Journal of Environmental Engineering

This study analyzed candidate hydrogen-fueled vehicles for near and long-term use associated with their efficiency, performance, and emissions. Various types of hydrogen-fueled vehicles were assessed using Argonne National Laboratory's Powertrain System Analysis Toolkit vehicle simulation model. These include hythane- and hydrogen-fueled internal combustion engines (ICEs), hydrogen-fueled hybrid electric propulsion, and direct hydrogen fuel cells. Vehicle sizes and configurations, consistent with the available component models/data, were simulated to compare efficiency and emissions with baseline conventional vehicles. The simulations provided salient information on the vehicle characteristics, performance, and efficiency, as functions of operating conditions on standard driving cycles. It was found that substantial gains in fuel economy can be achieved through hybridization both for conventional and fuel cell vehicles. When hybridized, hydrogen ICE configurations achieve similar fuel economy to gasoline counterparts. The results also confirm that ICE hybrid electric vehicles (HEV) achieve higher fuel economy than fuel cell configurations and comparable results with fuel cell HEV. Comparison of efficiency results for various driving cycles further indicates that cycles with low power demand are most suited for hybrid operations.

Conventional coagulation and sedimentation processes can be significantly disrupted by gas bubbles, attaching to, and then floating coagulant floc. This study sought to understand the fundamental factors that lead to bubble formation and corresponding floating floc during coagulation and sedimentation. Gas bubbles (causing the floating floc) can form whenever the total dissolved gas pressure exceeds the local solution pressure, which can occur at localized minimum pressures during rapid mixing at high fluid velocities. Very high rate rapid mixers can cause bubble formation and floating floc even in waters undersaturated with dissolved gas. The formation and stability of floating floc are dependent on the local solution pressure, amount and type of dissolved gas supersaturation, temperature, length of rapid mixing, surface chemistry of the mixing paddle, floc, and attachment forces.

In the United States, foundry facilities produce huge quantities of by-products to be disposed of annually. These by-products are broadly divided into three waste streams: sand, dust, and slag. To characterize foundry by-products in terms of waste streams helps beneficially manage and reuse foundry by-products based on individual environmental characteristics. One thousand one hundred eighty two data sets addressing bulk and leaching characterization of up to 24 metallic elements in sand, dust, and slag are collected and assessed using statistical methodologies. Findings indicate that sand is not hazardous with high confidence per metallic elements, and a leaching program is not mandatory in assessing whether sand is hazardous or not regarding metallic elements. No evidence indicates that dust and slag are nonhazardous materials. Only a fraction of metallic elements are extracted from as-received waste streams. Through comparisons of statistical parameters including estimated means, 95th percentiles and data distributions, sand is found less contaminated by most metallic elements than dust and slag, but metallic elements in sand leachate are in the similar levels as those in dust and slag leachates. Fe, Zn, and Al are highly concentrated in dust and slag on average, which suggests their potential reclamations.

Aggregation of microbes with particles can reduce the effectiveness of ultraviolet (UV) disinfection. This study evaluated the comparative impact of dispersed spores, dispersed spores mixed with clay particles (nonaggregated), spore–spore aggregates, and spore–clay aggregates on UV disinfection performance in simulated drinking waters. Aggregates were induced by flocculation with alum and characterized by particle size analysis (count, volume, and surface area) of dispersed and aggregated systems, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. It was concluded that spores within aggregates of the spore–clay system were protected from UV irradiation compared to nonaggregated spores and the difference between these systems was found to be statistically significant throughout the UV range tested. In addition SEM-EDX analysis suggested that aggregate composition is nonhomogeneous with respect to the ratio of spores and clay particles among aggregates. It was estimated that 30–50% of the spores in the aggregates tested were protected from UV irradiation.

