Journal of Environmental Engineering

Bench-scale jar testing was conducted to compare the cost and performance of three hydrolyzing and two prehydrolyzed coagulants for treatment of an organic-laden ($>8\mathrm{mg}/\mathrm{L}$ total organic carbon) surface water slough. Coagulant dose and pH were varied between 80 and $240\mathrm{mg}/\mathrm{L}$ and 4 and 8 pH units, respectively. Dissolved organic carbon (DOC) removal performance data were depicted graphically and modeled using empirical regressions. Ferric chloride and aluminum chlorohydrate achieved the highest organic removal (85 and 70%, respectively) and color reduction (98 and 97%, respectively) at dose concentrations of $120\mathrm{mg}/\mathrm{L}$ as ${\mathrm{FeCl}}_3$ and $100\mathrm{mg}/\mathrm{L}$ as polyaluminum hydroxychloride, respectively. Cost diagrams were developed using DOC removal performance data. Ancillary effects including alkalinity retention, settling time, and sludge settling rates were also considered in this comparison. This research provides insight regarding the relationship between process conditions and the advantages of using prehydrolyzed coagulants for DOC and color removal from surface water.

Bioleaching treatments can significantly improve the dewaterability of sewage sludge. However, the exact mechanisms of the improvement of sludge dewaterability by bioleaching are as yet unclear. In this study, the variation of extracellular polymeric substances (EPS) content along with bound water content in sludge during bioleaching was investigated in detail. Results showed that sludge dewaterability was improved rapidly and then deteriorated slowly. The improvement of sludge dewaterability in the first 48 h of bioleaching was primarily attributable to the removal of sludge EPS, and the deterioration of sludge dewaterability in the following 144 h primarily resulted from the unexpected increase of sludge EPS amount in the latter stage of the bioleaching treatment. The Spearman correlation coefficients of EPS content and bound water content, EPS content and the specific resistance to filtration (SRF), and bound water content and SRF were 0.81, 0.83, and 0.94, respectively. Furthermore, the dewaterability of original sludge or the sludge being bioleached for eight days was improved by removing EPS through centrifugation, on the contrary, re-adding EPS especially from Acidithiobacillus ferrooxidans to bioleached sludge resulted in poor sludge dewaterability. Therefore, bioleaching is an innovative approach in enhancing sludge dewaterability, and an EPS level of bioleached sludge decides sludge dewaterability.

This study was designed to identify the effects of variable concentrations of chloride on microbial regrowth, disinfection efficacy, and metal release in drinking water distribution systems. Annular reactors (ARs) containing cast iron or polycarbonate coupons were operated in this study to simulate distribution systems. Experiments were conducted with test water containing chloride concentrations of 10, 75, and $250\mathrm{mg}/\mathrm{L}$. Chlorine disinfection was applied to achieve 0.2 and $1.0\mathrm{mg}/\mathrm{L}$ free chlorine residuals. Results showed that the ARs operated with elevated chloride concentrations were not significantly different from the ARs operated with low chloride concentrations in terms of microbial regrowth. However, there was a significant increase in iron concentrations after chlorination in the high chloride ARs. Further, more iron release was observed in these ARs at $1.0\mathrm{mg}/\mathrm{L}$ compared to $0.2\mathrm{mg}/\mathrm{L}$ chlorine residual. Higher chlorine doses were required to achieve goal residuals for those ARs with higher chloride concentration in cast iron systems. However, in polycarbonate systems, similar doses of chlorine were required to achieve the target free chlorine residual in both low-chloride and high-chloride ARs.

