Accumulation of Heavy Metals on Soil Irrigated with Treated Wastewater at Al al-Bayt University-Jordan

Four types of water used for irrigation at Al alBayt university campus: untreated wastewater, treated wastewater, fresh groundwater and mixed fresh/ wastewater were tested and evaluated accordingly to its suitability for irrigation and the impact of using treated wastewater on heavy metal accumulation with time. Major ionic composition (HCO
₃
^-
, Cl
^-
, NO
₃
^-
, SO
₄
^-2
, Ca
⁺²
, Mg
⁺²
, Na
⁺
and K
⁺
) of water samples were determined in addition to four heavy metals (Zn, Pb, Cu and Ni). Soil samples at different depths including the upper (0-20 cm) and lower (20-40 cm) were tested for heavy metals. The results showed that the treated wastewater and the fresh water were below the Jordanian standards and suitable for irrigation with no threat of using such water for irrigation in terms of major ionic composition as the wastewater is excellent to permissible in terms of sodium percentage, and S2-S3 with C3 in terms of SAR even before being mixed with fresh water. For heavy metals although their concentrations were low in the treated wastewater that only Ni and Zn were above the detection limits, such metals accumulated in the soil as its concentrations in soil increased with the longer period of irrigation where the highest concentrations found in the lower soil profile which was irrigated for 15 years and the lowest was for soil irrigated for 5 years after the minimum level of the obtained blank samples.