The impact of the Arbaeen pilgrimage on treated wastewater at a station in the Holy Karbala Governorate was studied. The environmental pollution indicators of the treated wastewater were examined, and these results were then compared with treated wastewater from periods before, during, and after the Arbaeen pilgrimage (12/19/2009 – 1/21/2010). The results were also compared with standard environmental limits. The studied parameters included BOD, COD, CT, SO₄, NH₃, NO₂, NO₃, PO₄, TSS, fats, and oils.

The results indicated that the treatment plant in Karbala was not operating efficiently, as all the tests were found to be outside the permissible limits, except for chloride ion concentration and TSS. Interestingly, during the period of the pilgrimage, the plant did not record any readings, despite the massive influx of pilgrims into the holy city, which could reach approximately 15 million visitors.