进水COD浓度对厌氧同步脱氮除硫特性的影响

研究了不同进水有机物浓度条件下,接种物不同的厌氧体系的同步脱硫反硝化特性。结果表明:当进水COD浓度从零增加到250mg/L时,两个接种物不同的反应器对硫化物、硝态氮和COD的去除率变化不同。接种厌氧污泥的1#反应器对硫化物的去除率从85%逐渐增加到99%,80%～90%的进水COD被去除,但产气量逐渐降低,出现了亚硝态氮的积累,反硝化脱氮困难;接种脱氮硫杆菌到厌氧污泥中的2#反应器对硫化物的去除率一直稳定在99%,相应的产气量也逐渐增大,脱氮效率高,55%～73%的进水COD被去除。此外,在这个浓度范围内,还观察到两个反应器出水硫酸盐的浓度由不加乙酸钠的23mg/L分别降到18mg/L和19mg/L,理论上硫转化率提高了4%～19%。当进水COD400mg/L时,仅60%～76%的硫化物被去除,相应的产气量也迅速降低,硫化物的氧化和反硝化过程均明显受到抑制。总而言之,在进水COD为250mg/L时,2#反应器对硫化物和硝态氮的去除率均达到了100%左右,对硫化物的比降解速率和产气量也提高了1.1～1.2倍,相应的出水硫酸盐浓度最低,80%左右的硫化物转化为单质硫,73%的COD被去除,可以实现同时脱氮、除硫和除碳,为同步脱氮除硫工艺的实际应用提供了新的思路。     

进水氨氮对厌氧同步脱氮除硫工艺的影响

通过比较含氨氮和不含氨氮两种进水水质条件下接种物不同的两个反应器的脱氮除硫特性,研究进水氨氮对厌氧同步脱氮除硫性能的影响。结果表明,进水未加氨氮的反应器对硫化物和硝态氮的去除率均高达95%,当加入氨氮后,仅有40%～50%的硝态氮被去除,消耗1 g硫化物所还原的硝态氮量减少,去除硝态氮的能力降低了近50%,然而对硫化物的去除率仍维持在90%左右,表明脱氮过程比脱硫过程受进水氨氮的影响大。扫描电镜观察结果证实,当进水中存在氨氮时硫化物的毒性增大,杀死了大量的脱氮硫杆菌,降低了硫化物转化为单质硫的能力,干扰了系统的反硝化脱氮过程,这是导致体系脱氮能力降低的主要原因。     

火化烟气吸收液的硫自养反硝化深度脱氮研究

基于硫自养反硝化工艺研究了火化烟气吸收液的深度脱氮过程与调控技术。通过逐级提高硝态氮负荷的方式可以在30 d内使硝态氮去除率提高至89.0%，石灰石可以有效替代碳酸氢钠为反应系统提供碱度，使自养反硝化菌群稳定发挥脱氮能力。相比于硫酸盐，亚硝态氮表现出更为明显的自养反硝化功能菌群毒性抑制效果，但是在功能菌群适应进水水质后，系统的硝态氮去除率均高于93.2%。定期反冲洗可以防止硫磺填料板结现象的发生，从而使系统维持较好的硝态氮去除效果。Thiobacillus sp.和Sulfrimonas sp.是系统中的优势菌群，相对丰度占总自养脱氮功能菌群的70.5%以上，但是Sulfuricurvum sp.的相对丰度则明显降低，主要原因在于其不能还原亚硝态氮。     

N/S值和电子受体对厌氧生物脱氮除硫的影响

分别以NO_3~-和NO-2为氮源,在9个不同N/S值条件下进行厌氧脱氮除硫试验。结果表明:当N/S值0.67时,硝酸盐体系的出水硫化物浓度均小于1.0 mg/L,硫化物去除率达99%,脱硫速度明显高于亚硝酸盐体系,即N_3~-是脱硫最佳的电子受体。硫化物加速了对NO-2的去除,即使将N/S值提高为4,对NO-2的去除率仍高达99%,硫化物是去除NO-2适宜的电子供体。硝酸盐体系的出水单质硫浓度明显高于亚硝酸盐体系,亚硝酸盐不利于单质硫富集。硝酸盐体系的N/S值从0.2增大为1时,大部分的N_3~-被转化为N2(产生氮气14~58 m L);而当硫化物不足时(N/S值从1继续增大为4),NO_3~-不能被全部转化为N2。对于亚硝酸盐体系而言,去除的NO-2基本全部生成N2。当NO-2受限时(N/S值0.4)产生了大量的N2(48 m L),此时部分进水氨氮可能被去除。硝酸盐、亚硝酸盐体系中,硫化物过量时(N/S值=0.2),电子数的差均较高,分别为59%和66%;二者分别在N/S值为1、2时,电子数的差为零,电子得失达到平衡。     

