Kathon (CMI-MI)

a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one (CMI) and 2-methyl-4-isothiazolin-3-one (MI)

was extensively used in industry as a nonoxidizing biocide or disinfectant. However

it would show adverse effects on aquatic life when it is discharged into surface water. In this study

the removal performance

parameter influence

degradation products and enhancement of subsequent biodegradation of CMI-MI in UV/H

2

O

2

system were systematically investigated. The degradation rate of CMI-MI could reach 90% under UV irradiation for 20 min when the dosage of H

2

O

2

was 0.3 mmol L

-1

. The DOC (dissolved organic carbon) mineralization rate of CMI-MI could reach 35% under certain conditions ([H

2

O

2

]

=0.3 mmol L

-1

UV irradiation for 40 min).

k

obs

was inversely proportional to the concentration of CMI-MI and proportional to the concentration of H

2

O

2

. The degradation rate of CMI-MI was almost unchanged in the pH range from 4 to 10. Except the presence of CO

3

2-

inhibited the removal rate of CMI-MI

SO

4

2-

Cl

-

NO

3

-

and NH

4

+

did not interfere with the degradation of CMI-MI in the system. It was found that UV/H

2

O

2

system had lower energy consumption and more economic advantage compared with UV/PS system by comparing the E

EO

(electric energy per order) values under the same conditions. Two main organic products were identified

namely HCOOH and CH

3

NH

2

. There's also the formation of Cl

-

and SO

4

2-

. After UV and UV/H

2

O

2

photolysis

the biochemical properties of CMI-MI solution were obviously improved

especially the UV/H

2

O

2

treatment effect was better

indicating that UV/H

2

O

2

technology is expected to combine with biotechnology to remove CMI-MI effectively and environmentally friendly from wastewater.