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Environmental Engineering and Science
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NOTE: Applied Research and Practice is published as part of Environmental Engineer and Scientist, the Quarterly Periodical of the American Academy of Environmental Engineers and Scientists™. All journals are copyrighted by the American Academy of Environmental Engineers and Scientists™. All rights are reserved. No part of any journal paper obtained may be reproduced or distributed in any form or by any means without the prior written permission of the American Academy of Environmental Engineers and Scientists™. By downloading a journal, you agree to these terms.
Definition of source and plume architecture at heterogeneous and homogeneous dense non-aqueous phase liquid (DNAPL) sites is highly complex and requires a detailed characterization approach. The membrane interface probe (MIP) can be used at many sites to perform cost-effective, detailed investigations. The MIP is a commercially available tool that has been described by the manufacturer as a semi-quantitative tool, by others as a quantitative tool, and yet others as a qualitative tool. A variety of methods have been used in an attempt to establish correlations between MIP data and environmental media concentration data. Application of a spatial correlation approach at two sites resulted in the development of semi-quantitative relationships between MIP data and environmental media concentration data, which were used to define volumes of impacted media that exceed applicable regulatory thresholds.
Access to a sufficient quantity of high quality water is important for improving health and economic livelihood of people residing in developing countries. The purpose of this paper is to identify some of the technical, economic, and social barriers to implementing drinking water technologies in these countries. The intent is to provide guidance to practitioners regarding the barriers and to assist development of strategies for successful implementation. Four representative regions and six water purification technologies were selected for this study. Information on engineering attributes and cost for these technologies were collected and evaluated. A survey of U.S. Peace Corps Volunteers was conducted to understand current practice in developing world countries. Successful implementation of technology in developing world countries requires it be culturally and economically appropriate. Also, it is very important to provide water and sanitation education to local communities before implementing the technologies so families understand the interaction between clean water, sanitation, and improved health.
The solvent stabilizer 1,4-dioxane has emerged in the environmental engineering arena as an unexpected and recalcitrant groundwater contaminant at many sites across the US. Decreases in the analytical detection limit in water have revealed the presence of this contaminant in sites where no 1,4-dioxane was identified during earlier, higher MDL sampling events. Toxicological studies suggest that 1,4-dioxane may be harmful, and it has been designated as a probable human carcinogen. However, the toxicity of 1,4-dioxane is in dispute and the United States Environmental Protection Agency is in the process of reviewing the toxicological information on 1,4-dioxane towards potentially revising the oral cancer slope factor and associated risk screening levels. Chemical characteristics of 1,4-Dioxane, such as high mobility, enable it to migrate much further than the solvent from which it likely originated. This has challenged remedial project managers to redesign treatment systems and monitoring networks to accommodate widespread contamination. This paper summarizes the fate and transport characteristics of 1,4-dioxane and presents current thinking in the environmental engineering community related to remedial technologies that may be applicable to groundwater treatment. At this point in time, ex-situ remediation has been performed at numerous sites for 1,4-dioxane, but no full scale in-situ remediation projects have been completed.
Because brewery wastewater is limited in nitrogen, biological treatment by an activated sludge process requires supplemental ammonia for a healthy biomass with good settling properties. Control of effluent ammonia while still meeting biomass nutritional requirements is an operational challenge. Nitrogen mass balances of the Coors Golden Brewery wastewater based on ammonia indicate that the biomass is generally nitrogen deficient, with total organic carbon:nitrogen ratios ranging from 16:1 to 103:1, significantly higher than the optimum 10:1. At the same time, total Kjeldahl nitrogen of the sludge is about 10% nitrogen by weight, indicating adequate nitrogen levels for healthy metabolism. Total and soluble Kjeldahl nitrogen of the wastewater show significant levels of organic nitrogen, which appears to be metabolized by the biomass. The Simulation of Single Sludge Processes (SSSP) software was used to improve understanding of nitrogen sources and utilization in the pure oxygen activated sludge process, and thus improve control of ammonia supplemental feeding and effluent quality. Various operating strategies were evaluated, such as step feed, adjustment of nitrogen feed and varying sludge age. Brewery wastewater streams from malting, packaging, brewing, fermenting, and yeast drying, were characterized and applied to the model to determine differences in supplemental nitrogen needs.
