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The storage lagoon of a land treatment system functions as a dynamic biological reactor in which algae and bacteria can transform input nitrogen. A quantitative estimate of these nitrogen transformations is needed for proper design of the... more
The storage lagoon of a land treatment system functions as a dynamic biological reactor in which algae and bacteria can transform input nitrogen. A quantitative estimate of these nitrogen transformations is needed for proper design of the spray irrigation component of land treatment. In this study, a simulation model was developed to predict the concentrations of inorganic and organic nitrogen and algae in the lagoon throughout the winter storage and irrigation months; pilot plant data were used for verification. Both the predicted and observed results indicated a large reduction in inorganic nitrogen caused by algal uptake during most of the irrigation period. The model was then applied to achieve a better balance between nitrogen supplied by the lagoon and crop demand throughout the growing season.
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The reuse of municipal wastewater is becoming increasingly popular in many areas of the United States, especially those areas where clean, fresh water is in high demand. Reclaimed wastewater can be a valuable resource in applications... more
The reuse of municipal wastewater is becoming increasingly popular in many areas of the United States, especially those areas where clean, fresh water is in high demand. Reclaimed wastewater can be a valuable resource in applications where less than potable water quality is sufficient. The City of Washington, North Carolina and the National Spinning Company, Inc. are considering a unique wastewater reuse scheme. Upon upgrading of the wastewater facility at the City of Washington with a denitrification filter, it is proposed that 1.3 million gallons per day (mgd) of tertiary treated wastewater be routed for use as process water in textile dyeing operations. The reclaimed wastewater would be stored at two abandoned City of Washington clearwells prior to use by National Spinning Company. A pilot-plant was constructed at the University of North Carolina at Chapel Hill to simulate the City of Washington treatment plant upgrade and the present process water treatment scheme at the Nationa...
Research Interests: Engineering, Waste Management, Wastewater, Spinning, Dyeing, and 3 moreSouth Carolina, Textile, and Reuse
Abstract: The biosand filter (BSF) is an intermittently operated, household-scale slow sand filter for which little data are available on the effect of sand composition on treatment performance. Therefore, bench-scale columns were... more
Abstract: The biosand filter (BSF) is an intermittently operated, household-scale slow sand filter for which little data are available on the effect of sand composition on treatment performance. Therefore, bench-scale columns were prepared according to the then-current (2006–2007) guidance on BSF design and run in parallel to conduct two microbial challenge experiments of eight-week duration. Triplicate columns were loaded with Accusand silica or crushed granite to compare virus and E. coli reduction performance. Bench-scale experiments provided confirmation that increased schmutzdecke growth, as indicated by decline in filtration rate, is the primary factor causing increased E. coli reductions of up to 5-log10. However, reductions of challenge viruses improved only modestly with increased schmutzdecke growth. Filter media type (Accusand silica vs. crushed granite) did not influence reduction of E. coli bacteria. The granite media without backwashing yielded superior virus reduction...
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Nanofiltration membranes (with pore sizes on the order of 10 -9 m) have been shown in pilot plant studies to provide a very effective means of removing natural organic matter (NOM). Removal of NOM from product water results in... more
Nanofiltration membranes (with pore sizes on the order of 10 -9 m) have been shown in pilot plant studies to provide a very effective means of removing natural organic matter (NOM). Removal of NOM from product water results in accumulation of rejected species which may foul the membrane. Frequency and intensity of cleaning, as well as the useful life of membranes, are important process optimization issues which cannot be resolved until membrane fouling by NOM is better understood. In this research we report that the concentration and composition of NOM and cross flow velocity are important factors in affecting the rate of fouling; in addition, fouling must be measured not only by permeate flux decline but also by permeate water quality.
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While several physical-chemical processes are currently available for ammonia removal, each has limitations. Ammonia stripping at high pH is unattractive in cold climates be cause of tower freezing problems; in addition, formation of... more
While several physical-chemical processes are currently available for ammonia removal, each has limitations. Ammonia stripping at high pH is unattractive in cold climates be cause of tower freezing problems; in addition, formation of CaC03 scale presents cleaning problems. Ion exchange, using clinoptilolite, also requires stripping of a concentrated am-, monia waste. Breakpoint chlorination, used for many years in treatment of potable water, requires high chlorine dosages for wastewater treatment and may produce toxic chloramines which pass into the receiving stream. A promising alternative for physical-chemical ni trogen removal is chlorination followed by activated carbon contact. This process can readily treat both municipal and industrial waste shock loads and is unaffected by cold weather conditions. In contrast to breakpoint chlorination, less chlorine is required, toxic chloramines are eliminated and the degree of ammonia removal can be controlled. The obvious application of ...
