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  • Long-term anaerobic digestion of microalgae grown in HRAP for wastewater treatment. Effect of microwave pretreatment

     Lopes del Rei Passos, Fabiana; Hernandez Marine, Mariona; Garcia Serrano, Joan; Ferrer Martí, Ivet
    Water research (Oxford)
    Vol. 49, p. 351-359
    DOI: 10.1016/j.watres.2013.10.013
    Date of publication: 2014-02-01
    Journal article

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    This paper describes the anaerobic digestion of microalgal biomass from high rate ponds in continuous anaerobic reactors for biogas production. With hydraulic retention times (HRT) of 15 and 20 days, the volatile solids (VS) removal did not exceed 30%, and the methane production rate ranged between 0.12 and 0.14 L CH4/L day. To improve process performance, microwave irradiation at 900 W for 3 min (specific energy similar to 70,000 kJ/kg VS) was applied as a pretreatment step. The VS removal increased to 40 and 45% at 15 and 20 days HRT, respectively. Consequently, the methane production rate increased to 0.16 and 0.20 L CH4/L day at 15 and 20 days HRT, respectively. Microscopic analysis confirmed cell wall damage, although generally without lysis, after irradiating microalgal biomass. However, the energy consumption was much higher than the extra energy production of the process. Indeed, microalgal biomass should not only be thickened but also dewatered if microwave irradiation was to be applied as a pretreatment to anaerobic digestion for biogas production. (C) 2013 Elsevier Ltd. All rights reserved.

  • Emerging organic contaminants in vertical subsurface flow constructed wetlands : Influence of media size, loading frequency and use of active aeration

     Avila Martin, Cristina; Nivala, Jaime; Olsson, Linda; Kassa, Kinfe; Headley, Tom; Mueller, Roland A.; Bayona, Josep M.; Garcia Serrano, Joan
    Science of the total environment
    Vol. 494, p. 211-217
    DOI: 10.1016/j.scitotenv.2014.06.128
    Date of publication: 2014-10-01
    Journal article

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    Four side-by-side pilot-scale vertical flow (VF) constructed wetlands of different designs were evaluated for the removal of eight widely used emerging organic contaminants from municipal wastewater (i.e. ibuprofen, acetaminophen, diclofenac, tonalide, oxybenzone, triclosan, ethinylestradiol, bisphenol A). Three of the systems were free-draining, with one containing a gravel substrate (VGp), while the other two contained sand substrate (VS1p and VS2p). The fourth system had a saturated gravel substrate and active aeration supplied across the bottom of the bed (VAp). All beds were pulse-loaded on an hourly basis, except VS2p, which was pulse-loaded every 2h. Each system had a surface area of 6.2m2, received a hydraulic loading rate of 95mm/day and was planted with Phragmites australis. The beds received an organic loading rate of 7-16gTOC/m2d. The sand-based VF (VS1p) performed significantly better (p<0.05) than the gravel-based wetland (VGp) both in the removal of conventional water quality parameters (TSS, TOC, NH4-N) and studied emerging organic contaminants except for diclofenac (85±17% vs. 74±15% average emerging organic contaminant removal for VS1p and VGp, respectively). Although loading frequency (hourly vs. bi-hourly) was not observed to affect the removal efficiency of the cited conventional water quality parameters, significantly lower removal efficiencies were found for tonalide and bisphenol A for the VF wetland that received bi-hourly dosing (VS2p) (higher volume per pulse), probably due to the more reducing conditions observed in that system. However, diclofenac was the only contaminant showing an opposite trend to the rest of the compounds, achieving higher elimination rates in the wetlands that exhibited less-oxidizing conditions (VS2p and VGp). The use of active aeration in the saturated gravel bed (VAp) generally improved the treatment performance compared to the free-draining gravel bed (VGp) and achieved a similar performance to the free-draining sand-based VF wetlands (VS1p).

    Four side-by-side pilot-scale vertical flow (VF) constructed wetlands of different designs were evaluated for the removal of eight widely used emerging organic contaminants from municipal wastewater (i.e. ibuprofen, acetaminophen, diclofenac, tonalide, oxybenzone, triclosan, ethinylestradiol, bisphenol A). Three of the systems were free-draining, with one containing a gravel substrate (VGp), while the other two contained sand substrate (VS1p and VS2p). The fourth system had a saturated gravel substrate and active aeration supplied across the bottom of the bed (VAp). All beds were pulse-loaded on an hourly basis, except VS2p, which was pulse-loaded every 2h. Each system had a surface area of 6.2m2, received a hydraulic loading rate of 95mm/day and was planted with Phragmites australis. The beds received an organic loading rate of 7-16gTOC/m2d. The sand-based VF (VS1p) performed significantly better (p<0.05) than the gravel-based wetland (VGp) both in the removal of conventional water quality parameters (TSS, TOC, NH4-N) and studied emerging organic contaminants except for diclofenac (85±17% vs. 74±15% average emerging organic contaminant removal for VS1p and VGp, respectively). Although loading frequency (hourly vs. bi-hourly) was not observed to affect the removal efficiency of the cited conventional water quality parameters, significantly lower removal efficiencies were found for tonalide and bisphenol A for the VF wetland that received bi-hourly dosing (VS2p) (higher volume per pulse), probably due to the more reducing conditions observed in that system. However, diclofenac was the only contaminant showing an opposite trend to the rest of the compounds, achieving higher elimination rates in the wetlands that exhibited less-oxidizing conditions (VS2p and VGp). The use of active aeration in the saturated gravel bed (VAp) generally improved the treatment performance compared to the free-draining gravel bed (VGp) and achieved a similar performance to the free-draining sand-based VF wetlands (VS1p).

  • Air temperature-driven CO2 consumption by rock weathering at short timescales: evidence from a Holocene lake sediment record

     Catalan, Jordi; Pla Rabes, Sergi; Garcia Serrano, Joan; Camarero, Lluis
    Geochimica et cosmochimica acta
    Vol. 136, p. 67-79
    DOI: 10.1016/j.gca.2014.04.005
    Date of publication: 2014-07
    Journal article

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    The role that air temperature plays in the interaction between atmospheric CO2 levels and continental rock weathering at relatively short time scales is still a matter of debate. Laboratory studies reveal a strong dependence of mineral dissolution on temperature, but field comparisons among watersheds under different climate conditions often indicate correlations with other environmental factors. Using a paleolimnological approach, here we show that there has been an extremely good coupling between rock weathering, water alkalinity (CO2 consumption), and air temperature during the last 10,000 years at sub-millennial time scales in a small watershed of silicate bedrock and scarce vegetation. The calculation of apparent activation energy for the weathering reaction (as a means to describe the temperature dependence of the process) provides a value (E-a = 67 +/- 7 kJ mol(-1)) that is comparable to those found for silicate rocks similar to those in the watershed in laboratory experiments and some field studies. Our results provide evidence that regulatory constraints between air temperature, atmospheric CO2 and silicate rock weathering can be fine-tuned at geological timescales and may not be negligible in the current context of global change. (C) 2014 Elsevier Ltd. All rights reserved.

  • NUMERICAL MODELLING OF CONSTRUCTED WETLANDS FOR WASTEWATER TREATMENT  Open access

     Samso Campa, Roger
    Universitat Politècnica de Catalunya
    Theses

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    Els aiguamolls construïts (AC) són sistemes de tractament d¿aigües residuals que aprofiten la capacitat de purificació dels aiguamolls naturals i n¿optimitzen el rendiment per complir regulacions d'abocaments tractats. Aquests sistemes són una alternativa d¿eficiència equiparable a les tecnologies de tractament convencionals per comunitats de fins a 2000PE, amb costos energètics i de manteniment menors. Malgrat això, els AC són poc fiables degut a la manca de coneixement sobre el seu funcionament i al fenomen de la colmatació. L¿enorme diversitat de tipologies i estratègies d¿operació dels AC, i el fet que operen a mercè de les condicions ambientals, fa que cada aiguamoll sigui únic en el seu gènere. En conseqüència, en força ocasions, els resultats d'estudis experimentals en AC no són extrapolables. Aquest fet converteix els models numèrics en una eina clau per estudiar el seu funcionament. Així, darrerament diversos models han proliferat com a eines de suport al disseny i operació dels AC i per comprendre millor els processos que s'hi donen. No obstant, el desenvolupament de models d¿AC es trobava una etapa embrionària. D¿acord amb això, els objectius del present treball han estat desenvolupar un model capaç de descriure els processos que tenen lloc en AC i aplicar-lo per millorar el coneixement sobre el seu funcionament a llarg termini. En aquest treball es desenvolupa un model d'AC en COMSOL Multiphysics, anomenat BIO_PORE. Permet simular flux subterrani i el transport de contaminants en medi porós. Implementa el model biocinètic Constructed Wetlands Model numero 1 (CWM1) per descriure l'eliminació de matèria orgànica, nitrogen i sofre així com el creixement dels bacteris habituals en AC. A més, BIO_PORE inclou dos paràmetres empírics (Mcap i Mbio_max) que milloren la descripció del creixement bacterià. El model es va calibrar amb dades experimentals d'un any de funcionament d¿un sistema pilot i l'efecte dels dos paràmetres introduïts es va avaluar amb un anàlisi de sensibilitat local. Posteriorment es va simular la dinàmica dels bacteris dins els AC. Al final del document es presenta una formulació per descriure la colmatació d¿origen biològic en medi porós i es realitza un experiment numèric per demostrar l¿impacte d¿aquest fenomen en la dinàmica dels AC. El principal resultat d¿aquest treball és el propi model BIO_PORE, que va permetre reproduir les concentracions efluents de contaminants durant tot un any de funcionament del sistema pilot. Mcap i Mbio_max van prevenir el creixement bacterià il¿limitat. Aquests dos paràmetres van ser responsables del bon ajust dels efluents simulats amb les mesurats experimentalment, fet que es va confirmar amb l¿anàlisi de sensibilitat posterior. Els resultats obtinguts amb el model es van utilitzar per construir un marc teòric conceptual, anomenat the Cartridge Theory, que descriu els patrons bàsics de funcionament dels AC de flux subsuperficial horitzontal. La teoria indica que les comunitats bacterianes es desplacen cap a la secció de sortida amb el temps, seguint l¿acumulació progressiva de sòlids inerts en la mateixa direcció. Segons aquest resultat els AC tenen una vida limitada, que correspon al temps després del qual les comunitats bacterianes es concentren tan aprop de la secció de sortida que la biomassa total no és capaç de proporcionar efluents de qualitat acceptable. La inclusió de la colmatació biològica del medi granular va ser requisit indispensable per reproduir correctament la distribució de bacteris i el flux i transport de contaminants dins els AC. Finalment, de resultes d'aquest treball també es fa evident que és necessari concentrar esforços en el desenvolupament del model BIO_PORE i en la seva calibració i validació.

