The aim of this study was to assess the environmental impact of microbial fuel cells (MFCs) implemented in constructed wetlands (CWs). To this aim a life cycle assessment (LCA) was carried out comparing three scenarios: 1) a conventional CW system (without MFC implementation); 2) a CW system coupled with a gravel-based anode MFC, and 3) a CW system coupled with a graphite-based anode MFC. All systems served a population equivalent of 1500 p.e. They were designed to meet the same effluent quality. Since MFCs implemented in CWs improve treatment efficiency, the CWs coupled with MFCs had lower specific area requirement compared to the conventional CW system. The functional unit was 1 m3 of wastewater. The LCA was performed with the software SimaPro® 8, using the CML-IA baseline method. The three scenarios considered showed similar environmental performance in all the categories considered, with the exception of Abiotic Depletion Potential. In this impact category, the potential environmental impact of the CW system coupled with a gravel-based anode MFC was around 2 times higher than that generated by the conventional CW system and the CW system coupled with a graphite-based anode MFC. It was attributed to the large amount of less environmentally friendly materials (e.g. metals, graphite) for MFCs implementation, especially in the case of gravel-based anode MFCs. Therefore, the CW system coupled with graphite-based anode MFC appeared as the most environmentally friendly solution which can replace conventional CWs reducing system footprint by up to 20%. An economic assessment showed that this system was around 1.5 times more expensive than the conventional CW system.
Microbial Fuel Cells implemented in Constructed Wetlands (CW-MFCs) show limited performance. Geobacter Lovleyi has been demonstrated to be one of the predominant bacterial species in active CW-MFCs. The aim of this study was to characterize the growth of G.Lovleyi so as to identify if it could be a source for the observed CW-MFCs low performances. To this aim, G. Lovelyi was grown under three different electron donors (acetate, lactate and formate) and two electron acceptors (fumarate and Fe(III) citrate). G. Lovleyi growing and electron transfer characteristics was also studied by inoculating it in double chambered MECs (anodes poised at 31, 450 and 771 mV). Results showed that its growth was supported by acetate, with doubling times of 4.4±0.1 and 8±0.1 hours for fumarate and Fe(III) citrate as electron acceptors, respectively. G. Lovleyi was also demonstrated to be highly intolerant to oxygen, requiring cysteine as a reducing agent. In contrast, formate and lactate did not support cell growth even in the presence of cysteine. Maximum currents achieved were that of 0.08 mA and 0.26 mA for the MECs operated at 450 mV and 771 mV, respectively. However, no current was observed at 31mV. Confocal laser scanning microscopy (CLSM) analysis showed poor electrode coverage, indicating that G. Lovleyi did not attach to the electrode effectively. According to these results, low performances of CW-MFCs could by at least partially explained by the inability of G. lovleyi to oxidize the wide range of metabolites present in CW, to tolerate even trace oxygen concentrations or to efficiently attach to electrodes surface.
Clogging in HSSF CW may result in a reduction of system's life-span or treatment efficiency. Current available techniques to assess the degree of clogging in HSSF CW are time consuming and cannot be applied on a continuous basis. Main objective of this work was to assess the potential applicability of microbial fuel cells for continuous clogging assessment in HSSF CW. To this aim, two replicates of a membrane-less microbial fuel cell (MFC) were built up and operated under laboratory conditions for five weeks. The MFC anode was gravel-based to simulate the filter media of HSSF CW. MFC were weekly loaded with sludge that had been accumulating for several years in a pilot HSSF CW treating domestic wastewater. Sludge loading ranged from ca. 20 kg TS·m- 3 CW·year- 1 at the beginning of the study period up to ca. 250 kg TS·m- 3 CW·year- 1 at the end of the study period. Sludge loading applied resulted in sludge accumulated within the MFC equivalent to a clogging degree ranging from 0.2 years (ca. 0.5 kg TS·m–3CW) to ca. 5 years (ca. 10 kg TS·m–3CW). Results showed that the electric charge was negatively correlated to the amount of sludge accumulated (degree of clogging). Electron transference (expressed as electric charge) almost ceased when accumulated sludge within the MFC was equivalent to ca. 5 years of clogging (ca. 10 kg TS·m–3CW). This result suggests that, although longer study periods under more realistic conditions shall be further performed, HSSF CW operated as a MFC has great potential for clogging assessment.
