Chlorine dioxide is a highly potent biocide that has a higher efficacy than hypochlorite in destroying protozoa, bacteria and viruses, without allowing them to build a tolerance. It is effective over a wide pH range as both a biocide and metal precipitant and has gained popularity because it creates significantly lower concentrations of disinfection byproducts such as trihalomethanes (THM’s) and haloacetic acids (HAA’s) when compared to chlorine. However, at least one study has shown that THM formation is still significant when naturally occuring organic matter (NOM) such as humic acids are present (A.A.Stevens, “Reaction Products of Chlorine Dioxide”,1982).
Chlorine dioxide is a powerful oxidizer and can damage polyamide reverse osmosis (RO) membranes, so a reducing agent such as sodium bisulfite is usually dosed as a precautionary measure.
The use of chlorine dioxide at a low residual that would deplete prior to contact with the RO membrane surface has been a hot topic. But as with any other biocide, when the residual depletes to sub-lethal doses prior to membrane contact, biofouling will be enhanced. This was confirmed in a 2010 publication by Shemesh et al, “The biocide chlorine dioxide stimulates biofilm formation in Bacillus subtilis by activation of the histidine kinase KinC.”
Chlorine dioxide can be used in the permeate but only at low dosages because it is reduced to chlorite and chlorate ions which can cause anemia and affect the nervous system. In the United States, the EPA limits the allowable residual of chlorine dioxide in drinking water to 0.8 ppm.
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Hace unas semanas, preservamos todas las membranas RO en nuestros trenes con metabisulfito de sodio para un almacenamiento a largo plazo. Nuestro fabricante de membranas nos recomendó que cambiáramos la solución una vez que el pH cayera por debajo de 3. Medimos una disminución en el pH durante las dos primeras semanas, pero en la tercera semana, el pH aumentó. ¿Podría explicar por qué el pH aumentó en lugar de disminuir?
¿Por qué aumenta el pH del permeado RO cuando el agua pasa a través de un desgasificador? ¿Ese pH más alto realmente estabiliza el permeado RO para ayudar a prevenir la corrosión en el sistema de distribución?
pH和碱度之间的关系是什么？ 他们有什么不同？ 温度如何影响他们？
What is the relationship between pH and alkalinity? How are they different? How does temperature affect them?