Fenton-dependent recovery of carbon initially saturated with one of several chlorinated aliphatic contaminants was studied in batch and continuous-flow reactors. A specialty carbon, URV-MOD 1 (Calgon) was employed to minimize non-productive H2O2 demand - that which does not yield hydroxyl or superoxide radicals.Enhancement of PCE degradation kinetics by ferric iron addition is limited by iron solubility, even at relatively low pH. Quinone addition increased the pseudo-first-order rate constant for PCE loss temporarily. Only copper addition sustainably enhanced the specific rate of PCE loss. For copper-to-iron molar ratios of 0.25 to 5, the pseudo-first-order rate constant for PCE transformation was increased by a factor of 3.5. It is apparent that the effect of copper addition on Fenton-dependent reaction rates is complex, and involves a shift in chemical mechanism, as indicated by the differing slopes in the Arrhenius plot (with and without copper).A mathematical model was developed to evaluate the effect of operational parameters ([Fe(III)]T:[H2O2]o ratio and pH) on degradation kinetics and optimize the PCE degradation process in homogeneous reaction mixtures. The model simulated experimental degradation of the organic target in a homogeneous Fenton-reaction system. The model requires further refinement to simulate Fenton's systems in which ions in solution (such as sulfate and chloride) play significant roles.In continuous-flow reactors, Fenton's reagents were cycled through spent GAC in columns to degrade one of seven chlorinated compounds tested. The contaminant with the weakest adsorption characteristics, methylene chloride, was 99% lost from the carbon surface during a 14-hour regeneration period. At the field site, the GAC was saturated with gases containing TCE and PCE from a soil vapor extraction (SVE) system. In the field, up to 95% of the sorbed TCE was removed from GAC during regeneration periods of 50-60 hours. Recovery of PCE-loaded GAC was significantly slower. Column experiments show that there is minimal loss of carbon adsorption capacity during Fenton treatment and that the rate of GAC regeneration is compound specific. Scoping-level cost estimates indicated that field use of Fenton regeneration is not cost effective without optimization and/or iron surface amendments, except in the case of the most soluble VOCs.

The treatment of potable water in Vars, ON is accomplished by filtering the colored, iron-laden groundwater through granular activated carbon (GAC) filters. When first installed, these filters unexpectedly experienced chromatographic displacements of iron into the produced water which resulted in orange-brown water at consumers’ taps. The treatment plant was later modified by adding potassium permanganate oxidation and a greensand filter prior to the GAC adsorption columns. Consequently, iron was almost completely removed and no longer caused operational problems. The main objective of this dissertation is to study the interactions between natural organic matter (NOM) and iron that caused the observed chromatographic effect. This study was divided into three main stages: a) characterization study on Vars groundwater and its treatment system; b) study of the competitive adsorption of iron with NOM in Vars groundwater; and c) evaluation of the rapid small-scale column test (RSSCT) for predicting the full-scale GAC column breakthroughs. The characterization of Vars groundwater showed that ferrous iron was found to be the dominant iron species, representing 90% of the total iron, and that 15 - 35% of the iron was complexed with NOM. It was hypothesized that the chromatographic displacement of iron from the GAC columns was caused by NOM-iron complexes; however, field mini-column experiments showed this was not the case. Thus, competitive adsorption between iron and NOM was seen as the more likely cause of the chromatographic effect. The adsorption capacity of ferrous iron in Vars raw water was less than that in organic-free water by a factor of 7 due to the competition with NOM over the GAC adsorbing sites. However, the NOM adsorption capacity was not reduced due to the presence of ferrous iron. It was hypothesized that ideal adsorption solution theory (IAST) models, which have been successful in describing competitive adsorption between target organic compounds and NOM, could model the competition between an inorganic compound such as ferrous iron and NOM. The hypothesis was proved to be correct, and the adsorption isotherm of iron in competition with NOM in Vars groundwater was simulated very well by several versions of the IAST model. However, none of the models were capable of simulating the competitive adsorption of NOM and ferrous iron simultaneously. Since the presence of iron did not significantly reduce the adsorption capacity of NOM, a simplified approach of using the single-solute NOM isotherm to represent the competitive NOM isotherm was recommended. The performance of the rapid small-scale column test (RSSCT) was evaluated in order to simulate the iron chromatographic effect observed at Vars’ full-scale GAC column. The RSSCT was not capable of predicting the iron phenomenon and the test proved to be problematic due to the oxidation and precipitation of iron within the small voids between the small-scale column’s GAC particles. The RSSCT, using constant and linear diffusivities, were applied to simulate the NOM adsorption after greensand treatment. Integrating both diffusivities, the tests predicted the onset and slope of the NOM breakthrough up to 10-L water treated/g GAC, which is equivalent to 250 days of operation time for the full-scale column. However, the NOM breakthroughs deviated beyond that point and the RSSCT using constant diffusivity underestimated the column performance greatly. On the other hand, the linear diffusivity RSSCT underestimated the performance to a lesser degree and its NOM breakthrough was quite parallel to the full-scale performance with lower NOM removals of 15%. The higher long-term NOM removal in the full-scale system may be explained by biodegradation, a phenomenon that was not considered by the short duration of RSSCT.

