Combining chlorination and chloramination processes for the inhibition of biofilm formation in drinking surface water system models.
OBJECTIVE
The aim of this study was to investigate the inhibition of biofilm formation on stainless steel (SS) and galvanized mild steel (MS) in chlorine (AFC(1)) and chlorine-monochloramine treated waters (AFC(2)M).


RESULTS
Disinfection was carried out using 2.5 mg l(-1) free chlorine followed by 1.5 mg l(-1) monochloramine, with non-disinfected water used as control water. Results of the standard spread plate procedure, DAPI epifluorescence microscopy and scanning electron microscopy revealed bacterial colonization of SS and MS exposed to non-disinfected and chlorinated waters between 24 and 720 h, while no bacterial adhesion was detected on SS and MS exposed to AFC(2)M between 48 and 504 h.


CONCLUSIONS
The inability of bacteria to grow on SS and MS was observed only when 0.35 mg l(-1) residual monochloramine was maintained throughout the system.


CONCLUSIONS
This demonstrates the inability of chlorine alone to inhibit bacterial growth and suggests a combination of chlorine and monochloramine as a more effective treatment for drinking water, especially for rural communities with very poor source waters in Africa.
Momba
M N B
MN
Department of Biochemistry and Microbiology, University of Fort Hare, Alice South Africa. mmomba@ufh.ac.za
Binda
M A
MA
D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development; D001422:Bacterial Adhesion; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002700:Chloramines / Q000494:pharmacology*; D002713:Chlorine / Q000494:pharmacology*; D004203:Disinfection / Q000379:methods*; D013193:Stainless Steel; D013232:Steel; D018508:Water Purification / Q000379:methods; D014881:Water Supply
D002700:Chloramines; D013193:Stainless Steel; D013232:Steel; D002713:Chlorine; C030816:chloramine