Inhibition of nitrification in the packed bed reactors by selected organic compounds

The effect of methanol, acetone, formalin and glucose on the nitrification process in the packed bed reactors has been investigated. For the utilized compounds the inhibition constant K_i was determined according to Dixon's method. The determined values were as follows: methanol K_i = 116.0 mg l^?1; acetone K_i = 804.2 mg l^?1; formalin K_i = 61.5 mg l^?1. The value of K_i for glucose has not been determined because glucose in applied concentration up to 11,325 mg l^?1 had no effect on the nitrification course.     

Denitrification en continu a l'aide de microorganismes immobilises sur des supports solidesContinuous denitrification by immobilized cells

In this paper, we describe a study of biological denitrification by immobilized cells. Nitrates are reduced in sterile solutions by Pseudomonas aeruginosa immobilized in a fixed bed reactor, and in synthetic waste water by mixed cultures immobilized into a fluidized bed reactor.The fixed bed reactor is a Plexiglas column filled with corn stovers (Table 1). It is 0.05 m in diameter and 0.55 in height, its volume being approx. 11. The fresh medium is injected at the base of the column and the liquid level is regulated by an overflow weir. Reactor and carrier are sterilized with ethylene-oxide. After sterilization 1 l. of a growing batch culture of Pseudomonas aeruginosa is introduced aseptically and the reactor is then fed continuously (45 ml h^?1) with fresh medium (NNO₃ = 40 mg l^?1) until the first steady state is reached.Nitrates and nitrites are determinated by means of a colorimetric method.Reactor efficiency remains constant for over 40 days. Nitrates and nitrites concentrations are measured inside the reactor for flow varying from 2 to 16 ml min^?1 (Fig. 2). Reductions of nitrates and nitrites seem to be two first-order reactions (Fig. 3 and Table 2) and constant rate increases with flow rate (Fig. 4). Until nitrate concentration reaches 960 mg/l^?1 (NNO₃) degradation is correct (Figs 5 and 6), beyond nitrites, which have been formed, seem to be inhibitor.Using this reactor, 50 mg NNO₃ have been reduced per hour and per liter of empty reactor, but it may be possible to reduce 140 mg NNO₃ l^?1 h^?1 if fresh medium contains 200 mg NNO₃ l^?1.The fluidized bed reactor is a Plexiglas column filled with earthenware. It is 0.05 m in diameter and 3.15 m in height, its volume being approx. 6.201. Fresh medium is injected at the base of the column and the liquid level is regulated by an overflow weir. Figure 7 shows the retention time of the liquid in the reactor in relation to flow. The first steady state has been reached after 2 weeks, and it has not been possible to know half life time of the column.Four experiments were conducted (Table 3) and, for each nitrate, nitrite and methanol concentrations in the reactor were measured (Fig. 8). So, it appears that reduction of nitrates and nitrites are two first-order reactions (Table 4) and that constant rate values, which are higher than in fixed bed reactor, increase with flow.The reactor is more affected by a flow shift than by a nitrate concentration shift in fresh medium, and biomass linked onto carrier is about 76 mg of dry matter g^?1 of earthenware.So, our fluidized bed column is able to reduce 560 mg NNO₃ h^?1 l^?1 of empty reactor, then retention time of liquid is less than 3 min.     

The application of the Roessler-Faxvog model to the analysis of the relation between visibility and pollution of the atmosphere in Katowice

This work reports the results of investigations into changes in visibility as a result of pollution for the area of Katowice. The interdependence of the two factors were analyses using the Roessler-Faxvog model, which enables us to estimate the coefficient of proportionality (A_E) between the extinction of atmosphere and its pollution as 4.5 m²g^?1.The results of extinction coefficient measurements (b_E) made with a Volz photometer are also shown. From this data we see that the value of A_E is equal to 4.9 m²g^?1. This fits well with the value of A_E obtained indirectly as a result of the visibility pollution analysis.     

