斜管沉淀池布水均匀性模拟计算与工艺参数分析

水量负荷的增大和水质标准的提高,迫使许多水厂不得不将平流沉淀池改造为斜管沉淀池,然而改造过程中所遇到的斜管布水均匀性问题一直没从理论上得以解决。通过建立包括长宽比、斜管管径、布水区高度等多个影响布水均匀性因素的水力学方程,定量分析了各种因素的影响规律。模拟计算结果表明:沉淀池长宽比(L/B)对均匀布水性影响最大,当L/B接近6时,布水渠末端的斜管流量极小,布水极不均匀;增大布水渠高度和沿池长方向上减小斜管管径有利于提高布水均匀性。据此在L/B较大的平流沉淀池改造工程中可采取由沿宽度方向布水改为沿长度方向,将沉淀池分格改造为多个斜管沉淀池以及斜管管径沿布水方向由小变大等技术措施提高布水均匀性。

Theoretical analysis on water distribution uniformity and determination of technological parameters of inclined sedimentation tanks

With the raising of water quality and quantity, many horizontal flow tanks being used have to be rebuit into inclined pipe sedimentation tanks. But the non-uniformity of water distribution of the inclined tanks remains unsolved theoretically and how the parameters affecting the non-uniformity are still not very clear. On the basis of hydraulic concept, several concerned hydraulic models of the inclined tanks were established including the ratio (L/B) of tank's length (L) to width (B), diameter of the inclined pipes, the height of the water distribution area etc. The models were used to simulate and analyze the effects of the parameters on water distribution uniformity of the tank (WDUT). The computation and simulation results show that the WDUT was most affected by the ratio (L/B), and there was almost no flow rate through the tube at the end row of the tank, which led to a very poor WDUT when the ratio reached to 6. It was also concluded that increasing the height of the distribution channel and reducing the diameter of inclined tube would improve WDUT. Therefore some technique methods, such as altering the influent direction along the length side instead of along the width side, dividing the horizontal flow tank into several smaller tanks as well as increasing the tube diameter, can be used for improving water distribution uniformity of the tank for a greater ratio of L/B.