Journal of Environmental Engineering

This research was performed as part of the San Francisco Public Utilities Commission’s search for more sustainable water resources. Disinfection methods were evaluated for treating light graywater to California drinking water standards for unrestricted, direct nonpotable water use, indoors. Graywater originating from sinks and showers in a commercial office building in southern California was collected in grab samples over 4 weeks. Samples were filtered and tested for disinfection efficacy toward indigenous total coliforms and Enterococci as well as seeded male-specific 2 (MS2) coliphage. The filtered samples were exposed to monochromatic (253.7 nm) ultraviolet (UV) light, chlorination with sodium hypochlorite, and ozonation. A UV dose of ${100\mathrm{mJ}/\mathrm{cm}}^2$ completely inactivated Enterococci and inactivated total coliforms to California drinking water standards required levels and achieved 5-log reduction of MS2 in half of the samples. Sodium hypochlorite met bacteria and virus standards for the graywater at a free-chlorine concentration × time (CT) well below the 450 $(\mathrm{mg}/\mathrm{L})\mathrm{-min}$ required by California drinking water standards. An ozone CT of 0.4 $(\mathrm{mg}/\mathrm{L})\mathrm{-min}$ met bacteriological standards for reuse in two of the four samples. Ozone virus inactivation criteria was inconclusive due to the high-ozone demand of the water matrix when seeded with the test organism; however, an applied ozone dose of $5–7\mathrm{mg}/\mathrm{L}$ would be expected to satisfy the ozone demand and meet the virus criteria. Of the disinfection options discussed, UV light was the least expensive, followed in order of lowest to highest cost by sodium hypochlorite delivered in bulk, sodium hypochlorite generated on-site, and ozone. An important and novel component of this research was that graywater treatment was performed only with tertiary processes and thus, biological treatment was not used. These results are applicable to other light graywaters with similar total organic carbon (TOC) concentrations (less than $5\mathrm{mg}/\mathrm{L}$ as carbon).

In this paper, light-emitting diodes (LEDs), a novel light source, is reported for the photocatalytic degradation of four known pesticides [2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), 4-chlorophenol (4-CP), and 2,4-dichlorophenol (2,4-DCP)] in aqueous solution. 2,4-Dichlorophenoxyacetic acid was further chosen to evaluate the impact of photocatalyst loading and light intensity on the degradation rate. The degradation of 2,4-D under LED irradiation (365 nm) was compared with that using mercury discharge lamp irradiation (350 nm). Irradiation of the different pesticides with a 365-nm LED light source led to their complete mineralization upon prolonged exposure. The degradation rate was slower when mixtures of pesticides were used because of competition between pesticide molecules for adsorption sites, hydroxyl radicals, and holes. A suitable photocatalyst loading was determined to be $2\mathrm{g}/\mathrm{L}$ of ${\mathrm{TiO}}_2$; a linear relationship between the first-order kinetic rate and light intensity (2.7 to approximately 46.5 mW) was observed. A comparison between LEDs and conventional mercury discharge lamps indicated that the former was more energy-efficient.

Resource-limited communities throughout the developing world face significant environmental health problems related to the myriad of coliform sources within those communities. This study comprehensively investigated contamination sources and the biological and chemical mechanisms sustaining them in two adjacent communities in rural Limpopo, South Africa. An 8-month study was conducted of household ($n=14$) and source water quality, measurements of biofilm layers on the inside of household water storage containers and water transfer devices, and also hand-based coliforms and hand-washing effectiveness. A 7-day water container incubation experiment was also performed to determine the biological and chemical changes that occur in a household water storage container independent of human interference. Results indicate that household drinking water frequently becomes contaminated after collection but before consumption (197 versus 1,046 colony-forming $\mathrm{units}/100\mathrm{mL}$; $n=266$; $p<0.001$). The most important contamination sources include biofilm layers on the inside of storage containers ($1.85\pm 1.59$ colony-forming ${\mathrm{units}/\mathrm{cm}}^2$; $n=44$), hands ($\mathrm{5,097}\pm \mathrm{2,125}$ colony-forming $\mathrm{units}/\mathrm{hand}$; $n=48$), and coliform regrowth resulting from high assimilable organic carbon (AOC) levels during storage. A maximum specific growth rate, ${\mu }_{\max }$, of $0.072\pm 0.003{\mathrm{h}}^{-1}$ was determined for total coliform bacteria on AOC, and a high correlation between AOC concentrations and the growth potential of total coliform bacteria was observed. These results support the implementation of point-of-use water treatment and other interventions aimed at maintaining the safe water chain and preventing biological regrowth.

