Investigation of Activated Sludge Sewage Dewatering by Electro-Flotation: Optimization of Operating Parameters and Energy Consumption

Introduction & Common methods for dewatering of wastewater sludge need chemi-cals and high energy consumption and have low efficiency and environmental acceptability because of colloidal and jelly property of bacteria cells of sludge. Furthermore, their operat-ing is completely complicated. In this study electro-flotation way, as a novel method, was performed to cover these limitations and also operating parameters and energy consumptions were optimized. In order to carry out the experiments, a batch reactor with the effective volume of 450 ml was used. In this experimental- laboratorial study, the effect of pH, current density, hydraulic retention time and surface/volume changes on the amount of dewatering and the amount of total solids in both the sludge cake (dewatered sludge) and the water sepa-rated from the sludge as well as the content of TSS, TS and COD in the water were investi-gated. The amount of consumed electricity was calculated and lowered by optimizing the variables. The finding showed that the best efficiency (81.6%) of sludge dewatering was achieved at pH = 2, current density = 1.7mA/cm2, hydraulic retention time = 30 min and sur-face/volume amount = 178 cm2/L with electrical energy consumption of 0.33-0.726 kWh/m3. The electro-flotation process owing to high efficiency, convenient construction and operating and lower energy consumption and construction costs compared to common methods can effectively be applied.