DoD-SERDP Project. Drinking Water Treatment Residuals as Material for in-situ Capping of Metal Contaminated Sediments

DoD-SERDP Project. Drinking Water Treatment Residuals as Material for in-situ Capping of Metal Contaminated Sediments

 

SUMMARY OF THE MAIN FINDINGS

Proposal Number:  ER18-C4-1428

Proposal Title: Drinking Water Treatment Residuals (DWTR) as Material for in situ Capping of Metal-Contaminated Sediments

Principal Investigators

Jean-Claude J. Bonzongo*, Nancy D. Denslow**, and Jean-François Gaillard***

*Dept. of Environmental Engineering Sciences, University of Florida, Gainesville, FL 32611-6450, USA

**Dept. of Physiological Sciences & Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32611, USA

***Dept. of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208-3109, USA

Video summary: https://youtu.be/Qp5oOTtJ73g

 

Drinking water treatment residuals (DWTRs) produced as result of the coagulation-flocculation process during water treatment are highly heterogeneous substrates containing several chemical functional groups that can act as binding sites for dissolved metals. To add value to these byproducts of drinking water treatment processes, numerous studies have focused on the determination of their ability to sequester metals and other anionic and cationic chemicals from contaminated aqueous effluents. In this project, we investigated the possibility of using DWTRs as in situ active capping substrates for metal-contaminated sediments. Laboratory studies were conducted to determine the physicochemical and toxicological characteristics of DWTRs with the goal of developing a screening procedure for the identification of DWTRs that can be considered safe for introduction to U.S. waters. The characterization component involved chemical analyses (total metal concentrations), ecotoxicological bioassays (toxicity to freshwater and marine organisms), and a combination of solid phase analytical techniques to gain insights into the association of metals with the different geochemical fractions of DWTRs. The ability of these substrates to immobilize dissolved metals was investigated using batch and flow-through column studies. Gust chamber studies were conducted using metal-contaminated sediment cores to determine (1) the ability of DWTR to reduce or eliminate the upward flux of metals from contaminated sediments to the overlying water, and (2) reduce/eliminate metal toxicity to water column organisms using fathead minnow juveniles in 96h exposure studies. Finally, diffusive gradients in thin films (DGT) were used to probe the effects of capping metal-contaminated sediments with DWTR on metal concentrations in both pore and overlying waters. The main findings of this research program can be summarized as follows:

  • Differences in the chemical composition of both treated waters and additives used in the water treatment processes do lead to highly heterogeneous DWTRs, and based on State and federal regulations, not all these substrates will be adequate for introduction to U.S. waters. Although none of the 15 samples tested in this study failed the toxicity characteristics leaching procedure (TCLP) test (i.e., all were non-hazardous), 6 samples (40%) were found non-adequate based on metal contents and sediment quality guidelines (SQG). Only 3 of the 9 that were classified as acceptable or questionable based on SQG results were qualified further using elutriation and ecotoxicity studies. The results led to the development of a screening method for selection of potentially safe DWTRs for use as capping substrate for metal-contaminated sediments.
  • Batch studies on the determination of the ability of DWTRs to sequester and immobilize metals from aqueous effluents showed that the affinity of metal cations for these substrates is significantly higher for borderline and type-B metals than for type-A metals. We also investigated the mechanisms of the association of metals with the different geochemical fractions of DWTRs. For instance, Hg sorption by DWTRs is due primarily to two atoms in the first shell and would be bound to oxygen (O) when attached to an aluminum oxide such as kaolinite, and to sulfur (S) when associated with sulfhydryl groups present in organic matter. Some of the tested DWTRs showed well-defined second shell features due to the presence of light elements such as N and O, with potential implications on sorption processes.
  • The results of the fixed bed column studies showed that DWTRs were able to significantly delay the breakthrough of metals when compared to an inert substrate (sand). Fitting of the experimental data with an adsorption model suggested that adsorption was not the only mechanism of metal immobilization, especially in aqueous solutions containing dissolved organic carbon. Precipitation seemed to play an important role, likely due to the presence of high levels of carbonates in some of the DWTRs.
  • The use of metal-contaminated sediment cores in gust chambers submitted to increasing hydrologic shear stress levels ranging from zero to 0.4 Pa, showed that sediment capping with DWTR does reduce both sediment erosion and the upward flux of metals from sediments to the overlying water. The reduction of the upward fluxes of metals due to both physical and chemical processes was significant for sediments containing high water-extractable and easily exchangeable metal fractions. Results show that the use of DWTR as a sediment capping layer can reduce the metal contamination of the overlying water by up to 95% as compared to the non-capped sediments.
  • Fish exposure studies using waters equilibrated with metal-contaminated sediments in either the absence (control) or presence (treatment) of a cap layer made of either sand or DWTR showed the ability of DWTR to reduce/eliminate toxicity to pelagic organisms.
  • The use of passive porewater samplers (DGT) showed that the presence of DWTR as capping layer at the water-sediment interface impacted the vertical profiles of soluble metal concentrations in both the overlying and pore waters by reducing the total dissolved metal concentrations through adsorption and precipitation processes.

Overall, the data collected so far suggest that the capping of metal-contaminated sediments with DWTR can be useful under specific scenarios, namely when sediments contain large fractions of water leachable and easily exchangeable metals. However, the small size of samples investigated in this study did not allow the development of a robust predictive tool linking the physicochemical characteristics of DWTRs to sought performances.

 

DISSEMINATION OF THE RESULTS

Community meeting. We organized a virtual “community meeting” on 3/09/2023. The topic of the meeting was “Evaluation of Drinking Water Treatment Residuals as Substrate for in situ Capping of Metal-Contaminated Sediments”. For this meeting we targeted the DWTP managers, primarily those who supplied us with the DWTR samples used in the study, as well as researchers from different academic institutions, working on the remediation of contaminated soils and sediments. The meeting was well attended. Unfortunately, the Zoom link for this meeting has now expired. 