Selection of growth rate model for activated sludges treating phenol

Research was undertaken for the purpose of selecting a growth rate model, i.e. a function relating specific growth rate, μ, to substrate concentration, S, for acclimated heterogeneous microbial populations metabolizing a phenolic waste and to gain an insight into the expected average and range of values of the kinetic “constants” for the selected model. Various sources of seed populations were employed and batch growth curves were generated using phenol as sole source of carbon. Comparison of the fit of the data obtained from 113 growth curves to five inhibition functions failed to distinguish a function which was statistically superior to the others. Since the Haldane equation proved to be the most readily adapted to curve-fitting procedures and insertion into mass balance equations for reactor performance, it was selected as the best representation of the experimental data. The values of the three pertinent biokinetic constants were as follows: μ_max, range = 0.08–0.36 h^?1, mean = 0.19 h^?1; K_S, range = 1.3–266 mg l^?1, mean = 75 mg l^?1; K_i, range = 66–1463 mg l^?1, mean 449 mg l^?1. Analysis of chemostat performance using growth constants determined in separate batch growth studies with seed from the chemostat showed that reasonably accurate prediction of the dilution rate at which the system attains μ1, the peak or critical specific growth rate designated by the Haldane equation, could be made. This finding indicates that batch growth rate data can be used for predictive control of activated sludge reactors treating toxic wastes.     

Wastewater treatment in a deep aeration tank

Pilot-scale experiments were conducted to investigate the performance of a deep aeration tank (DAT) (10 m deep) treating a high-strength synthetic wastewater and the DAT biokinetics. At the mean cell residence of 2 days or at the food to microorganisms ratio of 1.41 and less, the DAT reactor, operating continuously as completely mixed and without cellular recycle, removed more than 95% of the chemical oxygen demand of the wastewater. The treatment kinetics were observed to follow the Lawrence and McCarty's models in which the values of the kinetic constants Y, k_d, k and K₃ for this particular operating condition were found to be 0.53, 0.085, 9.25 day^?1 and 259 mg 1^?1, respectively. The results of solid separation by flotation, using the hydrostatic pressure developed in the DAT reactor, were satisfactory. However, better flotation results can be expected with the proper design and operation of the flotation tank.     

Phytoplankton in a polluted subarctic lake before and after nutrient reduction

Phytoplankton and water chemistry were studied in a eutrophic subarctic Swedish lake before and after nutrient reduction. Pollution started in 1964 and the lake had received about 4.5 tons of phosphorus by the time the treatment plant was built in 1974. After that only 18–20 kg P yr^?1 entered the lake. Before nutrient reduction the phytoplankton consisted principally of three species, Dictyosphaerium pulchellum var. minutum, Chromulina cv. darlecarlica and Cryptomonas cv. ovata. Two years after the P-load was reduced Chlamydomonas spp and Mallomonas akrokomos predominated in the plankton and their dominance has been maintained during the period of study. Seasonal average phytoplankton biomass decreased from 11.2 g m^?3 in 1973 to 2.9 g m^?3 in 1980. Average seasonal total phosphorus concentrations decreased from 168 μgl^?1 in 1973 to 74 μgl^?1 in 1980. Average Secchi depth readings increased from 1.3 m in 1973 to 2.1 m in 1980. Blue-green algae never had any quantitative importance in the lake and no blooms were observed.     

Filtration and clogging of permeable pavement loaded by urban drainage

Permeable pavement, as a sustainable infrastructure material can promote hydrologic restoration, particulate matter (PM) and solute control. However, filtration and commensurate clogging are two aspects of continued interest and discussion. This study quantifies filtration and clogging of cementitious permeable pavement (CPP) for loadings from 50 to 200 mg/L of hetero-disperse sandy-silt PM. The CPP mix design provides a hetero-disperse pore size distribution (PSD)_pore, effective porosity (φ_e) of 24% and median pore size of 658 μm with a standard deviation of 457 μm. The PM mass separation across the entire particle size distribution (PSD)_PM exceeds 80%; with complete separation for PM greater than 300 μm and 50% separation for suspended PM. Turbidity is reduced (42–95%), and effluent is below 10 NTU in the first quartile of a loading period. Permeable pavement illustrates reductions in initial (clean-bed) hydraulic conductivity (k₀) with loading time. For all PM loadings, k₀ (3.1 × 10^?1 mm/s) was reduced to 10^?4 mm/s for runoff loading durations from 100 to 250 h, respectively. Temporal hydraulic conductivity (k) follows exponential profiles. Maintenance by vacuuming and sonication illustrate that 96–99% of k₀ is recovered. Permeable pavement constitutive properties integrated with measured PM loads and a year of continuous rainfall-runoff simulation illustrate k reduction with historical loadings. Study results measure and model filtration and hydraulic conductivity phenomena as well as maintenance requirements of permeable pavement directly loaded by urban drainage.     

