Journal of Environmental Engineering

Phosphate concentration microprofiles were measured within activated sludge flocs in the enhanced biological phosphate removal (EBPR) process, and a fluorescent in situ hybridization and clone library analysis were conducted to indentify polyphosphate accumulating organisms (PAOs). The center of the flocs had the highest phosphate concentrations, and the stratification of the flocs found by microprofiling indicated that the PAOs were probably distributed evenly throughout the flocs. Under the assumption that the phosphate, which was generated because of phosphate release by microbial activity, was not consumed by microbes and was only transferred from the flocs to the bulk by diffusion during anaerobic conditions, the effective diffusion coefficient $\left(D_f\right)$ for phosphate release within the flocs was calculated to be $3.33\times {10}^{-7}{\text{cm}}^2/\text{s}$ at the end of the anaerobic phase of the EBPR process. These results provide a better understanding of the phosphate removal mechanism, and this understanding of the internal function of flocs can lead to improvement in the modeling, design, and operation of the biological phosphorus removal process.

Hydrogen $\left({\text{H}}_2\right)$ production was maximized and methane $\left({\text{CH}}_4\right)$ formation was minimized in a mixed anaerobic culture which was maintained at $21°\text{C}$ and fed glucose plus unsaturated long chain fatty acids (LCFAs). The initial pH in the batch reactors was $7.8\pm 0.2$ . The two LCFAs under consideration included linoleic acid (LA) (two $\text{C}\text{C}$ bonds) and oleic acid (OA) (one $\text{C}\text{C}$ bond). Hydrogen production was observed when glucose was injected on Day 0 and again after Day 4. The ${\text{H}}_2$ yield in cultures fed LA was less than those receiving OA. The ${\text{H}}_2$ yield reached a maximum of approximately $1.1\text{mol}{\text{H}}_2{\text{mol}}^{-1}$ glucose when the LA level was $2,000\text{mg}{\text{L}}^{-1}$ . In the case of OA, a maximum yield of $1.3\text{mol}{\text{H}}_2{\text{mol}}^{-1}$ glucose was attained with $2,000\text{mg}{\text{L}}^{-1}$ . The inhibition caused by the addition of LA or OA diverted a fraction of electrons toward proton reduction. Under maximum ${\text{H}}_2$ production conditions in the LA fed cultures the acetate production pathway was repressed, while in cultures fed OA the acetate pathway was dominant. The amount of ${\text{CH}}_4$ produced decreased with increasing ${\text{H}}_2$ production and the major volatile fatty acids detected were acetate, propionate and butyrate. Small quantities of formate were detected only in cultures fed LA after the first glucose injection. As the LCFA concentration increased, the initial glucose degradation rate decreased.

An anaerobic expanded granular sludge bed (EGSB) reactor is considered to be an improvement over upflow anaerobic sludge blanket reactors owing to the former’s ability to recycle the effluent and its modified reactor geometry. However, the mixing pattern in EGSB reactors, which greatly influences the design and the performance of this reactor, has not yet been studied in detail. In this research, the mixing pattern in a lab-scale EGSB reactor treating a synthetic dye wastewater was studied using lithium chloride as a tracer. The tracer exit curve indicated a complete-mix behavior. A simulation study was conducted on identical reactors using conductivity probes, inserted through the sample ports along the height of the reactors and connected to a data acquisition system. The reactors were operated at three different hydraulic retention times (3.3, 5.5, and 9 h) and at four different upflow liquid velocities (1.10, 2.66, 5.33, and 8.68 m/h). The data showed the existence of a plug-flow regime in the basin at lower upflow liquid velocities although the tracer response curves resemble complete-mix behavior. With increasing upflow liquid velocity the flow pattern in the basin deviates from a plug-flow pattern and approaches a complete-mix condition. The EGSB reactor can be modeled as a plug-flow reactor with recycle and dead space, and with a large vessel dispersion number $\left(D/uL>0.01\right)$ .

Pollutants removal from swine wastewater by a submerged biofilm sequencing batch reactor (BSBR) with internal circulation of liquor through a sand filter was studied. The variation of nutrient removal efficiencies with changes in volumetric circulation ratios and rates were determined. The reactor was operated under the following conditions: One cycle per day, hydraulic retention time of 15 days, average ${\text{NH}}_4–\text{N}$ loading rate of $55\text{g}{\text{m}}^{-3}{\text{d}}^{-1}$ , and without supplemental external carbon source. System performance was enhanced by conducting internal circulation of liquor through the sand filter. When compared with the performance of a single BSBR without sand filter, nitrogen and phosphorus removal efficiencies were found to increase by 18% and over 33%, respectively. With a circulation rate of $170\text{L}{\text{h}}^{-1}{\text{m}}^{-3}$ , and duration of 22 h (circulation ratio of 0.9), TOC, ${\text{NH}}_4–\text{N}$ , and total soluble inorganic nitrogen (as ${\text{NH}}_4–\text{N}$ plus ${\text{NO}}_x–\text{N}$ ) removal efficiencies of 73, 97.8, and 85.6%, respectively, were achieved. The enhancement of nitrogen removal was attributed to the occurrence of denitrification in the sand filter during circulation of liquor. The denitrification rate was proportional to the volumetric circulation ratio per day, resulting in an average 15% ${\text{NO}}_x–\text{N}$ removal in the sand filter. Also, it was found that continuous circulation during the entire reaction phases could be one way to achieve better performance.

