Journal of Environmental Engineering

With the growing acceptance of ultraviolet (UV) irradiation for disinfection of water and wastewater, the use of medium pressure Hg-based UV lamps and nonmercury, pulsed UV lamps emitting polychromatic light, are being considered in place of low-pressure, monochromatic UV lamps. However, traditional methods of fluence measurement developed for monochromatic light sources are not appropriate for polychromatic light sources. New approaches for estimation of effective germicidal fluence for polychromatic UV sources were investigated integrating chemical actinometry (uridine and iodide/iodate) with mathematical modeling. Actinometric fluence measurements as well as radiometry were referenced against microbial biodosimetry. Combining traditional chemical actinometry with mathematical analysis improved the accuracy of incident and germicidal polychromatic UV fluence measurement. Uridine actinometer germicidal fluence measurement, with or without mathematical correction, was just outside of the 95% confidence interval of that measured by biodosimetry. Similarly, an iodide/iodate actinometer was observed to accurately measure incident fluence, and coupled with mathematical corrections, it measured germicidal fluence within the 95% confidence interval of that measured by biodosimetry. These methods have potential to develop into flexible, convenient ways to measure germicidally effective UV fluence from any type of UV lamp.

In order to understand the redox chemistry of chromium at low concentrations $(100\mu \mathrm{g}∕\mathrm{L})$ under conditions typically found in drinking water systems, three reductants and four oxidants were tested in three different waters at pH 5, 7, and 9. In the absence of any oxidant or reductant, Cr(VI) was stable at all three pHs, while Cr(III) precipitated out of solution at pH 9 and greatly impacted the reduction reactions. Stannous chloride was more effective than sodium sulfite or sodium sulfide for reducing Cr(VI) to Cr(III). Sulfide is not likely to be used as a reductant due to the long reaction time $\left(120\mathrm{h}\right)$ to achieve the same reduction as $\mathrm{Sn}{\mathrm{Cl}}_2$ , while sulfite may be effective at higher doses. The oxidation of Cr(III) by dissolved oxygen and chloramine was very slow, while ${\mathrm{Cl}}_2$ and $\mathrm{K}\mathrm{Mn}{\mathrm{O}}_4$ were effective oxidants under many conditions. A ${\mathrm{Cl}}_2$ residual in a drinking water distribution system may oxidize any soluble Cr(III) to Cr(VI) because of the long contact time, so Cr treatment strategies will need to remove both Cr(III) and Cr(VI).

To understand the characteristics of particle size distribution (PSD) in highway runoff and to facilitate designing best management practices, PSD $(2–1,000\mathrm{\mu }\mathrm{m})$ was monitored in seven rainfall events in the 2002–2003 rainy season at three highway sites in west Los Angeles. Most of the particles in number were less than $30\mathrm{\mu }\mathrm{m}$ in diameter and more than 90% were less than $10\mathrm{\mu }\mathrm{m}$ . Particle number concentration decreased rapidly to $6\mathrm{mm}$ of accumulated rainfall and then declined more slowly throughout the storm. Particle number concentration was correlated with total suspended solids (TSS) and turbidity. Grab sample particle median diameter increased with increasing TSS. A two-compartment settling tank was evaluated using the measured PSD and was effective in removing both small and large particles. Capturing and retaining the first 20% of the runoff volume on seasonal average can remove 40% of the total particulate load based on calculated particle mass. Using literature data for metal concentrations sorbed to particles, this size holding compartment coupled with a similar size continuous flow clarifier can achieve 65–90% removal for the metals investigated.

An investigation was conducted to develop a simple method for tracking the fate and transport of recycled water following recharge into a shallow brackish aquifer (caprock aquifer) in a coastal area on the Island of Oahu, Hawaii. Several naturally present chemical constituents including the boron isotopic signature $\left(\delta {}^{11}\mathrm{B}\right)$ were used to characterize each of the caprock aquifer source waters and the recycled water. Because of the influence of seawater, only $\delta {}^{11}\mathrm{B}$ could be used to clearly distinguish the recycled water from the source waters and the caprock aquifer water. Estimates of the mixing ratios of source waters in the aquifer were made and a method was developed to determine the fraction of wastewater present in a brackish water sample recovered from a monitoring well during recharge operations without addition of a tracer. This method can be adapted to monitor any other brackish aquifer subjected to wastewater recharge.

