低剂量臭氧的直接通加对活性污泥的活性、微生物种群及污泥减量化的影响

研究构建了2个容积为1.1 L的好氧活性污泥反应器（即1号和2号反应器）1,号反应器每天直接通加低剂量臭氧（投加量为0.01 g O3/g TSS）,不加臭氧的2号反应器作为对照平行运行,均采用每天换一次人工污水的充/排式操作。运行71 d的结果表明2,个反应器对人工污水COD的处理效果基本相同。反应器运行40 d后1,号反应器的污泥浓度比2号反应器的污泥浓度低1 400～1 700 mg/L并可稳定在8 200 mg/L,污泥减量化效果明显。低剂量臭氧的直接通加明显降低了胞内ATP浓度,并影响了微生物的抗氧化活性,2号反应器的平均超氧化物歧化酶和过氧化氢酶酶活比1号反应器分别高了24.3%和9.5%。PCR-DGGE对两反应器微生物种群的分析结果表明：Uncultured gammaproteobacteria bacteri-um、Nannocystis exedens和Uncultured actinobacterium为1号反应器的主要种群;而2号反应器的主要种群为Uncultured bacte-rium和Uncultured gammaproteobacteria bacterium。     

Recovery of polyhydroxyalkanoate from activated sludge in an enhanced biological phosphorus removal bench-scale reactor.

A sequencing batch reactor was used to study the possibility of harvesting polyhydroxyalkanoate (PHA) from enhanced biological phosphorus removal (EBPR) processes without compromising treatment quality. Because, in EBPR, the highest PHA concentrations are observed after exposure of the sludge to anaerobic conditions, PHA accumulation was evaluated with collection of waste activated sludge (WAS) at the end of the anaerobic stage, in addition to the traditional removal after the aerobic stage. The system achieved good phosphorus removal, regardless of the point of WAS collection. When sludge was harvested at the end of the anaerobic stage, the PHA content of the sludge ranged from 7 to 16 mg PHA/100 mg mixed liquor volatile suspended solids. Although this level of PHA production is below levels obtained with pure cultures, the demonstrated ability to harvest PHA, while simultaneously satisfying phosphorus removal in an EBPR process, is a key initial step towards of the use of wastewater treatment plants for PHA production.     

Treatment of carbofuran-bearing synthetic wastewater using UASB process

In the present study, fate of carbofuran in anaerobic environments and the adverse effects of carbofuran on conventional anaerobic systems were evaluated. Carbofuran degradation studies were carried out in batch reactors with varying carbofuran concentrations of 0 to 270.73 mg/L corresponding to a sludge-loading rate (SLR) of 2.12 x 10(-6) to 3.83 x 10(-3) g of carbofuran/g of volatile suspended solids (VSS)/d. Carbofuran concentration was reduced to undetectable levels at the end of 8 and 13 days in the batch reactors operated with a SLR of 2.12 x 10(-6) and 3.33 x 10(-5) g of carbofuran/g of VSS/d, respectively. Performances of two anaerobic reactors i.e. upflow anaerobic sludge blanket (UASB) and modified UASB (with tube settlers) were evaluated in the presence and absence of carbofuran using synthetic wastewater. In the absence of carbofuran, the soluble chemical oxygen demand (COD) removal efficiency in the conventional UASB reactor at 8 h and 6 h hydraulic retention time (HRT) was nearly 88% and 76%, respectively, whereas in modified UASB reactor it was increased to 90% at 8 h HRT and 78% at 6 h HRT. When 28 mg/L (SLR of 1.19 x 10(-2) g of carbofuran/g of VSS/d) of carbofuran was introduced in the reactors, the COD removal efficiency was reduced to 41% and 44% in conventional and modified UASB reactors respectively. However, the reactor could maintain around 80% COD removal efficiency at a carbofuran concentration of 7.84 mg/L (SLR of 3.64 x 10(-3) g of carbofuran/g of VSS/d). The reactor efficiency was also measured in terms of specific acetoclastic methanogenic activity (SMA). The toxic effect of carbofuran was reversible to a certain extent. Carbofuran removal efficiency in the conventional UASB reactor at carbofuran concentrations of 7, 13 and 28 mg/L were 40 +/- 3%, 27 +/- 3%, and 11 +/- 3%, respectively. In modified UASB reactor, carbofuran removal efficiency was almost uniform at 7 and 13 mg/L but it was reduced nearly by 56% at 28 mg/L. The major metabolite of carbofuran i.e. 3-keto carbofuran was found in all the reactors.     