Seawater desalination plants produce concentrate (brine) which is usually 1.5 to 2 times higher than the concentration of total dissolved solids (TDS or salinity) of the ambient seawater. When returned to the ocean without dilution, the concentrate may have negative impact on the aquatic environment in the area of the discharge. This impact is very site-specific and depends to a great extent on the salinity tolerance of the specific marine organisms inhabiting the water column and benthic environment influenced by the discharge. The existing US EPA whole effluent toxicity (WET) tests are indicative of the level of salinity which causes mortality of pre-selected test organisms, which may or may not inhabit the discharge area. This work presents a novel method that allows establishing the site-specific maximum level of salinity concentration (salinity tolerance threshold) at which marine organisms not only survive, but can also grow and reproduce normally. The described method was used successfully for the permitting of the concentrate ocean discharge of two large seawater desalination projects in California -- the 189,000 m3/day (50 MGD) Carlsbad and Huntington Beach desalination plants.
Nitrogen removal in wastewater treatment can be achieved by introducing anoxic zones in biological reactors within an activated sludge process, operating at medium or long mean cell retention time (MCRT). Anoxic zones at the head of the process also function as biological selectors and provide benefits in addition to nitrogen removal, including improved stability by avoiding filamentous bulking, enhanced removal of many recalcitrant pollutants and reduced energy consumption due to the oxygen credit and higher oxygen transfer efficiency. Improved oxygen transfer occurs because the readily biodegradable organic compounds are used by the denitrifiers for nitrate reduction. These organic compounds, which are surfactants, would otherwise reduce oxygen transfer efficiency, increasing plant operating costs. We tested 22 treatment plants which included either conventional, nitrifying-only, or nitrifying-denitrifying (NDN) operations. Off-gas tests confirm that oxygen transfer efficiency for NDN operations is higher. Our economic analyses show that NDN operation can have the lowest aeration costs, contrary to long-standing beliefs. The net operating costs can be lower than conventional, short MCRT operation and are always lower than nitrifying-only operation. However, depending on the local plant situation, expansion of aeration volume and/or clarifier area might be necessary, and the operating savings could be offset by debt service on plant expansion.
Disinfection is a very important unit process to deactivate coliform bacteria in treated wastewater. However, regrowth potential of coliform bacteria raises human health and safety concerns associated with reuse of treated wastewater in various applications. Both post chlorination and post UV disinfection regrowth have been reported in the literature. In view of increasing use of recycled wastewater for reuse, it is necessary to address this phenomenon from both technical and regulatory standpoints. A case study of fecal coliform regrowth in a full scale operating plant is reported here. This is expected to aid in further understanding of the phenomenon and its causes so that proper technology may be selected on a case by case basis in the design of treatment plants. The results demonstrated that effectiveness of UV disinfection system is largely compromised by the presence of residual organics and color in the treated effluent.
The main objectives of this research were to determine the compounds associated with odors during the digestion and handling of biosolids and understand the process operational factors which impact the production of these odor causing compounds. To accomplish these goals, a comprehensive sampling of 11 full-scale wastewater utilities with anaerobic digestion was performed in which samples were collected from most locations throughout the liquid and solids processing scheme. The samples were analyzed for a number of inorganic and organic constituents such as metal concentration, anions, pH, temperature, and the samples were placed in sealed headspace bottles for headspace analysis of possible odor causing compounds. The results indicated that biosolids odors after dewatering were generally much higher than odors produced from other sample locations in a plant. A direct correlation was found between the sulfur compound concentration, especially the volatile organic sulfur compounds, and the dilution thresholds measured by an odor panel, indicating that sulfur compounds were a main contributor to odors. The main sulfur compounds measured included hydrogen sulfide, methanethiol, dimethyl sulfide, and dimethyl disulfide. The odor descriptors most frequently cited by the odor panel were "offensive" "putrid" "chemical" and "garbage". Few of the operational parameters were correlated with biosolids odorant production, such as influent wastewater characteristics, ratio of primary and secondary to digestion, and residual biosolids activity. Digester SRT was weakly, negatively correlated to the concentration of VOSCs produced during storage and no correlation was found between the percent volatile solids reduction and VOSCs.
