Environmental Technology

Lebourg, A.; Sterckeman, T.; Ciesielski, H.; Proix, N.; Gomez, A.

doi: 10.1080/09593331908616678pmid: N/A

Soil trace metal extractability by 0.01 mol l−1 CaCl2, 0.1 mol l−1 NaNO3 and 1 mol l−1 NH4NO3 solutions is very low. The hypothesis, according to which the saturation of extracts limits the concentrations in solution, was tested by the study of polluted soils. Thus, according to our calculations, cadmium and copper did not precipitate as carbonates, hydroxides and phosphates. In contrast, zinc might precipitate as phosphate, lead as carbonate, hydroxide, sulfate and phosphates. The influence of such phenomena on the estimation of Pb bioavailability was tested by studying the lead uptake of radish plants cultivated in sandy soils artificially enriched with lead. It was then demonstrated that the saturation of the solutions did not in these conditions allow the evaluation of lead bioavailability using such chemical extractions.

Pareek, S.; Matsui, S.; Kim, S. K.; Shimizu, Y.

doi: 10.1080/09593331908616679pmid: N/A

The degradation of cellulosic and lignocellulosic waste was investigated in the simulated landfill column reactors, under sulfidogenic and methanogenic conditions. Competition between SRB and MPB was steered to optimum sulfate reduction and thus suppress the methane production in phase V of waste stabilization, where methane composition of biogas decreases and economical methane use is not feasible. In addition to the control of methane gas production, carbon dioxide emission was also reduced in sulfate reducing reactors. In vial batch experiment the hydrolysis rate constant of Avicel cellulose in sulfate reducing culture was 1.44 times higher than that in methanogenic culture. Results from carbon balance in vial experiments showed that carbon mineralization in sulfate reducing vial sets was 2–5 times higher for various cellulosic and lignocellulosic material than in methanogenic vial sets.

Peppiatt, C. J.; Shama, G.

doi: 10.1080/09593331908616680pmid: N/A

A novel UV photoreactor based on the principle of a water bell had been shown in earlier studies to be effective in disinfecting liquids of high UV absorptivities. The water bells were produced using a nozzle in which an annular jet was made to impact on a plane disc. Photographs taken of bells produced in this way were overlayed with the outlines of bells as predicted by the hydrodynamic model of Lance and Perry [1] and showed good agreement. The hydrodynamic bell model was coupled with a volumetric emission model in order to determine the UV dose delivered to the bell by a single UV source located centrally inside the bell. The value obtained using this model, and including a correction factor to account for the UV absorption of the quartz thimble shrouding the UV source, was 0.43 mW-s.cm−2at a flowrate of 650 1 hr−1 which compared with a value of 0.31 mW-s.cm−2 obtained using potassium ferrioxalate actinometry and with a value of 0.43 mW-s.cm−2 obtained from a direct measurement of UV intensity using a radiometer. The combined model was used to predict the effect of changing the principal nozzle characteristic-the nozzle gap opening- on bell profile, UV dose and thickness of the water film comprising the bell.

Jinda, R.; Fujii, S.

doi: 10.1080/09593331908616681pmid: N/A

A mathematical model of rock-bed filtration process was formulated and a numerical computation scheme was developed. Eight physical and biological processes, namely, reaeration, sedimentation of organic and inert particulate matter, oxic decomposition of dissolved organic matter, nitrification, and oxic, anoxic, and anaerobic decomposition of organics in sediments were incorporated in the model. The functions describing the qchange in concentrations of six water quality indices and two sediment fractions were obtained from the conversion rate functions based on the IAWPRC approach in a matrix format. The respective differential equations were then solved sequentially using the numerical solution scheme with known initial conditions for a given time step along the reactor length. The simulated changes in the concentrations of water quality indices and sediment fractions were compared with the results of the Inagawa river project for evaluating the model performance. It was possible to obtain a reasonable agreement between the simulated and observed results through the adjustment of kinetic and stoichiometric parameters. The model predicted results for the long term performance of rock-bed filtration systems for four selected cases and indicated that the method could be suitable for the treatment of low strength wastewaters.

Shin, H. S.; Lee, S. M.

doi: 10.1080/09593331908616682pmid: N/A

The removal of ammonia nitrogen and phosphorus from wastewater by precipitating out with magnesium salts was showed. Factors of pH, reaction time, N/P ratio, and dissolution test were investigated to find optimal conditions for magnesium ammonium phosphate (MAP) formation. The investigated conditions were also applied to toxic industrial wastewater. SEM and EDS analyses indicated that the precipitate was magnesium ammonium phosphate that was fine crystals of Mg and P compounds. The removal of ammonia and phosphorus increased with pH up to 10.5 where 82.6% and 97% of ammonia nitrogen and phosphorus were removed. It was found that minimum 10 minutes reaction was required for the nutrients removal. However, a small amount of phosphorus dissolved after 60 minutes. Ammonia nitrogen was well removed at one mole to two moles of magnesium. But at doses higher than two moles of magnesium, ammonia nitrogen increased due probably to the decreased pH. Bittern and sea water proved to be excellent coagulants for nutrient removal from industrial wastewater. The comparative study of different magnesium sources showed that bittern was the most efficient as 72% 99% of ammonia and phosphorus, respectively, were removed.