Slow sand filtration (SSF) is widely used throughout the world for the treatment of drinking water. However, relatively little attention has been given to the development of a comprehensive process model. Previous studies have considered separate aspects of the SSF process, such as developing an improved representation of the schmutzdecke layer, and a more detailed description of the microbial dynamics. The objective of this work was to develop a deterministic simulation model of the SSF process incorporating fundamental physicochemical and biological dynamics within a classical filtration framework. The model was based on a temporal and spatial finite difference method and was calibrated and verified using operational data from pilot-scale SSF units. Results from the calibration showed that the model satisfactorily predicts headloss development in SSF units. There was no significant difference between many of the most sensitive model parameter values for two successive runs of the same filter. However, a few individual model parameters (e.g., in the fundamental headloss equations) were found to vary with filtration run and it is speculated that this is due to seasonal factors.

This paper describes the use of a deterministic slow sand filter process model to investigate and assess some of the fundamental aspects and mechanisms operating during slow sand filtration (SSF). These include the role of the schmutzdecke, biomass development, and the initial condition of the filter, to the overall process performance. The SSF process model has been developed recently and is described in a companion paper by Campos et al., in 2006. It attempts to provide a simulation of the physicochemical and biological processes responsible for the filtration mechanisms operating in SSF. The simulation of filter runs has been carried out with the help of extensive pilot plant data provided by Thames Water Utilities Ltd., involving both uncovered and covered filter beds. The results demonstrate that the presence and nature of a schmutzdecke layer profoundly influence the spatial and temporal development of interstitial biomass within the sand and, consequently, the headloss profile. Microbial interactions in the filter bed play a fundamental role in the process and are involved in setting the pattern and magnitude of headloss development. The model also demonstrates the significance of residual deposits within the filter after surface cleaning, on the subsequent filter behavior.

Two upflow anaerobic sludge blanket (UASB) reactors were operated for approximately $900\text{days}$ to examine the feasibility of treating municipal wastewater under low temperature conditions. In this paper, a modified solid distribution model has been formulated by incorporating the variation of biogas production rate with a change in temperature. It was found that the model simulated the solid distribution well as confirmed by experimental observations of solid profile along the height of the reactor. Mathematical analysis of tracer curves indicated the presence of a mixed type of flow pattern in the sludge-bed zone of the reactor. It was found that the dead-zone and bypass flow fraction were impacted by the change in operating temperatures.

The concentrations of several selected organic hazardous substances were investigated in domestic graywater. In total, 41 of 81 organic hazardous substances were found in concentrations above the detection limits (nonylphenol and octylphenol ethoxylates, brominated flame-retardants, organotin compounds, polyaromatic hydrocarbons, polychlorinated biphenyls, phthalates, linear-alkyl benzene sulfonate, and triclosan). Moreover, total solids, biochemical oxygen demand $\left({\mathrm{BOD}}_7\right)$ , chemical oxygen demand (COD), total nitrogen, total phosphorus, potassium, and sulphur were investigated and presented for graywater. Another objective was to suggest potential household sources for a selected number of organic hazardous substances. The present and past investigations reveal households to be obvious contributors of organic hazardous substances to municipal wastewater, and that graywater is an important media in this transport. The spreading derives from diffuse household sources like everyday activities (laundry, cleaning, etc.), the wearing down of things such as pipe material and interior fittings, and from airborne deposition.

The enhanced biological phosphorus removal (EBPR) performances of phosphate-accumulating organisms (PAOs) under organic loading fluctuations were investigated using a sequencing batch reactor (SBR) with anaerobic/oxic stages. The adaptability of PAOs was evaluated after establishing a normal steady-state condition [chemical oxygen demand ( ${\mathrm{COD}}_{\mathrm{in}}$ )=150 mg/L]. During SBR operation, the initial COD was changed gradually or abruptly. When the initial COD increased gradually from the steady state to 300 mg/L, the biomass increased steadily and the system showed stable EBPR. However, when the initial COD oscillated from 150 to 300 or 50 mg/L abruptly, PAOs could not adapt themselves to these sudden changes, resulting in unstable EBPR. When the organic loading returned to a normal condition, the system was recovered to stable EBPR in 2 days after the high organic loading fluctuation, while it was not after the low organic loading fluctuation. Using fluorescent in situ hybridization technique, Rhodocyclus-related PAO population changes were monitored. It was demonstrated that PAOs would wash out faster under the low organic loading fluctuation than the high organic loading fluctuation.

