Constructed wetlands are considered an inefficient technology for long-term phosphorus (P) removal. The P retention effectiveness of subsurface wetlands can be improved by using appropriate substrates. The objectives of this study were to: (i) use sorption isotherms to estimate the P sorption capacity of the two materials, masonry sand and light weight expanded shale; (ii) describe dissolved P removal in small (2.7 m3) subsurface flow wetlands; (iii) quantify the forms of P retained by the substrates in the pilot cells; and (iv) use resulting data to assess the technical and economic feasibility of the most promising system to remove P. The P sorption capacity of masonry sand and expanded shale, as determined with Langmuir isotherms, was 60 mg/kg and 971 mg/kg respectively. In the pilot cells receiving secondarily treated wastewater, cells containing expanded shale retained a greater proportion of the incoming P (50.8 percent) than cells containing masonry sand (14.5 percent). After a year of operation, samples were analyzed for total P (TP) and total inorganic P (TIP). Subsamples were fractionated into labile-P, Fe+Al-bound P, humic-P, Ca+Mg-bound P, and residual-P. Means and standard deviations of TP retained by the expanded shale and masonry sand were 349 + 169 and 11.9 + 18.6 mg/kg respectively. The largest forms of P retained by the expanded shale pilot cells were Fe+Al- bound P (108 mg/kg), followed by labile-P (46.7 mg/kg) and humic-P (39.8). Increases in the P forms of masonry sand were greatest in labile-P (7.5 mg/kg). The cost of an expanded shale wetland is within the range of costs conventional technologies for P removal. Accurate cost comparisons are dependent upon expansion capacity of the system under consideration. Materials with a high P sorption capacity also have potential for enhancing P removal in other constructed wetland applications such as stormwater wetlands and wetlands for treating agricultural runoff.

Thesis advisor: Noah P. Snyder / Dam removal is a widely used river restoration technique. Historically, dams produced hydropower, controlled flooding, and provided water storage, but currently many dams in the United States, specifically low head dams in New England, are obsolete. This study aims to assess the ability of a simple morphodynamic sediment transport model, Dam Removal Express Assessment Model (DREAM-1), developed by Cui et al. (2006a). I compare simulations to a dam removal monitoring project that quantified the physical response of the Souhegan River to the removal of the Merrimack Village Dam (MVD), Merrimack, NH. Pearson et al. (2011) reported results of field monitoring from August 2007-May 2010 and found that the Souhegan River responded to dam removal in two phases: initial rapid incision of impoundment sediment induced by immediate base level drop of 3.9 m (~50% of impounded sediment eroded in ~2 months), followed by an event-driven phase in which impoundment sediment eroded primarily during floods. The reach downstream of the dam showed a similar two-phase response, with rapid deposition in the first three weeks after dam removal followed by bed degradation to the pre-removal elevation profile within a year. I have continued the field methods of Pearson et al. (2011) for the past two survey periods, June 2011 and July 2012. Using five years of comprehensive field data, I conduct a hindcast to compare the sediment erosion and deposition patterns predicted by DREAM-1 to the observed downstream response of the Souhegan River. I model the changes in bed elevation for the downstream and upstream channel reaches at intervals that correspond with the dates of four longitudinal profile surveys and seven annual cross-section surveys. Results of the hindcast show that DREAM-1 predicts channel elevation accurately within one meter and with average discrepancy of ±0.35 m when compared to average channel bed elevations of each cross-section. DREAM-1 successfully simulates two phases of upstream channel response, rapid impoundment erosion followed by a longer period of gradual sedimentation change. However, DREAM-1 erodes to base elevation within 11 weeks after dam removal (erosion of the 88% impoundment sand), leaving little sand for transport during the later survey periods. This overestimation of impoundment erosion is likely the product of limitations of the model, specifically the simplification of channel cross-sections with constant width throughout the simulation. The model assumes uniform lateral sediment transport in the impoundment and does not capture the variation in width due to incision and channel widening. This hinders the ability of the model to simulate some details of the sediment budget developed by Pearson et al. (2011) and extended with recent surveys. / Thesis (MS) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