Critical ventilation velocity for tunnel fires occurring near tunnel exits

Ventilation is an effective method for controlling smoke during a tunnel fire. The “critical ventilation velocity” u_cr is generally defined as the minimum velocity at which smoke is prevented from spreading against the longitudinal ventilation flow in tunnel fire situations. This study conducted small-scale experiments to investigate u_cr for situations when tunnel fire occurs near tunnel exits. The model tunnel was 4 m long, 0.6 m wide and 0.6 m tall, and the fires were located at 0.5 m, 1.0 m and 1.5 m from the tunnel exit. 6.3×6.3 cm² and 9.0×9.0 cm² square asoline fuel pans were used as fire source. Results show that u_cr decreases as the fire approaches the tunnel exit.     

The source of hydrogen sulfide in anoxic sediment

Putrefactive hydrogen sulfide production in the upper 4 cm of sediment in two small freshwater and eutrophic Southeast Michigan, U.S.A., lakes ranged from 0.13 to 1.51 with an average of 0.46 mg S l^?1 day^?1. Sulfate reductive production of hydrogen sulfide at the same sites ranged from 0.7 to 3.2 with an average of 1.54 mg S l^?1 day^?1. Putrefactive hydrogen sulfide production represented 5.1–53% (average of 18.3–27.6%) of the total hydrogen sulfide produced at the two lakes over an April–October study period. ³⁵S labeled substrates were used to estimate hydrogen sulfide production rates.Proteolytic bacteria averaged 2.2 × 10⁴ cells ml^?1 sediment whereas sulfate reducers averaged 4.8 × 10² cells ml^?1 sediment. Putrefactive hydrogen sulfide production correlated highly with numbers of proteolytic bacteria (r² = 0.84) but the correlation between sulfate reduction and sulfate reducing bacteria was low (r² = 0.13).Interstitial soluble inorganic sulfate, protein and organic carbon were not closely correlated with hydrogen sulfide production rates or bacteria enumeration results. Natural substrate concentrations (S_n) used to estimate hydrogen sulfide production were supported by kinetic bioassay results.     

A kinetic model of steady state phosphorus fixation in a batch reactor—II. Effect of pH

Measurements of phosphorus fixation at the soil/solution ratio of 250 mg 500^?1 ml at pH = 2, 3, 5, 7 and 8 in a batch reactor with steady input of phosphate were carried out. All results reached a steady state and followed a Michaelis-Menten type equation as predicted for the catalytic process. Maximum rate of reaction showed a decrease with increase of pH due to the competitive effect between OH^? and H₂PO^?₄. The maximum value of 1/K at pH = 5 showed H₂PO^?₄ may be required in phosphorus adsorption for some specific-bonding mechanism with soil.     

Biological denitrification in an upflow sludge blanket reactor

A study was made of a denitrifying sludge blanket reactor without carrier material for the activated sludge. The reactor was fed with a solution of alcoholic waste and sodium nitrate. The highest surface load in our study was 2 m h^?1 and the sludge concentration in the sludge blanket at this flow was in the range of 40 g TS l^?1. To our opinion higher surface loads are attainable. The nitrate removal rate that at least can be obtained is 500 g NO^?₃ ? N m^?3 h^?1.     

Improved parameterization of dust emission (PM10) fluxes by the gradient method using the Naiman tower data at the Horqin desert in China

Dust emission/deposition flux has been estimated using the gradient method with the two-level (3 and 15 m high) measured PM₁₀ concentrations and the sonic anemometer measured momentum and kinematic heat fluxes at 8 m high from a 20-m monitoring tower located at Naiman (Horqin desert) in the Asian dust source region in China for the winter of November 2007 to March 2008. The time series of measured PM₁₀ concentration at 3 m high is used to identify the dust event and the non-dust event periods. It is found that the dust emission/deposition flux (F_C) shows a significant diurnal variation with the maximum emission flux of 5.8 kg km^? 2 h^? 1 at noon and the minimum of ? 1.6 kg km^? 2 h^? 1 in the afternoon for the non-dust event cases. Whereas for the dust event cases, the dust emission flux is found to occur when the prevailing winds are westerlies to northerlies with the maximum flux of 1275 kg km^? 2 d^? 1, while the maximum dust deposition flux of 148 kg km^? 2 d^? 1 occurs with the prevailing winds of southerlies to easterlies without any diurnal variation. The optimal regression equation between F_C and the friction velocity (u_*) for the dust emission cases is found to be F_C = 9.55 u_*^3.13 with the R² value of 0.73. However, this regression equation can be improved by taking into account the convective velocity (w_*). The resulting optimal regression equation is found to be F_C = 9.3(u_* ? 0.1w_*)^3.19 for the stable stratification (w_* < 0) with the R² value of 0.77 and F_C = 10.5(u_* + 0.34w_*)^4.11 for the unstable stratification (w_* > 0) with the R² value of 0.78, suggesting the importance of the convective velocity on the dust emission flux.     

