Arsenic Removal using Manganese Oxide for Arsenic Oxidation Process : Case study - Skovby Waterworks, Denmark
Tran, Lam (2017)
Kaakkois-Suomen ammattikorkeakoulu
2017
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2017083114679
https://urn.fi/URN:NBN:fi:amk-2017083114679
Tiivistelmä
Arsenic contamination has been a pressing concern in water supplies for a long time, exerting detrimental and severe impacts on human health due to its high toxicity. According to Danish drinking water criteria, the limit for arsenic is set to 5 µg/l. Skovby waterworks, a local water supply company in Denmark, is planning to increase water production by abstracting raw water from a new intake well which contains 18 µg/l of arsenic.
The study aimed to find the most practical and appropriate treatment techniques to deal with high level of arsenic in the new boring raw water at Skovby waterworks. Investigating on the oxidizing potential of solid media was also one of the objectives of this study, providing knowledge about the roles of manganese oxides coated sand in arsenic oxidation process. A review of literature on existing arsenic removal methods as well as manganese oxides ‘s ability to convert As(III) to As(V) were carried out. Several calculations were made to identify possible water treatment operations and systems that could manage raw water containing arsenic from new well while satisfying with safety limit.
Manganese oxides has shown good capability of oxidizing As(III) to As(V) following first-order kinetic with a half-life time of 3-6 minutes, in which manganese oxides could either be a catalyst for reaction between arsenic and dissolved oxygen or a main oxidant in direct reaction with arsenic through surface mechanism. The role was defined by the levels of interfering substances in raw water, such as sulfide, iron or natural organic matter.
High efficiency of arsenic removal could be achieved by oxidation/filtration method (also known as iron and manganese removal), in which arsenic is co-removed with natural iron content in water. Three water treatment designs and processes were studied, of which co-treatment of raw water sources and two-step arsenic treatment indicated good results while individual treatment of raw water from new well was possible if iron chemical was added.
Later experiments and bench-scale studies are suggested to better accurate the efficiency of arsenic oxidation process and arsenic removal treatment.
The study aimed to find the most practical and appropriate treatment techniques to deal with high level of arsenic in the new boring raw water at Skovby waterworks. Investigating on the oxidizing potential of solid media was also one of the objectives of this study, providing knowledge about the roles of manganese oxides coated sand in arsenic oxidation process. A review of literature on existing arsenic removal methods as well as manganese oxides ‘s ability to convert As(III) to As(V) were carried out. Several calculations were made to identify possible water treatment operations and systems that could manage raw water containing arsenic from new well while satisfying with safety limit.
Manganese oxides has shown good capability of oxidizing As(III) to As(V) following first-order kinetic with a half-life time of 3-6 minutes, in which manganese oxides could either be a catalyst for reaction between arsenic and dissolved oxygen or a main oxidant in direct reaction with arsenic through surface mechanism. The role was defined by the levels of interfering substances in raw water, such as sulfide, iron or natural organic matter.
High efficiency of arsenic removal could be achieved by oxidation/filtration method (also known as iron and manganese removal), in which arsenic is co-removed with natural iron content in water. Three water treatment designs and processes were studied, of which co-treatment of raw water sources and two-step arsenic treatment indicated good results while individual treatment of raw water from new well was possible if iron chemical was added.
Later experiments and bench-scale studies are suggested to better accurate the efficiency of arsenic oxidation process and arsenic removal treatment.