Ultraviolet (UV) absorbance measurements are subject to significant error using a standard spectrophotometer when particles or aggregates that scatter light are present. True UV absorbance for highly turbid waters should be measured using integrating sphere (IS) spectrophotometry that allows the collection of reflected and transmitted radiation simultaneously. This is especially important when the effects of scattering impact UV disinfection—such as with the presence of aggregates. The impact of light scattering of particle-aggregated microbes on UV disinfection was evaluated by comparing standard spectrophotometer and integrating sphere absorbance measurements for UV fluence determination. Spore–clay aggregates in simulated drinking waters and spore aggregates with natural particles from raw waters were induced by flocculation with alum. Coagulated systems significantly decreased the UV inactivation effectiveness compared to the noncoagulated system with the effects more pronounced for raw natural water. Absorbance measurement of suspensions and aggregates using standard spectrophotometry in the calculations of fluence resulted in overdosing whereas the use of IS spectroscopy did not. The results demonstrated that aggregation protected spores from UV disinfection, and that use of proper absorbance measurement techniques, accounting for particle scattering, is essential for correct interpretation of the results.

Bioremediation of oil spills on tidally influenced beaches commonly involves the addition of a nutrient solution to the contaminated region of the beach at low tide to stimulate the growth of indigenous oil-degrading bacteria. Maximizing the residence time of nutrients in the beach and subsequently their contact time with microorganisms is a main goal for successful bioremediation. Therefore, understanding the effects of the tide on water flow and solute transport in a beach is an essential task for designing a nutrient application strategy. We investigated these effects by conducting a tracer study in a laboratory beach simulating nutrient application on natural beaches. The study consisted of applying, at low tide, a conservative tracer solution onto the beach surface near the high-tide line and monitoring its movement in the beach subsurface. The tidal motion caused the applied plume to move downward and seaward. The downward movement occurred during rising tides, while the seaward movement occurred mainly during falling tides. The results indicate that nutrients should be applied at the high-tide line during low tides. Guidelines for scaling up the results to natural beaches are provided along with an example.

An innovative anaerobic–aerobic integrated bioreactor system consisting of an upflow anaerobic sludge blanket (UASB) and a jet loop reactor was developed to investigate the feasibility of combined removal of carbon and nitrogen for a low-strength wastewater at different hydraulic retention times (HRTs) and recycle ratios. Total chemical oxygen demand (COD) removal of the integrated system increased from 87 to 92%, at a combined system HRT of $44\mathrm{h}$ , when the recycle ratio was increased from 100 to 400%, respectively. Denitrification efficiency of the integrated system increased from 49 to 86%, at all HRTs, when the recycle ratio was increased from 100 to 400%. The integrated system, on average, achieved more than 78% of total nitrogen at all HRTs. Nitrogen content of the biogas produced from the UASB reactor increased with increase in recycle ratios while the methane content exhibited a reverse trend, irrespective of the HRTs. Sludge volume index of the UASB reactor increased from $15\text{to}42\mathrm{mL}∕\mathrm{g}$ total suspended solids at the end of the study. Specific methanogenic activity of the granular sludge decreased from 1.3 to 0.8 g $\mathrm{C}{\mathrm{H}}_4–\mathrm{COD}∕\mathrm{g}$ volatile suspended solids per day at the end of the study. Nitrogen and COD mass balance of the integrated system indicated that a substantial amount of influent nitrogen and COD was lost in the effluent as dissolved form.

The use of thermal and/or oxidative treatment to enhance anaerobic digestion of excess municipal sludge was evaluated. Different reactor configurations were studied. A “moderate” temperature $(90°\mathrm{C})$ was used in the thermal treatment and hydrogen peroxide was the oxidant. Thermal treatment alone did not increase solids destruction. A maximum of 15.2% increase in volatile suspended solids (VSS) destruction was observed with the oxidative treatment. A synergistic effect was observed when both treatments were combined. The increase in VSS destruction when both cotreatments were applied (oxidative and thermal) ranged between 27.2 and 29.0%, depending on the reactors configuration. Parameters such as methane production, chemical oxygen demand removal, nitrogen and volatile fatty acids concentrations, and fecal coliforms removal were also evaluated for the different configurations studied.