To better define the knowledge and skills required for the practice of environmental engineering, the American Academy of Environmental Engineers (AAEE) sponsored a Body of Knowledge Working Group (BOKWG) to define the knowledge, skills and abilities needed to practice environmental engineering at the professional level. The Working Group adopted an outcomes based approach and identified 18 outcomes. Bloom's Taxonomy enhanced by the Daggett Rigor/Relevance Framework was used to identify the cognitive rigor and applicative relevance level expected for each outcome at the baccalaureate, masters (or equivalent) and after 4 or more years of professional experience. The Working Group Draft Report summarized here is undergoing a peer review by educators and practitioners. Comments are welcome and should be directed to Dr. Debra Reinhart at reinhart at mail.ucf.edu.
Greenhouse gas (GHG) emissions associated with production of desalinated seawater at the 50 MGD Carlsbad project in California are planned be mitigated by a portfolio of alternative technologies and measures including advanced energy reduction technologies, implementation of renewable energy projects, and carbon dioxide sequestration. This paper describes the methodology used to determine the carbon footprint for the Carlsbad desalination project and presents the scope and costs associated with the various GHG emission initiatives planned for this project.
Mitigation of ozone-induced bromate by carbon dioxide and chlorine/ammonia processes was studied at the Greenway Water Treatment Plant located in Peoria, AZ. Plant scale and bench-scale testing were performed to assess practicality and to determine the influence of source water on bromate formation, especially with respect to bromide concentrations. Results indicated that both of the approaches were able to reduce bromate yield by 35 percent or more depending on the raw water quality. Mitigation effectiveness depended on the ozone/TOC dosage, and at an O3/TOC ratio of 1.0 mg/mg, neither process was expected to reduce bromate formation below 8 μg/L on a consistent basis. Carbon dioxide addition appeared to perform slightly more consistently compared to the chlorine/ammonia process. However, based on other economic, social, and environmental considerations not discussed in this paper, the chlorine/ammonia process appeared to be the best alternative to mitigate bromate formation in order to allow higher ozone dosages and thereby enhance taste, odor, and TOC removal.
Removal of nitrogen from onsite sanitation water was demonstrated using three experimental two-stage biofiltration systems treating septic tank effluent (STE). Each system consisted of a vertical flow unsaturated trickle filter followed by a horizontal saturated denitrification filter with elemental sulfur as electron donor. Unsaturated filter media were clinoptilolite, expanded clay, and recycled granular rubber. The sole mechanical component of each filter was a single liquid pump that provided pressure dosing at a 30 min. interval and a hydraulic loading rate of 3 gallons per square foot per day (gal/ft2-day) (0.12 m/day). The systems were operated for over eight months on STE with an average total nitrogen (TN) concentration of 72.2 milligrams per liter (mg/L). The two-stage filters employing clinoptilolite, expanded clay and granular rubber media produced average final effluent TN of 2.2, 2.6 and 27 mg/L, respectively, with average TN removal efficiencies of 97, 96 and 65%. Dissolved organic nitrogen was the predominant form of nitrogen in treated effluent. Reduction of carbonaceous biochemical oxygen demand (CBOD) exceeded 94% for all three systems. The results demonstrated that the two-stage biofiltration design using a single pump was highly effective in reducing nitrogen in onsite sanitation water, and produced an effluent of comparable quality to centralized wastewater systems that employ external carbon dosing for tertiary denitrification.
