Journal of Environmental Engineering

The application of surfactants for the bioremediation of sites contaminated with polycyclic aromatic hydrocarbons has been widely reported, because they are known to increase PAH solubility and desorption, thereby enhancing their bioavailability to biofilm microorganisms. The effects of a nonionic surfactant on the biodegradation of PAHs in porous media, as well as the fate of the surfactant, were investigated in this study. Column experiments in the presence of the surfactant showed that the degradation of the two-ring PAH alone was not significantly affected, but that there was a small enhancement of three- and four-ring PAH degradation when they were present as sole substrates and when using Triton X-100. This was due to the higher solubility of the PAHs in the presence of the surfactant. Biofilm seemed to respond well to binary mixtures of phenanthrene–naphthalene and pyrene–naphthalene, with removals of 45.5 and 24.1%, respectively, in the presence of the surfactant; however, higher biodegradations were always achieved by having just PAH mixtures without the surfactant, indicating the importance of cometabolic mechanisms over improved solubilization of PAHs. Optical sections taken using a confocal laser scanning microscope allowed observation of a heterogeneous web-like matrix of biofilm, with diverse biological aggregate structures.

Bacillus subtilis spores were used as an indicator organism to characterize the effects of UV radiation and iodine, alone and in combination, as disinfectants for water. Spore exposures to UV radiation were conducted in shallow, well-mixed batch reactors under collimated beams. Three (essentially) monochromatic collimated UV sources were used in these experiments, with characteristic emission wavelengths of 222, 254, and $282\mathrm{nm}$ . Iodine exposures were conducted in well-mixed batch reactors. Synergism was demonstrated when UV (at certain doses) and iodine were used as sequential disinfectants; synergism was attributed to UV-induced damage that enhanced the susceptibility of spores to iodine.

Nitrification and granular activated carbon (GAC) filtration impact leaching of lead/copper to potable water under typical home plumbing configurations. GAC filters removed the disinfectant and caused rapid establishment of nitrification in chloraminated systems. The potential adverse consequences of whole house GAC filters deserve increased scrutiny in chloraminated systems. The lower pH values from nitrification and other microbes during overnight stagnation in pipes can markedly increase (up to 800%) lead and copper contamination of water.

In this study, a copolymer, cyclodextrin/epichlorohydrin was synthesized and used as an adsorbent to remove two taste and odor causing compounds, namely, MIB and geosmin from the Lake Michigan water. The removal efficiency of these compounds using the copolymer on average was 74.5% for MIB and 77.5% for geosmin as compared to the removal efficiency using powdered activated carbon that resulted in 52.9% and 67% removal, respectively, for the same compounds. The removal efficiencies were examined for an initial concentration range of 20 to $120\mathrm{\mu }\mathrm{g}∕\mathrm{L}$ for both MIB and geosmin.

The capacity of complete simultaneous ammonium and phosphate removal was studied in a laboratory scale Dephanox system in relation to its internal bypass ratio (BPR). In this configuration, most of the ammonium detected in the effluent is ammonium bypassed by the system’s internal settler. Therefore, this research studies the possibility of complete simultaneous ammonium and phosphate removal by means of the balance of bypassed ammonium with ammonium requirement for growth of denitrifying phosphorus accumulating organisms in the anoxic tank. During these experiments, ammonium removal was governed by internal BPR and limited by sludge settleability. The predominant anaerobic-anoxic sludge developed a high settleability, allowing the application of drastic low BPRs. The system studied under many BPRs proved to achieve almost complete simultaneous ammonium and phosphate removal for BPRs ranging from 0.08 to 0.13 of the influent. A BPR lower than the inferior limit produced extreme accumulation of sludge into the internal settler, interfering in the distribution of sludge and consequently in removal efficiency. A positive effect of the internal settler was the extension of anaerobic contact time and anaerobic solids retention time. The increased phosphorus release suggests that a higher volatile fatty acids production might have occurred when raw wastewater was used as influent.

This study aimed to examine the process configurations for mesophilic anaerobic digestion of sewage sludge, when incorporated with thermal treatment of $120°\mathrm{C}$ for $1\mathrm{h}$ . Four types of process configurations were designed: control (no thermal treatment), pretreatment and posttreatment configurations of the single-stage process, and an interstage-treatment configuration of the two-stage process. The lab-scale digesters were operated at $35°\mathrm{C}$ with the sewage sludge of 4.5% total solids, and were equally set at the total hydraulic retention time of 20 days. At the steady state, the control digester showed 35.3% of volatile solids (VS) destruction and $0.168\mathrm{L}∕\mathrm{g}$ VS fed of methane production. Compared to the control, the VS destruction in the pre-, post-, and interstage-treatment configurations was increased by 4.5, 6.6, and 9.9%, respectively, while the methane production in the post- and interstage-treatment configurations was improved by 0.036 and $0.028\mathrm{L}∕\mathrm{g}$ VS fed, respectively. The pretreatment configuration yielded identical methane production to the control. Therefore, it is more effective on anaerobic digestibility to apply the moderate thermal treatment after sewage sludge is digested once. On the other hand, the increase in soluble chemical oxygen demand and deterioration of dewaterability were observed, when solids destruction was improved.

