ABSTRACT
Diethylene glycol (DEG) is one of several diols used as a raw material in the production of plasticizers and polyester resins. It has been associated with a number of mass poisonings in several countries. Conventional methods of remediation of DEG contaminated wastewaters are still not very effective. This paper presents an alternative method for remediation of DEG-contaminated waters using the plant Echinodorus cordifolius. The effects of DEG on E. cordifolius were studied along with the plant's efficiency at treating DEG-contaminated wastewater in a constructed wetland. We found that DEG was toxic to the plants with an LD50 of 6238 mg L(-1). The plants exhibited decreased water uptake and showed wilting, chlorosis and necrosis. SEM images showed injury to the cortex tissue. In the constructed wetland, E. cordifolius plants were able to remove and degrade DEG from wastewater, decreasing the pH from 12 to 6.8 and the COD and TDS by approximately 98% and 67%, respectively, in 7 days, while accumulating Ca in the cells.
Subject(s)
Alismataceae/metabolism , Ethylene Glycols/metabolism , Water Pollutants, Chemical/metabolism , Water Purification/methods , Alismataceae/drug effects , Alismataceae/ultrastructure , Biodegradation, Environmental , Calcium/analysis , Ethylene Glycols/toxicity , Hydrogen-Ion Concentration , Microscopy, Electron, Scanning , Oxygen/metabolism , Plant Leaves/drug effects , Plant Leaves/metabolism , Plant Leaves/ultrastructure , Time Factors , Water/metabolism , Water Pollutants, Chemical/toxicity , WetlandsABSTRACT
This work presents the use of the plant Echinodorus cordifolius for remediating diethylene glycol (DEG) contaminated waters. The potential of this plant for treating DEG wastewater in a remediation system was observed. We found that E. cordifolius was able to remove DEG from wastewater, decrease the pH to neutral and remove approximately 95% of the chemical oxygen demand within 12 days. The plants can grow well in DEG wastewater, as indicated by their root and leaf biomass, which was found to be statistically similar to control. Wilting, chlorosis and necrosis were observed in DEG-treated plants, but the relative water content was not significantly different between control and treated plants, suggesting that the plants were able to take up and tolerate DEG present in the wastewater. Plant roots changed to black colour during experimental period. The fluorescence in situ hybridisation and bacterial enrichment confirmed that 4.30 × 10(5) cells/g of sulphate reducing bacteria and 9.30 × 10(8) cells/g of acid-producing bacteria were found associated with the plant roots. Furthermore, volatile fatty acids were found in non-sterile soil treatments, indicating that soil microorganisms are associated with DEG remediation. These results demonstrated that plants and bacteria have the ability to form a relationship to remove the organic contaminant DEG.
