Effect of sonication assisted by titanium dioxide and ferrous ions on polyaromatic hydrocarbons (PAHs) and toxicity removals from a petrochemical industry wastewater in Turkey

BACKGROUND: In Izmir (Turkey) polyaromatic hydracarbon (PAH) removal efficiencies are low in petrochemical industry aerobic biological wastewater treatment plants because bacteria are not able to overcome the inhibition of these toxic and refractory organics. In order to increase PAHs removal, sonication process was chosen among other advanced treatment processes include sonication processes. The effects of ambient conditions, increasing sonication time, sonication temperature, TiO₂ and Fe⁺² concentrations on sonication at a petrochemical industry wastewater treatment plant in Izmir (Turkey) was investigated in a 650 W sonicator, at a frequency of 35 kHz and a 500 mL glass reactor. RESULTS: Increasing the temperature improved PAH removal after 150 min sonication at 30 °C and 60 °C. The maximum total PAH removal efficiencies were the same in a reactor containing 20 mg L^?1 TiO₂ and in a TiO₂‐free reactor at 30 °C and 60 °C after 150 min sonication. Maximum 91% and 97% total PAH removals were obtained in a control reactor and a reactor containing 20 mg L^?1 Fe⁺² at 30 °C and 60 °C, respectively, after 150 min sonication. The PAH concentration was toxic to Daphnia magna, so that the EC₅₀ value decreased significantly from 342.56 ng mL^?1 to EC₅₀ = 9.88 ng mL^?1 and to EC₅₀ = 3.35 ng mL^?1, at the lowest TiO₂ (0.1 mg L^?1) and Fe⁺² (2 mg L^?1) concentrations, respectively, after 150 min sonication at 30 °C. CONCLUSION: PAHs and the acute toxicity in a petrochemical industry wastewater were removed efficiently through sonication. Copyright © 2010 Society of Chemical Industry     

Kinetics of syntrophic acetogenesis in a saline medium

BACKGROUND: The anaerobic degradation kinetics of volatile fatty acids (VFA) in a saline (24 g NaCl dm^?3) and mesophilic (37 °C) medium was studied under batch test conditions. The acetate production kinetics without inhibition by propionic, butyric and valeric acids was determined. The inhibition of acetate production during syntrophic acetogenesis by VFA and pH was studied. The acetogenesis without inhibition was modelled using a Monod equation. The pH inhibition was represented by a Michaelis pH function, while the inhibition by acetic acid (HAc) was represented by a non‐competitive model. RESULTS: The specific maximum degradation rate and saturation constant (k_{max, VFA}, K_{S, max}) values were (5.89, 15.95), (7.97, 25.99) and (7.75 g VFA g^?1 volatile suspended solids day^?1, 11.52 mg VFA dm^?3) for propionic, butyric and valeric acids respectively, with maximum velocity at pH 7. The inhibition constants (K_{I, HAc}) were 1295, 671 and 572 mg HAc dm^?3 for propionic, butyric and valeric acids respectively. CONCLUSION: VFA and pH can be inhibitory for acetogenesis under these conditions. Copyright © 2008 Society of Chemical Industry     

Rate of ammonia oxidation in a synthetic saline wastewater by a nitrifying mixed‐culture

Most of the kinetic studies on nitrification have been performed in diluted salts medium. In this work, the ammonia oxidation rate (AOR) was determined by respirometry at different ammonia (0.01 and 33.5 mg N‐NH₃ L^?1), nitrite (0–450 mg N‐NO₂^? L^?1) and nitrate (0 and 275 mg N‐NO₃^? L^?1) concentrations in a saline medium at 30 °C and pH 7.5. Sodium azide was used to uncouple the ammonia and nitrite oxidation, so as to measure independently the AOR. It was determined that ammonia causes substrate inhibition and that nitrite and nitrate exhibit product inhibition upon the AOR. The effects of ammonia, nitrite and nitrate were represented by the Andrews equation (maximal ammonia oxidation rate, r_AOMAX, = 43.2 [mg N‐NH₃ (g VSS_AO h)^?1]; half saturation constant, K_SAO, = 0.11 mg N‐NH₃ L^?1; inhibition constant K_IAO, = 7.65 mg N‐NH₃ L^?1), by the non‐competitive inhibition model (inhibition constant, K_INI, = 176 mg N‐NO₂^? L^?1) and by the partially competitive inhibition model (inhibition constant, K_INA, = 3.3 mg N‐NO₃^? L^?1; α factor = 0.24), respectively. The r_AOMAX value is smaller, and the K_SAO value larger, than the values reported in diluted salts medium; the K_IAO value is comparable to those reported. Process simulations with the kinetic model in batch nitrifying reactors showed that the inhibitory effects of nitrite and nitrate are significant for initial ammonia concentrations larger than 100 mg N‐NH₄⁺ L^?1. Copyright © 2005 Society of Chemical Industry     

