Pilot Test Of A Multi-storey Slab Unit Assembled Sedimentation Tank And Study On Its Optimization Approach

In recent years,it has been found that increasing the concentration of activated sludge can significantly improve the sewage treatment capacity of system,so the high concentration activated sludge process was invented.There are many ways to achieve high concentration activated sludge process,comparison studies proved that using the secondary sedimentation tank wiht low hydraulic surface loading and high sludge recycle ratio can achieve the goal,this method is simple and low cost.In view of this,invent a modified sedimentation tank wiht low hydraulic surface loading,it can be used in municipal wastewater treatment,water treatment and industrial wastewater treatment,this will have great practical significance.In this paper,the pilot test proved that the multi-storey slab unit assembled sedimentation tank has a strong p sedimentation function.It is found that,when it is used as ordinary sedimentation tank it has a large hydraulic surface loading,that can reduces the occupying area of sedimentation tank;when it is used as secondary sedimentation tank it has a strong ability to maintain the activated sludge concentration of system.The key results and conclusions of the pilot test were as follows:when the pilot test sedimentation tank is installing multi-storey slab unit,the sedimentation tank can withstand a higher hydraulic surface loading.under the conditions of sludge settling in stage 5 and stage 7,the relation between the multipl of the critical hydraulic surface loading(n)and sludge concentration(X)can be represented as n=5.1553X-0.147;For the pilot test equipment,the sludge recycle ratio has no effect on the relationship between hydraulic surface loading and maintainable sludge concentration when it greater than 1;When the sludge concentration is less than 14g/L,reduce the rotational speed of sludge scraper in multi-storey slab unit can significantly improve the settling capacity of sedimentation tank,when he sludge concentration is greater than 14g/L,the effect was not obvious.As the pilot test did not carry out the research on optimization,So using the CFD software FLUENT to establishing three-dimensional model of multi-storey slab unit assembled sedimentation tank.In the case of different parameters,launching numerical simulation research on flow regime and sludge sludge particle concentration field in sedimentation tank.It is found by numerical simulation that themulti-storey slab unit can strengthening precipitation,when the number of slab was 4,the precipitation effect of the sedimentation tank is the best.Under the optimal condition of the number of slab was 4,The effect of high concentration sludge sedimentation as good as low concentration sludge;when the sedimentation tank with the length was 8m and installed double slab unit,The maximum hydraulic surface loading the sedimentation tank can be increased by 46%,this fact suggests that that it is possible to apply a multi-storey slab unit to longer tank type.Comprehensive analysis of pilot test results and numerical simulation results,put forward the following optimization approach of pilot test equipment:In accordance with the layout of slab unit of the pilot test equipment,the recommended number of slab is 4;Appropriate increase the distance between the slab back end and back wall of sedimentation tank,it is recommended to use 1.5m to 2m;In the future,the design and operate of equipment should use smaller Sludge recycle ratio and lower slab scraper rotational speed,this will reduce the cost of equipment and operating energy consumption.