Polynuclear Aromatic Hydrocarbons (PAH) and Heavy Metals in Dry and Wet Sludge from As-Samra Wastewater Treatment Plant, Jordan

Abstract

Dry and wet sludge samples were collected from the sewage sludge storage site and primary treatment ponds at As-Samra Wastewater Treatment Ponds in Al Hayshmia, Jordan. The concentrations of polynuclear aromatic hydrocarbons (PAH) and macro- and microelements were determined using gas chromatography-mass spectrometry (GC-MS) and inductively coupled plasma-mass spectrometry (ICP-MS), respectively.

Environmentally relevant concentrations of PAH were detected ranging from 62 μg g⁻¹ to 70 μg g⁻¹ for dry sludge and from 35 μg g⁻¹ to 47 μg g⁻¹ for wet sludge. These results indicated a potential environmental risk if sewage sludge is reused in Jordan as organic fertilizer without first being treated. The results of the study showed that the sewage sludge samples were contaminated with low levels of heavy metals, as the dry sludge samples were characterized by higher concentrations of most analyzed elements than for wet sludge samples. Still, none of the trace metal concentrations exceeded the threshold concentration levels for agricultural-related sludge.

Unlike many other nutrients found in sludge, the Total Organic Carbon (TOC%) found in dry and wet sludge revealed similar values, at 13.18 percent and 13.29 percent, respectively. The total phosphorus ranged from 0.25% for dry sludge to 0.47% for wet sludge. Total nitrogen varied from 0.80% for wet sludge to 1.01% for the dry sludge samples. The overall nutrients levels are close to those found in the literature. The findings of this study have improved the understanding of sewage sludge characteristics in a semiarid environment.

Keywords:

• PAH
• heavy metals
• TOC
• sewage sludge
• As-Samra
• Jordan

Acknowledgments

The author would like to thank Briana Adams, a U.S. Peace Corps volunteer based in Jordan, for the text editing.