Utilization of Drinking Water Treatment Slurry to Produce Aluminum Sulfate Coagulant

Abstract

In Egypt, water treatment consumes about 365 000 tons of aluminum sulfate and produces more than 100 million tons of sludge per year. The common disposal system of sludge in Egypt is to discharge it into natural waterways. Toxicity of aluminum, environmental regulations and costs of chemicals used in water treatment and sludge treatment processes led to an evaluation of coagulant recovery and subsequent reuse. The present work aimed at aluminum recovery from sludge of El-Shiekh Zayd water treatment plant (WTP) to produce aluminum sulfate coagulant. Sludge was characterized and the effect of five variables was tested and the process efficiency was evaluated at different operating conditions. Maximum recovery is 94.2% at acid concentration 1.5 N, sludge weight 5 g, mixing speed 60 rpm, temperature 60 °C and leaching time 40 min. Then optimum conditions were applied to get maximum recovery for aluminum sulfate and compared to commercial coagulant on raw water of El-Shiekh Zayd (WTP).

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

“…Organic content in the sludge wasted from ESZ-WTP recorded 23% w/w of the sludge, which reflects organic matter removed from the raw water during the treatment process. This complies with the literature which reports the presence of organic matter in sludge wasted from the clarification process (Fouad et al, 2017a(Fouad et al, , 2017cRaeke et al, 2017). Metals content of the sludge used in this study is presented in Table 1, which illustrates that aluminum was the highest concentration metal in the sludge.…”

“…Sludge Characterization. The prepared sludge was characterized by measuring organic content by weight loss on ignition at 550 8C (Fouad et al, 2017a(Fouad et al, , 2017b. Afterward, sludge metals composition and concentration were determined by acid digestion as per U.S. EPA method no.…”

“…Coagulant Recovery Optimization. Aluminum sulfate recovery was performed using a solution of 1.5 N sulfuric acid, 60 8C temperature, 40 min mixing time, 60 rpm mixing speed, and 5 g dried sludge as reported in the authors' previous work (Fouad et al, 2017a) as optimum conditions for the recovery process using ESZ-WTP sludge. These optimum conditions were reported to achieve 94.2% aluminum sulfate recovery (Fouad et al, 2017a).…”

“…There are many chemical methods for coagulants recovery from sludge including acidification, basification, ion exchanging, and Donnan dialysis (Fouad et al, 2017b). But the most economically attractive is sludge acidification and reuse in potable water production, domestic wastewater, and industrial effluents treatment (Fouad et al, 2017a(Fouad et al, , 2017bIppolito et al, 2011). Sludge acidification and coagulants recovery demonstrate good practice for waste handling and recovery of a useful material from the treatment process, which reduces the operational costs.…”

“…Pollutants accumulation in the recovered coagulants is one of the main highlighted obstacles reported to affect the sustainability of the recovery process (Babatunde and Zhao, 2007;Fouad et al, 2017aFouad et al, , 2017bKeeley et al, 2016). Despite some research, trials have proceeded to fill the knowledge gap in the area of sequential coagulants recovery (Fouad et al, 2017c), however, pollutants accumulation in sequentially recovered coagulants is still not well covered and needs more investigation, especially for recovery using sulfuric acid.…”