Treatment of biorefractory wastewater through membrane-assisted oxidation processes

La escasez de agua se presenta como uno de los mayores retos para asegurar el desarrollo sostenible. Entre otras actuaciones, se deben investigar e implementar sistemas eficientes de tratamiento de aguas biorecalcitrantes, que necesitan ser condicionadas antes de su depuración biológica. Uno de los posibles pre-tratamientos es el proceso Fenton de oxidación avanzada, que presenta dos principales inconvenientes: la utilización de sales de hierro como catalizador homogéneo, que abandonan continuamente la etapa de oxidación, y el elevado consumo de oxidante, en parte desaprovechado. La presente tesis se centra en el estudio de la mejora del proceso Fenton de aguas fenólicas mediante su acoplamiento con tecnologías de membrana como la nanofiltración, la emulsificación con membranas o los reactores de membrana. El acoplamiento de dichas tecnologías con el proceso Fenton permite el confinamiento del catalizador y el aumento de la eficiencia de oxidación, mejorando así el tratamiento en términos ambientales y económicos.Water scarcity is one of the major challenges for assuring a sustainable development. Among other measures, research into efficient wastewater treatment systems to deal with biorefractory wastewaters, which need to be amended before their biological degradation, is required. The Fenton process is an advanced oxidation process that can be used as potential pre-treatment for this purpose. However, the pre-treatment presents two main limitations: the use of iron salts as homogeneous catalyst, which are continuously thrown away in the reactor effluent, and the high consumption of oxidant, which is partially wasted. The present thesis aims at studying the improvement of the Fenton process applied on phenolic wastewater through its coupling with membrane technologies such as nanofiltration, membrane emulsification or membrane reactors. The coupling allows confining the catalyst and increasing the oxidation efficiency, thus enhancing the treatment efficiency in environmental and economic terms

Composition and reversibility of fouling on low-pressure membranes in the filtration of coagulated water: insights into organic fractions behaviour

The primary problem for the application of microfiltration (MF) and ultrafiltration (UF) membrane technology is membrane fouling. Such is the case that understanding membrane fouling has become one of the major factors driving MF and UF membrane technology for- ward. Nevertheless, identifying the constituents that most contribute to membrane fouling 20 and quantifying how they are detached when backwashing (BW) and cleaning-in-place (CIP) are applied still remains a challenging task. The aim of the present study was to quan- tify membrane fouling development during filtration and membrane fouling detachment during BW and CIP in terms of membrane permeability changes and masses of inorganic and organic constituents accumulated on the membrane. The study was conducted using 25 bench-scale MF and UF modules fed with coagulated and settled water coming from a drinking water treatment plant and operated under dead-end and cross-flow operation modes. The experiments consisted inconsecutive permeation (20 min) alternated with BW with permeate water (1.0 min) (periodically chemically assisted with NaClO and NaOH) and followed by a two-stage CIP consisting first in an oxidising and basic step (NaClO and 30 NaOH) and second in an acidic step (citric acid). Feed, permeate, retentate (when present) and cleaning discharge streams were monitored for turbidity, total and dissolved organic carbon (TOC and DOC, respectively), UV 254 and inorganic ions (Al, Fe, P). DOC was frac- tionated by high-performance size exclusion chromatography to gain insight into the beha- viour of the different organic fractions. Results showed that both MF and UF membranes 35 successfully removed turbidity, Al and Fe, whereas UV 254 was moderately removed and TOC and DOC poorly removed, with removal percentages higher for UF than for MF. With regard to the organic fractions, the largest molecular weight compounds were moderately removed while the smallest organic fractions seemed to totally permeate through both membranes. The results also showed that foulants were poorly washed out from thePeer ReviewedPostprint (author's final draft

Reversibility of fouling on ultrafiltration membrane by backwashing and chemical cleaning: differences in organic fractions behaviour

