Performance and Microbial Community of Simultaneous Denitrification and Biomineralization in Bioreactors

The effects of combined different strains on a simultaneous denitrification and biomineralization process were examined. The influence of sodium succinate concentration, pH, and hydraulic retention time on nitrate and hardness removal was evaluated in bioreactors. Experimental results indicated that high nitrate and hardness removal efficiencies were obtained under optimum conditions. The community diversity was markedly influenced by the concentration of sodium succinate. The findings proved that Pseudomonas sp. H117 and Pseudomonas sp. H2 played a key role in the process of nitrate and hardness removal. The main component of sedimentation generated from the bioreactor was detected as calcium ion precipitation by scanning electron microscopy and X‐ray diffraction.     

Ionic Competition Effects in a Continuous Uranium Biosorptive Recovery Process

Immobilized Rhizopus arrhizus biomass was studied in a continuous sorption and desorption mode in order to identify factors that affect the long term uranium biosorptive uptake capacity performance of the immobilized biomass. Laboratory-scale continuous operation pilot plant experiments were performed using synthetic uranyl nitrate and industrial uranium mine leachate solutions. Analysis of the liquid solutions indicated that the immobilized Rhizopus arrhizus biomass successfully recovered all of the uranium from the dilute (less than 500 mg U dm⁻³) solutions. All uranium can subsequently be eluted, yielding highly concentrated uranium eluates. The immobilized Rhizopus arrhizus biomass maintained its uranium biosorptive uptake capacity over 12 successive sorption–elution cycles when synthetic uranyl nitrate solutions were used. However, when used with mine leachate solutions, an 18% reduction in the uranium biosorptive uptake capacity occurred within the first four adsorption–elution cycles. Spectral analysis indicated that, during continuous use and reuse, the immobilized biomass retained its structural integrity. EDAX, scanning and transmission electron microscopic techniques employed on the microbial biomass suggested that the presence of aluminium interferes with the uranium biosorption process. Spectral analysis also indicated that the presence of silicon enhances the negative effect of the presence of aluminium on the uranium biosorptive uptake capacity of the immobilized Rhizopus arrhizus biomass particles. © 1997 SCI     

Denitrifying phosphorus removal with nitrite by a real‐time step feed sequencing batch reactor

BACKGROUND: Nitrite is toxic to anoxic phosphorus uptake when it exceeds a threshold concentration. In this study, denitrifying phosphorus removal with nitrite as electron acceptor was investigated in a sequencing batch reactor (SBR) operated using a real‐time step feed strategy. RESULTS: The nitrite pulse concentration was initially determined by batch experiments. pH increased with use of nitrite for phosphate uptake, and decreased when the nitrite was used up. Nitrite was added promptly after the pH reached the peak value, and phosphate uptake continued, driven by the nitrite addition. The pH was adjusted to 7.50 using HCl with each pulse of nitrite addition. ORP could be used to determine the endpoint of denitrifiying phosphorus removal. However, the variation of second derivative of ORP with time was much more sensitive and should be a more suitable control parameter than ORP itself to determine the endpoint of denitrifying phosphorus removal. CONCLUSION: Compared with denitrifying phosphorus removal with nitrate as electron acceptor, denitrifying phosphorus removal with nitrite using real‐time step feed can save 22.3% of polyhydroxyalkanoate (PHA) for phosphorus removal and 49.4% of PHA for nitrogen removal. In addition, the reaction time could be shortened. Copyright © 2010 Society of Chemical Industry     

Zirconium mesostructures immobilized in calcium alginate for phosphate removal

Eutrophication caused by the excessive supply of phosphate to water bodies has been considered as one of the most important environmental problems. In this study, the powder of zirconium mesostructure (ZM), which was prepared with the template of surfactant, was immobilized in calcium alginate for practical application and the resulting material was tested to evaluate the phosphate removal efficiency. Sorption isotherms and kinetic parameters were obtained by using the entrapped ZM beads with 30 to 60% of ZM. The maximum sorption capacity increased with the higher ZM content. Q _max in Langmuir isotherm was 51.74 mg/g for 60% of ZM with 7 mm of size. The smaller the particle size of the ZM beads, the faster the rate of phosphate removal, because the phosphate ions had less distance to reach the internal pores of the immobilized ZM beads. Chemical and electrochemical regeneration techniques were compared. Phosphates adsorbed on the ZM beads were effectively desorbed with NaCl, NaOH, and Na₂SO₄ solutions. An electrochemical regeneration system consisting of an anion exchange membrane between two platinum-coated titanium electrodes was successfully used to desorb and regenerate the phosphate-saturated ZM beads. Complete regeneration was reached under optimal experimental conditions. Chemical and electrochemical regeneration proved the reusability of the bead form of the entrapped ZM, and will enhance the economical performance of the phosphate treatment process.     