The aim of this study was to quantitatively assess the net increase in microalgal biomass concentration induced by photosynthetic microbial fuel cells (PMFC). The experiment was conducted on six lab-scale PMFC constituted by an anodic chamber simulating an anaerobic digester connected to a cathodic chamber consisting of a mixed algae consortia culture. Three PMFC were operated at closed circuit (PMFC+) whereas three PMFC were left unconnected as control (PMFC-). PMFC+ produced a higher amount of carbon dioxide as a product of the organic matter oxidation that resulted in 1.5–3 times higher biomass concentration at the cathode compartment when compared to PMFC-
The cathode of microbial fuel cells (MFCs) implemented in constructed wetlands (CWs) is generally set in close contact with water surface to provide a rich oxygen environment. However, water level variations caused by plants evapotranspiration in CWs might decrease MFC performance by limiting oxygen transfer to the cathode. Main objective of this work was to quantify the effect of water level variation on MFC performance implemented in HSSF CW. For the purpose of this work two MFCs were implemented within a HSSF CW pilot plant fed with primary treated domestic wastewater. Cell voltage (E-cell) and the relative distance between the cathode and the water level were recorded for one year. Results showed that E-cell was greatly influenced by the relative distance between the cathode and the water level, giving an optimal cathode position of about 1 to 2 cm above water level. Both water level variation and E-cell were daily and seasonal dependent, showing a pronounced day/night variation during warm periods and showing almost no daily variation during cold periods. Energy production under pronounced daily water level variation was 40% lower (80 +/- 56 mWh/m(2) . day) than under low water level variation (131 +/- 61 mWh/m(2) . day). Main conclusion of the present work is that of the performance of MFC implemented in HSSF CW is highly dependent on plants evapotranspiration. Therefore, MFC that are to be implemented in CWs shall be designed to be able to cope with pronounced water level variations.
Uggetti, E.; Hughes, T.; Morris, R.; Newton, M.; Trabi, C.; Hawes, P.; Puigagut, J.; Garcia, J. Science of the total environment Vol. 559, p. 212-217 DOI: 10.1016/j.scitotenv.2016.03.195 Data de publicació: 2016-07-15 Article en revista
Forced aeration of horizontal subsurface flow constructed wetlands (HSSF CWs) is nowadays a recognized method to improve treatment efficiency, mainly in terms of ammonium removal. While numerous investigations have been reported testing constant aeration, scarce information can be found about the efficiency of intermittent aeration. This study aims at comparing continuous and intermittent aeration, establishing if there is an optimal regime that will increase treatment efficiency of HSSFCWs whilst minimizing the energy requirement. Full and intermittent aeration were tested in a pilot plant of three HSSF CWs (2.64 m(2) each) fed with primary treated wastewater. One unit was fully aerated; one intermittently aerated (i.e. by setting a limit of 0.5 mg/L dissolved oxygen within the bed) with the remaining unit not aerated as a control. Results indicated that intermittent aeration was the most successful operating method. Indeed, the coexistence of aerobic and anoxic conditions promoted by the intermittent aeration resulted in the highest COD (66%), ammonium (99%) and total nitrogen (79%) removals. On the other hand, continuous aeration promotes ammonium removal (99%), but resulted in nitrate concentrations in the effluent of up to 27 mg/L. This study demonstrates the high potential of the intermittent aeration to increase wastewater treatment efficiency of CWs providing an extreme benefit in terms of the energy consumption.
Taking into account the current global water scarcity and the expensive operation and maintenance cost of wastewater treatment, INCOVER concept has been designed to move wastewater treatment from being primarily a sanitation technology towards a bio-product recovery industry and a recycled water supplier. A wastewater specific Decision Support System methodology will be tailored to the INCOVER technologies and provide data and selection criteria for a holistic wastewater management approach.