Membrane fouling is an inherent phenomenon in ultrafiltration (UF) membrane processes, making it necessary to periodically perform backwashes (BW) and chemical cleanings in place (CIP) to restore the initial permeability of the membrane. The objective of this study was (1) to explore systematically the effect of distinct BW-related variables (BW transmembrane pressure, duration, frequency and composition) on the reversibility of UF membrane fouling and on the permeate quality (in terms of total organic carbon, turbidity and UV absorbance) over successive filtration/BW cycles; and (2) to identify which organic fractions were most removed by the membrane and, of these, which were most detached after BW, alkaline and oxidant CIP and acid CIP episodes. For this purpose, a bench-scale outside-in hollow fibre module operated under dead-end filtration mode at constant transmembrane pressure and treating settled water from a drinking water treatment plant was employed. Dissolved organic carbon fractionation was performed by high-performance size-exclusion chromatography. Results showed that, in general, the more intensive the BW was (in terms of high transmembrane pressure, shortened frequency and prolonged duration) the more effective it was in removing fouling from the membrane. Concerning the composition of the water used for the BW, the addition of NaClO led to maximum fouling reversibility, closely followed by the combination of NaOH+NaClO, while citric acid and NaOH contributed little compared to water alone. However, results also showed that irreversible fouling was never completely avoided whatever the BW regime applied, leading to a gradual increase in the total resistance over time. Larger differences in the behaviour of the different organic fractions were observed. UF membrane preferentially retained the heaviest fraction of biopolymers (BP), while the intermediate fraction of humic substances (HS) was removed at a lower percentage and the lighter fractions seemed to entirely pass through the UF membrane. The successive application of BW and CIPs resulted in the detachment from the membrane of a significant percentage of the retained BP, whereas only a modest percentage of the retained HS.Peer ReviewedPostprint (author's final draft

Techno-economic evaluation and comparison of PAC-MBR and ozonation-UV revamping for organic micro-pollutants removal from urban reclaimed wastewater

The presence of sewage-borne Organic Micro-Pollutants (OMP) in Wastewater Treatment Plants (WWTP) effluents represents an increasing concern when water is reclaimed for irrigation or even indirect potable reuse. During eighteen months, an innovative hybrid water reclamation scheme based on a Membrane Biological Reactor (MBR) enhanced with Powder Activated Carbon (PAC) was operated at pilot-scale (70 m3/d) in order to compare it with state-of-the art Wastewater Reclamation System (WWRS) also revamped with a final step of ozonation-UV. Removal of persistent OMP, water quality and treatment costs were evaluated and compared for the different treatment schemes. OMP removal efficiency results for the different schemes concluded that established technologies, such as physico-chemical and filtration systems as well as MBR, do not remove significantly (>15%) the most recalcitrant compounds. The upgrading of these two systems through the addition of ozonation-UV step and PAC dosing allowed improving average recalcitrant OMP removal to 85±2 and 75±5 %, respectively. In term of costs, PAC-MBR represents an increase of 37 % of costs regarding conventional systems but presents improvements of 50 % reduction in space and water quality. On the other hand, ozonation requires up to a 15% increase of foot-print; nevertheless, represents lower costs and lower carbon footprint. Ozonation-UV seems to be the best option for upgrading existing facilities, while PAC- MBR should be considered when space represents a critical limitation and produced water is reused for high water quality purposes.Postprint (author's final draft

Automatic submerged arc welding steam outlet nozzles to the shell of VVER 440 MW steam generator

18.00; Translated from Czech (Zvaranie 1987 v. 36(8) p. 231-235)SIGLEAvailable from British Library Document Supply Centre- DSC:9023.19(VR--3379)T / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Removal of dissolved organic carbon and bromide by a hybrid MIEX-ultrafiltration system: Insight into the behaviour of organic fractions

Dissolved organic carbon (DOC) and bromide (Br-) are principal precursors in the formation of halogenated disinfection by-products resulting from chlorination of drinking water. Their effective removal from water represents, thus, one of the main challenges faced by drinking water treatment plants worldwide. The objective of this study was to evaluate the performance of a pilot-scale hybrid system based on the patented magnetic ion-exchange resin (MIEX) combined with ultrafiltration (UF) in the removal of DOC and Br- from water. Two different doses of MIEX (1 mL/L and 3 mL/L) were applied and compared. Samples of feed water, UF permeate and tank solution were regularly collected to assess the system performance in terms of removal of DOC and Br-. DOC was characterised by high-performance size-exclusion chromatography (HPSEC) and 3D-fluorescence excitation-emission matrix (FEEM) to identify which organic fractions were preferentially removed by the MIEX/UF process. Results demonstrated that the hybrid MIEX/UF system was able to remove DOC and Br- from water. The evolution and extent of these removals depended on the MIEX dose applied, with percentage removals clearly increasing when the MIEX dose was increased from 1 mL/L to 3 mL/L. MIEX exhibited higher affinity toward DOC than toward Br-. Saturation of MIEX toward Br- was achieved short after the start of the experiment, while removal of DOC persisted until the end of the experiment. Fractionation of DOC by HPSEC indicated that the highest molecular weight fraction was mainly removed by size-exclusion by the UF membrane, while lower molecular weight fractions seemed to be better removed by ion-exchange on the MIEX resin. FEEM analysis revealed a poor affinity of MIEX toward microbial by-products, whereas fulvic and humic acid-like material were the most retained by MIEX.Peer Reviewe