    Constructed Wetlands (CWs) are a wastewater treatment technology that inherits the purification potential of natural wetlands and optimizes it to comply with regulations for treated discharges. CWs have become an equally performing alternative to conventional wastewater treatment technologies of communities up to 2000PE, with lower energy and maintenance costs. Despite their potential, CWs lack reliability, which holds back their full deployment in the territory. This fact results from the lack of understanding on their internal functioning and because they are prone to clogging. The enormous diversity of CWs typologies and operation strategies, and the fact that they operate at the mercy of the environmental conditions, makes each CW unique on its kind, and experimental studies are usually only representative of the studied system. This fact makes mathematical models essential to study their functioning. Several models for CWs have proliferated in the last dozen years to provide supporting tools for their design and operation as well as more insight into the treatment processes. However, compared to models utilized in similar disciplines, CWs models are still in an embrionary stage. Accordingly, the objectives of the current work were to develop a CWs model able to describe the most common processes taking place within CWs, and to use this model to shed light on the internal functioning of these systems in the long-term. The model, named BIO_PORE, was built in COMSOL Multiphysics and can simulate subsurface flow and pollutants transport in porous media. It also implements the biokinetic model Constructed Wetlands Model number 1 (CWM1) to describe the fate of organic matter, nitrogen and sulphur and the growth of the bacterial groups found in CWs. The model was calibrated with experimental data of a year of operation of a pilot system. Two empirical parameters (Mcap and Mbio_max ) were used to improve the description of bacterial growth obtained with CWM1 and to include the effects of solids accumulation on bacterial communities. The effect of these two parameters was evaluated using local sensitivity analysis. The model was later used to unveil the dynamics of bacterial communities within CWs. In addition, a theory was derived from simulation results, which aimed at describing the most basic functioning patterns of CWs based on the interaction between bacterial communities and accumulated solids. At the end of the document a mathematical formulation is presented to describe bioclogging and a numerical experiment is carried out to showcase its impact on simulation results. The main outcome of the current work was the BIO_PORE model. This model was able to reproduce effluent pollutant concentrations measured during an entire year of operation of the pilot system. Parameters Mcap and Mbio_max proved essential to prevent unlimited bacterial growth predicted by CWM1 near the inlet sections of CWs. These two parameters were also responsible for the good fitting with experimental data. This was confirmed with the sensitivity analysis, which demonstrated that they have a major impact on the model predictions for effluent COD and ammonia and ammonium nitrogen. The theory derived from simulation results indicated that bacteria move towards the outlet with time, following the accumulation of inert solids from inlet to outlet. This result may prove that CWs life-span is limited, corresponding to the time after which bacterial communities are pushed as much towards the outlet that their total biomass is not able to provide effluents with acceptable quality. The inclusion of bioclogging was a requisite to reproduce the bacterial distribution and fluid flow and pollutants transport within CWs. More work on the BIO_PORE model is required and more experimental data is necessary to calibrate and validate its results.

  • Biogas production from microalgae grown in wastewater: effect of microwave pretreatment

     Lopes del Rei Passos, Fabiana; Sole, Maria; Garcia Serrano, Joan; Ferrer Martí, Ivet
    Applied energy
    Vol. 108, p. 168-175
    DOI: 10.1016/j.apenergy.2013.02.042
    Date of publication: 2013-08
    Journal article

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    The aim of this study was to evaluate the effect of microwave pretreatment on the solubilisation and anaerobic digestion of microalgae-bacterial biomass cultivated in high rate algal ponds for wastewater treatment. The microwave pretreatment comprised three specific energies (21,800, 43,600 and 65,400. kJ/kg TS), combining three output power values with different exposure times. Response surface analysis showed that the main parameter influencing biomass solubilisation was the applied specific energy. Indeed, a similar solubilisation increase was obtained for the same specific energy, regardless of the output power and exposure time (280-350% for 21,800. kJ/kg TS, 580-610% for 43,600. kJ/kg TS and 730-800% for 65,400. kJ/kg TS). In biochemical methane potential tests, the initial biogas production rate (27-75% increase) and final biogas yield (12-78% increase) were higher with pretreated biomass. A linear correlation was found between biomass solubilisation and biogas yield.

  • Three-stage hybrid constructed wetland system for wastewater treatment and reuse in warm climate regions

     Avila Martin, Cristina; Garfi, Marianna; Garcia Serrano, Joan
    Ecological engineering
    Vol. 61, num. Part A, p. 43-49
    DOI: 10.1016/j.ecoleng.2013.09.048
    Date of publication: 2013-12
    Journal article

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    An experimental hybrid constructed wetland system consisting of 3 stages of different wetland configurations (i.e. two vertical flow beds (1.5m2 each) alternating feed-rest cycles followed by a horizontal subsurface flow (2m2) and a free water surface (2m2) wetlands in series) and the quality of its final effluent were evaluated for about one year. Mean overall removal rates were as 97% TSS, 78% COD, 91% BOD5, 94% NH4-N, 46% TN and 4% PO4-P. Vertical flow beds achieved high organic matter retention (77% BOD5) and great nitrification capacity (74% NH4-N removal). Although horizontal and free water surface wetlands accomplished little denitrification, they enabled water disinfection to produce an effluent suitable for various reuse applications. Authors suggest partial bypass from the Imhoff tank to the horizontal subsurface flow wetland so as to provide a carbon source to promote denitrification. The treatment system performed equally well in terms of organic matter and ammonium removal both in warm and cold seasons. However, reduced nitrate retention took place in horizontal and free water surface wetlands in the cold season, presumably due to low denitrification activity at low water temperatures. In general, the three-stage hybrid constructed wetland system has proven to constitute an appropriate ecotechnology for wastewater treatment and reuse in small communities of warm climate areas. © 2013 Elsevier B.V.

    tAn experimental hybrid constructed wetland system consisting of 3 stages of different wetland config-urations (i.e. two vertical flow beds (1.5 m2each) alternating feed-rest cycles followed by a horizontalsubsurface flow (2 m2) and a free water surface (2 m2) wetlands in series) and the quality of its finaleffluent were evaluated for about one year. Mean overall removal rates were as 97% TSS, 78% COD, 91%BOD5, 94% NH4-N, 46% TN and 4% PO4-P. Vertical flow beds achieved high organic matter retention (77%BOD5) and great nitrification capacity (74% NH4-N removal). Although horizontal and free water surfacewetlands accomplished little denitrification, they enabled water disinfection to produce an effluent suit-able for various reuse applications. Authors suggest partial bypass from the Imhoff tank to the horizontalsubsurface flow wetland so as to provide a carbon source to promote denitrification. The treatment sys-tem performed equally well in terms of organic matter and ammonium removal both in warm and coldseasons. However, reduced nitrate retention took place in horizontal and free water surface wetlands inthe cold season, presumably due to low denitrification activity at low water temperatures. In general, thethree-stage hybrid constructed wetland system has proven to constitute an appropriate ecotechnology for wastewater treatment and reuse in small communities of warm climate areas.

  • Bacteria distribution and dynamics in constructed wetlands based on modelling results

     Samso Campa, Roger; Garcia Serrano, Joan
    Science of the total environment
    Vol. 461-462, p. 430-440
    DOI: 10.1016/j.scitotenv.2013.04.073
    Date of publication: 2013-09
    Journal article

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    Bacteria communities growing in constructed wetlands play a major role on the removal of pollutants from wastewater and the presence of a stable community is a critical factor affecting their performance. With this work we aimed at finding how long it takes for bacterial communities to stabilise in constructed wetlands and at answering specific questions regarding their abundance, spatial distribution and their relative importance on the treatment processes. To this end the numerical model BIO_PORE was used to simulate the dynamics of 6 functional bacteria groups (heterotrophic, autotrophic nitrifying, fermenting, acetotrophic methanogenic, acetotrophic sulphate reducing and sulphide oxidising bacteria) within a wetland for a period of 3 years. Three indicators of bacterial stabilisation were used: 1) total biomass; b) effluent pollutant concentrations and c) Shannon's diversity index. Results indicate that aerobic bacteria dominated the wetland until the 80th day of operation. Anaerobic bacteria dominated the wetland from that moment and until the end of the studied period. Bacteria stability was reached between 400 and 700 days after starting operation. Once the wetland reached stability, sulphate reducing bacteria accounted for the highest biomass of all bacterial groups (46%). The distribution of bacterial communities obtained after bacterial stability is consistent with available experimental results, and was clearly controlled by dissolved oxygen (SO) concentrations and H2S toxicity. After stability, the progressive accumulation of inert solids pushed the location of the active bacteria zone towards the outlet section.

  • Integrated treatment of combined sewer wastewater and stormwater in a hybrid constructed wetland system in southern Spain and its further reuse

     Avila Martin, Cristina; Salas, Juan Jose; Martin, Isabel; Garcia Serrano, Joan; Aragón, Carlos A.
    Ecological engineering
    Vol. 50, p. 13-20
    DOI: 10.1016/j.ecoleng.2012.08.009
    Date of publication: 2013-06
    Journal article

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    An integrated pilot-scale treatment system consisting of a vertical subsurface flow (317 m2), a horizontal subsurface flow (229 m2) and a free water surface (240 m2) constructed wetlands operating in series for the treatment of a combined sewer effluent was put into operation and monitored over a period of about 1.5 years. The goal of the treatment system was to provide effluents suitable for various water reuse applications. Moreover, the influence of pulses of high flow resulting from several rain events over the treatment performance of the system was evaluated. An intensive sampling campaign was also carried out following an intense storm (45 mm in one-hour span) to have a further insight into the characteristics of the inflowing water at the early part of it or so-called `first-flush¿. Results under dry weather conditions showed a good performance on the removal of BOD5, COD and TSS taking place already in the vertical flow wetland (94, 85 and 90%, respectively). A high removal of total nitrogen occurred also in the vertical flow wetland (66%) suggesting both nitrification and denitrification to take place, presumably due to the existence of both aerobic and anoxic microenvironments within the bed. Removal of Escherichia coli along the treatment system was of almost 5 log units. To this respect, the horizontal flow and free water surface wetlands proved to be crucial treatment units to achieve a water quality suitable for further reuse (e.g. recharge of aquifers by percolation through the ground, silviculture and irrigation of green areas non accessible to the public). Although the occurrence of the storm event caused a prompt raise of COD and TSS within the first 30 min of rainfall (868 and 764 mg L-1, respectively), it was soon followed by a dilution effect. In general the storm events did not jeopardize the correct functioning of the system, proving its robustness for the treatment of a combined sewer effluent.

    An integrated pilot-scale treatment system consisting of a vertical subsurface flow (317 m2), a horizontal subsurface flow (229 m2) and a free water surface (240 m2) constructed wetlands operating in series for the treatment of a combined sewer effluent was put into operation and monitored over a period of about 1.5 years. The goal of the treatment system was to provide effluents suitable for various water reuse applications. Moreover, the influence of pulses of high flow resulting from several rain events over the treatment performance of the system was evaluated. An intensive sampling campaign was also carried out following an intense storm (45 mm in one-hour span) to have a further insight into the characteristics of the inflowing water at the early part of it or so-called ‘first-flush’. Results under dry weather conditions showed a good performance on the removal of BOD5, COD and TSS taking place already in the vertical flow wetland (94, 85 and 90%, respectively). A high removal of total nitrogen occurred also in the vertical flow wetland (66%) suggesting both nitrification and denitrification to take place, presumably due to the existence of both aerobic and anoxic microenvironments within the bed. Removal of Escherichia coli along the treatment system was of almost 5 log units. To this respect, the horizontal flow and free water surface wetlands proved to be crucial treatment units to achieve a water quality suitable for further reuse (e.g. recharge of aquifers by percolation through the ground, silviculture and irrigation of green areas non accessible to the public). Although the occurrence of the storm event caused a prompt raise of COD and TSS within the first 30 min of rainfall (868 and 764 mg L−1, respectively), it was soon followed by a dilution effect. In general the storm events did not jeopardize the correct functioning of the system, proving its robustness for the treatment of a combined sewer effluent.

  • Reactive transport simulation in a tropical horizontal subsurface flow constructed wetland treating domestic wastewater

     Mburu, N.; Rousseau, Diederik P. L.; Van Bruggen, J.J.A; Thumbi, G.; Llorens Ribes, Esther; Garcia Serrano, Joan; Lens, P.N.L
    Science of the total environment
    Vol. 449, p. 309-319
    DOI: 10.1016/j.scitotenv.2013.01.069
    Date of publication: 2013-04-01
    Journal article

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    A promising approach to the simulation of flow and conversions in the complex environment of horizontal subsurface flow constructed wetlands (HSSF-CWs) is the use of reactive transport models, in which the transport equation is solved together with microbial growth and mass-balance equations for substrate transformation and degradation. In this study, a tropical pilot scale HSSF-CW is simulated in the recently developed CWM1-RETRASO mechanistic model. The model predicts organic matter, nitrogen and sulfur effluent concentrations and their reaction rates within the HSSF-CW. Simulations demonstrated that these reactions took place simultaneously in the same (fermentation, methanogenesis and sulfate reduction) or at different (aerobic, anoxic and anaerobic) locations. Anaerobic reactions occurred over large areas of the simulated HSSF-CW and contributed (on average) to the majority (68%) of the COD removal, compared to aerobic (38%) and anoxic (1%) reactions...

  • E-01196

     Garcia Serrano, Joan
    Competitive project

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  • Impact of low temperature pretreatment on the anaerobic digestion of microalgal biomass

     Lopes del Rei Passos, Fabiana; Garcia Serrano, Joan; Ferrer Martí, Ivet
    Bioresource technology
    Vol. 138, p. 79-86
    DOI: 10.1016/j.biortech.2013.03.114
    Date of publication: 2013-06
    Journal article

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    The aim of this study was to investigate the effect of low temperature pretreatment on the anaerobic digestion of microalgal biomass grown in wastewater. To this end, microalgae were pretreated at low temperatures (55, 75 and 95. C) for 5, 10 and 15. h. Biomass solubilisation was enhanced with the pretreatment temperature and exposure time up to 10. h. The methane yield was improved by 14%, 53% and 62% at 55, 75 and 95. C, respectively; and was correlated with the solubilisation increase. The pretreatment at 95. C for 10. h increased VS solubilisation by 1188%, the initial methane production rate by 90% and final methane yield by 60% compared to untreated microalgae. With diluted biomass (~1% VS) positive energy balance was not likely to be attained. However, with concentrated biomass (2% VS) energy requirements may be covered and even surplus energy generated.

    The aim of this study was to investigate the effect of low temperature pretreatment on the anaerobic digestion of microalgal biomass grown in wastewater. To this end, microalgae were pretreated at low temperatures (55, 75 and 95 °C) for 5, 10 and 15 h. Biomass solubilisation was enhanced with the pretreatment temperature and exposure time up to 10 h. The methane yield was improved by 14%, 53% and 62% at 55, 75 and 95 °C, respectively; and was correlated with the solubilisation increase. The pretreatment at 95 °C for 10 h increased VS solubilisation by 1188%, the initial methane production rate by 90% and final methane yield by 60% compared to untreated microalgae. With diluted biomass (∼1% VS) positive energy balance was not likely to be attained. However, with concentrated biomass (>2% VS) energy requirements may be covered and even surplus energy generated.

  • BIO_PORE, a mathematical model to simulate biofilm growth and water quality improvement in porous media: Application and calibration for constructed wetlands

     Samso Campa, Roger; Garcia Serrano, Joan
    Ecological engineering
    Vol. 54, p. 116-127
    DOI: 10.1016/j.ecoleng.2013.01.021
    Date of publication: 2013-05
    Journal article

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    Reactive-transport models have been widely used to describe biogeochemical processes in subsurface environments. Horizontal subsurface-flow constructed wetlands fall in that category, and have experienced an exponential widespreading as an alternative wastewater treatment technique in recent years. As a result, the interest in modelling the processes occurring within these systems has proportionally increased. However, the functioning of wetlands is still poorly understood and the applicability of the available models is still limited. BIO_PORE model was built using COMSOL Multiphysics¿ platform to help accelerating the development of constructed wetland models and to shed light on their internal functioning. The biokinetic equations of Constructed Wetlands Model number 1 describe bacteria-induced degradation and transformation processes of organic matter, nitrogen and sulphur. Small changes of such equations were required in order to include attachment and detachment of influent particulate components.

  • Research and innovation on ecotechnologies applied to improve wastewater treatment efficiency

     Garcia Serrano, Joan; Salas Rodríguez, Juan José; Martin, Isabel; Vymazal, Jan
    Ecological engineering
    Vol. 50, p. 1-4
    DOI: 10.1016/j.ecoleng.2012.09.003
    Date of publication: 2013-01
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  • Emerging organic contaminant removal depending on primary treatment and operational strategy in horizontal subsurface flow constructed wetlands: Influence of redox

     Avila Martin, Cristina; Reyes, Carolina; Bayona, Josep M.; Garcia Serrano, Joan
    Water research (Oxford)
    Vol. 47, num. 1, p. 315-325
    DOI: 10.1016/j.watres.2012.10.005
    Date of publication: 2013-01-01
    Journal article

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    This study aimed at assessing the influence of primary treatment (hydrolytic upflow sludge blanket (HUSB) reactor vs. conventional settling) and operational strategy (alternation of saturated/ unsaturated phases vs. permanently saturated) on the removal of various emerging organic contaminants (i.e. ibuprofen, diclofenac, acetaminophen, tonalide, oxybenzone, bisphenol A) in horizontal subsurface flow constructed wetlands. For that purpose, a continuous injection experiment was carried out in an experimental treatment plant for 26 days. The plant had 3 treatment lines: a control line (settler-wetland permanently saturated), a batch line (settler-wetland operated with saturate/unsaturated phases) and an anaerobic line (HUSB reactor-wetland permanently saturated). In each line, wetlands had a surface area of 2.95 m2, a water depth of 25 cm and a granular medium D60 ¼ 7.3 mm, and were planted with common reed. During the study period the wetlands were operated at a hydraulic and organic load of 25 mm/d and about 4.7 g BOD/m2d, respectively. The injection experiment delivered very robust results that show how the occurrence of higher redox potentials within the wetland bed promotes the elimination of conventional quality parameters as well as emerging microcontaminants. Overall, removal efficiencies were always greater for the batch line than for the control and anaerobic lines, and to this respect statistically significantly differences were found for ibuprofen, diclofenac, oxybenzone and bisphenol A. As an example, ibuprofen, whose major removal mechanism has been reported to be biodegradation under aerobic conditions, showed a higher removal in the batch line (85%) than in the control (63%) and anaerobic (52%) lines. Bisphenol A showed also a great dependence on the redox status of the wetlands, finding an 89% removal rate for the batch line, as opposed to the control and anaerobic lines (79 and 65%, respectively). Furthermore, diclofenac showed a greater removal under a higher redox status (70, 48 and 32% in the batch, control and anaerobic lines). Average removal efficiencies of acetaminophen, oxybenzone and tonalide were almost >90% for the 3 treatment lines. The results of this study indicate that the efficiency of horizontal flow constructed wetland systems can be improved by using a batch operation strategy.

  • Effect of Design and Operational Factors on the Removal of Emerging Organic Contaminants in Constructed Wetlands for Wastewater Treatment  Open access

     Avila Martin, Cristina
    Department of Hydraulic, Maritime and Environmental Engineering, Universitat Politècnica de Catalunya
    Theses

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    L'aigua constitueix un recurs essencial per a la vida i la salut pública, i per tant la seva gestió sostenible és de vital importància. Per aquesta raó, el tractament de l'aigua residual i la seva reutilització constitueixen una pràctica clau en aquest plantejament. No obstant això, hi ha una preocupació generalitzada per la presència i possibles efectes adversos de contaminants emergents orgànics en el medi natural, els quals, en molts casos, no són eliminats completament a les plantes de tractament d'aigua residual convencionals. Els aiguamolls construïts han demostrat ser eficients en la seva capacitat per eliminar molts d'aquests contaminants, i representen una bona alternativa per al tractament d'aigua residual en petites comunitats ja que suposen baixos costos d'operació i manteniment. No obstant això, hi ha poca informació sobre les condicions (ja siguin les característiques de disseny o de les estratègies d'operació) que promouen l'eliminació d'aquests compostos en aquesta ecotecnologia.L¿objectiu d¿aquest treball és avaluar la capacitat de diferents configuracions d'aiguamolls construïts (vertical de flux subsuperficial, horitzontal de flux subsuperficial i de flux superficial) , així com l'efecte de diversos factors de disseny i funcionament (tractament primari, estratègia d'operació, freqüència d'alimentació, granulometria, ús de ventilació activa, càrrega hidràulica) en l'eliminació d'un conjunt de contaminants emergents orgànics, incloent tres fàrmacs antiinflamatoris no-esteroïdals (ibuprofè, diclofenac i acetaminofè), tres productes de la cura personal (tonalide , triclosan i oxibenzone) i dos disruptors endocrins (etinilestradiol i bisfenol A). Es van realitzar diversos assajos a escala experimental i pilot en sistemes d'aiguamolls construïts a Espanya i Alemanya. El rendiment de aiguamolls horitzontals de flux subsuperficial exhibeixen un patró estacional. L'ús d'un reactor anaerobi de flux ascendent per al tractament primari - en comptes d'un decantador convencional - va promoure un menor rendiment. En operar l'aiguamoll horitzontal en batch, alternant cicles de saturació i insaturació, va promoure l'existència de majors condicions redox, la qual cosa va millorar notablement l'eliminació dels compostos estudiats. La identificació d'un intermedi de degradació del bisfenol (en la línia operant en batch) suggereix que la biodegradació aeròbica podria constituir un mecanisme predominant d' eliminació d'aquesta substància quan prevalen condicions més oxidants.En aiguamolls de flux vertical, una freqüència d'alimentació més gran (bihorària vs. bihoraria) va reduir el rendiment d'alguns compostos. La presència de grava (4-8 mm) en lloc de sorra (1-3 mm) al llit principal dels aiguamolls verticals van exhibir una eficiència d¿eliminació significativament menor. Per contra, l'ús de ventilació activa en un aiguamoll de flux vertical saturat no va demostrar millorar l'eliminació del contaminants respecte al tipus convencional insaturat.Un sistema híbrid basat en una primera fase de l'aiguamoll vertical, un horitzontal de flux subsuperficial i un flux superficial en sèrie, ha demostrat ser una tecnologia molt robusta per al tractament d'aigua residual en petites comunitats, produint un efluent final adequat per a la seva reutilització per a diversos fins. L'eficiència general d'eliminació de contaminants emergents va ser molt alta (90 ± 11%), fins i tot sota càrregues hidràuliques altes, a causa de la combinació de diversos mecanismes d'eliminació abiòtics/biòtics (e.g. biodegradació, sorció, volatilització, hidròlisi, fotodegradació). Assaigs toxicològics realitzats juntament amb les injeccions d'antibiòtics durant la campanya de càrregues hidràuliques més altes van demostrar que la toxicitat general, estrogenicitat i activitats de tipus dioxina van ser eliminades satisfactòriament al llarg de les diferents unitats del sistema de tractament.

    Water of quality constitutes a scarce and essential resource for life and public health, and its sustainable management is of crucial importance. Thus, wastewater treatment, reuse and reclamation represent a key practice in that approach. Nevertheless, there is a generalized concern about the occurrence and possible adverse effects of emerging organic contaminants such as pharmaceutical and personal care products in the environment, which are often not well removed in conventional wastewater treatment plants. Constructed wetlands have shown promise in their ability to remove a variety of these contaminants, and represent a good alternative for wastewater treatment in small communities, having low operational and maintenance expenses. However, there is a need in increasing the knowledge about the conditions that promote the removal of these compounds within this ecotechnology. This thesis aims at evaluating the capacity of different wetland configurations (vertical subsurface flow, horizontal subsurface flow and free water surface), as well as the effect of various design and operational factors (primary treatment, operation strategy, loading frequency, grain size, use of active aeration, hydraulic loading rate) on the removal of a variety of emerging organic contaminants, including three non-steroidal anti-inflammatory drugs (ibuprofen, diclofenac and acetaminophen), three personal care products (tonalide, triclosan and oxybenzone) and two endocrine disrupting compounds (ethinylestradiol and bisphenol A). Assays were carried out at experimental and pilot scale in constructed wetland systems in Spain and Germany. In order to achieve approximate steady state conditions of the influent concentrations of the target emerging organic contaminants and to obtain a more reliable estimate of the removal efficiency of the systems, continuous injection experiments were performed at experimental-scale systems. The performance of horizontal subsurface flow wetlands exhibited a seasonal pattern. The use of a hydrolitic upflow sludge blanket reactor -as opposed to a conventional settler- for the primary treatment of wastewater resulted in reduced performance. Conversely, operating the horizontal wetlands in batch, alternating cycles of saturation and unsaturation, promoted the existence of higher redox conditions, enhancing the removal of target compounds. The identification of an intermediate product of bisphenol A (promoted by the operation in batch) suggests that aerobic biodegradation could constitute a principal removal mechanism of this substance when a higher redox status prevail. In VF wetlands, a higher loading frequency (bi-hourly vs. hourly) showed to perform significantly worse on the removal of some EOCs. The occurrence of gravel (4-8 mm) as opposed to sand (1-3 mm) in this type of systems exhibited a significantly lower treatment performance. Conversely, the use of active aeration in a saturated vertical flow wetland did not show to enhance contaminant removal in respect to the typical unsaturated vertical wetland. A hybrid treatment system based on a vertical wetland stage and a horizontal subsurface flow and free water surface wetlands in series has proved to be a very robust technology for wastewater treatment in small communities, producing a final effluent suitable for its reuse in various applications. Overall removal efficiency of emerging contaminants was very high (90 ± 11%), even under high hydraulic loads, presumaby due to the combination of various abiotic/biotic removal mechanisms (e.g. biodegradation, sorption, volatilization, hydrolysis, photodegradation). Toxicological assays performed together with the injection of antibiotics at high hydraulic loading rates showed that general toxicity, estrogenicity and dioxin-like activities were well removed along the different units of the treatment system.

    El agua constituye un recurso escaso y esencial para la vida y la salud pública, y por ende su gestión sostenible es de vital importancia. Por esta razón, el tratamiento del agua residual y su reutilización constituyen una práctica clave en este planteamiento. Sin embargo, existe una preocupación generalizada por la presencia y posibles efectos adversos de contaminantes emergentes orgánicos en el medio natural, tales como los fármacos y productos del cuidado personal, los cuales, en muchos casos, no son eliminados de manera eficiente en las plantas de tratamiento de agua residual convencionales. Los humedales construidos han demostrado ser eficientes en su capacidad para eliminar muchos de estos contaminantes, y representan una buena alernativa para el tratamiento de agua residual en pequeñas comunidades ya que suponen bajos costes de operación y mantenimiento. Sin embargo, existe poca información acerca de las condiciones (ya sean las características de diseño o las estrategias de operación) que promueven la eliminación de estos compuestos en esta ecotecnología. Este trabajo de investigación tiene como objetivo evaluar la capacidad de diferentes configuraciones de humedales construidos (vertical de flujo subsuperficial, horizontal de flujo subsuperficial y de flujo superficial), así como el efecto de varios factores de diseño y funcionamiento (tratamiento primario, estategia de operación, frecuencia de alimentación, granulometría, uso de aireación activa, carga hidráulica) en la eliminación de un conjunto de contaminantes emergentes orgánicos, incluyendo tres fármacos anti-inflamatorios no-esteroideos (ibuprofeno, diclofenaco y acetaminofen), tres productos del cuidado personal (tonalide, triclosan y oxibenzone) y dos disruptores endocrinos (etinilestradiol y bisfenol A). Se realizaron varios ensayos a escala experimental y piloto en sistemas de humedales construidos en Barcelona y Sevilla (España), y en Leipzig (Alemania). Para lograr aproximar condiciones de estabiidad en las concentraciones de contaminantes emergentes orgánicos en el afluente, y obtener así una estimación más fiable de la eficiencia de eliminación de los sistemas, se realizaron experimentos de inyección continua en los sistemas a escala experimental. La eliminación de los contaminantes estudiados en humedales horizontales de flujo subsuperficial exhibió un patrón estacional, posiblemente debido a una mayor biodegradación, volatilización e incorporación por las plantas a mayores temperaturas. En este tipo de humedal el uso de un reactor anaeróbico de flujo ascendente para el tratamiento primario -en vez de un decantador convecional- confirió condiciones más reducidas al sistema, lo cual promovió un menor rendimiento. En cambio, al operar el humedal horizontal en batch, alternando ciclos de saturación e insaturación, promovieron la existencia de mayores condiciones redox, lo cual mejoró notablemente la eliminación de los compuestos estudiados. La identificación de un intermedio de degradación del bisfenol A en este sistema de tratamiento (en la línea operando en batch) sugiere que la biodegradación aeróbica podría constituir un mecanismo predominante de elminación de esta sustancia cuando prevalencen conditiones más oxidantes. En humedales de flujo vertical, la frecuencia de alimentación (horaria/bihoraria) mostró diferencias significativas en la eliminación de algunos compuestos. Esto podria atribuirse a un menor tiempo de contacto y reducida renovación del oxígeno que se dan a frecuencias de alimentación menores. Además, la presencia de grava (4-8 mm) en lugar de arena (1-3 mm) en el lecho principal de los humedales verticales exhibió una eficiencia de elminación significativamente menor. El tamaño más pequeño de la arena se traduce en poros más pequeños que proporcionan una mejor capacidad de filtración, un área superficial mayor para el crecimiento de biofilm y un tiempo de contacto mayor. Por el contrario, el uso de aireación activa en un humedal de flujo vertical saturado no demostró mejorar la eliminación del contaminantes con respecto al tipo convencional insaturado. Un sistema de tratamiento híbrido basado en una primera fase de humedal vertical y un humedal horizontal de flujo subsuperficial y uno de flujo superficial en serie, ha demostrado ser una tecnología muy robusta para el tratamiento de agua residual en pequeñas comunidades, produciendo un efluente final adecuado para su reutilización para varios fines. La eficiencia general de eliminación de contaminantes emergentes fue muy alta (90 ± 11%), incluso bajo cargas hidráulicas altas, posiblemente debido a la combinación y sinergia de varios mecanismos de eliminación abióticos/bióticos (e.g., biodegradación, sorción, volatilización, hidrólisis, fotodegradación). Ensayos toxicológicos realizados junto con las inyecciones de antibióticos durante la campaña de cargas hidráulicas más altas demostraron que la toxicidad general, estrogenicidad y actividades de tipo dioxina fueron eliminadas satisfactoriamente a lo largo de las diferentes unidades del sistema de tratamiento.

    L'aigua constitueix un recurs escàs i essencial per a la vida i la salut pública, i per tant la seva gestió sostenible és de vital importància. Per aquesta raó, el tractament de l'aigua residual i la seva reutilització constitueixen una pràctica clau en aquest plantejament. No obstant això, hi ha una preocupació generalitzada per la presència i possibles efectes adversos de contaminants emergents orgànics en el medi natural, com ara els fàrmacs i productes de la cura personal, els quals, en molts casos, no són eliminats de manera eficient a les plantes de tractament d'aigua residual convencionals. Els aiguamolls construïts han demostrat ser eficients en la seva capacitat per eliminar molts d'aquests contaminants, i representen una bona alternativa per al tractament d'aigua residual en petites comunitats ja que suposen baixos costos d'operació i manteniment. No obstant això, hi ha poca informació sobre les condicions (ja siguin les característiques de disseny o de les estratègies d'operació) que promouen l'eliminació d'aquests compostos en aquesta ecotecnologia. Aquest treball de recerca té com a objectiu avaluar la capacitat de diferents configuracions d'aiguamolls construïts (vertical de flux subsuperficial, horitzontal de flux subsuperficial i de flux superficial) , així com l'efecte de diversos factors de disseny i funcionament (tractament primari, estratègia d'operació, freqüència d'alimentació, granulometria, ús de ventilació activa, càrrega hidràulica) en l'eliminació d'un conjunt de contaminants emergents orgànics, incloent tres fàrmacs antiinflamatoris no-esteroïdals (ibuprofè , diclofenac i acetaminofè ), tres productes de la cura personal (tonalide , triclosan i oxibenzone) i dos disruptors endocrins (etinilestradiol i bisfenol A). Es van realitzar diversos assajos a escala experimental i pilot en sistemes d'aiguamolls construïts a Barcelona i Sevilla (Espanya), i a Leipzig (Alemanya). Per aconseguir aproximar condicions d’estabilitat en les concentracions de contaminants emergents orgànics en l'afluent, i obtenir així una estimació més fiable de l'eficiència d'eliminació dels sistemes, es van realitzar experiments d'injecció contínua en els sistemes a escala experimental. L'eliminació dels contaminants estudiats en aiguamolls horitzontals de flux subsuperficial exhibeixen un patró estacional, possiblement a causa d'una major biodegradació, volatilització i incorporació per les plantes a majors temperatures. En aquest tipus d'aiguamoll l'ús d'un reactor anaerobi de flux ascendent per al tractament primari - en comptes d'un decantador convencional - conferir condicions més reduïdes al sistema, el qual va promoure un menor rendiment. En canvi, en operar l'aiguamoll horitzontal en batch, alternant cicles de saturació i insaturació, van promoure l'existència de majors condicions redox, la qual cosa va millorar notablement l'eliminació dels compostos estudiats. La identificació d'un intermedi de degradació del bisfenol A en aquest sistema de tractament (en la línia operant en batch) suggereix que la biodegradació aeròbica podria constituir un mecanisme predominant d' eliminació d'aquesta substància quan prevalen condicions més oxidants. En aiguamolls de flux vertical, la freqüència d'alimentació (horària/bihoraria) va mostrar diferències significatives en l'eliminació d'alguns compostos. Això es podria atribuir a un menor temps de contacte i reduïda renovació de l'oxigen que es donen a freqüències d'alimentació menors. A més , la presència de grava (4-8 mm) en lloc de sorra (1-3 mm) al llit principal dels aiguamolls verticals van exhibir una eficiència d’eliminació significativament menor. La mida més petita de la sorra es tradueix en porus més petits que proporcionen una millor capacitat de filtració, una àrea superficial més gran per al creixement de biofilm i un temps de contacte més gran. Per contra, l'ús de ventilació activa en un aiguamoll de flux vertical saturat no va demostrar millorar l'eliminació del contaminants respecte al tipus convencional insaturat. Un sistema de tractament híbrid basat en una primera fase de l'aiguamoll vertical i un aiguamoll horitzontal de flux subsuperficial i un flux superficial en sèrie, ha demostrat ser una tecnologia molt robusta per al tractament d'aigua residual en petites comunitats, produint un efluent final adequat per a la seva reutilització per a diversos fins. L'eficiència general d'eliminació de contaminants emergents va ser molt alta (90 ± 11%), fins i tot sota càrregues hidràuliques altes, possiblement a causa de la combinació i sinergia de diversos mecanismes d'eliminació abiòtics/biòtics (e.g. biodegradació, sorció, volatilització, hidròlisi, fotodegradació). Assaigs toxicològics realitzats juntament amb les injeccions d'antibiòtics durant la campanya de càrregues hidràuliques més altes van demostrar que la toxicitat general, estrogenicitat i activitats de tipus dioxina van ser eliminades satisfactòriament al llarg de les diferents unitats del sistema de tractament.