A2O工艺缺氧生物磷去除

A lab-scale anaerobic-anoxic-oxic （A^2O） process used to treat a synthetic brewage wastewater was investigated. The objectives of the study were to identify the existence of denitrifying phosphorus removing bacteria （DPB）, evaluate the contribution of DPB to biological nutrient removal and enhance the denitrifying phosphorus removal in A^2O bioreactors. Sludge analysis confirmed that the average anoxic P uptake accounted for approximately 70% the total amount of P uptake, and the ratio of anoxic P uptake rate to aerobic P uptake rate was 69%. In addition, nitrate concentration in the anoxic phase and different organic substrate introduced into the anaerobic phase had significant effect on the anoxic P uptake. Compared with conventional A^2O processes, good removal efficiencies of COD, phosphorus, ammonia and total nitrogen （92.3%, 95.5%, 96% and 79.5%, respectively） could be achieved in the anoxic P uptake system, and aeration energy consumption was saved 25%. By controlling the nitrate recirculation flow in the anoxic zone, anoxic P uptake could be enhanced, which solved the competition for organic substrates among poly-P organisms and denitrifiers successfully under the COD limiting conditions. Therefore, in wastewater treatment plants the control system should be applied according to the practical situation to optimize the operation.     

A2O工艺缺氧生物磷去除

A lab-scale anaerobic-anoxic-oxic (A2O) process used to treat a synthetic brewage wastewater was investigated. The objectives of the study were to identify the existence of denitrifying phosphorus removing bacteria (DPB), evaluate the contribution of DPB to biological nutrient removal and enhance the denitrifying phosphorus removal in A2O bioreactors. Sludge analysis confirmed that the average anoxic P uptake accounted for approximately 70% the total amount of P uptake, and the ratio of anoxic P uptake rate to aerobic P uptake rate was 69%. In addition, nitrate concentration in the anoxic phase and different organic substrate introduced into the anaerobic phase had significant effect on the anoxic P uptake. Compared with conventional A2O processes, good removal efficiencies of COD, phosphorus, ammonia and total nitrogen (92.3%, 95.5%, 96% and 79.5%, respectively) could be achieved in the anoxic P uptake system, and aeration energy consumption was saved 25%. By controlling the nitrate recirculation flow in the anoxic zone, anoxic P uptake could be enhanced, which solved the competition for organic substrates among poly-P organisms and denitrifiers successfully under the COD limiting conditions. Therefore, in wastewater treatment plants the control system should be applied according to the practical situation to optimize the operation.     

Comparative study of nitrification performances of immobilized cell fluidized bed reactor and contact oxidation biofilm reactor in treating high strength ammonia wastewater

BACKGROUND: The immobilized cell fluidized bed reactor and contact oxidation biofilm reactor are two common choices for high strength ammonia wastewater treatment, however, comparative study of the nitrification performance of the two reactors has not been thoroughly studied. The nitrification performance of the two bioreactors when treating strong synthetic ammonia wastewater was investigated and compared. RESULTS: Results demonstrated that the immobilized cell fluidized bed reactor had a shorter acclimation period, and possessed several advantages over the contact oxidation biofilm reactor, in the form of complete oxidation of 150–360 mg L^?1 ammonia wastewater in a shorter time, higher ammonia removal rates (from 9.6 to 4.32 × 10² mgN L^?1 d^?1) over the temperature range 8 to 32 °C, irrespective of organic load. In contrast, a large reduction in ammonia removal was found in the contact oxidation biofilm reactor with chemical oxygen demand (COD) load. The immobilized cell fluidized bed reactor exhibited stable and high rates of nitrification in the long term. CONCLUSION: These facts demonstrated that the immobilized cell fluidized bed reactor is a suitable selection for high strength ammonia wastewater treatment. Copyright © 2007 Society of Chemical Industry     

