Method for the treatment of water and wastewater

A method for the treatment of water or wastewater, having impurities therein, by filtration through two moving bed granular media filter stages disposed in series, comprising:

• feeding of said water/wastewater as a first influent through first feed pipes to first stage granular media filters comprising granular filter media, wherein said first influent is filtered in said first stage granular media filters to produce a first effluent;
• feeding said first effluent as a second influent through second feed pipes to second stage granular media filters comprising granular filter media, wherein said second feed pipes are provided with first valves to allow or prevent the feeding of said second influent to said second stage granular media filters and wherein said second influent is filtered in said second stage granular media filters to produce a second effluent,
• wherein the method includes intermittent washing of the granular filter media of said second stage granular media filters by discontinuing the feeding of said first effluent as a second influent through said second feed pipes to said second stage granular media filters, and instead feeding wash water to said second stage granular media filters to wash the granular filter media of said second stage granular media filters,
• wherein the second stage granular media filters are operated, using said first valves, such that the feeding of said first effluent as second influent to said second stage granular media filters is discontinued during said intermittent washing, and
• wherein said wash water for washing of the granular filter media of the second stage granular media filters consists of water produced as second effluent from another second stage granular media filter.