Journal of Environmental Engineering

Transient loading of vapor-phase biofilters may result in exceedence of the local reaction or mass transfer capacity of the inlet region. In such cases, higher concentrations of contaminants are carried deeper into the bed where there is less active biomass and, in some cases, breakthrough of contaminants may occur. Previous studies have demonstrated that periodic reversal of the flow direction results in improved transient-loading response. However, quantitative information on the extent of the benefit is lacking. Step function increases in toluene concentration were applied to unidirectional-flow and flow-direction-switching laboratory reactors operated in parallel. Contaminant concentration was monitored at several points along the packed beds. Relative to unidirectional mode of operation, periodic flow reversal produced a more uniform distribution of microbial reaction capacity along the length of the packed bed. Directional switching at a $12\text{-}\mathrm{h}$ interval did not result in a loss of activity or removal capacity. Mass-removal rates under transient-loading conditions were similar in the first-half of both biofilters but, in the second-half of the units, significant removals were observed only in the flow-direction-switching biofilter. As a result, maximum mass-removal rates under transient-loading conditions were approximately twice as great for the flow-direction-switching biofilter relative to the conventional unidirectional-flow biofilter receiving similar mass loading.

The resistance of reovirus to inactivation by mesophillic and thermophillic temperatures was investigated and compared to existing inactivation patterns for poliovirus, the most commonly used enteric virus indicator. The resistance of reovirus to alkaline condition resulting from the addition of lime (CaO) to biosolids was also examined. Phase one involved the incubation of reovirus in a buffered solution for a $28\text{-}\text{day}$ period at different temperatures ranging from $4\text{to}50°\mathrm{C}$ . This phase also involved reovirus incubation at thermophillic temperatures ranging from $50\text{to}55°\mathrm{C}$ for a $30\text{-}\min$ period. The second phase looked at reovirus survival in biosolids mixed with lime doses ranging from $0\text{to}100\mathrm{g}$ lime per kg dry biosolids over a $23\text{-}\text{day}$ period. Reovirus was more resistant to inactivation caused by long-term storage under mesophillic temperature conditions than poliovirus. Reovirus also was more resistant to inactivation caused by short-term storage under thermophillic temperature conditions than poliovirus. Reovirus has shown to be stable in biosolids under naturally occurring environmental conditions for up to $1\text{year}$ , while doses of $80\mathrm{g}$ lime per kg dry biosolids and greater were able to meet class A levels for enteric viruses after $1\text{day}$ of storage.

The paper demonstrates an intensive work carried out and results obtained on the pilot plant of the City of Kogalym Water Treatment Station (Tjumen, Siberia, Russian Federation) to elaborate on a contemporary nonreagent treatment technology for the local iron-rich groundwater. Several filter materials (Birm, Pyrolox, hydroanthracite, Everzit, granulated activated carbon) and chemical oxidants (ozone, chlorine, hydrogen peroxide, oxygen, and potassium permanganate) were tested to solve the problem with complexed iron removal from groundwater. The final elaborated technology consists of raw water intensive aeration in the gas-degas treatment unit followed by sequential filtration through hydroanthracite and the special anthracite Everzit.

The main objective of the present study is to develop a modified membrane bioreactor (MBR) system for the treatment of municipal wastewater for the enhanced biological removal of nitrogen (N) and phosphorus (P) simultaneously with the ultimate goal of optimizing the two processes. The paper will address the implementation and optimization of the MBR process with respect to biological characteristics, operational performance, and effluent quality. The system utilizes anoxic P uptake and nitrification–denitrification in a MBR. Following optimization, the system achieved 99% chemical oxygen demand (COD), 98.4% ${\mathrm{NH}}_3–\mathrm{N}$ , 77.5% TN, and 96.3% P removal producing effluent biological oxygen demand, COD, ${\mathrm{NH}}_3–\mathrm{N},{\mathrm{NO}}_3–\mathrm{N},{\mathrm{NO}}_2–\mathrm{N}$ , and P of $<3$ , 3, 0.4, 5.8, 0.050, and $0.18\mathrm{mg}∕\mathrm{L}$ , respectively.

