Filtering apparatus and method

A method comprising filtering a liquid having total suspended solids of between 1 and 50 g/L using a liquid-permeable filtering element having first and second faces so as to produce filtered liquid having total suspended solids of no more than 10 mg/L, wherein the liquid-permeable filtering element is movable into at least partial submersion in the liquid and the liquid-permeable filtering element is configured for cyclical movement through the liquid, the method further comprising:

• cyclically moving the liquid-permeable filtering element through the liquid whereby:
• when moved into a first position, an area of the first face of the filtering element is subjected to liquid under pressure and a pressure difference across the liquid-permeable filtering element is greater than 0 and less than or equal to 5.9 kPa, and
• when moved into a second position, the area is not subjected to liquid under pressure or is subjected to liquid at a lower pressure difference, and solids accumulated on the first face of the filtering element are removable by directing at least one jet at the second face of the liquid-permeable filtering element through the liquid-permeable filtering element towards the first face of the liquid-permeable filtering element;
• wherein
• the liquid-permeable filtering element has a pore size between 2 and 40 μm;
• and the method further comprising:
• introducing gas bubbles into the liquid using a gas feeder positioned below the liquid-permeable filtering element in the first position so that when the liquid-permeable filtering element is in the first position and the gas feeder is introducing gas bubbles, the gas bubbles create turbulent motion along the first face of the liquid-permeable filtering element.

Apparatus comprising:

• a liquid-permeable filtering element having first and second faces, the liquid-permeable filtering element movable into at least partial submersion in a liquid, the liquid-permeable filtering element configured for cyclical movement through the liquid such that:
• when moved into a first position, an area of the first face of the liquid-permeable filtering element is subject to liquid under pressure and a pressure difference across the liquid-permeable filtering element is greater than 0 and less than or equal to 5.9 kPa;
• and
• when moved into a second position, the area is not subjected to liquid under pressure or is subjected to liquid at a lower pressure difference,
• at least one nozzle for directing at least one jet at the second face of the liquid-permeable filtering element through the liquid permeable filtering element towards the first face of the liquid-permeable filtering element for removing and/or aiding removal of solids accumulated on the first face of the liquid-permeable filtering element;
• wherein
• the liquid-permeable filtering element includes pores having a range of different pore sizes, the pore sizes being between 2 and 40 μm;
• and
• the apparatus further comprises:
• at least one gas feeder for introducing gas bubbles into the liquid during filtration by the liquid-permeable filtering element with the gas feeder positioned below the first position so that when the liquid-permeable filtering element is in the first position and the gas feeder is introducing gas bubbles, the gas bubbles create turbulent motion along the first face of the liquid-permeable filtering element.