Biomonitoring of biosurfactant production by green fluorescent protein‐marked Bacillus subtilis W1012

BACKGROUND: Biosurfactant production was investigated using two strains of Bacillus subtilis, one being a reference strain (B. subtilis 1012) and the other a recombinant of this (B. subtilis W1012) made able to produce the green fluorescent protein (GFP). RESULTS: Batch cultivations carried out at different initial levels of glucose (G₀) in the presence of 10 g L^?1 casein demonstrated that the reference strain was able to release higher levels of biosurfactants in the medium at 5.0≤G₀≤10 g L^?1 (B_max = 104–110 mg L^?1). The recombinant strain exhibited slightly lower levels of biosurfactants (B_max = 90–104 mg L^?1) but only at higher glucose concentrations (G₀ ≥ 20 g L^?1). Under these nutritional conditions, the fluorescence intensity linked to the production of GFP was shown to be associated with the cell concentration even after achievement of the stationary phase. CONCLUSION: The ability of the genetically‐modified strain to simultaneously overproduce biosurfactant and GFP even at low biomass concentration makes it an interesting candidate for use as a biological indicator to monitor indirectly the biosurfactant production in bioremediation treatments. Copyright © 2008 Society of Chemical Industry     

Kinetics and thermodynamics of glucoamylase inhibition by lactate during fermentable sugar production from food waste

BACKGROUND: Glucoamylase hydrolysis is a key step in the bioconversion of food waste with complicated composition. This work investigated the effect of lactate on glucoamylase from Aspergillus niger UV‐60, and inhibition mechanisms of glucoamylase by lactate during food waste hydrolysis. RESULTS: For 125 min hydrolysis of food waste (10%, dry basis), reducing sugars produced in the absence of lactate were 15%, 26% and 56% more than those produced in the presence of 24 g L^?1 lactate at 60, 50 and 40 °C, respectively. Kinetic study showed that the type of glucoamylase inhibition by lactate was competitive, and K_m (Michaelis‐Menten constent), V_max (maximum initial velocity), K_I (inhibition constant) were 103.2 g L^?1, 5.0 g L^?1 min^?1, 100.6 g L^?1, respectively, for food waste hydrolysis at 60 °C and pH 4.6. Lactate also accelerated glucoamylase denaturation significantly. Activation energy of denaturation without inhibitor was 61% greater than that of denaturation with inhibitor (24 g L^?1 lactate). Half‐lives (t_1/2) without inhibitor were 7.6, 2.7, 2.6, 1.7 and 1.2 times longer than those with inhibitor at temperature 40, 45, 50, 55 and 60 °C, respectively. CONCLUSION: These results are helpful to process optimization of saccharification and bioconversion of food waste. Copyright © 2010 Society of Chemical Industry     

Sorption of polycyclic aromatic hydrocarbons from aqueous solution by hexadecyltrimethylammonium bromide modified fibric peat

