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München, Univ., Diss., 2002. / Computerdatei im Fernzugriff.

München, Univ., Diss., 2002. / Computerdatei im Fernzugriff.

Harmful algal blooms in surface water supply systems pose a threat to public health and are increasing in both frequency and geographical distribution. Cyanobacteria can contribute to taste and odor issues and potentially release harmful cyanotoxins into the water. Several treatment methods are currently employed to control these blooms, including physical separation and chemical pre-oxidation. However, existing oxidation options can be costly; increase the release of intracellular material causing the formation of disinfection byproducts; or disrupt coagulation and filtration processes. This study investigated ferrate (Fe(VI)) as an alternative to other oxidants by measuring its effect on algae cells. Fe(VI) has several advantages as an oxidant, including a high oxidation potential, a low potential for harmful disinfection byproduct production, and formation of Fe(III) - which can potentially be beneficial for downstream treatment processes. Bench scale studies were conducted with laboratory prepared waters containing the common cyanobacteria Microcystis aeruginosa to examine the interactions between Fe(VI) and algae. The effects of ferrate oxidation on algae were characterized by particle counts, UV254 absorbance, total organic carbon (TOC) and dissolved organic carbon (DOC), and total nitrogen. Ferrate decomposition was also monitored. Results showed that Fe(VI) lysed algal cells under some conditions, but further oxidation of released organic matter is possible at some doses. Additionally, some coagulation benefits were observed through an overall decrease in total particle counts and an increase in particle sizes. In general, the results indicate that Fe(VI) could be a possible alternative to other oxidants for water utilities during harmful algal blooms; however, the final fate of resulting organic matter and the potential for disinfection byproduct formation should be further studied.

This study was conducted to evaluate the effectiveness of the liquid form of ferrate for dewatering of biosolids from wastewater treatment facilities. Two different ferrate products prepared using calcium hypochlorite and sodium hypochlorite were used. Samples of anaerobic digested sludge and waste activated sludge with solids content of 2.1% and 0.95 %, respectively were conditioned with both products to evaluate and compare their effectiveness. Centrifugation and filtration of the sludge after conditioning were used. For centrifugation the volume reduction and the turbidity of the supernatant after centrifugation were evaluated. For filtration, the Capillary Suction Time test was used. The optimum doses and conditions for dewatering of the sludge using ferrate were determined for each type of sludge. The centrifugation and filtration results were compared with those obtained for polymer doses currently used at the wastewater treatment plants where the samples were collected and with ferric coagulants as well. The results of this research indicated that optimum pH was 7.0. The time required to achieve mechanical equilibrium defined as the time at which the volume occupied by the solids was no more than one percent of the preceding reading was 1800 seconds for both types of sludge. The optimum rotational speeds were 800 and 2400 for waste activated sludge and anaerobic digested sludge, respectively. The optimum ferrate dose for anaerobic digested sludge for centrifugation and filtration was 5000 mg/l. For waste activated sludge a dose of 10 mg/l was found to be effective for filtration and centrifugation. The results indicated that the ferrate product prepared using calcium hypochlorite provides better results for the waste activated sludge than the ferrate prepared using sodium hypochlorite, while for anaerobic digested sludge no significant difference was observed. Finally, the results show that ferrate is a cost-effective alternative for the conditioning and disinfection of waste activated sludge, but not for the conditioning of anaerobic digested sludge.