The assessment of the sound insulation requirements for a large broadcasting studio, using a scale model Practical details

SIGLEAvailable from British Library Document Supply Centre- DSC:7383.85(BBC-RD--1987/21) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Characterising biofilm development on granular activated carbon used for drinking water production

Under normal operation conditions, granular activated carbon (GAC) employed in drinking water treatment plants (DWTPs) for natural organic matter (NOM) removal can be colonised by microorganisms which can eventually establish active biofilms. The formation of such biofilms can contribute to NOM removal by biodegradation, but also in clogging phenomena that can make necessary more frequent backwashes. Biofilm occurrence and evolution under full-scale-like conditions (i.e. including periodic backwashing) are still uncertain, and GAC filtration is usually operated with a strong empirical component. The aim of the present study was to assess the formation and growth, if any, of biofilm in a periodically backwashed GAC filter. For this purpose, an on-site pilot plant was assembled and operated to closely mimic the GAC filters installed in the DWTP in Sant Joan Despí (Barcelona, Spain). The study comprised a monitoring of both water and GAC cores withdrawn at various depths and times throughout 1 year operation. The biomass parameters assessed were total cell count by confocal laser scanning microscopy (CLSM), DNA and adenosine triphosphate (ATP). Visual examination of GAC particles was also conducted by high-resolution field emission scanning electron microscopy (FESEM). Additionally, water quality and GAC surface properties were monitored. Results provided insight into the extent and spatial distribution of biofilm within the GAC bed. To sum up, it was found that backwashing could physically detach bacteria from the biofilm, which could however build back up to its pre-backwashing concentration before next backwashing cycle.Peer ReviewedPostprint (published version

Removal of dissolved organic carbon and bromide by a hybrid MIEX-ultrafiltration system: Insight into the behaviour of organic fractions

Dissolved organic carbon (DOC) and bromide (Br-) are principal precursors in the formation of halogenated disinfection by-products resulting from chlorination of drinking water. Their effective removal from water represents, thus, one of the main challenges faced by drinking water treatment plants worldwide. The objective of this study was to evaluate the performance of a pilot-scale hybrid system based on the patented magnetic ion-exchange resin (MIEX) combined with ultrafiltration (UF) in the removal of DOC and Br- from water. Two different doses of MIEX (1 mL/L and 3 mL/L) were applied and compared. Samples of feed water, UF permeate and tank solution were regularly collected to assess the system performance in terms of removal of DOC and Br-. DOC was characterised by high-performance size-exclusion chromatography (HPSEC) and 3D-fluorescence excitation-emission matrix (FEEM) to identify which organic fractions were preferentially removed by the MIEX/UF process. Results demonstrated that the hybrid MIEX/UF system was able to remove DOC and Br- from water. The evolution and extent of these removals depended on the MIEX dose applied, with percentage removals clearly increasing when the MIEX dose was increased from 1 mL/L to 3 mL/L. MIEX exhibited higher affinity toward DOC than toward Br-. Saturation of MIEX toward Br- was achieved short after the start of the experiment, while removal of DOC persisted until the end of the experiment. Fractionation of DOC by HPSEC indicated that the highest molecular weight fraction was mainly removed by size-exclusion by the UF membrane, while lower molecular weight fractions seemed to be better removed by ion-exchange on the MIEX resin. FEEM analysis revealed a poor affinity of MIEX toward microbial by-products, whereas fulvic and humic acid-like material were the most retained by MIEX.Peer Reviewe

Pre-treatment of Llobregat River raw water through pressurised inside/out hollow fibre ultrafiltration membranes

The feasibility of raw river direct ultrafiltration, as an alternative to conventional drinking water treatment plant pre-treatment, was investigated at prototype scale (May–October 2011). A highly variable and challenging water resource was selected, in order to assess different scenarios, covering a broad range of conditions. The prototype was able to deal with conditions ranging from 20 to >800NTU successfully, without any chemical pre-treatment and consuming low amount of chemical reagents for cleaning purposes. The membranes’ performance proved to work better in terms of water production yield and resistance build up stability at medium and high turbidity episodes than at lower ones, probably due to a cake layer formation which prevented small binding organic species and particles reaching the membrane. Permeate quality, both in physico-chemical and microbiological terms, was independent of the feed water characteristics