Research in environmental radioactivity studies

A survey of the tissue and subcellular distribution of some enzyme activities of mixed-function oxygenase (MFO) and benzo [a] pyrene (BP) metabolism in Mytilus edulis has been carried out. Subcellular fractions were characterized by marker enzymes (pyruvate kinase, β-N-acetylglucoseaminidase, succinic dehydrogenase and glycose-6-phosphatase) and electron microscopy. The tissues examined in male and female mussels were the digestive gland, gills, mantle, posterior adductor muscle, foot, ‘rest’ fraction and blood cells. Evidence was obtained that in the female digestive gland in particular a signifant fraction of the microsomes co-sedimented with the mitochondria at 12 000 × g and some solubilization of the endoplasmic reticulum also occurred during homogenization and extraction. MFO activities and cytochromes were localized in the microsomes. Cytochrome P-450 was present only in the digestive gland and the P-450-associated activities were highest in this tissue. In contrast cytochrome b₅ was also present in the gills and mantle. The activities were higher in the digestive gland microsomes of female mussels than of males and were in females (means ± SEM, n = 4): 7.5 ± 0.7 (glucose-6-phosphate dehydrogenase), 930.2 ± 54.6 (NADH-ferricyanide reductase), 156.5 ± 9.5 (NADH-cytochrome c reductase) and 18.4 ± 4.6 (NADPH-cytochrome c reductase) (all in nmol min^?1 mg^?1 protein at 25°C); 31.0 ± 3.9 (BP hydroxylase, pmol min^?1 mg^?1 protein at 25°C); 75.5 ± 11.7 (b₅) and 134 ± 64 (P-450) (in pmol mg^?1 protein and both the pooled material of both sexes, n = 4). Digestive gland microsomal BP hydroxylase activity was partially inhibited by carbon monoxide, SKF-525A and α-naphtoflavone. Based on this evidence and an observed relationship between microsomal BP hydroxylase and NADPH-cytochrome c reductase activities, it is concluded that a cytochrome P-450 mediated MFO system is present in mussels.     

A parameterization of dust concentration (PM₁₀) of dust events observed at Erdene in Mongolia using the monitored tower data

Hourly mean time series of dust concentration (PM₁₀) measured at 3 m high and a sonic-anemometer measured momentum and kinematic heat fluxes at 8 m high above the surface have been obtained from a 20-m monitoring tower located at Erdene in the Asian dust source region of Mongolia for years of 2009 and 2010. These time series were used to identify dust events and to develop optimal regression equations for the dust concentration of dust events with the friction velocity (u_*) and the convective velocity scale (w_*). In total, 68 dust events were identified in 2009 (except for November) and 43 dust events for the period from March to August in 2010. The duration of each dust event ranged from 3-29 h in 2009 and 5-35 h in 2010. The maximum hourly mean dust concentration of the dust event was found to be 4,107 μg m^− 3 in May in 2009 and 4,708 μg m^− 3 in March in 2010 while a minimum of 251 μg m^− 3 in August in 2009 and 662 μg m^− 3 in June in 2010. The optimal regression equation for the dust concentration (C) of dust events was found to have the form of log C = a + b(u_* + cw_*)ⁿ, where a, b, c and n are constants that vary month to month. The convective velocity scale (w_*) that has not been taken into account in most dust modelings was found to enhance the dust concentration of dust events during the cold period from December to March when the soil temperature was below the freezing level for both the stable (w_* < 0) and unstable (w_* > 0) stratifications, whereas the convective velocity caused a reduction in the dust concentrations during the warm period from April to October, suggesting the importance of the convective velocity to estimate dust concentration of dust events.     

The effects of nickel and cadmium on the growth rate of Hydra littoralis and an assessment of the rate of uptake of 63Ni and 14C by the same organism

Hydra littoralis was used as a bioassay organism to determine the sublethal threshold concentrations of NiCl₂ and CdCl₂: the concentrations were found to be 75 and 20 μg 1^?1 respectively.The rates of uptake of ¹⁴C and ⁶³Ni were measured over periods of 24 h. It seemed that Hydra reached an equilibrium with ¹⁴C within this period, whereas the total uptake of ⁶³Ni was proportional to time.The changes in the mean specific growth rate of Hydra when related to the uptake of ⁶³Ni showed it probable that a detoxication process is taking place within the organism.     

