Microbial load limits for water for pharmaceutical use:

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With optimized water purification system at the final user point it is observed that water has very low microbial load or microbial counts, to avoid a step rise in microbial load with any sudden change in water purification system, step wise validation and monitoring of microbial loads at each points in water system should be undertaken, with which one can set up narrow alert and action limits so as to maintain the final quality of water for pharmaceutical use.

Following is the limits for microbiology at different points in water purification system:

Raw water : It must be of quality of drinking water with complying with
Targeted limit for Microbial load in CFU = Equal or less than 200 cfu/ml
Alert limit for Microbial load in CFU = 300 or readings nearing 300 cfu/ml
Action limit for Microbial load in CUF = 500 or reading nearing to 500 cfu/ml

After prefiltration thought multimedia filters:
Targeted limit for Microbial load in CFU = Equal or less than 100 cfu/ml
Alert limit for Microbial load in CFU = 250 to 300 cfu/ml select one figure
Action limit for Microbial load in CUF = 500 or reading nearing to 500 cfu/ml

After passing through water softner :
Targeted limit for Microbial load in CFU = Equal or less than 100 cfu/ml
Alert limit for Microbial load in CFU = 250 to 300 cfu/ml select one figure
Action limit for Microbial load in CUF = 500 or reading nearing to 500 cfu/ml

After passing through activated charcoal filter:
Targeted limit for Microbial load in CFU = Equal or less than 50 cfu/ml
Alert limit for Microbial load in CFU = 250 to 300 cfu/ml select one figure
Action limit for Microbial load in CUF = 500 or reading nearing to 500 cfu/ml


Limits for feed water for reverse osmosis unit:
Targeted limit for Microbial load in CFU = Equal or less than 20 cfu/ml
Alert limit for Microbial load in CFU = 150 to 200 cfu/ml select one figure
Action limit for Microbial load in CUF = 400 or reading nearing to 400 cfu/ml


Water treated with reverse osmosis:
Targeted limit for Microbial load in CFU = Equal or less than 10 cfu/ml
Alert limit for Microbial load in CFU = 20 to 50 cfu/ml select one figure
Action limit for Microbial load in CUF = 100 or reading nearing to 100 cfu/ml

 Water for injection must be sterile there should not be any microbial count of any kind , as well as it is required to be free from bacterial endotoxin or pyrogen.
Water for injection must be discarded if it is stored for more than 24 hours , that means it must be used with in 24 hours for further process in injectable dosage form manufacturing.

What is CFU:
colony forming unit (CFU) is a unit to express the number or microorganism in any given sample for microbiological examination for its bio burden or total microbial count, it based on the principle that a single viable microbial cell when grown in a suitable dilution in a microbial enrichment media gives rise to one single colony on agar plate, which can be seen with magnifier of with naked eyes..

One ml of water sample is inoculated in microbiological enrichment mediums which can promote microbial growth, a single viable microorganism (bacteria as well as fungi)  in a microbiological enrichment medium grow and form a continuous growth , a single viable microorganism give rise to a single visible microbial colony counting such colony gives number which is very much near to the total number of microorganisms in given 1 ml of sample water being tested, dilution factors and sample preparations must be considered before arriving at the final count.

Also see:

Ultraviolet light as antimicrobial disinfectant in water for pharmaceutical use


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