Abstract
Although they are abundantly available, the specific applicability of water treatment residues (WTRs) is dictated largely by the favorability of physicochemical characteristic properties and mineralogical composition. We have suggested that WTRs have a high potential for remediation application. In addition, the relevant properties that define the beneficial reuse of WTRs may be widely variable due to the influence of the dose, type of coagulant/softening agent, and quality of source water. This study investigated the physical, chemical, agronomic, and mineralogical characteristics of three different types of WTRs that were collected from treatment plants in the Midwestern U.S, in order to compare and assess their suitability for remediating impacted ecosystems, such as abandoned mine lands (AML). An analysis of the results showed that the differences in the properties of the WTR samples were significant. The total metal concentrations by inductively coupled plasma mass spectrometry (ICP-MS) revealed the abundance of Fe, Al, Mn, Cu, and other co-occurring metals. The leachability of metal(loid)s, regulated under the Resource Conservation and Recovery Act (RCRA 8 metals), were below their respective US Environmental Protection Agency (EPA) allowable limits of 5.0, 100, 1.0, 5.0, 5.0, 0.2, 1.0, and 5.0 mg/kg, indicating that the WTRs were non-hazardous to the environment. Comparatively, the Al-WTR showed a significant release of arsenic (As), possibly from livestock waste and pesticide application from farms in the catchment area of the raw water source. The WTRs were alkaline (potential of hydrogen [pH] 7.00–9.10), which suggested a high acidity-neutralizing potential. The Ca:Mg ratio was between 1:7 and 1:1.5 (meq basis), which contributed to a cation exchange capacity (CEC) range of 4.6–16.2 meg/100g. The WTRs also showed adequate capability to supply relevant plant nutrients, such as Zn, Ca, Mg, S, Cu, and Fe, although readily available concentrations of NO3-N, P, and K were generally low. Thus, the alkalinity, significant CEC, low metal concentration and the presence of X-ray diffraction amorphous phases and calcites suggested that WTRs could be safely applied as low-cost sustainable alternatives for soil improvement and remediating contaminants such as metal(loid)s in AML.
Highlights
The treatment processes that are utilized in the production of potable water include coagulation–filtration, granular activated carbon, precipitative softening, ion exchange, and membrane separation
This study has suggested that water treatment residuals (WTRs) have a high potential for remediation application due to particular inherent properties and that, WTRs may share common properties, a composition analysis of samples that were collected from different treatment facilities, would reveal significantly different levels of the relevant parameters that define beneficial reuse
WTRs samples were, collected from three drinking water treatment plants in the Southern Illinois region, in order to explore their potential for remediation application
Summary
The treatment processes that are utilized in the production of potable water include coagulation–filtration, granular activated carbon, precipitative softening, ion exchange, and membrane separation. Precipitative softening plants primarily reduce hardness by raising the potential of hydrogen (pH) in order to enhance the precipitation of calcium carbonate (CaCO3) and magnesium hydroxide Mg(OH), using lime or soda ash These treatment processes result in the production of byproducts known as water treatment residuals (WTRs) [2]. The sustainable recycle and reuse of WTRs as a cost-effective and efficient alternative material for remediation of soil and water at identified abandoned mines sites It would provide a safe and beneficial disposal route for the otherwise solid waste, as regulated under the framework of the Resource Conservation and Recovery Act (RCRA) public law. WTRs samples were, collected from three drinking water treatment plants in the Southern Illinois region, in order to explore their potential for remediation application. The identification of mineral phases was conducted by comparing calculated d-spacing values with published crystal structure data [38]
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