Optimization of turbidity removal from wastewater using Carica papaya seed extract via response surface methodology

This study focuses on optimizing turbidity removal from wastewater using Carica papaya seed extract as a natural coagulant. While conventional chemical coagulants such as alum and ferric chloride are effective, they produce toxic sludge that poses environmental and health concerns. In contrast, papaya seeds contain bioactive compounds such as cysteine protease, offering a biodegradable and ecofriendly alternative. Response Surface Methodology (RSM) was employed to evaluate the effects of coagulant dosage, stirring speed, and pH on treatment efficiency. A jar test was conducted to simulate the coagulation and flocculation process, with 13 experimental runs designed using Central Composite Design (CCD) through Design-Expert software. The papaya seed extract was prepared with sodium hydroxide to enhance the release of active compounds. Statistical modelling identified the optimum conditions at a coagulant dosage of 125 mg/L, stirring speed of 175 rpm, and pH 7.75. Under these conditions, the model predicted a turbidity removal efficiency of 84.18%, while the actual mean removal from validation experiments was 87.78%, indicating good agreement with a percentage deviation of 4.27%. These findings demonstrate the potential of papaya seed extract as a sustainable alternative to chemical coagulants, with reduced sludge production and improved environmental outcomes. This research supports Sustainable Development Goal 6 by promoting innovative and environmentally friendly approaches to wastewater treatment and clean water management.