BACKGROUND: Fibric peat was modified by hexadecyltrimethylammonium bromide (HTAB) to improve its performance in sorption of polycyclic aromatic hydrocarbons (PAHs). The raw fibric peat (P‐R) and surfactant modified peat (P‐HTAB) were characterized by capillary rise test to determine the effect of HTAB on surface hydrophobicity. Effect of contact time was also investigated. Batch sorption data were fitted to the Freundlich model and pseudo‐second‐order model for isotherm and kinetics study. RESULTS: P‐HTAB had a more hydrophobic surface than P‐R. After modification, the sorption coefficients (K_OC) of naphthalene, phenanthrene and pyrene on fibric peat increased from 1590, 29661 and 204171 mL g^?1 to 2006, 52410 and 358569 mL g^?1, respectively; the sorption rate constants of naphthalene, phenanthrene and pyrene increased from 0.00057, 0.00036 and 0.00051 g µg^?1 min^?1 to 0.00062, 0.00140 and 0.00155 g µg^?1 min^?1, respectively. The sorption coefficients of PAHs were positively correlated with the octane‐water partition coefficients of PAHs. CONCLUSIONS: The hydrophobicity of fibric peat was enhanced through modification by HTAB, which resulted in the improved sorption rate and sorption capacity for PAHs. The sorption performance of P‐HTAB reveals that it is an effective biosorbent for PAHs and has potential for treatment of wastewater containing hydrophobic organic contaminants. Copyright © 2010 Society of Chemical Industry     

Monitoring and Origin of Polycyclic Aromatic Hydrocarbons (PAHs) in Effluents from a Surface Treatment Industry

ABSTRACT

In Europe, polycyclic aromatic hydrocarbons (PAHs) are a source of concern due to their toxic effects and are considered as priority pollutants by water authorities. In this study, we reported the results of qualitative and quantitative monitoring of 16 PAHs in effluents from a surface treatment industry to determine their origin. The results indicated that PAHs were present in the discharge waters at a concentration of 500 ng L^?1 (in average for the PAH sum). However, the further we returned to the start of the industrial process, the more the PAH concentrations increased. Indeed, the highest concentrations (>20,000 ng L^?1 for the PAH sum) were found in the degreasing baths – the first step in the part treatment. The final analyses showed that the PAHs came from the oils left on the metal parts by the suppliers. The important difference in concentrations between the upstream (first baths in the production line) and the downstream (discharge water) of the effluent showed that phenomena including dilution or potentially degradation occurred but that the major part of the PAHs tended to adsorb to sludge during the settling step in the effluent treatment plant.     

Kinetic characterization and modeling simplification of an anaerobic sulfate reducing batch process

BACKGROUND: A series of kinetic experiments for a sulfate reducing process was carried out in a batch laboratory reactor that allowed simplification of a model initially proposed for this system enabling establishment of the kinetic parameters. RESULTS: It was found that an incomplete oxidation of lactate is the most significant bio‐reaction occurring in the reactor; this fact led to model simplifications that allowed determination of the kinetic parameters. Sulfide and pH inhibition can be described using one inhibition term within the model equation, given the fact that sulfide inhibition is not present in the system. Kinetic parameters were obtained, yielding a maximum specific rate (µ_max/Y) of 2.17 ± 0.08 mg sulfate mg^?1 VSS min^?1. A zero‐order kinetics with respect to sulfate and a Monod affinity constant of 142.7 ± 64.9 mg L^?1 for the lactate were found. CONCLUSIONS: The final model for the process can be described by a single Monod term involving the lactate. This model resulted from the lack of sulfide inhibition in the system and the predominance of the partial lactate oxidation to acetate reaction over the complete lactate and acetate oxidation. Copyright © 2010 Society of Chemical Industry     

POLYCYCLIC AROMATIC HYDROCARBONS ANALYZED IN RAINWATER COLLECTED ON TWO SITES IN EAST OF FRANCE (STRASBOURG AND ERSTEIN)

Polycyclic Aromatic Hydrocarbons (naphtalene, acenaphtene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[j]fluoranthene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylène, indeno[1,2,3-c,d]pyrene and coronene) have been consecutively analyzed in rainwater sampled in Strasbourg (urban site) and Erstein (rural site) between January 2002 and June 2003 and between April 2002 and June 2003 on a weekly basis respectively. For the sampling of rainwater, a wet-only rainwater sampler was used together with an open collector to take the measurements of precipitation.

PAHs in rainwater were extracted by using SPE cartridges and analyzed by HPLC-fluorescence following a method developed in the laboratory.

