Journal of Hazardous, Toxic, and Radioactive Waste

Pump and treat groundwater remediation systems typically rely on utility power to continuously pump contaminated groundwater to an above-ground treatment unit. The use of renewable energy for a pump and treat remediation system reduces the output of harmful greenhouse gases and the need for coal-based utility power. This paper describes a hypothetical renewable energy-powered pump and treat remediation system that uses an off-grid photovoltaic array to power a submersible solar water pump. The pump operates on an intermittent schedule predicted by available solar irradiance. The intermittently operated pump generates an effective capture zone defined by multiple transient capture zones. Effective capture zones are modeled using Visual MODFLOW and MODPATH and compared against a continuously pumped steady-state capture zone. The comparison showed that a renewable energy-powered intermittently pumped remediation system performs 90% as effectively as a utility-powered continuously pumped remediation system and is cost effective when the capital cost and annual costs of the utility-powered system exceed the capital cost of the renewable-energy powered system.

Removal of arsenic using an iron-oxide-based adsorbent (IBA) was examined for the groundwater near a black foot disease epidemic area, Chiayi, Taiwan. The groundwater was first characterized for arsenic speciation and water quality that may influence arsenic removal. Arsenic in the present groundwater was predominately the pentavalent species and dissolved form ($<1\mathrm{kDa}$) and with a concentration of $\sim 30\mathrm{\mu g}/\mathrm{L}$. Adsorption uptake of arsenate onto the studied IBA in the groundwater was only two-thirds of that in deionized water. Among the 10 ions, metals, and organics examined, only phosphate and natural organic matter (NOM) influenced the adsorption of arsenate onto iron-oxide-coated diatomite (IOCD). To further identify the governing factor for the suppression of arsenate uptake on IOCD, adsorption experiments were conducted using coagulated groundwater, which may remove phosphate and NOM to different degrees. Experimental results confirmed that phosphate was the only important factor to suppress arsenate adsorption to IOCD in the studied groundwater.

Urban storm water runoff consists of unacceptable levels of nutrients and heavy metals, and a mixed-media filter system is proposed to treat such storm water with multiple contaminants. In this study, a two-dimensional filter simulation test apparatus was constructed to examine the effectiveness of mixed media for the removal of multiple contaminants from synthetic storm water. The mixed media, selected based on several series of batch and column experiments in previous studies, consisted of a mixture of calcite, zeolite, sand, and iron filings. The mixed media was tested for removal of coexisting nitrate, phosphate, Ni, Cu, Cd, Cr, Pb, and Zn at concentrations and conditions relevant for typical urban storm water. Results show that the mixed-media filter was able to maintain high flow rates without any clogging issues, with an average hydraulic conductivity around $30\mathrm{cm}/\min$. No significant initial release or final desorption of the contaminants was observed. The filter system proved effective for the simultaneous removal of nutrients and heavy metals from the storm water, except for Ni, which had significantly lower removal efficiency than the other metals. Overall, the study indicated that a mixed-media filter can be designed with high contaminants removal capacity, but additional studies are recommended for evaluating long-term performance of the mixed-media filter under variable storm water field conditions.

In this study, the occurrence and treatment of two earthy-musty odorants, geosmin and 2-MIB, produced by cyanobacteria is investigated at two conventional drinking-water treatment plants (WTPs) at Kinmen Island, Taiwan. Samples of the source, processed, and finished waters and tap water at the two WTPs were collected and analyzed. Both geosmin and 2-MIB were commonly detected in most water samples, with the 2-MIB concentration much higher than the geosmin concentration. About 78% of the source water samples and 35% of the finished and tap water samples showed detected 2-MIB levels higher than the odor threshold concentration (OTC, $\sim 10\mathrm{ng}/\mathrm{L}$). Sampling and analysis of the reservoir water indicated that 2-MIB is uniformly distributed in the reservoir, with $\sim 70\%$ of which existing in the dissolved phase. The chlorination study of the raw water indicates that both geosmin and 2-MIB are resistant to chlorine. However, the cyanobacterial cells in raw water were effectively ruptured within15 min of the contact time when a chlorine dosage of $6.4\mathrm{mg}/\mathrm{L}$ was applied at the WTPs. A monitoring of the processed water at WTPs shows that the flotation process is most effective to the removal of cyanobacteria, with about 77–79% efficiency, compared to $\sim 99.4\%$ achieved with the whole treatment train. Removal of 2-MIB by the treatment processes before flotation was only about 17–28%, which may be limited to the low ratio of cell-bound 2-MIB. The two sand filtration processes removed 23–47% of 2-MIB, due probably to the biological degradation of dissolved 2-MIB. For the two WTP studied, the removal of 2-MIB was about 74%. It is shown that 2-MIB is a major odorant in the drinking water source and the finished water at Kinmen Island. The current processes are not sufficient to remove 2-MIB to a level below the OTC. Advanced processes are needed to effectively remove the odorant.

