Low-temperature effects on the removal of soluble manganese in MnOx(s)-coated media systems (original) (raw)
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Water Research, 2017
The Mn oxide (MnO x(s)) surfaces of water treatment filtration media are known to aid in the capture of dissolved Mn species, but the discovery of significant deposits of Al within these coatings (Tobiason et al., 2008) raised certain questions about the possible role of Al in soluble Mn removal and the formation of the MnO x(s) surface on the media. This phenomenon was addressed by conducting a series of bench-scale column studies that involved the application of solutions containing varying amounts of soluble Al and Mn to MnO x (s)-coated media. The experimental results confirmed that soluble Al was removed in significant amounts by adsorption onto the MnO x(s) media surface. The deposition of soluble Al onto the media surface did not have any significant effect on its ability to remove soluble Mn. Likewise, the relative amounts of Al incorporated into the media coating suggested that uptake of soluble Al alone cannot fully explain the levels of Al often found in real-world, MnO x (s)-coated filter media; instead, the incorporation of particulate forms of Al (routinely found in water treatment plant situations) must contribute to the formation of the MnO x (s) coatings on these media.
Water Research X, 2018
Discontinuing application of pre-filter chlorine is a common water treatment plant practice to permit a bioactive filtration process for the removal of soluble Mn. However, soluble Mn desorption has sometimes been observed following cessation of chlorine addition, where filter effluent Mn concentration exceeds the influent Mn concentration. In this paper it is hypothesized that Mn-reducing bacteria present in a biofilm on the filter media may be a factor in this Mn-release phenomenon. The primary objective of this research was to assess the role of Mn-reducing microorganisms in the release of soluble Mn from MnO x(s)-coated filter media following interruption of pre-filtration chlorination. Bench-scale filter column studies were inoculated with Shewanella oneidensis MR-1 to investigate the impacts of a known Mn-reducing bacterium on release of soluble Mn from MnO x(s) coatings. In situ vial assays were developed to gain insight into the impacts of MnO x(s) age on bioavailability to Mn-reducing microorganisms and a quantitative polymerase chain reaction (qPCR) method was developed to quantify gene copies of the mtrB gene, which is involved in Mn-reduction. Results demonstrated that microbiallymediated Mn release was possible above a threshold equivalent of 2 Â 10 2 S. oneidensis MR-1 CFU per gram of MnO x(s) coated media and that those organisms contributed to Mn desorption and release. Further, detectable mtrB gene copies were associated with observed Mn desorption. Lastly, MnO x(s) age appeared to play a role in Mn reduction and subsequent release, where MnO x(s) solids of greater age indicated lower bioavailability. These findings can help inform means of preventing soluble Mn release from drinking water treatment plant filters.
X-ray photoelectron spectroscopy (XPS) was applied to investigate Mn(II) removal by MnO x (s)-coated media under experimental conditions similar to the engineered environment of drinking water treatment plants in the absence and presence of chlorine. Macroscopic and spectroscopic results suggest that Mn(II) removal at pH 6.3 and pH 7.2 in the absence of chlorine was mainly due to adsorption onto the MnO x (s) surface coating, while removal in the presence of chlorine was due to a combination of initial surface adsorption followed by subsequent surface-catalyzed oxidation. However, Mn(III) was identified by XPS analyses of the Mn 3p photoline for experiments performed in the absence of chlorine at pH 6.3 and pH 7.2, suggesting that surface-catalyzed Mn oxidation also occurred at these conditions. Results obtained at pH 8.2 at 8 and 0.5 mg 3 L À1 dissolved oxygen in the absence of chlorine suggest that Mn(II) removal was mainly due to initial adsorption followed by surface-catalyzed oxidation. XPS analyses suggest that Mn(IV) was the predominant species in experiments operated in the presence of chlorine. This study confirms that the use of chlorine combined with the catalytic action of MnO x (s) oxides is effective for Mn(II) removal from drinking water filtration systems.
Mn(II) Dissolution from the Surface of Manganese Oxide-Coated Filter Media
Manganese oxides on the surface of filter media adsorb soluble manganese and organic matter in the water. Previous studies have suggested that surface coated manganese removes soluble manganese by adsorption and subsequent oxidation in the presence of oxidants at neutral pH's. However, the adsorbed Mn(II) and surface coated manganese oxide coatings can be dissolved from the surface of filter media under anoxic conditions and/or acidic conditions in the presence of adsorbed organics on the surface of the filter media. The first objective of this investigation was to determine what conditions might lead to dissolution of adsorbed Mn(II) and Mn02(s) from the surface of manganese-coated filter media. The second objective was to develop a better understanding of manganese dissolution by organics and solution pH in the absence and presence of free chlorine. The third objective was to recommend procedures to control the release of manganese from the filter media. Experiments were perfo...
Water Research, 2014
Manganese-oxidizing bacteria a b s t r a c t Soluble manganese (Mn) presents a significant treatment challenge to many water utilities, causing aesthetic and operational concerns. While application of free chlorine to oxidize Mn prior to filtration can be effective, this is not feasible for surface water treatment plants using ozonation followed by biofiltration because it inhibits biological removal of organics.
