Iron oxidation in different types of groundwater of Western Siberia

Abstract

Background, aim, and scope The groundwaters of Western Siberia contain high concentrations of iron, manganese, silicon, ammonium, and, in several cases, hydrogen sulfide, carbonic acids, and dissolved organic substances. Generally, the groundwaters of Western Siberia can be divided into two major types: one type with a relatively low concentration of humic substances and high hardness (water of A type) and a second type with a relatively low hardness and high concentration of humic substances (water of B type). For drinking water production, the waters of A type are mostly treated in the classical way by aeration followed by sand bed filtration. The waters of B type often show problems when treated for iron removal. A part of iron practically does not form the flocs or particles suitable for filtration or sedimentation. The aim of this work was to determine the oxidizability of Fe(II), to characterize the iron colloids, and to investigate the complexation of the iron ions with humic substances and the coagulation of the iron colloids in the presence of dissolved organic matter. Materials and methods Water samples of the A and B types were taken from bore holes in Western Siberia (A type: in Tomsk and Tomsk region, B type: in Beliy Yar and Kargasok). Depth of sampling was about 200 m below surface. The oxidation of the groundwater samples by air oxygen and ozone was done in a bubble reactor consisting of a glass cylinder with a gas-inlet tube. To produce ozone, a compact ozone generator developed by Tomsk Polytechnic University was used. For the characterization of the colloids in the water of B type, the particle size distribution and the zeta potential were measured. To investigate the formation of complexes between iron and humic substances in the water of B type, size exclusion chromatography was used. The coagulation behavior of iron in the presence of dissolved organic substances was investigated at different pH values. The agglomerates were detected by measuring the optical density using a UV-Vis spectrometer. Results Ozone showed, as expected, a faster oxidation of Fe (II) than air oxygen. The rate constants for Fe(II) oxidation were not much different for the waters of A and B types when the same oxidation process was used. However, the removal of iron after oxidation and filtration was higher in the water of A type than in the water of B type. No evidence for the formation of soluble complexes between iron and humic substances were found. In the water of A type, the coagulation process started at pH=4.5 and accelerated with increasing pH value. In the water of B type, the coagulation of colloids occurred only at pH=11 and higher. Discussion The oxidation experiments indicated no major effect of dissolved organic carbon concentration on the kinetics of Fe(II) oxidation. In contrast to this, the humic substances showed a significant influence on the aggregation behavior of the iron hydroxide colloids. Due to the sorption of humic substances on the iron hydroxide colloids, they were highly stable in the pH ...

Colloid stability of iron compounds in groundwater of Western Siberia

“…As shown earlier (Serikov et al 2009 ), stable iron colloid substances are formed in waters with a low hardness salt concentration. The groundwater hardness depends more on calcium salt than on magnesium salt (Serikov et al 2009 ). Moreover, no aluminum ions are found in groundwater where iron colloid substances are formed.…”

“…The groundwater hardness depends more on calcium salt than on magnesium salt (Serikov et al 2009). Moreover, no aluminum ions are found in groundwater where iron colloid substances are formed.…”

“…During oxidation, slightly soluble iron hydroxide (III) appears in the colloid form; the properties of this colloid are well studied (Richard 2004 ; Paul and Raj 1997 ). Second, these are humic organic substances which assist the formation of stable iron-containing colloid systems (Serikov et al 2009 ). Third, there are silicon compounds which can also contribute to the formation of colloid compounds both with iron compounds and with organic substances (Crittenden et al 2012 ).…”

Rapid Removal and Separation of Iron(II) and Manganese(II) from Micropolluted Water Using Magnetic Graphene Oxide

“…Figure a illustrates the variation in the adsorption capacity trends versus contact time for micropolluted water. The adsorption equilibrium for both Fe and Mn was achieved within 1.0 min, which was very rapid compared with aeration and oxidation treatment that usually takes hours . Even for synthetic water with high metal concentrations, adsorption equilibrium was reached in 15 min (Supporting Information Figure S6).…”

Условия Совместного Удаления Соединений Кремния И Гуминовых Веществ Из Природных Вод В Присутствии Продуктов Термической Обработки Магнезита

“…Подземные воды Западной Сибири характери зуются содержанием ионов железа, силикат ионов и органических веществ гумусового происхожде ния. Соединения железа и кремния попадают в во ду в результате растворения минералов [1], а забо лоченность территории способствует обогащению подземных вод гуминовыми веществами. Содер жание силикат ионов в подземных водах варьиру ется от 10 до 30 мг/л, при нормативном значении 10,0 мг/л [2].…”