| dc.description.abstract | Organochlorine pesticide (OCP) contamination in groundwater is a problem worldwide, more severely in rural areas that normally cannot afford centralized water treatment systems. Iron nanoparticles have shown their ability to degrade a number of chlorinated organic pollutants in water. However, their practical application as a point-of-use filtration medium is not possible because of their mobility, high cost and unknown/potential toxic effects to human health. In this study, iron turning waste, a common waste material which has the same valence as iron nanoparticles but is ubiquitous and affordable, was experimented to remove individual (batch wise) and mixture of six OCPs (batch and continuous systems) including lindane, heptachlor, endosulfan, dieldrin, endrin, and dichlorodiphenyltrichloroethane from water. The effects of iron turning dose, water pH and initial pesticide concentration, and common minerals in groundwater such as magnesium, sodium, calcium, and nitrate on the removal of the pesticides were examined. Results indicate that pesticide removal increased with the increase of iron dose. Acidic pH favored the removal of the pesticides except endosulfan. Low pH restricted the formation of rust on iron surface resulting in better interaction between iron surface and the pesticides. For endosulfan removal, both hydrolysis and reductive dehalogenation were involved under basic conditions. Common minerals in groundwater had minimal effect on the removal of pesticides. Iron turning waste removed the pesticides more efficiently at higher pesticide concentrations. Iron turning waste media worked better in combination with sand in a filtration column at long empty bed contact time. Iron turning waste first dechlorinated the pesticides followed by ring cleavage and formation of aldehydes. Degradation by-products of all pesticides were far less toxic than the parent pesticides. Shewanella oneidensis, a non-pathogenic environmental bacterium successfully regenerated the exhausted iron turning waste, and the pesticide removal efficiencies of microbially regenerated iron turning were comparable to virgin iron turning waste. This research provides an efficient and affordable method to treat OCPs in water and for the first time elucidates degradation pathways through the identified degradation products and demonstrates utilization of microbially regenerated iron turning waste for OCPs removal. | en_US |
