Application of a Mathematical Model for Sludge Reduction in Pharmaceutical Wastewater

Abstract

Excess sludge treatment is indispensable in sewage treatment plants. This study aims to reduce the excess material from activated sludge and establish a mathematical model. Sludge dissolution rates were calculated by measuring the total chemical oxygen demand (TCOD) and the soluble COD (SCOD) with regard to water quality before and after pretreatment. Then, sludge reduction effects were obtained by means of the suspended solid (SS) changes. The major impact factors on sludge dissolution rates were evaluated, such as pH, temperature, potassium ferrate amount, and reaction time, among others. The response surface method of the Design-Expert V8.0.6.1 software was adopted to analyze the sludge dissolution rate, which represents the sludge reduction effect. By regulating the different constraint factors, the Design-Expert model showed that the sludge dissolution rate reached the highest value of 54,36% at a temperature of 21,58 oC and a pH of 4, as well with a potassium ferrate dosage of 1 mg/g SS and a reaction time of 4,07 hours with constant stirring. A mathematical model for the sludge dissolution rate that considers temperature, pH, potassium ferrate dosage, reaction time, and stirring condition was established, and the simulated R2 value of 0,72 indicated a relatively acceptable fitting effect.