Method and apparatus for measuring the fouling potential of membrane system feeds

A method of determining the optimum antifoulant concentration and cleaning interval for a reverse osmosis membrane, comprising the steps of:

• providing samples of a liquid to be purified in a reverse osmosis system, the samples having a range of antifoulant concentrations added;
• measuring the zeta potential for each sample;
• selecting the preferred concentration of antifoulant as that which provides the lowest zeta potential;
• preparing a cleaning frequency sample of the liquid to be purified with the preferred antifoulant concentration;
• passing the cleaning frequency sample across one side of a membrane, so that a fraction of the cleaning frequency sample passes through the membrane as a permeate, the membrane being selected such that it passes dissolved matter in the permeate but does not pass colloidal material;
• measuring the rate of change in flow of the permeate of the cleaning frequency sample through the membrane as a function of time;
• and
• determining the cleaning frequency of the cleaning frequency sample from a preexisting correlation, using the rate of change in flow of the permeate as a function of time.

A method of determining the cleaning interval for a reverse osmosis membrane having molecular sieve layer, comprising the steps of:

• providing a cleaning frequency sample of a reverse osmosis feed liquid;
• passing the sample across one side of a cleaning frequency membrane, so that a fraction of the cleaning frequency sample passes through the cleaning frequency membrane as a permeate, the cleaning frequency membrane being selected such that it passes dissolved matter in the permeate but does not pass colloidal material at a rate relatively rapid compared to said sample being passed through said reverse osmosis membrane;
• measuring the rate of change in flow of the permeate of the sample through the membrane as a function of time;
• and
• determining the cleaning frequency of the reverse osmosis membrane, the reverse osmosis membrane comprising the same membrane material as used in the cleaning frequency membrane of the step of passing, from the rate of change in flow of the permeate as a function of time.

Apparatus for use in determining the required cleaning frequency for a reverse osmosis filter element, comprising:

• means for supplying a flow of a liquid capable of being purified by a reverse osmosis membrane having a molecular sieve layer;
• and
• a test cell having
• a cleaning frequency membrane constructed and arranged to pass dissolved matter in a permeate but to not pass colloidal material at a rate relatively rapid compared to said liquid being purified by the reverse osmosis membrane,
• an inlet on a first side of the cleaning frequency membrane for introducing a flow of the liquid to be purified to a first side of the cleaning frequency membrane,
• a concentrate outlet on the first side of the cleaning frequency membrane disposed so that the flow of liquid introduced from the inlet contacts the first side of the cleaning frequency membrane in flowing to the concentrate outlet, and
• a permeate outlet on a second side of the cleaning frequency membrane.