Multistage wastewater treatment using separated storage driven denitrification and nitrification biofilms.

The feasibility of combining a previously reported storage driven denitrification biofilm, where 80% of influent acetate can be converted to poly-beta-hydroxybutyrate (PHB), with a suitable nitrification reactor, either submerged or trickling filter design, to achieve complete biological nitrogen removal was tested. The reactor system showed the potential of complete biological nitrogen removal of waste streams with a C/N ratio as low as 3.93 kg COD/kg N-NH3 at an overall nitrogen removal rate of 1.1 mmole NH3/L/h. While the efficiency and the rates of nitrogen removal were higher than what is observed in traditional or simultaneous nitrification and denitrification (SND) systems, there were two problems that require further development: (a) the incomplete draining of the reactor caused ammonia retention and release in the effluent, limiting the overall N-removal and (b) pH drifts in the nitrification step slowed down the rate of nitrification if not corrected by appropriate pH adjustment or buffering.     

Nitrogen removal from sludge reject water by a two-stage oxygen-limited autotrophic nitrification denitrification process.

Nitrogen removal from sludge reject water was obtained by oxygen-limited partial nitritation resulting in nitrite accumulation in a first stage, followed by autotrophic denitrification of nitrite with ammonium as electron donor (similar to anaerobic ammonium oxidation) in a second stage. Two membrane-assisted bioreactors (MBRs) were used in series to operate with high sludge ages and subsequent high volumetric loading rates, achieving 1.45 kg N m(-3) day(-1) for the partial nitritation MBR and 1.1 kg N m(-3) day(-1) for the anaerobic ammonium oxidation MBR. Biomass retention in the nitritation stage ensured flexibility towards loading rate and operating temperature. Nitrite oxidisers were out-competed at low oxygen and high free ammonia concentration. Biomass retention in the second MBR prevented wash-out of the slowly growing bacteria. Nitrite and ammonium were converted to dinitrogen gas in a reaction ratio of 1.05, thereby maintaining nitrite limitation to assure process stability. The anoxic consortium catalysing the autotrophic denitrification process consisted of Nitrosomonas-like aerobic ammonium oxidizers and anaerobic ammonium oxidizing bacteria closely related to Kuenenia stuttgartiensis. The overall removal efficiency of the combined process was 82% of the incoming ammonium according to a total nitrogen removal rate of 0.55 kg N m(-3) day(-1), without adding extra carbon source.     

Biological nutrient removal in membrane bioreactors: denitrification and phosphorus removal kinetics.

The impact of including membranes for solid liquid separation on the kinetics of nitrogen and phosphorus removal was investigated. To achieve this, a membrane bioreactor (MBR) biological nutrient removal (BNR) activated sludge system was operated. From batch tests on mixed liquor drawn from the MBR BNR system, denitrification and phosphorus removal rates were delineated. Additionally the influence of the high total suspended solids concentrations present in the MBR BNR system and of the limitation of substrate concentrations on the kinetics was investigated. Moreover the ability of activated sludge in this kind of system to denitrify under anoxic conditions with simultaneous phosphate uptake was verified and quantified.The denitrification rates obtained for different mixed liquor (ML) concentrations indicate no effect of ML concentration on the specific denitrification rate. The denitrification took place at a single specific rate (K(2)) with respect to the ordinary heterotrophic organisms (OHOs, i.e. non-PAOs) active mass. Similarly, results have been obtained for the P removal process kinetics: no differences in specific rates were observed for different ML or substrate concentrations. From the P removal batch tests results it seems that the biological phosphorus removal population (PAO) consists of 2 different sets of organisms denitrifying PAO and aerobic PAO.     

溶解氧对同步硝化反硝化脱氮影响研究

以实际生活污水为处理对象,利用生物膜内所具有的A/O环境,针对DO浓度对生物膜法同步脱氮效果影响进行试验研究.研究结果表明,在DO为2.5 mg/L时SND脱氮效果达最佳,TN去除率近70%;DO浓度过高或过低都不利于生物膜内部DO浓度梯度的形成,合理控制DO浓度,对生物膜法同步脱氮尤为重要.     

