Chemical Reduction of Nitrate by Zero-Valent Iron: Shrinking-Core versus Surface Kinetics Models.

Zero valent iron (ZVI) is being used in permeable reactive barriers (PRB) for the removal of oxidant contaminants, from nitrate to chlorinated organics. A sound design of these barriers requires a good understanding of kinetics. Here we present a study of the kinetics of nitrate reduction under relatively low values of pH, from 2 to 4.

Anaerobic co-digestion of municipal sewage sludge and fruit/vegetable waste: effect of different mixtures on digester stability and methane yield.

The anaerobic co-digestion of fruit and vegetable waste (FVW) and municipal sewage sludge (MSS) is investigated under mesophilic conditions. This was done at a constant hydraulic retention time (HRT) similar to that typically used at waste water treatment plant digesters, 20 days. The effects on digester performance of the FVW:MSS ratio and the organic loading rate (OLR) were examined.

Aging effects on the mobility of Pb in soil: Influence on the energy requirements in electroremediation.

This paper studies the possible differences in the behavior of lead as a contaminant in soil samples when it is present as "naturally-aged" for decades after the contamination, and when it has been spiked in the laboratory. This behavior differences are stablished mainly in two ways: as changes in the fractionation analysis obtained after a sequential extraction procedure (SEP) and as changes in the efficiency of the acid-enhanced electroremediation (EKR) technique. Additionally, aging effects have been studied for almost five years.

Production of biogas from co-digestion of livestock and agricultural residues: A case study.

This study was undertaken to determine the possible changes in the digester yield and performance for the anaerobic co-digestion under mesophilic conditions of strawberry residues (SRs) together with pig manure (PM). The first part of this paper deals with the digestion of SR as a single substrate. For organic loading rates (OLRs) of 4.

Effects of the buffering capacity of the soil on the mobilization of heavy metals. Equilibrium and kinetics.

Understanding the possible pH-buffering processes is of maximum importance for risk assessment and remediation feasibility studies of heavy-metal contaminated soils. This paper presents the results about the effect of the buffering capacity of a polluted soil, rich in carbonates, on the pH and on the leaching evolution of its main contaminant (lead) when a weak acid (acetic acid) or a strong one (nitric acid) are slowly added. In both cases, the behavior of lead dissolution could be predicted using available (scientifically verified freeware) models assuming equilibrium between the solid and the aqueous phase.

Two-dimensional model for soil electrokinetic remediation of heavy metals. Application to a copper spiked kaolin.

A two-dimensional numerical model has been developed to simulate the electrokinetic remediation of soils contaminated with heavy metals and has been validated using laboratory experiments performed with a copper spiked kaolin. The model divides the soil into compartments in a Cartesian grid and a non-conductivity barrier encloses the considered area. Basically, it consists in two main parts clearly distinguishable.

Competitive retention of lead and cadmium on an agricultural soil.

Lead and cadmium contamination of an agricultural soil has been studied using batch and column experiments. Thermodynamics of the retention phenomena may be represented by a Langmuir isotherm for an aqueous metal concentration up to 100 mg L(-1). First order kinetics with respect to the solid phase yield good predictability for both batch and column experiments.