Enhanced coagulation using a magnetic ion exchange resin.

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies

Background:

• Disinfection by-products (DBPs) like trihalomethanes (THMs) and haloacetic acids (HAAs) are formed during water disinfection.
• Enhanced coagulation is a key process for removing DBP precursors, but often requires high coagulant doses.
• Magnetic ion exchange (MIEX) resin offers a potential method to improve DBP precursor removal.

Purpose of the Study:

• To evaluate the effectiveness of MIEX pretreatment for removing DBP precursors from various surface waters.
• To assess the impact of MIEX pretreatment on the alum dose required for turbidity coagulation.
• To compare the performance of MIEX-assisted coagulation with conventional alum coagulation alone.

Main Methods:

• Utilized nine surface waters representing the USEPA's 3x3 enhanced coagulation matrix.
• Applied MIEX pretreatment followed by alum coagulation.
• Measured residual total organic carbon (TOC), ultraviolet absorbance (UVA), and DBP formation potential (THM and HAA).

Main Results:

• MIEX pretreatment significantly reduced THM and HAA precursors by over 60% in all tested waters.
• Reductions in precursors approached 90% in waters with high specific UVA.
• MIEX treatment, combined with alum, resulted in lower residual TOC, UVA, and DBP formation potential compared to alum alone.
• MIEX pretreatment substantially decreased the coagulant demand of the surface waters.

Conclusions:

• MIEX pretreatment is a highly effective method for removing DBP precursors from diverse surface waters.
• MIEX significantly reduces the coagulant (alum) dose required for effective water treatment.
• This approach offers a promising strategy for optimizing water treatment processes and minimizing DBP formation.