同步硝化反硝化的影响因素研究

为了深入研究同步硝化反硝化(SND)的影响因素,试验研究了SBR工艺中C/N、DO和pH对SND率的影响.试验结果表明,在DO=0.45 mg/L、C/N在3.33～8.32的情况下,SND率随着C/N的升高而线性升高.当C/N超过8.32时,SND率增速减缓.在C/N=8.32、DO 0.2～0.4 mg/L的情况下,SND率随DO的升高而升高,当DO超过0.4 mg/L时,SND率开始下降.在C/N=8.32、pH处于7.6～8.4的情况下,SND率随着pH的增加先升高后下降,当pH处于8时,SND率达到最高.     

Performance and microbial ecology of the hybrid membrane biofilm process for concurrent nitrification and denitrification of wastewater.

We report on a novel process for total nitrogen (TN) removal, the hybrid membrane biofilm process (HMBP). The HMBP uses air-supplying hollow-fibre membranes inside an activated sludge tank, with suppressed aeration, to allow concurrent nitrification and denitrification. We hypothesised that a nitrifying biofilm would form on the membranes, and that the low bulk-liquid BOD concentrations would encourage heterotrophic denitrifying bacteria to grow in suspension. A nitrifying biofilm was initially established by supplying an influent ammonia concentration of 20 mgN/L. Subsequently, 120 mg/L acetate was added to the influent as BOD. With a bulk-liquid SRT of only 5 days, nitrification rates were 0.85 gN/m(2) per day and the TN removal reached 75%. The biofilm thickness was approximately 500 lim. We used DGGE to obtain a microbial community fingerprint of suspended and attached growth, and prepared a clone library. The DGGE results, along with the clone library and operating data, suggest that nitrifying bacteria were primarily attached to the membranes, while heterotrophic bacteria were predominant in the bulk liquid. Our results demonstrate that the HMBP is effective for TN removal, achieving high levels of nitrification with a low bulk-liquid SRT and concurrently denitrifying with BOD as the sole electron donor.     

Nitrogen removal from pharmaceutical manufacturing wastewater with high concentration of ammonia and free ammonia via partial nitrification and denitrification.

In this study, laboratory-scale experiments were conducted applying a Sequencing Batch Reactor (SBR) activated sludge process to a wastewater stream from a pharmaceutical factory. Nitrogen removal can be achieved via partial nitrification and denitrification and the efficiency was above 99% at 23 degrees C+/-1. The experimental results indicated that the nitrite oxidizers were more sensitive than ammonia oxidizers to the free ammonia in the wastewater. The average accumulation rate of nitrite was much higher than that of nitrate. During nitrogen removal via the nitrite pathway, the end of nitrification and denitrification can be exactly decided by monitoring the variation of pH. Consequently, on-line control for nitrogen removal from the pharmaceutical manufacturing wastewater can be achieved and the cost of operation can be reduced.     

曝气生物滤池内同步硝化反硝化的研究进展

笔者以1984—2009年发表在国内外期刊上的关于BAF研究与应用的多篇文献为基础,对曝气生物滤池中的同步硝化反硝化作用从宏观、微观和微生物角度进行机理分析,并从DO、C/N、pH以及滤料角度对影响脱氮过程的因素进行探讨,最后对曝气生物滤池同步硝化反硝化研究进行展望。     

A new oxygen supply method for simultaneous organic carbon removal and nitrification by a one-stage biofilm process

