| Sedimentation tank is a kind of structure which can remove suspended matter by gravity in water.With the use of double-deck horizontal flow sedimentation tank in some domestic water plants,optimizing the structure of double level horizontal sedimentation tank and improving the water purification effect of sedimentation tank which can improve water resources and land use efficiency in china have a practical significance.In the present study,we have improved the existing double level horizontal sedimentation tank and designed two new double-deck horizontal flow sedimentation tank with inclined plate structure: double flow horizontal flow sedimentation tank with downward inclined plate structure(A model),double flow horizontal flow sedimentation tank with upward inclined plate structure(B model)and tandem double layer horizontal flow sedimentation tank(model C),and made these three models.We made a model test combined the water inflow in Shihezi area and made a numerical simulation of the flow field.We got the main research results by a comprehensive analysis of model test and numerical simulation:(1)This paper introduce the design principle of the new double-deck horizontal flow sedimentation tank with inclined plate structure and the design parameters of the sedimentation tank model,which can provide a reference for the subsequent design and research of the double level horizontal sedimentation tank.The results of the experiment showed that the sedimentation effect of model A was better than that of model B and model C whether added flocculant or not under the same hydraulic condition.(2)It is a gradual process from the current outflow to the outflow water quality and the time interval from the current outflow to the outflow water quality is about 120 min during the initial operation in the three models which are not included flocculant.The two new double-deck horizontal flow sedimentation tank with inclined plate structure had good operating conditions and stable effluent quality,which can meet the requirements of the continuous operation of the sedimentation tank in practical engineering and achieve a better removal effect after continuous operation of 48 h in the water treatment plant.For the high turbidity water,in order to ensure the higher suspended solids removal rate and take into account the water treatment efficiency,the hydraulic retention time of model A should be set to 70 min and the hydraulic retention time of model B should be set to 80 min.(3)When the flow of effluent was stable with flocculant,the average effluent turbidity of model A was lower than that of model B and model C,the model A was better than model B and model C in reducing turbidity of effluent.In the process of the flowout tends to be stable,the dislodge rate of solid suspended matter of model A is close to model B,the dislodge rate of solid suspended matter of the three sedimentation tank flow model is close to the average after the addition of flocculant,the results show that there is no significant correlation between the removalrate of suspended solids and the dip angle of the bottom plate,and the flow rate has little effect on the removal rate of suspended solids.(4)Two dimensional simulation were carried out of the flow field distribution of double deck settling tank under different inflow.Based on the analysis of the flow field distribution map,it can be concluded that the flow field distribution of model A is better than that of model B and model C,the area of recirculation zone and backwater area of model A were less than model B and model C,the flow field characteristics of model A are better than those of model B and model C,this result is close to the result of the model test that the settlement effect of model A is better than model B and model C.There is a large area of turbulent flow in the flow field of the double layer horizontal flow sedimentation tank,which can be solved through the reasonable layout flow board opening holes and other measures. |
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