Activated Carbon as an Advanced Treatment for Petrochemical Wastewaters

This paper presents the results of a study conducted with the purpose of establishing the feasibility of using activated carbon as an advanced treatment process for petrochemical wastewaters. Two pilot plants using Powdered Activated Carbon (PAC) and Granular Activated Carbon (GAC), respectively, were operated for a period of 15 weeks, fed with the effluent of a petrochemical wastewater treatment plant. The study was made using all available Brazilian carbons at the time. Isotherm tests and other carbon properties were used to select the carbons for GAC and PAC plants. The two pilot plants were operated between 8 April and 24 June 1981 at CETREL's wastewater treatment plant located at Camacari, BA, Brazil. The plant treats organic wastewaters from a petrochemical complex. During the first two GAC runs, low COD removal efficiencies were evident, and the effluent of all columns contained color due to the presence of organic colloids which were not adsorbed by the carbon. For this reason the feed to the system was pretreated to remove organic colloids. During the study period six GAC test runs were conducted using carbon GM and one using carbon HIDRO-G. Comparison of the two carbons showed that GM was the superior of the two. At all times, the GAC pilot plant using GM produced a colorless effluent from the amber-colored influent. At the same time, the PAC system, with a carbon dosage of 100 mg/l, was not capable of removing the color. One sample of carbon was regenerated to study its performance after regeneration. The analysis of the obtained data suggests that the adsorptive properties of the virgin and regenerated carbon may differ by as much as 12%. Several tests were made to determine the removal efficiency of priority pollutants in the GAC and PAC systems. These tests indicated that the GAC system is capable of reducing organic priority pollutants to below detectable limits. Metal analyses were made on several occasions on the GAC systems in addition to those conducted on priority pollutants samples. These tests indicated that metal concentrations in the GAC effluent were at or below the proposed effluent standards. The authors concluded that granular activated carbon is a sound advanced treatment process for petrochemical wastes to reduce organic priority pollutants to below detectable limits, producing an effluent with less than 150 mg/l COD.