Combination of activated carbon adsorption with light-enhanced chemical oxidation via hydrogen peroxide

A tertiary treatment scheme involving simultaneous operation of activated c arbon adsorption and advanced oxidation with ultraviolet light and hydrogen peroxide, followed by "destructive regeneration" of the spent adsorbent by advanced oxidation was investigated, using phenol as a model compound. Ope rational parameters in each step were optimized on the basis of phenol and total organic carbon removal during selected contact times. It was found th at in the first stage with adsorption/advanced oxidation, phenol was totall y eliminated during the first quarter of the contact time, and 87.5% total organic carbon removal was accomplished at the end. It was further found th at advanced oxidation was the dominant pathway in this operation for the di sappearance of phenol, while that of total organic carbon was carried out b y combined effects of adsorption and oxidative degradation. Optimum regener ating frequency for the spent activated carbon was found to be once every f our batches, which was four times slower than the required frequency in the absence of advanced oxidation. In the second part of the operation, where the spent carbon was regenerated destructively via advanced oxidation, 92.5 % mineralization was accomplished in the regenerating solution at the end o f the optimized contact Lime. The economic assessment of the system conside ring the operation of both steps revealed that under the initial and optimi zed conditions, the operating cost is 2.26 USD per cubic meter of wastewate r with 40 ppm phenol. (C) 2000 Elsevier Science Ltd. All rights reserved.