Single-stage and two-stage treatment processes using ferric sulphate (${\mathrm{Fe}}_2({\mathrm{SO}}_4{)}_3$) coagulation, lime precipitation, ballasted flocculation, and sedimentation were compared for the removal of high concentrations (i.e., $60\mathrm{mg}/\mathrm{L}$) of arsenic in a synthetic mine water (SMW). Single-stage treatment was found to reduce arsenic to $0.39\pm 0.04\mathrm{mg}/\mathrm{L}$ in As(V) SMW and $0.78\pm 0.07\mathrm{mg}/\mathrm{L}$ in As(III) SMW using either preoxidation with ${\mathrm{KMnO}}_4$ or higher pH and coagulant dose compared to As(V) (i.e., 9.0 to 9.5 versus 5.5 to 6.0 and 151 versus $76\mathrm{mg}\mathrm{Fe}/\mathrm{L}$), above a proposed national discharge guideline of $0.10\mathrm{mg}\mathrm{As}/\mathrm{L}$. The two-stage treatment process was able to reduce total arsenic concentrations to $0.004\pm 0.002\mathrm{mg}/\mathrm{L}$ for As(V) SMW using coagulation and ballasted flocculation alone in Stage 2, $0.010\pm 0.008\mathrm{mg}/\mathrm{L}$ for As(III) with oxidation upstream of the second coagulation stage, and $0.037\pm 0.006\mathrm{mg}/\mathrm{L}$ for As(III) with pH adjustment downstream of it. The two-stage process was shown to achieve optimum performance at colder operating temperatures (i.e., 3 versus 23°C).

Steel slag, a by-product of the steel-making industry, after it is aged, has a huge potential for use as a replacement of natural aggregates in highway construction. However, the high pH of leachates from aged steel slags is a major impediment for its beneficial use. This study hypothesized that minimizing hydration of CaO-containing mineral phases in slag can reduce leachate alkalinity. Treatment methods that include coating steel slag with bitumen, bathing steel slag in either Fe(III), Al(III), or ${\mathrm{PO}}_4(\text{-}\mathrm{III})$, and mixing steel slag with an alum-based drinking water treatment residual (WTR) were designed and evaluated based on reduction in Ca release, pH, and alkalinity in the leachate of treated steel slag samples. According to batch-type 18-h water leach test results, bitumen coating (4% of dry weight) and ${\mathrm{Al}}_2({\mathrm{SO}}_4{)}_3$ passivation (0.05–0.10 M as Al) were able to reduce Ca release 50–70% and the levels of alkalinity mitigation were proportional to the reductions in Ca release. WTR addition provided the most successful treatment method; 84% of the Ca release and 71% of the original slag alkalinity were reduced upon WTR addition as low as 10% by dry weight; leachate pH reduced by approximately 1 unit.

The electrochemical oxidation of phenol was studied using a $\mathrm{Ti}/{\mathrm{PbO}}_2$ electrode prepared by the electrodeposition method with ${\mathrm{PbO}}_2$ coated on Ti. The structural and morphological activity of $\mathrm{Ti}/{\mathrm{PbO}}_2$ was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and intermediates formed after degradation of phenol were quantitatively assessed by high-pressure liquid chromatography (HPLC). Optimization of various parameters such as current density, initial phenol concentration, initial solution pH, and different temperature and dose of ${\mathrm{Fe}}^{2+}$ on electrochemical degradation of phenol using ${\mathrm{Ti}/\mathrm{PbO}}_2$ were investigated. Complete removal of phenol ($250{\mathrm{mgL}}^{-1}$) was observed at 50°C, potential difference (5 V), and at pH 2. Experimental results showed that the phenol removal rate increased with increasing current intensity along with significant reduction in total organic carbon (TOC). Fundamental kinetic data obtained for the degradation of phenol by ${\mathrm{Ti}/\mathrm{PbO}}_2$ was found to follow in accordance with the zero-order kinetics with respect to the phenol concentration. This paper is expected to be useful for the development of electrochemical process using ${\mathrm{Ti}/\mathrm{PbO}}_2$ for the degradation of phenol containing wastewater.