Mean concentrations of all PAHs (Σ 16 HAPs) varied between 0.15 and 79.60 ng·L^?1 in Erstein, and between 3.70 and 1596.45 ng·L^?1 in Strasbourg. Naphtalene, phenanthrene, fluoranthene, pyrene, chrysene, benzo[j]fluoranthne and benzo[a]pyrene were the most concentrated PAHs analyzed. Benzo[a]pyrene was frequently detected. Seasonal effects were observed with a maximum of concentrations of PAHs during cold periods. Some spatial influences were also reported. The calculation of some PAH ratios show that diesel exhaust could be the main source of PAHs in rainwater on the two sites.     

Gas-Particle Partitioning of PAHs In The Urban Air of Dalian,China: Measurements and Assessments

To evaluate the gas-particle partitioning behavior of polycyclic aromatic hydrocarbons (PAHs) in the urban air of Dalian, China, both gas phase and particle phase ambient air were monitored with active high-volume sampler from November 2009 to October 2010. The average total concentration of 16 US EPA priority monitoring PAHs (particle + gas) (∑PAHs) was 112 ng m^?3 and the most abundant PAH was Phenanthrene. ∑PAHs and the gas-particle partitioning coefficients (K _p) of PAHs displayed seasonal variation in the order of winter > autumn > spring > summer. ∑PAHs was much higher during the heating period than non heating period. ∑PAHs in gas phase were all higher than those in particle phase in the four seasons. The PAHs sources identification was attempted using diagnostic ratios. The relationship between the concentration of PAHs in the air and meteorology parameters were analyzed using SPSS packages. The concentrations of PAHs in the air decreased with the increase of ambient temperature, and increased with the increase of atmospheric pressure. The gas-particle distribution was examined through several different approaches such as the relationship of logK _p with the ambient temperature, with the logarithm of the sub-cooled vapor pressure (logP _L ⁰), and the octanol-air partitioning coefficient (logK _oa) of PAHs. The slopes obtained from regressing logK _p vs. logP _L ⁰ was ?0.687～?0.821 in heating periods, which was in the range between ?0.6 and ?1, indicating the partitioning of PAHs to particle phase in the urban air of Dalian was absorption as well as for adsorption mechanism. However, the average slope value was ?0.502 in the non heating periods, which was shallower than -0.60, indicating that the absorption mechanisms contributed more to the partitioning process. The exposure risk of PAHs was evaluated with four methods, the results of which indicated that the quality of the urban air of Dalian was better.     

Biological treatment of high salinity produced water by microbial consortia in a batch stirred tank reactor: Modelling and kinetics study

This study was performed to evaluate the potential of acclimated halophilic microorganisms, commercial microorganisms, and microorganisms from polluted soil to degrade crude oil in high salinity oily wastewater (synthetic produced water) at different salt concentrations ranging from zero to 250,000?mg?L^?1 of total dissolved solids (TDS). The highest degradation of crude oil (>60%) was found for acclimated halophilic microorganisms at TDS of 35,000?mg?L^?1. An increase in the TDS concentrations above 145,000?mg?L^?1 leads to a significant decrease in the growth of microorganisms. The results showed that efficiency of the commercial microorganisms was less than the acclimated halophilic microorganisms. The oil biodegradation followed substrate inhibition kinetics and the specific growth rate were fitted to the Haldane model. The biokinetic constants for the saline oily water at TDS of 35,000?mg?L^?1, i.e., Y, K_s, µ_max, and 1/K_i, were 0.21?mg?MLSS/mg crude oil, 0.27?mg?L^?1, 0.019?h^?1, and 0.002?mg?L^?1, respectively.     

GAS-PARTICLE PARTITIONING OF POLYCYCLIC AROMATIC HYDROCARBONS DURING THE SPRING AND SUMMER IN A SUBURBAN SITE NEAR MAJOR TRAFFIC ARTERIES

Concentrations of atmospheric polycyclic aromatic hydrocarbons were measured in a suburban site near major traffic arteries during the period April-August 2006. Total suspended particulate during the sampling period was 65.3 ± 33.9 μ g m^?3. Total PAH concentrations were 63.5 ± 20.1 ng m^?3 in the gaseous phase and 1.4 ± 0.3 ng m^?3 in the particulate phase. Observed concentrations were comparable with previously measured values reported in the literature for urban and suburban sites with a high anthropic influence. PAH concentration diagnostic ratios indicate that, during the spring and summer seasons, vehicular emission was the main source of atmospheric PAHs.

