Evaluation of the adsorption characteristics of dissolved organic matter using granular activated carbon (GAC) and the regeneration efficiency of denitrification, Electro-Fenton, and Sono-Fenton oxidation

Abstract

This research explored the use of a granular activated carbon (GAC) column to treat dissolved organics in Combined Sewer Overflows (CSOs), a major river pollutant. The regeneration efficiency of spent GAC was assessed utilizing three distinct methods: biological denitrification, electro-Fenton oxidation, and Sono-Fenton oxidation. Among the six organics tested, sucrose and raw sewage demonstrated the most comparable adsorption characteristics. GAC adsorption factors are multifaceted, involving pore size, surface functional groups, and competing solution substances, rather than just organic matter hydrophobicity. The biological denitrification enabled the utilization of the adsorbed organic matter on spent GAC, consequently reducing the initial NO3-N concentration from 99 mg/L to 8 mg/L over a period of 48 hours. Electro-Fenton treatment revealed marginal performance differences between SUS-SUS and Ti/Pt-Ti/Pt; however, the latter proved superior in terms of electrode stability over prolonged use. A combined strategy employing ultrasound and Fenton treatment at a frequency of 40 kHz yielded marginally higher GAC regeneration efficiency (68.5%) as compared to that at 750 kHz (67.8%). Among all regeneration techniques applied in this investigation, the Sono-Fenton method showed the highest efficiency.