Repeated Aluminum Sulfate Recovery from Waterworks Sludge: A Case Study in El-Sheikh Zaid WTP.

Although surface water treatment presents a good solution for pollutants in rivers and freshwater lakes, the purification process itself presents a great threat to the aquatic environment through aluminum waste disposal. Recent studies have introduced coagulants recovery from treatment sludge as a green solution for waste handling and cost reduction. This article aims to evaluate repeated aluminum coagulants recovery from sludge using sulfuric acid. The waste from El-Sheikh Zaid Water Treatment Plant (ESZ-WTP) was characterized, then sequential coagulants recovery using optimum conditions was conducted. In addition, treated water was analyzed to determine the efficiency of the obtained coagulants and their influence on treated water quality. Sequential coagulants recovery using acidification revealed that no metals accumulation took place in the produced coagulants until the third recovery from ESZ-WTP sludge. On the other hand, a noticeable increase in trihalo-methanes was detected in the treated water, especially using the third recovered coagulant. In conclusion, sequential coagulants recovery and usage in water treatment is an attractive alternative for single-use original coagulant in ESZ-WTP but for no more than three sequential recoveries. It is advisable to apply a fresh coagulant every three sequential recoveries to enrich the aluminum content and regenerate the sludge before restarting the recovery process.