Endosulfan, an organochlorine pesticide, is known for its toxicity and ability to accumulate in the environment. In India endosulfan was banned only in 2011 and hence toxic residues are still persistent in the environment. The abilities of three plant species Chittaratha (Alpinia calcarata), Tulsi (Ocimum sanctum), and Lemongrass (Cymbopogon citratus) to remove endosulfan from soil in the absence and presence of zerovalent iron nanoparticles (nZVIs) (1000 mg/Kg of soil), i.e., by phytoremediation and nano-phytoremediation, were determined. Extracted soil samples from the experimental plot were analyzed using Gas Chromatograph with Electron Capture Detector (GC-ECD) and final dehalogenated product was confirmed by Mass Spectrometer (MS). A. calcarata had the best efficiency compared to the other two plant species and the efficiency decreased in the order A. calcarata > O. sanctum> C. citrates. The initial endosulfan removal rate was high (82% was removed within 7 days) when nano phytoremediation experiments were conducted with A. calcarata but then gradually decreased, probably because the activity of nZVI decreased over time. The nZVI endosulfan degradation mechanism appears to involve hydrogenolysis and sequential dehalogenation which was confirmed by GC-MS analysis. Only small amounts of endosulfan were accumulated in the plants because the added nZVIs might have promoted the reductive dechlorination of endosulfan.

The endosulfan-degrading bacterial strain Pseudomonas fluorescens was isolated, and degradation of endosulfan by freely suspended and calcium-alginate entrapped bacterial cells were investigated in batch as well as in packed bed column studies. Freely suspended Pseudomonas fluorescens cells with biomass maximum OD/OD 0 value of 1.68 at 610 nm could degrade endosulfan with an initial concentration of 350.24±0.83 μg/L efficiently within 12 days, thus utilising endosulfan as the sole carbon and energy source. Degradation of endosulfan occurred concomitantly with bacterial growth. The bacteria immobilised in Caalginate beads in batch shake flask system were tested for their ability to degrade endosulfan at different concentrations (350.24±0.83, 450.39±1.95 and 550.85±1.84 μg/L). A total of 125 mL of Broth minimal medium of pH 7 was inoculated with 5 g of wet Ca-alginate beads (derived from a 3-mL cell suspension of 0.72 OD at 610 nm) for the study. Almost similar trends of degradation efficiencies were shown by the immobilised cells toward different concentrations of endosulfan. The complete removal of alpha and beta-isomers of endosulfan at different initial endosulfan concentrations was observed between 9 and 11 days of the experiment. Additionally, the degradation rate in batch reactors with Ca-alginate-immobilised cells also derived from a 3-mL cell suspension of 0.72 OD at 610 nm was tested and found to be marginally higher than that of free cells. Ca-alginate immobilised cells in packed bed reactors operated in a semi-continuous mode could degrade toxic alpha and beta-isomers of endosulfan (350.38±1.18 μg/L) within 6 days. Thus, the method proved effective for biodegradation of endosulfan. The metabolites formed indicated that the degradation of the pesticide follows a hydrolytic pathway.

Endosulfan is a persistent, toxic broad-spectrum organochlorine insecticide and acaricide used on food and non-food crops. To overcome the problem of hydrophobicity of endosulfan, surfactants play a major role in soil remediation. A concentration of 1 g/L tween 80 released 83.89 ± 1.22% of endosulfan from the soil in 24 hours and a total of only 13.96 ± 0.14% was found remaining in the soil. Phytoremediation is an emerging technology that promises effective and inexpensive cleanup of contaminated hazardous waste sites. The potential of aquatic plant species Salvinia molesta and the terrestrial plant species, Spinach (Spinacia oleracea) and Tomato (Solanum lycopersicum), to remove persistent organochlorine pesticide endosulfan from contaminated water and soil respectively were investigated. Remediation of endosulfan in water using different aquatic plants showed that Salvinia molesta is more efficient in endosulfan removal as the percentage removal of endosulfan obtained was 97.94 ± 0.33% in 21 days (with an initial concentration of 123 µg/L endosulfan). Among the selected terrestrial plant species, Spinach and Tomato, percentage removal of endosulfan was found to be higher with Tomato. On Day 21, complete removal of pesticide (with an initial concentration of 140 µg/Kg endosulfan) occurred in the soil in which phytoremediation was done with Tomato while Spinach took about 28 days for complete removal of endosulfan. Microbial degradation offers an effective approach to remove toxicants from the environment. Microbial degradation of endosulfan was studied and Pseudomonas species was able to completely degrade endosulfan in 16 days. The technologies developed can be utilized for the complete removal of endosulfan from a contaminated area. The surfactant enhanced recovery and phytoremediation will help to decontaminate the polluted water and soil. The recovered endosulfan in the surfactants and plants can be subjected to biodegradation by bacterial species using a bio reactor.

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A bioreactor system that consisted of Pseudomonas fluorescens cells immobilised in calcium-alginate beads was utilised to remediate endosulphan contaminated water and soil. A packed bed reactor system was designed for the bio-degradation of endosulphan in artificially spiked water samples (initial concentration of endosulphan: 350 µg/L). Reactor studies with cell-immobilised Ca-alginate beads were conducted after checking their efficiency through batch and column degradation studies. The results showed that the concentration of toxic isomers of endosulphan (endosulphan alpha and endosulphan beta) was below the limit in the bioreactor during the 7th day of the experiment. Experiments conducted with contaminated soil samples (initial concentration of endosulphan: 1,000 μg/kg) indicated that the toxic isomers of endosulphan degraded to below the detection limit within 10 days and monitoring of endosulphan residues on the 14th day revealed that almost complete degradation of metabolites of endosulphan had occurred. The bioreactor system designed can be scaled up for remediation of endosulphan in contaminated areas.