The treatment of potable water in Vars, ON is accomplished by filtering the colored, iron-laden groundwater through granular activated carbon (GAC) filters. When first installed, these filters unexpectedly experienced chromatographic displacements of iron into the produced water which resulted in orange-brown water at consumers’ taps. The treatment plant was later modified by adding potassium permanganate oxidation and a greensand filter prior to the GAC adsorption columns. Consequently, iron was almost completely removed and no longer caused operational problems. The main objective of this dissertation is to study the interactions between natural organic matter (NOM) and iron that caused the observed chromatographic effect. This study was divided into three main stages: a) characterization study on Vars groundwater and its treatment system; b) study of the competitive adsorption of iron with NOM in Vars groundwater; and c) evaluation of the rapid small-scale column test (RSSCT) for predicting the full-scale GAC column breakthroughs. The characterization of Vars groundwater showed that ferrous iron was found to be the dominant iron species, representing 90% of the total iron, and that 15 - 35% of the iron was complexed with NOM. It was hypothesized that the chromatographic displacement of iron from the GAC columns was caused by NOM-iron complexes; however, field mini-column experiments showed this was not the case. Thus, competitive adsorption between iron and NOM was seen as the more likely cause of the chromatographic effect. The adsorption capacity of ferrous iron in Vars raw water was less than that in organic-free water by a factor of 7 due to the competition with NOM over the GAC adsorbing sites. However, the NOM adsorption capacity was not reduced due to the presence of ferrous iron. It was hypothesized that ideal adsorption solution theory (IAST) models, which have been successful in describing competitive adsorption between target organic compounds and NOM, could model the competition between an inorganic compound such as ferrous iron and NOM. The hypothesis was proved to be correct, and the adsorption isotherm of iron in competition with NOM in Vars groundwater was simulated very well by several versions of the IAST model. However, none of the models were capable of simulating the competitive adsorption of NOM and ferrous iron simultaneously. Since the presence of iron did not significantly reduce the adsorption capacity of NOM, a simplified approach of using the single-solute NOM isotherm to represent the competitive NOM isotherm was recommended. The performance of the rapid small-scale column test (RSSCT) was evaluated in order to simulate the iron chromatographic effect observed at Vars’ full-scale GAC column. The RSSCT was not capable of predicting the iron phenomenon and the test proved to be problematic due to the oxidation and precipitation of iron within the small voids between the small-scale column’s GAC particles. The RSSCT, using constant and linear diffusivities, were applied to simulate the NOM adsorption after greensand treatment. Integrating both diffusivities, the tests predicted the onset and slope of the NOM breakthrough up to 10-L water treated/g GAC, which is equivalent to 250 days of operation time for the full-scale column. However, the NOM breakthroughs deviated beyond that point and the RSSCT using constant diffusivity underestimated the column performance greatly. On the other hand, the linear diffusivity RSSCT underestimated the performance to a lesser degree and its NOM breakthrough was quite parallel to the full-scale performance with lower NOM removals of 15%. The higher long-term NOM removal in the full-scale system may be explained by biodegradation, a phenomenon that was not considered by the short duration of RSSCT.

