The coal-fired power industry faces pressing needs to improve disposal practices for the generated flue gas desulfurization (FGD) wastewater and coal fly ash (CFA). Zero-liquid-discharge (ZLD) strategies are gaining significant interest and can be achieved by co-disposing the concentrated FGD wastewater brine with CFA and Portland cement in a solidification/stabilization (S/S) process—a novel strategy that manages two wastes simultaneously. In this study, the stability of such S/S solids produced by utilizing bituminous CFA was evaluated for the mass transport release of major components (Ca2+, Cl−, Mg2+, Na+, and SO42−) and heavy metal oxyanions (As, Cr, and Se) in long-term leaching tests. Particularly, the impact of FeSO4 (FS) addition to the S/S mixture for the purpose of enhancing heavy metal immobilization was assessed. Results showed that FS addition to the S/S process decreased the solid’s cumulative release and flux at shorter leaching times for the major components Ca2+, Cl−, Mg2+, Na+, and SO42−, but this effect was diminished over time. However, FS addition significantly decreased release of oxyanions As, Cr, and Se throughout the prolonged leaching time, indicating that FS addition could increase the likelihood of successful long-term disposal of S/S solids of concentrated FGD brines containing these heavy metal oxyanions. Results of this study can help the power industry to further assess and optimize the co-disposal ZLD strategy to minimize environmental risks.

To achieve zero liquid discharge, the flue-gas-desulfurization (FGD) wastewater at coal-fired power plants can be concentrated into brine through thermal evaporation to maximize water reuse; however, the hot brine generated requires further treatment prior to disposal. To address this need, this study investigates the performance of aged, micron-sized zero-valent iron (ZVI) for heavy metal removal in simulated and real FGD hot brines, which was scarcely studied previously. The effects of temperature, pH, total dissolved solids, ZVI dosage, major cations, nitrate and sulfate on the reactivity of ZVI in the brines were evaluated. Among many factors, higher temperature and Mg2+ exert the dominant influence. At 80 degrees C, almost 100% of arsenate (1 mg/L) and chromate (1 mg/L) can be removed in < 5 min using 4.17 g/L of ZVI in simulated brines, while selenate (25 mg/L) and cadmium (5 mg/L) can be completely removed within 30 min. Mg2+ ions naturally present in FGD brines account for the depassivation of aged ZVI. X-ray diffraction results suggest that green rust is the reactive intermediate for selenate and cadmium removal. Overall, this study demonstrates that ZVI is an effective material for removing heavy metals in hot FGD brines generated through thermal evaporation at power plants.

Effective management of flue-gas-desulfurization (FGD) wastewater and coal-combustion-residues (CCRs) are major challenges in the coal-fired power industry. The zero-liquid-discharge (ZLD) method of combining FGD brines and CCRs in solidification/stabilization (S/S) is promising due to its potential of treating both wastes in the same process. This study evaluated the performance of such a ZLD method for immobilizing heavy metals (Se, As, Cd and Cr) and chloride in FGD wastewater and/or CCRs. Effects of different coal fly ash (bituminous (BCFA) and sub-bituminous (SCFA)), activating agent (Portland cement (PC) and lime) and pretreatment of brines by zero valent iron (ZVI) on the S/S process were evaluated. Short-term and long-term leaching tests were conducted to evaluate performance of the S/S solids in pollutant retainment. The pre-treatment of FGD brine by ZVI enhanced the retainment of heavy metals when BCFA was used, but not when SCFA was used since it already performed quite well without ZVI pretreatment. Quantitative X-ray diffraction and scanning electron microscopy analyses strongly indicated the formation of Friedel's salt, Ca2Al(OH)6(Cl,OH)·2H2O, is critical in the retainment of heavy metals and chloride. SCFA contained higher lime and reactive aluminate contents than BCFA; thus, S/S solids made with SCFA contained higher amounts of Friedel's salt.