The removal of the herbicides diuron, isoxaben, oryzalin, and clopyralid by shredded cedar mulch was studied in laboratory batch and column experiments. The distribution coefficients $\left(K_d\right)$ for the herbicides diuron, isoxaben, and oryzalin measured in batch experiments ranged from 129 to 187 L/kg for raw mulch and from 153 to 341 L/kg for ground mulch. $K_d$ could not be accurately determined for clopyralid because of its weak sorption. A reactive transport model that described adsorption-desorption using a linear two-rate (site) reversible submodel provided a good fit for the experimental breakthrough data for isoxaben from column studies; adjusting the exchange rate coefficients using molecular diffusion coefficient ratios allowed breakthrough curves for oryzalin and diuron to be predicted effectively using no adjustable parameters. Model sensitivity analysis indicates that over 80% herbicide removal efficiency can be obtained for detention times greater than 8 min and storm durations of less than 100 min for the ground mulch particles. Widespread use of mulch as landscape material and the short detention times required for reasonable removal efficiency suggests that a mulch treatment system may be an efficient best management practice; these experimental and model results provide a basis for future pilot testing.

This paper presents a mathematical model for the pressure inside the vapor space of an underground storage tank (UST). Using mass balances based on dispensing activities, vapor recovery, evaporation, leaks, and the safety vent, the model resulted in a system of nonlinear differential equations with unknown parameters, leak rate and evaporation rate. Given the leak rate and evaporation rate, the pressure inside the UST can be obtained by solving the system of differential equations numerically. Given the pressure inside a UST over a period of time, one can find the evaporation and leak rates such that the calculated pressure from our model best fits the given pressure data. This optimal value of leak rate can allow us to determine whether the UST system is leaking and if the leak rate is above the EPA standard. Numerical results and statistical analysis of our model are also presented.

The main objective of this paper is to explore the potential application of electromagnetic waves to evaluate the effect of contaminant removal in granular soils. Thus, various specimens of saturated silica sand were prepared using paraffin oil and lubricant oil as contaminants. Four flushing fluids were used to remove the contaminants from sand columns: Deionized water, water-detergent, water-detergent-alcohol solution, and water vapor. Dielectric permittivity was measured at different stages of the removal process at the frequency from $20\mathrm{MHz}\text{to}1.3\mathrm{GHz}$ . The measured permittivity was compared with that determined for clean and fully contaminated specimens. A theoretical mixture formula was calibrated and implemented to estimate the volume fraction of contaminant present in the pore fluid. It is concluded in this work that dielectric parameters reflect the contamination level of the soil for the nonpolar organic compounds used here. Measurement of permittivity allows us to determine that the inclusion of alcohol and detergent in the displacing fluid improved the removal efficiency. However, water vapor was the most efficient removal agent.

Ethene (ETH) is often associated with vinyl chloride (VC) in contaminated groundwater, as it is formed along with vinyl chloride during reductive dechlorination of higher chloroethenes (e.g., perchloroethylene and trichloroethylene). In the present study the interaction between VC and ETH during their aerobic biodegradation by enrichment cultures was investigated. The cultures were able to use both compounds as growth substrates. In mixture experiments, the degradation rate of one substrate was affected by the presence of the other. A biokinetic model based on competitive inhibition described well the observed substrate interactions over a range of initial VC (0–144 $\mu \mathrm{mol}{\mathrm{L}}^{-1}$ ) and ETH (0–37.5 $\mu \mathrm{mol}{\mathrm{L}}^{-1}$ ) concentrations, using parameters estimated from single-substrate experiments. Notably, half-velocity coefficients could be used as competitive inhibition coefficients. This finding shows the importance of obtaining accurate measurements of half-velocity coefficients in order model competitive inhibition processes. Simulation results showed that when the initial ETH concentration was raised from 0 to 30 $\mu \mathrm{mol}{\mathrm{L}}^{-1}$ , the apparent half-velocity coefficient for VC $\left(K_{\mathrm{VC}}^{\mathrm{APP}}\right)$ increased by nearly three times, from 12.9 to 35.4 $\mu \mathrm{mol}{\mathrm{L}}^{-1}$ . This finding has strong environmental implications because a low half-velocity coefficient for VC is regarded as the major prerequisite for achieving efficient and complete VC degradation. Moreover, the effect of ETH on the efficiency of VC removal is strongly dependent on the $K_{\mathrm{VC}}∕K_{\mathrm{ETH}}$ ratio, consequently determination of $K_{\mathrm{ETH}}$ for VC-degrading microbes is important when biodegradation (or bioaugmentation) is considered for clean up of VC-contaminated sites. Additional model simulations, using the ratio of $K_{\mathrm{VC}}$ to $K_{\mathrm{ETH}}$ for previously characterized VC- and ETH-utilizing microorganisms (values ranged from 0.06 to 1.2) showed that their ability to degrade VC in the presence of ETH may differ significantly.

