Aluminum sulfate regeneration from surface water treatment waste in Cairo, Egypt

The world needs to adapt to recycling and reusing water due to limited resources. So, decision-makers and policy leaders should use sustainable practices to improve protection and pollution remediation. Aluminum sulfate is used for surface water treatment, which leads to waste sludge being disposed into water bodies, causing environmental pollution. Coagulants' regeneration from sludge improves water quality and reuse options. Organics accumulation is the primary concern regarding coagulant regeneration, using acidification. Our study investigated the raw water quality, aluminum sulfate, and sludge and evaluated its influence on coagulant recovery, using acidification, from eight water treatment plants (WTPs) in Cairo, Egypt. The significant elements in the tested sludge were aluminum with a concentration range of 86.65-688.85 mg/g sludge in El-Rawda and Embaba and iron with a concentration range of 9.45-7.45 mg/g in Shamal Helwan and El-Fostat. Recovery percentages of aluminum, iron, manganese, and strontium recorded the highest values 97%, 89%, 89%, and 92% for Embaba, Rod El-Farag, Embaba, El-Rawda, respectively. The correlation between metal concentration and recovery was insignificant in the studied matrix and conditions for the four metals. Total organic carbon (TOC) transfer into recovered solutions was maximum in El-Fostat (82.6%) and minimum in Embaba (36.7%). The TOC transfer percentage depends on the matrix of the sludge. The best location for coagulant recovery is at the Embaba WTP, where there were minimum organics transfer and maximum Al recovery.