Start-up procedures and analysis of heavy metals inhibition on methanogenic activity in EGSB reactor

The effectiveness of operating an industrial UASB reactor, treating wastewater from the beer industry, with flows containing heavy metals was evaluated. A pilot-scale UASB reactor, already used to simulate the industrial reactor, was unsuccessfully employed. An easy start-up was obtained arranging it as an EGSB reactor. Considerations about this modification are reported. The effects of Cu(II), Ni(II) and Cr(III) ions on the anaerobic activity were analyzed by measurements of methane production rate and COD removal. The employed biomass was the sludge of the industrial UASB reactor, while a solution of ethanol and sodium acetate with COD of 3000 mg/L and a heavy metal concentration of 50 mg/L were continuously fed. Experimental results proved higher biomass sensitivity for copper and much slighter for nickel and chromium. Moreover, copper inhibition has been demonstrated to be less significant if a metal-free feed was provided to the system before copper addition.     

Complexes of zinc, copper, and nickel with the nonprotein amino acid L-alpha-amino-beta-methylaminopropionic acid: a naturally occurring neurotoxin

The non-protein amino acid L-alpha-amino-beta-methylaminopropionic acid (L-MeDAP) causes motor neuron dysfunction in macaques. The amino acid is a potent chelator of divalent metal ions such as copper and zinc. Binding constants nickel(II) for copper(II) and zinc(II) with L-MeDAP have been measured. Some copper(II) complexes of L-MeDAP have been synthesized and characterized by their electronic, infrared, and epr spectra. These results are used to comment on the possibility that metal ion complexation in the central nervous system is involved in the expression of the meurotoxicity of L-MeDAP.     

Impact of fluorides on the removal of heavy metals from an electroplating effluent using a flocculent brewer’s yeast strain of Saccharomyces cerevisiae

Abstract

Besides several toxic heavy metals, electroplating effluents can have in solution different cations and anions, which may influence heavy metals removal by the biomass. Among them, fluorides are commonly used in the electroplating industries and thus can be found in the respective wastewaters. In the present work, the effect of the presence of fluorides in the efficiency of chromium(III), copper(II) and nickel(II) removal, from an effluent, by heat-inactivated cells of a brewing flocculent strain of Saccharomyces cerevisiae was evaluated. The presence of fluorides severely decreased (>60%) the removal of chromium(III) by yeast biomass. This effect impaired the effective treatment of the effluent according to the US Environmental Protection Agency and the Portuguese law; conversely, a higher removal of copper(II) and nickel(II) was observed. This behaviour can be understood by metal speciation. In the presence of fluorides, chromium(III) was mainly complexed, becoming unavailable for yeast accumulation; this effect decreased the efficiency of chromium(III) removal. Thus, in the presence of fluorides, less chromium(III) is associated with biomass and consequently more yeast binding sites remain available for the uptake of other metals present in solution. This fact explains the increase of copper(II) and nickel(II) removal in the presence of fluorides.     

A novel membrane bioreactor enhanced by effective microorganisms for the treatment of domestic wastewater

The activated sludge membrane bioreactor (MBR) has been shown to have some advantages for the processing and reclamation of domestic wastewater. We hypothesized that certain microorganisms, chosen for their abilities to decompose the chemical components of raw sewage, would, when coupled with the MBR, significantly improve the stability and efficiency of this system. We selected environmental bacterial strains which oxidize ammonia and nitrites and produce protease, amylase, and cellulase for the development and testing of a novel biologically enhanced MBR (eMBR). We compared the eMBR with the activated sludge MBR. With the eMBR, the average values of effluent quality were: chemical oxygen demand (COD), 40 mg/l(average efficiency of removal 90.0%); and NH₄ ⁺–N, 0.66 mg/l(average efficiency of removal 99.4%). Effluent qualities met the standard and were stable during the entire 90 days of this study. For the activated sludge MBR, the COD removal rate was 91.7%, and the NH₄ ⁺–N removal (94.8%) was less than that of the eMBR. Start-up time for the eMBR was only 24–48 h, much shorter than the 7–8 days required to initiate function of the standard MBR. The biomass concentrations of total heterotrophic bacteria and autotrophic bacteria in the eMBR did not fluctuate significantly during the course of the study. Various kinds of microorganisms will establish an ecological balance in the reactor. Compared with the activated sludge MBR, the eMBR not only produced an excellent and stable quality of effluent but also resulted in a shorter time to start-up and significantly improved the efficiency of NH₄ ⁺–N removal.     

Increased removal of nickel and organics in the upflow anaerobic sludge bed filter reactor using sulfate and sulfide additions

Glucose (total organic carbon: 1,200 mg/l) and nickel (0 to 40 mg/l) were added to an anaerobic upflow sludge bed filter reactor. The removal efficiencies of total organic carbon and nickel were maintained to 95% and 98.5%, respectively, since nickel was precipitated with sulfide which was converted from sulfate added at 80 mg SO4-S/l by sulfate reducing bacteria. Sulfate therefore enhances its organic removal efficiency of AUBF reactor under the presence of heavy metal.     

Heavy metal adsorption properties of a submerged aquatic plant (Ceratophyllum demersum)

Heavy metals can be adsorbed by living or non-living biomass. Submerged aquatic plants can be used for the removal of heavy metals. In this paper, lead, zinc, and copper adsorption properties of Ceratophyllum demersum (Coontail or hornwort) were investigated and results were compared with other aquatic submerged plants. Data obtained from the initial adsorption studies indicated that C. demersum was capable of removing lead, zinc, and copper from solution. The metal biosorption was fast and equilibrium was attained within 20 min. Data obtained from further batch studies conformed well to the Langmuir Model. Maximum adsorption capacities (q(max)) onto C. demersum were 6.17 mg/g for Cu(II), 13.98 mg/g for Zn(II) and 44.8 mg/g for Pb(II). Kinetics of adsorption of zinc, lead and copper were analysed and rate constants were derived for each metal. It was found that the overall adsorption process was best described by pseudo second-order kinetics. The results showed that this submerged aquatic plant C. demersum can be successfully used for heavy metal removal under dilute metal concentration.     

Binding of transition metal ions [cobalt, copper, nickel and zinc] with furanyl-, thiophenyl-, pyrrolyl-, salicylyl- and pyridyl-derived cephalexins as potent antibacterial agents

A method is described for the preparation of novel cephalexin-derived furanyl-, thiophenyl-, pyrrolyl-, salicylyl- and pyridyl-containing compounds showing potent antibacterial activity. The binding of these newly synthesized antibacterial agents with metal ions such as cobalt(II), copper(II), nickel(II) and zinc(II) has been studied and their inhibitory properties against various bacterial species such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae are also reported. These results suggest that metal ions to possess an important role in the designing of metal-based antibacterials and that such complexes are more effective against infectious diseases compared to the uncomplexed drugs.     

Assessment of the metal removal capability of two capsulated cyanobacteria, Cyanospira capsulata and Nostoc PCC7936

Two capsulated, exopolysaccharide-producing cyanobacteria, Cyanospira capsulata and Nostoc PCC7936, were tested with regard to their metal removal capability by using copper as model metal. The experiments, carried out with the sole cyanobacterial biomass suspended in distilled water and confined into small dialysis tubings, showed that C. capsulata biomass is characterized by the best efficiency in metal removal, with a q_max (maximum amount of copper removed per biomass unit) of 96 ± 2 mg Cu(II) removed per g of protein in comparison with the value of 79 ± 3 of Nostoc PCC7936 biomass. The experimental data obtained with both cyanobacterial biomass best fit the Langmuir sorption isotherm. The sorption of copper started from the first minutes of contact with the metal and attained the equilibrium state, when no more copper removal was evident, after 5 and 6 hours, for C. capsulata and Nostoc PCC7936, respectively. The best efficiency in Cu(II) removal was obtained at pH 6.1–6.2, while the presence of Mg²⁺ or Ca²⁺ reduced copper removal capability of both species to 60–70% of their q_max. The results showed that the biomass of C. capsulata and Nostoc PCC7936 possesses a high affinity and a high specific uptake for copper, comparable with the best performances shown by other microbial biomass, and suggest the possibility to use the capsulated trichomes of the two cyanobacteria for the bioremoval of heavy metals from polluted water bodies.     

Antifungal cobalt(II), copper(II), nickel(II) and zinc(II) complexes of furanyl-,thiophenyl-, pyrrolyl-, salicylyl- and pyridyl-derived cephalexins

Some novel cephalexin-derived furanyl, thiophenyl, pyrrolyl, salicylyl and pyridyl Schiff's bases and their cobalt (II), copper (II), nickel (II) and zinc (II) complexes have been synthesized and studied for their antifungal properties against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata. The presence of metal ions in the investigated Schiff's base complexes reported here lead to significant antifungal activity, whereas the parent ligands were generally less active.     

Removal of selected metal ions from aqueous solution using modified corncobs

The objective of this study was to convert corncobs to metal ion adsorbents for wastewater treatment. Ground corncobs were modified with either 0.6 M citric acid (CA) or 1.0 M phosphoric acid (PA) to help improve their natural adsorption capacity. The effect of a combination of wash and modification treatment was tested for corncob adsorption efficiency with five different metal ions (cadmium, copper, lead, nickel, zinc) individually or in a mixed solution containing each metal at a 20 mM concentration. Results were compared to those of commercial resins Amberlite IRC-718, Amberlite 200, Duolite GT-73 and carboxymethylcellulose (CMC). Modified corncobs showed the same adsorption efficiency as Duolite GT-73 for cadmium, copper, nickel and zinc ions and had greater adsorption than CMC for nickel and zinc ions. For mixed metals, the modified corncobs exhibited the same adsorption efficiency as Duolite GT-73 for cadmium and copper ions and the same or higher adsorption than Amberlite IRC-718 for lead ions. Adsorption capacities of modified samples were compared to those of Amberlite IRC-718, Amberlite 200 and Duolite GT-73. Commercial resins generally had higher adsorption capacities than modified corncobs. However, the adsorption capacity of modified corncobs for copper and lead ions was equivalent to Duolite GT-73, but was lower than for Amberlite IRC-718 or Amberlite 200. Depending on the specific metal ion and the presence or absence of other metal ions, chemically modified corncobs were at least equivalent in adsorption properties to all of the commercial cation exchange resins examined in this study.     

Binding of Transition Metal Ions [Cobalt,Copper, Nickel and Zinc] with Furanyl-, Thiophenyl-, Pyrrolyl-, Salicylyl-and Pyridyl-Derived Cephalexins as Potent Antibacterial Agents

A method is described for the preparation of novel cephalexin-derived furanyl-, thiophenyl-, pyrrolyl-, salicylyl- and pyridyl-containing compounds showing potent antibacterial activity. The binding of these newly synthesized antibacterial agents with metal ions such as cobalt(II), copper(II), nickel(II) and zinc(II) has been studied and their inhibitory properties against various bacterial species such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae are also reported. These results suggest that metal ions to possess an important role in the designing of metal-based antibacterials and that such complexes are more effective against infectious diseases compared to the uncomplexed drugs.     