Combination and optimization of an iron-based reduction and solidification/stabilization (S/S) processes for the immobilization of heavy metals in concentrated flue gas desulfurization (FGD) brines was investigated. The performance of aged zero valent iron (ZVI) on heavy metal removal in simulated FGD brine and real FGD brine was investigated. Batch studies were performed to evaluate the effects of temperature, pH, TDS, ZVI dosage, nitrate and sulfate on ZVI’s reactivity in simulated brine. Temperature is the dominant factor on ZVI’s reactivity compared to other factors being studied. At 80°C, almost 100% removal of arsenate (1 ppm) and chromate (1 ppm) can be achieved in less than 5 min using 4.17 g/L of ZVI in simulated brine, while selenate (25 ppm) and cadmium (5 ppm) could be completely removed within 30 minutes. The process of heavy metal retainment by S/S of the ZVI-pretreated or non-pretreated FGD brines was studied by using class C (subbituminous) and F (bituminous) coal fly ash, with the addition of Portland cement or lime. Leaching tests were performed to evaluate the performance of each S/S recipe by comparing the heavy metal concentrations in the leachate. The pre-treatment of brine by ZVI enhanced the retainment of heavy metals when Class F ash was used, but not when Class C ash was used since it already performed quite well without ZVI pretreatment.

Southern Research, as the primary awardee, with sub-awardees ArcSec Technologies, LLC (ArcSec) and Reaction Engineering International (REI) have investigated a plasma arc based thermal process intended to concentrate rare earth elements (REE) from coal fly ash. Successful demonstration of the technology would contribute to the effort for realizing a competitive, domestic REE value chain thereby reducing U.S. dependence on foreign supply, maintaining national security interests, and creating opportunities for economic growth. The originally proposed concept included two technology options – 1) a smelting process and 2) a smelting plus vaporization and condensation process. For both options, coal fly ash would be smelted in a plasma arc heated furnace under reducing conditions to separate ash into molten slag and reduced metal (primarily iron) phases. During smelting, it was expected that the REE would also be reduced to metals and partition mostly to the iron phase. During the first year of work, sample coal ash feedstocks were acquired and characterized, feasibility of the smelting process was evaluated in bench-scale experiments, and the vaporization/condensation process was investigated through equilibrium and CFD modeling studies. From the feedstock characterization, REE content for the coal ash samples obtained was measured to be in the range of 302 – 1219 ppm with average at 537 ppm. Though it was successfully demonstrated that ash could be separated into slag and metal phases, the bench-scale experiments were only marginally successful at collecting REE in the metal phase. Producing REE concentrates near the DOE goal of 2%, however, has not been achieved. From the modeling studies, the vaporization/condensation process was predicted to be effective for separating individual REE and producing enriched metal fractions with total REE content higher than 2%, provided the smelting process performed as intended. Supplemental smelting experiments and thermodynamic modeling studies, conducted during the second year of work, indicated a number of technical modifications that could lead to producing higher REE concentrates from coal ash. The strategy shifted to reducing as much of the ash oxides to metals as possible, leaving the REE more concentrated in the remaining slag. Results from later experiments based on the modified approach showed improvements in REE recovery and concentration levels in smelted products. SEM-EDS analyses on product specimens showed agglomerations of reduced metal REE crystals at much larger length-scales as compared to REE content in raw ash.

The sorption behavior and mechanisms of Se from wastewater with high salinity are unclear, a scenario that can be encountered in the flue-gas-desulfurization (FGD) blowdown at coal-fired power plants. In this study, we investigated the uptake behavior and mechanisms of Se(IV) and Se(VI) by a coal fly ash/cement composite at high ionic strengths (IS) of up to 3.0M NaCl or CaCl2 using batch sorption experiments, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and X-ray absorption spectroscopy. NaCl, regardless of IS, only caused slight changes in Se(IV) and Se(VI) uptake. Presence of CaCl2 significantly enhanced Se(IV) uptake, but had minor effect at low IS (≤0.3M) and no effect at high IS (>0.3M) on Se(VI) uptake. Both Se(IV) and Se(VI) mainly formed outer-sphere surface complexes in the presence of NaCl. The enhanced Se(IV) uptake by CaCl2 is likely due to the formation of Ca-SeO3 precipitate(s). Outer-sphere complexation is the main mechanism for Se(VI) sorption in the presence of CaCl2, with additional formation of minor amounts of inner-sphere complex at IS >0.3M. The results added new mechanistic insights for Se removal from industrial wastewaters with high salinity and will be useful for immobilization of Se in the co-management of FGD blowdown and coal fly ash wastes.

