Environmental Technology

Marshall, W. E.; Wartelle, L. H.; Boler, D. E.; Toles, C. A.

doi: 10.1080/09593332108618075pmid: N/A

Soybean hulls, extracted with 0.1 N NaOH (BE) and modified in the presence of 0.6 M citric acid (CA), were compared to similarily treated peanut shells and the hulls of almonds, cottonseed and macadamia nut for their ability to adsorb copper ion (Cu2+) as a typical metal ion. BE, CA-modified soybean hulls had the highest metal ion adsorption but similarly treated almond hulls had the highest total negative charge. BE, CA-modified soybean hulls also were compared to BE hulls modified in the presence of 0.6 M concentrations of four different dicarboxylic acids (maleic, malic, succinic, tartaric) for their copper ion adsorption potential. Hulls modified with CA had the highest adsorption of copper ion by virtue of their largest total negative charge. Adsorption capacities and affinity constants for the metal ions cadmium (Cd2+), copper (Cu2+), nickel (Ni2+), lead (Pb2+) and zinc (Zn2+) were determined for BE, CA-modified hulls at pH 4.8. Adsorption capacities for all ions were greater than 1.0 mmol g−1 hull. These hulls were compared to two commercial cation exchange and two commercial chelating resins for adsorption of the five metals at three metal ion concentrations either in a solution containing all five ions or as individual metals. When all five metal ions were present at the highest concentration (7 mM), modified soybean hulls removed more metal ions than any of the commercial products. For individual metal ions, all adsorbents generally were quite effective at metals removal at the three concentration levels. Our comparative results demonstrate that modified soybean hulls have excellent metals removal properties and can be considered as a product with possible commercial potential for metal ion remediation.

Denizli, A.; Büyüktuncel, E.; Tuncel, A.; Bektas, S.; Genç, Ö.

doi: 10.1080/09593332108618079pmid: N/A

Polyethyleneglycolmethacrylate [PEG-MA] gel beads (100-120 µm in diameter) carrying Cibacron Blue F3GA (42.6 µmol g−1 polymer) were prepared for the removal of Pb(II) ions from aqueous solutions containing different amount of these ions (10-600 mg l−1) and at different pH values (2.0-6.4). Pb(II) adsorption capacity increases with the time during the first 20 min and then levels off toward the equilibrium adsorption capacity. Adsorption of Pb(II) ions on the unmodified PEG-MA gel beads was zero. Cibacron Blue F3GA-immobilisation significantly increased the Pb(II) adsorption (23.3 mg g−1 polymer). Langmuir adsorption model was found to be applicaple in interpreting lead adsorption by Cibacron Blue F3GA-immobilised PEG-MA gel beads. The adsorption of Pb(II) ions increased with increasing pH and reached a plateau value at around pH 5.0. The optimal pH range for Pb(II) adsorption was shown to be from 5.0 to 6.0. PEG-MA gel beads can be regenerated by washing with a solution of nitric acid (0.1 M). The maximum regeneration value was as high as 98%. These PEG-MA gel beads are suitable for repeated use for more than three adsorption-desorption cycles without considerable loss of adsorption capacity.

Carvalho Dos Santos, M.; Lenzi, E.

doi: 10.1080/09593330.2000.9618946pmid: N/A

The use of aquatic macrophytes (Eichhornia crassipes) as a biological filter in the elimination of lead from industrial effluents was tested experimentally in greenhouses. Variables studied and optimized were ratio (r) mass of wet water hyacinth in grams per volume of contaminated solution in liters where it was found that the best intervals ranged from 40 to 50 g l−1, best value of lead concentration in contaminated solution in which water hyacinth had greater de-pollution efficiency up to 30 mg l−1; the first 12 hours constitute the best period of contact of water hyacinth with solution. The method was applied to an effluent of a battery industry. Acid pH of effluent was corrected to 7, temperature ranged from 20°C to 25°C, at 1 atm. After neutralization of effluent (4.45 mg l−1) lead concentration was removed with 99% efficiency when optimizing conditions were achieved.