High quality video summary. A high-quality video summarizing this research was produced and can be seen at: https://youtu.be/Qp5oOTtJ73g 

Publication List

Wallace, S. M., Zhou, L., Ma, Q., Denslow, N. D., Bonzongo, J. C. J., & Gaillard, J. F. (2024). An XAS study of Hg (II) sorption to Al-based drinking water treatment residuals. Chemosphere, 349, 140922.

Wallace, SM., Zhang Y, Zhou L, Ma Q, Guise WE, Denslow ND, Bonzongo JC, and Gaillard JF. (2023). The diversity of aluminum-based drinking water treatment residuals for use in environmental remediation. Environmental Science: Water Research & Technology, 9(3), 935-947.

Quiñones, KYD., & Bonzongo, JC. (2023). Effects of simulated acid rain and carbon rich water on mercury mobilization in soils amended with aluminum-based drinking water treatment residuals. Soil & Environmental Health, 100020.

Zhou, L., Wallace, SM., Denslow, ND., Gaillard, JF., Meyer, P., & Bonzongo, JC. (2021). A screening approach for the selection of drinking water treatment residuals for their introduction to marine systems. Environmental Toxicology and Chemistry, 40(4), 1194-1203.

Zhou, L., Wallace, SM., Kroll, KJ., Denslow, ND., Gaillard, JF., Meyer, P., & Bonzongo, JC. (2021). Acute and chronic toxicity testing of drinking water treatment residuals in freshwater systems. Environmental Toxicology and Chemistry, 40(7), 2003-2012.

Wallace SM, Zhou L, Gaillard JF, Denslow ND, & Bonzongo JC (2021). Probing Cu sorption to drinking water treatment residuals (DWTRs) by XAS. American Chemical Society Spring meeting, April 2021.

Zhou L, Wallace SM, Denslow ND, Gaillard JF, & Bonzongo JC (2021). Total and leachable concentrations of toxic metals in drinking water treatment residuals (DWTRs) and toxicity implications in marine and freshwater systems. American Chemical Society Spring meeting, April 2021.

Bonzongo JC, Gaillard JF and Denslow ND. 2021. Evaluation of Drinking Water Treatment Residuals for Use as Capping Sorbent in Metal Contaminated Sediments. SERDP & ESTCP Annual Symposium. Washington, DC, 11/2022.

Zhou L., Wallace SM, Chen T, Kevin KJ, Denslow ND, Gaillard, JF. and Bonzongo, JC. 2019: Evaluation of Drinking Water Treatment Residuals for Use as Capping Sorbent in Metal Contaminated Sediments. SERDP & ESTCP Annual Symposium. Washington, DC, 12/2019.

Bonzongo, JC, Gaillard, JF, Denslow Nd, Zhou L, Wallace SM, Gendusa W, & Kroll KJ. (2018). Drinking Water Treatment Residuals as Material for in situ Capping of Metal-Contaminated Sediments. SERDP & ESTCP Symposium Sediment Meeting. Washington, DC, 11/2018.

Wallace, S. M., Zhou, L., Gaillard, J. F., Kroll, K., Denslow, N. D., & Bonzongo, J. C. (2021, November 29-December 3). Drinking Water Treatment Residuals (DWTRs) as Material for in situ Capping of Metal-Contaminated Sediments: Metal Sorption Studies. Virtual Poser Session, SERDP-ESTCP Symposium.

Zhou, L., Wallace, S. M., Denslow, N. D., Gaillard, J. F., & Bonzongo, J. C. (2021, April 5-16). Total and Leachable Concentrations of Toxic Metals in Drinking Water Treatment Residuals (DWTRs) and Toxicity Implications in Marine and Freshwater Systems. Virtual Poster session, American Chemical Society Spring 2021.

Zhou, L., Wallace, S. M., Chen, T., Zhang, Y., Kroll, K., Denslow, N. D., Gaillard, J. F., & Bonzongo, J. C. (2019, December 3-5). Evaluation of Drinking Water Treatment Residuals for Use as Capping Sorbent in Metal Contaminated Sediments. Poster session, SERDP- ESTCP Symposium, Washington, D.C.

Bonzongo, J. C., Gaillard, J. F., Denslow, N. D., Hill, A., Wallace, S. M., Chen, T., Zhou, L., Gendusa, W., & Kroll, K. (2018, November 27-29). Can drinking water treatment residuals be used as material for in-situ capping of metal contaminated sediments? Poster session, SERDP-ESTCP Symposium, Washington, D.C.

Manuscripts in preparation

Oyamada GK, Kroll K, Zhou L, Wallace SM, Bonzongo J-C, Gaillard J-F, and Denslow ND. (2024). Drinking water treatment residuals minimize the effect of metals on fish exposed to metal contaminated sediments. In prep.

Zhou L, Zheng Y, Wallace SM, Denslow ND, Gaillard J-F, and Bonzongo J-C. (2024). Predicting the sorption affinity of metals for drinking water treatment residuals of different chemical compositions based on the environmental classification of metals.  In prep.

Wei J, Zheng Y, Zhou L, Wallace SM, Denslow ND, Gaillard J-F, and Bonzongo J-C. (2024). Assessing the effectiveness of drinking water treatment residuals as in-situ capping substrates for metal-contaminated sediments.  In prep.

Wallace, S. M., Alsina M.A., Shindel B., Zhou, L., Ma, Q., Denslow, N. D., Bonzongo, J. C., and Gaillard, J. F. (2024). A spectroscopic examination of copper and lead sorption to aluminum-based drinking water treatment residuals. (In prep)