This study compared the roles of different reactive oxygen species (ROS) in the photodegradation of cationic dye methylene blue (MB) and anionic dye orange II (OII) by the ${\mathrm{TiO}}_2/\text{ultraviolet}$ (UV) system using different radical quenchers to elucidate the oxidation mechanisms for cationic and anionic dyes. In this study, the holes and surficial $\mathrm{HO}•$ rather than $\mathrm{HO}•$ in the bulk solution were found to play the dominant role in the photodegradation of the two types of dyes, accounting for 60% of the total degradation (the remaining 40% degradation could be contributed by ${\mathrm{O}}_2^{•-}$, ${{}^1\mathrm{O}}_2$, and the UV photolysis). Interestingly, potassium iodide (KI) as the scavenger for surficial radicals could inhibit the OII degradation but enhanced the MB degradation, probably due to the formation of oxidized products such as ${\mathrm{I}}_2$ or ${\mathrm{IO}}_3^{-}$ that could react with MB. ${\mathrm{O}}_2^{•-}$ played a more contributing role in the photodegradation of OII than MB, whereas ${{}^1\mathrm{O}}_2$ exhibited the same contribution to the photodegradation of OII and MB. The results suggested that the photocatalytic reaction mechanisms for cationic and anionic dyes may vary with the types of ROS generated in the ${\mathrm{TiO}}_2/\mathrm{UV}$ system.

Electrochemical method is a promising technology for biorefractory organic wastewater treatment. In this study, commercial available electrode materials, $\mathrm{Ti}/{\mathrm{IrO}}_2$ and Cu/Zn, were used as anode and cathode, respectively, to treat ${\mathrm{CHCl}}_3$-contaminated water. The performance was investigated through cyclic voltammetry and paired electrolysis in an undivided cell. The voltammetric data revealed that the Cu/Zn cathode exhibited good electrocatalytic activity toward ${\mathrm{CHCl}}_3$ reduction. By contrast, no direct oxidation of ${\mathrm{CHCl}}_3$ was observed at the $\mathrm{Ti}/{\mathrm{IrO}}_2$ anode. The reduction of ${\mathrm{CHCl}}_3$ at the Cu/Zn cathode took place through a three-step consecutive hydrodechlorination mechanism. During the paired electrolysis with current density of $15\mathrm{mA}/{\mathrm{cm}}^2$, the chemical oxygen demand (COD) of ${\mathrm{CHCl}}_3$ solution was decreased from 194 to $74\mathrm{mg}/\mathrm{L}$ within 300 min with an energy consumption of $28.6\mathrm{kWh}·{\mathrm{L}}^{-1}$. A mild acidic environment (pH 4.6) was shown to be more favorable to ${\mathrm{CHCl}}_3$ abatement. Decreasing the anode/cathode surface area ratio also had significant impact on ${\mathrm{CHCl}}_3$ reduction, and the optimal ratio was 2.0. The results demonstrated that Cu/Zn cathode is a potential candidate for chlorinated organic compound removal.

Phosphate, a key nutrient for bacterial growth, is also a key component of many corrosion-control programs to manage lead and copper corrosion in premise plumbing. Bench-scale stagnant water galvanic macrocells with lead and copper components were fed with drinking water containing three levels of zinc orthophosphate [0 (control), 1, and $3\mathrm{mg}{\mathrm{l}}^{-1}\text{-}{\mathrm{PO}}_4$]. Suspended polycarbonate coupons, representing benign downstream fixtures, were placed in the macrocells, thus enabling biofilm formation on this material. Community profiling using denaturing gradient gel electrophoresis (16S rDNA PCR-DGGE) revealed that phosphate dose (primarily) and metal type (to a lesser extent) influenced biofilm community diversity. Generally, community diversity increased with increasing heterotrophic plate counts that in turn rose in response to elevated phosphate. Partial 16s rDNA sequences obtained from DGGE gel bands identified the dominant bacterial taxa as the phyla Verrumicrobia, Firmicutes, Bacteroidetes, and $\alpha$-Proteobacteria. The increase in size and diversity of biofilm communities as a result of phosphate treatment further highlights the challenges of a phosphate corrosion-control program.

