Biofilm removal

Gluteraldehyde + 10% block copolymer (BCP), a nonionic biodispersant. Dose at 40 to 50 ppm. Effective as a slime penetrant, sessile bacteria biocide, and biofilm remover. Not particularly suitable with high levels of ammonia or primary amine. 

TABLE I Sorption of Amino Acids onto Clean Stream Sediment Surfaces (Si02) with the Biofilm Removed... 

No commercial substrate is completely resistant to surface bacterial growth and biofilm formation. In a study at the University of Minnesota, PFA with a smooth surface was found to be least hospitable to bacterial growth. Biofilm removal from PFA was eas-... 

Table 3.90. Biofilm Removal (%) in Virtually Quiescent Dilute Sodium Hypochlorite Reported by the BioProcess Technical Institute, University of Minnesota ...

The effect of flow velocity on biofilm removal is illustrated on Fig. 14.14 [Nesaratnam and Bott 1984]. The curves show that as the velocity is increased the rate of removal of established biofilm increases, and the apparent final biofilm thickness is less. There are two effects related to velocity and include ... 

FIGURE 14.13. The dependence of initial rate of biofilm removal on ee chlorine concentration... 

Dose sequence Ozone concentration mg/l Duration of application h Initial removal rate % mass/min Biofilm removed %... 

Nesaratnam, R.N. and Bott, T.R., 1984, Effects of velocity and sodium hypochlorite derived chlorine concentration on biofilm removal from aluminium tubes. Proc. Biochem. 19,14 -18. 

Fig. 21 Top Schematic setup of an ultrasonically vibrating micropitted silicon surface. The cavitation chamber is filled with pure liquids or a cell cultivation liquid for biological assays. Bottom Temporal recording of a biofilm removed by microbubbles. The grey area with black dots is the zone covered by biofilm. The pit is indicated with a large black dot. Microbubbles can be identified as the blurred dark region surrounding the pit. Reproduced with permission from [110]. Copyright 2012 AIP Publishing...

FIGURE 4.10 (a) Biofilm removed from amild steel electrode in amixed marine culture environment along... 

Biofilm formation at the air-water interface. The bathtub ring often formed at the air-water interface around the sides of the basin is likely to be a biofilm due to microbial activity. This film acts like a trap and is known to concentrate caesium and other radioactive isotopes contained in the basin water. This biofilm should be removed mechanically by wet brushing, using water to hold down any airborne activity. A 35% solution of hydrogen peroxide has proven effective in suppressing microbial activity and could be used to assist in biofilm removal without corrosive attack on aluminium alloys. 

Ozone bacteria, biofims no corrosive ions or other residual product formed 0.01-0.05 ppm in continuous treatment (up to 1 ppm for biofilm removal)... 

Exner et al. (1987) reported that lOmg/L of free chlorine reduced the colony count of drinking water biofilms on silicone tube surfaces by approximately four log units after a contact time of 24 h however, no complete inactivation was observed. SEM examination of the silicone surfaces demonstrated that no biofilm removal had occurred. A shorter contact time of 60 min or treatment with a lower chlorine concentration (0.3mg/L) for 24 h had no inactivating effect on the biofilm bacteria. 

Typical enzymes investigated for assisting with biofilm removal include proteases act to hydrolyse peptide bonds in proteins and peptides, amylases act to cleave glycosidic linkages in starch or glycogen, levan hydrolyases act to hydrolyse levan (polysaccharide). 

No commercial substrate is completely resistant to surface bacterial growth and biofilm formation. In a study at the University of Minnesota, PFA with a smooth surface was found to be least hospitable to bacterial growth. Biofilm removal was easily and completely accomplished from PFA (Table 13.49). PFA was cleaned more completely than glass, stainless steel, and PVDF. Figure 13.112 shows the results of bacterial count in a dynamic ultrapure water system in which fouling of the surfaces of stainless steel, PVDF, and ECTFE were studied. ECTFE and PVDF were orders of magnitude less susceptible to biofouling than stainless steel. 

Bergel et al. (2005) discovered that the formation of seawater improved the performance of stainless steel cathodes used in seawater applications of hydrogen fuel cells. The amount of improvement depended on the electrode sizes and pH. The fuel cell produced 41 mWW in the presence of the biofilm, but only 1.4 mW/m when the biofilm was removed, an increase of 30x (power normalized to cathode projected surface area). Increasing the pH of the anode compartment from 8.2 to 12.5 increased power to 270 mWW, which was almost lOOx larger than that with the cathode biofilm removed (2.8 mWW). The highest power output was 325 mW/m, which was obtained by decreasing the cathode surface area from 9 to 1.8 cm. ... 

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