Lime softening produces an estimated 10,000 metric tons of dry drinking water treatment wastes (DWTW) per year, costing an estimated one billion dollars annually for disposal worldwide. Lime softening wastes have been investigated for reuse as internal curing agents or supplementary cementitious materials in concrete as well as a high-capacity sorbent for heavy metal removal. Lead, cadmium, and zinc are common heavy metals in groundwater contaminated by mine tailings. Cement-based filter media (CBFM) are a novel material-class for heavy metal remediation in groundwater. This study investigated the incorporation of DWTW as a recycled, low-cost additive to CBFM for the removal of lead, cadmium, and zinc. Jar testing at three different metal concentrations and breakthrough column testing using synthetic groundwater were performed to measure removal capacity and reaction kinetics. Jar testing results show as DWTW content increases at low concentrations, removal approaches 100% but at high metal concentrations removal decreases due to saturation or exhaustion of the removal mechanisms. Removal occurs through the formation of metal carbonate precipitates, surface sorption, and ion exchange with calcium according to the preferential series Pb+2 > Zn+2 > Cd2+. Removal kinetics were also measured through column testing and exceeded estimated calculations derived from batch jar testing isotherms due to the large formation of oolitic metal carbonates. Lead, cadmium, and zinc was concentrated in the column precipitates from 0.29, 0.23, and 20.0 mu g/g in the influent solution to approximately 200, 130, 14,000 mu g/g in the reacted DWTW-CBFM. The control and DWTW-CBFM columns had statically similar removal for zinc and lead. In the DWTW-CBFM, cadmium had decreased removal of approximately 25% due to proportionately decreased hydroxide content from cement replacement with 25% DWTW. This study shows the potential for DWTW as an enhancement to CBFM, thereby valorizing an otherwise waste material. Furthermore, the concentrative abilities of CBFM through precipitate and oolitic mineral formation could provide a minable waste product and close the waste-product cycle for DWTW.

AbstractArsenic-contaminated groundwater affects millions worldwide. A cement-based filter medium (CBFM) can be used to remediate heavy metals from groundwater. Recently, the desulfurization of flu...

Heavy metal contamination of surface and ground waters from anthropogenic sources presents a significant risk to human health and the environment. Leaching of metals such as lead, cadmium, and zinc from historic mining residuals has led to extensive groundwater contamination, for example, the elevated concentrations found at the Oronogo-Duenweg Superfund site in Joplin, Missouri, United States. Excessive wastewater buildup and storage at historic mines have also caused the release of metal toxicants into river systems, as was the case in the catastrophic 2015 Gold King mine spill into the Animas River in Western Colorado. Prevention of metals contamination and the reclamation of contaminated water for human and agricultural use are compelling reasons to improve heavy metal remediation technologies. Permeable reactive concrete (PRC) is a novel, cementitious material that demonstrates substantial removal capacity for heavy metals from aqueous solutions at the bench scale. This study investigated breakthrough testing of PRC using a synthetic groundwater solution of lead, cadmium, and zinc at concentrations similar to reported values for the Oronogo-Duenweg site of similar to 0.4 mg/L for lead and cadmium and 45 mg/L for zinc. Breakthrough testing elucidates removal mechanisms and reaction rates, but has never before been performed on PRC. Removal mechanisms documented in this study were precipitation of the hydroxide metals, complexation, and sorption of metals into the hydrated cement paste or metal precipitates. Demonstrated removal became more permanent over time, with total testing time around 260 days without breakthrough. Column breakthrough testing timeframes exceeded initial bench scale isotherm estimates by a factor of 20. Cost estimates for PRCs are similar to 1/6th to 1/12th the cost of comparable technologies for similar site applications. PRC has been shown in this study to perform equal to, or greater than, comparable technologies and could significantly reduce remediation costs for other contamination sites.

Catastrophic release of heavy metals from the King River mine in Colorado and the Minas Gerais dam in Brazil have brought to the forefront the importance of contaminant stabilization and remediation in surface waters. Permeable reactive materials are currently utilized for the remediation of heavy metals and other pollutants by employing reactive media to remove contaminants. This research investigated the use of fly ashes with loss on ignition or sulfur trioxide exceeding ASTM C618 limits to enhance pollutant removal in pervious concrete. The high carbon and sulfur contents of the noncompliant fly ashes provide additional capacity to remove lead, cadmium, and zinc. High-sulfur and high-carbon fly ashes were less effective in metal removal at higher metal concentrations but improved removal at lower concentrations. These results suggest pervious concrete can be designed as an effective remedial technique for use in many infrastructure applications, including beneath permeable pavement, permeable asphalt, revetment, permeable shoulders, gabions for slope stability, mine tailing dams, and emergency surface water cleanup.