Kochany, J.; Lugowski, A.

doi: 10.1080/09593332108618085pmid: N/A

The paper presents the results of treatability studies on high strength landfill leachate (COD=7880 mg l−1; TOC = 2360 mg l−1; NH3−N=590 mg l−1). During the studies physicochemical methods, biological treatment and an ozonation were tested. Optimization of treatment using each treatment method was performed. It has been determined that preaeration of leachate with 50 mg l−1 of phosphoric acid, followed by biological treatment (anaerobic and aerobic) and ozonation achieved removal of 99.6 % of ammonia and 92 % of COD. The treatment system produced the high quality effluent, suitable for discharge to the surface water.

Hers, I.; Zapf-Gilje, R.; Li, L.; Atwater, J.

doi: 10.1080/09593330.2000.9618948pmid: N/A

Vadose zone in situ diffusion coefficients were measured at a former petrochemical plant (Chatterton research site) using a push-pull test and helium tracer. The test is relatively simple to perform, utilizes relatively inexpensive materials and field equipment, and requires only a few hours to complete each series of tests. In situ diffusion coefficients are derived using an analytical solution for spherical diffusion from a point source, assuming instantaneous injection of the tracer. The results of push-pull tests conducted at the Chatterton research site indicate that measured effective diffusion coefficients in sand fill with moisture content between 5 and 12% (by weight) ranged from about 0.01 to 0.07 cm2sec−1. A good comparison was obtained between the measured gas-phase tortuosity and that predicted using a common empirical relationship, with measured tortuosity factors consistently being about twice the predicted values. While further comparisons need to be conducted for various moisture contents and different soil types, the results of this study suggest that the push-pull test is an effective tool for estimating diffusion coefficients and can be used to validate empirical relationships for diffusion coefficient.

Boukhars, L.; Rada, A.

doi: 10.1080/09593332108618081pmid: N/A

The aim of this study was to determine cadmium availability in soils collected from the future sewage spreading field in Marrakesh city (Morocco). These agricultural soils are characterised by significant salinity due to the proximity of the Tensift river. The investigation was conducted under arid climatic conditions using a pot procedure. The effect of various cadmium origins (raw wastewaters (EUB), treated wastewaters (EUT), sludge (B) and Cd(NO3)2 on the plant availability according to a salinity gradient, was determined, using lettuce (Lactuca sativa L var pommée d'été) and rye-grass (Lolium perenne L var Maprima). The dry weight yield of plant leaves and roots produced on salt soil treated with B, EUB and EUT was relatively stable. However, it decreased by about 50 % with the addition of Cd(NO3)2 and Cd(NO3)2+EUB except for rye-grass. The lettuce cultivated on salty soils showed a yield decrease of 38.9 to 79 % and 38 to 69.6 % (leaves) respectively in proportion to non and little salted soils. Addition of cadmium salt to the soils induced a more important bioaccumulation than for other forms. The Cd(NO3)2 supply was taken up much more than the sludge-borne cadmium. This tendency increases further after culture irrigation with EUB (Cd(NO3)2 + EUB, treatment). The concentrations ranged between 3.15 to 8.23; 2.16 to 2.88 and 3.83 to 8.88 mg Cd kg−1 in the lettuce leaves for the treatments and from 2.49 to 7.83; 1.54 to 2 and 3.09 to 8.61 mg Cd kg−1 in its roots, according to the gradient of salinity. Furthermore, the concentration of Cd accumulated in plants on the sludge-treated soils could be due to increased growth of plant resulting from the fertilising power of sludge. Increase in plant metal uptake for all treatments coincided with increase in soil salinity. Thus, the highest concentrations recorded in leaves increased approximately two fold with an increase of about 1.6 times of the salt concentration estimated in terms of soil chloride (Cl) amounts. A positive and significant correlation was found between the cadmium concentration in the test plants and the amounts of chlorides in the soils (threshold 0.1 %). For cadmium uptake by plants, the extraction of cadmium by CaCl2 (0.1 M) was more important in soils supplied with cadmium salt. Likewise, the extracting quantities were substantially higher in soils with elevated chlorides concentrations. It was in the order of 1.2 compared with 0.7 mg exchangeable Cd kg−1 in the non-salted soils. These data suggest that the possible formation of CdCln n−2 compounds can facilitate the plant exposure to cadmium and so its accumulation into edible plant parts.

