Method for controlling the integrity of a nanofiltration or reverse osmosis module, or module system

1. 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.

2. A method according to claim 1 , wherein the system comprises at least a plurality of modules mounted in parallel, the method comprising:

measuring the value of the concentration of that dissolved compound in similar downstream zones of each module of said plurality of modules,

comparing said measured values for each module,

identifying those of said values which are the least values, and identifying as reference value a value at least approximately equal to said least values,

recognizing the existence of a defect in one of the modules mounted in parallel when the measured value for that module is greater than reference value.

3. A method according to claim 1 , wherein the system comprises a plurality of series of modules mounted in parallel, said method comprising:

measuring the value of the concentration of that dissolved compound in similar zones of each series,

comparing said measured values for each series,

identifying those of said measured values which are the least values, and identifying as reference value a value at least approximately equal to said least values,

recognizing the existence of a defect in one of said series when the measured value for that series is clearly greater than that reference value.

4. A method according to claim 3 , further comprising:

measuring the value of the concentration of said dissolved compound in a plurality of zones chosen along a series of modules,

for each value of the concentration measured for a given zone, taking a reference value substantially equal to the value of the concentration measured for the zone situated immediately upstream of that given zone or, it lacking, of the zone situated immediately downstream thereof, and

recognizing the existence of a defect in a given zone when the value which is measured there is greater than the associated reference value.

5. A method according to claim 4 , wherein the zones chosen along the series of modules comprise at least one zone downstream of each module and one zone of each connector connecting a module to the following one.

6. A method according to claim 4 or 5 , wherein the dissolved compound of which the concentration is measured is sulfate.

7. A method according to any one of claims 3 to 5 , wherein the value of the concentration of that dissolved compound is measured in a sample of fluid taken from a zone containing fluid coming from each module of that series.

8. A method according to claim 7 , wherein the dissolved compound of which the concentration is measured is sulfate.

9. A method according to claim 1 , wherein the system comprises at least one series of modules, said method comprising:

measuring the value of the concentration of that dissolved compound in a plurality of zones chosen along the series of modules,

for each value of the concentration measured for a given zone, taking a reference value substantially equal to the value of the concentration measured for the zone situated immediately upstream of that given zone or, if lacking, of the zone situated immediately downstream thereof, and

recognizing the existence of a defect in a given zone when the value which is measured there is greater than the associated reference value.

10. A method according to claim 9 , wherein the zones chosen along the series of modules comprise at least one zone downstream of each module and one zone of each connector connecting a module to the following one.

11. A method according to any one of claims 1 , 9 , or 10 , wherein the system comprises at least one series of modules, and the value of the concentration of that dissolved compound is measured in a sample of fluid taken from a zone containing fluid coming from each module of that series.

12. A method according to any one of claims 1 , 2 or 3 , wherein the dissolved compound of which the concentration is measured is sulfate.

13. The method according to claim 12 , wherein the sulphate concentration is less than approximately 100 mg/L.

14. A method according to claim 11 , wherein the dissolved compound of which the concentration is measured is sulfate.

15. A method according to claim 9 or 10 , wherein the dissolved compound of which the concentration is measured is sulfate.