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Characterizing the rate of chloramine loss at pipe surfaces is crucial for predicting the rate of decay within the distribution system (DS). Chloramines in finished water are relatively stable, yet they do autodecompose. However,... more
Characterizing the rate of chloramine loss at pipe surfaces is crucial for predicting the rate of decay within the distribution system (DS). Chloramines in finished water are relatively stable, yet they do autodecompose. However, significant loss of stability can occur in the DS where interaction with pipe surfaces is a major source of chloramine loss. Myriad factors complicate in situ measurement of the surface reaction rate including spatially varying pipe material, age, and condition, as well as temporally varying hydraulics. In this study, a bench‐scale, pipe section reactor was used to determine chloramine surface reaction rate constants for cementlined ductile‐iron pipe and tuberculated, unlined cast‐iron pipe. Chloramine decay was found to be first order for both of these pipe materials. Surface reaction rates were calculated by accounting for the influence of water velocity on mass transfer of chloramine to the pipe surface, and therefore the overall chloramine decay rate. T...
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The case study for evaluating the EPA Toxicity Identification Evaluation protocol was a textile dye manufacturing plant that suspected chloride as the major source of toxicity. Phase I of the protocol, together with some additional... more
The case study for evaluating the EPA Toxicity Identification Evaluation protocol was a textile dye manufacturing plant that suspected chloride as the major source of toxicity. Phase I of the protocol, together with some additional experiments, was successful in showing that one-third to one-half of the toxicity was due to chloride and the rest was due to nonpolar organic compounds. From 41 to 78 organic chemicals were found in toxic fractions using the EPA Phase II test procedures; these included dyes, dye intermediates, process chemicals such as surfactants and possibly metabolic by-products of waste treatment. A major component of Surfynol, a widely used surfactant, was present in concentrations much higher than any other chemical in the toxic fractions of all three samples analyzed. However, the concentration was still considerably less than the LC50 (mg/L) and thus could not explain whole effluent toxicity. Instead, more than one organic chemical may be involved.
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A discussion of the state-of-the-art of controlling and predicting adsorber performance covers published experimental and theoretical studies on competitive adsorption, e.g., phenol-dodecylbenzenesulfonate, p-nitrophenol/benzoic acids,... more
A discussion of the state-of-the-art of controlling and predicting adsorber performance covers published experimental and theoretical studies on competitive adsorption, e.g., phenol-dodecylbenzenesulfonate, p-nitrophenol/benzoic acids, and p-nitrophenol/phenol; the potential for simplifying models for predicting competitive adsorption; the interaction between adsorption biodegradation on granular activated carbon (GAC) beds; and the effects of pretreatment, e.g., prozonation, prechlorination, and biological oxidation, on the performance of GAC adsorbers.
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The effect of diet on the health and robustness of Ceriodaphnia dubia was investigated. C dubia were raised on three diets for 19 generations to evaluate survival and reproduction. The three diets used to culture C. dubia were... more
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The effect of diet on the health and robustness of Ceriodaphnia dubia was investigated. C dubia were raised on three diets for 19 generations to evaluate survival and reproduction. The three diets used to culture C. dubia were the EPA‐recommended one containing the green alga, Selenastrum capricornutum, plus a mixture of yeast, cereal leaves (Sigma Chemical), and trout chow (YCT); one containing the green alga, Chlamydomonas reinhardtii, plus YCT; and one with a combination of the two species of algae plus YCT. C. dubia also were subjected to various copper concentrations to evaluate the relative sensitivity to toxicants of animals raised on different diets.
The levels of survival and reproduction of C. dubia raised on all three diets satisfied the both the EPA and North Carolina Division of Environmental Management Mini‐chronic Pass/Fail Ceriodaphnia Effluent Toxicity Test minimum standards for control animals used in a chronic toxicity test. Survival was not significant...
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New fluorine containing polymer materials, which contain n-fluoro octylacrylate (pFOA) or n-fluorooctylmethylacrylate (pFOMA) repeating units, are being explored for use in thin film composite membranes in treatment of drinking water.... more
New fluorine containing polymer materials, which contain n-fluoro octylacrylate (pFOA) or n-fluorooctylmethylacrylate (pFOMA) repeating units, are being explored for use in thin film composite membranes in treatment of drinking water. These polymers both have extremely low surface tension which should prevent the accumulation of foulant materials from water. However, they need to be chemically linked with a hydrophilic polymer, e.g. vinyl alcohol, in order to produce hydrophilic regions that span the entire sample thickness and thus form channels for water permeation. Such a microphase-separated structure can be controlled through the process of block copolymer synthesis. The initial findings from synthesis and characterization of copolymers and formation of thin-film composite membranes are presented.
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... Membrane Characterization and Membrane Material Optimization. by Francis A. DiGiano , M.ASCE , Benny Freeman , Michelle Arnold , Jack Preston , Kazukiyo Nagai , and Anna Roudman pp. 217-226 Purchase Information Permissions for Reuse ...