Zugl.: Berlin, Humboldt-Univ., Diss., 2008

Masters Research - Master of Philosophy (MPhil) / Gac fruit, Momordica cochinchinensis Spreng contains extraordinarily high levels of carotenoids, especially β-carotene and lycopene, and a comparatively high content of alpha-tocopherol (vitamin E) and of polyunsaturated fatty acids. The aim of this study was therefore to develop an understanding of suitable conditions for the processing of Gac fruit and the preparation of Gac fruit powder. The objectives of this study were to investigate the effect of 1) pre-treatments; blanching, ascorbic acid and bisulfite, and 2) drying techniques; air, vacuum, freeze and spray drying, on the physicochemical and antioxidant properties of powders produced from Gac arils. In addition, Gac arils (mixed with added maltodextrin) and untreated Gac skin and yellow pulp were air-dried and their properties were evaluated. The shelf life of a number of the Gac powder products was periodically evaluated during an extended storage period. The moisture sorption isotherms of various Gac powders were also constructed. Furthermore, the stability of three different types of Gac fruit powders was also tested when used in food and beverage products. Results showed that freeze drying of fresh Gac aril without any pre-treatment produced powders of high quality as determined by colour (hue angle of 33.93, total carotenoid content (TCC) of 7.24 mg/g and total antioxidant activity (TAA) of 0.39 mmole TE/g). However, pre-treatment of fresh Gac fruit aril with 1% (w/v) ascorbic acid or bisulfite solution before vacuum drying at 40 oC for 45 hours was just as effective as freeze drying in preserving colour (hue angle of 34.18 and 36.25, respectively), TCC (7.28 and 6.99 mg/g, respectively) and TAA of 0.36-0.40 mmole TE/g. Pre-treatment with 1% (w/v) ascorbic acid or bisulfite solution before air drying at 40 oC for 48 hours was also effective (TCC of 6.36 and 6.11 mg/g, respectively and TAA of 0.33 mmole TE/g) but not to the extent of vacuum or freeze drying. In respect of the spray drying process, taking into account the dilution effect of the added maltodextrin, the addition of 10% maltodextrin to the feed mixture and drying at 120 oC effectively preserved the physicochemical and antioxidant properties of the powder (hue angle of 66.85, TCC of 2.77 mg/g and TAA of 0.14 mmole TE/g). In addition, in a comparison of fresh and frozen arils, both were found to be equally useful for production of Gac powder in terms of preservation of colour (hue angle of 33.93 and 31.28, respectively), TCC (7.24 and 6.27 mg/g, respectively) and TAA (0.39 and 0.33 mmole TE/g, respectively). However, the dried aril was found to be very difficult to grind due to its stickiness. The addition of maltodextrin (0.5 or 1 g maltodextrin/g of total fruit solids) prior to drying solved this problem and also maintained the quality of the powder (hue angle of 28.04-30.55; TCC of 5.65-6.29 mg/g and TAA of 0.29-0.31 mmole TE/g, respectively). The storage study indicated that the degradation of TCC and TAA of freeze-dried and spray-dried powders for up to 8 and 3 months, respectively, was lowest when samples were packed into laminated bags and stored at temperature of 10 oC (TCC loss of 11% and 5% and TAA loss of 44% and 15%, respectively). The highest losses for freeze-dried and spray-dried powders (TCC of 70% and 42%; and TAA of 88% and 42%, respectively) occurred when stored at conditions of 37 oC. Isotherm curves of all the Gac powders have sigmoid shapes. By comparing different drying methods for aril, the lowest hygroscopicity was observed in SD powder, followed by VD, AD and FD powders. Results also showed that the air-dried skin and yellow pulp powders contained low levels of TCC and TAA compared to the aril powders, but these are still high levels of TCC (0.90 and 0.42 mg/g, respectively) as compared to cherry tomatoes (0.36) and pumpkin (0.14). The skin (18%) and yellow pulp (49%) account for 67% of the total weight of the Gac fruit and as such comprise significantly high components. Therefore, utilisation of these components can prevent environmental pollution due to waste issues, and also enhances the overall value of Gac fruit. Freeze-dried, vacuum-dried and spray-dried Gac fruit aril powders were found to be easily incorporated into cooked glutinous rice, pasteurised Gac juice and pasteurised Gac milk mixtures. The colour, TCC and TAA of the juice and the milk mixtures were maintained after storage for 30 days under refrigeration temperature of 40 oC. Overall the study established that, the quality of Gac aril powders, in terms of colour, TCC and TAA, is most effectively preserved by applying pre-treatments prior to vacuum drying at 40 oC. These powders should be packed in laminated bags and stored at 10 oC for any lengthy storage period. It was also found that the Gac powders can be satisfactorily incorporated into “Xoi Gac”, juice and milk products. Finally, the overall value of Gac fruit could be enhanced through utilisation of all the anatomical components.