Hydrological behavior of pervious pavements during rainfall events is a complex process that is affected by many factors such as surface type, nature of aggregates, layer thickness, rainfall height, rainfall intensity, and the preceding dry period. In order to determine the influence of construction materials on the runoff attenuation capacity of pervious pavements, 16 laboratory models were created with four different cross sections obtained by combining two pervious surfaces and two subbase aggregate materials. Successive rainfall simulations were applied over the laboratory models, measuring lag times, retained rainfalls, and times to peak, and peak outflows were registered for the simulated rainfalls. The results obtained were grouped depending on the materials used and statistically analyzed in order to compare their stormwater retention and runoff attenuation capacities. Both surface type and subbase aggregate characteristics were proven to influence the attenuation capacity of pervious pavements. While subbase aggregate materials highly influence the hydrological performance during the first rainfall simulations, the permeable surface affects the hydrological behavior during the final rainfall events and the retention capacity variation over time.

Cocopeat, a by-product of coconut processing plants widely available in Vietnam, Thailand, Cambodia, the Philippines, and Indonesia, was studied for its ability to support biological nutrient removal in lab-scale vertical flow columns treating simulated wastewater. Treatment performance for cocopeat was compared to sphagnum peat, a traditional packing medium, and Celite, an inert clay pellet. Removal efficiencies of nitrogen, phosphorus, and biological oxygen demand (BOD) were measured over a period of 325 days. During the treatment period, varying configurations were tested to determine the effect of varying aerobic, anoxic, and anaerobic zones on nutrient removal. Overall, similar BOD removal profiles were obtained for cocopeat and sphagnum peat. Slightly more efficient anoxic conditions and a less acidic environment developed with the cocopeat. Up to 75% nitrogen removal was obtained; however, phosphorus removal was not accomplished using the experimental setup, likely due to the absence of a completely anaerobic treatment zone. Overall, cocopeat appears to be a promising alternative packing material for on-site wastewater treatment in Southeast Asia in terms of nitrogen removal.

Cocopeat, a byproduct of coconut processing, was evaluated as a packing medium in vertical flow constructed wetlands for the treatment of septic tank effluent in the Mekong Delta of Vietnam. Vertical flow constructed wetlands are typically packed with gravel and then planted with ornamental plants. For this study, varying percentages of cocopeat were added to the gravel and the systems assessed for supplemental treatment efficiency. A secondary treatment step of gravel planters with ornamental plants was assessed for supplemental treatment efficiency. Removal efficiencies of nitrogen, phosphorus, coliform, and biological oxygen demand were measured. Microbial community samples were collected periodically in order to chronologically analyze community shifts within and between different wetland cells. Ammonium transformation and removal was greater than 95% in each wetland containing cocopeat throughout the course of the study. Ammonium concentrations were significantly higher in the effluent of the wetland without cocopeat, indicating reduced nitrification activity, suggesting that cocopeat was critical for supporting nitrification. At steady state, each wetland had significantly lower phosphate concentrations than the influent. Complete removal of ammonium or phosphate in the constructed wetlands was not achieved; however, a secondary treatment step consisting of ornamental planters provided additional removal. This field study suggests that cocopeat is an adequate packing medium for constructed wetlands treating wastewater in Southeast Asia.

Municipal stormwater retention ponds are a means of managing stormwater in urban settings. Numerous contaminants collect in stormwater retention ponds, creating problems such as odor. Because of the complex and variable nature of stormwater quality, a comprehensive study involving both a field study and a laboratory study were accomplished. These two components used a multidisciplinary approach, focused on both water chemistry and microbiological methods to analyze the existing conditions that encourage sulfide production. The field study compared two stormwater retention ponds in terms of water quality and sediment microbial communities in Edmonton, Canada to determine methods to reduce sulfate levels, which are believed to stimulate generation of the toxic hydrogen sulfide. The field study comparison was followed by laboratory studies focused on methods of suppressing sulfide production. Nitrate amendments were found to be effective in suppressing sulfate production; however, the addition of a carbon source stimulated greater sulfide production.