Biodegradation kinetics of trans‐4‐methyl‐1‐cyclohexane carboxylic acid in continuously stirred tank and immobilized cell bioreactors

BACKGROUND: Naphthenic acids are carboxylic acid compounds of oil sands wastewaters that contribute to aquatic toxicity. Biodegradation kinetics of an individual naphthenic acid compound in two types of continuous‐flow bioreactors were investigated as a means of improving remediation strategies for these compounds. RESULTS: This study evaluates the kinetics of biodegradation of trans‐4‐methy‐1‐cyclohexane carboxylic acid (trans‐4MCHCA) using two bioreactor systems and a microbial culture developed in previous work. Using a feed concentration of 500 mg L^?1 the biodegradation rate of trans‐4MCHCA in the immobilized cell bioreactor was almost two orders of magnitude higher than that in a continuously stirred tank bioreactor. The maximum reaction rates of 230 mg (L d)^?1 at a residence time of 1.6 d (40 h) and 22 000 mg (L d)^?1 at a residence time of 2.6 h were observed in the continuously stirred tank and immobilized cell bioreactors, respectively. In a second immobilized cell system operating with a feed concentration of 250 mg L^?1, a comparable maximum reaction rate (21 800 mg (L d)^?1) was achieved at a residence time of 1.0 h. CONCLUSION: The use of immobilized cell bioreactors can enhance the biodegradation rate of naphthenic acid compounds by two orders of magnitude. Further, biodegradation greatly reduces the toxicity of the effluent wastewater. Copyright © 2009 Society of Chemical Industry     

负载型纳米Fe/Ni材料同步去除水中硝酸盐/磷酸盐

水体的富营养化主要与硝酸盐和磷酸盐有关,但目前的处理方法大多只对其中一种污染物有去除效果。制备的负载型Fe/Ni双金属复合材料(DOW 3N-Fe/Ni)能实现NO_3~-和PO_4~(3-)的同步去除。当NO_3~--N为20 mg/L,PO_4~(3-)-P为1 mg/L时,NO_3~-和PO_4~(3-)的去除率分别可达70%和99%。探讨了DOW 3N-Fe/Ni同步去除NO_3~-和PO_4~(3-)的机理,铁镍金属在还原NO_3~-的过程中被氧化为金属离子或金属氧化物及氢氧化物,并通过Lewis酸碱理论、静电作用及吸附作用去除PO_4~(3-),实现NO_3~-和PO_4~(3-)的同步去除。     

Preparation of slow release encapsulated insecticide and fertilizer based on superabsorbent polysaccharide microbeads

The use of encapsulated fertilizers and pesticides is a key approach for slowing the release of agrochemicals, while simultaneously reducing costs and environmental problems. The use of hybrid systems for encapsulation in organic-based agriculture, which enables the release of agrochemicals in a single application, has been a growing field. In this approach, a formulation of Bacillus-thuringiensis as bio-pesticide and nitrogen, phosphorus, and potassium fertilizer (fish emulsion, potassium nitrate, and potassium phosphate) were formulated using superabsorbent polymers microbeads based on sodium alginate (ALG) then evaluated for release. Different formulations were prepared using 15 wt% of Bt, fish emulsion, nitrogen, and phosphorus. The encapsulated microbeads were prepared by wet-extrusion processing using sodium alginate as the superabsorbent polymer and calcium chloride as the gelling agent. The resulting beads were characterized in terms of size, morphology, water uptake, and biodegradability. The results showed that the prepared microbeads have narrow size distributions (1.2 to 2.1 mm) and increased water uptake (1,200–3,200%). Moreover, loaded microbeads were analyzed using inductively coupled plasma-optical emission spectroscopy and Elementar CHNS analyzer to obtain the fertilizer grades as (6.2–0.8–1.05), (0–6.3–6.4), and (0.62–0–2.4) for the one loaded with fish emulsion, for potassium phosphate loaded beads, and for potassium nitrate loaded beads, respectively.     

