Characterization of Southern Illinois Water Treatment Residues for Sustainable Applications

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 NO 3 -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.