Ferrate (molecular formula, FeVIO42-) has been studied increasingly since the 1970s as a disinfectant and coagulant for domestic wastewater and also as an oxidant for industrial wastewaters (Murmann and Roginson, 1974, Gilbert et al., 1978, Kazama, 1994, Jiang et al., 2002, and Sharmaet al., 2005). This research was performed to explore whether ferrate could possibly be used as chemical treatment for industrial wastewaters from plastic, chemical, dye, soap, and wood stain producing plants that contain 2, 4-Dinitrophenol (DNP). DNP is listed on the United States Environmental Protection Agency (EPA) Drinking Water Contaminant Candidate List (CCL). This list includes compounds which are not currently regulated at the national level, but there is a growing concern for the harm they may cause to the environment. Therefore, the EPA prioritizes these compounds and conducts extensive research to determine if these compounds should be regulated (USEPA, 2005). The effects of Ferrate on DNP were evaluated during these experiments. The effect of various dosages of Ferrate and different pH values was monitored over 17 minutes using UV 254 to determine the extent of oxidation of 300 mg L-1 DNP. Removal of DNP at all pHs and dosages was noted, however, a pH of 4 and a molar ratio of 14: 1 (Ferrate to DNP) removed the highest percentage of DNP at 87.3. The by-products of the 3.5 and 14: 1 molar ratio of Ferrate to DNP reactions at a pH of 4 and their toxicity were determined by measuring biochemical oxygen demand 5 day (BOD5), dissolved organic carbon (DOC), chlorine residual and chemical oxygen demand (COD), and gas chromatography/mass spectrometry (GC/MS) analysis. The BOD5 indicated toxicity, either from the residual chlorine or the organisms used for seeding not being acclimated to DNP and by-products. DOC of the 3.5 : 1 molar ratio was higher than calculated values indicating more ring breakage than was originally measured by UV 254. DOC of the 14: 1 molar ratio experiment was lower than calculated values, which indicated human error in measuring the DNP concentration. The chlorine residual was high for both experiments, 112 and 594 mg L-1, for the 3.5 and 14: 1 molar ratios, respectively. COD was unable to be measured due to chloride interference. The GC/MS data showed several chlorine-substituted benzene rings as well as carbon tetrachloride for the 3.5:1 molar ratio DNP experiments. The 14:1 GC/MS data indicated much more ring breakage with carbon tetrachloride, a substituted butane chain, many unknown straight chain chlorinated compounds and dichloro-pentane isomers as by-products.

Universiẗat, Diss., 2002--München.

The goal of this study was to evaluate the feasibility of using advanced coagulation with Fe(VI) in coagulation-flocculation-sedimentation/ flotation systems for the pretreatment of SWRO desalination plants during algal bloom events. Algal organic matter (AOM) material extracted from marine diatom species (Chaetoceros affinis) was added to Red Sea water to mimic algal bloom conditions. Low dosage of Fe(VI) (<1 mg Fe/L) was very effective at improving feed water quality containing AOM (algal bloom conditions). Based on results from both a bench-scale DAF unit and Jar testing unit, 0.75 mg Fe/L of Fe (VI) proved to be effective at improving the raw water quality which is comparable to the performance of 1 and 3 mg Fe/L of Fe (III). The removal efficiency for both testing units with the use of Fe(VI) was up to 100% for algae , 99.99% for ATP, 99% for biopolymers and 70 % for DOC. The improvement in Fe(VI) performance is related to the simultaneous action of Fe(VI) as oxidant, disinfectant and coagulant. The performance of Fe(VI) coagulant was also evaluated with the use of coagulant aids (clays). The overall turbidity, DOC, biopolymers and algal cells removal was improved via using Fe(VI) and clays at very low dose. Generally, it was found that for the same pretreatment performance achieved, a much lower Fe(VI) dose was required compared to Fe (III), which make it important to study of cost effectiveness for using Fe(VI) instead of Fe(III) and estimate cost savings during algal bloom conditions. A detailed cost comparative study was conducted for Fe(III) vs. Fe(VI) coagulation process based on the removal efficiency. The use of Fe(VI) reduced the total pretreatment cost by 77% and sludge disposal cost by > 88% compared to the use of Fe(III) in the pretreatment process. The use of Fe(VI) reduces the operational and maintenance cost in SWRO desalination plant by 7% and the production cost by 4%. This study proved that the use of Fe(VI) during high turgidity and algal bloom conditions helped providing high raw water quality to the RO process with lower chemicals and operations cost as well as low chlorine and iron residuals.

