Microbial growth control of pharmaceutical purified water equipment

In the pretreatment system of purified water equipment, the methods to control microbial growth include regular disinfection, ultraviolet (UV) light, chlorine / chloramine, reducing agent and chlorine dioxide.

1. Regular disinfection: use the scheduled schedule or the method of regular disinfection as required, including: thermal disinfection, chemical reagent disinfection, medium regeneration or replacement, washing or discharge. By heating, the indicator organics in USP are killed above 60 ℃, and most of them will not proliferate. When the temperature is higher than 80 ℃, it will be all killed. The disinfection time at this temperature is 1-2 hours, and the total cycle time including heating and cooling time may be 4-8 hours. The specific temperature and duration need to be determined according to the characteristics of specific components or equipment. The method of thermal disinfection is usually used in carbon bed, filter and distribution system.

Chemical disinfectants include: hydrogen peroxide, iodine, amino compounds and organic or inorganic high oxidation compounds, the disinfection time is 0.5-4 hours, and additional disinfectant adding time and washing time from the system. The total cycle time may be 8 hours. The specific concentration and disinfection time of the agent need to be determined according to the characteristics of specific components or equipment.

In order to reduce the microorganism to the minimum, the temperature control can extend the interval time of two disinfection. Because the temperature of 15 ℃ will reduce the growth of microorganism, prevent the retention and blind tube can also reduce the growth of microorganism to the minimum. During the shutdown period, each operation unit can use the circulation pipeline.

2. UV lamp: because of its convenient use, UV lamp treatment is a very popular form of microbial control and disinfection. When water is exposed to UV light at a controlled flow rate, the UV light can inactivate the DNA of microorganisms, prevent replication and therefore reduce the use of bacteria. In the pretreatment system, UV is used when chlorine / chloramines and thermal methods are ineffective or not feasible. The water supply into the UV must be free of suspended solids, because they can "shield" the bacteria from full contact with the UV light. UV is used to control the water supply of RO and the circulating water of non ammonia treatment during system standstill. UV has no residue in the treated water, so it is only effective when UV can directly contact with microorganisms.

3. Chlorine: molecular ammonia has adverse effects on the components in the water purification system, which will lead to membrane deterioration used in ultrafiltration and RO membrane. Although ammonia concentration in drinking water is appropriate, it can still lead to degradation, embrittlement, loss of capacity and resin degradation of deionized resin. It will also corrode stainless steel, especially at elevated temperature, and may be carried in the distillation system. The product does not contaminate the product, so most systems that produce purified water consider removing chlorine at a certain point.

Advantages: low cost; general treatment method; consistent with municipal water treatment; maintain residue; easy to detect and maintain content level;

Disadvantages: THMs can be produced; it has no effect on all organic matters; residual chlorine is not acceptable in many final treatment systems.

The methods of chlorine removal have the functions of active carbon and reduction. The advantages of active carbon in chlorine removal are: it can remove organic matters with low molecular weight; remove color; it can effectively remove chlorine; the technology is not complex; the cost is relatively low;

Disadvantages: there is a high possibility of increasing the biological load; the medium cost is high; the fallen fine powder needs to be filtered in the downstream; the invalid activated carbon needs to be replaced regularly;

4. Reduction: the addition of reducing agent (sulfite) can reduce chlorine or chloride, its advantages: it can effectively remove chlorine; the cost of specific heat disinfection is low; there is no requirement for regeneration or replacement; the operation cost is low;

Disadvantages: technically more complex; there are some chemical reagent treatment including: sodium bisulfite and acid / alkali regulating pH; due to the possibility of microbial growth in the sulfite adding tank, it is necessary to configure sulfite solution frequently; the cost of feeding system and monitor is higher; the cost is higher than that of disposable carbon;

5. Chlorine dioxide: chlorine dioxide is a highly effective oxidant, its oxidation capacity is 2.3 times that of chlorine. When it interacts with organics, it will take place oxidation-reduction reaction instead of replacement. The result is that the organics of polymers will be degraded into organic acids, H2O and CO2, while chlorine dioxide will be reduced into chloride ions, which will hardly form mutagenic and carcinogenic substances such as trichloromethane and carbon tetrachloride. It is the biggest advantage compared with chlorine.

Another characteristic of chlorine dioxide is that its efficacy is sustained when it is used for sterilization, which can ensure the inhibition of microbial reproduction in a long time.