玉米芯与海绵铁复合填料的反硝化脱氮特性

在实验室条件下分别运行以玉米芯/海绵铁复合填料和单纯玉米芯填料的反硝化滤池,分析两类填料的反硝化脱氮效果,考察复合填料对硝态氮的去除率及出水水质。结果表明,复合填料反硝化滤池以生物异养反硝化作用为主,较单纯玉米芯填料反应器表现出更加稳定的反硝化脱氮效果。当进水硝态氮浓度为20 mg/L、停留时间3 h时,复合填料反应器对硝态氮的去除率可以维持在90%以上,出水硝态氮浓度2 mg/L,没有出现亚硝态氮、氨氮的积累和pH值升高现象;3个月的运行期间单位质量玉米芯的脱氮量为0.42 kg/kg,比单纯玉米芯高0.05 kg/kg。因此,玉米芯/海绵铁复合填料作为反硝化滤池的碳源和生物载体具有脱氮效果好、无需连续添加碳源、出水pH值稳定的特点。     

低温对硫自养反硝化脱氮系统的影响及调控措施

为了提高低温下硫自养反硝化系统的脱氮性能,通过改变电子供体(硫源),并结合异养反硝化作用,利用序批试验,比较了不同温度下反应系统的脱氮性能。试验结果表明,低温条件下硫自养反硝化脱氮作用受到明显的抑制,5℃时硝态氮的还原反应速率常数为0. 003 7 mg~(0.5)/(L~(0.5)·h),仅为25℃时的3. 2%,并且亚硝态氮积累严重,p H值降低明显。相较于单质硫,低温条件下投加硫代硫酸盐或乙酸盐后,系统的反应速率常数分别提升2. 81倍和8. 49倍。加入乙酸盐能够有效缓解亚硝态氮的积累,5℃时亚硝态氮的还原反应速率常数为0. 200 0 mg~(0.5)/(L~(0.5)·h),而加入单质硫或硫代硫酸盐试验组的亚硝态氮浓度没有明显下降。     

厌氧氨氧化与反硝化耦合启动影响因素

为避免实际废水中一定浓度的有机物对厌氧氨氧化的脱氮产生不利影响,向2组启动成功的厌氧氨氧化装置之一R2中投加有机COD(C/N=0. 6)与反硝化耦合协同脱氮,并以硝酸盐为电子受体,R1中不加有机物作为对比,定期测定脱氮效果与有机碳源消耗。结果表明:R1中厌氧氨氧化菌自身可利用少量硝酸盐进行厌氧氨氧化反应,氨氮、硝态氮去除率分别为26. 7%和30. 5%; R2装置中两种菌种协同脱氮,氨氮、硝态氮去除率分别提高至36. 4%和48. 6%,出水亚硝态氮稳定在4 mg/L以下,碳源利用率在90%以上,但2组装置对磷的利用几乎为零。适当投加有机物可促使厌氧氨氧化与反硝化耦合协同脱氮,为含碳和硝酸盐废水的脱氮除碳提供了参考。     

羟基氧化铁强化低C/N废水生物反硝化脱氮研究

针对处理低C/N废水过程中传统生物反硝化效率低的技术难题，在活性污泥反硝化系统中投加羟基氧化铁，研究羟基氧化铁对C/N逐渐降低废水反硝化效率的影响。结果表明，在C/N为10、7.5时，羟基氧化铁对硝态氮去除率的影响不明显；当C/N为5、2.5时，投加羟基氧化铁可使硝态氮去除率分别提高16.38%和15.76%，同时加快了系统对反硝化中间产物亚硝态氮的去除。另外，投加羟基氧化铁还促进了胞外聚合物（EPS）中蛋白质（PN）和多糖（PS）的分泌，降低了传统反硝化亚硝酸还原酶（NIR）的活性。羟基氧化铁可以改变微生物的群落结构，使系统能够富集Uncultured＿bacterium＿f＿Gemmatimonadaceae和Neochlamydia等脱氮菌，诱导发生硝酸盐型厌氧亚铁氧化，实现传统反硝化和硝酸盐型厌氧亚铁氧化协同去除硝态氮。     