High-rate anaerobic treatment systems are becoming increasingly popular to treat industrial wastewater containing large amounts of organic matter in the form of carbohydrates or proteins. Mathematical models of these systems can serve as tools for equipment sizing, process design, control and optimization, plant operation, and operator training. Several models for these plants have been proposed which have been validated and tested on laboratory-scale systems. Information on full-scale application of these models is not readily available. In this paper, a model only previously validated on laboratory scale was applied at full scale. The model was used to predict the behavior of two full-scale plants of different designs treating brewery wastewater under dynamic conditions. Influent and effluent liquid streams and gas flows were sampled over a 4 and 10 day period for the two plants, respectively. Limited characterization to just total carbon in feed over only four days was sufficient to predict the gas production rate or total volatile organic acid concentration in the effluent of the methanogenic reactor. Elaborate measurements over 10 days of feed characteristics including organic acid concentrations were important in obtaining good full-scale predictions of all variables that were modeled. Apart from the operating variables, the key parameter that required re-estimation for the full-scale system was the solids retention time in the methanogenic stage.

Anaerobic treatability of two different wastes that represent the main refuse streams generated by a frozen food factory (fresh vegetable waste and precooked food waste) was assessed. Moreover, the sludge coming from agro-industrial wastewater treatment was codigested with the previously mentioned wastes. Batch tests were performed at different solids content both on the single wastes and on appropriate mixtures of them (also in order to simulate the seasonality of factory production). Both fresh vegetable and precooked food wastes strongly inhibited methanogenesis from unacclimated inoculum at 10% solids content (undiluted waste) and 5% solids content (eight- to nine-fold diluted waste), respectively. This was due to their high contents of potassium and lipids, respectively. The aerobic sludge from the wastewater treatment plant did not exert inhibitory effect up to 10% solids content (undiluted waste). Codigestion of the fresh vegetable waste and sludge (60 and 40% on wet basis) was more effective both in terms of rate and yield of methane production with respect to the single wastes (due to dilution and synergic effects). On the other hand, methanogenesis remained strongly inhibited from mixtures containing pre-cooked food waste (at 25 and 45%, on wet basis). Methanogenesis inhibition could be overcome by a long acclimation period. The results showed that fill-and-draw digestion in a 0.5 L lab-scale reactor of the fresh vegetable waste and sludge mixture after start up with acclimated inoculum allowed higher methane yields (37% at high organic load and 57% at low organic load). Better results were obtained in a 1.7 L micropilot fill-and-draw reactor (yield of 67%) fed at higher frequency.

A nitrifying biomass was produced from anaerobic sludge dewatering liquors for the purpose of bioaugmentation of sequencing batch reactors (SBRs). Nitrification of centrate was conducted at four temperatures (10, 20, 25, and 30°C) while the seeded SBRs were operated at 10°C with a solids retention time of approximately 4 days. The SBRs did not exhibit any nitrification before the onset of seeding. When the hydraulic retention time (HRT) was 24 h, partial removal of ${\mathrm{NH}}_3–\mathrm{N}$ occurred when seed acclimated to 20, 25, and 30°C was added. When the HRT was 12 h, only the SBR seeded with nitrifying biomass acclimated to 10°C achieved 50% ${\mathrm{NH}}_3–\mathrm{N}$ removal. Complete removal of ${\mathrm{NH}}_3–\mathrm{N}$ was not achieved in any of the seeded SBRs. The degree of ${\mathrm{NH}}_3–\mathrm{N}$ removal in the seeded SBRs was dependent on the initial temperature of the seed, and the observed growth rates of the nitrifying bacteria were inversely proportional to the change in temperature.

A clayey soil contaminated with pyrite was treated with the addition of a base in laboratory experiments. The subsequent rise in pH is an efficient mechanism to retain the metals released by the sulfide weathering. Iron concentrations decrease as pH increases owing to the formation of secondary hydroxide phases, such as ferrihydrite. Aluminum and the aqueous divalent metals, such as Cu, Zn, Ni, Co, Cd, and Mn also decrease in concentration as pH increases. The fall in concentration can be accounted for by the formation of complexes on the surface of illite, which forms about 20 wt % of the soil. Given the proportion of illite and the thickness of clayey soils in the Aznalcóllar region, the addition of a base such as lime or lime-containing flying ash could be an efficient remediation process. By contrast, the addition of more efficient exchangers such as zeolite continues to be recommended for sandy soils and gravels from the area with low clay contents.

