Application In Membrane & Resin Sanitation.
Membrane sanitation –
The membrane separation technology, especially reverse osmosis, is used as an alternative to water production with higher quality and also to wastewater treatment in industrial process for its reuse. However, the use of the membranes is limited by its lifetime which varies according to the species, the amount of impurities present in the effluent and the frequency of cleaning. Some impurities also can propitiate the development of microorganisms in the flow channels and on the surface of the membranes that, to some extent, will contribute for the membrane degradation; this phenomenon is known as biofouling.
To prevent Biofouling, it is necessary to imply an efficient disinfection process in the feed stream of the reverse osmosis unit to promote the death of the microorganisms and the oxidation of the organic matter.
Chlorination is the practice adopted in many industries, but chlorine can cause environmental damage, health hazards in the industry and damages the olyamide membranes. Therefore, it is necessary to find a less aggressive agent to the environment and to the polyamide membranes.
CDD-5000 (0.5% Chlorine Dioxide) is less aggressive than any chlorinating agent but is capable to reduce the total population of bacteria.
RO tolerance of CDD-5000:
Many experiments (mentioned below) had already been carried out in various laboratory scale to reverse osmosis units with chlorine dioxide generated by classical way. It was verified that chlorine dioxide is less aggressive than chlorine. And below 0.8 ppm of chlorine dioxide, carbon filters and RO equipments effectively removes chlorine dioxide and its by products.
When using CDD-5000 it is possible to use CDD-5000 before the RO-membrane without damaging the membrane.The function of adding CDD-5000 after the active coal and before the membrane is simple: by adding CDD-5000 in ppb dosage rates the water contains disinfection power at low dosage contributing positively to face the undesired fouling of RO systems. The degree and frequency of fouling vary widely from one membrane system to another. Fouling to the point of cleaning being required can occur as limited as once per year or as frequently every day.
The foulants can be classified into four main categories:
- dissolved solids,
- suspended solids,
- Biological Organics
- Non biological organics.
Biological fouling continues to be a major unresolved problem for membranes and systems as the most common RO-membrane types in use today are attacked and degraded by chlorine and according to public literature by other oxidizing agents. Chlorine is commonly used as a feed water disinfectant. However it must be removed from the feed water prior to entering the RO. system. Without a disinfectant present in the water, microorganisms colonize and form a biofilms in the RO system.
The general practice is that the RO membranes have to be removed from service and cleaned. Thus the biofilms causes a reduction in membrane performance and membrane damage leading to higher maintenance and system operating cost. The main objective of CDD-5000 disinfection treatment is to treat a membrane separation system efficiently to control biofilm formation by extremely low levels of CDD-5000 solution without adversely affecting the RO membrane.
Resin sanitation –
An ion-exchange resin or ion-exchange polymeris an insoluble matrix (or support structure) normally in the form of small (1–2 mm diameter) beads, usually white or yellowish, fabricated from an organic polymer substrate. The material has highly developed structure of pores on the surface of which is sites with easily trapped and released ions. The trapping of ions takes place only with simultaneous releasing of other ions; thus the process is called ion exchange.
The two major types of treatment applied to water are water softening – the replacement of ’hard’ ions such as Ca2+ and Mg2+ by Na+ and demineralization – the complete removal of dissolved minerals.
Adsorption of organic matter
One of the common problems results from the presence of organic matter in water supplies. Untreated water from lakes and rivers usually contains dissolved organic materials derived from decaying vegetation which imparts a yellow or brown color. These substances can become irreversibly adsorbed within the anion beads, reducing their exchange capacity and leading to a reduction in treated water quality. Removal of organics prior to demineralization is usually achieved by flocculation with alum or ferric salts followed by filtration which removes the metal hydroxide floc and the co precipitated organic compounds. This treatment also removes any fine silt which represents another source of resin fouling. Both organic and iron fouled units can be chemically cleaned on site but complete removal of impurities is rare and resin performance usually suffers after fouling.
Organic contamination from the resin
The resins themselves can be a source of non-ionized organic contamination. New commercial grade resin often contains organics remaining after manufacture, while very old resin will shed organic fragments as the polymer structure opens up very slowly (decrosslinkage).
Resin beds do not act as filters for the removal of bacteria or other micro-organisms. They very often tend to worsen such contamination as traces of organic matter, which invariably accumulate, constitute a nutrient source for continual growth. When sterile water is required, it can be obtained by treating the demineralised water by non-chemical means such as heat, ultra violet irradiation or very fine filtration. Resins beds cannot be decontaminated with disinfectants such as chlorine as chlorine damages resins.
Sanitation / Disinfection of Ion Exchange Resins: CDD 5000 is a user-friendly chemical that can be used to sanitize ion exchange resins with no adverse effects on the capabilities of the resin.
CDD 5000 is non-corrosive. It has no effect on Ion Exchange Resin, Low Toxicity, High Microbial Killing efficacy, No pH Sensitivity, Easy Residual Monitoring etc.