The S.D.Warren Westbrook Mill is an integrated bleached kraft pulp and paper mill located in Westbrook, Maine. The mill currently treats an average wastewater flow of 68 MLD using primary sedimentation and an activated studge process with pedestal-mounted, surface aerators. In the spring of 1996, Woodard & Curran began a project with S.D.Warren to develop an improved method of reducing TSS levels in the treatment plant effluent. The first step in the process was to evaluate the hydraulic efficiency fo the secondary clarifiers, to see how effective, if at all, the installation of baffles would be. Both slug and continuous dye tests were performed in each of the two clarifierd. Visual observation revealed the presence of significant floc carry-over. The results of the dye testing were revealing. The slug dye test results demonstrated that the two identical clarifiers suffered from significatnt short circuiting currents, which were impairiring TSS removal efficiency. The continuous dye test was used to pinpoint the location of the currents. Based on these results, it was decided that peripheral baffles would be the most effective method of mitigating the currents. The baffles were installed in one of the two clarfiers in October 1997, allowing side-by-side comparison of two clarifiers, one with baffles and one without. There were noticeabvle visual differences regarding floc carry-over between the two clarifiers. The results were impressive, as the baffled clarifier averaged 25
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