Start-up of autotrophic nitrogen removal reactors via sequential biocatalyst addition

A procedure for start-up of oxygen-limited autotrophic nitrification-denitrification (OLAND) in a lab-scale rotating biological contactor (RBC) is presented. In this one-step process, NH4+ is directly converted to N2 without the need for an organic carbon source. The approach is based on a sequential addition of two types of easily available biocatalyst to the reactor during start-up: aerobic nitrifying and anaerobic, granular methanogenic sludge. The first is added as a source of aerobic ammonia-oxidizing bacteria (AAOB), the second as a possible source of planctomycetes including anaerobic ammonia-oxidizing bacteria (AnAOB). The initial nitrifying biofilm serves as a matrix for anaerobic cell incorporation. By subsequently imposing oxygen limitation, one can create an optimal environment for autotrophic N removal. In this way, N removal of about 250 mg of N L(-1) d(-1) was achieved after 100 d treating a synthetic NH4+-rich wastewater. By gradually imposing higher loads on the reactor, the N elimination could be increased to about 1.8 g of N L(-1) d(-1) at 250 d. The resulting microbial community was compared with that of the inocula using general bacterial and AAOB- and planctomycete-specific PCR primers. Subsequently, the RBC reactor was shown to treat a sludge digestor effluent under suboptimal and strongly varying conditions. The RBC biocatalyst was also submitted to complete absence of oxygen in a fixed-film bioreactor (FFBR) and proved able to remove NH4+ with NO2- as electron acceptor (maximal 434 mg of NH4+-N (g of VSS)(-1) d(-1) on day 136). DGGE and real-time PCR analysis demonstrated that the RBC biofilm was dominated by members of the genus Nitrosomonas and close relatives of Kuenenia stuttgartiensis, a known AnAOB. The latter was enriched during FFBR operation, but AAOB were still present and the ratio planctomycetes/AAOB rRNA gene copies was about 4.3 after 136 d of reactor operation. Whether this relates to an active role of AAOB in the anoxic N removal process remains to be solved.     

Characterization of efficient aerobic denitrifiers isolated from two different sequencing batch reactors by 16S-rRNA analysis

By adopting two sequencing batch reactors (SBRs) A and B, nitrate as the substrate, and the intermittent aeration mode, activated sludge was domesticated to enrich aerobic denitrifiers. The pHs of reactor A were approximately 6.3 at DOs 2.2-6.1 mg/l for a carbon source of 720 mg/l COD; the pHs of reactor B were 6.8-7.8 at DOs 2.2-3.0 mg/l for a carbon source of 1500 mg/l COD. Both reactors maintained an influent nitrate concentration of 80 mg/l NO3- -N. When the total inorganic nitrogen (TIN) removal efficiency of both reactors reached 60%, aerobic denitrifier accumulation was regarded completed. By bromthymol blue (BTB) medium, 20 bacteria were isolated from the two SBRs and DNA samples of 8 of these 20 strains were amplified by PCR and processed for 16SrRNA sequencing. The obtained results were analysed by a Blast similarity search of the GenBank database, and constructing a phylogenetic tree for identification by comparison. The 8 bacteria were found to belong to the genera Pseudomonas, Delftia, Herbaspirillum and Comamonas. At present, no Delftia has been reported to be an aerobic denitrifier.     

Hydrogen sulfide oxidation by a microbial consortium in a recirculation reactor system: sulfur formation under oxygen limitation and removal of phenols

Wastewater from petroleum refining may contain a number of undesirable contaminants including sulfides, phenolic compounds, and ammonia. The concentrations of these compounds must be reduced to acceptable levels before discharge. Sulfur formation and the effect of selected phenolic compounds on the sulfide oxidation were studied in autotrophic aerobic cultures. A recirculation reactor system was implemented to improve the elemental sulfur recovery. The relation between oxygen and sulfide was determined calculating the O2/S2- loading rates (Q(O2)/Q(S)2- = Rmt), which adequately defined the operation conditions to control the sulfide oxidation. Sulfur-producing steady states were achieved at Rmt ranging from 0.5 to 1.5. The maximum sulfur formation occurred at Rmt of 0.5 where 85% of the total sulfur added to the reactor as sulfide was transformed to elemental sulfur and 90% of it was recovered from the bottom of the reactor. Sulfide was completely oxidized to sulfate (Rmt of 2) in a stirred tank reactor, even when a mixture of phenolic compounds was present in the medium. Microcosm experiments showed that carbon dioxide production increased in the presence of the phenols, suggesting that these compounds were oxidized and that they may have been used as carbon and energy source by heterotrophic microorganisms present in the consortium.     

