Abstract
Understanding the character of natural organic matter (NOM) and assessing its impact on water quality is paramount for managers of catchments and water utilities. For drinking-water producers, NOM affects disinfectant demand and the formation of by-products which can have adverse health effects. NOM content in raw waters also has an impact on water treatment processes by increasing required coagulant dosages, reducing the effectiveness of adsorption processes and fouling membrane systems. This study investigated the effects of calcium chloride (CaCl2) as a co-coagulant in Al3+ and Fe3+ assisted coagulation, flocculation and sedimentation processes for NOM-removal from raw water collected from Lake Bolmen, in southern Sweden. Jar tests were conducted at Ringsjö Water Works (WW), a surface water treatment plant (WTP), to investigate the potential reduction in primary coagulants aluminum sulphate (Al2(SO4)3) and ferric chloride (FeCl3). This work shows that CaCl2 can, in certain situations, reduce the need for primary coagulants, which would reduce the environmental impact and costs associated with primary coagulant consumption.
Highlights
Natural organic matter (NOM) is generated through the breakdown of bacteria, algae and both terrestrial and aquatic plants, resulting in a complex mixture of organic substances.In freshwater bodies used as a raw water source for drinking water production NOM needs to be removed, representing a substantial challenge due to changes in seasonal NOM composition
We investigate the effects of using CaCl2 as a co-coagulant aid in the removal efficiency of NOM from raw water obtained from Lake Bolmen, the tenth largest lake in Sweden
Water from Lake Bolmen is currently used as raw water for Ringsjö Water Works (WW), a surface water treatment plant (WTP)
Summary
Natural organic matter (NOM) is generated through the breakdown of bacteria, algae and both terrestrial and aquatic plants, resulting in a complex mixture of organic substances.In freshwater bodies used as a raw water source for drinking water production NOM needs to be removed, representing a substantial challenge due to changes in seasonal NOM composition. The percentage of removal of NOM affects the efficacy of drinking water treatment processes. A comprehensive review of the different methods for the characterization of NOM in relation to drinking water production was published by Matilainen et al [3]. The different existing technologies for water treatment, including NOM removal, have been summarized elsewhere [5,6]. A wide variety of conventional and non-conventional adsorbents have been recently reviewed by Bhatnagar and Sillanpää [7] for their potential in NOM removal from water. The authors showed that modified adsorbents, composite materials and a few nanomaterials have shown promising results for NOM removal from water. A brief overview of the state-of-the-art methods for NOM removal from supply waters was recently published by Callegari et al [8]
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