Journal of Environmental Engineering

This research examined the dynamic physiological and transcriptional responses of Nitrosococcus mobilis, an unsquenced ammonia-oxidizing bacterium, to ${\mathrm{Cu}}^{2+}$ exposure. ${\mathrm{Cu}}^{2+}$ exposure caused decreases in N. mobilis nitrite production and oxygen uptake rates, and the release of intercellular ${\mathrm{K}}^{+}$ suggested that ${\mathrm{Cu}}^{2+}$ damaged the outer-membrane of N. mobilis cells. Shotgun DNA microarrays identified five previously unsequenced genes that were up- or down-regulated in response to ${\mathrm{Cu}}^{2+}$ exposure. The up-regulated putative efflux protein (HP 1900) and a copper containing NnrS protein (HP 1696) were found to correlate with ${\mathrm{Cu}}^{2+}$ concentrations. The up-regulation of these genes may be useful as a bioindicator of the presence of ${\mathrm{Cu}}^{2+}$ in natural and engineered systems. Finally, the expression of amoA and hao genes encoding the sole metabolic enzymes ammonia monooxygenase and hydroxylamine oxidoreductase, respectively, were measured. While hao expression did not change upon exposure to ${\mathrm{Cu}}^{2+}$, amoA expression increased upon exposure to slightly inhibitory concentrations of ${\mathrm{Cu}}^{2+}$ and decreased upon exposure to more severe inhibitory concentrations. This suggests that N. mobilis will adjust amoA expression based on available ${\mathrm{Cu}}^{2+}$ and energy.

Microbial marking for human fecal pollution with Enterococcus faecium relies on cultivation followed by the detection of the enterococcal surface protein gene ($Efm-es{p}^{+}$). This study examined the prevalence of the populations carrying the gene among the enterococci populations cultured out of domestic wastewater. Through year-long monitoring at a wastewater treatment plant in Michigan, the proportion of $Efm-es{p}^{+}$ in the enterococci population cultivated from sewage was 0.99%. A more sensitive detection method was developed for disinfected sewage and some impacted ambient waters by using larger membrane filters to increase the volume sampled, and preliminary application of the new protocol showed the presence of $Efm-es{p}^{+}$ in the Grand River, where enterococcal concentrations were low. An $Efm-es{p}^{+}$ strain isolated from wastewater in Michigan was very stable in phosphate buffer and river water at 4 and 25°C, suggesting that it can survive for months after being released into environmental waters. Among 44 samples from human and nonhuman sources, $Efm-es{p}^{+}$ was detected only from samples with human fecal pollution. These results provide evidence that the $Efm-es{p}^{+}$ with large volume sampling is useful as a microbial source tracking marker for disinfected wastewaters.

The effects of varying hydraulic retention time (HRT) and associated upflow velocity on mixing and reactor performance were evaluated in five lab-scale upflow anaerobic sludge blanket (UASB) reactors treating real domestic wastewater. The mixing and transport studies were carried out with the help of tracer experiments at various HRTs using a pulse tracer input. A number of existing models were assessed for the analysis of the time series of observed tracer concentrations. The plug-flow reactor (PFR) model with two-zone dispersion better simulated the time series of tracer concentrations at all HRTs than other models, such as single compartment dispersion, completely mixed flow reactors (CMFRs) in series, and a combination of CMFR and PFR. The dispersion coefficients obtained from the two-zone dispersion model correlated well with the dispersion analysis expression for flow in a circular cylinder, and the correlation can be used for the prediction of dispersion in a UASB reactor. The analysis of reactor performance data indicated that reduction of dispersion owing to decrease in the upflow velocity resulted in increased sulfidogenic activity in the reactor. This was attributed to the inability of the sulfate reducers to colonize in the reactor at high upflow velocity and mixing condition.