"Aluminum alloy cleanliness has been in the limelight during the last three decades and still remains as one of the top concerns in the aluminum casting industry. In general, cleaning an aluminum alloy refers to minimizing the following contaminants: 1) dissolved gases, especially hydrogen, 2) alkaline elements, such as sodium, lithium, and calcium, and 3) unwanted solid particles, such as oxides, carbides, and a variety of intermetallic compounds. Extensive research has resulted in significant improvements in our understanding of the various aspects of these contaminants, and in many foundries, melt-cleansing practices have been established and are routinely used. However, with the ever-increasing demands for improved casting properties, requirements for molten metal cleanliness has become extremely stringent. Rotary degassing is one of the most efficient ways of cleansing molten metals, thus removal of unwanted particles and dissolved hydrogen from molten aluminum alloys by rotary degassing has become a widely used foundry practice. Rotary degassing involves purging a gas into the molten alloy through holes in a rotating impeller. Monatomic dissolved hydrogen either diffuses into these gas bubbles or it forms diatomic hydrogen gas at the bubbles’ surface; in any case, it is removed from the melt with the rising bubbles. Simultaneously, solid particles in the melt collide with one another due to turbulence created by the impeller and form aggregates. These aggregates either settle to the furnace floor, or are captured by the rising gas bubbles and are also removed from the melt. The objective of this work is to understand the physical mechanisms underlying the removal of dissolved hydrogen and unwanted solid particles from molten aluminum alloys by the rotating impeller degasser, and to develop a methodology for the effective use of the degassing process by providing mathematical models and computer simulations of the process. The models and simulations can be used to optimize the process, design new equipment and determine the cause of specific operational problems."

Inthisthesiswefocusontheimpactofilluminationchangesinvideoand we discuss how we can minimize the impact of illumination variance in video processing systems. Identifyingandremovingshadowsautomaticallyisaverywellestablished and an important topic in image and video processing. Having shadowless image data would benefit many other systems such as video surveillance, tracking and object recognition algorithms. Anovelapproachtoautomaticallydetectandremoveshadowsispresented in this paper. This new method is based on the observation that, owing to the relative movement of the sun, the length and position of a shadow changes linearly over a relatively long period of time in outdoor environments,wecanconvenientlydistinguishashadowfromotherdark regions in an input video. Then we can identify the Reference Shadow as the one with the highest confidence of the mentioned linear changes. Once one shadow is detected, the rest of the shadow can also be identifiedandremoved. Wehaveprovidedmanyexperimentsandourmethod is fully capable of detecting and removing the shadows of stationary and moving objects. Additionally we have explained how reference shadows can be used to detect textures that reflect the light and shiny materials such as metal, glass and water. ...

The legal requirements for wastewater discharge into environment, especially to zones exposed to eutrophication, lately became stricter. Nowadays wastewater treatment plants have to manage with the new rules and assure better biogenic elements’ removal, in comparison with the past. There are some well-known methods of diminishing concentrations of these compounds, but they are ineffective in case of nitrogen-rich streams, as landfill leachate or reject waters from dewatering of digested sludge. This wastewater disturbs conventional processes of nitrification-denitrification and raise necessity of building bigger tanks. The partial nitritation followed by Anaerobic Ammonium Oxidation (Anammox) process appear to be an excellent alternative for traditional nitrification/denitrification. The process was investigated in three different reactors – Membrane Bioreactor (MBR), Moving Bed Biofilm Reactor (MBBR) and Rotating Biological Contactor (RBC). The process was evaluated in two options: as a two-stage process performed in two separate reactors and as a one-stage process. The two-step process, in spite of very low nitrogen removal rates, assured very high nitrogen removal efficiency, exceeding even 90% in case of the MBBR. However, obtained results revealed that the one-step system is a better option than the two-step system, no matter, what kind of nitrogen-rich stream is taken into consideration. Moreover, the one-step process was much less complicated in operation. Performed research confirmed a hypothesis, that the oxygen concentration in the bulk liquid and the nitrite production rate are the limiting factors for the Anammox reaction in a single reactor. In order to make a quick and simple determination of bacteria activity, the Oxygen Uptake Rate (OUR) tests were shown as an excellent tool for evaluation of the current bacteria activity reliably, and without a need of using expensive reagents. It was also shown, that partial nitritation/Anammox process, could be successfully applied at temperatures much lower than the optimum value. Performed Fluorescent in situ Hybridization (FISH) analyses, proved that the Anammox bacteria were mainly responsible for the nitrogen removal process. / QC 20100707