Long-term effects of titanium dioxide nanoparticles on nitrogen and phosphorus removal from wastewater and bacterial community shift in activated sludge

The expanding use of titanium dioxide nanoparticles (TiO(2) NPs) in a wide range of fields raises concerns about their potential environmental impacts. However, investigations of the potential effects of TiO(2) NPs on biological nitrogen and phosphorus removal and bacterial community in activated sludge are sparse. This study evaluated the influences of TiO(2) NPs on biological nutrient removal in the anaerobic-low dissolved oxygen (0.15-0.50 mg/L) sequencing batch reactor. It was found that 1 and 50 mg/L TiO(2) NPs had no acute effects on wastewater nitrogen and phosphorus removal after short-term exposure (1 day). However, 50 mg/L TiO(2) NPs (higher than its environmentally relevant concentration) was observed to significantly decrease total nitrogen (TN) removal efficiency from 80.3% to 24.4% after long-term exposure (70 days), whereas biological phosphorus removal was unaffected. Denaturing gradient gel electrophoresis profiles showed that 50 mg/L TiO(2) NPs obviously reduced the diversity of microbial community in activated sludge, and fluorescence in situ hybridization analysis indicated that the abundance of nitrifying bacteria, especially ammonia-oxidizing bacteria, was highly decreased after long-term exposure to 50 mg/L TiO(2) NPs, which was the main reason for the serious deterioration of ammonia oxidation. Further study revealed that 50 mg/L TiO(2) NPs inhibited the activities of ammonia monooxygenase and nitrite oxidoreductase after long-term exposure, but had no significant impacts on the activities of exopolyphosphatase and polyphosphate kinase, and the transformations of intracellular polyhydroxyalkanoates and glycogen, which were consistent with the observed influences of TiO(2) NPs on biological nitrogen and phosphorus removal.     

多孔载体生物膜反应器深度处理皮革废水的试验研究

本试验采用自制多孔载体生物膜反应器对某皮革厂经物化、生化处理后的出水进行深度处理。研究结果表明:在水中溶解氧DO为2.0~3.0 mg/L,水力停留时间HRT为8 h,进水COD为176.5~256.6 mg/L、氨氮为39.2~58.9 mg/L、总氮为51.9~76.5 mg/L的条件下,经过本反应器处理之后的出水平均COD为75.8 mg/L,平均氨氮质量浓度为8.8 mg/L,平均总氮质量浓度为22.9 mg/L,出水水质达到《污水综合排放标准》(GB8978-1996)中的一级排放标准。     

Experimental studies of the influence of grain size, oxygen availability and organic carbon availability on bioclogging in porous media

Changes in the hydraulic properties of porous material due to bioclogging have been observed in many laboratory simulations and field studies. Because such changes in hydraulic properties influence the movement of fluids and contaminants, microbial ecology data are required for improved transport modeling. Here we investigate the effects of environmental variables previously shown to influence bioclogging, specifically oxygen availability, sediment grain size, and organic carbon (nutrient) concentration on the hydraulic properties of simulated subsurface environments. Our study provides evidence of a different clogging mechanism for aerobic and anaerobic microbial communities under high organic carbon concentrations (400 mg L(-1)). This work also suggests that the clogging mechanism operating in anaerobic microbial communities is more sensitive to carbon availability than that in the aerobic microbial communities. We found that grain size does have an effect on clogging, but it appears that there is a threshold carbon concentration, and therefore biomass, below which these effects are insignificant. Differences between the microbial communities that developed under different oxygenation conditions were detected using 16s rRNA analysis.     

SBR法对缫丝废水的后续处理试验研究

通过研究影响序批式活性污泥法(SBR法)对缫丝废水的后续处理效果的各种因素,得出最佳工况运行条件。结果表明,在SBR法中,曝气时间为8 h,沉淀时间为40 min,溶解氧值为2～3 mg/L时,系统处理效果最好,COD、氨氮和TP的去除率分别达到90.5%±0.5%、95.1%±0.6%和78.2%±3.1%,出水的COD和氨氮都能达标排放。将SBR反应器作为缫丝废水后续好氧处理工艺,具有较高的处理效率和较好的运行稳定性。     

螺旋藻混合营养培养中碳源分析

对螺旋藻混合营养培养过程中无机碳HCO3-和有机碳源葡萄糖进行详细的检测及分析,结果表明:在培养3d时各组所添加的葡萄糖基本用完,培养9d时,葡萄糖浓度为3.0g/L组培养液HCO3-含量最低.同时优选了螺旋藻混合营养培养的NaHCO3添加量,研究发现NaHCO3含量对螺旋藻混合营养细胞积累有很大的影响,NaHCO3的浓度在8.4g/L～16.8g/L时基本对螺旋藻生物量的积累没有太大的影响.     

