Sludge Blanket Clarifier For Coagulation of Turbidity and Organics: Design, Operation and Scale Effects

摘要

The intrusion of natural organic matter (NOM) in source waters due to climate change has called for the development of robust systems for the removal of not only inorganic turbidity but also of NOM. In this study, a pilot-scale sludge blanket clarifier was designed for the coagulation of inorganic turbidity and organics, describing theory and practice of solids contact clarifiers. The hydraulic parameters such as velocity gradient and detention time were scaled up from jar test to pilot-scale system. Synthetic sample waters were prepared using kaolin and humic acid as source of inorganic turbidity and organics. respectively, to incorporate the effects of fluctuating organic matter and inorganic turbidity. Optimized doses oj'PACl from jar tests were replicated on the pilot plant. The regression coefficient was used to establish the similarities in the removal trends with varying input water characteristics between bench-scale and pilot-scale systems. It was found that for TOC removal trends, jar test closely represented the sludge blanket clarifier. The removal efficiencies of turbidity, TOC, DOC and UV_(254) were also analyzed. The turbidity removal was 20-81%, and the TOC removal was 11-84%. The mechanisms of removal were elaborated by measuring pH, alkalinity andzeta potential before and after the treatment. It was found that the removal of hydrophobic TOC occurred dominantly by adsorption and entrapment, and the removal of hydrophilics occurred dominantly by charge neutralization. The challenging aspects of operation were the maintenance of blanket depth, operation at low input turbidities, and channeling of loosely flocs.