abstract: Granular activated carbon (GAC) filters are final polishing step in the drinking water treatment systems for removal of dissolved organic carbon fractions. Generally filters are colonized by bacterial communities and their activity reduces biodegradable solutes allowing partial regeneration of GAC's adsorptive capacity. When the bacteria pass into the filtrate due to increased growth, microbiological quality of drinking water is compromised and regrowth in the distribution system occurs. Bacteria attached to carbon particles as biofilms or in conjugation with other bacteria were observed to be highly resistant to post filtration microbial mitigation techniques. Some of these bacteria were identified as pathogenic. This study focuses on one such pathogen Legionella pneumophila which is resistant to environmental stressors and treatment conditions. It is also responsible for Legionnaires' disease outbreak through drinking water thus attracting attention of regulatory agencies. The work assessed the attachment and colonization of Legionella and heterotrophic bacteria in lab scale GAC media column filters. Quantification of Legionella and HPC in the influent, effluent, column's biofilms and on the GAC particles was performed over time using fluorescent microscopy and culture based techniques. The results indicated gradual increase in the colonization of the GAC particles with HPC bacteria. Initially high number of Legionella cells were detected in the column effluent and were not detected on GAC suggesting low attachment of the cells to the particles potentially due to lack of any previous biofilms. With the initial colonization of the filter media by other bacteria the number of Legionella cells on the GAC particles and biofilms also increased. Presence of Legionella was confirmed in all the samples collected from the columns spiked with Legionella. Significant increase in the Legionella was observed in column's inner surface biofilm (0.25 logs up to 0.52 logs) and on GAC particles (0.42 logs up to 0.63 logs) after 2 months. Legionella and HPC attached to column's biofilm were higher than that on GAC particles indicating the strong association with biofilms. The bacterial concentration slowly increased in the effluent. This may be due to column's wall effect decreasing filter efficiency, possible exhaustion of GAC capacity over time and potential bacterial growth. / Dissertation/Thesis / Masters Thesis Civil and Environmental Engineering 2014

The treatment of potable water in Vars, ON is accomplished by filtering the colored, iron-laden groundwater through granular activated carbon (GAC) filters. When first installed, these filters unexpectedly experienced chromatographic displacements of iron into the produced water which resulted in orange-brown water at consumers’ taps. The treatment plant was later modified by adding potassium permanganate oxidation and a greensand filter prior to the GAC adsorption columns. Consequently, iron was almost completely removed and no longer caused operational problems. The main objective of this dissertation is to study the interactions between natural organic matter (NOM) and iron that caused the observed chromatographic effect. This study was divided into three main stages: a) characterization study on Vars groundwater and its treatment system; b) study of the competitive adsorption of iron with NOM in Vars groundwater; and c) evaluation of the rapid small-scale column test (RSSCT) for predicting the full-scale GAC column breakthroughs. The characterization of Vars groundwater showed that ferrous iron was found to be the dominant iron species, representing 90% of the total iron, and that 15 - 35% of the iron was complexed with NOM. It was hypothesized that the chromatographic displacement of iron from the GAC columns was caused by NOM-iron complexes; however, field mini-column experiments showed this was not the case. Thus, competitive adsorption between iron and NOM was seen as the more likely cause of the chromatographic effect. The adsorption capacity of ferrous iron in Vars raw water was less than that in organic-free water by a factor of 7 due to the competition with NOM over the GAC adsorbing sites. However, the NOM adsorption capacity was not reduced due to the presence of ferrous iron. It was hypothesized that ideal adsorption solution theory (IAST) models, which have been successful in describing competitive adsorption between target organic compounds and NOM, could model the competition between an inorganic compound such as ferrous iron and NOM. The hypothesis was proved to be correct, and the adsorption isotherm of iron in competition with NOM in Vars groundwater was simulated very well by several versions of the IAST model. However, none of the models were capable of simulating the competitive adsorption of NOM and ferrous iron simultaneously. Since the presence of iron did not significantly reduce the adsorption capacity of NOM, a simplified approach of using the single-solute NOM isotherm to represent the competitive NOM isotherm was recommended. The performance of the rapid small-scale column test (RSSCT) was evaluated in order to simulate the iron chromatographic effect observed at Vars’ full-scale GAC column. The RSSCT was not capable of predicting the iron phenomenon and the test proved to be problematic due to the oxidation and precipitation of iron within the small voids between the small-scale column’s GAC particles. The RSSCT, using constant and linear diffusivities, were applied to simulate the NOM adsorption after greensand treatment. Integrating both diffusivities, the tests predicted the onset and slope of the NOM breakthrough up to 10-L water treated/g GAC, which is equivalent to 250 days of operation time for the full-scale column. However, the NOM breakthroughs deviated beyond that point and the RSSCT using constant diffusivity underestimated the column performance greatly. On the other hand, the linear diffusivity RSSCT underestimated the performance to a lesser degree and its NOM breakthrough was quite parallel to the full-scale performance with lower NOM removals of 15%. The higher long-term NOM removal in the full-scale system may be explained by biodegradation, a phenomenon that was not considered by the short duration of RSSCT.