  • Safeguarding Water resources in INdia with Green and Sustainable

     Garfi, Marianna; Avila Martin, Cristina; Garcia Serrano, Joan
    Competitive project

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  • FP7-308336-NaWaTech - Natural Water Systems and Treatment Technologies to cope with Water Shortages in Urbanised Areas in India

     Garfi, Marianna; Garcia Serrano, Joan; Puigagut Juarez, Jaume; Avila Martin, Cristina
    Competitive project

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  • Safeguarding Water resources in INdia with Green and Sustainable

     Garfi, Marianna; Garcia Serrano, Joan; Avila Martin, Cristina
    Competitive project

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  • Effect of climatic conditions, season and wastewater quality on contaminant removal efficiency of two experimental constructed wetlands in different regions of Spain

     Garfi, Marianna; Pedescoll Albacar, Anna; Bécares Mantecón, Eloy; Hijosa Valsero, Maria; Sidrach Cardona, A.; Garcia Serrano, Joan
    Science of the total environment
    Vol. 437, p. 61-67
    DOI: 10.1016/j.scitotenv.2012.07.087
    Date of publication: 2012-10-15
    Journal article

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    The aim of this study was to examine the effects of climate, season and wastewater quality on contaminant removal efficiency of constructed wetlands implemented in Mediterranean and continental-Mediterranean climate region of Spain. To this end, two experimental horizontal subsurface flow constructed wetlands located in Barcelona and León (Spain) were compared. The two constructed wetland systems had the same experimental set-up. Each wetland had a surface area of 2.95 m2, a water depth of 25 cm and a granular medium of D60=7.3 mm, and was planted with Phragmites australis. Both systems were designed in order to operate with a maximum organic loading rate of 6 gDBO m−2 d−1. Experimental systems operated with a hydraulic loading rate of 28.5 and 98 mm d−1 in Barcelona and León, respectively. Total suspended solids, biochemical oxygen demand and ammonium mass removal efficiencies followed seasonal trends, with higher values in the summer (97.4% vs. 97.8%; 97.1% vs. 96.2%; 99.9% vs. 88.9%, in Barcelona and León systems, respectively) than in the winter (83.5% vs. 74.4%; 73.2% vs. 60.6%; 19% vs. no net removal for ammonium in Barcelona and León systems, respectively). During the cold season, biochemical oxygen demand and ammonium removal were significantly higher in Barcelona system than in León, as a result of higher temperature and redox potential in Barcelona. During the warm season, statistical differences were observed only for ammonium removal. Results showed that horizontal subsurface flow constructed wetland is a successful technology for both regions considered, even if winter seemed to be a critical period for ammonium removal in continental climate regions.

  • Effect of climate and wastewater quality on removal efficiency in two identical experimental constructed wetlands located in different sites

     Garfi, Marianna; Bécares Mantecón, Eloy; Pedescoll Albacar, Anna; Hijosa Valsero, Maria; Sidrach Cardona, A.; Garcia Serrano, Joan
    Science of the total environment
    Vol. 437, num. 15, p. 61-67
    Date of publication: 2012
    Journal article

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  • Performance of sludge treatment wetlands using different plant species and porous media

     Uggetti, Enrica; Ferrer Martí, Ivet; Carretero Ariza, Javier; Garcia Serrano, Joan
    Journal of hazardous materials
    Vol. 217-218, p. 263-270
    DOI: 10.1016/j.jhazmat.2012.03.027
    Date of publication: 2012-05-30
    Journal article

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  • Quantification of greenhouse gas emissions from sludge treatment wetlands

     Uggetti, Enrica; Garcia Serrano, Joan; Lind, S.E.; Martikainen, P.J.; Ferrer Martí, Ivet
    Water research (Oxford)
    Vol. 46, num. 6, p. 1755-1762
    DOI: 10.1016/j.watres.2011.12.049
    Date of publication: 2012-04-15
    Journal article

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  • Characteristics of biosolids from sludge treatment wetlands for agricultural reuse

     Uggetti, Enrica; Ferrer Martí, Ivet; Nielsen, Steen; ARIAS, CARLOS; Brix, Hans; Garcia Serrano, Joan
    Ecological engineering
    Vol. 40, p. 210-216
    DOI: 10.1016/j.ecoleng.2011.12.030
    Date of publication: 2012-03
    Journal article

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  • Dewatering model for optimal operation of sludge treatment wetlands

     Uggetti, Enrica; Argilaga, A.; Ferrer Martí, Ivet; Garcia Serrano, Joan
    Water research (Oxford)
    Vol. 46, num. 2, p. 335-344
    DOI: 10.1016/j.watres.2011.10.040
    Date of publication: 2012-02-01
    Journal article

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  • A comparison of in situ constant and falling head permeameter tests to assess the distribution of clogging within horizontal subsurface flow constructed wetlands

     Pedescoll Albacar, Anna; Knowles, P.R.; Davies, Peter A; Garcia Serrano, Joan; Puigagut Juarez, Jaume
    Water, air and soil pollution
    Vol. 223, num. 5, p. 2263-2275
    DOI: 10.1007/s11270-011-1021-4
    Date of publication: 2012-06
    Journal article

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  • Carbon footprint of sludge treatment reed beds

     Uggetti, Enrica; Ferrer Martí, Ivet; ARIAS, CARLOS; Brix, Hans; Garcia Serrano, Joan
    Ecological engineering
    Vol. 44, p. 298-302
    DOI: 10.1016/j.ecoleng.2012.04.020
    Date of publication: 2012-07
    Journal article

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  • Biogas production from microalgae grown in wastewater: effect of microwave pretreatment

     Lopes del Rei Passos, Fabiana; Garcia Serrano, Joan; Ferrer Martí, Ivet
    Young Algaeneers Symposium
    p. 74
    Presentation's date: 2012-06-14
    Presentation of work at congresses

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  • Producción de biogás a partir de microalgas cultivadas en aguas residuales

     Ferrer Martí, Ivet; Lopes del Rei Passos, Fabiana; Garcia Serrano, Joan
    Reunión de la Mesa Española de Tratamiento de Aguas
    p. 151-152
    Presentation's date: 2012-10-05
    Presentation of work at congresses

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  • Microalgae production and wastewater treatment in high rate algal ponds and low-cost tubular photobioreactors

     Lopes del Rei Passos, Fabiana; Garcia Serrano, Joan; Ferrer Martí, Ivet
    Young Algaeneers Symposium
    p. 24
    Presentation's date: 2012-06-15
    Presentation of work at congresses

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  • Biotechnology for Africa¿s sustainable water supply

     Garfi, Marianna; Avila Martin, Cristina; Garcia Serrano, Joan
    Competitive project

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  • SEWAGE SLUDGE TREATMENT IN CONSTRUCTED WETLANDS. Technical, economic and environmental aspects applied to small communities of the Mediterranean Region.  Open access  awarded activity

