Phosphorus removal from municipal wastewater by hydrous ferric oxide reactive filtration and coupled chemically enhanced secondary treatment: part I--performance.

This work examines the performance of a hydrous ferric oxide (HFO) reactive filtration (RF) process with coupled chemically enhanced secondary treatment (RECYCLE) for phosphorus removal from municipal wastewater (HFO-RF-RECYCLE). A 3-month, 0.95-ML/d (0.25-mgd) demonstration of HFO-RF-RECYCLE was performed at a municipal wastewater treatment plant equipped with oxidation ditches and secondary clarifiers. Influent to the plant averaged 6.0 mg/L phosphorus, with a tertiary effluent average of 0.011 mg/L phosphorus. Iron doses to the plant were low, at 5 mg/L. Inline recycling of HFO solution rejects to the plant influent resulted in a maximum 90.3%, dose-dependent reduction of phosphorus in the secondary effluent at 4.5 ML/d (1.2 mgd). Other results included reduction of total suspended solids and turbidity. A mass balance analysis was performed. We conclude that HFO-RF-RECYCLE may allow very low levels of phosphorus discharge from municipal wastewater treatment plants with a ferric-iron-based tertiary filtration process and residual recycling.     

The impact of the 2004 tsunami on coastal Thai communities: assessing adaptive capacity

The suddenness and scale of the 26 December 2004 tsunami and the challenges posed to affected communities highlighted the benefits of their members having a capacity to confront and adapt to the consequences of such a disaster. Research into adaptive capacity or resilience has been conducted almost exclusively with Western populations. This paper describes an exploratory study of the potential of a measure of collective efficacy developed for Western populations to predict the capacity of members of a collective society, Thai citizens affected by the 2004 tsunami, to confront effectively the recovery demands associated with this disaster. Following a demonstration that this measure could predict adaptive capacity, the role of religious affiliation, ethnicity and place of residence in sustaining collective efficacy is discussed. The implications of the findings for future research on, and intervention to develop, adaptive capacity among Thai citizens in particular and collectivist societies in general are discussed.     

Effects of ecological factors on the diurnal activity rhythm of Yakutian black-capped marmots (Marmota camtschatica bungei) in the arctic

It is established that the activity of marmots (the genusMarmota) on the surface is timed to the daylight period. In the Arctic, under conditions of continuous illumination (the polar day), the diurnal rhythm of black-capped marmotsMarmota camtschatica bungei on the surface has a “daylight” pattern. The main external regulator of the diurnal rhythm is the altitude of the sun above the horizon. In the cold period, however, the effect of air temperature on animal activity becomes stronger.     

Persistent organic pollutants in atmospheric deposition and biomonitoring with Tillandsia usneoides (L.) in an industrialized area in Rio de Janeiro state, southeast Brazil--Part II: PCB and PAH

Monitoring of immission of persistent organic pollutants in the industrialized area of Volta Redonda (V.R.) and in the National Park of Itatiaia (PNI) in southeast Brazil was performed using an endemic bromeliad species as biomonitor and measuring bulk deposition rates of polychlorinated biphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH). For the sum of PCB, overall deposition rates were between 17 and 314 ng/(m2 day) in winter and between 43 and 81 ng/(m2 day) in summer, respectively. Deposition rates of dioxin-like PCBs ranged from 0.14 to 2.8 pg WHO-TEQ/(m2 day) in winter and from 0.90 to 4.3 pg WHO-TEQ/(m2 day) in summer. PCB deposition rates (total PCB and WHO-TEQ) were in the same range in winter in V.R. and PNI. In summer, contamination levels in V.R. were 6-10-folds higher than in PNI. PCB concentrations in biomonitor samples from V.R. and PNI were in the same range in summer and in winter. Concentrations of total PCB ranged from 14 to 95 microg/kg dry matter (d.m.) in winter and from 18 to 27 microg/kg d.m. in summer, respectively. The TEQ values were between 1.7 and 4.1 ng WHO-TEQ/kg d.m. in winter and between 1.9 and 2.9 ng WHO-TEQ/kg d.m. in summer. PCB concentrations of di-ortho PCB but not of non-ortho PCB were a factor of 2-4 lower in summer in both areas. PCB congener profiles resembled those from technical formulations. The profiles shifted to the higher chlorinated congeners in summer, probable due to revolatilisation of the lighter components at higher temperatures. PCB profiles in biomonitor resembled those from deposition samples and the shift to the heavier congeners in summer was even more pronounced. PAH deposition rates were in a similar range in both areas (131-2415 ng/(m2 day)). PAH levels in biomonitor samples from V.R. were about one order of magnitude higher than in samples from PNI indicating the impact of local sources. PAH profiles revealed stationary thermal processes as main source of contamination in V.R. whereas in PNI, biomass burning seems to be the main contamination source.     