Gas/particle partitioning coefficients K _P were well correlated with both the sub-cooled liquid vapor pressures p _L ⁰ and the octanol-air partition coefficients K _OA . Measured K _P values were in a good agreement with K _P values predicted by applying a literature model, which takes into account both adsorption onto black carbon and absorption into the organic matter.     

Study of a newly isolated thermophilic bacterium capable of Kuhemond heavy crude oil and dibenzothiophene biodesulfurization following 4S pathway at 60 °C

BACKGROUND: To meet stringent emission standards stipulated by regulatory agencies, the oil industry is required to bring down the sulfur content in fuels. As some compounds cannot be desulfurized by existing desulfurizing processes (such as hydrodesulfurization, HDS) biodesulfurization has become an interesting topic for researchers. Most of the isolated biodesulfurizing microorganisms are capable of desulfurization of refined products whose predominant sulfur species are dibenzothiophenes so biocatalyst development is still needed to desulfurize the spectrum of sulfur‐bearing compounds present in whole crude. RESULTS: The first desulfurizing bacterium active at 60 °C has been isolated, which reduces DBT concentration from 2 mmol L^?1 to 0.1 mmol L^?1 after 95 h, following the 4S pathway. Its DBT desulfurization pattern was represented by the Michaelis‐Menten equation. Various parameters such as V_max, K_m, µ_m, K_s and maximum specific DBT desulfurization rate were calculated which are 0.092 mmol L^?1 h^?1, 3.554 mmol L^?1, 0.157 h^?1, 3.722 mmol L^?1 and 0.192 mmol L^?1 DBT g^?1 DCW (dry cell weight) h^?1, respectively. It can desulfurize 50% of the sulfur content of Kuhemond heavy crude oil (KHC oil) with an initial sulfur content of 7.6%wt in 6 days. Its maximum specific desulfurization rate for KHC oil is equivalent to 0.005 g sulfur g^?1 DCW h^?1. The bacterium was isolated during a heavy crude oil biodesulfurization project initiated by PEDEC, a subsidiary of National Iranian Oil Company. CONCLUSION: The KHC oil sulfur removal efficiency of the bacterium is approximately five times that of BBRC‐9016 bacterium. It removes sulfur selectively without using sulfur‐containing compounds as its carbon source. By applying various media during its isolation, the probability of screening the correct microorganism is increased. Copyright © 2008 Society of Chemical Industry     

Modeling of Rhamnolipid Biosurfactant Production: Estimation of Kinetic Parameters by Genetic Algorithm

Studies about kinetics and modeling of production parameters for biosurfactants are essential to the development of efficient processes from an economic point of view. In this sense, this work evaluated the performance of four nonstructured models to explain the experimental data for biomass growth, substrate consumption, and rhamnolipid production using glycerol as carbon source and a Pseudomonas aeruginosa strain. The kinetic parameters of each model were estimated using a global search method known as genetic algorithm and numerical discretization of differential equations by the Runge–Kutta 4th order method. The main result of this study showed that the Monod model best represented the experimental data, with μ_max values of 0.06 h⁻¹, K_S of 50.8 g L⁻¹, Y_X/S of 0.43 g g⁻¹, and Y_P/X equal to 0.017 g g⁻¹.     

