Experimental study on filtrating and backwashing of sandy beds in micro-irrigation filter

Through the experiment of filtrating and backwashing of grit filter media in micro-irrigation, the change rule of water turbidity with the filter time was analyzed and the calculation method of the filter ratio of media to water turbidity from five different raw water concentrations was put forward at the condition of five filter rates and five backwashing rates. Results show that it can shorten the time of the backwashing water turbidity closing to the clear water turbidity by increasing the backwashing rates. The process of backwashing can be completed in 6～7 minutes at the normal rates. It is in direct relationships between raw water turbidity and filter water turbidity, between the turbidity of filtrated water and filtrate rates. The filtrate ratio of turbidity is in 40%～60% when raw water concentration changes from 0.1‰ to 1‰. Similarly, the filter layer has a mature stage and the turbidity of filter water is changing.