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Several modifications to conventional uses of passive dosimetry in industrial hygiene were explored to make the method attractive for both long-term monitoring of underground storage tanks and short-term site assessments of ground water... more
Several modifications to conventional uses of passive dosimetry in industrial hygiene were explored to make the method attractive for both long-term monitoring of underground storage tanks and short-term site assessments of ground water contamination. Methods for both vapor and aqueous phase measurements were of interest. In addition, a colorimetric method was tried to eliminate the need for return of the dosimeter to the laboratory for chemical analysis. The results suggest that passive dosimetry can be a useful qualitative tool for the mapping of the sub-surface of a contaminated area. It is recommended that the dosimeter be used for short-term site-assessments, rather than long-term compliance monitoring applications. A more extensive comparison with other methods of leak detection than was possible in the research may be needed before convincing the private sector to develop a product based on commercial use of these prototype dosimetry devices.
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New buildings increasingly incorporate advanced water conservation features and use of grey water and recycled water for non-potable purposes. Recent experiences highlight the negative impact of these sustainable practices on water... more
New buildings increasingly incorporate advanced water conservation features and use of grey water and recycled water for non-potable purposes. Recent experiences highlight the negative impact of these sustainable practices on water quality at the tap. Water residence time in building plumbing can increase markedly, causing microbial growth, taste and odor problems, and elevated lead. In our experience, at some locations
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Granular activated carbon (GAC) in filter-adsorbers provides an excellent support surface for the proliferation of microorganisms. Therefore, GAC beds may release particles of carbon with attached bacteria that are protected from... more
Granular activated carbon (GAC) in filter-adsorbers provides an excellent support surface for the proliferation of microorganisms. Therefore, GAC beds may release particles of carbon with attached bacteria that are protected from disinfection. In this pilot-plant study, particles were collected from the product waters of GAC filter-adsorbers, examined for bacterial colonization, and characterized by energy-dispersive X-ray analysis. Results showed that bacteria
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The characterization of trihalomethane (THM) precursors and their eventual removal from water are elusive goals. Conflicting and highly variable results exist. Precursors of THMs were examined by sampling humic substances from three... more
The characterization of trihalomethane (THM) precursors and their eventual removal from water are elusive goals. Conflicting and highly variable results exist. Precursors of THMs were examined by sampling humic substances from three regions in Massachusetts with dissimilar ...
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ABSTRACT Biological activity on granular activated carbon (GAC) may significantly enhance the treatment process. Shifting the pathway for contaminant removal from adsorption to biodégradation reduces biodegradable organics and increases... more
ABSTRACT Biological activity on granular activated carbon (GAC) may significantly enhance the treatment process. Shifting the pathway for contaminant removal from adsorption to biodégradation reduces biodegradable organics and increases sorptive capacity for nondegradable or slowly degradable compounds. Biodegradation and adsorption of natural organic matter (NOM) were studied in a laboratory-scale GAC reactor. Ozonation was found to encourage biofilm growth and biodégradation of NOM. Biofilm organisms grown on ozonated NOM readily degraded trace concentrations of phenol. La actividad biológica en el carbón granular activado (GAC) puede mejorar en forma muy significativa el proceso del tratamiento. El cambio de la ruta de la remoción de contaminantes desde adsorpción hasta biodegradación reduce la materia orgánica biodegradable y aumenta la capacidad de adsorción de los compuestos no degradables o lentos. La biodegradación y adsorción de la materia orgánica natural (NOM) fue estudiada en un reactor de GAC a escala de laboratorio. Se encontró que la ozonización estimula el crecimiento de biopelículas y la biodegradación del NOM. Los organismos biopeliculares creados en un NOM ozonizados fácilmente degradan el fenol.
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... 1996., 1996. The book consists of twelve chapters focusing on various aspects of process dynamics. It begins with an overview of the subject and a formulation of the approach to process engineering that we use throughout the book. ...
ABSTRACT A simple laboratory test, referred to here as the dredging elutriate test (DRET), was sought to predict the concentration of contaminants in the water column at the point of dredging. The DRET is procedurally similar to the... more
ABSTRACT A simple laboratory test, referred to here as the dredging elutriate test (DRET), was sought to predict the concentration of contaminants in the water column at the point of dredging. The DRET is procedurally similar to the modified elutriate test developed by the US Army Corps of engineers to predict concentrations of contaminants at the point of disposal of dredge material. The objective of experimentation was to investigate the release of dissolved and suspended polychlorinated biphenyls (PCBs) as a function of initial concentration of sediment, aeration time, and settling time in the DRET. Settling time was found most important. Field data from a pilot dredging project in New Bedford Harbor, Massachusetts compared well to results of the DRET. Most of the PCB in the field and DRET were sorbed to small particles rather than dissolved. A good correlation was obtained between total PCB and total suspended solids. A sorption equilibrium model based on available partition coefficients described the sorbed-dissolved PCB distribution. Particle size distribution analysis showed that the mean diameter was less than 10 [mu]m after just 0.5 h of settling and decreased very little with further settling. These particles and their PCB burden have the potential to be transported away from a dredging site.