     Uggetti, Enrica
    Universitat Politècnica de Catalunya
    Theses

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    During the last years, the implementation of new Wastewater Treatment Plants has lead to a significant increase of sludge production. As a response, sludge valorisation in agriculture is the preferred option nowadays, ensuring the return of organic constituents, nutrients and microelements to crop fields. In practice, sludge treatments should provide a final product suitable for land application, with reasonable investment as well as operational and maintenance costs. In this sense, sludge treatment wetlands (STW) appear as a suitable technology for sludge management from an economic and environmental point of view. The main objective of this research work was to assess the suitability of STW for sludge management; with special focus on small communities of the Mediterranean Region. To this end, technical, environmental and economic aspects of the treatment were studied in 3 full-scale systems and in a pilot plant located in Catalonia. A comparison with conventional treatments for sludge management is presented in order to establish the most favourable solution for the Catalan context. As the final result from this work, design and operation criteria are proposed as a guide for STW implementation in small Mediterranean communities. The study of the performance of the full-scale STW suggests good treatment efficiency. Moisture content was reduced by 16-30%, reaching efficiencies similar to those of conventional dewatering technologies. On the other hand, VS were reduced up to 30-49%VS/TS, suggesting the progressive sludge stabilisation and mineralisation. Similar values were found at the end of the treatment in the pilot plant. In this case the sludge volume was reduced around 80% and TS increased up to 16-24%. However, the observed VS reduction (up to 50%VS/TS) after 2 months without feeding, indicates that longer resting periods should be applied in order to increase mineralisation of the sludge. A finite element model able to simulate sludge dewatering in STW was developed by combining the evapotranspiration (ET) and the Terzaghi¿s consolidation theory representing water percolation. The model allows for the determination of the most appropriate feeding frequency as a function of the sludge height stored on the wetland. Similarly, the sludge loading rate is determined as a function of ET, feeding frequency and sludge height. On the whole, the model implemented is a useful tool for the establishment of standardised criteria of STW operation. The characterisation of the final product from the pilot plant and from three full-scale systems demonstrated the suitability of biosolids as organic fertilisers. DRI values indicated the partial stabilisation of the product. Moreover, the absence of phytotoxicity and the heavy metals concentrations below the legal thresholds confirmed their viability to be reused in agriculture. However, in the pilot plant, pathogens were still present after 2 resting months, confirming the necessity of a longer resting period. Monitoring the stabilisation degree as phytotoxicity, heavy metals and pathogens' concentration during the final resting period would help optimising its duration. Looking at the environmental aspects, the static chamber method was successfully adapted to the determination of gas emissions from STW. Aerobic conditions before sludge feeding, characterised by low methane emissions and high nitrous oxide emissions, were strongly altered by fresh sludge feeding, which increases CH4 emissions and reduces N2O emissions. According to the measured emissions, the Global warming potential of STW corresponds to 17kgCO2eq/PE¿y, which is from 2 to 9 times lower than that of sludge centrifugation and transport. Besides,the economic and environmental assessment indicates STW with direct land application as the most cost-effective technique, which is also characterised by the lowest environmental impact.Thus STW are the best solution to manage waste sludge in decentralised small communities.

  • Bacterial transformation and biodegradation processes simulation in horizontal subsurface flow constructed wetlands using CWM1-RETRASO

     Llorens, E.; Saaltink, Maarten Willem; Poch, Manel; Garcia Serrano, Joan
    Bioresource technology
    Vol. 102, num. 2, p. 928-936
    DOI: 10.1016/j.biortech.2010.09.038
    Date of publication: 2011-01-01
    Journal article

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    The performance and reliability of the CWM1-RETRASO model for simulating processes in horizontal subsurface flow constructed wetlands (HSSF CWs) and the relative contribution of different microbial reactions to organic matter (COD) removal in a HSSF CW treating urban wastewater were evaluated. Various different approaches with diverse influent configurations were simulated. According to the simulations, anaerobic processes were more widespread in the simulated wetland and contributed to a higher COD removal rate [72–79%] than anoxic [0–1%] and aerobic reactions [20–27%] did. In all the cases tested, the reaction that most contributed to COD removal was methanogenesis [58–73%]. All results provided by the model were in consonance with literature and experimental field observations, suggesting a good performance and reliability of CWM1-RETRASO. According to the good simulation predictions, CWM1- RETRASO is the first mechanistic model able to successfully simulate the processes described by the CWM1 model in HSSF CWs.

  • Clogging in subsurface-flow treatment wetlands: Occurrence and contributing factors

     Knowles, Paul; Dotro, Gabriela; Nivala, Jaime; Garcia Serrano, Joan
    Ecological engineering
    Vol. 37, num. 2, p. 99-112
    DOI: 10.1016/j.ecoleng.2010.08.005
    Date of publication: 2011-02
    Journal article

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  • Technical, economic and environmental assessment of sludge treatment wetlands

     Uggetti, Enrica; Ferrer Martí, Ivet; Molist, Jordi; Garcia Serrano, Joan
    Water research (Oxford)
    Vol. 45, num. 2, p. 573-582
    DOI: 10.1016/j.watres.2010.09.019
    Date of publication: 2011-01
    Journal article

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    Sludge treatment wetlands (STW) emerge as a promising sustainable technology with low energy requirements and operational costs. In this study, technical, economic and environmental aspects of STW are investigated and compared with other alternatives for sludge management in small communities (<2000 population equivalent). The performance of fullscale STW was characterised during 2 years. Sludge dewatering increased total solids (TS) concentration by 25%, while sludge biodegradation lead to volatile solids around 45% TS and DRI24h between 1.1 and 1.4 gO2/kgTS h, suggesting a partial stabilisation of biosolids. In the economic and environmental assessment, four scenarios were considered for comparison: 1) STW with direct land application of biosolids, 2) STW with compost post-treatment, 3) centrifuge with compost post-treatment and 4) sludge transport to an intensive wastewater treatment plant. According to the results, STW with direct land application is the most cost-effective scenario, which is also characterised by the lowest environmental impact. The life cycle assessment highlights that global warming is a significant impact category in all scenarios, which is attributed to fossil fuel and electricity consumption; while greenhouse gas emissions from STW are insignificant. As a conclusion, STW are the most appropriate alternative for decentralised sludge management in small communities.

  • Mechanical resistance properties of gravel used in subsurface flow constructed wetlands: implications for clogging

     Pedescoll Albacar, Anna; Lopes del Rei Passos, Fabiana; Alba, Elisenda; Garcia Serrano, Joan; Puigagut Juarez, Jaume
    Water science and technology
    Vol. 63, num. 9, p. 1801-1807
    DOI: 10.2166/wst.2011.380
    Date of publication: 2011-05-05
    Journal article

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    Gravel constitutes the filter medium in subsurface flow constructed wetlands (SSF CWs) and its porosity and hydraulic conductivity decrease over time (clogging), limiting the lifespan of the systems. Using gravel of poor quality accelerates clogging in wetlands. In this study, gravel samples from six different wetland systems were compared with regards to their mineral composition and mechanical resistance properties. Results showed that both mineralogy and texture are related to mechanical resistance. Accordingly, gravel with high content of quartz (480%) showed a lower percentage of broken particles (0.18–1.03%) than those with lower content of quartz (2.42–4.56% media broken). Although granite is formed by high durability minerals, its non-uniform texture results in a lower resistance to abrasion (ca. 10% less resistance than calcareous gravel). Therefore, it is recommended to use gravels composed mainly of quartz or, when it is not available, limestone gravels (rounded and uniform) are recommended instead. The resistance to abrasion (LAA test) seems to be a good indicator to determine the mechanical properties of gravels used in CWs. It is recommended to use gravels with LAA below 30% in order to avoid a rapid clogging due to gravel crumbling and subsequent mineral solids accumulation.

  • Contaminant removal efficiency depending on primary treatment and operational strategy in horizontal subsurface flow treatment wetlands

     Pedescoll Albacar, Anna; Corzo Hernandez, Angelica; Alvarez San Millan, Eduardo; Puigagut Juarez, Jaume; Garcia Serrano, Joan
    Ecological engineering
    Vol. 37, num. 2, p. 372-380
    DOI: 10.1016/j.ecoleng.2010.12.011
    Date of publication: 2011-02
    Journal article

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  • Evaluation of primary treatment and loading regimes in the removal of pharmaceuticals and personal care products from urban wastewaters by subsurface-flow constructed wetlands

     Hijosa Valsero, Maria; Matamoros, Victor; Pedescoll Albacar, Anna; Martin Villacorta, Javier; BÉCARES MANTECÓN, ELOY; Garcia Serrano, Joan; Bayona, Josep M.
    International journal of environmental analytical chemistry
    Vol. 91, num. 7-8, p. 632-653
    DOI: 10.1080/03067319.2010.526208
    Date of publication: 2011-05
    Journal article

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  • The effect of primary treatment and flow regime on clogging development in horizontal subsurface flow constructed wetlands: an experimental evaluation

     Pedescoll Albacar, Anna; Corzo, Angelica; Alvarez, Eduardo; Garcia Serrano, Joan; Puigagut Juarez, Jaume
    Water research (Oxford)
    Vol. 45, num. 12, p. 3579-3589
    DOI: 10.1016/j.watres.2011.03.049
    Date of publication: 2011-06
    Journal article

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  • Advances in pollutant removal processes and fate in natural and constructed wetlands

     Garcia Serrano, Joan
    Ecological engineering
    Vol. 37, num. 5, p. 663-665
    DOI: 10.1016/j.ecoleng.2011.02.012
    Date of publication: 2011-05
    Journal article

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  • Influence of design, physico-chemical and environmental parameters on pharmaceuticals and fragrances removal by constructed wetlands

     Hijosa Valsero, Maria; Matamoros, Victor; Sidrach Cardona, A.; Pedescoll Albacar, Anna; Martin Villacorta, Javier; Garcia Serrano, Joan; Bayona, Josep M.; BÉCARES MANTECÓN, ELOY
    Water science and technology
    Vol. 63, num. 11, p. 2527-2534
    DOI: 10.2166/wst.2011.500
    Date of publication: 2011
    Journal article

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  • Economic valuation of a created wetland fed with treated wastewater located in a peri-urban park in Catalonia, Spain

     Alfranca Burriel, Oscar; Garcia Serrano, Joan; Varela, Hector
    Water science and technology
    Vol. 63, num. 5, p. 892-899
    DOI: 10.2166/wst.2011.267
    Date of publication: 2011
    Journal article

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  • CWM1 implementation in RetrasoCodeBright: first results using horizontal subsurface flow constructed wetland data, Chemical Engineering Journal

     Llorens, Llorens, E.; Saaltink, Maarten Willem; Garcia Serrano, Joan
    Chemical engineering journal
    Vol. 166, num. 1, p. 224-232
    DOI: 10.1016/j.cej.2010.10.065
    Date of publication: 2011-01-01
    Journal article

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    Constructed Wetland Model No. 1 (CWM1) processes were implemented within RetrasoCodeBright (RCB) to simulate hydraulics and reactive transport as well as the main biodegradation and transformation processes in horizontal subsurface flow constructed wetlands (SSF CWs). New values for some stoichiometric and kinetic coefficients were determined in the calibration step in order to obtain more realistic biochemical transformation and degradation processes. The model was checked and then tested for a horizontal SSF CW operating with different hydraulic loading rates [20, 36 and 45 mm/d]. Modifications to the CWM1 formulation had a negligible effect on the good fitting of measured and simulated data. However, changes in stoichiometric and kinetic parameters positively affected performance. Bacterial concentrations defined as initial conditions proved to be a variable requiring attention in the calibration. In terms of pollutant concentrations in effluent, simulated data corresponded well with data measured in most cases evaluated. The quality of the results obtained suggests that CWM1-RETRASO, the resulting model, is a potential tool for studying hydraulics, reactive transport and the main biochemical transformation and degradation processes for organic matter, nitrogen and sulphur in horizontal SSF CWs.

