Biocide action of monochloramine on biofilm systems ofPseudomonas aeruginosa

Monochloramine was used to inactivate biofilm cells of Pseudomonas aeruginosa. Experimental results indicated that the clean RotoTorque system had no monochloramine demand. The dose of 4 mg·l−1 killed in situ biofilm cells more than 99·99% within 60 min, while the dose of 3 mg·l−1 killed 80% and the dose of 2 mg·l−1 showed no significant killing. Computations of pseudo steady state surface gradient of monochloramine and the observable modulus indicated that there was no marked mass transfer resistance in the biofilm for the 4 mg·l−1 treatment, moderate mass transfer resistance for the 3 mg·l−1 treatment, and high mass transfer resistance for the 2 mg·1−1 treatment. Mass transfer resistance within the biofilm impacts the biocide performance.