A physically based, one-dimensional, mathematical model is developed to simulate transport of herbicides applied to roadsides into adjacent surface water. Herbicide transport by overland flow, infiltrating water, and subsurface flow is considered. The model accounts for advection, dispersion, equilibrium linear sorption in the soil, and first-order decay of the herbicides. Chemical transport between soil and overland flow is described using a rate-limited mass exchange between the two compartments that is proportional to the difference between the chemical concentration in overland flow and the pore water with a proportionality constant that is a function of overland flow characteristics and rain intensity. For simulating overland and subsurface flow, the kinematic wave equation is solved using a Crank–Nicolson finite difference scheme. Richards’ equation is solved using a Galerkin finite element method to model infiltration, and the transport equation is solved using a finite difference method. The model is calibrated and verified using extensive field data on the runoff of five herbicides with a range of physical–chemical properties at two field sites. Good agreement is obtained between predicted and measured event-mean concentrations in runoff and the herbicide concentration remaining in the application-zone soil.

The objective of this study is to investigate the effect of organic cosolvents on the extractability of hydrophobic organic compounds (HOCs) from soils after defined aging periods following HOC contamination. Phenanthrene was used as the representative HOC. Two soils with organic matter contents 2.9 and 6.5%, respectively, were investigated. The soils were spiked with phenanthrene, then saturated in water or mixtures of water and methanol, and aged for up to 422 days. After freeze drying, the extent of phenanthrene release was measured using a mild extraction process. The results show that as aging period increases, phenanthrene removal from the soils becomes more difficult. The amount of easily extractable phenanthrene tended to increase when more methanol existed in the pore fluid during aging, but the difference largely diminished after about 400 days. At the early stage of aging, extraction of phenanthrene from the soil with lower organic matter content tended to be less difficult compared with that from the soil containing more organic matter. The opposite appeared to be true when the aging time was longer than 200 days. From the results, we propose that a shift in the predominant sequestration mechanisms occurred after a certain period of time, in which hydrophobic interactions between HOCs and organic matter gradually yield to physical trapping of the sorbate molecule in the meso- and micropores of the soil particles.

In order to implement efficient and effective management strategies for coastal water quality in Southern California, it is important to consider the relative pollutant contributions from urban dry-weather flow (DWF) and wet-weather flow (WWF). This study uses both historical flow coupled with water quality monitoring data and computer modeling to characterize the annual DWF and WWF discharges from an urban catchment in Los Angeles, Calif. The DWF and WWF pollutant loading of the trace metals copper, lead, nickel, and chromium for 6 water years dating from 1991 to 1996 is predicted. The results indicate that DWF contributes a considerable amount of flow and pollutants. Approximately, 9–25% of the total annual Ballona Creek flow volume is DWF. The simulations indicate DWF accounts for 54, 19, 33, and 44% of the average annual load of total chromium, copper, lead, and nickel, respectively. In the dry season, the simulations indicate DWF accounts for 89, 59, 58, and 90% of the load of total chromium, copper, lead, and nickel, respectively. This research suggests DWF controls may be an important part of pollution mitigation plans for urban stormwater drainage systems in Southern California.

A theoretical model is introduced for describing the mechanistic and probabilistic structure of observations of streamflow $Q$ , concentration $C$ , and constituent loads $L$ . The model has application to many water-quality management problems including load estimation, water-quality monitoring network design and total maximum daily load assessment. The statistical behavior of streamflow, concentration, and load is described and expressions are derived for the coefficient of variation of daily concentrations and loads assuming a bivariate lognormal model. The model provides a first-order approximation to continuous empirical observations of $C$ , $Q$ , and $L$ from four watersheds in the Great Lakes Region. The utility of the model is demonstrated by quantifying the amount of “spurious” correlation between load and discharge, by documenting factors which influence bias in water-quality load estimates and those which give rise to increased/decreased variability in water-quality loads and concentrations.

Infiltration basins are frequently used for stormwater drainage. They can operate for periods over 20 years but long-term evolution is not well understood or controlled. The two main problems encountered are clogging, which compromises the hydraulic capacity of the basin, and possible contamination of underlying soil and groundwater. This paper focuses on studying long-term evolution of clogging and soil pollution of infiltration basins. Basins of different ages are compared. Also, clogging and soil pollutant concentrations are explored for four infiltration basins in Lyon, France. Ages of the sites range from 10 to 21 years old. Clogging is characterized by the hydraulic resistance. Soil samples were collected at different depths in each basin and analyzed for different pollution parameters (metals, hydrocarbons, pH, and particle size distribution). All four basins have good infiltration capacities. Their hydraulic resistance is low. Such uniformity is surprising because of the age difference between the basins. Pollutant concentrations decrease rapidly with depth whereas pH and grain size increase. Concentrations reach an acceptable value at a 30 cm depth, even after 21 years of operation. Multivariate data analysis does not show significant relation between age, hydraulic resistance, and pollution.