Effects of dietary sodium bicarbonate and calcium chloride on physiological responses of lactating dairy cows in hot weather

Twenty-four lactating cows were assigned randomly to three treatments to evaluate responses to large differences of dietary sodium and chloride. Treatments were corn-cottonseed meal-corn silage based complete rations with either: 1) .23% sodium chloride (control), 2) control plus 2.28% calcium chloride, or 3) control plus 1.70% sodium bicarbonate. Treatment effects were significant for urine pH (7.96, 5.41, 8.18), blood pH (7.50, 7.39, 7.49), partial pressure of oxygen (91.2, 99.4, 86.3 mm Hg), partial pressure of carbon dioxide (34.60, 30.57, 32.98 mm Hg), bicarbonate (26.20, 18.06, 24.64 meq/liter), total carbon dioxide (27.51, 19.18, 25.88 mM/liter), base excess (4.50, -4.31, 3.13 meq/liter), plasma chloride (93.4, 102.8, 95.7 meq/liter), serum potassium (3.26, 4.24, 4.14 meq/liter), and inorganic phosphorus (7.11, 5.61, 6.80 mg/100 ml). Blood glucose (45.1, 43.0, 55.5 mg/dl) and blood urea nitrogen (11.8, 8.7, 11.9 mg/dl) exhibited treatment effects. Respiration rates, 84.8, 61.8, 89.9 per min, and body temperatures, 39.7, 39.0, and 40.0 degrees C were significantly different. Lower intake of the high chloride diet and higher intake of the bicarbonate diet were probably responsible for some of the effects. Dietary electrolytes should receive attention in formulation because acid-base status of the animal is determined, in part, by ionic concentration and balance of the diet.     

运用序列式生物膜反应器处理味精污水工艺研究

味精污水中含有较高的氨氮离子,序列式生物膜反应器(SBBR)能够有效实现味精污水的同步硝化与反硝化反应,减少设备占有面积和节约处理时间。经过实验得出,当溶氧(DO)为3~4mg/L能够有效地满足生物膜中好氧菌的生长需要,又不会破坏生物膜内的厌氧环境,当pH值为8.0时,温度为30℃时,对味精生产中产生的污水的化学需氧量(COD)去除率高达95.34%,氨氮的去除率达到95.78%,生物需氧量(BOD5)去除率94.1%。     

A^2/O+MBBR集成工艺处理印染废水

简要介绍印染废水的水质特点及改良传统活性污泥法(A2/O)+移动床生物膜反应(MBBR)工艺集成技术;重点介绍A2/O+MBBR工艺处理印染污水的运行效果。结果显示,在进水量20~60 L/h,溶解氧(DO)质量浓度1.5~4.5 mg/L,污泥回流比50%~90%,硝化液回流比250%~350%,好氧池污泥质量浓度(MLSS)2.0~3.5 g/L,好氧池悬浮填料装填比25%(体积比)的操作条件下连续稳定运行200天后,出水COD去除效果、氨氮去除效果、总磷去除效果、总氮去除效果远远优于《城镇污水处理厂污染物排放标准》的一级A标准。     

4-nitrophenol biodegradation in a sequencing batch reactor operating with aerobic-anoxic cycles

The study regards 4-nitrophenol removal performed in a lab-scale sequential batch reactor with an integrated aerobic-anoxic cycle. The purpose of the study was to examine the kinetics of 4-nitrophenol biological oxidation and denitrification in order to test the feasibility of the proposed technological solution for xenobiotic removal. The results obtained show that high removal efficiency of 4-nitrophenol is easily achieved when the compound is fed into the reactor as the sole carbon source. Residual concentrations of 4-nitrophenol and nitrous/nitric nitrogen in the effluent lower than 1 mg L(-1) were observed in the range of applied feed concentration (200-320 mg L(-1)). Low concentrations of dissolved oxygen (< or =2 mg L(-1)) in the feed and aerobic phases lead to appreciable simultaneous denitrification. As regards the denitrification process, while no carbon-limiting effects were observed at COD/N ratios > or = 3, a significant decrease in the rate of denitrification is detected for COD/N ratios < or = 2. The denitrification rate obtained in tests with no external carbon addition proved very low and unsuitable for practical application. A model of the denitrification process taking into account both the limiting effect of nitrogen and carbonaceous substrate has been proposed and applied for experimental data correlation.     

