Effect of the aqueous matrix on the inactivation of E. coli by permaleic acid

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies

Background:

• Peracetic acid (PAA) is a common disinfectant, but its efficacy can be influenced by water quality.
• Permaleic acid (PMA), a derivative of maleic anhydride, has not been extensively studied as a disinfecting agent.

Purpose of the Study:

• To investigate permaleic acid (PMA) as a potential disinfecting agent.
• To compare PMA's antimicrobial activity against E. coli with peracetic acid (PAA).
• To evaluate the impact of pH and bivalent ions (Mg2+ and Ca2+) on PMA's disinfection efficiency in real water matrices.

Main Methods:

• Synthesized PMA from maleic anhydride and hydrogen peroxide.
• Assessed antimicrobial activity by measuring E. coli growth inhibition.
• Investigated the effects of varying pH and concentrations of Mg2+ and Ca2+ on PMA efficacy.
• Calculated pKa values for PMA using DFT methods.
• Conducted disinfection tests in the presence of EDTA.

Main Results:

• PMA demonstrated antimicrobial activity against E. coli.
• Disinfection efficiency of PMA was highly sensitive to bivalent ion concentrations; high levels (e.g., Ca2+=13.3 mg L-1, Mg2+=25.6 mg L-1) drastically reduced E. coli reduction (< log 1).
• Alkaline pH significantly decreased PMA's disinfection efficacy (pH 9 resulted in < log 1 E. coli reduction).
• DFT calculations predicted a pKa2 of 7.3 for PMA, aligning with experimental observations regarding pH effects.

Conclusions:

• PMA's disinfection performance is strongly dependent on water quality parameters, particularly the concentration of metal bivalent ions and initial pH.
• Optimizing PMA application requires careful consideration of these water matrix characteristics.
• PMA shows potential as a disinfectant, but its use in real-world water treatment necessitates further investigation into mitigating factors affecting its efficacy.