Hybrid poplar trees are known to take up trichloroethylene (TCE) into above ground tissues, where it degrades into the metabolites trichloroacetic acid (TCAA), dichloroacetic acid, and trichloroethanol and where parent chlorinated solvents volatilize to the atmosphere. Based on this knowledge, numerous phytoremediation applications have been implemented for TCE and other chlorinated solvents. Sampling of plant tissues has proven effective for phytoforensic and phytoscreening applications in assessing sites and evaluating the efficacy of phytoremediation. However, little is known about the appropriate exposure times and sampling locations required to obtain an accurate assessment of TCE and metabolites. In this study, hybrid poplars were dosed under greenhouse conditions for times ranging from one hour to 29 weeks. No increasing accumulation of TCE occurred in the stems over the time periods; however, concentrations decreased with increasing stem height in all cases. The concentration of TCAA throughout the plants’ leaves fluctuated along the stem rather than following a decreasing pattern with height. However, as a result of its nonvolatile characteristics, TCAA did accumulate to higher concentrations in the leaves over the given time periods. These results revealed that sampling TCE in the lower stem/trunk was ideal, but TCAA concentrations varied across locations; thus, sampling of multiple leaves is appropriate for an accurate determination of accumulative contaminant uptake. Used together, these methods offer a novel monitoring tool, which is needed because phytoremediation does not offer traditional monitoring means such as treated effluent to assess fate and efficacy. Knowledge resulting from this research can improve monitoring and reduce long-term monitoring costs for chlorinated solvent sites.

Glass beads embedded in pavement markings provide retroreflectivity to ensure safe driving. Recently, elevated concentrations of arsenic (As), antimony (Sb), and lead (Pb) have been observed in glass beads imported to the US. After an initial assessment of total concentrations in glass beads, a factorial study was conducted to determine the impact of environmentally relevant factors on leaching: pH (4, 7, and 10), chemicals applied on roadways (NaCl, ${\mathrm{CaCl}}_2$, ${\mathrm{KCH}}_3\mathrm{COO}$, and KCl), ionic strength (${10}^{-2}–{10}^{-1}\mathrm{M}$), particle size ($>100$ and $<37\mathrm{\mu m}$), and time (18 h to 160 days). Additional leaching studies included the US EPA toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP). Results demonstrated that the most important factors affecting leaching were pH and time. For anions of As and Sb, leaching tended to increase with increasing pH, whereas for the cation Pb, leaching increased as pH decreased. As expected, leaching increased with a decrease in particle size. Although the TCLP results revealed greater leaching than the SPLP, concentrations were one to two orders of magnitude less than concentrations observed in the factorial experiments.

In this study, an inexact chance-constrained waste-load allocation (ICWA) model is proposed for supporting river quality management under uncertainty that is capable of addressing uncertainties expressed as intervals and probability distributions as well as analyzing the reliability of satisfying (or the risk of violating) various constraints. The ICWA model is then applied to water quality management of the Xiangxihe River in the Three Gorges Reservoir Region, which faces severe water quality problems due to point and nonpoint source pollution. The results demonstrate that higher biological oxygen demand (BOD) discharge amounts are observed at the Baishahe chemical plant and Gufu wastewater treatment plant. Moreover, total phosphorus discharges into the river come mainly from point sources, particularly the chemical plants and phosphorus mining companies. For nonpoint sources, crop farming generates large amounts of total phosphorus and total nitrogen. Tradeoffs between economic benefits and system-failure risks are also examined. Alternatives can be obtained from different combinations of decision variables within their lower and upper bounds, which are valuable for decision makers, who need to develop the desired regional economic plans while satisfying environmental requirements.