Mechanism and kinetics of the catalytic oxidation of aqueous ammonia to molecular nitrogen

Aqueous phase catalytic oxidation of ammonia has been studied over Ru/TiO2 catalyst in a batch reactor by changing the solution pH, concentration of catalyst in the solution, temperature, and reaction time. The oxidation reaction of ammonia over Ru/TiO2 catalyst has been found to take place exclusively for the aqueous NH3 with a preferred mode in strong alkaline pH region. An oxidation reaction pathway has been proposed as follows: Oxidation of ammonia is initiated by the reaction of aqueous ammonia with catalytically activated oxygen. After undergoing further successive oxidation reactions with activated oxygen, ammonia is finally oxidized to a molecule of nitrous acid. Nitrous acid dissociates into a nitrite ion and a proton. The solution pH is decreased with the protons from the dissociation of HNO2 so that the solution concentration of NH4+ is increased. Molecular nitrogen as a final product is produced from the homogeneous aqueous phase reaction between nitrous ion and ammonium ion. Further reaction of nitrous ion with the activated oxygen leads to the formation of nitrate ion. The reaction pathway proposed has been validated with the changes of solution pH along with the ammonia conversions, and the formation of N2 from the solution containing NO2- and NH4+ ions in equimolar amounts of nitrogen has been confirmed in a separate experiment. The kinetics of aqueous ammonia oxidation reaction has been well represented as a first-order reaction with respect to the concentration of aqueous ammonia, and an apparent rate constant has been obtained as a function of catalyst concentration in solution, oxygen pressure, and reaction temperature.     

Development of chitosan-magnetite aggregates containing Nitrosomonas europaea cells for nitrification enhancement

A cell suspension of the nitrifying bacterium Nitrosomonas europaea obtained after 96-h cultivation was subjected to magnetic separation using chitosan-conjugated magnetite particles (chitosan-magnetite), which have the ability to form aggregates with microbial cells. An equilibrium condition was obtained at room temperature after 30 min and over 90% of the cells were recovered when the chitosan-magnetite concentration was 200 mg/l. The relationship between the cell concentration in the supernatant in equilibrium and the number of cells adsorbed per 1g chitosan-magnetite was expressed by a Freundlich-type adsorption equation. A high nitrifying bacterium activity yield was obtained with a chitosan-magnetite concentration between 100 and 200 mg/l. Repeated batch culture resulted in more N. europaea cells accumulating on the aggregates and as a consequence their nitrification activity improved further. The chitosan-magnetite/cell aggregates were recovered and employed to remove ammonia from artificial wastewater together with PVA-alginate gel beads containing the denitrifying bacterium Paracoccus denitrificans. A higher ammonia removal rate was achieved under aerobic conditions in comparison with that obtained when N. europaea and P. denitrificans were coimmobilized in PVA-alginate gel beads.     

基于高分子载体与活性炭对比处理白酒废水的研究

实验以高分子材料做载体,与多孔颗粒活性炭(GAC)在完全相同的条件下,作厌氧流化床固定化微生物处理白酒废水的对比性研究.6d后加入已经分离出来的高效厌氧微生物,结果表明,新型高分子载体能有效促进厌氧菌固定化,可比GAC缩短反应器启动时间12d左右;且在进水COD值为3957.4mg/L、pH值为7.30、膨胀率为50%、水力停留时间为9h的条件下,COD的云除率为90.5%.     

Characterization study and five-cycle tests in a fixed-bed reactor of titania-supported nickel oxide as oxygen carriers for the chemical-looping combustion of methane

Recent investigations have shown that in the combustion of carbonaceous compounds CO2 and NOx emissions to the atmosphere can be substantially reduced by using a two stage chemical-looping process. In this process, the reduction stage is undertaken in a first reactor in which the framework oxygen of a reducible inorganic oxide is used, instead of the usual atmospheric oxygen, for the combustion of a carbonaceous compound, for instance, methane. The outlet gas from this reactor is mostly composed of CO2 and steam as reaction products and further separation of these two components can be carried out easily by simple condensation of steam. Then, the oxygen carrier found in a reduced state is transported to a second reactor in which carrier regeneration with air takes place at relatively low temperatures, consequently preventing the formation of thermal NOx. Afterward, the regenerated carrier is carried to the first reactor to reinitiate a new cycle and so on for a number of repetitive cycles, while the carrier is able to withstand the severe chemical and thermal stresses involved in every cycle. In this paper, the performance of titania-supported nickel oxides has been investigated in a fixed-bed reactor as oxygen carriers for chemical-looping combustion of methane. Samples with different nickel oxide contents were prepared by successive incipient wet impregnations, and their performance as oxygen carriers was investigated at 900 degrees C and atmospheric pressure in five-cycle fixed-bed reactor tests using pure methane and pure air for the respective reduction and regeneration stages. The evolution of the outlet gas composition in each stage was followed by gas chromatography, and the involved chemical, structural, and textural changes of the carrier in the reactor bed were studied by using different characterization techniques. From the study, it is deduced that the reactivity of these nickel-based oxygen carriers is in the two involved stages and almost independent of the nickel loading. However, in the reduction stage, carbon deposition, from the thermal decomposition of methane, and CO emissions, mainly derived from the partial reduction of titania as support acting as an additional oxygen source, may impose some constraints to the efficiency of the overall chemical-looping combustion process in CO2 capture.     

好氧移动床生物膜反应器挂膜启动过程

采用移动床生物膜反应器处理生活污水，考察了接种污泥质量浓度对挂膜启动过程的影响，同时对启动过程中微生物相的变化、悬浮污泥的影响进行了初步分析。结果表明：在不添加接种污泥的条件下，反应器能够在两周内完成挂膜启动，载体上附着微生物生长稳定时挥发性悬浮污泥（VSS）质量浓度达1．2g／L；栽体上微生物的附着生长主要可分为3个阶段：适应期、增长期以及稳定期，不同阶段微生物相的种群分布不同，各有其特征微生物存在；反应器在挂膜启动过程中，接种所需的临界活性污泥质量浓度在0．1g／L以下。     

PROPERTIES OF FRANKFURTERS PROCESSED WITH POTASSIUM AND SODIUM BICARBONATE

A study was designed to evaluate the use of low levels of sodium (0.25, 0.5, 1%) and potassium (0.25, 0.5%) bicarbonate on the sensory, microbial and functional properties of frankfurters. Both sodium and potassium bicarbonate resulted in higher pH values than control (no bicarbonate) on day 0 but differences diminished after storage at 4°C for 22 days. At the 0.5% level of addition, both sodium and potassium bicarbonate treatments had lower percent free water when compared to controls. The addition of high levels of bicarbonate resulted in diminished sensory properties; however, low levels had sensory characteristics in the acceptable range. No differences were detected between treatments for aerobic plate counts, anaerobic plate counts or yeast and mold counts. Results indicate an acceptable product can be produced using low levels of either sodium or potassium bicarbonate. The use of low levels of bicarbonate also results in beneficial changes of some physical properties.     

Microbial ecology of nitrifying bacteria in wastewater treatment process examined by fluorescence in situ hybridization

The microbial ecology of nitrifying bacteria in various types of wastewater treatment processes and the dynamic response of the microbial ecology in biofilms were investigated using fluorescence in situ hybridization (FISH) with 16S rRNA-targeted oligonucleotide probes. Nitrifying bacteria were found to exhibit various organizational forms under different conditions of substrate composition and concentration. Ammonia-oxidizing bacteria were dominant in ammonia-rich inorganic wastewater, while heterotrophic bacteria and ammonia-oxidizing bacteria were localized at different positions in the biofilm in organic wastewater. The dynamics of the microbial ecology in the biofilm with regard to the spatial distribution of ammonia-oxidizing bacteria and heterotrophic bacteria caused by a gradual change in substrate composition was successfully monitored by FISH analysis.     

Enhanced microbial adaptation to p-nitrophenol using activated sludge retained in porous carrier particles and simultaneous removal of nitrite released from degradation of p-nitrophenol

In order to examine the microbial degradation of p-nitrophenol (PNP) by a mixed culture system and simultaneous removal of nitrite released via the degradation, an activated sludge retained in porous carrier particles and a suspension culture as a control were acclimated to artificial sewage containing PNP as the sole carbon source. The adaptation of microbes retained in porous carrier particles to PNP was faster than that of suspended microbes by more than 20 d. After microbial adaptation to PNP, it was degraded completely without significant accumulation of intermediate metabolites. The PNP degradation activity of the retained microbes was more than 2 times higher than that of the suspended microbes. By increasing the retained microbial concentration, nitrite released from the degraded PNP was removed by denitrification. This research demonstrates that using microbes retained in porous carrier particles is not only effective for reduction of acclimation time but also enables simultaneous removal of the nitrogen compounds resulting from the degradation of nitroaromatics.