Bioremediation of pesticides in surface soil treatment unit using microbial consortia

The manufacturing and use of pesticides has been rising tremendously in India. The waste generated by the pesticide industry has become an environmental problem due to the present insufficient and ineffective waste treatment technology involving physico-chemical and biological treatment. The available data indicates that pesticide residues remain in surface soil, leading to toxicity in the soilwater environment. The recent advances in bioremediation technology using microbial consortium has been found effective for treatment of pesticides in soil. In the present study, a Surface Soil Treatment Unit has been designed wherein bioremediation of commonly used pesticides namely chlorpyrifos, cypermethrin, fenvalerate, and trichlopyr butoxyethyl ester at varying concentration viz. 25, 50 and 100 mg/kg have been carried out using cow-dung microbial consortia under simulated environmental conditions. The bioremediation conditions have been monitored and maintained during the study. The investigation has been extended till the parent compound was converted into intermediates and/or less harmful compounds. These then will further mineralize, from part of the microbial food chain and/or become integrated into the humic fractions. The results presented here highlight the potential of cowdung slurry consortia for bioremediation of soil contaminated with pesticides in surface soil treatment unit.Key words: Bioremediation, surface soil treatment unit, pesticides, cow-dung, microbial consortia

Remediation of anthracene in mycorrhizospheric soil using ryegrass

Rhizosphere bioremediation has become an effective technique that uses green plants to enhance biodegradation of persistent organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), pesticides and radionuclides. Polycyclic aromatic hydrocarbons, due to their hydrophobic nature were found to be retained in the soil. Plants could be grown at the PAH contaminated sites to stimulate the biodegradation in the rhizosphere. In the present study, biodegradation of anthracene was studied using ryegrass in mycorrhizosphere soil by laboratory scale pot culture experiments. Ryegrass (Lolium multiflorum) was grown in pots containing soil contaminated with various levels of anthracene. Soil and plants from treated pots were sampled after 15, 30, 45 and 60 days and compared with uncontaminated planted pots. In the mycorrhizosphere, the concentrations of anthracene in the soil were found to be 5.2, 7.88, 15.43, 33.23 and 41.5 mg/kg at the 15 days harvest which further decreased to 0.31, 0.45, 0.89, 1.89 and 2.43 mg/kg over a period of 60 days when exposed to the initial concentrations of 10, 25, 50, 75 and 100 mg/kg amended in soil, respectively. Plant shoot and root dry biomass were observed to be significantly reduced at higher anthracene concentrations (75 and 100 mg/kg) whereas low concentrations had no distinct effect on plant biomass (p<0.05). The increase in the microbial counts was also monitored and quantified along the degradation of the anthracene in the soil. The findings of this research show that there is rapid degradation of anthracene under the influence of ryegrass mycorrhizosphere.Key words: Rhizosphere bioremediation, Lolium multiflorum, arbuscular mycorrhizal fungi, PAHs