Remediation of acaricide solutions in cattle tick dips to minimise soil and environmental contamination. II - Bioremediation

Successful bioremediation of cattle tick dip sludge contaminated with the formamidine acaricide amitraz (Taktic registered ) was demonstrated by the process of thermophilic composting. Laboratory and pilot trials have shown that the half-life of amitraz in compost is between 1 to 2 days, with degradation being attributed to both microbial activity and chemical degradation. The rate of biodegradation of amitraz was greater than non-biological degradation. The breakdown products N-2,4-dimethylphenyl-N'-methylformamidine (Formamidine), 2,4-dimethylformanilide (Aldehyde) and 2,4-dimethylaniline (DMA) were formed by both biodegradation and chemical degradation. While DMA was found to be a persistent or terminal metabolite of chemical degradation of amitraz, biodegradation in the compost did not accumulate any metabolites, as they were in turn rapidly biodegraded to non-detectable compounds. Biodegradation of flumethrin (Bayticol registered ) also occurred in thermophilic compost. There was little detectable non-biological degradation of this synthetic pyrethroid in the compost and its half-life in the pilot compost was shown to be 21 days.