CORN GLUTEN HYDROLYSIS BY ALCALASE: KINETICS OF HYDROLYSIS

In the present study, the reaction kinetics of corn gluten hydrolysis by Alcalase, a bacterial protease produced by Bacillus licheniformis, was investigated. The reactions were carried out for 10 min in 0.1 L of aqueous solutions containing 10, 20, 30, 40, and 50 g protein L^?1 corn gluten at various temperature and pH values. The amount of enzyme added to the reaction solution was 0.25% (v/v). Also, to determine decay and product inhibition effects for Alcalase, a series of inhibition experiments were conducted with the addition of various amounts of hydrolysate. For each experimental run, both the amount of hydrolysis (meqv L^?1) and the soluble protein amount (g L^?1) were investigated with respect to time, and the initial reaction rates were determined from the slopes of the linear models that fitted to these experimental data. The kinetic parameters, K_m and V_max were estimated as 53.77 g L^?1 and 5.94 meqv L^?1min^?1. The type of inhibition for Alcalase was determined as uncompetitive, and the inhibition constant, K_i, was estimated as 44.68% (hydrolysate/substrate mixture).     

LONG TERM MONITORING OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) IN BLUE MUSSELS (Mytilus edulis) FROM A REMOTE SCOTTISH LOCATION

Farmed mussels have been collected on a monthly basis since 1999 from a remote site on the west coast of Scotland for polycyclic aromatic hydrocarbon (PAHs) analysis with the aim of establishing background concentrations as a benchmark against which to assess any environmental incident. Total PAH (2- to 6-ring parent and alkylated) concentrations ranged from 12.5 to 151.2 μg kg^?1 wet weight. Seasonal trends were evident with concentrations being significantly higher for samples collected between November and March compared to those collected between April and October. By taking the median of medians for each of these time periods two background concentrations are suggested for the total PAH concentrations (2- to 6-ring PAHs parent and alkylated); for April to October: 31.2 μg kg^?1 wet weight and for November to March: 62.9 μg kg^?1 wet weight. Individual PAH concentrations were mainly below the OSPAR Background Assessment Concentrations (BACs), where they are specified, and were only exceeded for the heavier 4- and 5-ring PAHs (fluoranthene, pyrene, benz[a]anthracene and benzo[a]pyrene) in samples collected between November and March. Differences were also seen in the PAH profiles with season. Mussels collected between November and March had a higher proportion of the heavier PAHs compared to mussels collected in the summer and autumn.     

Surface Chemical Properties and Micellization of Disodium Hexadecyl Diphenyl Ether Disulfonate in Aqueous Solution

The surface tension of disodium hexadecyl diphenyl ether disulfonate (C₁₆‐MADS) was measured at different NaCl concentrations (0.00–0.50 mol L^?1) and temperatures (298.0–318.0 K) using the drop‐volume method. The results show that, with increasing temperature, the critical micelle concentration (CMC) of C₁₆‐MADS increases slightly, but the maximum surface adsorption capacity (Γ_max) at the air–water interface decreases. When the concentration of NaCl was increased from 0.00 to 0.50 mol L^?1, the CMC of C₁₆‐MADS decreased from 1.45 × 10^?4 to 4.10 × 10^?5 mol L^?1, but the surface tension at the CMC (γ_cmc) was not affected. When the concentration of NaCl was increased at 298.0 and 303.0 K, the Γ_max of C₁₆‐MADS increased. When the temperature was increased from 308.0 to 318.0 K, the surface excess concentration (Γ_max) of C₁₆‐MADS abnormally decreased from 2.26 to 1.41 μmol m^?2 with increasing NaCl concentration. The micellization free energy () decreased from ?63.98 to ?76.20 kJ mol^?1 with increase of temperature and NaCl concentration. The micellar aggregation number (N_m) of disodium hexadecyl diphenyl ether disulfonate (C₁₆‐MADS) was determined using the molecule fluorescence probe method with pyrene as probe and benzophenone as quencher. The results show that an appropriate N_m could be measured only at surfactant concentration above the CMC. The N_m increased with an increase in C₁₆‐MADS concentration, but the micropolarity in the micelle nucleus decreased. The temperature had little effect on N_m. Compared with typical single hydrophilic headgroup surfactants, aggregates of C₁₆‐MADS exhibit different properties.     