可降解硝态氮的歧化厌氧氨氧化颗粒污泥的驯化

向SBR反应器中接种成熟的厌氧氨氧化颗粒污泥,在氨氮、亚硝态氮浓度均为100mg/L的条件下,按C/N值=0.1添加乙酸钠,研究乙酸钠对厌氧氨氧化菌去除氮素的影响。结果表明,在存在乙酸钠的条件下,出水硝态氮生成量为没有乙酸钠情况下的45%,对总氮的去除率提高到90%以上,有利于出水总氮浓度达到一级A标准。验证了在C/N值=0.1条件下,厌氧氨氧化反应是反应器中的主体反应,没有被反硝化反应取代。厌氧氨氧化菌可利用乙酸钠和硝态氮的代谢机制也为降低短程硝化控制难度提供了一种思路。     

人工湿地的反硝化能力研究

利用人工湿地的反硝化作用进行去除硝态氮的试验,其反硝化碳源主要为植物根系的分泌物及湿地内腐败的死亡植株.结果表明,人工湿地内有着适宜反硝化的反应环境,反硝化茵能够很好地利用湿地内产生的碳源进行反硝化作用来去除硝态氮,且不会出现亚硝态氮的大量积累.在进水(NO3-)-N浓度为20-50 mg/L、水力停留时间为24 h的条件下,夏季运行时,湿地系统对硝态氮的去除率为20%～30%;冬季运行时,对硝态氮的去除率在10%左右.提供充足的反硝化碳源是硝态氮去除率进一步提高的瓶颈.     

A novel sulfate reduction, autotrophic denitrification, nitrification integrated (SANI) process for saline wastewater treatment

This paper reports on a lab-scale evaluation of a novel and integrated biological nitrogen removal process: the sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) process that was recently proposed for saline sewage treatment. The process consisted of an up-flow anaerobic sludge bed (UASB) for sulfate reduction, an anoxic filter for autotrophic denitrification and an aerobic filter for nitrification. The experiments were conducted to evaluate the performance of the lab-scale SANI system with synthetic saline wastewater at various hydraulic retention times, nitrate concentrations, dissolved oxygen levels and recirculation ratios for over 500 days. The system successfully demonstrated 95% chemical oxygen demand (COD) and 74% nitrogen removal efficiency without excess sludge withdrawal throughout the 500 days of operation. The organic removal efficiency was dependent on the hydraulic retention time, up-flow velocity, and mixing conditions in the UASB. Maintaining a sufficient mixing condition in the UASB is important for achieving effective sulfate reduction. For a typical Hong Kong wastewater composition 80% of COD can be removed through sulfate reduction. A minimum sulfide sulfur to nitrate nitrogen ratio of 1.6 in the influent of the anoxic filter is necessary for achieving over 90% nitrate removal through autotrophic denitrifiers which forms the major contribution to the total nitrogen removal in the SANI system. Sulfur balance analyses confirmed that accumulation of elementary sulfur and loss of hydrogen sulfide in the system were negligible.     

Simultaneous biological removal of nitrogen, carbon and sulfur by denitrification

Refinery wastewaters may contain aromatic compounds and high concentrations of sulfide and ammonium which must be removed before discharging into water bodies. In this work, biological denitrification was used to eliminate carbon, nitrogen and sulfur in an anaerobic continuous stirred tank reactor of 1.3 L and a hydraulic retention time of 2 d. Acetate and nitrate at a C/N ratio of 1.45 were fed at loading rates of 0.29 kg C/m3 d and 0.2 kg N/m3 d, respectively. Under steady-state denitrifying conditions, the carbon and nitrogen removal efficiencies were higher than 90%. Also, under these conditions, sulfide (S(2-)) was fed to the reactor at several sulfide loading rates (0.042-0.294 kg S(2-)/m3 d). The high nitrate removal efficiency of the denitrification process was maintained along the whole process, whereas the carbon removal was 65% even at sulfide loading rates of 0.294 kg S(2-)/m3 d. The sulfide removal increased up to approximately 99% via partial oxidation to insoluble elemental sulfur (S0) that accumulated inside the reactor. These results indicated that denitrification is a feasible process for the simultaneous removal of nitrogen, carbon and sulfur from effluents of the petroleum industry.     

