Patent ID: 7216529

Claim:
A method of checking during operation the integrity of a system of nanofiltration or reverse osmosis modules adapted for a treatment of a supply water retaining living microorganisms and of detecting leaks of living micro-organisms in said systems of modules, each module comprising nanofiltration or reverse osmosis membranes and connection joints of these membranes, comprising: choosing in the supply water to be treated a dissolved compound which is in significant quantity in the supply water and which is normally strongly kept back by the membranes said compound being such that an increase in its concentration is detectable sooner than an increase in the concentration of the microorganisms passing through leaks is detectable, thus indicating degradation of the membranes or connection joints, measuring the value of the concentration of the compound in a downstream zone of a module of that system, comparing that measured value with a reference value, and recognizing the existence of a defect which lets through a detectable quantity of microorganisms in that zone of the system when that measured value is greater than the reference value.