Urban storm runoff is one of the significant sources of surface and groundwater pollution in metropolitan areas. The purpose of this research is to evaluate the performance of porous concrete containing iron slag with sand filter to control urban storm-runoff pollution. Treatments of porous concrete containing iron slag in presence and absence of a sand filter were studied and compared. Parameters of chemical oxygen demand (COD), turbidity, concentration of lead, electrical conductivity (EC), total suspended solids (TSS), and pH in treatment media influent and effluent were measured. The results show that except for EC and pH, the porous concrete containing iron slag with a sand filter significantly improved all of these stated parameters. While the removal efficiency of control porous concrete with a sand filter for COD, turbidity, lead ($\mathrm{initial}=2\mathrm{mg}/\mathrm{L}$), lead ($\mathrm{initial}=5\mathrm{mg}/\mathrm{L}$), and TSS was at 11, 38, 44, 42, and 53%, respectively, these rates increased to more than 43, 91, 91, 95, and 70% for porous concrete containing iron slag with a sand filter. The use of porous concrete containing iron slag with a sand filter is suggested in urban areas affected by stormwater in order to reduce surface-water and groundwater pollution.

Groundwater contaminant transport modeling is basically performed to predict contaminant concentration and to understand the biochemical and physical processes that happen in the subsurface of porous media. Modelers have been faced with the challenge of accurately modeling the behavior and fate of contaminants in groundwater with models and techniques that incorporate the appropriate noise statistics and estimates the hydrogeologic parameters effectively. Unaccounted noise and uncertainties in the modeling greatly affect the accuracy of these predictions. In this paper, two Monte Carlo-based techniques, particle filter (PF) and Ensemble Kalman filter (EnKF), were applied to a three-dimensional (3D) groundwater contaminant transport model to accurately estimate the first-order decay rate and contaminant concentration at each time step. The PF and EnKF are embedded with Sampling Importance Resampling (SIR) and Singular Value Decomposition (SVD) concepts to avoid degeneracy and matrix singularity, respectively. The simulation is performed with a specified domain space and with ensembles and particles size of 50 for parameter estimation and concentration prediction. A set of sparse observation points selected at specific locations were used to update the predictions from the filter at each time step. An analytical solution is generated as true solution to test the accuracy of the predicted values. Algorithms to generate the simulation results were run. The first-order decay rate estimated using PF and EnKF all converged at $0.041/\mathrm{day}$, which matches the actual decay rate. The performance and accuracy of the numerical method, PF, and EnKF were tested using Mean Absolute Error (MAE) and Maximum Absolute Error ($E_{\text{max}}$) equations. The results show that the EnKF performs better than both the PF and the numerical method. Also, the EnKF is capable of reducing the error in the numerical solution by approximately 85%. The R-square adjusted values for the numerical solution, PF, and EnKF were 55, 91.2, and 97.3%, respectively. This statistical value further confirms that EnKF approach performs better than PF.

The treatment by adsorption on activated carbon, ozonation, and ozone/activated carbon coupling of a solution containing six pharmaceutical compounds (metoprolol, carbamazepine, terbutaline, fluoxetine, and sulfamethoxazole) chosen among different pharmaceutical classes has been investigated. The efficiency of the processes was estimated through the removal of each target pollutant and the evolution of both toxicity (inhibition of Vibrio fisheri bioluminescence) and the total organic carbon concentration. The influence of pH, ranging from 3 to 7, on the process efficiency was also studied. In each experimental condition, the fastest removal of the pharmaceutical compounds was achieved with ozone/activated carbon coupling. Nevertheless, this process (ozonation and ozone/activated carbon coupling) leads to the formation of toxic by-products that significantly increase the toxicity of the treated effluent. Their removal would require extending the treatment time or increasing the ozone concentration, which increases the treatment costs. Based on the experimental results in these experimental conditions and the toxicity evolution in the liquid phase, the adsorption on activated carbon seems to be the most efficient and the safest process to remove pharmaceutical compounds from water.