A new oxygen supply method to biofilm is proposed for simultaneous organic carbon removal and nitrification. The main feature of the method is use of hydrophobic porous membrane or oxygen enrichment membrane as substratum of biofilm. In the biofilm formed on oxygen permeable membrane, oxygen is supplied from the bottom to the surface of the biofilm through the membrane while organic pollutants are supplied from the surface to the bottom of the biofilm. The oxygen supply method allows nitrifiers near the bottom region to grow with less competition from BOD oxidizers. The microbial population was investigated in the biofilm formed on hydrophobic microfilter. Nitrifiers grew mainly in the bottom region while denitrifiers grew in the middle region of the biofilm formed on the membrane. Simultaneous organic carbon removal and nitrification were carried out successfully by the biofilm. Furthermore, the potential of the new oxygen supply method was demonstrated with the biofilm formed on an oxygen enrichment-type biomass carrier in a single-stage treatment of domestic wastewater. The nitrification rate was about 1.9 g/m²d and was comparable to that in the conventional biofilm process designed especially for nitrification.     

Free water surface wetlands for wastewater treatment in Sweden: nitrogen and phosphorus removal.

In South Sweden, free water surface wetlands have been built to treat wastewater from municipal wastewater treatment plants. Commonly, nitrogen removal has been the prime aim, though a significant removal of tot-P and BOD7 has been observed. In this study, performance data for 3-8 years from four large (20-28 ha) FWS wetlands have been evaluated. Two of them receive effluent from WWTP with only mechanical and chemical treatment. At the other two, the wastewater has also been treated biologically resulting in lower concentrations of BOD7 and NH4+-N. The wetlands performed satisfactorily and removed 0.7-1.5 ton N ha(-1) yr(-1) as an average for the time period investigated, with loads between 1.7 and 6.3 ton N ha(-1)yr(-1). Treatment capacity depended on the pre-treatment of the water, as reflected in the k20-values for N removal (first order area based model). In the wetlands with no biological pre-treatment, the k20-values were 0.61 and 1.1 m month(-1), whereas for the other two they were 1.7 and 2.5 m month(-1). P removal varied between 10 and 41 kg ha(-1) yr(-1), and was related to differences in loads, P speciation and to the internal cycling of P in the wetlands.     

The presence of ammonium facilitates nitrite reduction under PHB driven simultaneous nitrification and denitrification.

For economic and efficient nitrogen removal from wastewater treatment plants via simultaneous nitrification and denitrification the nitrification process should stop at the level of nitrite such that nitrite rather than nitrate becomes the substrate for denitrification. This study aims to contribute to the understanding of the conditions that are necessary to improve nitrite reduction over nitrite oxidation. Laboratory sequencing batch reactors (SBRs) were operated with synthetic wastewater containing acetate as COD and ammonium as the nitrogen source. Computer controlled operation of the reactors allowed reproducible simultaneous nitrification and denitrification (SND). The oxygen supply was kept precisely at a low level of 0.5 mgL(-1) and bacterial PHB was the only electron donor available for denitrification. During SND little nitrite or nitrate accumulated (< 20% total N), indicating that the reducing processes were almost as fast as the production of nitrite and nitrate from nitrification. Nitrite spiking tests were performed to investigate the fate of nitrite under different oxidation (0.1-1.5 mgL(-1) of dissolved oxygen) and reduction conditions. High levels of reducing power were provided by allowing the cells to build up to 2.5 mM of PHB. Nitrite added was preferentially oxidised to nitrate rather than reduced even when dissolved oxygen was low and reducing power (PHB) was excessively high. However, the presence of ammonium enabled significant reduction of nitrite under low oxygen conditions. This is consistent with previous observations in SBR where aerobic nitrite and nitrate reduction occurred only as long as ammonium was present. As soon as ammonium was depleted, the rate of denitrification decreased significantly. The significance of the observed strongly stimulating effect of ammonium on nitrite reduction under SND conditions is discussed and potential consequences for SBR operation are suggested.     