ABSTRACT EXCHANGES OF STRONTIUM ON CLINOPTILOLITE ZEOLITE G&Uuml / L, &Ouml / zkan MS, Department of Chemical Engineering Supervisor: Prof. Dr. Hayrettin Y&uuml / cel November 2003, 110 Pages Sr-90 and Cs-137, nuclear fission products, are the major sources of medium-level radioactive waste which must be decontaminated. Inorganic ion exchangers are the preferred materials to eliminate radioisotopes from aqueous nuclear waste because of their high selectivity, radiation and thermal stability, low cost and likely compatibility with cement containment. Clinoptilolite and other zeolites are widely used in nuclear industry for the removal of radioisotopes from aqueous nuclear waste. In this study, the performance of local clinoptilolite zeolite from G&ouml / rdes region has been investigated so as to determine the conditions under which it can be used effectively in the column for strontium and cesium removal. It was found that under different loading conditions, breakthrough capacity varied from 0 to 0.4078 meq/g for strontium removal, breakthrough capacity varied from 0.1178 to 0.7800 meq/g for cesium removal. It was also determined that the increase of the flow rate reduced the exchange capacity of the bed. Effect of cationic form of the zeolite (Na-CLI: Sodium form of clinoptilolite and Original-CLI: Original form of clinoptilolite) on the breakthrough capacity was also searched. It was observed that Na-CLI performed much better for the removal of strontium and cesium with respect to its original form. In addition, effect of presence of calcium in the feed solution on the breakthrough capacity was investigated and it was found that presence of calcium in the feed solution makes strontium removal essentially impossible, in the case of cesium, presence of calcium in the feed solution decreases breakthrough capacity significantly.

I denna studie har funktionen hos sju anlagda våtmarker för behandling av avloppsvatten i Sverige jämförts över tid med avseende på avskiljning av kväve, fosfor och BOD. Syftet var att undersöka våtmarkernas långsiktiga funktion, skötselåtgärder och relaterade kostnader. Våtmarkerna (1,6 - 28 ha stora) har varit i drift olika länge, mellan 7 och 17 år, och befintliga övervakningsdata samt intervjuer med ansvariga för respektive våtmark användes som grund för studien. Resultaten visade att våtmarkernas reningsfunktion generellt sett varit god utan någon tendens till en försämrad funktion över tid. Våtmarkerna belastades med 1100 - 9900 kg N/ (ha·år) och avskiljde mellan 420 och 2400 kg N/ (ha·år), beräknat som ett medelvärde per anläggning. Belastningen av fosfor var 17 - 145 kg P/ (ha·år) med en avskiljning på 10 - 110 kg P/ (ha·år). En linjär regressionsanalys visade att en högre fosforbelastning också gav en högre avskiljning. Sambandet var svagare för kväve, vilket indikerar att andra faktorer också var viktiga för kväveavskiljningen. Problem med fosforsläpp i våtmarkerna observerades bara där fosforfällning i reningsverken skett med järnbaserad kemikalie, och verkade vara förknippade med tidvisa anaeroba förhållanden i sedimenten. Utgående halter av BOD7 låg på < 5,0 mg/l för alla våtmarker trots stora skillnader i inkommande halt. Kostnaderna för avskiljningen i våtmarkerna var 30 - 190 kr per kg avskilt kväve och 0 - 4700 kr per kg avskilt fosfor. Storleken på kostnaderna var beroende av investeringskostnaden och den årliga driftkostnaden samt hur kostnaden fördelades mellan kväve och fosfor. / In this study, seven constructed free water surface wetlands for wastewater treatment in Sweden were compared, regarding the removal of nitrogen, phosphorous and BOD. The aim was to investigate the long term function, management needs, related costs and look into uncertainties regarding the risk for phosphorous release. The seven wetlands (1.6 - 28 ha) have been in operation for 7-17 years and existing monitoring data were used along with interviews with the staff responsible for the operation. All wetlands performed satisfactorily and there were no indications of a reduced treatment capacity over time. On average, the wetlands received 1100 to 9900 kg N / (ha·yr) and removed 420 to 2400 kg N / (ha·yr). The phosphorous loads varied between 17 and 145 kg P / (ha·yr) and the removal between 10 and 110 kg P / (ha·yr). A linear regression showed that a higher phosphorous load resulted in a higher removal rate. For the removal of nitrogen the linear relationship was weaker, indicating that other factors also were important. Release of bound phosphorous occurred occasionally in wetlands after WWTP using iron based phosphorous precipitation chemicals, and seemed associated with periods when sediments became anaerobic. Effluent concentrations of BOD were < 5.0 mg/l despite varying inflow concentration, and seemed to reflect a background concentration. The costs for the wetland treatment varied between 30 and 190 SEK per kg N removed and between 0 and 4700 SEK per kg P removed. The size of the costs was dependent on investment and management costs as well as how the cost was distributed between nitrogen and phosphorous.