Kim, K. W.; Lee, H. K.; Yoo, B. C.

doi: 10.1080/09593331908616683pmid: N/A

An investigation was made of the degree and extent of heavy metals in tailings, stream waters, sediments, soils and crop plants in the Yugu-Kwangcheon Au-Ag Province, comprising the Gubong, Daebong and Samgwang mines. As a result of mining activity, average concentrations of Cd, Cu, Pb and Zn in the stream sediments from the Gubong and Samgwang mine areas are significantly higher than the standard levels. In order to give the sufficient information for an estimate of the hazard potential stored in these geological materials, the use of a pollution index is suggested, and it decreases in order of Gubong > Samgwang > Daebong mine areas. Average concentrations of Cd and Pb in paddy/farm soils in the Gubong area are highest ranging up to 8.2 µg g−1 Cd and 192 µg g−1 Pb, and Pb concentrations in rice grain and sesame from these soils range up to 0.4 µg g−1 and 6.8 µg g−1.

Leu, H. G.; Lin, S. H.; Shyu, C. C.; Lin, C. M.

doi: 10.1080/09593331908616684pmid: N/A

Aeration using fine bubble membrane aerators in a tank of 2 m height was investigated. The performances of the aeration system were assessed in terms of oxygen mass transfer coefficient (kLa). Experiments were conducted to examine the effects of air flow rate, pH and water depth in the aeration tank on the mass transfer coefficient. The mass transfer coefficients for the present fine bubble membrane aerator and the conventional coarse bubble type were compared. Also investigated were the effects of several anionic surfactants and SS simulated by using kaolin and diatomaceous earth on the oxygen mass transfer coefficient. An attempt was made to account for the effects based on theories proposed by previous investigators. Finally, based on the experimental results, optimum operating conditions for the present fine bubble aeration system were identified.

Obrador, A.; Rico, M. I.; Alvarez, J. M.; Mingot, J.

doi: 10.1080/09593331908616685pmid: N/A

The use of sewage sludge for agricultural use is regulated in the European Community, but there is potential for its use as an organic substrate for the cultivation of ornamental plants in containers, providing phytotoxic levels are not exceeded. Mixtures of a sludge with high concentrations of Cr and Zn and two soils were prepared at sludge:soil ratios of 1:1 and 1:10 (w:w) and incubated at ambient temperature for up to one year. Metal extractability was assessed at various times using a sequential fractionation procedure. Soil type and sludge:soil ratio influenced cation (Cr, Cu, Mn, Pb, Zn) mobility between the different chemical fractions. In general, there was an increase in the potentially bioavailable fraction of all cations at the beginning of the incubation period which then remained more or less constant or decreased, over the rest of the period. Average values for the potentially bioavailable fraction as a percentage of the total metal present during incubation varied from 0.71% for Cr to 37.35% for Zn. The extractability of all metals except Cu was influenced by the soil type. Increases in the amount of sludge added led to increases or decreases of bioactivity depending on the cation.

Chakravarty, R.; Prasad, G.; Raupainwar, D. C.

doi: 10.1080/09593331908616686pmid: N/A

This study examines the adsorption characteristics for the removal of copper (II) from aqueous solution using natural hematite which is available in abundance in this country. The static characterisation of the kinetics of the adsorption process has been studied using batch experiments at different adsorbate/adsorbent ratios for pH for fixed ionic strength. Adsorption isotherms have been modelled with the help of both Langmuir and Freundlich formulae. The dependence of the adsorption of the metal ion on the pH of the solution has been studied to achieve a better understanding of the adsorption mechanism. It has been found that maximum adsorption of Cu(II) from aqueous solution takes place at a pH value of 8.0. It has been concluded that the adsorption process comprises monolayer adsorption followed by intraparticle diffusion.

de Velásquez, M. T. Orta; Manero, O.; Cardoso, J.; Martínez, G.

doi: 10.1080/09593331908616687pmid: N/A

In this work, new polymeric flocculants are presented for use in water-treatment operations. Efficiencies are reported from results obtained by conventional bench-scale tests. These tests are carried out in three systems: a bentonite suspension, biologically treated wastewater effluents and chemically treated effluents. The polymers are water-soluble moieties of the zwitterionic type, which present considerable chain expansion in the presence of high ionic strengths or high salinity, in contrast to the behavior exhibited by common polyelectrolytes. In the case of biologically treated wastewater, 87% of turbidity removal is obtained with the polymer alone. In the case of chemically treated mixed industrial wastewater, the new polymers are compared with cationic and anionic polymers. This work illustrates that high efficiencies may be obtained using anionic or zwitterionic polymers. With 0.2 mg l−1 of zwitterionic polymer and 20 mg l−1 aluminum sulfate, removals of 38% and 96% in chemical oxygen demand (COD) and total suspended solids (TSS), respectively, can be obtained. For Mexico City's wastewater flow, the highest efficiencies are obtained with 250 mg l−1 of Ca(OH)2 and 0.1 mg l−1 of zwitterionic polymer (48% COD and 87% TSS). In this particular case good results are also obtained using anionic flocculants with aluminum sulfate.