短程生物脱氮与同步除磷的中试研究

交互式反应器运行倒置A2/O处理低碳高氮城市污水,在其好氧段通过控制DO为0.5~1mg/L,进行短程硝化研究。结果表明:在总HRT为10h条件下,经过1个月左右稳定运行后,亚硝氮的累积率可以达到50%以上,最高达到75%左右,而且反应器对总氮的去除也有明显改善,出水总氮平均在10mg/L左右。亚硝酸盐在预缺氧区和缺氧区的反硝化反应较为彻底,进入厌氧池后不会对厌氧段生物释磷产生抑制。但是,低氧条件下的短程硝化过程会导致污泥沉降性能恶化,容易产生污泥膨胀,不过通过控制好氧末端的后曝气提高DO可以改善污泥的性状。     

污水处理厂反硝化除磷研究及实践

结合苏州娄江污水处理厂生产运行实践,研究了改良型一体化交替反应池在实现良好反硝化除磷条件下的运行工况.实践表明,提高反硝化除磷的关键是要有充足的硝酸盐氮为反硝化聚磷菌(DPB)提供电子受体,当NO-2N浓度在5 mg/L以上时,可以实现较好的反硝化除磷;当SRT为12～14 d时,反硝化除磷和系统脱氮除磷效果最好,生物除磷运行成本较低.此外,进水COD/TP、好氧池DO、厌氧池MLSS以及SRT也是影响一体化反应池生物除磷的主要因素.针对雨季低负荷运行除磷效果不理想的现象,提出了相应的工况运行措施.     

MBR的脱氮除磷工艺研究

采用厌氧/缺氧池/好氧MBR工艺处理模拟的城市生活污水,就系统主要的运行参数对氮磷去除的影响进行了研究.结果表明:TN、TP、NH3-N去除率分别达到80%、90%、95%以上,出水各项指标完全满足城市杂用水水质标准的要求.     

化学除油法在济钢中厚板高压除磷水中的应用

化学除油器除油法是以投加化学药剂,经混合反应使水中的油类、氧化铁皮等悬浮物通过絮凝、凝聚作用去除.济钢中厚板高压除磷水系统采用化学除油法将浊水中的乳化油、悬浮物进行处理,使出水含油量≤5 mg/L,SS≤10 mg/L,提高了出水水质和产品质量.     

BICT biological process for nitrogen and phosphorus removal.

An updated biological nitrogen and phosphorus removal process--BICT (Bi-Cyclic Two-Phase) biological process--is proposed and investigated. It is aimed to provide a process configuration and operation mode that has facility and good potential for optimizing operation conditions, especially for enhancing the stability and reliability of the biological nutrient removal process. The proposed system consists of an attached-growth reactor for growing autotrophic nitrifying bacteria, a set of suspended-growth sequencing batch reactors for growing heterotrophic organisms, an anaerobic biological selector and a clarifier. In this paper, the fundamental concept and operation principles of BICT process are described, and the overall performances, major operation parameters and the factors influencing COD, nitrogen and phosphorus removal in the process are also discussed based on the results of extensive laboratory experiments. According to the experimental results with municipal sewage and synthetic wastewater, the process has strong and stable capability for COD removal. Under well controlled conditions, the removal rate of TN can reach over 80% and TP over 90% respectively, and the effluent concentrations of TN and TP can be controlled below 15 mg/L and 1.0 mg/L respectively for municipal wastewater. The improved phosphorus removal has been reached at short SRT, and the recycling flow rate of supernatant between the main reactors and attached-growth reactor is one of the key factors controlling the effect of nitrogen removal.     

Agricultural use of municipal wastewater sludges: phosphorus availability of biological excess phosphorus removal sludges.