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ABSTRACT The effects of solution chemistry, surface shear, and composition of natural organic matter (NOM) were investigated for their impact on accumulation of foulant material at the surface of charged polymeric nanofiltration... more
ABSTRACT The effects of solution chemistry, surface shear, and composition of natural organic matter (NOM) were investigated for their impact on accumulation of foulant material at the surface of charged polymeric nanofiltration membranes. The source of NOM was the Suwannee River. A bench-scale, batch recycle system was used with 20 hollow fiber, nanofiltration membranes. Membrane flux decline and foulant accumulation increased at low pH and high ionic strength as a result of neutralization of charge, electric double layer compression, and the apparent shift in conformation of charged NOM macromolecules. The rate of NOM accumulation decreased with operating time, suggestive of an eventual steady state between adsorption and desorption. The effect of NOM composition on membrane fouling could not be discerned by a standard technique to isolate hydrophobic and hydrophilic NOM fractions, quite possibly because of the fractionation methodology's failure to recover a small but important fouling fraction or because of NOM interactions that are lost when individual fractions are separately tested. However, a greater percentage of the hydrophilic than hydrophobic fraction permeated the membrane, in agreement with prior observations by others. Increasing the cross flow velocity from 85 to 255 cm/s reduced the extent of flux decline, presumably due to hydrodynamic disruption of cake layer formation.
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At the time the study was initiated, Jordan Lake was being considered as a source of municipal drinking water by several communities in the central Piedmont of N.C. This research project evaluated three treatment scenarios for Jordan Lake... more
At the time the study was initiated, Jordan Lake was being considered as a source of municipal drinking water by several communities in the central Piedmont of N.C. This research project evaluated three treatment scenarios for Jordan Lake water. The first consisted of conventional coagulation, sedimentation, and filtration, followed by chlorination. The other two involved advanced treatment schemes, one incorporating
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ABSTRACT The removal of contaminated sediments from waterways by dredging generates concern about the release of contaminants to the water column. The ability to predict the magnitude of these potential releases during the project... more
ABSTRACT The removal of contaminated sediments from waterways by dredging generates concern about the release of contaminants to the water column. The ability to predict the magnitude of these potential releases during the project planning process will improve decision making in regard to water quality impacts and controls or mitigation measures for the dredging project. This report describes the development of a simple laboratory test, the dredging elutriate test (DRET), to predict the concentration of contaminants in the water column at the point of dredging. The DRET is procedurally similar to the modified elutriate test developed by the Corps of Engineers to predict the contaminant concentrations in effluent from a confined disposal facility. The test involves mixing sediment and site water, allowing the heavier solid particles to settle, sampling and supernatant, and analyzing for dissolved and particulate bound contaminants. Results of the laboratory test compared well with field data collected while dredging New Bedford Harbor sediment, which was contaminated with polychlorinated biphenyls. Most of the contaminated loading was associated with the suspended particles.
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ABSTRACT The U.S. Department of energy (DOE) is actively pursuing new and improved separation techniques for the cleanup of past nuclear defense production sites. Research and production activites at DOE`s Hanford Site in Richland, Wash.,... more
ABSTRACT The U.S. Department of energy (DOE) is actively pursuing new and improved separation techniques for the cleanup of past nuclear defense production sites. Research and production activites at DOE`s Hanford Site in Richland, Wash., have created large volumes of waste streams containing hazardous and toxic chemicals along with radioactive materials. Many of these wastes will require processing for segregation into high-level, transuranic, and/or low-level waste for permanent disposal. A process to selectively remove actinides, such as americium, from liquid radioactive waste was investigated for potential use at Hanford and other contaminated DOE sites. The objective of this research was to determine the effectiveness of polymer binding followed by ultrafiltration for removal of europium (Eu), a nonradioactive surrogate for trivalent actinides such as americium. A commercially available polyacrylic acid (PAA) and a Pacific Northwest Laboratory (PNL) synthesized copolymer were tested. Both polymers significantly increased Eu removal. A cation exchange mechanism was implied by examination of the Eu-to-RCOââ» functional groups that comprise the acrylic acid monomer. The weight ratios of Eu-to-polymer needed to achieve 85% rejection of Eu were 1:6 for PAA and 1:10 for the PNL copolymer. Addition of sodium to the feed solution at a concentration three orders of magnitude greater than Eu did not adversely affect rejection of Eu. 12 refs., 12 figs., 4 tabs.