Study on the Factors Affecting the Start-Up of Iron-Manganese Co-Oxide Filters for Ammonium and Manganese Removal from Groundwater

The removal of ammonia, arsenic, iron and manganese by biological treatment from a small Iowa drinking water system

Although not regulated in United States drinking water, ammonia has the potential to increase chlorine consumption and cause nitrification problems in the distribution system. Many groundwaters with elevated ammonia are also contaminated with other inorganic analytes such as arsenic, iron, and manganese, all of which have primary or secondary maximum contaminant levels (MCLs). The objective of this work was to demonstrate the effectiveness of an innovative biological treatment process to simultaneously remove ammonia (2.9 mg N per L), arsenic (23 μg L^-1), iron (2.9 mg L^-1) and manganese (80 μg L^-1) from a groundwater source in Iowa. The biological treatment system consisted of an "aeration contactor" followed by a conventional granular media filter. Orthophosphate was also added, as a biological nutrient, at 0.3 mg PO₄ per L. Ammonia, manganese, and iron were consistently reduced through the pilot system by 98 to 99%. Complete oxidation of ammonia to nitrate was observed (i.e., no nitrite was released) and arsenic was consistently removed to below the 10 μg L^-1 MCL. Ammonia was oxidized by ammonia and nitrite oxidizing bacteria and arsenic by bacteria which converted As(III) in the source water to more readily removable As(V). Iron was presumably oxidized by oxygen during aeration although some biologically assisted oxidation could not be ruled out. As(V) bound iron particles were removed in the filter resulting in effective arsenic (and iron) reduction. A surprising treatment benefit was the effective manganese reduction, the mechanism of which was not so clear, but was attributed to biologically assisted oxidation of Mn(II). While some system acclimation time was necessary to achieve desired ammonia and manganese reductions, acceptable arsenic and iron reductions were observed shortly after start-up.

The mixotrophic denitrification characteristics of Zoogloea sp. L2 accelerated by the redox mediator of 2-hydroxy-1,4-naphthoquinone

Denitrification in mixed culture system has been extensively researched to date, but few studies have focused on accelerating the process using redox mediators to promote electron transfer. Strain L2, an iron-reducing bacteria, can remove 75.44% of nitrate under temperature of 30.60 °C, pH of 6.75 and Fe²⁺ concentration of 27.86 mg·L^-1. Additionally, the removal rate of nitrate reached 1.516 mg·L^-1·h^-1 in 8 h with the addition of 0.030 mmol·L^-1 2-hydroxy-1,4-naphthoquinone (HNQ), which increased by 1.38 times than control group. Furthermore, analysis by fluorescence spectroscopy, flow cytometer and gas chromatography demonstrated that HNQ positively stimulated denitrification. This study provides a reference for enhancing denitrification in mixed culture and lays the foundation for the practical application of redox mediators in groundwater treatment.

Mineral Materials Coated with and Consisting of MnOx-Characteristics and Application of Filter Media for Groundwater Treatment: A Review

For groundwater treatment, the technologies involving oxidation on MnOx filter bed are beneficial, common, and effectively used. The presence of MnOx is the mutual feature of filter media, both MnOx-coated mineral materials like quartz sand and gravel, chalcedonite, diatomite, glauconite, zeolite, or anthracite along with consisting of MnOx manganese ores. This review is based on the analysis of research and review papers, commercial data sheets, and standards. The paper aimed to provide new suggestions and useful information for further investigation of MnOx filter media for groundwater treatment. The presented compilations are based on the characteristics of coatings, methods, and conditions of its obtaining and type of filter media. The relationship between the properties of MnOx amendments and the obtained purification effects as well as the commonly used commercial products, their features, and applications have been discussed. The paper concludes by mentioning about improving catalytic/adsorption properties of non-reactive siliceous media opposed to ion-exchange minerals and about possible significance of birnessite type manganese oxide for water treatment. Research needs related to the assessment of the use MnOx filter media to heavy metals removal from groundwater in field operations and to standardize methodology of testing MnOx filter media for water treatment were identified.