Effect of Wind on Smoldering Combustion Limits of Moist Pine Needle Beds

We studied moist pine needle beds burning under the effect of wind, in order to determine the upper moisture limit for which there is fire propagation for different wind velocities. For this purpose we built a wind tunnel that allowed us to burn a 600 mm by 150 mm by 40 mm bed under wind velocities between 0.5 m/s and 5.0 m/s and controlled air temperature. Results show an increase in moisture limit from 54% to approximately 140%, for the velocity range indicated. Combustion at limiting conditions proceeds mainly by smoldering with some periods of flaming combustion. It was observed that, for conditions close to extinction, the smoldering front is not quenched at the surface. Additionally, it was also observed that a strong flow of hot gases exit from the fuel bed at the free surface. These two observations lead to the conclusion that the main heat sink is moisture evaporation and that heat losses to the surroundings is reduced by the blowing effect of the hot gases coming off the bed. A dimensional analysis suggests a correlation between moisture limit and wind velocity of the form M = A ? B/ \( {v} \) _w ² , where M is moisture limit for fire propagation, A and B are constants, and \( {v} \) _w is wind speed. Two dimensionless numbers helped to plot the smoldering temperature and fire propagation velocity in a more meaningful way. They are \( \Uppi_{1} = {{T_{sml} c_{p,g} } \mathord{\left/ {\vphantom {{T_{sml} c_{p,g} } {v_{w}^{2} }}} \right. \kern-0pt} {v_{w}^{2} }} \) and \( \Uppi_{2} = {{Mh_{fg} } \mathord{\left/ {\vphantom {{Mh_{fg} } {v_{w}^{2} }}} \right. \kern-0pt} {v_{w}^{2} }} \) , where T _sml is smoldering temperature, c _p,g is the gas specific heat, M is fuel moisture content and h _fg is the latent heat of water evaporation. A relatively high moisture limit at 5 m/s wind velocity is possible due to the relatively high air flow into the smoldering front and the efficient heat feedback produced in forward smoldering.     

Application of the mass balance equation in the estimation of beryllium and radium concentrations in the lower atmosphere

In this work the mass balance equation for estimation of changes in beryllium and radium concentrations was applied. The value of the coefficient of self-clearing of atmosphere, k₁, for beryllium and radium in the rainy and non-rainy period was calculated. In the industrial areas the values for beryllium and radium were very similar. In rainy days the value k₁ is 1.18h^?1. In the non-rainy period the self-clearing coefficient increases with wind speed. The change of k₁ together with the distance of emission source was also stated.The values of pollution background of beryllium and radium based on Reynolds model were also calculated.     

Nonlinear Earthquake Response Characteristics of a Central Clay Core Rockfill Dam

The effect of the 2008 Iwate-Miyagi Nairiku earthquake (M_J 7.2), Japan on the Aratozawa dam, which is a 74.4 m high rockfill dam with a central clay core located in the area, was studied with a main focus on the change in the vibration period, shear wave velocity, shear modulus, and pore-water pressure. In a vertical section of the central part of the dam, three sets of 3-component accelerometers and 15 pore water pressure meters were installed. During the main shock, the acceleration exceeded 10 m/s² at the gallery, inducing large shear strains in excess of 10^-3 and a sudden build-up of the excess pore water pressure in the core. Due to the large strains, the shear wave velocity and shear modulus showed a significant decrease from their initial values and the vibration period was elongated. The decreased shear wave velocity gradually recovered toward the end of the main shock, and continued to recover with the passage of time. The full recovery of the wave velocity was found to take at least one year, while the dissipation of the excess pore water pressure proceeded more quickly than the recovery of the wave velocity.     

The stability of particulate nitrate in the Los Angeles atmosphere

Simultaneous measurements of atmosphere particulate nitrate (NO₃^?) and its gas phase precursor nitric acid (HONO₂) were conducted in Los Angeles during severe smog episodes, and the results were compared to those predicted on the basis of thermodynamic data for the HONO₂ (g) + NH₃ (g) = NH₄ NO₃ (s) equilibrium. Over the wide range of conditions studied (four-hour averaged NO₃^? = 0.5?44.3 μg m^?3 HONO₂ = 1.4?36.0 μg m^?3, T = 10?33°C, humidity = 16?99%, ozone up to 460 ppb) the solid equilibrium model was found to be applicable to only about one-third of the total number of data sets. In this case good agreement was found between measured nitrate values and those expected from comparison of measured and equilibrium nitric acid concentrations. Samples collected at humidities above the deliquescent point of ammonium nitrate at the sampling temperature, for which the solid NH₄ NO₃ equilibrium no longer applies and solution chemistry must be considered, accounted for two-thirds of the data sets. For this subset, good agreement was also found between experimental results and theoretical considerations.