More Like this

1. Effects of residual disinfectants on the redox speciation of lead( ii )/( iv ) minerals in drinking water distribution systems

   https://doi.org/10.1039/d0ew00706d  

   Avasarala, Sumant ; Orta, John ; Schaefer, Michael ; Abernathy, Macon ; Ying, Samantha ; Liu, Haizhou ( February 2021 , Environmental Science: Water Research & Technology)

   null (Ed.)

   This study investigated the reaction kinetics on the oxidative transformation of lead( ii ) minerals by free chlorine (HOCl) and free bromine (HOBr) in drinking water distribution systems. According to chemical equilibrium predictions, lead( ii ) carbonate minerals, cerussite PbCO 3(s) and hydrocerussite Pb 3 (CO 3 ) 2 (OH) 2(s) , and lead( ii ) phosphate mineral, chloropyromorphite Pb 5 (PO 4 ) 3 Cl (s) are formed in drinking water distribution systems in the absence and presence of phosphate, respectively. X-ray absorption near edge spectroscopy (XANES) data showed that at pH 7 and a 10 mM alkalinity, the majority of cerussite and hydrocerussite was oxidized to lead( iv ) mineral PbO 2(s) within 120 minutes of reaction with chlorine (3 : 1 Cl 2  : Pb( ii ) molar ratio). In contrast, very little oxidation of chloropyromorphite occurred. Under similar conditions, oxidation of lead( ii ) carbonate and phosphate minerals by HOBr exhibited a reaction kinetics that was orders of magnitude faster than by HOCl. Their end oxidation products were identified as mainly plattnerite β-PbO 2(s) and trace amounts of scrutinyite α-PbO 2(s) based on X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopic analysis. A kinetic model was established based on the solid-phase experimental data. The model predicted that in real drinking water distribution systems, it takes 0.6–1.2 years to completely oxidize Pb( ii ) minerals in the surface layer of corrosion scales to PbO 2(s) by HOCl without phosphate, but only 0.1–0.2 years in the presence of bromide (Br − ) due the catalytic effects of HOBr generation. The model also predicts that the addition of phosphate will significantly inhibit Pb( ii ) mineral oxidation by HOCl, but only be modestly effective in the presence of Br − . This study provides insightful understanding on the effect of residual disinfectant on the oxidation of lead corrosion scales and strategies to prevent lead release from drinking water distribution systems. 

   more » « less
2. Impact of iron‐rich scale in service lines on lead release to water

   https://doi.org/10.1002/aws2.1188  

   Bae, Yeunook ; Pasteris, Jill D. ; Giammar, Daniel E. ( August 2020 , AWWA Water Science)

   Total iron and total lead concentrations were correlated in water that had stagnated in laboratory‐scale experiments with sections of 10 harvested lead service lines (LSLs) from Providence, Rhode Island. One of these sections had much greater lead release and pH decrease during stagnation, and the inner surface of this service line had a thick coating of iron oxide scale. The iron‐rich scale was composed of coarse‐grained iron oxides (lepidocrocite and magnetite) covered with a thin lead‐bearing layer (hydrocerussite). Complementary batch experiments with pure iron oxides found that their surfaces accelerated the oxidation of Pb(II) from hydrocerussite, which produced PbO_2(s)and decreased the pH. While the findings presented are for LSLs from Providence, the co‐occurrence of iron oxides and lead corrosion products is widespread. The results highlight the importance of considering iron corrosion when evaluating processes that control lead concentrations in tap water.

    

   more » « less
3. Phosphate-Based Corrosion Inhibition in Drinking Water Systems and Effects on Disinfectant Decay and Biofilm Growth

   https://doi.org/10.1089/ees.2023.0065  

   Huang, Conghui ; Ginn, Timothy R. ; Clark, Gemma G. ; Zaki, Farzana R. ; Won, Jungeun ; Boppart, Stephen A. ; Nguyen, Thanh H. ( October 2023 , Environmental Engineering Science)

   Catherine Peters (Ed.)