Specific resistance to filtration of biomass from membrane bioreactor reactor and activated sludge: effects of exocellular polymeric substances and dispersed microorganisms.

This study investigates the effect of dispersed microorganisms and exocellular polymeric substances on biomass dewaterability. Specific resistance to filtration (SRF) was measured for biomass from a membrane bioreactor and a completely mixed activated sludge system. Both laboratory-scale reactors were fed with synthetic wastewater and operated at a high food-to-microorganism ratio (F/M) (1 to 11 kilograms chemical oxygen demand per kilogram mixed liquor volatile suspended solids per day [kgCOD/(kg MLVSS.d)]) and short solids retention times (0.25 to 5 d). The SRF values were affected by strong interactions of three parameters: (1) the mixed liquor suspended solids concentration, (2) the amount of dispersed microorganisms, and (3) the exocellular polymeric substances (EPS) concentration. At F/M smaller than 2 kg COD/(kg MLSS.d) and mixed liquor suspended solids (MLSS) concentration higher than 2000 mg/L, increasing amount of dispersed microorganisms in the biomass yielded higher SRF values. However, at high F/M (> 5 kg COD/kg MLSS.d) and low MLSS concentrations (< 600 mg/L), lower EPS concentrations resulted in slightly smaller SRF values, even though the amount of dispersed microorganisms in the biomass was much higher. Thus, at low MLSS concentrations, EPS concentrations rather than the amount of dispersed microorganisms tend to control SRF.     

Partition of volatile organic compounds in activated sludge and wastewater

The Henry's law constant is important in the gas-liquid mass transfer process. Apparent dimensionless Henry's law constant, or the gas-liquid partition coefficient (K'H), for both hydrophilic (methanol, isopropyl alcohol, and acetone) and hydrophobic (toluene and p-xylene) organic compounds in deionized (DI) water, a wastewater with a maximum total dissolved organic carbon (DOC) content of 700 mg/L, and DI water mixed with a maximum activated sludge suspended solid (SS) concentration of 40,000 mg/L were measured using the single equilibrium technique at 293 K. Experimental results demonstrate that the K'H of any of the test volatile organic compounds varied among three situations. First, the K'H of the hydrophilic compounds in mixed liquor with the maximum SS concentration was 9-21% higher than those in DI water. Second, those for toluene and p-xylene were 77% and 93% lower, respectively, in the mixed liquor with the maximum SS concentration. Third, the K'H values of all of the test compounds in the wastewater were only 10% lower than those in DI water. A model was developed to relate K'H with wastewater DOC and the SS concentration in the activated sludge using an organic carbon-water partition coefficient and activated sludge-water partition coefficient as model parameters. The model was verified and model parameters for test compounds estimated.     

Oxidation-reduction potential changes in aeration tanks and microprofiles of activated sludge floc in medium- and low-strength wastewaters.

Real-time control of aeration tank operation is key to high-efficiency pollutant removal and energy savings. One of the aims of this study was to examine the potential for using redox potential (oxidation-reduction potential [ORP]) to indicate wastewater quality online in aeration tanks treating medium (chemical oxygen demand [COD] of 70 to 150 mg/L) and low (COD of 15 to 30 mg/L) pollutant-concentration wastewaters. The field-scale data provide a good relationship between ORP values and nutrient removal along the length of the aeration tanks. The ORP values increased dramatically as organic matter was removed along the aeration tanks, indicating the improvement of the bulk liquor redox status. Dissolved oxygen higher than 1.0 mg/L was necessary for good biodegradation and improvement of the liquid redox status. Nitrification occurred at higher ORP values (380 to 420 mV) than was the case for organic substrate oxidation (250 to 300 mV). The microprofiles obtained from microelectrode measurements substantiate the heterogeneity of the microbial processes inside activated sludge flocs. Because of microbial oxygen utilization, the aerobic region in the activated sludge floc was limited to the top layer (0.1 to 0.2 mm) of the activated sludge aggregate present in medium-strength wastewater, with an anoxic zone dominating inside the flocs. When dissolved oxygen in the bulk water was higher than 4.0 mg/L, the anoxic zone inside the floc disappeared. At low wastewater pollutant concentrations, the ORP and dissolved oxygen inside the activated sludge aggregates were higher than those from medium-strength wastewater. The prospect of using ORP as an online control approach for aeration tank operation and the potential reasons for activated sludge floc size varying with pollutant strengths are also discussed.     

