Optimizing Urban Sludge Conditioning: A Comparative Study of Chemical Flocculation and Ultrasound/Flocculation Coupling of Sludge Collected from Baraki Wastewater Treatment Plant

The main objective of this investigation is to enhance the conditioning efficiency of urban sludge, collected from Baraki wastewater treatment plant. The study aims to evaluate and compare two distinct conditioning methods, namely chemical flocculation and ultrasound/flocculation coupling, with the goal of optimizing the treatment process for improved sludge management. Chemical conditioning trials, based on the flocculation process using a cationic polyelectrolyte, were conducted. Various doses were injected into 100 ml volumes of sludge [1]. The slurry suspensions were stirred at 140 rpm for 20 seconds. Then, this speed was reduced to 30 rpm for 2 minutes. The conditioned sludge was mechanically dehydrated by centrifugation at 4000 rpm for 10 minutes. The results showed an increase in dryness from 3.1% to 26.84%, a significant drainage efficiency of 80%, and a substantial reduction in turbidity from 137 to 13.43 after the application of 7 kg/T of dry sludge of polyelectrolyte. The pH remained almost unchanged, ranging from 7.72 to 7.43 for 2 to 9 kg/T of dry sludge of flocculent. For the conditioning by the ultrasound/flocculation coupling process, sludge samples underwent ultrasonic irradiation for varying durations of 10, 15, 30, and 60 minutes. Subsequent to this, a flocculation operation was conducted, involving the addition of escalating doses of cationic polyelectrolyte (ranging from 3 to 9 kg/T of dry sludge). The results indicated a correlation between dryness and both ultrasonication time and polyelectrolyte dose. Notably, the maximum dryness achieved was 45.03% after 30 minutes of sonication, coupled with flocculation using 5 kg/T of dry sludge of polyelectrolyte, compared to the initial dryness of 14.51% before the flocculation process. A sonication time of 30 minutes and a dose of 6 kg/T of dry sludge of polyelectrolyte have increased the volume of supernatant drained after ultrasound/flocculation coupling, with a maximum removal of 96%. A significant decrease in turbidity from 360 to 8.90 NTU was recorded with a dose of 5 kg/T of dry sludge and 30 minutes of sonication. The obtained results provide at least a clearer understanding of the efficiency and technical potential of ultrasound/flocculation coupling.