Contaminated environments in the subsurface and bioremediation: organic contaminants

Due to leakages, spills, improper disposal and accidents during transport, organic compounds have become subsurface contaminants that threaten important drinking water resources. One strategy to remediate such polluted subsurface environments is to make use of the degradative capacity of bacteria. It is often sufficient to supply the subsurface with nutrients such as nitrogen and phosphorus, and aerobic treatments are still dominating. However, anaerobic processes have advantages such as low biomass production and good electron acceptor availability, and they are sometimes the only possible solution. This review will focus on three important groups of environmental organic contaminants: hydrocarbons, chlorinated and nitroaromatic compounds. Whereas hydrocarbons are oxidized and completely mineralized under anaerobic conditions in the presence of electron acceptors such as nitrate, iron, sulfate and carbon dioxide, chlorinated and nitroaromatic compounds are reductively transformed. For the aerobic often persistent polychlorinated compounds, reductive dechlorination leads to harmless products or to compounds that are aerobically degradable. The nitroaromatic compounds are first reductively transformed to the corresponding amines and can subsequently be bound to the humic fraction in an aerobic process. Such new findings and developments give hope that in the near future contaminated aquifers can efficiently be remediated, a prerequisite for a sustainable use of the precious subsurface drinking water resource

Biomimetic and Hemisynthetic Pesticides

Pests are responsible for most losses associated with agricultural crops. In addition, due to the indiscriminate use of synthetic pesticides, several problems have arisen over the years, such as pest resistance and contamination of important planetary sources such as water, air and soil. This awareness regarding pest problems and environment has led to the search for powerful and eco-friendly pesticides that degrade after some time, avoiding pest persistence resistance, which is also pest-specific, non-phytotoxic, nontoxic to mammals, and relatively less expensive in order to obtain a sustainable crop production Biodegradable biomimetic pesticides can be a potential green alternative to the pest industry

Degradation of chlordecone and beta-hexachlorocyclohexane by photolysis, (photo-)fenton oxidation and ozonation

Intensive use of chlorinated pesticides from the 1960s to the 1990s has resulted in a diffuse contamination of soils and surface waters in the banana-producing areas of the French West Indies. The purpose of this research was, for the first time, to examine the degradation of two of these persistent pollutants – chlordecone (CLD) and beta-hexachlorocyclohexane (β-HCH) in 1 mg L−1 synthetic aqueous solutions by means of photolysis, (photo-) Fenton oxidation and ozonation processes. Fenton oxidation is not efficient for CLD and yields less than 15% reduction of β-HCH concentration in 5 h. Conversely, both molecules can be quantitatively converted under UV-Vis irradiation reaching 100% of degradation in 5 h, while combination with hydrogen peroxide and ferrous iron does not show any significant improvement except in high wavelength range (>280 nm). Ozonation exhibits comparable but lower degradation rates than UV processes. Preliminary identification of degradation products indicated that hydrochlordecone was formed during photo-Fenton oxidation of CLD, while for β-HCH the major product peak exhibited C3H3Cl2 as most abundant fragment

Chemical structure investigation of tropical Turbinaria turbinata seaweeds and its derived carbon sorbents applied for the removal of hexavalent chromium in water

International audienceBiomass such as algae, has a great potential to simultaneously deliver renewable energy, bio-products and also better water quality. A pathway towards the realization of these benefits is through the development of valuable materials preferably inexpensive. This work reports on the successful exploitation of Turbinaria turbinata, a brown alga widely available in many tropical areas; which was used as sorbent for the removal of hexavalent chromium from aqueous media. By characterizing the surface material, we showed that the dried alga exhibits several polyfunctional metal-binding sites, enabled to use it as a raw material. Further surface modification (pre-treatment with acid) and structural modification (preparation of both chemically and physically activated carbons) was also carried out to enhance material adsorption properties. Significant improvement of metal uptake (up to 40 fold higher) was obtained, depending of the testing conditions. Based on a close examination of the surface chemistry and pH profiles, a mechanism describing the adsorption mechanism of the different systems was proposed

Chapitre VIII. Les charbons actifs pour le traitement des eaux usées

1. Introduction Les eaux usées d’origine industrielle ou domestique contiennent généralement des composés organiques et/ou inorganiques en concentrations élevées qui peuvent être toxiques. Dans certains cas, elles peuvent aussi contenir des micro-organismes pathogènes. Aussi, ces eaux doivent être traitées par des techniques appropriées avant rejet (Singh et al., 2011). Les méthodes généralement utilisées pour le traitement des eaux usées peuvent impliquer des procédés physiques (décantation,..

Exploring the use of locally produced activated carbon for treatment of chlordecone contaminated animals

International audienceChlordecone (CLD) and γ-hexachlorocyclohexane (γ-HCH) are xenobiotics identified as persistent organic pollutants since 2009. Their presence in water and soils of banana and sugar crops production zones of the Caribbean islands, Guadeloupe and Martinica, led to a long term pollution of soils which is thought to last 5 to 7 centuries for the heaviest polluted andosoils. The National survey plans carried out since 2008 in Guadeloupe and Martinique revealed an unexpected contamination of animal products. This contamination is believed to result from concomitant soil ingestion by animals during pasture. The aim of this project is to formulate and test dietary non-absorbable substances with the aim to bind the compound in order to avoid its absorption or reabsorption. The use of activated carbons (ACs) prepared from biomass and exhibiting specific textural and physico-chemical properties to adsorb chlordecone and to avoid its absorption in the digestive tract, appear to be the most promising approach. Indeed, ACs are for example, widely used in the pharmaceutical industry as antidote in treatment of poisoning. Recent results demonstrated that the use of ACs has the potential to strongly reduce the bioavailability of CLD from soil for rearing animals (pigs and goats). ACs produced from locally available precursors, such as sugar cane bagasse, coconut shell with adequate textural and physico-chemical characteristics will be prepared to optimize these experiments. Two different strategies will be assessed: one performing an amendment of contaminated soil by AC, the other one bringing the AC via an additional feed

Exploring the use of locally produced activated carbon for treatment of chlordecone contaminated animals

International audienceChlordecone (CLD) and γ-hexachlorocyclohexane (γ-HCH) are xenobiotics identified as persistent organic pollutants since 2009. Their presence in water and soils of banana and sugar crops production zones of the Caribbean islands, Guadeloupe and Martinica, led to a long term pollution of soils which is thought to last 5 to 7 centuries for the heaviest polluted andosoils. The National survey plans carried out since 2008 in Guadeloupe and Martinique revealed an unexpected contamination of animal products. This contamination is believed to result from concomitant soil ingestion by animals during pasture. The aim of this project is to formulate and test dietary non-absorbable substances with the aim to bind the compound in order to avoid its absorption or reabsorption. The use of activated carbons (ACs) prepared from biomass and exhibiting specific textural and physico-chemical properties to adsorb chlordecone and to avoid its absorption in the digestive tract, appear to be the most promising approach. Indeed, ACs are for example, widely used in the pharmaceutical industry as antidote in treatment of poisoning. Recent results demonstrated that the use of ACs has the potential to strongly reduce the bioavailability of CLD from soil for rearing animals (pigs and goats). ACs produced from locally available precursors, such as sugar cane bagasse, coconut shell with adequate textural and physico-chemical characteristics will be prepared to optimize these experiments. Two different strategies will be assessed: one performing an amendment of contaminated soil by AC, the other one bringing the AC via an additional feed