Anaerobic passive treatment systems remediating high-strength mine-impacted water (MIW) have not displayed consistent success. For example, the high iron ($140\mathrm{mg}/\mathrm{L}$) and acidity ($380\mathrm{mg}/\mathrm{L}$ as ${\mathrm{CaCO}}_3$) of the Klondike-1 discharge near Ashville, Pennsylvania, caused premature clogging of a vertical flow pond (VFP), which was filled with a traditional 90% spent mushroom compost (SMC) and 10% limestone substrate. In this study, continuous-flow columns were designed to simulate VFPs with a hydraulic residence time of 16 h to evaluate if the treatment of high-strength MIW can be improved using crab shell as a substrate amendment. Columns containing between 50 and 100% crab shell (with the balance SMC) were compared with a column containing the traditional substrate as well as to a sand control. Water from the Klondike-1 site was pumped through the columns continuously for 181 days and effluent samples were analyzed for pH, oxidation-reduction potential (ORP), ammonia, acidity, alkalinity, dissolved organic carbon, anions, and metals. An additional passive aeration step after substrate treatment was included to simulate the settling ponds typically used in practice so that the full extent of metals removal under these substrate conditions could be evaluated. An optimal substrate ratio of 70% crab shell $+30\%$ SMC treated double the volume of MIW, removed more than twice the mass of metals, and sustained the pH above 5.0 for almost twice as long as the traditional substrate. A treatment efficiency of 1.2 g substrate per liter MIW was calculated as a design parameter for field-scale systems, compared with 2.3 g per liter for the traditional substrate. Although more expensive than traditional substrates ($\sim 50\%$ more expensive for the 70% crab shell mixture), the efficiency of the crab shell amendment enables a 50% reduction in the areal footprint of the VFP and is significantly (two times) less expensive than active treatment alternatives.

The decomposition behavior of lignocellulosic materials is related to the taxonomic classes of the parent plant tissues. Thus, methods to characterize the composition of mixtures of lignocellulosic materials such as municipal solid waste (MSW) according to different taxonomic classes of plants are useful. The copper oxide (CuO) oxidation products of lignin provide molecular markers that allow for characterization of the initial plants. The objective of this study was to determine if the chemical composition of the monomers present after CuO oxidation can be used to infer information on the content of woody angiosperms (hardwood—HW), non-woody angiosperms (leaves and grasses—LG), woody gymnosperms (softwood—SW), and non-woody gymnosperms (needles—GN). Results showed that the composition of HW and SW in synthetic mixtures can be estimated from CuO oxidation products of lignin within an error of $\pm 60\%$ of the expected values. The high uncertainty in the estimate of composition in synthetic mixtures can be attributed to the fact that the components selected for the synthetic mixtures had different CuO oxidation products compared to the average which was used in developing the mixing model. Application of the mixing model to estimate the composition of samples from a Kentucky (KY) landfill showed that the majority of the samples are from HW and SW with little to no non-woody tissues (LG, GN). However, the mixing model is not sufficiently precise to infer more detailed information on MSW composition.