High concentrations ammonia removal by the cyanobacterium plectonema boryanum in a photobioreactor system

The potential application of the cyanobacterium Plectonema boryanum was investigated for the removal of ammonia from aqueous solution to meet the target concentration of below 0.02 mg/L free ammonia. This method can be applied as a final polishing step in a series of wastewater treatment steps to reduce the ammonia concentration to drinking water levels. The experiments were conducted in a 2 L photobioreactor using batch and semi-batch modes of operation. The effect of important growth parameters such as temperature, light intensity and pH were investigated to identify their relative significance in a batch photobioreactor. Concentrations of ammonia in aqueous samples were varied up to 420 mg/L to study ammonia removal rates and growth of the cyanobacterium. The ammonia removal rates and maximum growth rates of the cyanobacterium were calculated and compared with other studies reported in literature. Repeated fed-batch experiments demonstrate the viability of the process to reduce free ammonia in aqueous solutions to less than 0.02 mg/L. The results of this study demonstrate the potential application of cyanobacteria technology for ammonia removal at 100 mg/L of total ammonia and greater.     

Potential Ozone Applications for Water/Wastewater Treatment

Abstract

Several applications of ozonation were examined in this study for:

1. the treatment of stabilized high strength municipal landfill leachates,

2. the reclamation potential and toxicity reduction of municipal secondary effluents, and

3. the removal potential of phytoplanktons from surface waters.

The major parameters examined were the applied ozone dosage and the respective contact time. The application of single ozonation on leachates resulted in the efficient removal of color and organic loading, due to the respective oxidation, induced by ozonation. In addition, ozonation was found to be effective for the removal of the residual organic content of secondary municipal effluents. However, acute toxic effects after ozonation were observed on V. fischeri and were related to ozone concentration and contact time. Furthermore, the surface water used for drinking water production, was subjected to ozonation treatment for the removal of harmful cyanobacteria. Ozonation resulted in the reduction of the number of cyanobacteria species and in the breakage of the chain‐type species to cells with a lower number of atoms.     

改性Fe3O4纳米粒子的定性及对功能菌固定化与脱氮特性

为解决水体富营养化所导致的恶臭现象, 用SiO₂和壳聚糖(CS)对Fe₃O₄纳米粒子进行改性, 再运用纳米粒子与微胶囊吸附-包埋的方法固定化功能性菌株, 进而对该体系的脱氮特性进行了研究。通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)、热重分析(TGA)及振动样品磁强计(VSM)等手段对材料的形貌、结构、磁学性能等进行表征。研究结果表明, SiO₂与CS在Fe₃O₄微球表面形成的包覆层具有产物结晶度高、形态规则、磁性能优良等特点。磁性微球在20min时对菌株的吸附率达85.00%, 吸附的活菌数达(2.1～2.2)×10⁶cfu/mL。在对水体脱氮的研究中, 游离态菌株对氨氮和硝氮的去除率分别为54.13%和59.17%, 固定化菌株对氨氮和硝氮的去除率分别达到72.26%和74.56%。实验结果表明, 改性Fe₃O₄磁性微球对菌株吸附能力强, 微胶囊结构使固定化菌株比游离态菌株具有更强的脱氮性能, 且能延长Fe₃O₄磁性微球的生命周期。     

Novel approach for selective phosphate removal using colloidal layered double hydroxide nanosheets and use of residue as fertilizer

Onsite remediation of phosphate in wastewaters remains a challenge in water treatment technologies. Further, aftermath of the treated material is hitherto unknown and mostly disposed of as land-fill. A new method for onsite remediation of phosphate is proposed using colloidal layered double hydroxide (LDH) nanosheets and the treated material is valorized as phosphate release fertilizer. Nitrate containing NiAl-LDHs was prepared by hexamine hydrolysis and the colloidal suspension of LDH nanosheets was obtained by dispersing the wet cake in water through three different methods namely ultrasonication, mechanical shaking and hydrothermal. These nanosheets were explored for phosphate remediation; the quantity of phosphate removed depended on the amount of LDH present in the colloidal suspension. Powder X-ray diffraction, TEM, and UV–vis diffuse reflectance spectroscopic measurements revealed that the uptake is due to restacking of nanosheets. The uptake of phosphate was rapid for UD-LDH compared to parent powdered LDH; however, settling of nanosheets was hindered at higher than the stoichiometric amount of UD-LDH and is reasoned through zeta potential measurements. Uptake of phosphate was similar in wide pH range (4.5–11) while decreased sharply at lower pH. Selective uptake of phosphate in enriched seawater and sustained removal of phosphate in simulated “model pond systems” were achieved for UD-LDH. The restacked material after phosphate removal was utilized as an effective phosphate release fertilizer for the growth of a common green seaweed Ulva lactuca. Tapping the potential of colloidal LDH nanosheets for wastewater remediation and ingeniously using the treated material, here as fertilizer, offers a new approach with dual benefits.     