   Disinfectant decay by biofilms in distribution networks during stagnation can allow opportunistic pathogens' transmission and thus compromise drinking water safety. Applying phosphate-based corrosion inhibitors to the system can exacerbate disinfectant decay by providing nutrients to biofilms growing inside premise plumbings. In this study, we evaluate the impacts of corrosion inhibitors on biofilms' structural and chemical properties that form in premise plumbing, and the resulting implications for disinfectant decay. Two commonly used phosphate-based (phosphate blends and phosphate) corrosion inhibitors were added separately to simulated drinking water for biofilm development over 1 to 2 years. Optical coherence tomography (OCT) imaging showed that the studied biofilms' thickness, porosity, and porous structure did not change after exposure to free chlorine for 24 h or monochloramine for 120 h. Compared with groundwater biofilms, phosphate-based biofilms had the highest overall porosity due to their many connecting channels. The phosphate-based biofilms consumed free chlorine or monochloramine at a faster rate than groundwater biofilms. Experimental results showed that phosphate-based biofilms consumed more monochloramine after 96 h of contact than other biofilms. A separate set of experiments involving disinfectant decay with suspended biomass material, together with the OCT results, provided parameters for a simplified quasi-first-order reaction–diffusion model so that predictive modeling of decay in biofilms under stagnation conditions could be attempted without parameter fitting. The biofilm modeling results provided a close estimate for free chlorine decay while underestimating monochloramine decay. In agreement with the experimental results, the model results indicate that the phosphate-based biofilms led to slightly faster free chlorine consumption and monochloramine consumption than groundwater biofilms and indicate that diffusion limitation imposed by biofilm pore structure on disinfectant decay is important. The study results suggest that using phosphate-based corrosion inhibitors may lead to a rapid depletion of residual disinfectant during stagnation in the presence of biofilms. 

   more » « less
4. Bromide-assisted catalytic oxidation of lead( ii ) solids by chlorine in drinking water distribution systems

   https://doi.org/10.1039/C7CC02533E  

   Orta, John ; Patton, Samuel ; Liu, Haizhou ( January 2017 , Chemical Communications)

   This study investigated the effect of bromide on the oxidation of three lead( ii ) solids by chlorine – a redox process critical to the control of lead release in drinking water distribution systems. Bromide had a strong catalytic effect on the oxidation of lead( ii ) carbonate solids, but had a limited impact on the oxidation of lead( ii ) phosphate. 

   more » « less
5. Enhanced toxicity of environmentally transformed ZnO nanoparticles relative to Zn ions in the epibenthic amphipod Hyalella azteca

   https://doi.org/10.1039/C8EN00755A  

   Poynton, Helen C. ; Chen, Chun ; Alexander, Shaun L. ; Major, Kaley M. ; Blalock, Bonnie J. ; Unrine, Jason M. ( January 2019 , Environmental Science: Nano)

   After release into the aquatic environment, engineered nanomaterials (ENMs) undergo complex chemical and physical transformations that alter their environmental fate and toxicity to aquatic organisms. Hyalella azteca are sediment-dwelling amphipods predicted to have a high exposure level to ENMs and have previously shown to be highly sensitive to ZnO nanoparticles (NPs). To investigate the impacts of environmentally transformed ZnO NPs and determine the route of uptake for these particles, we exposed H. azteca to ZnSO 4 , ZnO NPs, and environmental aged ZnO NPs which resulted in three types of particles: 30 nm ZnO–Zn 3 (PO 4 ) 2 core–shell structures (p8-ZnO NPs), micron scale hopeite-like phase Zn 3 (PO 4 ) 2 ·4H 2 O (p6-ZnO NPs), and ZnS nano-clusters (s-ZnO NPs). Treatments included freshwater, saltwater (3 ppt), and the presence of sediment, with a final treatment where animals were contained within mesh baskets to prevent burrowing in the sediment. Dissolution was close to 100% for the pristine ZnO NPs and phosphate transformed NPs, while s-ZnO NPs resulted in only 20% dissolution in the water only exposures. In the freshwater exposure, the pristine and phosphate transformed ZnO NPs were more toxic (LC 50 values 0.11–0.18 mg L −1 ) than ZnSO 4 (LC 50 = 0.26 mg L −1 ) and the s-ZnO NPs (LC 50 = 0.29 mg L −1 ). Saltwater treatments reduced the toxicity of ZnSO 4 and all the ZnO NPs. In the presence of sediment, water column concentrations of Zn were reduced to 10% nominal concentrations and toxicity in the sediment with basket treatment was similarly reduced by a factor of 10. Toxicity was further reduced in the sediment only treatments where the sediments appeared to provide a refuge for H. azteca . In addition, particle specific differences in toxicity were less apparent in the presence of sediment. Bioaccumulation was similar across the different Zn exposures, but decreased with reduced toxicity in the saltwater and sediment treatments. Overall, the results suggest that H. azteca is exposed to ZnO NPs through the water column and NP transformations in the presence of phosphate do not reduce their toxicity. Sulfidized ZnO NPs have reduced toxicity, but their similar level of bioaccumulation in H. azteca suggests that trophic transfer of these particles will occur. 

   more » « less