Fuzzy optimization of Fenton\u27s reagent and cationic surfactant for sludge dewatering

Abstract

Sludge is a by-product of wastewater treatment which has a high-water content. Sludge dewatering is performed to reduce its water content prior to its disposal. Through lowering the water content of the sludge, dry solids (DS) are formed. The objective of the study is to minimize the water content of the sludge and the total operating cost. The efficiency of cetyltrimethylammonium bromide (CTAB), ferrous ion (Fe2+), and hydrogen peroxide (H2O2) in dewatering the sludge are evaluated. Parametric study is performed to understand the relationship of the reagent, operating cost in $/L, and water content of the sludge. The e-constraint is applied to determine the boundary limits of the operating cost and water content for the Pareto frontier identification. Through fuzzy optimization, the study can identify the satisficing solution which simultaneously minimizes water content and cost for Fenton’s reagent and CTAB. The combination of the three reagents is observed to enhance the dewaterability of the sludge. The optimal dosage of ferrous ion, hydrogen peroxide and CTAB is 1.00 mg/g DS, 204.53 mg/g DS, and 162.96 mg/g DS, respectively. Thus, the optimal minimum water content using these reagents is 67.97$/L on a 100 mL sludge and an overall satisfaction level of 40.47 %. Keywords: Sludge dewatering, CTAB, hydrogen peroxide, ferrous ion, e-constraint method, Pareto frontier, fuzzy optimization