Study On Solid-liquid Separation Technology For Anaerobic Fermentation Slurry Of Scaled Swine Farms

Basing on widely knowing the domestic status quo of wastewater treatment for scaled swine farms and the popular disposal technologies of piggery wastewater around the world, aiming at the problem of post-treatment for anaerobic fermentation slurry in swine farms that should be immediately solved, taking the present economical and technological condition of China into consideration, this paper put forwards that the new method "Flocculation→Sedimentation by inclined plate setter→Dewatering by drying bed→(AF)" is a promising solution. By this method, not only the post-treatment problem can be solved, but also reclaim the valuable swine resource as well as produce favorable social and economical benefits.In fact, the key point and difficulty of this new method are lie with the solid-liquid separation for anaerobic fermentation slurry. Therefore, the subject firstly picks inclined plate setter as a research object, because this sedimentation facility will ensure that the solid-liquid separation for anaerobic fermentation slurry works well in the first stage. Secondly, setting drying bed as another research object which may guarantee the accomplishment of solid-liquid separation in the last stage.For the inclined plate setter, after analyzing the problems in practice, this paper designs innovative triangle bars to improve the inside flow pattern of counter flow inclined plate setter, which may make up its dynamical defects. The experiment shows that, because of commutating flow and water-sludge separation of triangle bars, the improve one can not only solve the practical problems such as odds of water quality in subareas and difficulty in sludge removal, but also increase surface load and upgrade performance. Anyway, the innovative design for inclined plate setter may proved to be an ultimately solution for the problems occurred in engineering application. Under normal flow rate 0.2m~3/h and 0.25m~3/h, the NTU of traditional inclined setter is obviously higher than the improve one, according to the testing order, the amplitudes are 17.89%, 23.72%, 66.52% and 90.53%. It means that the performance of solid-liquid separation of improved settler is better than the tradition one and comparative advantage will be more evident with the increase of flow rate. Under abnormal flow rate 0.35m~3/h, "penetration" occurs in traditional settler and that the system doesn't work, but "penetration" doesn't happen in improved one and it's system still work well, the NTU of traditional settler is higher than improved one 57.41% and 178.96% respectively; for the same size of two types of settler, the maximal flow rate of traditional one is 0.32m~3/h, and the improved one is 0.41m~3/h, then the surface load of improved one will higher than traditional one 28.13%.For the drying bed, through deeply analyzing the speciality of sludge separated by inclined plate setter, the paper educe that the drying bed is appropriate choice for sludge dewatering method. Base on the fundamentals of drying bed, the dewatering experiment can be divided into two stage infiltration and evaporation. In the stage of infiltration, since the height of injected sludge(A), the solid content of injected sludge(B) and the rate of mixing(C) are key factors which affect the rate of dewatering, this paper originally carried out there factors and there levels of orthonormal experiment. The experiment's results show that C is the most distinct factors that affect rate of dewatering; A is the second is the second one; B's effect is little and the optimum factor and level combination is A(30)B(0.91%)C(10). Then, the validated experiments show that the solid content of cake is 21.13% which is higher then any of combination in the former orthonormal experiment. In the stage of dryness, this experiment takes the temperature and the rate of airflow as researching factors, and that results show that the rate of dryness will increase if increasing the temperature or the rate of airflow. After a 7-day's work cycle (2 days' infiltration and 5 days' evaporation), the solid content of cake increases to 34.36%～39.65% which is up to the demand of storage or transport.