Manganese removal processes at 10 groundwater fed full-scale drinking water treatment plants
Water Quality Research Journal, 2019
Manganese (Mn) removal in drinking water filters is facilitated by biological and physico-chemical processes. However, there is limited information about the dominant processes for Mn removal in full-scale matured filters with different filter materials over filter depth. Water and filter material samples were collected from 10 full-scale drinking water treatment plants (DWTPs) to characterise the Mn removal processes, to evaluate the potential use of enhancers and to gain further insight on operational conditions of matured filters for the efficient Mn removal. The first-order Mn removal constant at the DWTPs varied from 10−2 to 10−1 min−1. The amount of Mn coating on the filter material grains showed a strong correlation with the amount of iron, calcium and total coating, but no correlation with the concentration of ATP. Inhibition of biological activity showed that Mn removal in matured filters was dominated by physico-chemical processes (59–97%). Addition of phosphorus and trace...
Significance of MnO2 Type and Solution Parameters in Manganese Removal from Water Solution
International Journal of Molecular Sciences
A very low concentration of manganese (Mn) in water is a critical issue for municipal and industrial water supply systems. Mn removal technology is based on the use of manganese oxides (MnOx), especially manganese dioxide (MnO2) polymorphs, under different conditions of pH and ionic strength (water salinity). The statistical significance of the impact of polymorph type (akhtenskite ε-MnO2, birnessite δ-MnO2, cryptomelane α-MnO2 and pyrolusite β-MnO2), pH (2–9) and ionic strength (1–50 mmol/L) of solution on the adsorption level of Mn was investigated. The analysis of variance and the non-parametric Kruskal–Wallis H test were applied. Before and after Mn adsorption, the tested polymorphs were characterized using X-ray diffraction, scanning electron microscope techniques and gas porosimetry analysis. Here we demonstrated the significant differences in adsorption level between MnO2 polymorphs’ type and pH; however, the statistical analysis proves that the type of MnO2 has a four times ...
The Application of MnO2 in the Removal of Manganese from Acid Mine Water
Water, Air, & Soil Pollution, 2013
In recent years, much attention has been devoted in developing inexpensive or alternative systems for treating acid mine drainage (AMD). Manganese is a common component of AMD, and it is traditionally removed by precipitation. However, in order to meet the standard limits for discharging, usually <1 mg L −1 , it is necessary to raise the pH above 10 which implies in high consumption of reagents and a final pH that does not meet the required value for discharging. This study investigated the removal of manganese from an acid mine effluent and laboratory solutions by using an industrial residue consisted of manganese dioxide (MnO 2). The pH of the acid effluent is around 2.7, and the manganese concentration is approximately 140 mg L −1. Batch experiments assessed the influence of pH and the efficiency of manganese dioxide (MnO 2) in the Mn +2 removal. In the presence of MnO 2 , the metal concentration meets the discharging limit at pH range of 6.8 to 7.2. Experiments carried out with columns packed with MnO 2 assessed the influence of the flow rate on the process. Best results were obtained for columns fed with mine water neutralized with limestone at pH 7.0 and a residence time of 3.3 h. The maximum manganese loading capacity for MnO 2 was around 14 mg g −1. RAMAN spectroscopy showed that the MnO 2 is essentially constituted of pyrolusite. In addition, the solid hausmannite (Mn 3 O 4) was observed on the surface of the MnO 2 residue after its contact with the Mn +2 solution.
Removal of Mn2+ from water by “aged” biofilter media: The role of catalytic oxides layers
Journal of Bioscience and Bioengineering, 2009
The present work was aimed at evaluating the surface coatings characteristics and autocatalytic manganese oxidation potentials of two groups of "aged" biofilter media. This refers to the anthracite filter media of a biological water treatment plant on which metal oxides and a biofilm have deposited on the surface of the filter media over long time of filtration. Duplicate samples of anthracite filter media were collected from each of the six filter wells in the plant and classified into two groups, based on their duration of operation, as 3-years filter media and 15-years filter media. Batch experiments showed that the 15-years filter media exhibited very high manganese sorption capacity and were less dependent on the microbial activity than the 3-years filter media. Results of the surface coatings analyses indicated that the biofilter materials is predominantly composed of variable layers of manganese and iron oxides, with microbial biomass contributing only about 3.5 and 1.4% of the dry weight of the surface coatings on the 3-and 15-years filter media respectively. Investigations onto the Mn 2+ sorption by the lyophilized biofilter media showed that, the sorption kinetics on the catalytic oxides layers followed the pseudo-second-order kinetics model, thus suggesting chemisorption as the dominant mechanism of Mn 2+ removal. This implied that manganese removal by these biofilters is mainly by adsorption of Mn 2+ onto the iron and manganese (catalytic) oxides layers and autocatalytic oxidation. The present study has clearly linked Mn 2+ oxidation to the catalytic oxides layers on the aged biofilter media.