Designing a Response Surface Model for Removing Phosphate and Organic Compound from Wastewater by Pseudomonas Strain MT1

Abstract

Improvement in wastewater bioremediation in water treatment refineries has attracted attention recently. For this, a strain of Pseudomonas aeruginosa MT1 with phosphate accumulating capacity was isolated from the topsoil of an agricultural land through screening in an enrichment medium based on decolorizing Toluidine blue-O dye. Two experimental design approaches were adopted to find the optimum condition for phosphate and organic carbon removal using the strain. In the first approach, one factor at a time method was employed with different carbon sources (glycerol, sodium citrate, sodium acetate and frying oil), pH and temperature range as well as KH2PO4 and NH4Cl concentrations. Maximum bacterial growth (250 mg/l) and phosphate sequestration (10.5 % of total phosphate) were achieved at pH 7.5, 30–35 °C and in frying oil as carbon source within 48 h incubation, while KH2PO4 in the range of 5–15 mg/l was regarded as ineffective. KH2PO4, sodium acetate concentrations, pH and agitation speed ranges were re-used in the second experimental approach using central composite design from response surface methodology. All experimental runs were conducted at lab-scale in a liquid synthetic wastewater with the variation of the factors whose supernatant chemical oxygen demand and phosphate contents were measured at the end of the batch incubation. In comparison, the response surface method resulted in more promising yield (50 and 38 % improvement in organic carbon and phosphate removal, respectively) and was more informative than one factor at a time approach in understanding the distinctive and interactive effects on the objective responses.