The use of seawater in cooling towers for industrial applications has much merit in the Gulf Cooperation Council countries due to the scarcity and availability of fresh water. Seawater make-up in cooling towers is deemed the most feasible because of its unlimited supply in coastal areas. Such latent-heat removal with seawater in cooling towers is several folds more efficient than sensible heat extraction via heat exchangers. Operational challenges such as scaling, corrosion, and biofouling are a major challenge in conventional cooling towers, where the latter is also a major issue in seawater cooling towers. Biofouling can significantly hamper the efficiency of cooling towers. The most popular methods used in cooling treatment to control biofouling are disinfection by chlorination. However, the disadvantages of chlorination are formation of harmful disinfection byproducts in the presence of high organic loading and safety concerns in the storage of chlorine gas. In this study, the research focuses on biofouling control in seawater cooling towers by investigating two different approaches. The first strategy addresses the use of alternative oxidants (i.e. ozone micro-bubbles and chlorine dioxide) in treatment of cooling towers. The second strategy investigates removing nutrients in seawater using granular activated carbon filter column and ultrafiltration to prevent the growth of microorganisms. Laboratory bench-scale tests in terms of temperature, cycle of concentration, dosage, etc. indicated that, at lower oxidant dosages (total residual oxidant (TRO) equivalent = 0.1 mg/l Cl2), chlorine dioxide had a better disinfection effect than chlorine and ozone. The performance of oxidizing biocides at pilot scale, operating at assorted conditions, showed that for the disinfectants tested, ozone could remove 95 % bioactivity of total number of bacteria and algae followed by chlorine dioxide at 85%, while conventional chlorine dosing only gave 60% reduction in bioactivities. Test results of GAC bio-filter showed that around 70 % removal of total organic carbon in the seawater feed was achieved and was effective in keeping the microbial growth to a minimum. The measured results from this study enable designers of seawater cooling towers to manage the biofouling problems when such cooling towers are extrapolated to a pilot scale.

No description available.

The removal of 34 per- and polyfluoroalkyl substances (PFAS) were compared in a 1 stagegranular activated carbon (GAC) filtration to a 2 stage GAC filtration in a pilot study at adrinking water treatment plant (DWTP). The PFASs that were present in the water wereperfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluoropentanoic acid(PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorobutanesulfonic acid (PFBS), perfluoropentane sulfonic acid (PFPeS) and perfluorohexane sulfonic acid(PFHxS). A cost comparison for the operation of a one stage GAC to a two stage GAC wascompared for PFAS4 (sum of PFOA, PFNA, PFHxS and PFOS) at treatment goals ranging from2 - 10 ng/L. The pilot was operated at three different flows and the three different bed volumes(BV)s resulting in three different empty bed contact times (EBCTs) at three different times.Therefore, the Lin & Huang adsorption model (1999) was used to model the concentrations ateach EBCT. It was found that the model worked good for PFBS, PFPeS, PFHxS, PFOS andPFOA but not for PFPeA, PFHxA and PFHpA (except for PFPeA and PFHxA during EBCT 5min) and did not work for desorbing PFASs. The removal comparison of PFASs was made,partly by comparing removal efficiencies between the first stage and the second stage GAC filterand by comparing the removal per weight of GAC per BV 1 stage and 2 stages. It was found thatthe removal efficiency decreases with decreasing chain length and increasing treated BVs forboth the first stage and the second stage. The short chain PFCAs were also desorbing after anumber of BVs. The removal per weight of GAC showed that the removal does not increasewhen comparing a one stage GAC to a two stage GAC for any the PFAS. The cost comparisonwas made using the adsorption model. It showed that it was cheaper to operate a 2 stage GAC forthe EBCT of 5 minutes and 8 minutes for the whole range of treatment goals. However, for theEBCT of 15 minutes the costs for the second stage was decreasing with decreasing treatmentgoal which is unrealistic result. This was caused by too few data points available for the model topredict reliable results.