This paper reports the in situ field saturated hydraulic conductivity of municipal solid waste at a landfill in Florida. The saturated hydraulic conductivity $\left(K_s\right)$ was estimated at 23 locations using the borehole permeameter test, a method commonly used for determination of the $K_s$ of unsaturated soil. The $K_s$ of the landfilled waste was found to range from $5.4\times {10}^{-6}$ to $6.1\times {10}^{-5}\mathrm{cm}∕\mathrm{s}$ . The $K_s$ was found to be on the lower end of the range of $K_s$ reported by previous studies. The hydraulic conductivity of the waste decreased with depth, the likely result of greater overburden pressures associated with deep locations of the landfill. Permeability values $\left(k_w\right)$ of the landfilled waste calculated based on $K_s$ were compared with permeability values estimated using air as the fluid (air permeability, $k_a$ ). Values of $k_a$ were found to be approximately three orders of magnitude greater than those of $k_w$ . The lower permeability of the waste to water was primarily attributed to entrapped gas. Other factors such as potential clogging of media and short-circuiting of air along the well may also have contributed to the differences in $k_a$ and $k_w$ .

Long-term (e.g., 5–15 years) groundwater concentration versus time records were compiled from 47 near-source zone monitoring wells at 23 chlorinated solvent sites (52 total records). Chlorinated volatile organic compound (CVOC) concentrations decreased significantly in most of the 52 temporal records, with a median reduction in concentration of 74%. A statistical method based on a Mann–Kendall analysis also showed that most sites had statistically significant decreasing concentration trends over time. Median point decay rate constants $\left(k_{\mathrm{point}}\right)$ values were calculated for nine sites containing tetrachloroethene (PCE); 13 sites containing trichloroethene (TCE); two sites containing cis-1,2-dichloroethene (DCE); and six sites containing 1,1,1-trichloroethane (TCA). The TCA sites had the highest $k_{\mathrm{point}}$ values (0.34/year) followed by PCE, DCE, and TCE (0.23/year, 0.16/year, and 0.11/year, respectively) (equal to decay half-lives of 2.0, 3.0, 4.3, and 6.1 years, respectively). If the median point decay rates from these sites are maintained over a 20 year period, the resulting reduction in concentration will be similar to the reported reduction in source zone concentrations achieved by active in situ source remediation technologies (typical project length: 1–2 years).

The ability of chitin fermentation products to promote tetrachloroethene (PCE) reduction was evaluated in a continuous-flow column system to identify how different electron donors affect reductive dechlorination. Natural chitin fermentation products were initially used to support PCE reduction. Acetate $\left(3.5\mathrm{mM}\right)$ was the dominant fermentation product, followed by propionate $\left(0.1\mathrm{mM}\right)$ , butyrate $\left(0.1\mathrm{mM}\right)$ , and hydrogen $\left(100\mathrm{nM}\right)$ . After chlorinated ethene concentration profiles reached pseudo steady state, the ability of individual fermentation products (acetate, $\mathrm{acetate}+\mathrm{propionate}$ , propionate, or formate) to support PCE reduction was evaluated. None of the fermentation products tested stimulated dechlorination as well as the suite generated from chitin $(k_{\mathrm{PCE}}=6.9{\mathrm{day}}^{-1})$ ; however, acetate-stimulated PCE dechlorination the best $(k_{\mathrm{PCE}}=5.3{\mathrm{day}}^{-1})$ , followed by formate $(k_{\mathrm{PCE}}=2.4{\mathrm{day}}^{-1})$ , acetate+propionate $(k_{\mathrm{PCE}}=1.8{\mathrm{day}}^{-1})$ , and propionate $(k_{\mathrm{PCE}}=1.2{\mathrm{day}}^{-1})$ . Similar trends were observed for the PCE daughter products trichloroethene and dichloroethene. Free energies of individual fatty acid reactions were calculated and shown to be useful predictors of dechlorination performance, except for the case of acetate+propionate. Hence, acetate is the dominant fatty acid controlling dechlorination in the chitin-enhanced system, propionate appears to have an inhibitory effect when present with acetate alone, and other unidentified nutrients produced during chitin fermentation likely contribute to dechlorination activity as well.