Heavy metals contaminants include lead, chromium, arsenic, zinc, cadmium, copper, and mercury all of which can cause significant damage to human health and the environment as a result of their mobility and solubility within groundwater. In the Midwest portion of the United States, soil and groundwater based lead, zinc, and cadmium are the prominent pollutants of concern. While remedial technologies exist for heavy metals pollution, the majority of these solutions are expensive to design, maintain, and install. Drinking water treatment waste (DWTW) is a currently landfilled, relatively pure, industrial waste byproduct composed almost entirely of calcium oxide produced during water purification processes. Measured doses of drinking water treatment waste were submerged in synthetic groundwater solutions containing 0.01, 0.1, and 1.0 millimolar concentrations of lead, cadmium and zinc in order to determine if this material could provide remedial measures for heavy metals. In addition, the geomechanical properties and chemical composition of the material were determined. Removal rates varied based upon internal and external water content as well as flocculant formation. However, all tests verify that the material is capable of heavy metals removal at relatively rapid rates. This data suggests that when entrained in a previous matrix, the reactive nature of the byproduct sorbs ions in solution passing through the matrix.

Permeable reactive barriers (PRBs) are a well-known technique for groundwater remediation using industrialized reactive media such as zero-valent iron and activated carbon. Permeable reactive concrete (PRC) is an alternative reactive medium composed of relatively inexpensive materials such as cement and aggregate. A variety of multimodal, simultaneous processes drive remediation of metals from contaminated groundwater within PRC systems due to the complex heterogeneous matrix formed during cement hydration. This research investigated the influence coarse aggregate, portland cement, fly ash, and various combinations had on the removal of lead, cadmium, and zinc in solution. Absorption, adsorption, precipitation, co-precipitation, and internal diffusion of the metals are common mechanisms of removal in the hydrated cement matrix and independent of the aggregate. Local aggregates can be used as the permeable structure also possessing high metal removal capabilities, however calcareous sources of aggregate are preferred due to improved removal with low leachability. Individual adsorption isotherms were linear or curvilinear up, indicating a preferred removal process. For PRC samples, metal saturation was not reached over the range of concentrations tested. Results were then used to compare removal against activated carbon and aggregate-based PRBs by estimating material costs for the remediation of an example heavy metal contaminated Superfund site located in the Midwestern United States, Joplin, Missouri.

While great strides have been made in the design of dental composites and orthopaedic implants, improvements are still needed. For instance the life span of dental polymer composites is known to be significantly shorter than traditional amalgam restorations [1]. Similarly, the early failure rate of orthopaedic implants often leads to an intentional delay in the treatment of painful, debilitating joints to ensure patients don’t outlive the functional life of their prosthetics [2]. Stress concentrations within biomaterials may be partially to blame for these premature failures.

High wind events such as hurricanes are one of the leading causes of electricity transmission line failures. There are two main failure mechanisms associated with de-energized transmission systems during hurricanes: 1) failure of the super-structures or the support towers; and 2) breakage of the transmission lines due to extreme wind loads. This paper presents a methodology for analyzing the reliability of spatially distributed transmission lines under hurricane wind hazard. As a case study, the vulnerability of the spatially distributed 230kv transmission lines in south Carolina was analyzed using 40,000 years of simulated hurricane events. Since the response of transmission lines under wind loads is highly nonlinear, a simplified nonlinear analytical model, verified by a 3-dimentional finite element model, was developed to simulate the tension forces considering the geometric nonlinearity induced by the sagging of the transmission lines. The reliability analysis results are presented in a GIS map, which can be easily used in pre-hurricane planning by power companies.

The aesthetic appeal of composite-resin restoratives promotes their use, however their functional life is significantly shorter when compared to their metal counterparts.1 One possible reason is the effect of polymerization stress on marginal integrity. Shrinkage of the composite, and its associated stress, has been found to cause gap formation and stress interactions between the restorative and the adhesive. These gaps offer an ideal niche for bacteria, and, when compounded by the mechanical strain of chewing, can lead to premature failure of the restorative.2,3 Additionally, it is well known that incomplete conversion of the double bonds occurs during methacrylate polymerizations.4–7 A high degree of conversion is needed to prevent the presence of potentially hazardous monomers.8