This study investigates the seasonal variation pattern of monthly wastewater influent data collected from the active treatment plants in Kuwait from 1999 to 2009. An attempt to examine the relationship with the population connected to the sanitary network is achieved indirectly by correlating monthly totaled influent data with climatological parameters of monthly averaged temperature and totaled rainfall. The periodograms of the influent, temperature, and rainfall data are also determined. The results reveal two significant periods in influent data of 12 and 6 months. The 12-month period is found in the two climatological data but the 6-month period exists only in rainfall data. The source of the 6-month period in the influent data has been related here to the illegal connection of storm sewers into the sanitary networks in many residential houses and to the typical variation of four seasons of the year during which the mode of people for watering activities or travel plans may change on average. The existing connection between residential stormwater and the sanitary networks may constitute a possible rainfall-harvesting system for arid countries as long as the wastewater plants have the capacity to handle the treatment process. The study concludes with the possibility of employing readily available climatological data to analyze the relationship between the seasonal wastewater influent and the population. The study also considers the detected periodicities to develop a time-series model that can be used to set a management plan for securing a nonconventional water supply for the country.

The use of mechanically biologically treated (MBT) waste as cover material for landfills during the aftercare period has gained in importance since the previous decade. The question arises how such materials change their properties under open field conditions. For field experiments, two MBT plants in Austria with related landfills were selected. A cover layer consisting of MBT material was applied on the surface and planted with grass and rape. The development without any vegetation served as a reference. Leaching, mineralization, and humification of waste organic matter were quantified. The impact of time, sampling depth, respective oxygen supply, and vegetation on the material was investigated. Intensive grass vegetation promoted mineralization and humification. Leaching of salts and the transformation of nitrogen were mainly influenced by time and depth. Aerobic conditions advanced degradation of still-reactive material. Under aerobic conditions, the remaining respiration activity was about two times lower than in the anaerobic zones. It was proven that well stabilized MBT material can be used as a cover layer with adequate vegetation.

This study examined nutrient fluxes between sediment and water with a laboratory-scale benthic chamber. This research targeted an artificial lake that had undergone water-quality problems. Two sites at Lake Asan, Site A in the vicinity of the dam and Site B at the inflow of the lake, were selected and characteristics of the sediments and their influence on the water quality of the lake were evaluated. Most of the inorganic phosphorus in the study area was in the form of apatite and nonapatite phosphorus (91.9% of Site A, 83.3% of Site B). Site B, with a fast-stream velocity, had larger particle size, smaller nutrient level, and smaller amounts of inorganic phosphorus than Site A. The benthic chamber experiment showed that overall fluxes of Site A were as follows: ammonia is $0.003\mu \mathrm{mol}{\mathrm{cm}}^{-2}{\mathrm{day}}^{-1}$, nitrate is $-0.067\mu \mathrm{mol}{\mathrm{cm}}^{-2}{\mathrm{day}}^{-1}$, and phosphate is $1.049\mathrm{nmol}{\mathrm{cm}}^{-2}{\mathrm{day}}^{-1}$. Site B showed an increase in phosphate concentration after a dissolved oxygen (DO) drop ($<3\mathrm{mg}/\mathrm{l}$), which resulted in smaller negative nitrate fluxes ($-0.043\mu \mathrm{mol}{\mathrm{cm}}^{-2}{\mathrm{day}}^{-1}$), larger positive ammonia ($0.137\mu \mathrm{mol}{\mathrm{cm}}^{-2}{\mathrm{day}}^{-1}$), and larger phosphate fluxes ($2.120\mathrm{nmol}{\mathrm{cm}}^{-2}{\mathrm{day}}^{-1}$) than at Site A. The movement of nutrients at the sediment-water interface was more sensitive to environmental conditions such as DO than other factors, such as sediment characteristics and chemical forms of nutrients. On the basis of the fluxes obtained from the benthic chamber, positive values are estimated for both phosphorus and nitrogen release rates. This indicates that during the sampling period sediment acted as a source of nitrogen as well as phosphorus to the overlying waterbody.