Seasonal and Spatial Variation of Polycyclic Aromatic Hydrocarbons in Vapor-Phase and PM2.5 in Southern California Urban and Rural Communities

Fifteen priority polycyclic aromatic hydrocarbons (PAHs) were measured in two rural communities (Atascadero and Lompoc) located several hundred km northwest of Los Angeles and in four urban communities 40–100 km downwind of Los Angeles (San Dimas, Upland, Mira Loma, and Riverside), during all seasons, from May 2001 to July 2002. PM_2.5 and vapor-phase PAHs were collected, on prebaked quartz fiber filters and PUF-XAD-4 resin, respectively, at 113 LPM, during 24 h periods, every eighth day, and quantified by HPLC-Fluorescence. At all sites vapor-phase PAHs contained > 99.9% of the total PAH mass and were dominated by naphthalene (NAP), which varied from about 60 ng m ^{? 3} in Lompoc, a community with light traffic, to ～580 ng m ^{? 3} in Riverside, a community traversed by ～200,000 vehicles day^{? 1}. During summer pollution episodes in urban sites, NAP concentrations reached 7–30 times annual averages. Except for summer episodes, concentrations of low MW PAHs showed small seasonal variations (～2 times higher in winter). Similar concentrations of particle-phase PAHs were observed at all sites except for Lompoc. Benzo[ghi]perylene (BGP), a marker of gasoline exhaust emissions, showed the highest concentration among particle-phase PAHs, varying from 23.3 pg m^?3 in Lompoc to 193 pg m^?3 in Mira Loma. Benzo[a]pyrene and indeno[1,2,3-cd]pyrene, found exclusively in the particle phase, were much higher in urban sites (～40–100 pg m^?3), than in Lompoc (～12 pg m^?3). Winter particle-phase PAHs were 2 to 14 times higher than summer levels. Particle-phase PAHs were negatively correlated with mean air temperature in urban sites (r = ?0.50 to ?0.75), probably resulting from surface inversions occurring during winter. The data suggest that in Southern California vehicular exhaust emissions are a major contributor to particle-phase PAHs.     

A new pH‐based procedure to model toxic effects on nitrifiers in activated sludge

A combination of a titration experiment and a biokinetic parameter estimation procedure is proposed as an experimental tool to study the kinetics of NH₄⁺‐oxidizing bacteria in activated sludge. The method was used to quantify the effect of low concentrations of a toxic compound on the maximum substrate removal capacity and the substrate affinity constant (K_NH) of NH₄⁺‐oxidizing bacteria in activated sludge samples. Experiments in the presence of increasing concentrations of a toxic compound (CN⁻, 3,5‐DCP, Cu²⁺ and phenol) were performed with nitrifying activated sludge samples obtained from two full‐scale wastewater treatment plants. The repeatability of the proposed procedure was found to be sufficient to deduce trends in the behavior of the NH₄⁺‐N‐oxidizing bacteria based on one series of experiments with increasing toxicant concentrations. The experimental results showed that the two sludge samples reacted completely differently in the presence of a certain concentration of the same toxic compound. For phenol, the shape of the titration curves did not correspond any longer to a simple Monod model. In this case, titration curves could be described by a model including both nitrification inhibition by phenol and degradation of the phenol by heterotrophic bacteria. © 1999 Society of Chemical Industry     

HYDROCARBON POLLUTION ALONG MOROCCAN COASTS AND BPH ACTIVITY IN THE MUSSEL PERNA PERNA

Specimens of the mussel Perna perna were collected along Moroccan coasts to determine the concentrations of polycyclic aromatic hydrocarbons (PAHs) bioaccumulated in the tissues, and to measure benzo[a]pyrene hydroxylase (BPH) activity. Chemical analysis of PAHs show that the Mediterranean (Nador, Martil, Tanger) and central Atlantic coasts (from Rabat to Jorf Lihoudi) are those most contaminated (351 245 ng.g^{? 1} dry weight in Tanger). The mussel contaminants were of mixed origin for most of the locations with non negligible inputs of petrogenic origin in many of them. Baseline levels of PAHs were between 6 and 55 ng.g^{? 1} dry weight. BPH activity showed significant correlation (r _s = 0.64, P < 0.05) with total PAH concentrations at the six most contaminated stations. The baseline level of BPH activity can be identified as in the range 0.1 to 13 pmol.min^{? 1}.mg prot^{? 1} along the Mediterranean and Atlantic coasts.