TECHNOLOGY FOCUS - ENVIRONMENT - Preferred Components: The solid content rate in the diluted anaerobic fermentation raw material is 6-8%. Preferred Method: The method further comprises: conveying the floated residue filtered by a mechanical barrier of a barrier ditch to an additional vehicle by the belt-type conveyer to discard; allowing the nutrient filtered from the floated residue by the mechanical barrier into an acidifying tank; conveying the hydrolyzed and acidified nutrient to a fermentation tank of an anaerobic fermentation reactor by a material feeding pump; conveying the settled sand and mixed raw material liquid into a sand and water separator and separating; and discharging the dehydrated settled sand through a sand outlet to flow into a sand storage tank.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The upper part of the pretreatment tank is equipped with an upper agitator (6) and a lower agitator (16) on the lower part to agitate the anaerobic fermentation raw material to achieve sedimentation and delamination. The agitation power of the upper agitator and the lower agitator is 3-16 kW, and rotational speed is 20-80 revolutions/minute. The pretreatment tank comprises a material inlet installed on the sidewall of the pretreatment tank and interconnected with the pretreatment tank, through which the anaerobic fermentation raw material is conveyed to the pretreatment tank. A sand precipitating hopper is installed at the pretreatment tank bottom, and used for precipitating settled and delaminated sand. The sand and water separator is extended into the sand precipitating hopper bottom. The lower part of the material inlet is inserted below a liquid level of the pretreatment tank. The lateral side of the lower part of the material inlet and the sidewall of the pretreatment tank are located on same vertical side. The material inlet adopts a slope shape with 0.3- 1.8 slope degree, which is washed by biogas liquid backflow. The pretreatment tank adopts a square shape with a length to width ratio of 2-6 and the sidewall of the pretreatment tank is extended into one side of the sand and water separator to an inclined side. The barrier ditch is equipped inside with a mechanical barrier. A belt-type conveyer is arranged below the mechanical barrier to filter and discharge the floated residue. The belt-type conveyer is installed on the ground and the discharged floated residue is conveyed to additional vehicles by the belt-type conveyer. The grain diameter of the floated residue is 10-50 mm. The sand and water separator comprises a sand discharging pipe. One end of the sand discharging pipe is extended into the sand precipitating hopper at the bottom of the pretreatment tank, and other end is extended outwards from the pretreatment tank, raised above the ground. The sand discharging pipe is internally equipped with a spiral pusher. An electric motor is installed on one end of the sand discharging pipe, which is extended outwards above the ground, and used for driving the spiral pusher. A sand outlet is set on one end of the sand discharging pipe, which is extended outwards above the ground. A sand storage tank is installed below the sand outlet, and dehydrated sand is discharged from the sand outlet to the sand storage tank. The rotation power of the electric motor is 3-20 kW and the rotation speed is 150-300 revolutions/minute. The conveying length of the sand discharging pipe is 3-15 m, and conveying angle is 0-60 degrees . The diameter of the sand discharging pipe is DN100-DN400 and the grain diameter of the settled sand is 1-60 mm. The device further comprises an acidifying tank interconnected with the pretreatment tank through the barrier ditch, and a pump tank located on one side of the acidifying tank. A material feeding pump is set in the pump tank. A material discharging pipe is connected with the material feeding pump and extended into the acidifying tank. A material feeding pipe is connected with the material feeding pump and is used for conveying the anaerobic fermentation raw material. The filtered floated residue from the nutrient is hydrolyzed and acidified in the acidifying tank and conveyed to a fermentation tank of an anaerobic fermentation reactor through the material discharging pipe, the material feeding pump and the material feeding pipe.