The velocity and pressure fields of the flow over street canyons formed by groups of buildings are studied numerically. The flow fields are computed by solving the time-dependent incompressible Navier–Stokes equations using the fractional step method. The numerical model is validated by simulating flows over a square cylinder at different Reynolds numbers. The Strouhal numbers, which reflect the dynamic flow characteristics, agree well with published experimental data over a wide range of Reynolds numbers. The wind field model is then applied to two street canyon configurations. First, flows inside street canyons formed by four identical buildings are simulated. The incidental flow is raised by the most upstream building and becomes parallel to the ground at the rooftop level of the fourth building downstream, resulting in a clockwise rotating vortex in downstream street canyons with an inflow from left to right. Second, flows inside street canyons formed by two identical buildings are simulated. In this case, a primary eddy that is counterclockwise rotating may be formed due to flow separation at the front corner of the upstream building. A clockwise rotating primary eddy is formed in the wake area of the separate zone above the street canyon, which drives the counterclockwise rotating eddy in the street canyon. The result indicates that rooftop level flows cannot be assumed parallel to the ground as some modelers have done in their studies. Studies also show that flow regimes in the street canyon will remain unchanged while the inflow velocity is greatly increased from 0.1 to $6.0\mathrm{m}∕\mathrm{s}$ . In addition, the wind velocities in the street canyon have a linear response to the inflow velocity.

Waste disposal problems are often the result of rapid industrial and economic developments in land-scarce municipalities. Waste utilization could be a viable choice to alleviate the problems by transforming wastes into useful products while conserving natural resources. Previous studies by the writers indicated that in the process of thermal conversion of industrial sludge and dredged marine clay mixes into concrete aggregates, pyro-expansion and bloating were often exhibited by the aggregates. The expansion and bloating mechanisms, however, have not been looked into in greater detail. This research examines the petrology of sintered industrial sludge–marine clay aggregates in order to better understand the mechanisms leading to pyro-expansion and bloating of the aggregates. The study would enable development of an efficient and cost-effective bloating methodology for lightweight aggregate production. Main factors investigated were sludge–clay mix proportions, firing temperatures, and salt additives. The investigation revealed that firing at temperatures of 1,200 and $\mathrm{1,300}°\mathrm{C}$ produced aggregates of lower specific gravity in the range of 0.5–1.6. The highest aggregate porosity can be achieved at $\mathrm{1,200}°\mathrm{C}$ with a clay content of 50%. Scanning electron microscope images indicated that the intrinsic lightweight characteristic of the aggregates could be attributed to large pores within a dense surrounding matrix. The effect of lightweight structures may be ascribed to the release of volatile substances at each respective peak endothermic transitions during firing. The release of substances in vapor form required a large amount of energy, which resulted in the peak endothermic transitions that correspond to the formation of the porous lightweight structures. The results suggested that it is possible to promote pores formation in the production of aggregates possessing lightweight characteristics through careful control of temperature and the selection of sludge–clay proportion.

Destruction of a dense nonaqueous phase liquid (DNAPL) by soluble iron (III)-catalyzed and pyrolusite $\left(\beta \text{-}{\mathrm{MnO}}_2\right)$ -catalyzed Fenton’s reactions (hydrogen peroxide and transition metal catalysts) was investigated using carbon tetrachloride (CT) as a model contaminant. In the system amended with 5 mM soluble iron (III), 24% of the CT DNAPL was destroyed after 3 h while CT dissolution in parallel fill-and-draw systems was minimal, indicating that CT was degraded more rapidly than it dissolved into the aqueous phase. Fenton’s reactions catalyzed by the naturally occurring manganese oxide pyrolusite were even more effective in destroying CT DNAPLs, with 53% degradation after 3 h. Although Fenton’s reactions are characterized by hydroxyl radical generation, carbon tetrachloride is unreactive with hydroxyl radicals; therefore, a transient oxygen species other than hydroxyl radicals formed through Fenton’s propagation reactions was likely responsible for CT destruction. These results demonstrate that Fenton-like reactions in which nonhydroxyl radical species are generated may provide an effective method for the in situ treatment of DNAPLs.