Piggery effluent is one of the most highly produced wastewaters throughout the world, containing high levels of inorganic nutrient species. In this study, a microalga Scenedesmus obliquus YSW-14 (S. obliquus) was employed not only for nutrient removal from piggery wastewater effluent but also for lipid accumulation in the algal biomass as a feedstock for biofuel production. The piggery wastewater effluent was diluted up to fivefold with synthetic media to reduce the toxicity of (in)organic components, which resulted in improved microalgal growth, nutrient removal, and lipid productivity. Among the examined culture conditions, a 40% concentration of wastewater effluent was found to be most effective for microalga lipid productivity ($0.13\mathrm{mg}{\mathrm{L}}^{-1}$). S. obliquus removed 155 mg total nitrogen and 4 mg total phosphate per gram of dried algae for growth at the same dilution condition. These results demonstrate the feasibility of using microalgae for advanced wastewater treatment and subsequent production of lipids as biofuel feedstock.

Foam is potentially a promising vehicle to deliver nanoparticles for vadose-zone remediation because foam can overcome the intrinsic problems associated with solution-based delivery, such as preferential flow and contaminant mobilization and spreading. In this work, the feasibility of using foam to deliver nanoscale zero valent iron (nZVI) in unsaturated porous media was investigated. Foam generated using the surfactant sodium lauryl ether sulfate (SLES) showed excellent ability to carry nZVI. SLES and nZVI concentrations in the foaming solutions did not affect the percentages of nZVI concentrations in foam relative to nZVI concentrations in the solutions. When foams carrying nZVI were injected through the unsaturated columns, the fractions of nZVI exiting the column were much higher than those when nZVI was injected with liquid. The enhanced nZVI transport implies that foam delivery could significantly increase the radius of influence of injected nZVI. The type and concentrations of surfactants and the influent nZVI concentrations did not noticeably affect nZVI transport during foam delivery. In contrast, nZVI retention increased considerably as the grain size of porous media decreased. Oxidation of foam-delivered nZVI due to oxygen diffusion into unsaturated porous media was visually examined in flow cell texts. It was demonstrated that if foam is injected to cover a deep vadose-zone layer, oxidation would only cause a small fraction of foam-delivered nZVI to be oxidized before it reacts with contaminants.

This investigation examines use of the electrokinetic (EK) technique in the remediation of low-permeability soil that is contaminated with pentachlorophenol (PCP). The EK system, which includes an electrolyte injection system, improves the efficiency of removal and the degradation of PCP, and performs dechlorination. Experimental results reveal that the species of electrolyte influences the generation of the electric current, the pH of the electrolyte, the pH of the soil, and the rate of electroosmotic flow (EOF). The latter influences the efficiency of remediation of the contaminated soil. Following 72 h of treatment, the overall PCP removal rates that were achieved using NaOH, tap water, and ${\mathrm{Na}}_2{\mathrm{SO}}_4$ electrolytes were 81.74, 11.47, and 29.81%, respectively. In this study, the obtained electroosmosis permeability ($K_{eo}$) values, ranging from $4.52\times {10}^{-5}$ to $6.17\times {10}^{-5}{\mathrm{cm}}^2/\mathrm{Vs}$, were considerably higher than the values of typical hydraulically induced flow in soil. After 48 (T2) and 72 (T3) h of treatment with NaOH as the electrolyte, the total energy consumption was 492 and $582\mathrm{kWh}/{\mathrm{m}}^3\text{-}\mathrm{soil}$, respectively. The energy consumption per unit mass of PCP removed revealed that T3 ($14\mathrm{kWh}/\mathrm{g}\text{-}\mathrm{PCP}$) was associated with a more efficient use of energy and the results for T2, T4, and T5 indicate that using NaOH as the electrolyte improved the removal efficiency, saved energy, and reduced the processing time. An evaluation of cost-effectiveness indicates that an EK system that included an electrolyte injection system and used NaOH as the electrolyte provided a favorable removal efficiency and rate of degradation of PCP.