Improving nitrogen removal in two modified decentralized wastewater systems

Efficient nutrient removal in decentralized wastewater treatment systems is a challenging task. To improve the removal of organic matter and nitrogen from wastewater, two types of bioreactors using membrane-aerated biofilm reactor (MABR) and microbial fuel cell (MFC) techniques were evaluated. During more than 250 days of continuous-flow reactor operation, both reactors showed consistently high chemical oxygen demand removal (>86%). At an influent ammonium-nitrogen (NH4(+)-N) concentration of 30 mg N/L, the average effluent NH4(+)-N concentrations were 6.2 and 0.5 mg N/L for the MABR and MFC reactor, respectively, while the effluent nitrate-nitrogen (NO3(-)-N) concentrations were 5.4 mg/ L in the MABR and 19.2 mg/L in the MFC-based reactor. The overall total inorganic nitrogen removal efficiencies were 64% and 36% for the MABR and MFC reactor, respectively. At the measured dissolved oxygen concentrations of 5.2 and 0.23 mg/L in the aerobic/anoxic zone of the MFC and MABR, respectively, a specific oxygen uptake rate of 0.1 g O2/g VSS-d, resulting from ammonia oxidation, was detected in the settled sludge of the MFC, while no nitrifying activity of the sludge from the MABR was detected. Molecular microbial analysis demonstrated a link between the bacterial community structure and nitrifying activity. The relatively high abundance of Nitrosomonas europaea was associated with its detectable nitrification activity in the settled sludge of the MFC. The results suggest that MABR and MFC techniques have the potential to improve organic and nitrogen removal in decentralized wastewater systems.     

Activated sludge deflocculation in response to chlorine addition: the potassium connection.

Chlorination is often used to control filamentous bulking in activated sludge systems. Pure culture and mixed-liquor experiments showed that soluble potassium (K+) concentrations increased by 2.4 mg/L (80%) and 1.5 to 3.6 mg/L (11 to 30%) in the bulk liquid phase of pure and activated sludge cultures that were exposed to chlorine, relative to unchlorinated controls. Effluent turbidity and total suspended solids from settled mixed liquor increased significantly in both short-term batch and sequencing batch reactor experiments when chlorine mass load increased above 6 milligrams of chlorine per gram mixed liquor volatile suspended solids (mg Cl2/g MLVSS) in a single dose, which correlated with a localized chlorine concentration at the dose point of 10 mg/L as Cl2 or greater. The results support the hypothesis that the glutathione-gated potassium efflux (GGKE) bacterial stress response may contribute to increased effluent turbidity associated with high doses of mixed-liquor chlorination. It is suggested that potassium is a useful parameter to monitor at full-scale facilities when determining chlorine mass doses that should be used to control filaments and minimize increases in effluent turbidity.     

Effect of operational parameters on the removal of particulate chemical oxygen demand in the activated sludge process.

The removal of particulate material in the aeration basin of the activated sludge process is mainly attributed to bioflocculation and hydrolysis of particulate substrate. The bioflocculation process in the aeration tank of the activated sludge process occurs only under favorable conditions in the system, and several common operational parameters affect its performance. The principal objective of this research was to observe the effect of mixed liquor suspended solids, solids retention time (SRT), and extracellular polymer substances on the removal of particulate substrate by bioflocculation. A first-order particulate removal expression, based on flocculation, accurately described the removal rates for supernatant suspended solids and colloidal chemical oxygen demand. Based on the results presented in this investigation, a mixed liquor concentration of approximately 2200 mg/L, an SRT of at least 3 days, and a contact time of 30 minutes are needed for relatively complete removal of the particulate substrate in a plug-flow reactor.     