Le ferrate (VI) de potassium est un produit prometteur dans la filière du traitement des eaux de par ses propriétés oxydantes, coagulantes et désinfectantes. S’il n’est pas largement employé aujourd’hui, c’est à cause de son coût de production. Un objectif majeur de ce travail est de développer la synthèse du ferrate (VI) au sein du sel double K2(Fe0,5,S0,5)O4 solide et stable. L’étude de la synthèse à l’échelle du laboratoire a permis de comprendre les mécanismes physico-chimiques régissant la synthèse et d’établir un cahier des charges pour la conception d’un pilote semi-industriel. En l’état actuel des recherches, un produit contenant 28-34% de K2(Fe0,5,S0,5)O4 est obtenu. L’étude de l’action du ferrate (VI) sur des molécules organiques (pharmaceutiques, toxines, bactéries…) et inorganiques (cyanures, métaux…) a été réalisée. Un mécanisme d’oxydation par transfert électronique à 1 électron a été observé lors du traitement du phénol. Le potentiel du produit à être utilisé pour une dépollution de l’eau est confirmé sur des polluants modèles et sur des effluents réels et lui assure un large domaine d’application. / Potassium ferrate (VI) is a new challenging product in the field of water treatment. The world interest in this high-valent iron is explained by its properties of chemical oxidant, coagulant and disinfectant. However, high cost of its production restricts its big scale applications. Thus, the main objective of this study is focused on ferrate synthesis in a solid form more stable K2(Fe0,5,S0,5)O4. At first, synthesis has been developed at lab scale to improve understanding of its mechanisms and define the conception of a small industrial pilot. At the moment, a product with 28-34% of K2(Fe0,5,S0,5)O4 is obtained. The removal of organics (pharmaceuticals, toxins, bacteria…) and inorganics (cyanides, metals…) in water by ferrate (VI) has been explored. An oxidation mechanism which consists in a single electron transfer has been highlighted for phenol treatment. Finally, the results confirm the real ability of the product synthesized to treat both contaminants in water and industrial effluents.

In recent years exposure to endocrine-disrupting chemicals (EDCs) in humans and wildlife has become an increasing concern. These compounds have been found ubiquitously in the environment and are suspected to induce adverse effects on the health of aquatic organisms. The results of health effects due to EDCs are clearly presented in many aquatic organisms, such as the feminization of male fish and a near extinction of some species. No clear effects on human health have been documented at this time. The major sources of these contaminants in the environment are discharges from wastewater treatment plants (WWTP) and diffuse pollution. Conventional wastewater treatment processes are not designed to remove such emerging pollutants and removal efficiency depends on many factors, including treatment technology and pollutant species. Passage through WWTPs and changes due to treatment technologies lead to detection of minute concentrations of EDCs in water downstream from discharge points. In New Orleans, Louisiana, discharge from its East Bank WWTP is being considered for potential reuse for wetland restoration. Therefore, effluents must be treated adequately to prevent adverse effects on the natural biota. Since effluents from wastewater treatment plants using conventional technologies may prove potentially unsafe for the environment due to the presence of EDCs, improved and/or new treatment processes for removal of these contaminants are needed. Ferrate (Fe+6) is known as an alternative oxidant for the treatment of wastewater that can be used as an oxidizing, disinfectant, and/or coagulating agent. Because of its redox potential, ferrate has been used as a disinfection agent and has been reported as a tool for enhanced treatment to remove many micropollutants without producing undesirable disinfection byproducts in contrast to other disinfection processes. Recent research has noted the ability of ferrate to deactivate a wide range of EDCs present in wastewater effluents. The negative effect of effluent's soluble organic matter on ferrate has been reported and higher doses of ferrate may be needed to obtain desired effluent quality. This study found that aerobic biological treatment processes reduce more than half of EDCs in wastewater and that free chlorine disinfection increases estrogenic activity in discharged effluent. Higher organic content in wastewater results in increased ferrate demand. The optimum ferrate dosage to deactivate EDCs in lab scale is 6 ppm, and a dosage of 8 ppm is possibly the operational optimum dose. pH neutralization by concentrated sulfuric acid was not found to affect EDCs deactivation efficiency by ferrate when added at the end of designed contact time. Ferrate was observed to have a high oxidation rate in the first10 minutes after application into wastewater and then degraded to other iron states, such as iron III. Higher oxidation rates can be obtained when more organics are present in wastewater as TOC. Higher dosages required longer oxidation reaction times. Ferrate was observed to generate fewer disinfection byproducts as compared to chlorine. Haloacetic acids in ferrate-treated effluent are generated from organics in wastewater and reactions with residual hypochlorite from the incomplete ferrate synthesis process. The reduction of trihalomethanes may be related to EDCs deactivation by ferrate. Because this study was performed on a lab scale, assessment of onsite production and application of ferrate is required to determine the feasibility of the ferrate treatment process at a full-scale treatment plant and to optimize required dosage. / acase@tulane.edu