Optimizing Conditions of Coagulation for Removal of Natural Organic Matter (NOM) : Comparison of Removal Efficiency of NOM When Using Bench-Scale Inline Coagulation Over Ultrafiltration and Classical Jar Tests

Abstract: Abstract The removal of Natural Organic Matter (NOM) from water supplies is crucial for the provision of clean, safe drinking water. Lab-scale experiments have been extensively utilized in water treatment facilities to optimize this process. The most used lab-scale method is known as jar test. However, with emerging membrane filtration, lab-scale inline coagulation has been recently utilized to mimic the inline coagulation over membrane filtration in water treatment plants (WTPs).     This study aims to compare the jar test with inline coagulation micro pilot methods from different aspects, including the NOM removal, time, and cost needed for each process. Three case studies were conducted using different water sources in Sweden: Katrineholm, Mälaren, and Mjörn.     In the experiments conducted to find the optimal NOM removal condition, the inline coagulation micro pilot method outperforms the jar test in terms of removal efficiency. In the Katrineholm case, the micro pilot method with a coagulant dosage of 4.5mg/l Al at pH 6.7 achieved removal efficiencies of 63% for fluorescent dissolved organic matter (fDOM), whereas the jar test showed 60% for fDOM but with a significantly higher coagulant dosage (7mg/l) . In the Mälaren case, the micro pilot method using a dosage of 2.5mg/l Al at pH 6.4 yielded removal efficiencies of 62% for UV254, absorbing organic matter and the jar test showed almost the same removal (64%) for UV254 but with a significantly higher coagulant dosage. Finally, in the Mjörn case, the micro pilot method with a coagulant dosage of 3.5mg/l Al at a pH of 6.6 resulted in removal efficiencies of 76% for UV254, the jar test also resulted in 76% for UV254 at the same pH level.     While the micro pilot method showed better removal efficiencies, it consumed more chemicals compared to the jar test. The micro pilot experiments required higher volumes of coagulant and additional chemical backwashing after each set of experiments. In contrast, the jar test method used lesser quantities of coagulant and chemicals due to the smaller scale of the experiments.     The findings of this study highlight the superiority of the inline coagulation micro pilot method over the jar test for optimizing NOM removal in water treatment processes. Despite the jar test being quicker and more cost-effective, it often required higher coagulant dosages to achieve comparable results. This was mainly because jar test demands heavy and large enough flocs to be removed from the water. Conversely, the micro pilot method, although more time-consuming and costly, provided more precise coagulant dosage control, resulted in higher removal efficiencies, and offered a more comprehensive understanding of the coagulation process. This is achieved by using a sensor called EXO sensor, which allows for immediate monitoring of the treatment results.