Robins, J. P.; Rock, J.; Hayes, D. F.; Laquer, F. C.

doi: 10.1080/09593332108618076pmid: N/A

The purposes of this study were i) to show that nitrate removal by denitrification from Platte Valley, Nebraska synthetic groundwater was possible utilizing a model, laboratory-scale, constructed wetland (MW) and ii) to evaluate the MW's influence on water quality when the hydraulic retention time (HRT) was varied. Denitrification was successfully achieved using a starch and cellulose mixture as the carbon source, instead of carbon from plant growth, and a 30 mg l−1 nitrate-nitrogen synthetic feed concentration. For 1, 3, and 7 day HRTs, the MW achieved nitrate-nitrogen plus nitrite-nitrogen (nitrate/nitrite-nitrogen) removals of 82%, 98%, and 88%, respectively. The effluent nitrate/nitrite-nitrogen levels were not significantly different, based on their 95% confidence intervals. For all HRTs, average effluent organic-nitrogen concentrations were less than 2.0 mg l−1 and average effluent ammonia-nitrogen values were less than 0.5 mg l−1. For 356 mg l−1 chemical oxygen demand (COD) addition to the MW, the MW achieved COD removals of 84%, 89%, and 98% for the 1, 3, and 7 day HRTs, respectively. Volatile fatty acid effluent levels were below the detection limit. Residual organic matter in the treated water may make further treatment necessary.

Bigg, T.; Judd, S. J.

doi: 10.1080/09593332108618077pmid: N/A

The use of zero-valent iron in the treatment of hazardous water contaminants is reviewed. The review concentrates on experimental procedures employed in the investigation of a range of applications for zero -valent iron and the efficacy of the processes. Investigations reviewed include those performed with halogenated aliphatic compounds, halogenated aromatic compounds, nitro-aromatic organic compounds, and high-valency toxic metals. Experiments employing bimetallic and cementation reductants as well as zero-valent iron alone are covered. The need for zero-valent iron technology is discussed, as is the need for more rigorous investigation of operational parameters. Despite a paucity of information from the literature it has been shown that efficacy is greatest for well-mixed batch or continuous column systems employing neutral to acidic pH and a high specific surface area of iron. The literature also reveals a need to focus future work on enhancing the chemical reaction taking place on the iron surface in order to enhance the rate of reductive remediation.

Saadi, Z.; Maslouhi, A.; Zeraouli, M.; Gaudet, J.-P.

doi: 10.1080/09593332108618078pmid: N/A

We have developed a simple mechanistic simulation model for predicting in-situ unsaturated water and nitrogen transfers in a large area (7760 ha) located at Mnasra zone. A new physically-based approach was used for determining accurate soil hydraulic properties. It can be applied for surveying large areas using the easily measured soil textural and structural data. The mean hydraulic parameters were used for solving unsaturated water and nitrogen transfer equations. Errors resulting from omitting groundwater flow modelling and spatial variability of the saturated hydraulic conductivity were negligible. Comparison between observed and calculated seasonal groundwater nitrate concentrations, during the expedition of 1992/93 and 1993/94, proved the simulation model performance and that the application rate of 120 kg N ha−1 per annum at agricultural soils should be reduced. The major risk of groundwater contamination were observed during winter which coincided with heavy rainfall and the absence of vegetation cover.

Akhouaou, M.; Srhir, B.; Ammor, H.; Chlihi, K.; Habibi, M.; El Kadiri, M.

doi: 10.1080/09593330.2000.9618953pmid: N/A

The measuring method used for characterizing a material, consists of simulating a coaxial cell containing a material by a formula that connects the filled material cell impedance to its complex permittivity in the area of frequency 100 MHz–4 GHz without establishing an equivalent electrical diagram. The application example proposed is powdered activated carbon, due to its importance in the area of water processing [1, 2]. The dielectric characterization of powdered activated carbon before and after washing by acidic solutions allowed the demonstration of superficial conductivity and dipolar relaxation phenomena; the increase of its conducting properties is clearly demonstrated.