Method and apparatus for microfiltration

A method comprising the steps of:

• flowing pressurized water including a precipitate through a substantially tubular semipermeable membrane comprising sub-micron filtration media and having an inner surface and an outer surface;
• and
• collecting a filtrate from the outer surface of the membrane,
• wherein the filtrate contains a concentration of dissolved precipitate below the solubility limit of the precipitate and wherein a pressure differential across the membrane is greater than 100 psi.

An apparatus comprising:

• at least one substantially tubular semipermeable membrane comprising sub-micron filtration media and having an inner surface and an outer surface, the inner surface defining a lumen;
• an inlet in communication with the lumen of the substantially tubular membrane;
• a momentary dynamic membrane comprising calcium carbonate disposed on a portion of the inner wall of the substantially tubular semipermeable membrane;
• a first outlet in communication with the lumen of the substantially tubular membrane;
• and
• a second outlet in communication with the outer wall of the substantially tubular membrane, wherein the membrane is capable of withstanding a pressure differential of greater than about 100 psi.

A method of pretreating water including at least one species of cation comprising the steps of:

• adding an anion to the water at a level adequate to precipitate out a portion of any cations present in the water;
• forming a precipitate;
• passing the water through a substantially tubular semipermeable membrane comprising sub-micron filtration media, at turbulent flow;
• and
• recovering a filtrate from the substantially tubular semipermeable membrane, wherein the filtrate comprises dissolved precipitate at a concentration below the solubility limit of the precipitate.

A method of pretreating water including at least one species of anion comprising the steps of:

• adding a cation to the water at a level adequate to precipitate out a portion of any anions present in the water;
• forming a precipitate;
• passing the water through a substantially tubular semipermeable membrane comprising sub-micron filtration media, at turbulent flow;
• and
• recovering a filtrate from the substantially tubular membrane, wherein the filtrate comprises dissolved precipitate at a concentration below the solubility limit of the precipitate.