal in the optonics and semiconductor industrial wastewater treatment. Experimental results demonstrate that the addition of a carbon source (glucose, acetate, and digester supernatant) improved phosphorus removal effectively. When the COD/P ratios were controlled in the range of 18-20 (using glucose and supernatant as supplement), the acclimated sludge showed more than 98% removal of phosphorus. In addition, different organic carbons induce dissimilar behavior in anaerobic release and aerobic uptake of phosphorus. The glucose supplement induces significant phosphorus release in anaerobic phase and then an increased phosphorus uptake in aerobic phase. The released phosphorus descended in anaerobic phase when acetate and supernatant were added. There was a good linear relationship of first order reaction between initial COD concentration and specific substrate utilization rate in anaerobic phase.     

污水地下渗滤系统脱氮效果及动力学过程

建立了模拟污水地下渗滤过程的中试系统,重点考察了水力负荷对系统脱氮效率的影响情况,建立了描述地下渗滤系统微生物脱氮过程的动力学模型.结果表明:地下渗滤系统脱氮效果好,抗水力负荷冲击能力强,处理最佳水力负荷0.125m3· m-2· d-1,出水中氮浓度低于《城市污水再生利用——景观环境用水水质》标准( GB/T 18921-2002).地下渗滤系统硝化过程符合一级动力学模型NE=Noe-0.4812t,温度是影响硝化速率的主要因素,两者的关系是KT=0.2218×1.035(T-20);出水硝态氮浓度与水力停留时间之间呈负指数关系,可描述为C=16.3475e-0.2548t,碳源是引起反硝化速率变化的主要因子.在基质层垂直深度65 cm处二次补加生活污水,反硝化速率常数由0.0355提高到0.0488.强调地下渗滤系统的污水净化功能而忽视其生态服务功能,是系统运行中普遍存在的认识误区,过高的水力负荷不利于硝化-反硝化反应的顺利进行.地下渗滤系统运行应采取适宜的水力负荷方式,促进硝化-反硝化作用.     

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。     

Effect of ferrous sulphate on nitrification during simultaneous phosphorus removal from domestic wastewater using a laboratory scale anoxic/oxic reactor

In the present study a laboratory scale anoxic/oxic reactor was used to remove the important eutrophication nutrients such as phosphorus and nitrogen from synthetic domestic wastewater. Phosphorus was removed through simultaneous precipitation and was carried out using the coagulant ferrous sulphate FeSO₄ · 7H₂O. Total phosphorus in the effluent was controlled to below 1 mg/l using a ferrous to phosphorus molar ratio of 2.1. pH after the addition of coagulant plays a major role in determining the molar ratio of the precipitant. Nitrogen was removed biologically in the anoxic/oxic system and the effect of simultaneous precipitation on nitrification and denitrification was investigated. The nitrification rate of the system remained unaffected during simultaneous precipitation and varied from 0.046 to 0.059 g N–NH₄ ⁺/g VSS/day. Denitrification was complete and was not affected by the coagulation process. The nitrogen removal efficiency varied from 78% to 85%. COD removal efficiency was not affected during simultaneous precipitation and was varied from 94% to 98%. The highly efficient nitrogen removal in the presence of simultaneous precipitant ferrous sulphate makes the process an ideal option for nutrient removal.     

基质碳氮比对广叶绣球菌生长发育的影响

培养基质碳氮比显著影响食用菌菌丝生长及子实体生长发育.广叶绣球菌是一种珍贵的食药用真菌,前期研究发现其生长发育过程中对碳源的需求较多.本研究采用松木屑、复合氮源作为栽培原料,研究基质碳氮比对绣球菌菌丝生长及子实体生长发育的影响.结果 表明:6种不同碳氮比(C/N)的栽培基质对菌丝生长速度无显著影响,但是随着C/N比值的...     

