Effect of diethylamine on PAH removal from municipal sludge under UV light

Abstract

This study was carried out to investigate the effect of diethylamine (DEA) on the removal of polycyclic aromatic hydrocarbon (PAH) from municipal sludge under ultraviolet (UV) light. UV apparatus was designed specifically for the PAH removal experiments. Sludge samples were collected from the municipal wastewater treatment plant which serves a population of 585000. Sludge samples were exposed to sunlight for 24 hours following the addition of 0.5% and 5% (w/w) DEA. Another group of samples including DEA dosages in the amounts that were stated above were exposed to UV-C light for 24 hours. Experiments in the UV apparatus were carried out at 38 degrees C and 53 degrees C to evaluate the effect of temperature on PAH removal. All of the PAH removal studies which were performed in UV apparatus and under natural sunlight were conducted in triplicates. The inlet air was cleaned with a polyurethane foam (PUF) column to determine the amount of PAH that evaporated from the sludge. The total PAH concentration was decreased on average by 50% and 40% by using 0.5% and 5% DEA, respectively. The amount of the volatilized PAH compounds increased with increasing temperature. Specifically, the 3-4 ring PAH compounds evaporated. The average concentrations of volatilized PAHs were measured as 5.6 ng/m(3) and 25 ng/m(3) for 38 degrees C and 53 degrees C, respectively. At the end of the 24 hours, the PAH concentration of the samples which were exposed to sunlight were higher than the initial PAH amounts. The potential PAH precipitation from the air to the sludge surface might have caused this increased concentration.