The aim of this work is to study the effect of metallic oxides additions to mortars on their mechanical and long-term environmental behaviors. Four common metal oxides were selected ( ${\mathrm{Fe}}_2{\mathrm{O}}_3$ , ZnO, as main oxides and a mix of $\mathrm{Pb}\mathrm{O}+{\mathrm{Cr}}_2{\mathrm{O}}_3$ , as minor oxides) and incorporated in mortars using a fractional factorial design $(2^{3-1}+3)$ of experiments. The studied variables were: setting time (ST), compressive and flexural strengths (UCS and UFS), availability, effective diffusion coefficient (De), and immission after $100\text{years}$ . The analysis of the results shows that ZnO and ${\mathrm{Fe}}_2{\mathrm{O}}_3$ are statistically significant on the mechanical properties at short ages. ZnO increases the ST and it decreases the UCS and UFS, whereas ${\mathrm{Fe}}_2{\mathrm{O}}_3$ shows an antagonistic effect. The metal release from monoliths was low, leading to small values of De. Finally the estimated immission of Pb, Zn, and Cr after $100\text{years}$ were lower than the standard limit of Dutch regulation.

Copper oxide and zirconia-supported copper oxide catalysts were tested for their catalytic activity for carbon monoxide and propylene oxidation reactions. The synthesized catalyst was supported by wet impregnation on zirconia. The higher activity of zirconia-supported catalyst compared to unsupported catalyst may be attributed to homogeneous and higher dispersion on zirconia, ionic oxygen carrying capacity of zirconia. Catalyst $10\%\mathrm{Cu}\mathrm{O}∕\mathrm{Zr}{\mathrm{O}}_2$ showed a best conversion efficiency of 90% at a temperature as low as $265°\mathrm{C}$ for CO oxidation. $T_{50}$ and $T_{100}$ for propylene oxidation on zirconia-supported copper oxide were 392 and $450°\mathrm{C}$ , respectively.

With good quality of fluidization the air flows uniformly through the bed and the particles are distributed well in the fluid stream, which may improve combustion efficiency. However, the effects of operating parameters and characteristics of waste on generation of particulate matters (fly ash) and quality of fluidization were rarely evaluated. This study investigated the relationship between the quality of fluidization and generation of particulate matters during incineration. The operating parameters included waste characteristics, operating gas velocity, and temperature. The statistical and power spectrum analyses were used to assess pressure fluctuations. The experimental results showed that when the combusion temperature was controlled at 600°C, the mean amplitude was reduced and the dominant frequency was increased, indicating that the quality of fluidization was better than for other conditions. Consequently, generation of fly ash during incineration was minimized when the combustion temperature was controlled at 600°C. The more amount of fly ash was generation with acrylonitrile–butadiene–styrene (ABS) combustion at different conditions, and combustion of wood generated the least amount of ash. It may be that the wood combustion is quite stable and the combustion behavior of ABS is the most violent among the four plastic wastes. Notably, the dominant frequency increased with temperature for wood combustion, and the quality of fluidization was improved at 800°C. For different results of $U∕U_{\mathrm{mf}}$ , they did not have obvious tendencies. Consequently, behavior of the bed material and quality of fluidization determined the generation of fly ash. Therefore, the combustion efficiency may be enhanced by improving the quality of fluidization.