Evaluation of biological nutrient removal from wastewater by Twin Circulating Fluidized Bed Bioreactor (TCFBBR) using a predictive fluidization model and AQUIFAS APP

A two-phase and three-phase predictive fluidization model based on the characteristics of a system such as media type and size, flow rates, and reactor cross sectional area was proposed to calculate bed expansion, solid, liquid and gas hold up and specific surface area (SSA) of the biofilm particles. The model was subsequently linked to 1d AQUIFAS APP software (Aquaregen) to model biological nutrient removal in two phase (anoxic) and three phase (aerobic) fluidized bed bioreactors. The credibility of the proposed model for biological nutrient removal was investigated using the experimental data from a Twin Circulating Fluidized Bed Bioreactors (TCFBBR) treating synthetic and municipal wastewater.The SSA of bio-particles and volume of the expanded bed were simulated as a function of operational parameters. Two-sided t-tests demonstrated that simulated SCOD, NH₄-N, NO₃-N, TN, VSS and biomass yields agreed with the experimental values at the 95% confidence level.     

Effect of influent COD/SO4(2-) ratios on mesophilic anaerobic reactor biomass populations: physico-chemical and microbiological properties

The competitive and syntrophic interactions between different anaerobic bacterial trophic groups in sulphate limited expanded granular sludge bed (EGSB) reactors was investigated. The outcome of competition between the sulphate-reducing, methanogenic and syntrophic populations after development in reactors at varying influent COD/SO4 (2-) ratios was examined in batch activity tests with the inclusion of specific sulphate reducing bacteria (SRB) and methane producing archaea (MPA) inhibitors. SRB species could not out-compete MPA species for acetate at influent COD/SO4 (2-) ratios as low as 2. The SRB were seen to play a more significant role in the conversion of hydrogen but did not become completely dominant. HMPA were responsible for hydrogen utilization at an influent COD/SO4 (2-) ratio of 16, and were still dominant when the ratio was reduced to 4. It was only when the COD/SO4 (2-) ratio was reduced to 2 that the HSRB assumed a more influential role. SRB species were significant in the degradation of propionate at all COD/SO4 (2-) ratios applied. Sludge samples were analysed by scanning electron microscopy (SEM), granule size distribution and fluorescent in situ hybridization (FISH), combined with confocal laser scanning microscopy (CLSM), to monitor any changes in granule morphology under the various COD/SO4 (2-) ratios imposed during the reactor trial. In situ hybridization with domain- and species-specific oligonucleotide probes demonstrated a layered architecture with an outer layer harboring mainly Eubacterial cells and an inner layer dominated by Archaeal species.     

Influence of wastewater composition on nitrogen and phosphorus removal and process control in A2O process

A bench-scale anaerobic–anoxic–oxic (A²O) bioreactor with steady denitrifying phosphorus removal performance was tested to determine the influence of influent C/N ratio (SCOD/TN) and C/P ratio (SCOD/TP) on biological nutrient removal for treating synthetic brewage wastewater; meanwhile, the spatial profiles of DO, pH and ORP sensors in such systems were investigated. The results showed that influent C/N ratio had significant effect on the TN, TP removal efficiencies and the ratio of anoxic to aerobic P uptake amount. The maximal TN and TP removal efficiencies could be achieved when influent C/N ratio was kept at about 7.1 and 5, respectively. Besides, the ratio of anoxic to aerobic P uptake amount was found to be linearly dependent on the influent C/N ratio with coefficient R ² of 0.685 when total recirculation ratio was constant at 3.5. Influent C/P ratio had an important effect on the TP removal efficiency, while it hardly affected TN removal efficiency. In addition, the TP removal efficiency reached the maximum for influent C/P ratio of 42. On the other hand, it was also found that the typical profiles of DO, pH and ORP sensors could be observed, and they have similar trends at the different influent C/N ratio and C/P ratio. It was suggested that the operational state could be well known according to the changes of simple on-line sensors.     