Chromium(VI) resistance and removal by actinomycete strains isolated from sediments

Forty-one isolated actinomycetes were used to study qualitative and semi-quantitative screening of chromium(VI) resistance. Chromate-removing activity was estimated using the Cr(VI) specific colorimetric reagent 1,5-diphenylcarbazide. Twenty percent of the isolates from El Cadillal (EC) and 14% of isolates from a copper filter plant (CFP) were able to grow at 13 mM of Cr(VI). All isolates from sugar cane (SCP) could grow up to Cr(VI) concentration of 17 mM. EC, CFP and SCP strains were able to remove 24%, 30% and more than 40% of Cr(VI), respectively. The highest and lowest Cr(VI) specific removal values were 75.5 mg g(-1) cell by M3 (CFP), and 1.5 mg g(-1) cell by C35 (EC) strains. Eleven Cr(VI) resistant strains were characterized and identified as species of the genera Streptomyces (10) and Amycolatopsis (1). Differences on actinomycete community composition between contaminated and non-contaminated soil were found. This study showed the potential capacity of actinomycetes as tools for Cr(VI) bioremediation.     

Sulfidation treatment of molten incineration fly ashes with Na2S for zinc, lead and copper resource recovery

The present study focuses on the conversion of heavy metals involved in molten incineration fly ashes to metal sulfides which could be thereafter separated by flotation. The sulfidation treatment was carried out for five molten incineration fly ashes (Fly ash-A to Fly ash-E) by contacting each fly ash with Na(2)S solution for a period of 10 min to 6h. The initial molar ratio of S(2-) to Me(2+) was adjusted to 1.20. The conversion of heavy metals to metal sulfides was evaluated by measuring the S(2-) residual concentrations using an ion selective electrode. The formation of metal sulfides was studied by XRD and SEM-EDS analyses. In the case of Fly ash-A to Fly ash-D, more than 79% of heavy metals of zinc, lead and copper was converted to metal sulfides within the contacting period of 0.5h owing to a fast conversion of metal chlorides to metal sulfides. By contrast, the conversion of about 35% was achieved for Fly ash-E within the same contacting period, which was attributed to a high content of metal oxides. Further, the S(2-) to Me(2+) molar ratio was reduced to 1.00 to minimize Na(2)S consumption and the conversions obtained within the contacting period of 0.5h varied from 76% for Fly ash-D to 91% for Fly ash-C. Finally, soluble salts such as NaCl and KCl were removed during the sulfidation treatment, which brought about a significant enrichment in metals content by a factor varying from 1.5 for Fly ash-D to 4.9 for Fly ash-A.     

Measuring and modelling experimental densities and ultrasonic velocities of aromatic and halogenated environmental pollutants

The potential environmental impact of aromatic and halogenated chemicals from the petrochemical and steel industry is of growning concern. The present paper deals with the modelling and experimental determination of density and speed of sound at the range 278.15-323.15 of six aromatic and halogenated compounds (Benzene, Toluene, Ethylbenzene, Fluorobenzene, 2-Fluorotoluene and Chlorobenzene). Fitting equations were applied to the data in order to correlate for later computer based design. The estimation of the studied properties was made by the application of different theoretical procedures. The Mchaweh-Nasrifar-Moshfeghian model (MNM), an equation of state based on the generalized van der Waals theory which combines the Staverman-Guggenheim combinatorial term of lattice statistics with an attractive lattice gas expression and the Free Length Theory showed a good response at the studied conditions.     