Performance of different immobilized‐cell systems to efficiently produce ethanol from whey: fluidized batch,packed‐bed and fluidized continuous bioreactors

BACKGROUND: The bioconversion of whey into ethanol by immobilized Kluyveromyces marxianus in packed‐bed and fluidized bioreactors is described. Both batch and continuous cultures were analyzed using three different strains of K. marxianus and the effect of the operating mode, temperature, and dilution rates (D) were investigated. RESULTS: All immobilized strains of K. marxianus (CBS 6556, CCT 4086, and CCT 2653) produced similar high yields of ethanol (0.44 ± 0.01 g EtOH g^?1 sugar). Significant variations of conversion efficiencies (66.1 to 83.3%) and ethanol productivities (0.78 to 0.96 g L^?1 h^?1) were observed in the experiments with strain K. marxianus CBS 6556 at different temperatures. High yields of ethanol were obtained in fluidized and packed‐bed bioreactors continuous cultures at different D (0.1 to 0.3 h^?1), with the highest productivity (3.5 g L^?1 h^?1) observed for D = 0.3 h^?1 in the fluidized bioreactor (87% of the maximal theoretical conversion), whereas the highest ethanol concentration in the streaming effluent (28 g L^?1) was obtained for D = 0.1 h^?1. Electronic micrographs of the gel beads showed efficient cell immobilization. CONCLUSION: Batch and continuous cultivations of immobilized K. marxianus in fluidized and packed‐bed bioreactors enable high yields and productivities of ethanol from whey. Copyright © 2012 Society of Chemical Industry     

Adsorptive Removal of Nitrate and Phosphate from Water by a Purolite Ion Exchange Resin and Hydrous Ferric Oxide Columns in Series

Elevated concentrations of nitrate and phosphate in surface and ground waters can lead to eutrophication, and nitrate can also cause health hazards to humans. The adsorption process is generally considered to be an efficient technique in removing these ions provided that the adsorbent is highly selective for these ions. Removal of nitrate and phosphate from a synthetic water (50 mg N/L as nitrate, 15 mg P/L as phosphate) and a wastewater (12.9 mg N/L as nitrate, 5.9 mg P/L as phosphate) using a Purolite A500P anion exchange resin and a hydrous ferric oxide (HFO) columns (60 cm height, 2 cm diameter, flow rate 1 m/h) in series containing 1–10% (w/w) of these adsorbents and the remainder anthracite (90–99%) were studied. Data from batch adsorption experiment at various concentrations of adsorbents satisfactorily fitted to Langmuir adsorption isotherm for nitrate and phosphate on Purolite with adsorption maxima of 64 mg N/g and 7 mg P/g and only for phosphate on HFO with adsorption maxima of 14 mg P/g. Both batch and column experiments showed that Purolite selectively removed nitrate and HFO selectively removed phosphate. The Purolite column BTC time was greater for nitrate than for phosphate. At the highest percentage by weight of Purolite almost all nitrate was removed in batch study and up to 1000 min in column study, but it was not able to remove a comparatively high percentage of phosphate. However, when the effluent from the Purolite column was passed through the HFO column almost all phosphate was removed. The two columns when set up in series also removed almost all nitrate and phosphate from the wastewater.     

Removal of radioactive strontium from water by coagulation–flocculation with ferric hydroxide

A systematic study of the removal of the radioactive fission product strontium from aqueous solution by ferric hydroxide flocs has shown that strontium can be removed effectively, in contrast to caesium which is poorly removed (?5%) under all conditions examined. Removal of strontium was enhanced by raising pH to a maximum of 10.5, increasing the iron/strontium ratio, or by adding phosphate ion, provided the phosphate/iron mole ratio did not exceed 0.33. In the absence of phosphate the optimum conditions for strontium removal, over the range of iron and strontium concentrations examined, were pH 10 and strontium/iron mole ratio 0.08. Addition of phosphate reduced the pH at which significant removal was obtained to about 8. The mechanism of removal has been identified as an ion-exchange reaction at the surface of the ferric hydroxide particles; consequently, when considering the process for the removal of stron-tium-90 from hard natural or process waters competitive effects from the larger concentrations of calcium and magnesium present in the water would become important.     