The “velocity pulse model” simulates the transfer of turbulence from flowing water into a sediment bed, and its effect on the diffusional mass transfer of a solute (e.g., oxygen, sulfate, or nitrate) in the sediment bed. In the “pulse model,” turbulence above the sediment surface is described by sinusoidal variations of vertical velocity in time. It is shown that vertical velocity components dampen quickly inside the sediment when the frequency of velocity fluctuations is high and viscous dissipation is strong. Viscous dissipation $\left(\nu \right)$ inside the sediment is related to the apparent viscosity depending on the structure of the sediment pore space, i.e., the porosity and grain diameter, as well as inertial effects when the flow is turbulent. A value $\nu ∕{\nu }_0$ between 1 and 20 ( ${\nu }_0$ is kinematic viscosity of water) has been considered. Turbulence penetration into the sediment is parametrized by the Reynolds number $\mathrm{Re}=\mathrm{UL}∕\nu$ and the relative penetration velocity $W∕U$ , where $U$ =amplitude of the velocity pulse; and $W$ =penetration velocity; $L=WT$ =wave length of the velocity pulse; and $T$ is its period. Amplitudes of vertical velocity components inside the sediment and their autocorrelation functions are computed, and the results are used to estimate eddy viscosity inside the sediment pore system as a function of depth. Diffusivity in the sediment pore system is inferred by using turbulent or molecular Schmidt numbers. Turbulence penetration from flowing water can enhance the vertical diffusion coefficient in a sediment bed by an order of magnitude or more. Penetration depth of turbulence is higher for low frequency velocity pulses. Vertical diffusivity inside the pore system is shown to decrease more or less exponentially with depth below the sediment/water interface. Vertical diffusivities in a sediment bed estimated by the “velocity pulse model” can be used in pore water quality models to describe vertical transport from or into flowing surface water. The analysis has been conducted for a conservative material, but source and sink terms can be added to the vertical transport equation.

Industrial flares have been identified as a potential major source of hydrocarbon emissions from chemical and petrochemical plants in the Gulf Coast area. Several studies have shown that crosswind may compromise the expected 98% efficiency level of these units. In order to understand the key variables in flare operation, a 3D simulation has been performed to predict the effect of crosswind on the efficiency of high momentum, turbulent combustion flames by using the commercial software Fluent 6.2. First, a ${\mathrm{CH}}_4+$ air flame was simulated for quiescent conditions and temperature and concentration profiles were compared to experimental data. Simulations were then performed to study how combustion efficiency may be affected by increasing the crosswind velocity. We have also analyzed the effect of crosswind at higher jet velocities. Our results show that high momentum flames are more sensitive to the crosswind problem as the jet velocity increases. The ultimate goal of this model is to obtain a quantitative understanding of how crosswind may affect the operation of industrial flares, a major source of highly reactive volatile organic compound emissions from chemical and petrochemical plants.

Based on the concept of functional intervals, fuzzy inexact mixed-integer semiinfinite programming (FIMISIP) method is developed for municipal solid waste management planning. The method allows the uncertainties in parameters expressed as fuzzy, interval, and functional interval numbers to be directly communicated into the programming problem. The FIMISIP problem is solved by dividing it into two interactive semiinfinite programming (SIP) subproblems. Solutions reflecting the inherent uncertainties can then be generated by combining the SIP solutions into a set of decision intervals. The method is applied to a municipal solid waste management planning system for demonstrating its effectiveness in dealing with uncertain and dynamic complexities. Compared to the previous inexact programming methods, FIMISIP has the advantages as follows: (1) the dynamic complexity can be addressed by introducing the functional-interval parameters associated with time into the programming problem; (2) the FIMISIP solutions provide a set of flexible waste-management schemes to the decision makers; and (3) the FIMISIP solutions are more reliable than those from the previous ILP ones since they can be “really” optimal regardless of how the parameters vary with time within the time period. While this study is a first attempt to solve solid waste management issues under complex uncertainties, the method can be extended to other environmental management planning problems.

Wastewaters containing sugars are easily and rapidly biodegraded, which results in their exerting a short period of intense demand for dissolved oxygen (DO). Their carbonaceous biochemical oxygen demand (BOD) is described by an empirical multiorder decay reaction with an order less than one. Examples show calculations of multiorder BOD equation parameters from glucose and glutamic acid data and the effect of a wastewater on DO sag in a river.

The results are presented from a laboratory and theoretical study to investigate the effects of sediment concentration and initial phosphorus loading on adsorption isotherm and capacity. The tested aquatic sediment was collected from the Chongqing reach of the Yangtze River. The adsorption isotherm of dissolved phosphate was approximated by the Langmuir equation. Using mass conservation and Langmuir adsorption kinetic equations, the authors derived formulas for calculating both the particulate and dissolved phosphate concentration. Kinetic experiments on fine sediment samples $(<0.008\mathrm{mm})$ show that the adsorption process is time dependent and takes place in three stages, namely, an initial fast stage followed by a gradual adsorption, leading to the eventual equilibrium. The results indicate that larger initial phosphate loading causes longer duration, higher adsorption rate, and less adsorption percentages on both the first and second stages. The sediment concentration mainly influences the adsorption rate of the first stage, in which the adsorption rate significantly increases with the increasing sediment concentration.