This study investigated the biodegradation of synthetic wastewater containing 2,4,6-trichlorophenol (TCP) in a sequencing batch-fluidized bed bioreactor (SBFBBR) with waste coke particles (WCPs) as the biofilm carrier. The irregular surfaces of WCPs (diameter range from 0.6 to 2.3 mm) rendered them ideal biomass carriers. The attached biomass was 4.0–4.5 mg volatile suspended solids $(\mathrm{VSS})/\mathrm{g}$ WCPs 3 weeks after reactor start-up, and the biofilm thicknesses were 35–110 μm. Biodegradation, not adsorption-degradation or volatilization-degradation, was found to be the main TCP removal mechanism. At the initial chemical oxygen demand (COD) concentration of $300\mathrm{mg}{\mathrm{L}}^{-1}$, removal of COD was more efficient and faster than that of TCP. The air-water ratio (ranging from 0.280 to $0.58{\min }^{-1}$) exerted negligible effects at dissolved oxygen (DO) concentrations above $2\mathrm{mg}{\mathrm{L}}^{-1}$. Maximum TCP degradation (62.1% after 3 h retention time and 75.8% after 6 h) occurred at initial COD concentration of $45\mathrm{mg}{\mathrm{L}}^{-1}$. TCP can be removed by biofilm as a sole source of carbon and energy. Furthermore, the TCP biodegradation follows zero-order reaction kinetics, with the zero-order specific biodegradation rate dependent on initial COD concentration.

Experimental evidence shows that the electrokinetic Fenton process is very effective for cleaning soil contaminated with organic compounds, especially hydrophobic and persistent organic pollutants. Despite the technological progress in recent years, there are still several performance-related issues to be addressed, such as its implication on the final soil quality and different oxidant delivery schemes. This paper reports the results of a series of experiments carried out to explore the possibilities of using polarity reversal as an enhancement during electrokinetic Fenton treatment of soil contaminated with persistent organic pollutants. Laboratory-scale experiments were conducted with kaolin and hexachlorobenzene (HCB) as the model soil and contaminant, respectively. Experiments were performed both with and without added iron (Fe). Reversing the polarity of electrodes after a period during the experiments was found to be effective in aiding the reachability of the oxidant to the soil specimen in a shorter duration. An overall HCB removal of 10% in 10 days was increased to 33% with one polarity reversal during the treatment. However, its use with different oxidant delivery methods is to be considered carefully, because it was observed that the addition of hydrogen peroxide (${\mathrm{H}}_2{\mathrm{O}}_2$) from the anode chamber was crucial for HCB degradation to occur.

Rain gardens are implemented to mitigate runoff volume and associated pollutants to restore the health of a watershed. Rain gardens reduce runoff volume through infiltration and improve water quality as pollutants are filtered through soil media. Infiltration rates, however, can be reduced as a result of soil compaction. Knowledge about the factors that control compaction in rain gardens is currently limited, and studies are lacking on the ability of rain gardens to infiltrate runoff over a long-term period. Twenty-six rain gardens in New Jersey were evaluated during the summers of 2010 and 2011. Depth to soil compaction was measured in the field, and soil texture, site information, and oxidation-reduction potential data were collected to compare different ages of rain gardens with various soil types. There was no significant difference in soil compaction between surveys based upon the age of the rain gardens, but soil texture was found to have an influence on compaction levels. This knowledge will help to provide information on the care and maintenance of rain gardens and will help to alleviate soil compaction and increase infiltration.