Southern Research Institute, with project partners BKT United (Anaheim, CA) and M2 Water Treatment, Inc. (Raleigh, NC) received an award from Research Partnership to Secure Energy for America (RPSEA) to develop an innovative, cost effective, and robust approach for treatment of shale gas fracturing water that produces National Pollution Discharge Elimination System (NPDES) quality water for discharge and/or reuse. This approach combines and optimizes four technologies. Magnetic ballast clarification (MBC), vortex-generating nanofiltration (NF) membrane, and conventional reverse osmosis (RO) will be used to remove total suspended solids (TSS) and total dissolved solids (TDS), e.g., metals and naturally occurring radioactive materials (NORMS) from flowback and produced waters. Residues containing metals, NORMs, and/or trace elements will be managed with hydrogel adsorbent or precipitation / solidification / stablization.

The United States Environmental Protection Agency (USEPA)’s announcement that it will revise the effluent limitation guidelines for steam electric power generating units could affect not only how power plants use water, but also how they discharge it. The revised guidelines may lower discharge limits for various contaminants in flue gas desulfurization (FGD) wastewater including mercury, selenium, arsenic, and nitrate/nitrite. Although the specific details of the guidelines are unknown at present, the power industry is evaluating various technologies that may address the new effluent limitation guidelines and promote water conservation. Moreover, the power industry is looking for avenues to increase water usage efficiency, reuse and recycle throughout its plant processes. Final rule approval is expected by the middle of 2014 and new regulations are expected to be implemented between 2017 and 2022 through 5-year NPDES permit cycles. discharge limits for various contaminants including arsenic, mercury, selenium, and nitrate/nitrite [1]. These pollutant limits may be below the levels achievable today with conventional treatment [2]. A growing interest exists in zero liquid discharge (ZLD) facilities and processes in power plant operations. Potentially stringent discharge limits along with water conservation and reuse efforts are two of the major drivers to achieve ZLD. Potential pollutant levels are so low that ZLD may be the best option, if not an outright requirement [1]. Thermal ZLD systems have been the subject of increased interest and discussion lately. They employ evaporating processes such as ponds, evaporators and crystallizers, or spray dryers to produce a reusable water stream and a solid residue (i.e. waste). Evaporators and crystallizers have been employed in the power industry for a number of years. However, typical A growing interest exists in zero liquid discharge (ZLD) facilities and processes in power plant operations. Potentially stringent discharge limits along with water conservation and reuse efforts are two of the major drivers to achieve ZLD. Potential pollutant levels are so low that ZLD may be the best option, if not an outright requirement. A key disadvantage of thermal ZLD is its high capital cost. One way to reduce this cost is to pre-treat the liquid stream using innovative membrane technologies and reverse osmosis (RO).

Development of the Water Research Center (WRC) at Georgia Power's Plant BowenThe Water Research Center (WRC) is located at Georgia Power Company's (GPC) Plant Bowen near Cartersville, Georgia outside of Atlanta. Operated by Southern Research Institute, the WRC is an industry resource providing independent performance evaluations of technologies to address water withdrawal, consumption, usage efficiency, treatment, recovery, and reuse throughout the power generation...Author(s)Jay WosJay RenewBen PakzadehJeff WilsonGeorge OffenRichard BreckenridgeSourceProceedings of the Water Environment FederationDocument typeConference PaperPublisherWater Environment FederationPrint publication date Oct, 2013ISSN1938-6478DOI10.2175/193864713813673866Volume / Issue2013 / 16Content sourceWEFTECCopyright2013Word count157

