ADVANCED OXIDATION TREATMENT OF MINE DRAINAGE

摘要

An investigation of the effects of ozone andozone-induced hydroxyl radical on reducing whole effluenttoxicity is described and discussed relative to the application ofozone for industrial water treatment. Results from operation ofan ozone system treating industrial effluent from a lead and zincmine in Colorado are presented. The mine discharges 1,000 gpmof wastewater into a tributary of the Arkansas River and hashistorically exceeded Whole Effluent Toxicity (WET) limits andon occasion has exceeded numeric limits for copper, ammonia,and cyanide. Based on results of a Toxicity IdentificationEvaluation (TIE) conducted on the effluent and individualprocess waste streams, the source of effluent toxicity is believedto be primarily associated with organic reagents used in the milling process.Based on test results, an applied ozone to COD ratio of 3:1 byweight and a contact time of 30 minutes was found to beeffective for reducing whole effluent toxicity at pH 11 but not atpH 7, indicating oxidation by hydroxyl radical to be thedominant mechanism responsible for toxicity reduction. At anapplied ozone to COD ratio of 3:1 and a pH of 11, toxicity wasimproved from 0 percent survival to 100 percent survival forCeriodaphnia dubia and fathead minnow (Pimephales promelas)based on 48-hour and 96-hour WET tests, respectively. Thisapplication rate of ozone with a 99 percent mass transferefficiency was also effective in reducing total cyanide from anaverage of 0.45 mg/L to less than 0.05 mg/L and COD from 28mg/L to 9 mg/L. Ammonia reduction by ozone was negligible atan applied ozone to COD ratio of up to 4:1 and a contact time ofup to 40 minutes.