Removals of dissolved organic carbon (DOC), ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA) and carboxylated alkylphenol polyethoxylate metabolites (APECs) were studied at the Sweetwater (Tucson, Ariz.) soil aquifer treatment site that treated chlorinated secondary effluent. The site was operated in a first phase by flooding irregularly for weeks interrupted by days of drying and in a second phase by a regular schedule of flooding for 3 days and drying for 4 days. The average hydraulic loading rates were 0.13 and $0.17\mathrm{m}∕\mathrm{day}$ in the first and second phases, respectively. During drying, oxygen intruded at least $3\mathrm{m}$ deep into the unsaturated subsurface causing nitrification of the ammonium that was retained in the top layer during flooding. Nitrification increased nitrate concentrations to $>200\mathrm{mg}∕\mathrm{L}$ but most was removed to $<10\mathrm{mg}∕\mathrm{L}$ during transport to $38\mathrm{m}$ depth. At $38\mathrm{m}$ depth, removals of DOC, EDTA, NTA, and APECs during the first phase were 85, 80, 90, and 98%, slightly higher $(<7\%)$ than during the second phase. Most of the DOC removal occurred during transport to $3\mathrm{m}$ and most of the trace organics removal occurred during transport from 3 to $38\mathrm{m}$ depth.

The essence of three case studies in relation to the global problem of surface and groundwater contamination by inorganic salts and biodegradation-resistant (“hard”) nonionic surfactants (APEOs) is presented and the results analyzed as far as the long-term consequent water salt and APEO profiles are concerned. The main conclusion derived is that sustainable large-scale reuse/recycling and reclamation in semiarid zones requires a combined desalination-biological treatment of APEO-free sewage/wastewaters before their reuse. This should be done without delay in order to ensure the quality of the supplied water from the scarce resources and to avoid, most probably, an irreversible process of aquifer contamination in these zones.

The transport of polychlorinated biphenyls (PCBs) in sediment is difficult to study in the laboratory due to their low solubility and strong tendency to sorb to sediment and experimental equipment. A small-scale laboratory microcosm was designed to study PCB transport in anaerobic surface sediment at microscale and to quantify transport rates. Results of verification testing showed that the experimental system enabled quantitative characterization of the diffusive transport of PCBs in sediment in a reasonable time frame (months). The fine-spatial-resolution results obtained were as expected with the less chlorinated, more mobile congeners transporting the fastest and the more heavily chlorinated compounds transporting more slowly. This laboratory microcosm system could be used to study the transport of many types of pollutants in sediment, but is particularly useful for hydrophobic organic compounds.

The use of aerobic granules in wastewater treatment can reduce the land area that is needed for the treatment of sewage. Until now granulation has been mainly studied using artificial wastewater. Studying the possibility of forming aerobic granules on domestic sewage in a sequencing batch reactor was a logical step in the scaling-up process and development of this technology. Therefore, aerobic granulation was studied using presettled sewage as influent. After $20\text{days}$ of operation at high chemical oxygen demand (COD) loading heterogeneous aerobic granular structures were observed, with a sludge volume index after $10\min$ settling of $38\mathrm{mL}{\mathrm{g}}^{-1}$ and an average diameter of $1.1\mathrm{mm}$ . Applying a high COD load was found to be a critical factor for the formation of aerobic granules on this type of influent. Therefore short cycle times and concentrated wastewater are preferred to form granules in a sequencing batch reactor when low strength wastewater is used. The nutrient removal was not optimized in this study.