Three added-value plants treating wastewater from three case-studies (municipalities, farms and food and beverage industries) will be implemented, assessed and optimised concurrently. INCOVER plants will be implemented at demonstration scale in order to achieve Technology Readiness Level(TRL) of 7-8 to ensure straightforward up scaling to 100,000 population equivalents (PE). INCOVER added-value plants will generate benefits from wastewater offering three recovery solutions: 1) Chemical recovery (bio-plastic and organic acids) via algae/bacteria and yeast biotechnology; 2) Near-zero-energy plant providing upgraded bio-methane via pre-treatment and anaerobic co-digestion systems; 3) Bio-production and reclaimed water via adsorption, biotechnology based on wetlands systems and hydrothermal carbonisation. To improve added-value production efficiency, INCOVER solutions will include monitoring and control via optical sensing and soft-sensors.
INCOVER solutions will reduce at least a 50% overall operation and maintenance cost of wastewater treatment through the use of wastewater as a source for energy demand and added-value production to follow UE circular economy strategy. In addition, strategies to facilitate the market uptake of INCOVER innovations will be carried out in order to close the gap between demonstration and end-users.
An estimated turnover of 188 million€ for INCOVER lead-users is expected after the initial exploitation strategy of 5 years implementing 27 INCOVER solutions.
Waste stabilization ponds (WSP), in spite of being a suitable technology for wastewater treatment, present low phosphorus removal. This study aimed at evaluating the net increase on phosphorus removal efficiency in microcosm WSP in which sludge was conditioned with an adsorbent (industrial by-product) having a high phosphorus retention capacity. In order to determine the best candidate to condition the sludge, four different industrial by-products (granular bentonite; fly ashes from a municipal solid waste incineration plant; and two types of fly ashes from power plants) were tested for their phosphorus adsorption capacity. Experimental results were fitted to Langmuir and Freundlich models. All adsorbents showed a high phosphorus adsorption capacity. Maximum phosphorous adsorption capacity estimated from Langmuir equations ranged between 34.7 and 74.0 mgP/g adsorbent, being fly ashes from a power plant and granular bentonite the adsorbents with the highest and lowest adsorption capacity, respectively. Microcosms WSP were set up and the sludge conditioned with fly ashes from a municipal solid waste incineration plant. Results showed that phosphorus removal efficiency increased up to 90% by adding 5% of adsorbent (in terms of weight of adsorbent to weight of sludge). Main conclusion is that of industrial by-products may be a low-cost solution for enhancing phosphorus removal in WSP.
This is an Accepted Manuscript of an article published by Taylor & Francis Group in Desalination and Water Treatment on 2016, available online at: http://www.tandfonline.com/10.1080/19443994.2014.977957
This work aimed at determining the amount of energy that can be harvested by implementing microbial fuel cells (MFC) in horizontal subsurface constructed wetlands (HSSF CWs) during the treatment of real domestic wastewater. To this aim, MFC were implemented in a pilot plant based on two HSSF CW, one fed with primary settled wastewater (Settler line) and the other fed with the effluent of a hydrolytic upflow sludge blanket reactor (HUSB line). The eubacterial and archaeal community was profiled on wetland gravel, MFC electrodes and primary treated wastewater by means of 16S rRNA gene-based 454-pyrosequencing and qPCR of 16S rRNA and mcrA genes. Maximum current (219 mA/m(2)) and power (36 mW/m(2)) densities were obtained for the HUSB line. Power production pattern correlated well with water level fluctuations within the wetlands, whereas the type of primary treatment implemented had a significant impact on the diversity and relative abundance of eubacteria communities colonizing MFC. It is worth noticing the high predominance (13-16% of relative abundance) of one OM belonging to Geobacter on active MFC of the HUSB line that was absent for the settler line MFC. Hence, MFC show promise for power production in constructed wetlands receiving the effluent of a HUSB reactor. (C) 2015 Elsevier Ltd. All rights reserved.