A robust and sensitive method for the detection of fluoroquinolones, sulfonamides and trimethoprim has been developed. Wastewater samples were acidified and extracted through an anion-exchange cartridge in tandem with a hydrophilic–lipophilic balance (HLB) cartridge, a procedure that reduced interferences from wastewater organic matter. The extracted antibiotics were analyzed using liquid chromatography electrospray mass spectrometry and selected ion monitoring. Quantification of antibiotics was assessed both by internal standard and standard addition methods. Average recoveries for a range of wastewater matrices were 37 to 129% for a 1 μg/L spiking concentration. The method detection limits (MDLs) of antibiotics in deionized water, final and secondary effluent ranged from 2 to 7 ng/L, from 20 to 50 ng/L, and from 30 to 90 ng/L, respectively. Assessment of matrix interference shows that signal suppression and MDL increases with higher amounts of organic matter in the sample. Analyses of samples from two municipal wastewater treatment plants indicate that ciprofloxacin, ofloxacin, sulfamethoxazole and trimethoprim are present in the secondary effluents at median concentrations of 100–160, 205–305, 395–575, and 40–705 ng/L, respectively.

Antibiotics are among the emerging microcontaminants in water because of concerns of their potential adverse effects on the ecosystem and possibly on human health. Antibiotics are likely to be released into the aquatic environment via wastewater effluent and agricultural runoff as a result of incomplete metabolism, ineffective treatment removal or improper disposal because large quantities of antibiotics are used annually in human therapy and in agriculture. Despite large quantities of use, published data on the amounts and use patterns of antibiotics are scarce. To assess the magnitude of the potential risks associated with antibiotics, a comprehensive literature review was conducted on the usage, occurrence, and behavior of antibiotics. To identify antibiotics that are likely to be present in water sources, concentrations of antibiotics in municipal wastewater and animal waste in the United States (U.S.) were estimated and were classified according to chemical properties. The estimation of human health antibiotics was based upon the number of prescriptions administered. The estimated concentrations of antibiotics in untreated wastewater range from 3.9 ng/L to approximately 27,000 ng/L. The estimation of animal health antibiotics was based upon the subtherapeutic usage in feed for growth promoting. Considerable variation in antibiotic usage exists among different animal species. Reported data on the occurrence of antibiotics in the aquatic environment confirm the persistence of certain antibiotics. Although information is limited, studies on the transformation and sorption of antibiotics indicate that these processes significantly affect the fate of mo st classes of antibiotics. By combining information on environmental fate with the predicted concentrations, we identify that antibiotics of sulfonamides and fluoroquinolones are the most likely water contaminants, followed by macrolides. Among sulfonamide and fluoroquinolone antibiotics, sulfamethoxazole and ciprofloxacin are most likely to be present in municipal wastewater effluent and sulfamethazine is most likely to be present in agricultural runoff. Azithromycin and tylosin are the most likely macrolides present in municipal wastewater effluent and in agricultural runoff respectively. An occurrence study, which is currently underway, focuses on three of the potential antibiotic contaminants, ciprofloxacin, sulfamethoxazole and sulfamethazine, identified by literature review. Solid phase extraction methods were developed. Recoveries ranged from approximately 45 to 106 percent. Analysis of the three antibiotics was conducted by liquid chromatography mass spectrometry (LC-MS). Additionally, high performance liquid chromatography (HPLC) with fluorescence detection was employed for ciprofloxacin analysis. Preliminary results indicated the presence of ciprofloxacin in secondary wastewater effluent at approximately 80 to 150 ng/L. Sulfamethoxazole was detected in one of the wastewater samples. Sulfamethazine was not detected. Concentrations of antibiotics were found to be much lower or below the detection limits in the effluent of advanced treatment processes including granular activated carbon and ozonation, indicating significant removal by those processes.