Advanced oxidation processes (AOPs), on the basis of photoelectrochemical reactions, constitute a good alternative for treating wastewaters contaminated with refractory organic compounds such as dyes. For this purpose, different approaches have been explored to develop novel photoanodes that can be efficiently used in these systems. In this context, this study deals with a comparison of indium tin oxide (ITO) thin films deposited at room temperature by pulsed laser deposition on flat glass and on silica optical fiber (${\mathrm{SiO}}_2$ core, 600 µm diameter) substrates. Characterization data reveal that nanostructured ITO thin films with resistivity values from $4.4\times {10}^{-2}$ to $5.6\times {10}^{-4}\Omega ·\mathrm{cm}$ were obtained. To build the photoanode, the ITO thin films were coated with a ${\mathrm{TiO}}_2$ layer deposited by using the electrophoretic method. The prepared ${\mathrm{TiO}}_2/\mathrm{ITO}$ bilayers on optical fibers showed a better photocatalytic performance than those deposited on flat glass substrates according to TOC and color removal measurements from dye contaminated water samples. These results suggest that the deposited materials exhibit suitable properties for their application in photoelectrocatalytic devices that, employing optical fiber as support and light transmitter, can be efficiently used for the elimination of organic contaminants in industrial wastewaters.

This study investigated the aniline oxidation at various conditions, namely, pH, ${\mathrm{H}}_2{\mathrm{O}}_2$ dose, ${\mathrm{Fe}}^{2+}$ dose, and aniline concentration, as well as the effects of inorganic ion concentrations on the electro-Fenton and fluidized-bed Fenton processes. Aniline degradation depended on the ${\mathrm{H}}_2{\mathrm{O}}_2$ and ${\mathrm{Fe}}^{2+}$ dose for both processes. The results showed that both processes had the best aniline oxidation efficiency at pH 2.8–3.2. In the electro-Fenton process, approximately 95% of the aniline was removed after 60 min. While the ${\mathrm{SiO}}_2$ carrier contents of fluidized-bed Fenton process was adjusted to $74\mathrm{g}/\mathrm{L}$, the aniline was gradually removed, and the degradation rate finally reached 83%. The inhibition effect of phosphate ions on aniline oxidation on both processes was more significant than that of chloride ions. Chloride ions have higher inhibition ability on aniline oxidation in the fluidized-bed Fenton process than in the electro-Fenton process. However, the inhibition of phosphate ions on aniline oxidation in the electro-Fenton process was more obvious than in the fluidized-bed Fenton process.

In the operation of porous media filtration systems, poor initial performance is often observed, in which particle removal is less than desired. Alum (${\mathrm{Al}}_2({\mathrm{SO}}_4{)}_3•14{\mathrm{H}}_2\mathrm{O}$), ferric chloride (${\mathrm{FeCl}}_3$), and polyaluminum chloride (PACl), are often used in drinking-water treatment to modify the surface properties of the particles being filtered and enhance their removal by filters; however, modification of the filter medium is not a common practice. In this research, these three coagulants were used to artificially modify a sand medium in situ by adding metal hydroxide precipitates onto the top of the filter before challenging the filter with an otherwise untreated kaolin suspension. After modification of the filter medium, high particle-removal efficiencies were achieved using a short (7.5 cm) sand column with $\cong 1\mathrm{mm}$ diameter sand. The best observed particle removal (96%) using alum and PACl occurred at the surface loading of 550 mmol of $\mathrm{Al}/{\mathrm{m}}^2$. The filter performance deteriorated at higher surface loadings. Fractional colloid removal increased with increased ferric chloride surface loading over the entire range of dosages tested (up to 97.5% at 2,200 mmol $\mathrm{Fe}/{\mathrm{m}}^2$). The experimental results suggest that pretreatment of filter media by application of Fe or Al hydroxides can eliminate the initial poor performance.

