New and Innovative Design of a Grit Chamber for Applications in Municipal Wastewater Treatment

废水处理中至关重要的第一步是从废水处理厂（WWTP）的进水中去除无机砂砾。在加拿大，污水处理厂经常使用曝气沉砂池进行沉砂，这需要在同一个沉砂池中产生两种不同的水流。需要高能湍流来将有机涂层与重无机砂砾颗粒分离，并且需要静止流来允许砂砾颗粒沉降。在相同的腔室中产生这些不同的流动条件在设计和操作方面都是非常困难的。这个问题可以通过在分开的沉砂池中执行这两个功能来解决，这将比现有的曝气沉砂池更有效和更经济。在加拿大，有许多污水处理厂已经通过增加二级和三级处理工艺进行升级，以达到国家污水标准，但没有修改其除砂系统。因此，如果污水处理厂要能够科普与城市和工业发展相关的日益大量的脂肪、油和油脂（FOG）和砂砾，则迫切需要升级现有的砂砾去除系统。拟议的NSERC CRD计划将开发一种创新的沉砂池设计，该设计将比现有的沉砂池更有效，容量更大。建议增加配备交叉射流的预混合室，这将有效地将FOG与砂砾分离，然后可以在下游沉降室中更有效地去除清洁的砂砾。将进行中试规模实验，以确定在预混合室中产生大分散数的交叉射流配置和操作条件，以及确定产生大绝对速度梯度和均匀流场的操作条件。此外，将在金条污水处理厂进行实验，以确定新的砂砾去除系统在处理真实的废水时是否有效。建议的研究结果可以直接应用到现有的加拿大污水处理厂，以提高砂砾去除效率，提高整个污水处理过程。

A crucial first step in the treatment of wastewater is the removal of inorganic grit from the influent to the wastewater treatment plant (WWTP). In Canada, WWTPs often use aerated grit chambers for grit removal and this requires the creation of two dissimilar flows in the same chamber. An energetic turbulent flow is required to separate organic coatings from the heavy inorganic grit particles, and a quiescent flow is required to allow settling of the grit particles. Generating these dissimilar flow conditions in the same chamber is very difficult in terms of both the design and operation. This problem can be solved by performing the two functions in separate chambers, which would be more efficient and cost effective than existing aerated grit chambers. In Canada, there are many WWTPs that have been upgraded to meet national effluent standards by the addition of secondary and tertiary treatment processes but with no modification of their grit removal systems. Therefore, upgrades to existing grit removal systems are urgently needed if WWTPs are to be able to cope with the increasingly large amounts of fat, oil and grease (FOG) and grit, associated with the growth of cities and industry. The proposed NSERC CRD Program will develop an innovative grit chamber design that will be more efficient and have larger capacity than existing grit chambers. The addition of a pre-mixing chamber equipped with cross-jets is proposed that will effectively separate FOG from grit and this cleaned grit can then be removed more efficiently in a downstream settling chamber. Pilot-scale experiments will be conducted to determine the cross-jet configuration and operating conditions that produce large dispersion numbers in the pre-mixing chamber as well as to determine the operating conditions that produce large absolute velocity gradients and homogeneous flow fields. Moreover, experiments at the Gold Bar WWTP will be performed to determine if the new grit removal system operates effectively when processing real wastewater. The proposed research results can be directly applied to existing Canadian WWTPs to improve grit removal efficiency and enhance the entire wastewater treatment process.