Heavy metal ions, such as cadmium and lead, should be removed from wastewaters to prevent bioaccumulation. Among many other separation processes, one of the alternatives is ion exchange involving a low cost packing material, clinoptilolite. Clinoptilolite is a natural zeolite and contains exchangeable cations such as Na+, K+, Mg2+, and Ca2+ in its structure. Aim of this study is to determine binary and multicomponent ion exchange behaviors of sodium enriched form of G&ouml / rdes clinoptilolite for lead and cadmium ions. For this purpose, Pb+2 &ndash / Na+, Cd+2 &ndash / Na+ binary and Pb+2 &ndash / Cd+2 &ndash / Na+ ternary systems were investigated in column operations for concentrations between 0.005 to 0.02 N and flow rates between 5 to 20 mL/min at 25 &amp / #730 / C. For determination of optimum particle size, 5/6, 8/10, 14/18, 20/30, 35/60, and 70/140 ASTM E-11 standard mesh ranges were tested and the optimum particle size, under the experimental conditions was found as 35/60. Furthermore, although the clinoptilolite has a theoretical ion exchange capacity of 2.14 meq/g based on its aluminum content, under experimental conditions maximum exchange level was determined as 1.08 meq/g. For binary and ternary experiments, it is observed that the clinoptilolite has affinity for both Pb2+ and Cd2+ ions. However, clinoptilolite has greater affinity to Pb2+ than Cd2+ ion. Therefore, selectivity sequence was determined as Pb2+&gt / Cd2+&gt / Na+. Additionally, for column studies, flow rates less than 10 mL/min and influent concentrations up to 0.01 N, sodium enriched form of G&ouml / rdes clinoptilolite holds great potential to remove Pb2+ and Cd2+ ions from wastewaters.

With increasing water reuse applications and upcoming stringent regulations for treated wastewater effluent discharge, wastewater plants need to consider alternative technologies beyond conventional treatment processes. The new regulations, Numeric Nutrient Criteria (NNC), may regulate discharge nitrogen and phosphorus concentrations to as low as 0.5 mg/L as N and 10 μg/L as P respectively. To meet these target requirements, system retrofitting to incorporate chemical or advanced nutrient removal systems possibly with membrane technology will most likely be required. Although microfiltration/ultrafiltration membranes coupled with biological processes, otherwise known as membrane bioreactors (MBR), remove contaminants and suspended solids, nutrient removal is minimal to none. This emphasizes the importance of the biological process in MBRs. This study evaluated and tested the improvement of biological nutrient removal (BNR) in an MBR system which can meet NNC regulations along with the optimization of membrane operation for the reduction of fouling and energy consumption. A pilot study was conducted at the City of Tampa wastewater treatment plant and was divided into four phases of experimentation using two submerged MBR membranes operated with modified biological configurations. Laboratory analyses and data collection were conducted during the experiments and the performance evaluated for each configuration. System configurations were also optimized throughout each phase of testing for nutrient removal. Important factors used in the development of an appropriate configuration included isolation of the membrane tank from the biological reactors in the design, control of the dissolved oxygen (DO) concentrations or specifically the oxidation reduction potential (ORP) during operation and appropriate internal recirculation rates between the reactors. The results of this study provided information relevant for the assessment of both the BNR process and membrane performance. Membrane performance data indicated the importance and effect of air scouring (despite energy consumption) on membrane fouling for long-term stable flux operation as well as the cleaning frequency whether chemical enhanced backwash (CEB) or clean-in-place (CIP). This assessment also discussed how BNR systems can be enhanced through the incorporation of important design factors to eliminate the inhibiting factors of nitrogen and phosphorus removal such as dissolved oxygen. One of the biological processes tested in this study achieved effluent nitrogen and phosphorus concentrations below 5 mg/L and 1 mg/L respectively. Although the process tested did not meet NNC criteria, it can be applied with chemical precipitation. This, in turn, can reduce the operating and maintenance (O&M) costs associated with the chemical precipitation of phosphorus.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy