Arsenic removal using steel manufacturing byproducts as permeable reactive materials in mine tailing containment systems

Steel manufacturing byproducts were tested as a means of treating mine tailing leachate with a high As concentration. Byproduct materials can be placed in situ as permeable reactive barriers to control the subsurface release of leachate from tailing containment systems. The tested materials had various compositions of elemental Fe, Fe oxides, Ca-Fe oxides and Ca hydroxides typical of different steel manufacturing processes. Among these materials, evaporation cooler dust (ECD), oxygen gas sludge (OGS), basic oxygen furnace slag (BOFS) and to a lesser degree, electrostatic precipitator dust (EPD) effectively removed both As(V) and As(III) during batch experiments. ECD, OGS and BOFS reduced As concentrations to <0.5mg/l from 25mg/l As(V) or As(III) solution in 72 h, exhibiting higher removal capacities than zero-valent iron. High Ca concentrations and alkaline conditions (pH ca. 12) provided by the dissolution of Ca hydroxides may promote the formation of stable, sparingly soluble Ca-As compounds. When initial pH conditions were adjusted to 4, As reduction was enhanced, probably by adsorption onto iron oxides. The elution rate of retained As from OGS and ECD decreased with treatment time, and increasing the residence time in a permeable barrier strategy would be beneficial for the immobilization of As. When applied to real tailing leachate, ECD was found to be the most efficient barrier material to increase pH and to remove As and dissolved metals.     

Application of 'waste' metal hydroxide sludge for adsorption of azo reactive dyes

The capacity and mechanism of metal hydroxide sludge in removing azo reactive dyes from aqueous solution was investigated with different parameters, such as charge amount of dyes, system pH, adsorbent particle size, and adsorbent dosage. The three anionic dyes used were CI Reactive Red 2, CI Reactive Red 120, and CI Reactive Red 141, increasing in number of sulfonic groups, respectively. Only 0.2% (w/v) of powdered sludge (<75microm) achieved color removal from 30 mg l(-1) reactive dye solutions within 5 min without pH adjustment. The larger the charge amount of the dyes, the greater the adsorption (>90%) on the metal hydroxide sludge. The system pH played a significant role in the adsorption on metal hydroxides and formation of dye-metal complexes. The optimum system pH for dye adsorption was 8-9 which was close to the pH(zpc) of the sludge while the precipitation of dye-metal complexes occurred at system pH 2. The maximum adsorption capacity (Q degrees ) of the sludge for the reactive dyes was 48-62 mg dye g(-1) adsorbent. The Langmuir and Freundlich models showed that the higher charged dyes had a higher affinity of adsorption. The smaller particle size and the greater amount of adsorbent showed the faster process, due to an increase in surface area of adsorbent. Desorption studies elucidated that metal hydroxide sludge had a tendency for ion exchange adsorption of sulfonated azo reactive dyes. Leaching data showed that the treated water was nontoxic at a system pH above 5 or a solution pH above 2.     

Cadmium biosorption by free and immobilised microorganisms cultivated in a liquid soil extract medium: effects of Cd,pH and techniques of culture

Instead of soil clean-up, a process not very technically and economically suited to agricultural soil contaminated by heavy metals (with a low concentration of heavy metals but highly or potentially highly contaminated surfaces), the control of the transfer of cadmium from the soil to the crops may well be a convenient method. We tested the bacterium ZAN-044, the actinomycete R27 and a basidiomycete Fomitopsis pinicola isolated for their ability to biosorb Cd, in order to inoculate agricultural soils afterwards. We then compared the cadmium biosorption by viable microbial cells which were free or immobilised in alginate beads and incubated in a soil extract liquid medium at various pH values (5, 6 and 7) and cadmium concentrations (1 and 10 mg/l). The Cd concentration in the medium had the most important effect on the percentage of Cd biosorbed by the microorganisms, but the culture mode (free or immobilised cells) was not a side effect. In the case of F. pinicola and the actinomycete R27, the percentage of Cd biosorbed by free cells did not decrease when the Cd concentration in the medium increased (6-42% at the lowest Cd concentration to 11-48% at 10 mg Cd/l). On the other hand, with a low Cd concentration (1 mg Cd/l), the percentage of Cd biosorbed by the bacterium ZAN-044 was maximum (69%) at pH 7, while this bacterium did not grow at 10 mg Cd/l and it did not accumulate Cd. For the three micro-organisms tested, relatively low specific biosorptions of Cd were observed, when the microorganisms were cultivated with a soil extract medium ('poor' medium), comparatively to those with a 'rich' medium. Finally, the choice of microorganism for the inoculation of contaminated soils depends on the cadmium level in the medium and on the distribution of the metal between the biomass and the medium.     

Relationships among total recoverable and reactive metals and metalloid in St. Lawrence River sediment: bioaccumulation by chironomids and implications for ecological risk assessment

The availability and bioaccumulation of metals and metalloids, and the geochemical interactions among them, are essential to developing an ecological risk assessment (ERA) framework and determining threshold concentrations for these elements. The purpose of this study was to explore the relationships among total recoverable and reactive metals and metalloid in sediment and their bioaccumulation by chironomids. In the fall of 2004 and 2005, 58 stations located in the three fluvial lakes of the St. Lawrence River and its largest harbour area in Montreal, Canada, were sampled. Nine total recoverable and reactive metals (Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) and one metalloid (As) were measured in whole sediment using two extraction methods: HCl/HNO(3) and HCl 1N, respectively. The bioaccumulation of six metals (Cd, Cr, Cu, Ni, Pb and Zn) and As by chironomids was evaluated in a subset of 22 stations. Strong collinearities were observed between some total recoverable or reactive metal concentrations in sediment; two principal clusters, including collinear metals, were obtained. The first one included metals of mainly geological origin (Al, Cr, Fe, Mn, Ni), while the second one included As, Cd, Cu, Pb and Zn, which likely derive mainly from point sources of anthropogenic contamination. Each element also showed strong collinearity between their total recoverable and reactive forms (0.65< or =r < or =0.97). We can conclude that both chemical forms are equivalent for use in statistical models needed to explain biological responses and also in screening risk assessment. However, these relationships are not always proportional. Lower availability percentages were observed for Cd, Cu and Zn in the highly mixed-contaminated area of the Montreal Harbour, even though concentrations in sediment were higher. We observed a significant correlation (0.50< or =r < or =0.56) between concentrations in chironomids and concentrations of both total recoverable and reactive Cr and Pb in sediment. Arsenic was an exception, with accumulation by chironomids being highly related to reactive sediment concentrations. Finally, we observed variable influences of explanatory factors (e.g. sediment grain size, Al, Fe, Mn, S, TOC), depending on which metal or metalloid was being predicted in chironomids. In this context, it is difficult to choose a universal predictive method to explain the bioaccumulation of specific metals, and more research is still needed into normalization procedures that consider a combination of explanatory factors.     

Arsenic pollution in groundwater: a self-organizing complex geochemical process in the deltaic sedimentary environment,Bangladesh

The presence of considerable concentrations of As (Sonargon: below detection limit (bdl)-1.46 mg/l; Faridpur: bdl-1.66 mg/l) and some other elements (like B, F, U) in groundwater of the Ganges-Meghna-Brahmaputra (G-M-B) rivers flood plain indicate that several millions of people are consuming contaminated water. Conditions regulating the mobilization and diagenetic behavior of arsenic in sediments are not well characterized, although understanding these conditions is essential in order to predict the modes of transfer of this contaminant from sediments to groundwater. Analyses of vertical profiles of total arsenic and iron as well as easily soluble As and reducible (reactive) iron concentrations in sediments of the Ganges and Meghna flood plains show no arsenic-enriched layer up to 36-m depth. However, arsenic content in sediments is relatively higher than mean crustal concentration, showing some peaks (Sonargaon: 27.9 mg/kg; 3 m, 31.5 mg/kg; 9 m, 27.30 mg/kg; 16 m, 37.70 mg/kg; 29.5 m, Faridpur: 19.80 mg/kg; 6 m, 26.60 mg/kg; 14.5 m, 29.40 mg/kg; 25 m) depending on the periodical differences in sedimentary cycling of arsenic, metal (hydr)oxides and organic matter. Seasonal changes have no clear or consistent effect on the groundwater arsenic concentrations; with the exception of a small-scale localized irregular change (10-16%). However, easily reducible metal oxides and hydroxides were significant factors affecting the retention of arsenic by sediments during leaching. The biogeochemical cycling of arsenic and iron is closely coupled in deltaic systems where iron oxy-hydroxides provide a carrier phase for the deposition of arsenic in sediments. Analytical results of mimic leaching experiments strongly supported the reduction (Fe oxy-hydroxides) mechanism for arsenic mobilization in alluvial aquifer of deltaic sedimentary environment of G-M-B rivers flood plain.     

Effect of chromium(VI) on bacterial kinetics of heterotrophic biomass of activated sludge

The effect of hexavalent chromium, Cr(VI), on the maximum specific growth rate, mu(m) and biomass yield, Y(H), of heterotrophic biomass was studied in batch tests conducted under high (= 10) and low (= 1.5) substrate-to-biomass ratios (S0/X0). The effects of sludge age and biomass acclimatization to Cr(VI) on the bacterial kinetics were also studied. The mu(m) values were determined by measuring oxygen uptake rate (OUR) and volatile suspended solids (VSS) increase. Cr(VI) concentrations equal or greater than 10 mg l(-1) inhibited the growth of unacclimatized activated sludge and caused a significant decrease in mu(m) and Y(H) values. The acclimatization of biomass and the selection of a high operating sludge age reduced the inhibitory effect of Cr(VI). At a sludge age of 20 days, Cr(VI) concentrations of <10 mg l(-1) stimulated bacterial growth as evidenced by an increase in both the mu(m) and Y(H) values. Determining mu(m) values by OUR and VSS methods, revealed that the presence of Cr(VI) in unacclimatized biomass caused an inhibitory effect mostly on substrate oxidation, while in acclimatized biomass, anabolic pathways were inhibited more.     

Estimates of benthic fluxes of nutrients across the sediment-water interface (Guarapiranga reservoir, São Paulo, Brazil)

Concentration profiles of nutrients (dissolved organic carbon, nitrate, nitrite, ammonium and soluble reactive phosphorus) were determined in pore waters from sediment from the Guarapiranga reservoir (S?o Paulo, Brazil). Redox potential and acid volatile sulfide measurements on bulk sediment samples were determined in the field and laboratory, respectively. The sediment redox potential ranged from -170 to -220 mV at 0-1 cm and increased to somewhat higher values at 20 cm. The acid volatile sulfide (AVS) profile had a bimodal pattern with concentration peaks at 3 cm (27-55 mg kg(-1)) and 14 cm (70-110 mg kg(-1)). Dissolved organic carbon (DOC) concentrations increased from the surface (4.7-5.6 mg l(-1)) to 20 cm (values up to 12 mg l(-1)). The concentration of ammonium increased significantly with depth, with maximum concentrations occurring at 15 cm; nitrate-nitrite concentrations only increased appreciably at 10 cm. The SRP profiles increased in concentration from the surface to approximately 10-cm depth, with a maximum value of 1200 microg H2PO4- l(-1). Benthic fluxes from the sediment into the pore water ranged from 278 to 339 mg cm(-2) year(-1) for ammonium ions and from 8 to 18 mg cm(-2) year(-1) for SRP. These upward diffusive fluxes correspond to 47-70% and to 10-24% of the total deposition of N and P measured in the reservoir, respectively. The burial rates for N and P in these sediments are 30-54% and 76-89%, respectively.     

Integrated biological and physiochemical treatment process for nitrate and fluoride removal

The feasibility of an integrated biological and physiochemical water treatment process for nitrate and fluoride removal has been evaluated. It consisted of two sequencing batch reactors (SBRs) in series. Performance of the process in the treatment of 24 synthetic water samples having nitrate concentrations of 40, 80, 120, 160, 200, and 250 mg/l (as N) and fluoride concentrations of 6, 10, 15, and 20 mg/l at different combinations was studied. Denitrification followed by defluoridation proved to be the best sequence of treatment. In all cases nitrate could be reduced to an acceptable level of less than 10 mg/l (as N) at 3, 5, and 7 h hydraulic retention times (HRTs) depending on its initial concentration. Fluoride concentrations up to 15 mg/l associated with nitrate concentrations up to 80 mg/l (as N) could be reduced acceptable 1.5 mg/l by alum-PAC slurry using alum doses up 850 mg/l [as Al2(SO4)3 x 16H2O] along with 100 mg/l of powdered activated carbon (PAC). Additional alkalinity produced during denitrification was used up during defluoridation for maintenance of pH avoiding the need for lime addition. On the other hand, residual organics, turbidity, and sulfide present in the denitrified water are removed by alum and PAC at the defluoridation stage along with fluoride, eliminating the need for an additional post-treatment step. At higher nitrate concentrations (> or = 120 mg/l as N), the alkalinity produced at the denitrification stage was in the range of 715-1175 mg/l as CaCO3. This excessive alkalinity inhibited reduction of fluoride to the level of 1.5 mg/l at the defluoridation stage, using alum doses up to 900 mg/l along with 100 mg/l of PAC. In all cases a fluoride concentration of 20 mg/l in water could not be reduced to the acceptable level of 1.5 mg/l.     

Investigating the environmental transport of human pharmaceuticals to streams in the United Kingdom

The occurrence of 12 selected pharmaceutical compounds and pharmaceutical compound metabolites in sewage treatment works (STW) effluents and surface waters was investigated. The substances selected for the monitoring programme were identified by a risk ranking procedure to identify those substances with the greatest potential to pose a risk to the aquatic environment. STW final effluent and surface water samples were collected from Corby, Great Billing, East Hyde, Harpenden and Ryemeads STWs. Ten of the 12 pharmaceutical compounds were detected in the STW effluent samples: propranolol (100%, median = 76 ng/l), diclofenac (86%, median = 424 ng/l), ibuprofen (84%, median = 3086 ng/l), mefenamic acid (81%, median = 133 ng/l), dextropropoxyphene (74%, median = 195 ng/l), trimethoprim (65%, 70 ng/l), erythromycin (44%, < 10 ng/l), acetyl-sulfamethoxazole (33%, median =< 50 ng/l), sulfamethoxazole (9%, median =< 50 ng/l), tamoxifen (4%, median =< 10 ng/l). In the corresponding receiving streams, fewer compounds and lower concentrations were found: propranolol (87%, median = 29 ng/l), ibuprofen (69%, median = 826 ng/l), mefenamic acid (60%, median = 62 ng/l), dextropropoxyphene (53%, median = 58 ng/l), diclofenac (47%, median =< 20 ng/l), erythromycin (38%, median =< 10 ng/l), trimethoprim (38%, median =< 10 ng/l), acetyl sulfamethoxazole (38%, median =< 50 ng/l). Four human pharmaceutical compounds were detected in samples upstream of the STWs sampled: ibuprofen (57%, median = 181 ng/l), trimethoprim (36%, median < 10 ng/l), erythromycin (17%, median =< 10 ng/l), propranolol (14%, median =< 10 ng/l), suggesting that longer range stream transport of some compounds is possible. The particular STW that was sampled and the month that it was sampled significantly influenced the measured concentrations of several, but not all, substances. There was no significant relationship between usage data and the overall frequency with which different substances were detected. There was however, some evidence to suggest that usage data are positively associated with concentrations of pharmaceuticals in effluent and, particularly, with concentrations measured in surface waters below STWs. These results suggest that most sewage treatment works in England and Wales are likely to be routinely discharging small quantities of pharmaceuticals into UK rivers. None of the pharmaceuticals were found at concentrations that were high enough to cause acute toxic impacts to aquatic organisms. However, insufficient data were available to be able to comment on whether the concentrations measured have the potential to result in more subtle long-term effects on aquatic organisms (e.g. effects on growth, ability to reproduce).     

Iron and hydrogen sulfide interference in the analysis of soluble reactive phosphorus in anoxic waters

Anoxic water from eight lakes containing various amounts of ferrous iron, hydrogen sulfide, calcium and total phosphorus was analysed for soluble reactive phosphorus (SRP). Hydrogen sulfide concentrations higher than 1 mg l⁻¹ and ferrous iron concentration above 0.20 mg l⁻¹ produce interferences in the SRP analysis in many occasions (e.g. 80% underestimation of SRP). Interfering concentrations of these materials are shown to be present in anoxic water from a large number of lakes, groundwater springs and ocean basins.The mechanisms of the interferences are discussed and methods described to prevent these analytical errors. Ferrous iron is not problematic if the sample is kept anoxic before and during filtration. On the other hand vigorous aeration is obligatory if hydrogen sulfide is present. Simple methods to test for both the possible interfering compounds are presented. It is shown for the water from the anoxic hypolimnia of eight lakes that a modified analysis of total (unfiltered) reactive phosphorus (TRP) yields on average only 2% lower phosphorus concentrations than SRP analysis. TRP hence can replace the complicated SRP analysis in anoxic waters.     

Bioaccumulation of platinum group elements and characterization of their species in Lolium multiflorum by size-exclusion chromatography coupled with ICP-MS

The bioaccumulation of Pt, Pd and Rh by grass grown hydroponically with nutrient solutions containing these ions at elevated (38.7 mg l(-1) Pt, 21.7 mg l(-1) Pd and 7.1 mg l(-1) Rh) and medium (3.6 mg l(-1) Pt, 4.4 mg l(-1) Pd and 0.5 mg l(-1) Rh) concentrations was studied by using inductively coupled plasma sector field mass spectrometry (ICP-SFMS). The highest bioaccumulation factors were obtained for Pd and Rh in roots and for Pt in leaves. The obtained results showed that most of the studied metals were accumulated in roots, and only a small fraction was really metabolised and transported to leaves. The multi-element capability of ICP-SFMS has been exploited to study the metabolism of platinum group elements (PGEs) in cultivated plants. The species of studied metals were extracted from roots and leaves and separated into two mass fractions by ultra-filtration. The low molecular mass (<10 kDa) fractions of the root and the leaf extracts were investigated by size-exclusion chromatography (SEC) coupled on-line to ICP-SFMS. The presence of Ca, Cu, S and C in the same fractions as Pt, Pd and Rh may indicate the interaction of PGEs with phytochelatins and carbohydrates.     

Passive treatment of ferruginous mine waters using high surface area media

Rapid oxidation and accretion of iron onto high surface area media has been investigated as a potential passive treatment option for ferruginous. net-alkaline minewaters. Two pilot-scale reactors were installed at a site in County Durham, UK. Each 2.0 m high cylinder contained different high surface area plastic trickling filter media. Ferruginous minewater was fed downwards over the media at various flow-rates with the objective of establishing the efficiency of iron removal at different loading rates. Residence time of water within the reactors was between 70 and 360 s depending on the flow-rate (1 and 12 l/min, respectively). Average influent total iron concentration for the duration of these experiments was 1.43 mg/l (range 1.08-1.84 mg/l; n = 16), whilst effluent iron concentrations averaged 0.41 mg/l (range 0.20-1.04 mg/l; n = 15) for Reactor A and 0.38 mg/l (range 0.11-0.93 mg/l; n = 16) for Reactor B. There is a strong correlation between influent iron load and iron removal rate. Even at the highest loading rates (approximately 31.6 g/day) 43% and 49% of the total iron load was removed in Reactors A and B, respectively. At low manganese loading rates (approximately 0.50-0.90 g/day) over 50% of the manganese was removed in Reactor B. Iron removal rate (g/m3/d) increases linearly with loading rate (g/day) up to 14 g/d and the slope of the line indicates that a mean of 85% of the iron is removed. In conclusion. it appears that the oxidation and accretion of ochre on high surface area media may be a promising alternative passive technology to constructed wetlands at certain sites.     

Kinetics of the oxidation of cylindrospermopsin and anatoxin-a with chlorine, monochloramine and permanganate

Cyanobacteria produce toxins that may contaminate drinking water sources. Among others, the presence of the alkaloid toxins cylindrospermopsin (CYN) and anatoxin-a (ANTX) constitutes a considerable threat to human health due to the acute and chronic toxicity of these compounds. In the present study, not previously reported second-order rate constants for the reactions of CYN and ANTX with chlorine and monochloramine and of CYN with potassium permanganate were determined and the influence of pH and temperature was established for the most reactive cases. It was found that the reactivity of CYN with chlorine presents a maximum at pH 7 (rate constant of 1265 M(-1)s(-1)). However, the oxidation of CYN with chloramine and permanganate are rather slow processes, with rate constants <1 M(-1)s(-1). The first chlorination product of CYN was found to be 5-chloro-CYN (5-Cl-CYN), which reacts with chlorine 10-20 times slower than the parent compound. The reactivity of ANTX with chlorine and chloramines is also very low (k<1M(-1)s(-1)). The elimination of CYN and ANTX in surface water was also investigated. A chlorine dose of 1.5 mg l(-1) was enough to oxidize CYN almost completely. However, 3 mg l(-1) of chlorine was able to remove only 8% of ANTX, leading to a total formation of trihalomethanes (TTHM) at a concentration of 150 microg l(-1). Therefore, chlorination is a feasible option for CYN degradation during oxidation and disinfection processes but not for ANTX removal. The permanganate dose required for CYN oxidation is very high and not applicable in waterworks.     

Treatment of perchlorate- and nitrate-contaminated groundwater in an autotrophic,gas phase,packed-bed bioreactor

The biological degradation of perchlorate was examined using a laboratory-scale, autotrophic, packed-bed biofilm reactor. The reactor was operated in unsaturated-flow mode and continuously fed water containing perchlorate (ClO4-) (as an electron acceptor), and a gas mixture of hydrogen (5%) and carbon dioxide at a retention time of 1.5 min. In the absence of nitrate, perchlorate removal rate (rp, ppb/min) in the reactor was found to be first order with respect to perchlorate concentration (c, ppb) according to rp = 0.16 +/- 0.06c(0.97+/-0.12) (n = 11, R2 = 0.97, p < 10(-5)). Perchlorate removal rates in the hydrogen feed were found to be comparable to rates found by others for fixed film bioreactors using either hydrogen gas or organic electron donors such as acetate, although the rate coefficient was reduced to slightly less than unity (r(p) = 0.22 +/- 0.08c(0.91+/-0.08); n = 19, R2 = 0.89, p < 10(-5)). When nitrate was present in the water, similar perchlorate removals were achieved despite nitrate concentrations three orders of magnitude higher than perchlorate concentrations. Perchlorate was removed by an average of 25 +/- 5% from a perchlorate-contaminated groundwater containing 73 +/- 2 ppb of perchlorate and 21 +/- 2 ppm of nitrate. This removal was slightly higher than the removal of 17 +/- 3% measured for a synthetic groundwater containing 79 +/- 3 ppb of perchlorate and 22 +/- 2 ppm of nitrate. In both cases, there was an average of 10% nitrate removal.     

Comparative effects of biostimulation and phytoremediation on crude oil degradation and absorption by water hyacinth (Eichhornia crassipes [Mart.] Solms)

This study investigated the effects of inorganic fertilizer (urea) amendment on crude oil degradation and uptake by water hyacinth (Eichhornia crasssipes). Experimental units (fresh borehole water) were spiked with crude oil at four different concentrations and then were randomly assigned fertilizer (urea) at three different concentrations. Crude oil degradation and absorption were determined monthly by measuring total petroleum hydrocarbon (TPH) in water column and water hyacinth, respectively. The water hyacinth planted in the control absorbed significantly (p?相似文献   

Behaviour of uranium in hydroxyapatite-bearing permeable reactive barriers: investigation using 237U as a radioindicator

This study was undertaken to investigate the long-term performance of hydroxyapatite (HAP) as reactive material for the removal of uranium in passive groundwater remediation systems. 237U used as a radioindicator enabled tracking the movement of the contamination front through a test column without taking samples or dismantling the apparatus. The stoichiometric ratio between uranium and HAP was found to be 1:(487 +/- 19). Uranium removal by HAP is of pseudo first-order kinetics and the rate constant was measured to be (1.1 +/- 0.1) x 10(-3) s(-1). HAP can sorb more than 2900 mg/kg uranium. Possible reaction pathways of uranium and HAP are discussed. The data obtained enable the calculation of ideal lifetime for permeable reactive barriers (PRB) using HAP for uranium removal neglecting hydrological factors that may impair the function of PRBs.     

Blood lead concentrations and iron deficiency in Canadian aboriginal infants

Aboriginal Cree infants living in northern Quebec who were 9 months of age were screened for anemia, iron deficiency and elevated blood lead concentrations. Of the 314 infants who were eligible to participate, 274 (87.3%) were screened for anemia, 186 had blood lead concentration measured and 141 of the latter group had iron status determined. The median blood lead concentration was 0.08 micromol/l (range 0.01-1.00 micromol/l). The 25, 50 and 75 percentiles for blood lead concentration were 0.05, 0.08 and 0.12 micromol/l, respectively. The prevalence of elevated blood lead concentrations (> 0.48 micromol/l) was 2.7% (95% Cl 0.36-5.0). Among infants who had blood lead measured, the prevalence of anemia (hemoglobin < 110 g/l) was 25.0% and 7.9% of infants had iron-deficiency anemia (hemoglobin < 110 g/l and serum ferritin < 10 microg/l). Anemic infants had a higher mean geometric blood lead concentration than did babies without anemia (0.11 micromol/l vs. 0.07 micromol/l, P = 0.003). Likewise, infants with iron-deficiency anemia had a significantly higher mean geometric blood lead concentration than infants without iron deficiency anemia (0.16 micromol/l vs. 0.07 micromol/l, P = 0.001). There was a significant negative correlation between blood lead and hemoglobin concentrations (r = -0.203, P = 0.006) and between blood lead and serum ferritin concentrations (r = -0.245, P = 0.003). Infants who were fed traditional food (fish, fowl and game) did not have a significantly different mean geometric blood lead concentration, hemoglobin concentration or serum ferritin concentration than infants who did not eat traditional food. Few infants (5.3%) ate traditional food daily.     

Sorption and redox processes controlling arsenic fate and transport in a stream impacted by acid mine drainage

Reigous acid creek originating from the Carnoulès tailings impoundment supplies high concentrations of arsenic under soluble (up to approximately 4 mg/l) and particulate (up to 150 mgAs/g) phases to the Amous river, situated at the drainage basin of the Rh?ne river (Southern France). The metalloid is present as As(III) (>95%) in Reigous creek water while As(V) predominates (50-80%) in the solid phase, i.e. schwertmannite. At the confluence between acid (pH<5) creek and alkaline Amous river, As(III) concentrations decrease ten-fold through dilution and formation of As-rich ferrihydrite (As/Fe=0.02-0.1) containing 10-30% As(III). However, these attenuation processes are not efficient in the summer heatwave of 2003 since As concentrations in Amous river water (>or=20 microg/l) and As/Fe ratios in particulate matter (>or=0.07) are closed to those of Reigous creek (相似文献   

Simultaneous removal of phenol and ammonia by an activated sludge process with cross-flow filtration

Attempts were made for removing ammonia from synthetic wastewater under the presence of phenol, which is inhibitory to nitrification, by using a single-stage activated sludge process with cross-flow filtration. Activated sludge biomass which had been acclimated with phenol for over 15 years was used for the inoculum, and synthetic wastewater was continuously supplied to the process retaining biomass at 8000 mg VSS l(-1). Phenol was completely removed, and ammonia was simultaneously nitrified to nitrate; nitrification rate reached 200 mg N l(-1) d(-1) when phenol was removed at a rate up to 300 mg l(-1) d(-1). It was observed that 0-13% of the ammonia was removed via denitrification. Intermittent aeration enhanced the denitrification rate to 160 mg N l(-1) d(-1) by utilizing phenol. and approximately 24% of the denitrified nitrogen was recovered as nitrous oxide. Methanol, which is the most commonly used electron donor in conventional nitrogen removal processes, did not enhance the denitrification rate of the phenol-acclimated activated sludge used in this study, however phenol did. The results suggest that this process potentially works as a space- and energy-saving nitrogen removal process by utilizing substances inhibitory to nitrifiers as electron donors for denitrification.     

Atrazine degradation in anaerobic environment by a mixed microbial consortium

Atrazine degradation by anaerobic mixed culture microorganism in co-metabolic process and in absence of external carbon and nitrogen source was studied at influent atrazine concentration range of 0.5-15 mg/l. Wastewater of desired characteristic was prepared by the addition of various constituents in distilled water spiked with atrazine. In co-metabolic process, dextrose of various concentrations (150-2000 mg/l) was supplied as external carbon source. The reactors were operated in sequential batch mode in which 20% of treated effluent was replaced by the same amount of fresh wastewater everyday, thus maintaining a hydraulic retention time (HRT) equal to 5 days. In co-metabolic process, 40-50% of influent atrazine degradation was observed. First-order atrazine degradation rate (expressed in day(-1)) was better in co-metabolic process (5.5 x 10(-4)) than in absence of external carbon source (2.5 x 10(-5)) or carbon and nitrogen source (1.67 x 10(-5)). In presence of 2000 mg/l of dextrose, atrazine degradation was between 8% and 15% only. Maximum atrazine degradation was observed from wastewater containing 300 mg/l of dextrose and 5mg/l of atrazine. Influent atrazine concentration did not have much effect on the methanogenic bacteria which was clear from methane gas production and specific methanogenic activity (SMA).