Coated Filter Media Research Articles

Effects of various humid environments on the filtration and dust cleaning performance of filter media

The filtration technology is gaining popularity in underground projects which are characterized by a poor working environment. However, the influence of various humid environments on the filtration performance of filter media (FM) has not been clarified yet. This study is the influence of humid environments on the performances of common mechanical filter media (MFM) and polytetrafluoroethylene coated filter media (CFM). First, the methods to control the dust moisture content, relative humidity and spray rate were determined. Then, the influences of dust loading on the pressure drop, filtration velocity and dust cleaning performance in various humid environments were explored. The results indicate that the maximum pressure drops of MFM and CFM both grow first and then decline with the increase in dust moisture content. The different is that the maximum pressure drops of MFM and CFM both decrease with the rise of relative humidity. In addition, the maximum pressure drops of MFM and CFM both decline first and then rise with the acceleration of the spray. Under the same humid environment, MFM correspond to a larger maximum value and a greater variation of pressure drop than CFM. When the dust moisture content, relative humidity or spray rate increases, the residual pressure drops of both FM grow after dust cleaning, but the latter corresponds to a smaller growth.

Interference of manganese removal by biologically-mediated reductive release of manganese from MnOx(s) coated filtration media

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 MnOx(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 MnOx(s) coatings. In situ vial assays were developed to gain insight into the impacts of MnOx(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 microbially-mediated Mn release was possible above a threshold equivalent of 2 × 102S. oneidensis MR-1 CFU per gram of MnOx(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, MnOx(s) age appeared to play a role in Mn reduction and subsequent release, where MnOx(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.

Influence of pleat geometry on the filtration and cleaning characteristics of filter media

Abstract The aim of this study is to analyze the influence of pleat geometry on the filtration and cleaning characteristics of the filter media through experiment. Six kinds of test chambers were designed to study the conventional filter media and the coated filter media with varying pleat ratio (the ratio of pleat height to pleat pitch). The experimental results showed that pleat geometry significantly influenced the pressure drop and the cleaning adhesive force in the two kinds of filter media. The effect of pleat geometry on the parameters of the dust cake was also studied in this work. The regeneration efficiency of conventional and coated filter media all gradually decreased with increasing pleat ratio, and the latter was higher than the former. The analysis of the experimental data and the theoretical equations revealed that the effective filtration area was mainly influenced by the pleat ratio and the pleat ratio should be kept to be below 1.59. The relationship between the effective filtration area and the pleat ratio for the conventional and coated filter media can be described by mathematical models.

Properties of catalyst for iron and manganese oxidation in filter materials

The aim of this work is to determine the properties of contact layers of grain of different type of filter media in term of their suitability for catalytical manganese oxidation and auto-activation for manganese removal from groundwater. The following oxidative filtration materials were investigated: auto-activated silica sand taken from full-scale filters (oxide coated filter media), Pyrolox – manganese ore – natural material and Hydrolit – artificially activated material. As a reference two natural not chemically active materials were tested: clean silica sand and clean chalcedonite. The investigation resulted in chemical composition and microstructure parameters of catalyst contact layers of grains. The modern analytical methods were used: EDAX, Raman spectroscopy, mercury and helium porozymetry. The data indicated that catalyst from autoacivated filtration material has better chemical composition and porosity parameters in comparison to tested catalytic filtration materials, making it more suitable for adsorption and catalytic manganese oxidation.

Evaluating the role of soluble aluminum in manganese removal via MnOx(s)-coated filtration media in drinking water treatment

The Mn oxide (MnOx(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 MnOx(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 MnOx(s)-coated media. The experimental results confirmed that soluble Al was removed in significant amounts by adsorption onto the MnOx(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, MnOx(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 MnOx(s) coatings on these media.

Low-temperature effects on the removal of soluble manganese in MnOx(s)-coated media systems

The purpose of this study was to investigate the role of low-temperature conditions in potentially impacting soluble Mn2+ removal in MnOx(s)-coated media systems. The study involved an extensive examination of water quality and process data for a ten-year period (2005–2014) from the Harwood's Mill Water Treatment Plant in Newport News, VA. Additionally, laboratory-scale shallow depth column studies were performed employing MnOx(s)-coated media for soluble Mn2+ removal. Data were evaluated for the impacts of low temperature conditions, water pH, soluble Mn2+ concentration, and free chlorine concentration on the ability of MnOx(s)-coated media to promote effective soluble Mn2+ removal. The results show that the uptake of soluble Mn2+ onto MnOx(s)-coated filter media is significantly impacted by water temperatures below 15 °C, with impacts being very substantial under lower temperature (T < 10 °C) conditions. Also, the adverse effects of low temperature on MnOx(s)-coated treatment processes can be at least partially mitigated by an increase in solution pH.

Assessment of Fate of Manganese in Oxide-Coated Filtration Systems

This study employed pilot-scale filters to examine the fate of Mn in MnOx(s)-coated filter media as a function of filter-applied pH and backwash conditions. A key operational issue for continuous efficient Mn(II) removal was maintenance of appropriate levels of free chlorine to ensure coated media regeneration. Neutral or slightly acidic pH promoted Mn(II) sorption and subsequent oxidation on MnOx(s)-coated media. Alkaline influent pH (pH > 7) allowed some soluble Mn(II) oxidation by free chlorine prior to filtration, resulting in significant Mn removal by MnOx(s) particle filtration. Increased backwash rates removed greater amounts of MnOx(s) from the filter media. The combination of MnOx(s) accumulation on filter media during filtration and its partial removal during backwash maintained a net amount of MnOx(s) coating sufficient for catalyzing further soluble Mn(II) removal, yet it did not significantly alter the size of the media.

Removal of Soluble Manganese by Oxide‐coated Filter Media: Sorption Rate and Removal Mechanism Issues

Research was conducted to provide a better understanding of the mechanisms of Mn(II) removal in oxide‐coated filters. The kinetics of Mn(II) sorption by MnOx(s)‐coated filter media were quantified as a function of solution pH, MnOx(s) surface concentration, and free chlorine concentration of the filter‐applied water. Rate of Mn(II) sorption was positively correlated to the number of available surface adsorption sites within a filter. Free chlorine had a very significant role in defining both the rate and ultimate extent of Mn(II) removal. Addition of chlorine to the filter‐applied water oxidized the adsorbed Mn(II), thereby continually regenerating the media surface. In the absence of free chlorine, Mn(II) removal was by adsorption only; no evidence of auto‐oxidation of Mn(II) was noted. Practical applications of the work to the operation of water treatment facilities concern the selection of oxidant dosing locations, the impact on filtration hydraulics, and the determination of media generation requirements.