Journal of Environmental Engineering

${\mathrm{Cu}}^{+}$-modified SBA-15 (${\mathrm{Cu}}^{+}/\mathrm{SBA}\text{-}15$, SBA-15 refers well-ordered hexagonal mesoporous silica) was prepared for adsorption of tetracycline (TC) by the pH adjusting reduction method. Some ${\mathrm{Cu}}^{+}$ species (${\mathrm{Cu}}_2\mathrm{O}$) are aggregated on the outside surface of SBA-15, and the other ${\mathrm{Cu}}^{+}$ species are highly dispersed in SBA-15 via $\equiv \mathrm{Si}\text{-}\mathrm{O}\text{-}\mathrm{Cu}$. Its adsorption mechanism was firstly studied via comparison with CuO/SBA-15. The TC adsorption kinetic of ${\mathrm{Cu}}^{+}/\mathrm{SBA}\text{-}15$ fitted the pseudo-second-order model well. The adsorption isotherms at 293, 303, and 313 K were determined and modeled with Langmuir and Freundlich equations, and the $Q_{\max }$ of ${\mathrm{Cu}}^{+}/\mathrm{SBA}\text{-}15$ for TC calculated from Langmuir model could reach $961.54\mathrm{mg}/\mathrm{g}$ at 313 K. Its good adsorption performance for TC is associated with the high surface area of SBA-15, highly dispersed ${\mathrm{Cu}}^{+}$ species, and mesoporous structure. The adsorption of ${\mathrm{Cu}}^{+}/\mathrm{SBA}\text{-}15$ for TC is an endothermic process, and adsorption heat is $66.88\mathrm{kJ}·{\mathrm{mol}}^{-1}$, which implies that the adsorption process of ${\mathrm{Cu}}^{+}/\mathrm{SBA}\text{-}15$ for TC is weak chemisorption. The adsorption mechanism of ${\mathrm{Cu}}^{+}/\mathrm{SBA}\text{-}15$ was mainly explored via comparing with CuO/SBA-15 by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) spectroscopy analysis. Besides the coordination complexation of ${\mathrm{Cu}}^{+}$ with ${\mathrm{NH}}_2$ radical of TC, the $\pi$-complexation between ${\mathrm{Cu}}^{+}$, and the benzene ring of TC improved the adsorption capacity of ${\mathrm{Cu}}^{+}/\mathrm{SBA}\text{-}15$ for TC comparing with CuO/SBA-15 and showed a dominant role for TC adsorption.

Coke-oven wastewater is generally characterized by having an array of pollutants such as cyanide, phenol, and ammoniacal-N. The present study focuses on the simultaneous removal of such pollutants from synthetic coke-oven wastewater using a bacterial isolate, Bacillus sp. NITD 19, collected from the contaminated site. Growth of bacterial sample was studied in Luria–Bertani (LB) medium. The tolerance limit of each pollutant was studied with the bacterial strain. One variable at a time (OVAT) approach was followed to see the individual effect of operating factors on the removal of each pollutant. Effective conditions like pH (8); inoculum size (IS) (4%); and initial concentrations of phenol ($100\mathrm{mg}/\mathrm{L}$), cyanide ($40\mathrm{mg}/\mathrm{L}$), and ammoniacal-N ($400\mathrm{mg}/\mathrm{L}$) were ascertained after OVAT analysis. Synthetic coke-oven wastewater (SCW) was prepared by mixing these three pollutants at their most effective initial concentrations. The time variation for removal of pollutants from individual aqueous solutions and SCW was studied at the most effective condition with the bacterial strain. Maximum removal of phenol ($79.88\%\pm 1.3\%$, $72.84\%\pm 1.21\%$), ammoniacal-N ($82.83\%\pm 1.23\%$, $80.25\%\pm 1.49\%$), and cyanide ($89.51\%\pm 1.44\%$, $79.78\%\pm 0.95\%$) were obtained from individual aqueous solution and SCW, respectively. Biomass extracted from the SCW solution was less than that obtained after the treatment of individual pollutants. Fourier-transform infrared spectrophotometry (FTIR) study and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis were performed for native and treated bacterial strain.

Landfill gas poses significant risk to global climate change. Landfill gas is composed of very high concentrations of methane (${\mathrm{CH}}_4$), nearly 50% by volume. The present study investigates the use of biochar amendment to silty clay landfill cover soil as a means of reducing ${\mathrm{CH}}_4$ emissions via long-term soil column incubation experiments. Amendment ratios of 2% and 10% (by weight) biochar-amended soil were evaluated in column tests; amendments were either applied to the zone in which ${\mathrm{CH}}_4$ oxidation activity was expected to be highest based on previous literature reviews [0.20–0.40 m (20–40 cm) below the surface] or throughout the entire soil layer [0–0.60 m (0–60 cm) below the surface]. Columns were incubated under simulated landfill cover conditions by applying synthetic landfill gas (60% ${\mathrm{CH}}_4$ and 40% ${\mathrm{CO}}_2$) at the base and atmospheric air flushing the headspace for $>400\mathrm{days}$. Initial and terminal physicochemical properties of the cover substrates were assessed to relate ${\mathrm{CH}}_4$ removal efficiency and long-term performance to key cover properties. An increase in soil porosity, water holding capacity, hydraulic conductivity, and overall soil moisture throughout testing was observed with biochar addition. The soil column with the greatest amount of biochar amendment (10% by weight) also had the highest average ${\mathrm{CH}}_4$ removal efficiency across all test stages [${\mathrm{CH}}_4$ loads of approximately $0.05-0.2\text{kg}{\mathrm{m}}^{-2}{\mathrm{day}}^{-1}$ ($50–200\mathrm{g}{\mathrm{m}}^{-2}{\mathrm{day}}^{-1}$)]. All tested designs displayed relatively high ${\mathrm{CH}}_4$ removal efficiencies ($>90\%$) at the ${\mathrm{CH}}_4$ loads tested. The study results suggest that the long-term performance of soil covers for enhanced ${\mathrm{CH}}_4$ oxidation may be improved by the addition of biochar, which may help to reduce moisture loss and minimize desiccation cracking and fugitive emissions in actual landfill covers.

This paper describes a novel cellular automata-based mesoscale multispecies reactive-transport (CA-MSRT) model for predicting microbial regrowth and trihalomethanes (THMs) formation in water distribution systems (WDSs) under different loading and temperature conditions. The kinetic models to analyze the degradation of chlorine, natural organic matter (NOM), and microbial biomass and formation of THMs during secondary chlorination applications are also proposed. The CA-MSRT model was applied to a benchmark WDS with two water sources (river and lake), a problem well tested by many researchers. A 60% reduction in total organic carbon (TOC) combined with chlorine application of $1\mathrm{mg}/\mathrm{L}$ at the lake water source has resulted in regulating the microbiological and chemical quality of the delivered water at the outlet points. Results indicate that supplementing the chlorine levels through secondary disinfection stimulates formation of THMs and thereby compromises the chemical quality of the delivered water. It was found that the fractions of THMs formed from the carbon content associated with attached and suspended microbial biomass were only $<2\%$, and the remaining fractions were derived from NOM. Overall, the study confirmed the benefits of reducing the organic matter content and optimal selection of the chlorine dose at the source point in contriving the water quality at the outlet points of WDSs.