Ca2+对上流式多级厌氧反应器处理蔗渣渗滤液的影响

研究了上流式多级厌氧反应器(UMAR)处理蔗渣渗滤液过程中Ca2+浓度对反应器运行特性和颗粒污泥性质的影响。结果表明,对于蔗渣渗滤液而言,进水中低浓度的Ca2+浓度(80～300 mg/L)对颗粒污泥产甲烷活性无抑制,COD去除率最高可达93.3%;Ca2+浓度达到500 mg/L以上时,对厌氧颗粒污泥的活性有抑制作用;随着Ca2+浓度进一步升高,抑制作用加强,污泥灰分明显升高,活性成分下降,COD去除效率明显降低,污泥粘结沉积在反应器底部,导致系统内循环出现障碍。因此,在实际生产中应减少废水中Ca2+的引入量。     

高效代谢解偶联剂的筛选及对SBR系统综合运行效能的影响

活性污泥法是最常用的污水处理技术,但它同时会产生大量的剩余污泥,需要进行额外的处理和处置.活性污泥的解偶联代谢能有效地减少剩余污泥的产量.比较了5种代谢解偶联剂,即2,4-二硝基苯酚(DNP)、邻氨基苯酚(AP)、2,4,6-三氯苯酚(TCP)、3,3',4,5-四氯水杨酰苯胺(TCS)、丙二酸的污泥减量效果和对COD去除能力的影响.结果表明,当它们在各自的最佳质量浓度20、1 5、4、1.2、15 mg/L时,污泥的表观增长系数分别降低了62.39%、63.75%、59.40%、34.58%和53.75%,而COD去除率仅有轻微下降.重点研究了15 mg/L的丙二酸和4 mg/L的TCP对SBR系统运行效能和污泥沉降性能的影响.发现在长期运行过程中,两者都能有效降低系统的污泥产量,而对COD去除率的影响较低,但使用丙二酸6 d后极大地影响了污泥的沉降性能,而TCP对污泥的沉降性能影响很小.     

Identifying different types of bulking in an activated sludge system through quantitative image analysis

The present study proposes an image analysis methodology for the identification of different types of disturbances in wastewater treatment activated sludge systems. Up to date, most reported image analysis methodologies have been used in activated sludge processes with the aim of filamentous bulking detection, however, other disturbances could be foreseen in wastewater treatment plants. Such disturbances can lead to fluctuations in the biomass contents, affecting the mixed liquor suspended solids (MLSS), and in the sludge settling ability, affecting the sludge volume index (SVI). Therefore, this work focuses on predicting the MLSS and SVI parameters for different types of disturbances affecting an activated sludge system. Four experiments were conducted simulating filamentous bulking, zoogleal or viscous bulking, pinpoint floc formation, and normal operating conditions. Alongside the MLSS and SVI determination, the aggregated and filamentous biomass contents and morphology were studied as well as the biomass Gram and viability status, by means of image analysis.     

Hybrid process for heavy metal removal from wastewater sludge.