This paper introduces concepts of sustainability with emphasis on the Natural Step principles. It describes the elements of an Environmental Management System (EMS) and discusses how an EMS can ensure sustainability by using portions of the Kent County (Delaware) Regional Wastewater Treatment Facility's (KCRWTF) Environmental Health and Safety Management Plan as an example. The KCRWTF is the first wastewater facility in the United States to be certified to the ISO 14001, OHSAS 18001, and the National Biosolids Partnership's EMS standards.
Recycled water must be properly disinfected to protect public health. The most widely practiced recycled water disinfection technology is chloramination. However, chloramines are precursors to the carcinogen N-nitrosodimethylamine (NDMA). To address this concern, engineers at the Sanitation Districts of Los Angeles County (Districts) developed the two-step "sequential chlorination" process. In the first step, free chlorine is added to fully nitrified secondary effluent to inactivate pathogens and to react with NDMA precursors, thus reducing subsequent NDMA formation. Chloramines are then added to media filtered effluent to stop formation of trihalomethanes (THMs) and haloacetic acids and to provide further disinfection.
The sequential chlorination process was extensively tested for disinfection efficacy and disinfection byproduct (DBP) formation in the laboratory, at the pilot scale, and at several water reclamation plants operated by the Districts. Results indicate that the process (1) provides effective disinfection against total coliform bacteria and viruses at chlorine contact times well below those required by California regulations for disinfected tertiary recycled paper; (2) reduces NDMA formation by 50 to 85% in comparison to chloramination; (3) produces effluent consistently meeting the total THM limit for recycled water; (4) generates insignificant amounts of cyanide (a DBP of concern); and (5) causes no aquatic toxicity.
Three case studies (Bolivia, Guyana, Florida) are presented that demonstrate how sustainability can be incorporated into environmental engineering education, research, and practice. They demonstrate how traditional measures of performance (e.g., function, economics, and safety) can be enhanced with additional measures of performance that integrate societal needs and a global perspective. The case studies also show how engineering practice can apply sustainability to an "engineering project" to transcend beyond the physical structure and include the social setting in which the project is located and importantly, the people who will operate, manage, and benefit from the project. This fits with the vision of the Environmental Engineering Body of Knowledge that "environmental engineering problem formulation and solution must be accomplished in the context of sustainability, must meet societal needs and must be sensitive to global implications." Furthermore, adding the learning outcomes of caring and a human dimension to education is critical if sustainability is to become inherent in all environmental engineering practice.
The aeration tanks at two Ohio wastewater treatment plants (Mill Creek and Upper Mill Creek) were investigated to improve phosphorus (P) removal. Although these plants were operated in modes conducive to biological P removal (BPR) and had high P removal efficiencies, they still had difficulty in consistently meeting their P discharge targets. Pilot-Scale Batch Reactors (PSBR's) were installed and fed mixed liquor from the head end of the aeration tanks to investigate the influence of anaerobic/anoxic and aerobic zones on BPR. The PSBR's were useful in investigating the influence of anaerobic/anoxic and aerobic zones on BPR. The results were used to recommend process modifications to improve BPR.
Phosphorus is well known to environmental engineers as an environmental issue because of its role in eutrophication of surface water. Environmental engineers tend to be concerned with how society interacts with its environment through its outputs (wastes). Sustainability is concerned with broader issues of our interaction with the environment, including both outputs and inputs (resources). (Environmental engineers have traditionally been involved with some inputs, notably water resources.) In the popular mind, sustainability is mostly about energy resources and global climate change. Environmental engineers are likely to add water resources to the list of concerns. But it is important to think more broadly in terms of material flow and life cycles to quantify inputs and outputs and to assess our ability to satisfy these needs indefinitely. This review examines phosphorus resources as an example of this broader view, and discusses ways in which environmental engineers may be well-poised to make contributions in dealing with the resulting challenges.