Antibacterial Co(II), Ni(II), Cu(II) and Zn(II) complexes of Schiff bases derived from fluorobenzaldehyde and triazoles

Antibacterial Schiff bases derived from 1,2,4-triazoles as well as their metal complexes incorporating cobalt(II), nickel(II), copper(II) and zinc(II) have been synthesized and characterized. Physico-chemical studies suggest that an octahedral geometry for the cobalt(II), nickel(II) and zinc(II)and square-planer geometry for the copper(II) complexes. These complexes have been screened for antibacterial activity against three Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis and Bacillus subtilis) and two Gram-negative (Salmonella typhi and Pseudomonas aeruginosa) bacterial strains, and results compared with the activity of the free ligands. The metal complexes were found to be more potent against one or more bacterial strains than the free ligands.     

Transition metal complexes of amino acids and derivatives containing disulphide bridges

The interaction of cobalt(II), nickel(II), copper(II) and zinc(II) with D-penicillamine disulphide, oxidized glutathione and L-cysteinylglycine disulphide were studied by pH-metric, spectrophotometric and EPR methods. D-Penicillamine disulphide forms binuclear complexes with all the metal ions studied. The formation of 1:1 complexes is characteristic of oxidized glutathione. L-Cysteinylglycine disulphide behaves like dipeptides, but the presence of two separate peptide moieties also results in the formation of various binuclear complexes. Metal ion-disulphide binding was not observed in any case.     

Metal binding and antibacterial activity of ciprofloxacin complexes

Four novel cobalt(II), copper(II), nickel(II) and zinc(II) complexes of the fluoroquinolone antibiotic ciprofloxacin have been prepared. The compounds were characterized by IR, UV-Visible, molar conductivity and elemental analyses. In all of the complexes, the drug ligand, ciprofloxacin (CFL) was coordinated through two carbonyl oxygen atoms. Octahedral and square-planar geometries have been proposed for the cobalt(II), nickel(II) and zinc(II), and copper(II) complexes, respectively. In vitro tests of susceptibility to these metal complexes showed stronger activity than that of ciprofloxacin against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Bacillus dysenteriae.     

Copper reduction in a pilot-scale membrane-free bioelectrochemical reactor

A pilot-scale, membrane-free, bioelectrochemical system (BES) reactor (16L in volume) installed by five cathodes with different distance to anode was tested for the removal of copper. CuSO4 solution was used as catholyte and anaerobic microorganisms grew as anodic biocatalyst. In the reactor, Cu(II) was reduced and recovered as solid-state copper deposits on cathodes accompanied with power production. When 600 and 2000 mg of Cu2+ were added into the cathode chamber, removal efficiency of 92% over 480 h and 48% over 672 h period with electric quantities of 2724 C and 8703 C, and cathodic efficiencies of 61.92% and 45.60% were achieved, respectively. The reduction reaction rate depended on the initial average Cu2+ concentration. The internal resistance decreased and voltage output increased as the distance of each cathode to anode decreased. The mass of metal Cu crystals and Cu(I) compounds deposited on each cathode was dependent on current intensity.     

A comparative study on heavy metal biosorption characteristics of some algae

The biosorption of copper(II), nickel(II) and chromium(VI) from aqueous solutions on dried (Chlorella vulgaris, Scenedesmus obliquus and Synechocystis sp.) algae were tested under laboratory conditions as a function of pH, initial metal ion and biomass concentrations. Optimum adsorption pH values of copper(II), nickel(II) and chromium(VI) were determined as 5.0, 4.5 and 2.0. respectively, for all three algae. At the optimal conditions, metal ion uptake increased with initial metal ion concentration up to 250 mg l⁻¹. Experimental results also showed the influence of the alga concentration on the metal uptake for all the species. Both the Freundlich and Langmuir adsorption models were suitable for describing the short-term biosorption of copper(II), nickel(II) and chromium(VI) by all the algal species.     