This paper deals with the physicochemical treatment of petrochemical wastewater emanating from a purified terephthalic acid (PTA) manufacturing unit. The PTA wastewater has a very high chemical-oxygen demand ($\mathrm{COD}=\mathrm{3,530}\mathrm{mg}·{\mathrm{dm}}^{-3}$) and contains various acids like terephthalic acid (TA), benzoic acid (BA), acetic acid, and $p$-toluic acid ($p-\mathrm{TA}$), in addition to aldehydes. The treatment of this wastewater with 1 N sulfuric acid (pH 2.0) at 25°C resulted in the removal of 53.2% of the COD, $>90\%$ of TA, and $>60\%$ of BA in the form of solid precipitate. Subsequent treatment of the clear supernatant with granular activated carbon (GAC) resulted in an overall removal of $>99\%$ of TA and BA in addition to 82.7% of the COD. The GAC is basic in nature with its pH at the point of zero charge being 8.3. It was also predominantly microporous with a BET surface area of $134.69{\mathrm{m}}^2·{\mathrm{g}}^{-1}$. Fourier-transform infrared spectroscopy of the GAC, before and after the adsorption of PTA wastewater components, was carried out to understand the COD and acid-removal mechanism. The optimum conditions for the treatment were pH 4.0, GAC dosage of $20\mathrm{g}·{\mathrm{dm}}^{-3}$, and ambient temperature. The COD removal mechanism was adsorption and precipitation of undissociated acid molecules within the pores. The adsorption was exothermic in nature and the Freundlich isotherm equation represented the experimental adsorption data well. Thermal regeneration of the spent GAC showed an improvement in the adsorption characteristics with the formation of mesopores, and resulted in the enhanced COD removal during five consecutive adsorption-desorption cycles. The spent carbon can be used as a cofuel for firing in the boiler furnaces for extracting its energy value.

The hazardous wastes generated in the manufacture of high-explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) from starting material 1,3,5-trichlorobenzene are described. The process generates three kinds of effluents: water-based nitration effluent (WNE), toluene-based amination effluent (TAE), and water-based amination effluent (WAE). These three effluents are analyzed as per the country’s pollution control norms. Both WNE and WAE need treatment before discharge to the environment. These treatment methodologies are discussed. The solvent recovery from TAE was found highly feasible. However, some solid organic explosive waste ($\sim 100\mathrm{kg}/\mathrm{ton}$ TATB produced) is generated from the residue of TAE after solvent recovery. The composition of this solid waste is analyzed by gas chromatography and its potential explosiveness is characterized by a sensitivity test. The disposal methodology of the solid wastes generated from WNE, TAE, and WAE are also discussed.

Membrane filtration systems can handle varying wastewaters with simple and robust operation. However, current low permeate flux rates attributed to solids accumulation at the membrane surface limit more widespread technology use. This work seeks a better understanding of flux performance relative to solids concentration and transmembrane pressure coupled with potential flux enhancements. Enhancements revolve around disturbing solids accumulation at the membrane surface by physical cleaning or periodic flow reversal. Results indicate both rotary and tubular membranes produce consistent particle-free, low-turbidity permeate at varying levels of feed solids concentrations. Rotary membranes may produce only slightly greater permeate flux rates than tubular membranes at low feed solids concentration, but the difference increases drastically as feed solids concentration increases. Rotary membrane systems can concentrate wastewaters to greater than 40% solids, but the greater the feed solids, the less additional pressure increases flux. Membrane surface cleaning by continually cleaning via nylon brushes contacting the membrane surface, periodic sponge ball surface cleanings, or periodic flow reversal can significantly increase permeate flux rates (2 to 20 times).

The ability of live and dead biomass of indigenous Aspergillus niger was examined for the removal of uranium (VI) from dilute aqueous solutions. The influences of different experimental parameters such as initial solution pH, initial uranium concentration, biomass concentration, and contact time were investigated. The results indicated that the maximum sorption of biomass was observed at pH 5 and pH 4, and biosorption equilibrium was established in 120 and 60 min, for live and dead biomass, respectively. Optimal biosorption was observed at concentrations of 0.2 and 0.3 g dry biomass per 100 mL for live and dead biomass, respectively. Langmuir and Freundlich models were well able to explain the sorption-equilibrium data with satisfactory correlation coefficients higher than 0.9 for both sorbents. Moreover, the Langmuir isotherm in linear form fit better for both live and dead biomass of A. niger. The kinetic study showed that the pseudosecond-order model was appropriate to describe the sorption process.

This study presents an evaluation of 9.5-mm minus steel slag fines (SSF) to immobilize lead (Pb), tungsten (W), and phosphate (P as ${\mathrm{PO}}_4$) at total contaminant dosing concentrations of $\mathrm{10,000}\mathrm{mg}/\mathrm{kg}$ (W, ${\mathrm{PO}}_4$) and $\mathrm{100,000}\mathrm{mg}/\mathrm{kg}$ (Pb), as a potential new construction material for firing-range backstop berms (or treating firing-range soils). Direct contaminant uptake and kinetic rate, rerelease, and mineralogical studies were undertaken for metal loadings totaling up to six combinations of Pb, W, and ${\mathrm{PO}}_4$. Batch rate studies showed that $>95\%$ of Pb and W were removed from aqueous solution within 2 h in the presence of the SSF media. For equivalent aqueous doses of $500\mathrm{mg}/\mathrm{L}$ (W, ${\mathrm{PO}}_4$) and $\mathrm{5,000}\mathrm{mg}/\mathrm{L}$ (Pb), the TCLP-Pb concentrations for all multielement suites were $<0.3\mathrm{mg}/\mathrm{L}$, which is much less than the TCLP-Pb criterion of $5.0\mathrm{mg}/\mathrm{L}$. For the P-Pb-W suite (all three contaminants present simultaneously), the SPLP-W concentrations ($<0.35\mathrm{mg}/\mathrm{L}$) were lower than the TCLP-W concentrations ($<1.1\mathrm{mg}/\mathrm{L}$) regardless of ${\mathrm{PO}}_4$ dose. Leached phosphate concentrations from the P-Pb-W suite were below or hovered at the detection limit ($0.5\mathrm{mg}/\mathrm{L}$) under SPLP and TCLP conditions, respectively. A mineralogical evaluation revealed that lead pyromorphite [${\mathrm{Pb}}_5{({\mathrm{PO}}_4)}_3\mathrm{OH}$] and scheelite [$\mathrm{Ca}({\mathrm{WO}}_4)$] were the key ${\mathrm{PO}}_4$-containing, Pb-containing, and W-containing phases.