Treatment of carbamate insecticide rinsates by adsorption and biodegradation using spent media from the mushroom production industry

This research was conducted to investigate the feasibility of using spent mushroom compost (SMC) as an adsorption medium and as a microorganism source to remediate carbamate insecticide rinsates in a completely mixed batch reactor (CMBR) for on-farm use. Included was an improved understanding of the kinetics for removal mechanisms (adsorption and biodegradation) involved.; Three widely used carbamate insecticides, namely carbaryl, carbofuran, and aldicarb with a concentration range of 0-30 mg/L, were selected for adsorption and biodegradation studies. The results of the adsorption study indicated that the adsorption of carbamate pesticides on SMC was found to exhibit nonlinear "favorable" adsorption behavior which can be characterized well by the Freundlich isotherm model.; The results of the biodegradability study showed that the SMC cultures could mineralize carbamate successfully producing a BOD/COD higher than 0.5, and the three carbamates did not show an inhibitory effect on SMC cultures over the concentration range of 0-30 mg/L. Microbial hydrolysis was identified as one of the major metabolic pathways for carbaryl and carbofuran degradation as indicated by the accumulation of 1-naphthol and carbofuran phenol in the medium, respectively, while the biodegradation of aldicarb was through an oxidative pathway. The degradation rate of carbamate pesticides was described well by the Monod model. The values of maximum specific growth rate pointed out that carbaryl and carbofuran were "readily" biodegradable by SMC cultures while aldicarb was categorized as a "hardly" biodegradable compound.; In summary, SMC may potentially be used for on-farm treatment of carbamate pesticide rinsates. The treatment efficiency for carbamate pesticides with SMC as media decreased in the order: carbaryl {dollar}>{dollar} carbofuran {dollar}>{dollar} aldicarb.