Modified by ethylenediaminetetraacetic acid (EDTA) salts and unmodified bagasse fibers were tested for the removal of total dissolved solids (TDSs) from cooling tower water. Parameters such as hydrogen ion concentration (pH), particle size of bagasse fibers, and the concentrations of adsorbent and adsorbate were studied to optimize the conditions to be applied on a commercial scale for the decontamination of effluents of cooling tower water. The optimum pH for TDS removal was between 6 and 6.5. The efficiency of TDS removal increased when the size of fiber particles decreased $\left(100\mu \text{m}\right)$ and when the concentration of EDTA salt increased to reach 78 mg/g of modified bagasse fibers. The adsorption parameters were determined using both Langmuir and Freundlich isotherms. The preferential mechanisms for the retention of TDSs are a complexation process between the TDSs and chemical functions present on the surface of fibers, and the chelation process with the EDTA attached to the fibers. The results obtained could be valuable for application to cooling tower water treatment and for the softening of hard drinking water.

The objective of this study was to assess the potential of applying enhanced bioremediation on the treatment of petroleum-hydrocarbon contaminated soils. Microcosm experiments were conducted to determine the optimal biodegradation conditions. The control factors included oxygen content, nutrient addition, addition of commercially available mixed microbial inocula, addition of wood chip and rice husk mixtures (volume $\text{ratio}=1:1$ ) as bulking agents, and addition of organic amendments (chicken manures). Results indicate that the supplement of microbial inocula or chicken manures could significantly increase the microbial populations in soils, and thus enhance the efficiency of total petroleum hydrocarbon (TPH) removal (initial $\text{TPH}=5,500\text{mg}/\text{kg}$ ). The highest first-order TPH decay rate and removal ratio were approximately $0.015{\text{day}}^{-1}$ and 85%, respectively, observed in microcosms containing microbial inocula (mass ratio of soil to $\text{inocula}=50:1$ ), nutrient, and bulking agent (volume ratio of soil to bulking $\text{agent}=10$ to 1) during 155 days of incubation. Results indicate that the first-order TPH decay rates of 0.015 and $0.0142{\text{day}}^{-1}$ can be obtained with the addition of microbial inocula and chicken manures, respectively, compared with the decay rate of $0.0069{\text{day}}^{-1}$ under intrinsic conditions. Thus, chicken manures have the potential to be used as substitutes of commercial microbial inocula. The decay rate and removal ratio can be further enhanced to $0.0196{\text{day}}^{-1}$ and 87%, respectively, with frequent soil shaking and air replacement. Results will be useful in designing an ex situ soil bioremediation systems (e.g., biopile and land farming) for practical application.

Artificial groundwater recharge for drinking water production involves infiltration of surface water through sandy soil and its capture into a groundwater aquifer. The transformation of aqueous organic matter is one of the central issues in this process. The purpose of this work was to assess the potential of indigenous microorganisms in the source water to contribute in the aqueous organic matter biodegradation. For this purpose, microorganisms were enriched from the source water in a fluidized-bed reactor (FBR) and used for kinetic studies on biodegradation of organic matter at ambient temperature range. Lake water (total organic carbon $5.8\text{mg}{\text{L}}^{-1}$ ) was continuously fed to the FBR containing porous carrier material to support biomass retention. In the inlet and outlet water there were on average $21\pm 6$ and $13\pm 5\times {10}^5\text{cells}{\text{mL}}^{-1}$ , respectively. Biofilm accumulation (as volatile solids) reached $13.1\text{mg}{\text{g}}^{-1}$ dw carrier. In the continuous-flow mode and the batch tests, the highest oxygen consumption rate appeared in the summer, followed by the fall, spring, and winter. At low temperatures, the biodegradation of aqueous organic matter was relatively rapid initially for labile fractions followed by a slower phase for refractory fractions. The average temperature coefficient $\left(Q_{10}\right)$ in the system was 2.3 illustrating a strong temperature dependency of oxygen consumption. The isotopic analysis of dissolved inorganic carbon ${\delta }^{13}{\text{C}}_{\text{DIC}}$ analysis revealed 27 and 69% mineralizations of dissolved organic carbon at 23 and $6°\text{C}$ over 65 and 630 min, respectively. These results can be used to construct additional input parameters in modeling applications of artificial groundwater recharge process. The biological component especially, i.e., the biodegradation, is difficult to predict for on-site applications without experimental proof and thus the interpretation in this study will help formulate design predictions for the process.