Steady-state model-based evaluation of sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) process

Recently we developed a process for wastewater treatment in places where part of the fresh water usage is replaced by seawater usage. The treatment of this saline sewage consists of sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) process. The process consists of an up-flow anaerobic sludge bed (UASB) for sulfate reduction, an anoxic filter for autotrophic denitrification using dissolved sulfide produced in the UASB and an aerobic filter for nitrification. The system was operated for 500 days with 97% COD removal and 74% total nitrogen removal without withdrawal of sludge. To verify these results and to understand this novel process, a steady-state model was developed from the COD, nitrogen and sulfur mass and charge balances based on the stoichiometries of the sulfate reduction, the autotrophic denitrification and the autotrophic nitrification. The model predictions agreed well with measured data on COD, nitrate and sulfate removal, sulfide production, effluent TSS, and mass balances of COD, sulfur and nitrogen in the three reactors. The model explains why withdrawal of sludge from the SANI system is not needed through comparisons of the predictions and measurements of effluent TSS and phosphorus concentrations.     

Heterotrophic activity compromises autotrophic nitrogen removal in membrane-aerated biofilms: results of a modeling study

A 1-d multi-population biofilm model was constructed to study the effect of heterotrophic activity on completely autotrophic ammonium (NH4+) removal in membrane-aerated (counter-diffusion) versus conventional biofilm systems (co-diffusion). Growth of heterotrophic bacteria (HB) was supported either solely by biomass decay products or by organic carbon (as chemical oxygen demand (COD)) in the influent. Three scenarios were considered: influence of HB growing on biomass decay products on steady-state performance (total nitrogen (TN) removal efficiency); influence of the influent COD/N ratio on steady-state performance (supplying COD in the influent); and impact of dynamic changes in the influent COD/N ratio on TN removal efficiency. The results revealed that the TN removal efficiency in the counter-diffusion biofilm was significantly different when HB were included in the simulations at NH4+ surface loads of LNH4>2.7 g - N m(-2) d(-1). Influent COD significantly altered the microbial community composition in the counter-diffusion biofilm and anaerobic NH4+ oxidation could not be sustained at COD/N>2. The co-diffusion system, however, was less affected and more than 50% of the TN removal originated from anaerobic NH4+ oxidation at those ratios. Perturbation experiments showed that step increases to influent COD/N ratios of 2 or higher over a period of 50 d or longer caused a loss of anaerobic NH4+ oxidation capacity which could not be regained within a reasonable time frame (>1000 d) in the counter-diffusion system. In contrast, simulating a 1-d sloughing event only caused a disturbance of 200 d although a maximum biofilm loss of 90-95% occurred. These results clearly indicate the importance of heterotrophic activity in autotrophic N removal biofilms, especially in counter-diffusion systems where they may compromise N removal capacity.     

DEAMOX--new biological nitrogen removal process based on anaerobic ammonia oxidation coupled to sulphide-driven conversion of nitrate into nitrite

This paper reports about the successful laboratory testing of a new nitrogen removal process called DEAMOX (DEnitrifying AMmonium OXidation) for treatment of typical strong nitrogenous wastewater such as baker's yeast effluent. The concept of this process combines the recently discovered anammox (anaerobic ammonium oxidation) reaction with autotrophic denitrifying conditions using sulphide as an electron donor for the production of nitrite from nitrate within an anaerobic biofilm. To generate sulphide and ammonia, a Upflow Anaerobic Sludge Bed (UASB) reactor was used as a pre-treatment step. The UASB effluent was split and partially fed to a nitrifying reactor (to generate nitrate) and the remaining part was directly fed to the DEAMOX reactor where this stream was mixed with the nitrified effluent. Stable process performance and volumetric nitrogen loading rates of the DEAMOX reactor well above 1000 mgN/l/d with total nitrogen removal efficiencies of around 90% were obtained after long-term (410 days) optimisation of the process. Important prerequisites for this performance are appropriate influent ratios of the key species fed to the DEAMOX reactor, namely influent N-NO(x)/N-NH(4) ratios >1.2 (stoichiometry of the anammox reaction) and influent S-H(2)S/N-NO(3) ratios >0.57 mgS/mgN (stoichiometry of the sulphide-driven denitrification of nitrate to nitrite). The paper further describes some characteristics of the DEAMOX sludge as well as the preliminary results of its microbiological characterisation.     

