Fernando Mirada

Solubilities of hydroquinone and p-quinone in supercritical carbon dioxide

The solubilities in binary and ternary systems of hydroquinone (1,4-dihydroxybenzene) and p-quinone (1,4-benzoquinone) in supercritical carbon dioxide were measured in the pressure range 10.0 to 35.0 MPa at temperatures of 333, 348 and 363 K. In binary systems, the solubility of hydroquinone was three orders of magnitude lower than that of p-quinone. This difference in solubility was lower in the ternary system because the solubility of hydroquinone increases, while the solubility of p-quinone decreases. The measured solubilities in the binary and ternary systems were correlated using a semiempirical model proposed by Bartle.

Effect of Cu2+ , Ni2+ and Zn2+ on an anaerobic digestion system

Abstract This paper reports the characterization of an anaerobic digester in relation to minimun levels of copper, nickel and zinc, separately and mixed, which it can receive and the effects these give rise to on stability, depuration efficiency and methane production. The experiments were carried out on complete mixture laboratory scale digesters.

Site best suitable for the disposal of urban solid waste

Abstract Sanitary landfill is an enginereed method of disposing of solid waste on land in a manner that protects the environment, by spreading the waste in thin layers, compacting it to the smallest practical volume, and covering it with compacted soil by the end of each working day or at more frequent intervals if necessary. Sanitary landfill are and will continue to be the principal method of urban solid waste (U.S.W) disposal becouse the relatively inexpensive equipment required to operate and the possibility to reuse the site once the landfill has been sealed and shut. The aspect more relevant to take account when this tecnhique is used is the location of the disposal area. This works analyzes the more important factors to be taken account when selecting the site best suitable for the disposal of U.S.W. Environmental impact, life span, access, transport, exploitation, sealing and shutting are analized and a final valuation is made in order to show recommendations that may be needed to select the best ...

Copper (2+), Zinc (2+), and Nickel (2+) Uptake by Activated Sludge

Abstract This paper reports the results obtained on copper, zinc, and nickel uptake by activated sludge in a completely mixed unit. Removal of these heavy metals from wastewater occurs by uptake and by precipitation, the latter being particularly important in the cases of copper and zinc. The amount of heavy metal taken up by the microorganisms at equilibrium varies with influent concentration for the three metals studied. The values obtained range from 2.3 mg/g VSS for copper at 1 mg/L in the influent to 57.4 mg/g VSS for nickel at influent 25 mg/L. Soluble metal removal from wastewater increases in percentage with influent concentration, being higher for copper and lower for nickel. Experiments with mixtures of these metals have also been carried out.

Copper (2+), zinc (2+), and nickel (2+) effects on activated sludge

Abstract This paper presents a study on the effects of ‐Cu (2+), Zn (2+) and Ni (2+) in activated sludge, focussing on their influence in COD removal efficiency. Experiments have been done at different heavy metals ‐concentrations varying from 1 to 25 mg/1. Cu (2+) exhibits the higher detrimental effect, followed by Zn (2+) and Ni (2+). Mixtures of these heavy metals show a less than a less than additive effect.

The Influence of Sludge Age on Copper (2+) and Chromium (3+) Uptake by Activated Sludge

Abstract This paper reports the results obtained on Cu2+ and Cr3+ uptake by activated sludge of 7 and 12 d sludge age. Removal efficiencies of these heavy metals decrease when their initial concentrations increase. For the Cu2+, sludges of lower age adsorb 12% less over the range of the metal concentration added. The Cr3+ adsorption was a function of both sludge age and initial concentration. For an initial concentration of 32 mg/L, both sludges gave identical removals. The stability of bound, metal-activated sludge increases when the sludge age increases for Cu2+. The opposite effect has been noted with Cr3+.

EVALUATION OF A PROTEASE ASSAY BASED ON A NATURAL PROTEIN FOR HEAVY METALS INHIBITION OF ACTIVATED SLUDGE

An enzymatic assay employing 2,4,6-trinitrobenzenesulfonic acid to follow the hydrolysis reaction of peptide bonds of a natural protein by activated sludge was evaluated for assessing the inhibition caused by heavy metals on biological treatment processes. The individual and joint effects up to 20 mg/l of Cu(II) and Zn(II) on activated sludge of different ages (6, 10 and 14 days) between a pH range from 6 to 7 was investigated by means of a 24 factorial experimental design. From statistical results, it has been concluded that not only the four main effects of these variables have an important influence on protease activity of activated sludge but also some interactions among them. Experimental data showed that Zn(II) was less inhibitory towards proteases than Cu(II) and that their joint effects acted neither synergistically or antagonistically. Sludge age was the variable that more strongly affected the protease activity of activated sludge.

Activated sludge treatment of waste water contaminated with heavy metals: Advantages of the use of sepiolita into the biological units

Abstract This paper reports the results obtained in an activated sludge pilot plant: 10 mg/l of Cu (2+) or 10 mg/l of Cr (3+) were added to the wastewater feed at the same time that different amounts of sepiolita were introduced into the aeration tank of the biological unit. The system behaviour was focussed through the evolution COD removal efficiency and the metal concentration, both in the effluent and in the activated sludge. The operation conditions used were fixed for the highest COD removal efficiency of system obtained without both, metal and sepiolita, therefore it was operated with mean‐cell residence time incluided within 7 and 13 days. The results obtained show that the sepiolita addition even in small quantities allows to keep and, in same cases, to improve the system efficiency related to the organic matter and metal removal.