Polycyclic aromatic hydrocarbons (PAHs) are organic compounds widely distributed in the environment. In the present work, concentrations of these organic compounds in sludge samples from Cluj-Napoca wastewater treatment plant are reported. The objective was to investigate PAHs in sludge from wastewater treatment plant and to assess their potential for land application. Primary sludge, fermented sludge, fermented concentrated sludge, anaerobic-digested dehydrated sludge and rejection water samples were collected monthly from December 2012. Ultrasonic assisted extraction with hexane was used, being followed by filtration and concentration to dryness in a rotary evaporator; the obtained residue was redisolved in acetonitrile. High performance liquid chromatographic analysis was achieved using an Agilent 1100 system consisting in a solvent degasser, a quaternary pumping system, an autosampler, a column oven, a diode-array detector and a fluorescence detector. Separations were accomplished using an Envirosep PP column with acetonitrile:water as mobile phase (45:55 v/v). Detection limit was 0.001 ïg/ kg, with good linearities for all PAHs, with correlation coefficients higher than 0.998. PAHs with four rings appeared to be the primary components in most of the tested sludge samples, the highest concentration levels being in anaerobic-digested dehydrated sludge samples. The obtained results can be helpful for the regional policy makers to make proper decisions on treating the increasing amount of sewage sludge, to provide practical reference for establishing threshold values of PAHs for land application of sludge, knowing that the practice of recycling sewage sludge onto agricultural lands poses an additional risk of soil contamination with PAHs.
Stormwater inflow loading of polycyclic aromatic hydrocarbons into urban domestic wastewater treatment plant for separate sewer system