Kinetic model of autotrophic denitrification in sulphur packed-bed reactors

Autotrophic denitrification of synthetic wastewater by Thiobacillus denitrificans in upflow sulphur packed-bed reactors was studied in order to establish the process kinetics for prediction of effluent concentration. Elemental sulphur particles of different size served as energy substrate as well as the physical support for the microbial biofilm. Experiments were performed under operating conditions of (i) different flow rates at constant influent nitrate concentration; and (ii) different influent nitrate concentrations at constant flow rate. The experimental results show that autotrophic denitrification rates in upflow sulphur packed-bed reactors can be described by a half-order kinetic model for biofilms. It was found that the half-order kinetic constants of upflow packed-bed reactors are 2.94-3.60, 1.47-2.04, and 1.12-1.29 mg1/2/L1/2 h for sulphur particle sizes of 2.8-5.6, 5.6-11.2, and 11.2-16 mm, respectively. The half-order kinetic constants could be related to the specific surface area of the reactor media by a simple equation. Successful application of the half-order reaction rate model was demonstrated for an actual wastewater (nitrified leachate). A comparison with the literature showed that the half-order reaction rate constants for autotrophic denitrification using elemental sulphur are approximately one order of magnitude lower than those of heterotrophic denitrification. An improved stoichiometric equation for autotrophic denitrification using elemental sulphur as electronic donor is also proposed.     

缺氧生物膜滤池的自养脱氮性能研究

在成功实现亚硝酸盐自养脱氮(厌氧氨氧化)的基础上,探讨了亚硝酸盐浓度对缺氧生物膜滤池脱氮性能的影响。结果显示,在一定范围内提高亚硝酸盐浓度可加快氨氮去除速率,当NO2--N为118.4 mg/L时氨氮去除速率达到最大;此后,进一步提高进水NO2--N浓度会对氨氮的去除产生明显的抑制作用,导致反应速率下降,但此时的厌氧氨氧化菌仍具有较高的活性;为获得良好的脱氮效果,应控制进水NO2--N/NH4 -N值为1.3。     

Sulfide-induced nitrate reduction in the sludge of an anaerobic digester of a zero-discharge recirculating mariculture system

The anaerobic digester is a vital component in a zero-discharge mariculture system as therein most of the organic matter is mineralized and nitrogen-containing compounds are converted to gaseous N₂. Although denitrification is a major respiratory process in this nitrate-rich treatment stage, also sulfate respiration takes place and may cause undesirable high sulfide concentrations in the effluent water. To examine the effect of sulfide on nitrate reduction, in situ depth profiles of inorganic nitrogen and sulfur compounds were determined. Additionally, nitrate reduction was examined as a function of ambient sulfide concentrations in sludge collected from different locations in the anaerobic reactor. Depth profiles showed high concentrations of nitrate and low concentrations of sulfide and ammonia in the aqueous layer of the reactor. A sharp decrease of nitrate and an increase in sulfide and ammonia concentrations was measured at the water-sludge interface. Nitrate reduction was highest in this interface zone with rates of up to 8.05 ± 0.57 μmol NO₃⁻ h⁻¹ g_(sludge)⁻¹. Addition of sulfide increased the nitrate reduction rate at all sludge depths, pointing to the important role of autotrophic denitrification in the anaerobic reactor. Dissimilatory nitrate reduction to ammonia (DNRA) was found to be low in all sludge layers but was enhanced when sludge was incubated at high sulfide concentrations. Although nitrate reduction rates increased as a result of sulfide addition to sludge samples, no differences in nitrate reduction rates were observed between the samples incubated with different initial sulfide concentrations. This as opposed to sulfide oxidation rates, which followed Michaelis-Menten enzymatic kinetics. Partial oxidation of sulfide to elemental sulfur instead of a complete oxidation to sulfate, could explain the observed patterns of nitrate reduction and sulfide oxidation in sludge incubated with different initial sulfide concentrations.     

Nitrogen transformations in a wetland receiving lagoon effluent: sequential model and implications for water reuse

Constructed wetlands could be components of low-tech systems to treat and reuse wastewater in arid region. A key function of the wetland would be to provide additional N removal. To improve design criteria, a sequential model of nitrogen transformations (organic N --> ammonium: ammonium --> nitrate: nitrate --> nitrogen gas) was successfully calibrated and verified for a wetland in Kingman, Arizona. A sequential model has the ability to "recognize" species of nitrogen in the influent and predict species of nitrogen in the effluent. Model scenarios show that increasing nitrification rates in the summer and denitrification rates in the winter would improve nitrogen removal efficiencies. Several lines of evidence suggest that wintertime denitrification may be limited by carbon supply. Winter carbon supply could be augmented by routing a portion of the water through channels planted with dryland vegetation.