Over the past century, the federal environmental research laboratories located in Cincinnati, Ohio, have played a major role in advancing engineering knowledge and practice related to public health, water and wastewater treatment, and management of solid wastes and hazardous wastes. These efforts were aided by early state-sponsored research such as that at the Lawrence Experiment Station (McCracken and Sebian, 1988) in Massachusetts. As the knowledge base grew, the Federal management structure evolved from the United States Public Health Service (USPHS) to the Environmental Protection Agency (EPA). The purpose of this paper is to review and document some of the significant developments and achievements of the Cincinnati environmental research program from 1910 to 1980.
There is an emerging trend in urban stormwater management, as more and more major U.S. cities are considering green stormwater infrastructure to reduce stormwater impacts to their separate and combined sewers. "Green stormwater infrastructure" (GSI) is a term used to refer to a number of strategies for handling storm precipitation at its source, rather than after it has entered a sewer system. It often relies heavily on systems designed to infiltrate stormwater. The Philadelphia Water Department's (PWD) proposed Long Term Control Plan Update for Combined Sewer Overflow control calls for "greening" more than 40 percent of the city's impervious cover in the coming 25 years. This is the most ambitious use of GSI being proposed to date by a major U.S. city. Although GSI is being widely tested and implemented, urban applications at the scale at which Philadelphia proposes is unprecedented. One of the key concerns associated with urban GSI is the long-term impact of enhanced recharge on the groundwater table. PWD has examined rising groundwater table concerns using groundwater models. Models have been developed on the local level nearby proposed infiltration structures to assess groundwater mounding, as well as on a city-wide scale to assess the long-term impacts of the GSI program. Modeling shows that the water table could mound beneath the trench up to about 1 m following significant rain events; however, the mounding drops off quickly at distances of several meters from the infiltration facility and dissipates over several days. Keeping infiltration facilities more than 3 meters from nearby structures should avoid any problems with basement flooding. At full implementation of PWD's program, the groundwater table could eventually stabilize up to 1.5 meters higher than its current level in some areas of the city, but this would occur in areas where the groundwater table is more than 3 meters deep.
Sustainable solid waste management involves socially-acceptable solutions that minimize environmental impacts and cost, and incorporate waste minimization, recycling, treatment, and landfill disposal practices. This paper discusses the role of the landfill in sustainable waste management, including sustainable operation and design to control emissions, greenhouse gas issues, waste diversion, gas to energy opportunities, and a new concept, pump and treat aerobic flushing, for sustainable landfill operation to completion. Through these practices, landfills can promote safe waste disposal. Greenhouse gas emission offsets can be achieved through the collection and beneficial use of methane and carbon dioxide, in addition to the storage of recalcitrant carbon. Landfill-gas-to energy projects provide an opportunity for compensation for reduced gas emissions. However, it appears that reduction of emissions beyond current practice may not be cost effective because of the high cost of fugitive emissions avoidance.
This case study assesses the feasibility of a point-of-use (POU), nanomaterial-enabled photocatalytic water treatment device for use in rural areas in Swaziland. Small reservoirs provide water for irrigation and community consumption, but this water is highly contaminated with human and animal wastes. A prototype fluidized bed photoreactor—amended with nano-sized TiO2 coated on silica beads (60 wt%) and illuminated by UV light (254 nm, 18 W cm-2)—was capable of removing 99.9% of bacteria and viruses with less than 60 seconds of contact time. However, control tests showed that the majority of the disinfection was accomplished by UV light alone, with the photocatalytic material unable to significantly add to the disinfection at such short contact times. A potential benefit of using nano-sized TiO2 photocatalyst was the removal of a model pesticide (carbaryl) whose concentration was reduced by approximately 50% (compared to controls) with a contact time of 3 minutes. This research highlights the importance of POU water treatment systems, and demonstrates the potential feasibility and limitations of using nanotechnology-enabled small reactors to help relieve high water-related disease and mortality rates in developing countries.
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