Crab-shell chitin, which is inherently high in calcium carbonate and nutrients, was tested as a multifunctional, fractional amendment to improve the effectiveness of spent mushroom compost (SMC), which is a low-cost, frequently used, but often underperforming substrate for treating acid mine drainage (AMD). Batch and continuous-flow column tests were used to evaluate different crab-shell/SMC mixtures for their ability to neutralize acidity, reduce sulfate, and remove metals in field-collected AMD. Alkalinity generation and the removal of manganese and sulfate were strongly correlated to the fraction of crab shell in the substrate: the treatment capacity increased from 36.7 L/kg for the traditional 90% SMC/10% limestone substrate up to 428 L/kg for 100% crab shell. The costs associated with adding crab shell to SMC were found to be minimal relative to the resulting improvement in water quality. Based on these data, it appears that a small fraction of crab shell (5–15%) does not provide a significant benefit over traditional compost and limestone substrates, but that larger fractions (50–100%) are much more efficient than traditional SMC substrates, especially for the removal of metals.

In this study, bioassessment data collected between 1998 and 2005 were synthesized and analyzed for streams and rivers throughout the San Diego Hydrologic Region to provide a spatial and temporal context for the results of several monitoring projects conducted between 1998 and 2005 and to ascertain the applicability of the Southern California benthic macroinvertebrate index of biological integrity (SoCal B-IBI) to the region’s streams. The water quality of the sites studied in the region, as reflected by temporal and spatial analyses of SoCal B-IBI scores, was found to be quite poor. When streams were analyzed individually most showed stable scores over the time frame of the study with some showing better scores in the fall. Spatially, scores were found to be better farther away from the coast in the upstream reaches of the watersheds. This study further explored the applicability of the SoCal B-IBI to a focused geographic region by demonstrating the necessity of each component metric to the assignment of biological condition. Although all component metric scores were deemed to be necessary, the percent intolerant individuals score had a more significant effect in driving impairment. The analysis of the component metrics of the SoCal B-IBI provides useful insights to the changes in scores among and between the sampled sites in the region’s watersheds. Based on this study, natural resource management agencies responsible for managing water quality should incorporate regular measures of biological integrity into their water quality programs to ascertain regional and temporal trends.

Aerosol dispersion in living spaces especially bioaerosols, due to accidents or deliberate acts, is of significant current interest. Computational fluid dynamics (CFD) provides an accurate and detailed platform to study the influence of different parameters on aerosol distribution in indoor spaces. The simulations however are time consuming and site-specific. The work here introduces an approach toward addressing this challenge. During emergencies, an accurate, quicker, and more general model is required to give rapid answers to first responders. Significant parameters influencing aerosol behavior in an office room were identified and through dimensional analysis, nine dimensionless groups were developed. Fractional factorial design was used to build sixteen scenarios to explore the design space. These scenarios were then simulated using a comprehensive CFD model. Large eddy simulation with the Smagorinsky subgrid scale model was applied to compute the airflow. Aerosols were modeled as a dispersed solid phase using the Lagrangian treatment. The influence of the dimensionless groups on the temporal variation of the number of aerosols in the room and the spatial distribution of the particles in the room was analyzed. The results showed that all the identified dimensionless groups were significant. Multiple linear regression models were developed for the prediction of the number of aerosols in the room and their spatial distribution as a function of the significant parameters influencing aerosol transport. The linear models accurately predicted the data on which they were based but did not predict the results of the independent tests as well. The limited predictive ability of the model showed that the relationships between the dimensionless groups are nonlinear and a higher level of experimental design will have to be applied to better explore the design space.

A regression curve based on a Weibull distribution model is generated to describe the binodal curve on a three component liquid-liquid ternary phase diagram. The methodology involves transforming the experimental phase partitioning data points of each mixture from the ternary phase diagram to equivalent Cartesian coordinates. The regression curve is then generated, and the regression curve becomes the Weibull-derived binodal curve by superimposing the regression curve onto the original ternary phase diagram. A total of seven regression curves for seven ternary mixtures are generated in this study. From the regression analysis, the resulting $R^2$ value for each mixture is very close to one, indicating that there is strong correlation between the regression curve and the transformed experimental data points. The method developed in this research allows researchers to empirically describe a binodal curve, which is useful in analyzing and predicting the various phase partitioning scenarios of a three-component liquid-liquid system.