Bioleaching processes have been demonstrated to be effective technologies in removing heavy metals from wastewater sludge, but long hydraulic retention times are typically required to operate these bioprocesses. A hybrid process (coupling biological and chemical processes) has been explored in laboratory pilot-scale experiments for heavy metals (cadmium [Cd], copper [Cu], chromium [Cr], and zinc [Zn]) removal from three types of sludge (primary sludge, secondary activated sludge, and a mixture of primary and secondary sludge). The hybrid process consisted of producing a concentrate ferric ion solution followed by chemical treatment of sludges. Ferric iron solution was produced biologically via oxidation of ferrous iron by A. ferrooxidans in a continuous-flow stirred tank (5.2 L) reactor (CSTR). Wastewater sludge filtrate (WSF) containing nutrients (phosphorus and nitrogen) has been used as culture media to support the growth and activity of indigenous iron-oxidizing bacteria. Results showed that total organic carbon (TOC) concentrations of the culture media in excess of 235 mg/L were found to be inhibitory to bacterial growth. The oxidation rate increased as ferrous iron concentrations ranged from 10 to 40 g Fe2+/L. The percentage of ferrous iron (Fe2+) oxidized to ferric iron (Fe3+) increased as the hydraulic retention time (HRT) increased from 12 to 48 h. Successful and complete Fe2+ oxidation was recorded at a HRT of 48 h using 10 g Fe2+/L. Subsequently, ferric ion solution produced by A. ferrooxidans in sludge filtrate was used to solubilize heavy metals contained in wastewater sludge. The best solubilization was obtained with a mixture of primary and secondary sludge, demonstrating a removal efficiency of 63, 71, 49, and 80% for Cd, Cu, Cr, and Zn, respectively.     

固定化菌藻系统对污水处理厂出水的深度处理

将海藻酸钠固定化活性污泥和小球藻制成颗粒小球,以自制的流化床反应器对重庆市某污水处理厂出水进行深度处理,探讨了系统对氨氮、TP、COD的去除效果,实验结果表明:在HRT=12 h,溶解氧浓度为3.0 mg/L左右,pH值为6.2至8.0之间,环境室温条件下,系统对氨氮、TP、COD均有较好的去除效果,系统稳定运行后对氨氮、TP、COD去除率基本维持在60%、60%和30%以上,出水氨氮、TP、COD浓度基本维持在8、0.5和40 mg/L以下,出水浓度达到了《城镇污水处理厂污染物排放标准》(GB 18918-2002)的一级A标准。这项研究显示固定化菌藻胶球系统在污水处理厂出水的深度处理中具有潜在的应用前景。     

Synthesis of polyhydroxyalkanoates in municipal wastewater treatment.

Biologically derived polyesters known as polyhydroxyalkanoates (PHAs) represent a potentially "sustainable" replacement to fossil-fuel-based thermoplastics. However, current commercial practices that produce PHA with pure microbial cultures grown on renewable, but refined, feedstocks (i.e., glucose) under sterile conditions do not represent a sustainable commodity. Here, we report on PHA production with a mixed microbial consortium indigenous to an activated sludge process on carbon present in municipal wastewaters. Reactors operated under anaerobic/aerobic and aerobic-only mode and fed primary solids fermenter liquor maintained a mixed microbial consortium capable of synthesizing PHA at 10 to 25% (w/w), while reducing soluble COD by approximately 62 to 71%. More critically, an aerobic batch reactor seeded from the anaerobic/aerobic reactor and fed fermenter liquor achieved approximately 53% PHA (w/w). Results presented suggest that environmentally benign production of biodegradable polymers is feasible. We further used PHA-rich biomass to produce a natural fiber-reinforced thermoplastic composite that can be used to offset advanced wastewater treatment costs.     

Hydraulic residence time effects on performance of an activated sludge unit treating wastewater containing dichlorophenol.

Wastewaters containing chlorophenol compounds are difficult to treat by biological means because of the toxic effects of those compounds on microorganisms. To investigate the adverse effects of chlorophenols on microorganisms, synthetic wastewater containing 2,4 dichlorophenol (DCP) was biologically treated in an activated sludge unit at different hydraulic residence times (HRTs) between 5 and 40 hours, whereas the feed chemical oxygen demand (COD), DCP concentrations, and sludge age were kept constant at 2500 +/- 50 mg/L, 150 mg/L, and 20 days, respectively. The resazurin method based on dehydrogenase activity was used for assessment of the feed and effluent wastewater toxicity. Percent COD, DCP, and toxicity removals increased, and the effluent COD, DCP, and toxicity levels decreased with increasing HRT. Biomass concentration in the aeration tank increased with increasing HRT because of low levels of DCP at high HRT levels, resulting in high COD, DCP, and toxicity removals. The sludge volume index decreased with increasing HRT, yielding well-settling organisms as a result of low levels of toxicity and high concentrations of active cells. Percent DCP and COD removals decreased with increasing specific DCP loading rate. The rates of DCP and COD removals showed a maximum at a low DCP concentration of 6 mg/L in the aeration tank, corresponding to a 25-hour HRT.     

