Method and apparatus for treating liquid containing impurities

An apparatus for treating a liquid containing impurities, comprising:

• a filtering chamber for receiving liquid containing impurities, the filtering chamber including a lower portion containing granular media and configured to permit the granular media to interact with the liquid containing impurities, thereby removing impurities from the liquid to produce filtrate;
• a filtrate section in fluid communication with the filtering chamber for receiving the filtrate, the filtrate section being in fluid communication with a first outlet for outflow of the filtrate;
• a gas supplying system for delivering gas to the granular media in the filtering chamber for transport of a portion of the granular media to a granular media washer;
• a reject section in fluid communication with the granular media washer for receiving a reject mixture comprising liquid and impurities from the granular media washer, the reject section being in fluid communication with a second outlet for outflow of a portion of the reject mixture;
• and
• a control unit that is configured to determine a condition of transport of the portion of the granular media by determining whether a level of reject mixture in the reject section exceeds a predetermined threshold,
• wherein, upon determining that the level of reject mixture in the reject section exceeds the predetermined threshold, the control unit is configured to send a command signal to the gas supplying system to control delivery of gas to the portion of the granular media.