Evaluation of the parameters affecting nitrogen and phosphorus removal in anaerobic/anoxic/oxic (A/A/O) biological nutrient removal systems

Considerable research has been performed on biological nutrient removal (BNR) systems which remove the problematic nutrients, nitrogen and phosphorus, that cause eutrophication. This research focussed on setting up two laboratory‐scale anaerobic/anoxic/oxic (A/A/O) systems and investigating their reliability while undergoing various parameter changes. Pump failure, in the first trial, R1, led to a decrease in pH, exposure of the sludge to relatively low nitrate concentrations and reduction of the suspended solids concentration within the system. This adversely affected the phosphorus removal efficiency. Shock loading the system with increased influent phosphate concentrations for 56 days was shown to aid remediation of the phosphorus removal efficiency to values between 65 and 70% (w/w). The second trial, R2, highlighted the presence of bacteria capable of P‐uptake under anoxic conditions (in the presence of nitrate). The characteristic anaerobic P‐release was also evident. The bacteria responsible for phosphate uptake under anoxic conditions are thought to be the denitrifying phosphate removing bacteria (DPB). However, the presence of higher nitrate concentrations retarded the P‐removal efficiency to some extent. Secondary release of P was evident in the clarifier of the A/A/O system during the R2 trial and especially during times of increased nitrate concentrations in the system. Between 20 and 40% (w/w) of the P taken up in the oxic stage of the system was released in the clarifier at various stages throughout the trial. © 2000 Society of Chemical Industry     

两种MBR工艺处理含抗生素污水效果及反应器内微生物群落结构

采用活性污泥缺氧一好氧膜生物反应器（A／O—MBR）和固定化缺氧一好氧膜生物反应器（I—A／O—MBR）I艺处理。含抗生素污水,考察了不同污泥龄（SRT）和水力停留时间（HRT）对两种工艺处理含抗生素污水性能的影响以及反应器内微生物种群结构的变化情况。试验结果表明：在较长的SRT条件下,A／O—MBR的运行受HRT的影响较小,在较长SRT时,对COD、NH4^＋-N和六种典型抗生素的去除率可分别达到96．4％、96．9％和84．4％以上;当SRT减小到3d时,对COD、NH4^＋-N和六种典型抗生素的去除率有明显下降。I-A／O—MBR受HRT变化的影响较大,在HRT较低时,污染物的去除效果不佳。SRT和HRT分别对两种工艺中的微生物种群结构具有明显影响,随着SRT和HRT的降低,系统内优势种群种类减少,类似Enterobactersp．具有抗生素抗药性的微生物在含抗生素污水的处理过程中发挥了重要作用。SRT降低促使A／O—MBR系统内总细菌数量明显下降,抗生素抗性基因的占比增加,而HRT的降低则使总细菌数量略微升高;I-A／O—MBR反应系统内总细菌和抗生素抗性基因的数量受HRT变化影响较小,固定化颗粒内由于固定化材料的保护作用使总细菌和抗生素抗性基因数量保持稳定。但在较低的HRT条件下,微生物与污水中污染物接触时间短是导致I-A／O—MBR处理效果下降的主要原因。     

Biosorption of Lead by Immobilized Biomass of Brevundimonas vesicularis: Batch and Column Studies

The objective of the present study was to evaluate the feasibility of a strategy to remove lead [Pb(II)] from aqueous waste using Brevundimonas vesicularis, a bacterial species isolated from contaminated soil. Batch studies were conducted using free and immobilized biomass and the optimum conditions for removal of lead from solutions were determined. The maximum specific lead uptake of the dry biomass was found to be 12.4 mg g^?1. Column study was conducted using immobilized biomass and the maximum specific lead uptake was 74.8 mg g^?1. It is concluded that Brevundimonas vesicularis is a promising biosorbent to remove lead from contaminated wastewater.