Development of effective expanded vermiculite flocculant for enhanced primary treatment of swine wastewater: Lab-scale investigations

Abstract

Flocculation is an essential process to purify the swine wastewater which generally contains high concentration of suspended colloids and phosphorus. In this study, a novel acidified expanded vermiculite flocculant (A-EV) was developed to efficiently remove phosphorus and suspended solids (SS) from the swine wastewater. EV and A-EV were fully characterized to understand their properties. The optimum acid concentration was determined to be 20%. It was demonstrated that A-EV exhibited better performance than the widely used polyferric sulfate (PFS), giving rise to more compact and faster settled flocs. The volume of the supernatant accounted for PFS was only 34% of the total volume, while for A-EV, the volume of the supernatant accounted was 66%. When the dosage of A-EV was 1500 mg/L, the removal efficiency of SS, turbidity, COD and TN in the swine wastewater were 95.7%, 70.0%, 38.8% and 21.9%, respectively. The toxicity of A-EV was also evaluated to ensure its biosecurity. Zeta potential analysis revealed that adsorption - charge neutralization was the dominant mechanism. The excellent flocculating performance of A-EV is attributed to the synergistic effect of acid-soluble salts and non-soluble silicon frame. Our study indicated that A-EV could be regarded as a green and effective flocculant for effective enhanced primary treatment of the swine wastewater.