Zarqa River pollution: impact on its quality.

Pollutants released to the Zarqa River have been identified, quantified, and linked to their sources. The methodology included field observation of the river, collection of available quality data, literature review, and grab sampling. Identified pollution sources to the Zarqa River are wastewater treatment plants, overflow of wastewater pumping stations, and leaks from sewer lines and manholes that pass through the riverbed, in addition to industrial, commercial, domestic, and agricultural activities along the river course. The main pollutants released to the river from these sources are organics, nutrients, heavy metals, raw wastewater, solids, and solid waste. The results showed that the concentrations of organics, total nitrogen, and total phosphorus in the river are within the Jordanian standards for reclaimed water use in restricted irrigation. Between the river confluence with As Samra wastewater treatment plant effluent and King Talal Dam, where the river water is used for restricted irrigation, B, Cr, Mn, and Ni have exceeded the Jordanian guidelines for reclaimed water use in irrigation; however, frequencies of exceedances were low. Immediately downstream of King Talal Dam, cadmium and nickel concentrations have exceeded the recommended limits once, while boron concentration has exceeded the recommended limit 15 times during the sampling period between 2003 and 2010. However, exceedances in this zone are expected to disappear after the river water mixes with King Abdulla Canal freshwater. The mixed water is then used for unrestricted irrigation in the middle Jordan Valley. Upstream of As Samra, where exceedances occurred more frequently, groundwater is used for irrigation.