Oxidizing biocide. See

Microbial fouling is best dealt with before biofilm becomes mature. Biofilm protects the microorganisms from the action of shear forces and biocidal chemicals used to attack them. Microbes can be destroyed using chlorine, ozone, ultraviolet radiation, or some non-oxidizing biocides (see Chapters 8.2.1,8.2.2, 8.1.8, and 8.2.5, respectively). An effective method to control bacteria and biofilm growth usually involves a combination of these measures. Specifically, chlorination or ozonation of the pretreatment system, followed by dechlorination to protect the membranes, or UV distraction followed by periodic sanitation with a non-oxidizing biocide used directly on the membranes. 

For biocide treatment directly on the membranes, DBNPA is a good non-oxidizing biocide (see Chapter 8.2.5.2). For clean membranes, a dosage of about 100 ppm for 30 minutes 2 to 3 times per week is recommended. For heavier fouling, 100 ppm for 60 minutes 2 to 3 times per week should be fed. Alternatively, DBNPA can be fed continuously at about 2-3 ppm. Note that once biofouling gets out of control, it will be very difficult for DBNPA to work, because it is a non-oxidizer and cannot penetrate biofilm. DBNPA works best as a preventative treatment. 

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