The impact of dosing sequence on the removal of the persistent pesticide metaldehyde using powdered activated carbon with coagulation and clarification

Removal of pesticides from drinking water remains a challenge for treatment suppliers throughout the world. A combined dissolved air flotation (DAF) and powdered activated carbon (PAC) was investigated as process removal recalcitrant pesticide metaldehyde. The PAC dosing position relative to coagulant studied regarding its impact on NOM pesticide, floc formation clarification efficiency. Four different sources were spiked with treated using PAC. dose 100 mg/L contact time 20 min required in order effectively remove compliance concentrations all sources. adsorption rate (kmet) decreased source DOC increased, moving 79.5–21.0 mg/?g/min an increase 2.6 6.5 mg/L. When coagulation, sequence addition followed by most effective due increased incorporation into floc, large size (median 800 ?m) high level removal, reducing metaldehyde concentration 0.18 ?g/L. Limited flocs observed when adsorbent added after coagulant. results provide rational basis selection conditions clarification.