Advances in biotreatment of acid mine drainage and biorecovery of metals: 1. Metal precipitation for recovery and recycle

Acid mine drainage (AMD), an acidic metal-bearingwastewater, poses a severe pollution problem attributedto post mining activities. The metals usuallyencountered in AMD and considered of concern for riskassessment are arsenic, cadmium, iron, lead, manganese,zinc, copper and sulfate. The pollution generated byabandoned mining activities in the area of Butte, Montanahas resulted in the designation of the Silver Bow Creek–ButteArea as the largest Superfund (National Priorities List) sitein the U.S. This paper reports the results of bench-scalestudies conducted to develop a resource recovery basedremediation process for the clean up of the Berkeley Pit.The process utilizes selective, sequential precipitation (SSP)of metals as hydroxides and sulfides, such as copper, zinc,aluminum, iron and manganese, from the Berkeley Pit AMDfor their removal from the water in a form suitable foradditional processing into marketable precipitates and pigments.The metal biorecovery and recycle process is based on completeseparation of the biological sulfate reduction step and themetal precipitation step. Hydrogen sulfide produced in the SRBbioreactor systems is used in the precipitation step to forminsoluble metal sulfides. The average metal recoveries usingthe SSP process were as follows: aluminum (as hydroxide) 99.8%,cadmium (as sulfide) 99.7%, cobalt (as sulfide) 99.1% copper(as sulfide) 99.8%, ferrous iron (sulfide) 97.1%, manganese(as sulfide) 87.4%, nickel (as sulfide) 47.8%, and zinc (as sulfide)100%. The average precipitate purity for metals, copper sulfide,ferric hydroxide, zinc sulfide, aluminum hydroxide and manganesesulfide were: 92.4, 81.5, 97.8, 95.6 , 92.1 and 75.0%, respectively.The final produced water contained only calcium and magnesiumand both sulfate and sulfide concentrations were below usablewater limits. Water quality of this agriculturally usable watermet the EPA's gold standard criterion.     

Treatment of heavy metal-polluted wastewaters using the biofilms of a multistage rotating biological contactor

The ability of the biofilms of a three-stage rotating biological contactor (RBC) to treat wastewater contaminated with cadmium, copper and zinc was investigated. The system successfully removed the metals, in the order Cu > Zn > Cd with removal capacities of approximately 73, 42 and 33% respectively. Analysis of the contribution of each reactor indicated that metal removal was not uniform, with Reactor 1 showing a much higher removal capacity than Reactors 2 and 3. Energy dispersive X-ray spectroscopy (EDS) revealed the presence of all three metals on the surface of the biofilms in all three reactors. Closer inspection of the biofilms, in terms of biomass and biofilm thickness, revealed that the low metal removal in Reactors 2 and 3 was probably attributable to poor biofilm development in these two reactors compared to that in Reactor 1. The poor biofilm development was substantiated by low chemical oxygen demand (COD) removal in the latter two reactors.     

Coordinate repression of cholesterol biosynthesis and cytoplasmic 3-hydroxy-3-methylglutaryl coenzyme A synthase by glucocorticoids in HeLa cells.

The stability constants for the calcium and magnesium complexes of rhodanese are >10⁵m^?1 at both high and low substrate concentrations. The stoichiometry of alkaline earth metal ion binding totals close to 1 per 18,500 molecular weight. The usual assay reagents contain sufficient amounts of these metal ions to maintain added enzyme in its metal-complexed form. When reaction mixtures are treated with oxalate to remove calcium ions, inhibition of rhodanese activity is virtually complete under circumstances such that the contribution of magnesium ion is low.Zinc and a number of transition metal ions are inhibitors of rhodanese activity. Studies of the concentration dependence of these effects with zinc, copper, and nickel showed that: 1) Some cyanide complexes of these metals are competitive with the donor substrate, thiosulfate ion. The binding of the copper and zinc complexes is mutually competitive. 2) Another cyanide species of copper appears to combine with the free enzyme to form a functionally active complex. 3) The zinc cyanide species with a net positive charge is an inhibitor competitive with the acceptor substrate, cyanide ion.All of these observations are consistent with a model in which metal ions serve as the electrophilic site of rhodanese.