Reuse of sewage sludges as phosphorus fertiliser requires the estimation of the plant availabilities of phosphorus (P) from different sludges. This study investigates the effect of lime stabilisation on the phosphorus availability from biological phosphorus removal sludges. In the first part of the study, pot experiments were carried out to assess the fertilising effect of a dewatered biological phosphorus removal sludge. Availability of P was determined in terms of plant-uptake. In the second part of the study, incubation tests were carried out to observe the change in the available P with time when the waste activated sludge (WAS) from an enhanced biological phosphorus removal (EBPR) process is mixed with the same soil. In this part, the plant available P was measured in terms of Olsen extractable P. A P-deficient, alkaline soil was used in the experiments and Lollium Perenne was selected as the testing plant. The results of the pot experiments revealed that lime-stabilisation of the sludge considerably decreased or retarded the availability of P in the sludge. In the incubation tests, the availability of phosphorus in the lime stabilised and nonstabilised sludge amended soil samples was close to each other. In general, P-availability was increased due to the sludge application except for the lime-stabilised dewatered sludge.     

Microbial community of biological phosphorus removal process fed with municipal wastewater under different electron acceptor conditions.

The microbial community in a biological phosphorus removal process under different electron acceptor conditions was estimated by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) assay and principal-component analysis (PCA). For this purpose, a lab-scale sequencing batch reactor (SBR) fed with municipal wastewater was operated under anaerobic-aerobic, anaerobic-anoxic-aerobic and anaerobic-anoxic conditions. The results of PCR-DGGE targeting the 16S rRNA gene indicated a significant shift in the microbial community with electron acceptor conditions. From the 16S rRNA-based PCA, the microbial shift implies that little oxygen supply caused the deterioration of aerobic bacteria, including aerobic polyphosphate-accumulating organisms (PAOs). Moreover, it also reflects the existence of nitrate-utilizing denitrifiers. On the other hand, although the band patterns of DGGE targeting a functional gene of denitrification (nirS) also showed the microbial shift, the result of PCA differed from that of 16S rRNA-based analysis. There is no conclusive proof that the bacteria represented as the dominant bands detected in the present study are denitrifying-PAOs so far, it should be worthwhile to identify the detected bacteria and to examine their traits as new denitrifying-PAO candidates.     

市政污水生物除磷效能和功能微生物分布特征

调研了4座市政污水处理厂的除磷效能、污泥活性以及微生物分布特征。结果表明出水总磷均达到《城镇污水处理厂污染物排放标准》(GB18918—2002)一级标准,但污泥性能差异显著。活性污泥厌氧释磷率和好氧聚磷率范围分别是0.224～7.77mg/(gVSS.h)和0.386～7.9mg/(gVSS.h)。聚磷假丝酵母菌(Accumulibacter)比例较低,为3.8%～8.7%,聚糖假丝酵母菌(Competibacter)为3.2%～9.1%。进水乙酸含量和乙酸吸收率,厌氧释磷率和好氧聚磷率间都存在很好的线性相关性,表明污水中可利用碳源的数量和磷素的比例极大影响污泥除磷性能。故控制工业废水排入,适当添加碳源,或设置独立的前置反硝化池有望增加污水处理厂的除磷效能。     

Comparison of sequentially combined carbon with sole carbon in denitrification and biological phosphorus removal.

The sequentially combined carbon (SCC) of methanol and acetic acid was used for the biological nutrient removal (BNR). Its BNR performance was compared with methanol or acetic acid as a sole carbon substrate. Compared to the sole carbon substrate, the use of SCC demonstrated the highest overall TIN removal of 98.3% at a COD ratio of 30 mg COD/l of methanol/50 mg CDO/l of acetic acid. Furthermore, denitrification was more enhanced when methanol was used as one of the SCC, rather than as a sole carbon source. Complete phosphorus removal was accomplished with a non-detectable o-P concentration when SCC was added. This research also showed that aerobic denitrifiers appear to prefer acetic acid to methanol, and the amount of poly-beta-hydroxybutyrate (PHB) stored by P accumulating organisms (PAOs) using acetic acid in the anoxic zone could be another important factor in improving the aerobic denitrification. The SCC was a very favorable carbon source for the aerobic denitrification since acetic acid was utilized more efficiently for P-release in accordance with increase of PHB stored in the cell of PAOs by removing nitrogen first using methanol.