Sonochemical substrate selectivity and reaction pathway of systematically substituted azo compounds

The sonochemical degradation of the systematically substituted azo compound 2,7-dihydroxy-1-phenylazonaphthaline-3,6-disulfonic acid was investigated using a frequency of 850 kHz and an acoustic input power of 61 W. All derivatives were degraded completely within 6h by the ultrasonic treatment. Trifluoromethyl substituted azo compounds exhibited 2-3-fold higher degradation rates in comparison to the reference hydrogen substituted azo compound (k=0.54 h(-1)). In contrast to enzymatic processes (azoreductase or laccase), the ultrasonic treatment for these ortho-, meta-, and para-substituted azo compound showed 1.5-50-fold higher degradation rates. Additionally the ultrasound treatment was characterized by shorter reaction times. As a result of the detection and identification of specific intermediates using LC-MS a reaction pathway of the sonochemical degradation of the analysed azo compound is proposed indicating the formation of cyclohexadienone and naphthalene quinone derivatives.     

Modeling in-situ uranium(VI) bioreduction by sulfate-reducing bacteria

We present a travel-time based reactive transport model to simulate an in-situ bioremediation experiment for demonstrating enhanced bioreduction of uranium(VI). The model considers aquatic equilibrium chemistry of uranium and other groundwater constituents, uranium sorption and precipitation, and the microbial reduction of nitrate, sulfate and U(VI). Kinetic sorption/desorption of U(VI) is characterized by mass transfer between stagnant micro-pores and mobile flow zones. The model describes the succession of terminal electron accepting processes and the growth and decay of sulfate-reducing bacteria, concurrent with the enzymatic reduction of aqueous U(VI) species. The effective U(VI) reduction rate and sorption site distributions are determined by fitting the model simulation to an in-situ experiment at Oak Ridge, TN. Results show that (1) the presence of nitrate inhibits U(VI) reduction at the site; (2) the fitted effective rate of in-situ U(VI) reduction is much smaller than the values reported for laboratory experiments; (3) U(VI) sorption/desorption, which affects U(VI) bioavailability at the site, is strongly controlled by kinetics; (4) both pH and bicarbonate concentration significantly influence the sorption/desorption of U(VI), which therefore cannot be characterized by empirical isotherms; and (5) calcium-uranyl-carbonate complexes significantly influence the model performance of U(VI) reduction.     

Enhanced stability of hydrogen peroxide in the presence of subsurface solids

The stabilization of hydrogen peroxide was investigated as a basis for enhancing its downgradient transport and contact with contaminants during catalyzed H(2)O(2) propagations (CHP) in situ chemical oxidation (ISCO). Stabilization of hydrogen peroxide was investigated in slurries containing four characterized subsurface solids using phytate, citrate, and malonate as stabilizing agents after screening ten potential stabilizers. The extent of hydrogen peroxide stabilization and the most effective stabilizer were solid-specific; however, phytate was usually the most effective stabilizer, increasing the hydrogen peroxide half-life to as much as 50 times. The degree of stabilization was nearly as effective at 10 mM concentrations as at 250 mM or 1 M concentrations. The effect of stabilization on relative rates of hydroxyl radical activity varied between the subsurface solids, but citrate and malonate generally had a greater positive effect than phytate. The effect of phytate, citrate, and malonate on the relative rates of superoxide generation was minimal to somewhat negative, depending on the solid. The results of this research demonstrate that the stabilizers phytate, citrate, and malonate can significantly increase the half-life of hydrogen peroxide in the presence of subsurface solids during CHP reactions while maintaining a significant portion of the reactive oxygen species activity. Use of these stabilizers in the field will likely improve the delivery of hydrogen peroxide and downgradient treatment during CHP ISCO.