SBR处理高浓度养猪废水工艺条件

以养猪场废水作为研究对象,采用序列间歇式活性污泥法SBR,通过实验研究了供气量、pH、排泥量、原水稀释倍数、水力停留时间（HRT）对SBR出水水质的影响。结果表明,供气量为375 L/（min·m³）、pH为8.0,并添加排泥100 mL的操作,可使SBR处理效果明显提高,COD、磷和凯氏氮去除率最高分别可达96.37%、94.14%、99.38%。逐步降低进水稀释倍数有利于培养出处理高浓度有机养猪废水的活性污泥,可将平均COD、磷和凯氏氮含量高达9 161.24、33.41和1 502.77 mg/L的养猪废水处理至出水的490.11、5.35和17.84 mg/L。降低HRT对SBR去除率影响不大。     

废水中KMnO4对生物处理效果的影响

为减轻和消除含高浓度KMnO4的牛仔服加工废水对生物处理系统的毒害作用,采用模拟序批式活性污泥法,研究KMnO4对活性污泥微生物生长的影响及COD和NH4+-N的降解规律。结果表明,当处理进水COD浓度500 mg/L,NH4+-N浓度23.5 mg/L,污泥浓度为2 000 mg/L时,曝气时间为4 h,KMnO4质量浓度增加对COD和NH4+-N的降解影响很大;同样条件下曝气时间改为8 h,对NH4+-N的降解影响显著减小,但对COD的降解影响减少不多;并且,高浓度KMnO4对NH4+-N去除效果的抑制作用比对COD的大。因此,处理含高浓度KMnO4的废水需要延长一倍曝气时间,可以获得良好的COD和NH4+-N的降解效果。同时,KMnO4对活性污泥的抑制影响较好地吻合非竞争性抑制机理修正莫若特方程的规律。     

清洁型一体化污水处理系统研究

针对城镇分散型污水处理的特点,开发了一种清洁型一体化污水处理系统.该系统由立体循环一体化氧化沟(IODVC)、污泥减量区和臭气处理区优化整合而成.中试试验结果表明:该系统可以使微生物有效处理污水,并实现污泥减量和臭味气体净化.经该系统处理的污水,出水COD、NH4 -N、SS的浓度维持在35 mg/L、1 mg/L和20 mg/L以下;同时,臭味气体得到有效去除,氨气和硫化氢等臭味气体可以达标排放;经过生物减量,排放的剩余污泥减少了46.4%;污泥的比阻有所降低.本系统占地少,运行操作简便,无二次污染,属于适合中小型污水处理的技术工艺.     

Partition of Volatile Organic Compounds in Activated Sludge and Wastewater

Abstract

The Henry’s law constant is important in the gas-liquid mass transfer process. Apparent dimensionless Henry’s law constant, or the gas-liquid partition coefficient (K’ _H), for both hydrophilic (methanol, isopropyl alcohol, and acetone) and hydrophobic (toluene and p-xylene) organic compounds in deionized (DI) water, a wastewater with a maximum total dissolved organic carbon (DOC) content of 700 mg/L, and DI water mixed with a maximum activated sludge suspended solid (SS) concentration of 40,000 mg/L were measured using the single equilibrium technique at 293 K.

Experimental results demonstrate that the K’ _H of any of the test volatile organic compounds varied among three situations. First, the K’_H of the hydrophilic compounds in mixed liquor with the maximum SS concentration was 9–21% higher than those in DI water. Second, those for toluene and p-xylene were 77% and 93% lower, respectively, in the mixed liquor with the maximum SS concentration. Third, the K’_H values of all of the test compounds in the wastewater were only 10% lower than those in DI water.

A model was developed to relate K’ _H with wastewater DOC and the SS concentration in the activated sludge using an organic carbon-water partition coefficient and activated sludge-water partition coefficient as model parameters. The model was verified and model parameters for test compounds estimated.