Adsorption is an effective remediation technique for petroleum hydrocarbons because of its ease of use and high efficiency. The utilization of high-carbon content industrial by-products in such applications can present significant economic and environmental advantages. In this study, batch adsorption tests and petrographic analyses were used to investigate the adsorption of two nonpolar petroleum contaminants, naphthalene and $o$-xylene, onto seven fly ashes with varying carbon contents, with powdered activated carbon (PAC) as a control. Six equilibrium isotherm models were used to evaluate the batch data. The results yielded nonlinear sorption isotherms characterized by high sorption capacity at low concentrations. The naphthalene and $o$-xylene adsorption capacity of the fly ashes was correlated with the unburned carbon content, specific surface area of the sorbent, and the percentage of the anisotropic and isotropic carbon content of the ash. On the basis of the Polanyi-Dubinin-Manes model, a pore-filling mechanism is the dominant mechanism for the adsorption of the nonpolar organic chemicals onto PAC, whereas the adsorption onto fly ash is likely to be governed by the unburned carbon content and the specific surface area of the ash.

Fly ash, an industrial by-product abundant in India, was treated with alkali and tested as a low-cost adsorbent for the removal of malachite green from an aqueous solution in a batch adsorption procedure. Effects of stirring rate, temperature, pH, initial dye concentration, contact time, and adsorbent dose were investigated. The adsorption was found to be strongly dependent on pH of the medium and the adsorption capacity decreased with an increase in temperature. The Langmuir isotherm model showed a good fit to the equilibrium adsorption data at all temperatures. The mean free energy ($E$) estimated from the Dubinin-Radushkevich model indicated that the adsorption mechanism was chemical ion exchange. The kinetic data were found to follow the pseudo second-order kinetic model. The rate constant decreased with the increase in temperature indicating the exothermic nature of adsorption. Intraparticle diffusion was not the sole rate-controlling factor. The Arrhenius and Eyring equations were used to evaluate the activation parameters. The activation energy ($E_a$) was estimated to be $56.08\mathrm{kJ}{\mathrm{mol}}^{-1}$. Gibbs free energy ($\Delta G^0$) was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. Results suggest that alkali-treated fly ash is a potential low-cost adsorbent for removal of malachite green from an aqueous solution.

To solve the disposal problem of wastewater treatment sludge (WWTS), WWTS was mixed with clay and water glass (sodium silicate) for the production of lightweight ceramsite. The effect of mass ratio of $\mathrm{CaO}/\mathrm{Si}{\mathrm{O}}_2$ (defined as basicity) on physicochemical characteristics of ceramsite and stabilization of heavy metals was investigated. It was found that the optimal basicity for making ceramsite ranges was 0.024–0.069. The main thermal changes ($\le 1,000°\mathrm{C}$) are phase transformations, which are caused by the evaporation and volatilization of water and carbonous matters and, finally, by the oxidation and decomposition of inorganic matters and minerals. Anorthite [$\mathrm{Ca}({\mathrm{Al}}_2{\mathrm{Si}}_2{\mathrm{O}}_8)$] and amorphous silica ($\mathrm{Si}{\mathrm{O}}_2$) increase as the basicity increases. The formation of more multiple crystalline phases is the main reason for the decrease in the compressive strength of the ceramsite with higher basicity. Leaching contents of Cd, Cu, Cr, and Pb decrease as the basicity increases. The stable compounds of heavy metals in ceramsite are $\mathrm{PbCr}{\mathrm{O}}_4$, ${\mathrm{Cr}}_2{\mathrm{O}}_3$, $\mathrm{CdSi}{\mathrm{O}}_3$, and CuO, which prove that strong chemical bonds are formed and the leachability of these heavy metals is greatly reduced by the crystallization and chemical incorporation process. Results indicate that basicity can be used as an important parameter for controlling the properties of ceramsite.