The performance of biological anaerobic filters packed with sludge-fly ash ceramic particles (SFCP) and commercial ceramic particles (CCP) during the restart period: Effect of the C/N ratios and filter media

Two lab-scale upflow biological anaerobic filters (BAF) packed with sludge-fly ash ceramic particles (SFCP) and commercial ceramic particles (CCP) were employed to investigate effects of the C/N ratios and filter media on the BAF performance during the restart period. The results indicated that BAF could be restarted normally after one-month cease. The C/N ratio of 4.0 was the thresholds of nitrate removal and nitrite accumulation. TN removal and phosphate uptake reached the maximum value at the same C/N ratio of 5.5. Ammonia formation was also found and excreted a negative influence on TN removal, especially when higher C/N ratios were applied. Nutrients were mainly degraded within the height of 25 cm from the bottom. In addition, SFCP, as novel filter media manufactured by wastes–dewatered sludge and fly ash, represented a better potential in inhibiting nitrite accumulation, TN removal and phosphate uptake due to their special characteristics in comparison with CCP.     

Effect of nitrite from nitritation on biological phosphorus removal in a sequencing batch reactor treating domestic wastewater

Although nitrite effect on enhanced biological phosphorus removal (EBPR) has been previously studied, very limited research has been undertaken about the effect of nitrite accumulation caused by nitritation on EBPR. This paper focused on nitrite effect from nitritation on EBPR in a sequencing batch reactor treating domestic wastewater. Results showed that nitrite of below 10 mg/L did not inhibit P-uptake and release; whereas EBPR deterioration was observed when nitrite accumulation reached 20 mg/L. Due to P-uptake prior to nitritation, nitrite of 20 mg/L has no effect on aerobic P-uptake. The main reason leading to EBPR deterioration was the competition of carbon source. Batch tests were conducted to investigate nitrite effect on anaerobic P-release. Under sufficient carbon source, nitrite of 30 mg/L had no impact on poly-β-hydroxyalkanoate (PHA) storage; contrarily, under insufficient carbon source, denitrifiers competing for carbon source with phosphorus accumulating organisms resulted in decrease of PHA synthesis and P-release.     

氮源及碳氮比对产朊假丝酵母合成谷胱甘肽的影响

研究了N源对产朊假丝酵母细胞生长和谷胱甘肽(GSH)合成的影响。在此基础上,分别以(NH4)2SO4和尿素作为单一N源,摇瓶条件下研究了不同C、N比对GSH发酵的影响。结果发现尿素有利于细胞生长,而(NH4)2SO4更有利于GSH的合成,并且酵母细胞在利用这2种N源合成GSH时,各自具有最佳的C、N比((NH4)2SO4为8.3 mol/mol,尿素为5.6 mol/mol)。最佳C、N比下的GSH分批发酵结果显示,尿素是更合适的N源,最终细胞干质量和GSH产量可以分别达到16.48 g/L和246.4 mg/L。最后分别采用发酵动力学模型和代谢网络分析对该结果产生的原因进行了定量解释。     

潜流型菖蒲人工湿地不同C/N对污染物的去除效率

选取炉渣和砾石为基质,以无植被为对照,分别设置低、中、高浓度的3个碳水平(C1、C2、C3)和3个氮水平(N1、N2、N3)处理,研究潜流型菖蒲人工湿地在不同C/N下净化生活污水中COD、总氮(TN)、总磷(TP)的效果。结果表明,在不同C/N下,菖蒲人工湿地对污水中COD、TN的去除效果显著高于无植被的人工湿地,菖蒲植被能增加人工湿地COD去除率10.53%,增加TN去除率6.73%;而对于TP的去除,有无植被无显著差异。随着进水N、P浓度及C/N的变化,菖蒲湿地对COD、TN和TP的去除率分别为67.57%～75.85%、20.91%～56.82%和7.15%～17.78%;同时,菖蒲植株对N、P的积累量也相应的变化,其地上部的N、P积累量为4.44～14.79和1.11～3.37g.m-2,平均占湿地N、P去除率的6.91%和10.67%;地下部的N、P积累量分别为2.35～5.20和0.74～1.41g.m-2,平均占湿地N、P去除率的2.69%和6.02%。植物地上器官对湿地N、P的积累量大于地下部,有利于通过收割作用去除湿地系统中的N、P。