DHI, Gustav Wieds Vej 10, DK, 8000, Aarhus C, Denmark.
Water Sci Technol. 2009;60(9):2439-45. doi: 10.2166/wst.2009.692.
Most wastewater treatment plants have several secondary clarifiers or even more sets of clarifiers including several secondary clarifiers, and in practice it is a well known problem that equal distribution of the load to the single clarifier (or set of clarifiers) is very difficult-not to say impossible-to obtain. If the problem is neglected, quite a big percentage of the total clarifier capacity-measured as the max. allowed hydraulic load-can be lost. Further, return sludge rates are seldom controlled by any other means than as a (typically too high) percentage of the inlet to the wastewater treatment plant-giving a varying and too low suspended solids concentration in the return sludge, which again can lead to an unnecessary use of polymer in the pre-dewatering of the surplus sludge taken from the return sludge. A control of the return sludge rate divided into two parts - control of the total return sludge flow and control of how the total flow shall be distributed between the secondary clarifiers - is able to solve the mentioned problems. Finally, as shall be demonstrated on full scale wastewater treatment plants, a considerable increase of the hydraulic capacity of the treatment plants can be obtained.
大多数污水处理厂有几个二沉池甚至更多套的澄清器，包括几个二沉池，在实践中，一个众所周知的问题是，将负荷均匀地分配到单个澄清器（或一组澄清器）是非常困难的——更不用说不可能实现了。如果忽略这个问题，相当大比例的总澄清器容量——以最大允许水力负荷来衡量——可能会损失。此外，回流污泥率很少通过其他方式控制，而只是作为污水处理厂进水的一个（通常过高的）百分比——导致回流污泥中的悬浮固体浓度变化且过低，这又可能导致在从回流污泥中提取的剩余污泥的预脱水过程中不必要地使用聚合物。将回流污泥率分为两部分进行控制——控制总回流污泥流量和控制总流量在二沉池之间的分配方式——能够解决上述问题。最后，正如在全规模污水处理厂所证明的那样，可以获得处理厂水力容量的显著增加。