The use of chlorine dioxide (${\mathrm{ClO}}_2$) instead of free chlorine (${\mathrm{Cl}}_2$) as a preoxidant is an effective option for reducing disinfection byproducts (DBPs) and enhancing coagulation in water treatment plants (WTPs). This study takes a first look at water quality and bacterial community responses within a WTP when switching preoxidants between ${\mathrm{Cl}}_2$ and ${\mathrm{ClO}}_2$. Water samples and biofilm coupons inserted in the sedimentation basin were collected during the change between ${\mathrm{ClO}}_2$ and ${\mathrm{Cl}}_2$ in a local WTP. Biofilm density and bacteria viability significantly decreased in response to the preoxidant change. Molecular methods confirmed the switch to ${\mathrm{Cl}}_2$ oxidation that decreased the diversity index for both biofilms and basin waters. Range weighted richness calculations reveal that changing the preoxidant results in a more adverse environment for bacterial growth, compared to maintaining one preoxidant over time. The insights provided regarding microbial growth and diversity under differing oxidants offer a unique perspective in water treatment that warrants further examination.

This paper presents the results from amending eucalyptus wood char with the following metal salts: aluminum sulfate, aluminum chloride, iron (II) chloride, and iron (III) nitrate. The results show that amending wood char with metal salts, which precipitate from the solution as metal oxides and amend the char surfaces, increases the ability of the wood char to remove fluoride from drinking water. Wood char alone has a $Q_{e1.5}$ value of $0.04\mathrm{mg}/\mathrm{g}$, whereas the $Q_{e1.5}$ values of the metal-amended wood chars range from 0.14 to $2.06\mathrm{mg}/\mathrm{g}$. Iron oxide amendments resulted in greater improvements in fluoride removal capacity than aluminum oxide amendments, with $Q_{e1.5}$ values of 2.06 and $0.76\mathrm{mg}/\mathrm{g}$ for the iron oxide–amended chars and 0.57 and $0.14\mathrm{mg}/\mathrm{g}$ for the aluminum oxide–amended chars. Pretreating wood char with the oxidizing agents potassium permanganate and hydrogen peroxide increased the metal loading and fluoride removal capacities in select instances. When wood char was pretreated with potassium permanganate and amended with aluminum sulfate, the $Q_{e1.5}$ value increased from 0.14 to $0.40\mathrm{mg}/\mathrm{g}$ and the metal loading increased from 0.05 to 0.27%.

The soils contaminated by copper (Cu) near a mine tailing are remedied via an enhanced electrokinetical (EK) method utilizing approaching anodes (AAs). The variations in the removal efficiency and soil pH as a function of treatment time are determined. The maximum Cu removal efficiency is as high as 61.98% under a voltage gradient of $1\mathrm{V}/\mathrm{cm}$ for 48 h; in contrast to 38.97% when the conventional electrokinetic remediation with one fixed anode (FA) is employed. Several anodes were inserted as AAs in the treated soil. They were switched in turn from the anode towards the cathode allowing for high ${\mathrm{H}}^{+}$ ions concentrations and high redox potentials to quickly migrate towards the cathode. As a result, the soil remediation is accelerated. The mechanism of Cu electromigration behavior in soils during an enhanced EK method is described as the elution in an electrokinetically-driven chromatogram.

A membrane bioreactor (MBR) pilot plant was operated in two subsequent experimental periods (namely, Periods I and II) with different start-up and sludge withdrawal strategies to study its peculiar biokinetic behavior by using respirometric techniques. Two extreme operational conditions were chosen to investigate the different biomass activity under dynamic or pseudostationary conditions during and after the start-up phases. Particularly, the MBR pilot plant was operated with the same volumetric loading rate (VLR) and permeate flux but differently managed during the start-up phase. In Period I, the MBR pilot plant was started up without sludge inoculum and operated without sludge withdrawals; on the contrary, in Period II the MBR pilot plant was started up with sludge inoculum and operated with regular sludge withdrawals. The obtained results highlighted that the different start-up strategies significantly affected the value of the yield coefficient, the storage phenomena, the decay coefficient, and the maximum respiration rates of heterotrophic species. More specifically, both experimental periods underlined interesting aspects related to the bacterial behavior under significant stress conditions occurring during a non-steady-state (start-up) phase.