  • Performance evaluation of eight years experience of constructed wetland systems in Catalonia as alternative treatment for small communities

     Vera, I.; Garcia Serrano, Joan; Sáez, K.; Moragas, L.; Vidal, G.
    Ecological engineering
    Vol. 37, num. 2, p. 364-371
    DOI: 10.1016/j.ecoleng.2010.11.031
    Date of publication: 2011-02
    Journal article

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  • Water.cat - catalan r&d network for water technologies

     Garcia Serrano, Joan; Blade i Castellet, Ernest; Espino Infantes, Manel; Puigagut Juarez, Jaume
    Competitive project

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  • Clogging in Horizontal Subsurface Flow Constructed Wetlands. Mesures, design factors and prevention strategies  Open access  awarded activity

     Pedescoll Albacar, Anna
    Department of Agri-Food Engineering and Biotechnology, Universitat Politècnica de Catalunya
    Theses

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    Constructed wetlands are alternative systems to conventional wastewater treatment for small communities (up to 2000 PE). This is mainly due to that operation and maintenance costs are reduced. Despite the advantages, the clogging of the bed is the most important trouble encountered by the managers of subsurface flow wetlands treatment systems. The solids accumulation in the interstitial spaces of the gravel over time causes the decrease of both, hydraulic conductivity and porosity. This leads in the development of preferential paths and short-circuiting of the water through the wetland, which converge in overland flow and contaminant removal efficiency decrease. Therefore, clogging is the main limiting factor of the life span of a subsurface flow constructed wetland. The strategies to reverse clogging imply important economic investments. Generally, the most widespread option is the replacement of gravel. Hence the need to measure realibly the degree of clogging of a system in order to identify the factors that influence this phenomenon and to search new configurations and strategies to delay its progress, thus operations needed to reverse it. Therefore, the aims of this thesis must contribute to establish new design criteria and operation of horizontal subsurface flow constructed wetlands to minimize clogging processes without reducing the contaminant removal efficiency. Then, the objectives were to compare a method to measure hydraulic conductivity in situ, based on falling head permeameter, in order to determine the state of clogging of wetlands and its horizontal distribution; to determine the most suitable indicator to assess clogging in horizontal subsurface flow wetlands; to identifie new design and operation parameters likely to cause or encourage the clogging of the filter medium; and to analyse two new configurations in a pilot scale system in terms of contaminant removal and clogging development. Among the different clogging indicators analysed (drenable porosity, hydraulic conductivity, accumulated solids and effective volume from a tracer test), hydraulic conductivity seems to be the best one. Firstly, because hydraulic conductivity provides information about the hydraulic behaviour inside the bed, and linked appropriately with the accumulated solids (a correlation of 74.5% was found between both indicators). Secondly, because its application in full-scale wetlands is more straightforward than other techniques.

    Los humedales construidos son una alternativa al tratamiento convencional de agua residual para pequeños municipios (hasta 2000 hab-eq) ya que son fáciles de operar y mantener y tienen un coste de explotación bajo. El mayor inconveniente a que se enfrentan los explotadores de sistemas de tratamiento con humedales subsuperficiales es la colmatación del lecho. Con el tiempo, la acumulación de sólidos de diversa naturaleza en los espacios intersticiales del medio filtrante, provoca la disminución de la conductividad hidráulica y la porosidad iniciales de la grava. Esto conduce al desarrollo de caminos preferenciales y cortocircuitos en el curso del agua que convergen en la aparición de agua en superficie. A la larga, esto puede comprometer la capacidad depurativa del sistema. Por ello, la colmatación supone el factor limitante de la vida útil de un humedal construido. Las estrategias para solventar la colmatación, una vez se ha producido, son costosas y pasan por realizar inversiones no despreciables. Generalmente la opción más extendida es el cambio del material granular. De ahí la necesidad de medir, de manera fiable, en qué grado un sistema está colmatado, identificar los factores que influyen en el fenómeno e indagar en nuevas configuraciones y estrategias que permitan retrasar el avance de la colmatación y consigo, aplazar las intervenciones necesarias para devolver al sistema un estado óptimo de funcionamiento. Los objetivos de esta tesis doctoral han de contribuir a establecer nuevos criterios de diseño y operación de humedales construidos de flujo subsuperficial horizontal para minimizar, o cuanto menos retrasar, la colmatación de estos sistemas, sin mermar la eficiencia de eliminación de contaminantes del agua residual. Por ello, los objetivos son cuantificar la precisión y exactitud de un método de medición in situ de la conductividad hidráulica, basado en el permeámetro de carga variable, para la determinación del grado de colmatación de un lecho y la distribución horizontal de la misma; estudiar la idoneidad de diferentes indicadores de la colmatación de un humedal de flujo subsuperficial horizontal; evaluar la incidencia de diferentes factores de diseño y operación de humedales de flujo subsuperficial horizontal en el proceso de la colmatación; y caracterizar (en términos de eficiencia de eliminación de contaminantes y de evolución de la colmatación) dos nuevas configuraciones de humedales construidos a escala piloto.

    Els aiguamolls construïts són una alternativa al tractament convencional d’aigua residual per a petits municipis (fins 2000 hab-eq) degut, principalment, a la facilitat en llur operació i manteniment y a les reduïdes despeses d’explotació. L’inconvenient més important amb què es troben els explotadors de sistemes de tractament amb aiguamolls subsuperficials és la colmatació del llit. Al llarg del temps, l’acumulació de sòlids de diversa natura en els espais intersticials de la grava, provoca la disminució de la conductivitat hidràulica i la porositat inicials. Això condueix al desenvolupament de camins preferencials i curtcircuits en el curs de l’aigua a través de l’aiguamoll, que convergeixen en l’aparició d’aigua en superfície, i que, a llarg termini pot comprometre la capacitat depurativa del sistema. Per això, la colmatació suposa el factor limitant de la vida útil d’un aiguamoll construït. Les estratègies per a fer front a la colmatació, un cop s’ha produït, passen per realitzar inversions econòmiques gens menyspreables. Generalment, l’opció més extesa és la reposició del material granular. D’aquí neix la necessitat de mesurar, de manera fiable, el grau de colmatació d’un sistema, d’identificar aquells factors que influeixen en el fenomen y qüestionar noves configuracions y estratègies que permetin retardar l’avenç de la colmatació, i per tant ajornar les intervencions necessàries per tornar al sistema a l’estat òptim de funcionament. Per tot això els objectius d’aquesta tesi doctoral han de contribuir a establir nous criteris de disseny i operació d’aiguamolls construïts de flux subsuperficial horitzontal per tal de minimitzar la colmatació d’aquests sistemes, sense minvar l’eficiència d’eliminació de contaminants de l’aigua residual. Els objectius específics són quantificar la precisió i exactitud d’un mètode de mesura in situ de la conductivitat hidràulica, basat en el permeàmetre de càrrega variable, per a la determinació de l’estat de colmatació d’un llit així com la distribució horitzontal d’aquesta; determinar l’indicador més adecuat per avaluar la colmatació d’un aiguamoll construït de flux subsuperficial horitzontal; identificar nous paràmetres de disseny y operación susceptibles de causar o afavorir la colmatación del medi filtrant; i caracteritzar (en termes d’eliminació de contaminants i d’evolució de la colmatación) dues noves configuracions d’aiguamolls construïts a escala pilot.

  • Properties of biosolids from sludge treatment wetlands for land application

     Uggetti, Enrica; Ferrer Martí, Ivet; Llorens, Esther; Güell, David; Garcia Serrano, Joan
    Date of publication: 2010-07-01
    Book chapter

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  • Contaminant removal processes in subsurface-flow constructed wetlands: a review

     Garcia Serrano, Joan; Rousseau, Diederik P. L.; Morato Farreras, Jordi; Lesage, Els; Matamoros, Victor; Bayona, Josep M.
    Critical reviews in environmental science and technology
    Vol. 40, num. 7, p. 561-661
    DOI: 10.1080/10643380802471076
    Date of publication: 2010
    Journal article

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