Labella, A.; Caniani, D.; Hughes, T.; Morrison, R.; Newton, M.; Hawes, P.; Puigagut, J.; Garcia, J.; Uggetti, E. Ecological engineering Vol. 83, p. 184-190 DOI: 10.1016/j.ecoleng.2015.06.028 Data de publicació: 2015-10 Article en revista
Constructed wetlands including aeration and heating were studied to improve treatment efficiency and prevent clogging. The experiments were carried out in a pilot plant (0.4 m(2)) treating urban wastewater with an organic loading rate of 40-60 g COD/m(2) d. Continuous and intermittent aeration was performed from the bottom on 8% of the wetland surface, leading to different dissolved oxygen concentrations within the wetlands (from 0.2 to 5 mg O-2/L). Continuous aeration increased organic matter (COD) and ammonium nitrogen removal by 56% and 69%, respectively. Improvements in wastewater treatment caused by aeration can result in reduction of the surface area requirement of future systems. This work demonstrated that for the studied configuration the cost of the power consumption of the continuous aeration was largely covered by the reduction of the wetlands surface. Even if the heating of 8% of the wetland surface at 21 degrees C had no effects on treatment performance, positive results showed that solids accumulation rate within the granular medium, which is closely related to the development of clogging. It has been demonstrated that heating for 10 days per year during 20 year period would delay the equivalent of 1 year of solids accumulation.
Methane is emitted in horizontal subsurface flow constructed wetlands (HSSF CWs) during wastewater treatment. The objective of this work was to determine the influence of primary treatment and organic loading rate on methane emissions from constructed wetlands. To this aim, methane emissions from a HSSF CW pilot plant were measured using the closed chamber method. The effect of primary treatment was addressed by comparing emissions from wetlands receiving the effluent of an anaerobic (HUSB reactor) or a conventional settler as primary treatments. Alternatively, the effect of organic loading was addressed by comparing emissions from wetlands operated under high organic loading (52 g COD m (2) day (1)) and low organic loading (17 g COD m (2) day (1)). Results showed that methane emission rates were affected by the type of primary treatment and, to a lesser extent, by the organic loading applied. Accordingly, lower redox conditions and slightly higher organic loading of a wetland receiving the effluent of a HUSB reactor resulted in methane emissions twelve times higher than those of the wetland fed with primary settled wastewater. Moreover, systems subjected to three times higher organic loading than that recommended lead to higher methane emission rates, although high data variability resulted in no statistically significant differences.
A microbial fuel cell (MFC) is a device that generates electricity from the
microbial degradation of organic and inorganic substrates. Constructed wetlands (CWs) are natural wastewater treatment systems that constitute a suitable technology for the sanitation of small communities. The synergy between MFCs and CWs is possible because of the presence of organic matter in CWs due to wastewater characteristics and the naturally generated redox gradient between the upper layer of CWs treatment bed (in aerobic conditions) and the deeper layers (completely anaerobic). As a result of MFC implementation in CWs (MFC-CW), it is possible not only to produce an energy surplus while wastewater is treated but also to improve and monitor the overall treatment process. Moreover, the implementation of MFCs may exert other beneficial effects on CWs, such as a decrease of surface treatment requirements, reduction of greenhouse gas
emissions or clogging. Finally, MFCs implemented in CWs would be also a suitable bioelectrochemical tool for the assessment of treatment performance without any additional cost involved in the process. Overall, though considered to be at an infancy stage, MFC-CW represents a promising synergy between technologies that may reduce energy costs and enhance treatment performance and monitoring while wastewater is treated. The envisaged main challenges for maximizing the synergy between both technologies
are linked to the optimization of both operational and design criteria in CW and MFC cell architecture and materials.
Marianna Garfi'; Pedescoll, A.; Carretero, J.; Puigagut, J.; Garcia, J. Desalination and water treatment Vol. 52, num. 31-33, p. 5848-5855 DOI: 10.1080/19443994.2013.811443 Data de publicació: 2014-09-19 Article en revista
This study aimed at determining the reliability and feasibility of constructed wetlands (CWs) performance evaluation by online monitoring. Redox potential (E-H), turbidity and ammonium (NH4) were continuously monitored for one year by means of online sensors in a pilot plant based on horizontal sub-surface flow constructed wetlands (HSSF CWs). Results were compared with conventional laboratory analyses. Online measures and laboratory analyses showed good agreement for NH4 (r = 0.84, p < 0.01). A significant correlation was also found for: online turbidity vs. Total suspended solids (TSS) (r = 0.85, p < 0.01); online turbidity vs. Biochemical oxygen demand (BOD) (r = 0.88; p < 0.01) and E-H vs. BOD (r = -0.62; p < 0.01). Results suggested that in full-scale CWs, continuous monitoring of turbidity, E-H and NH4 would help to both daily monitoring and improvement of CWs performance. A general overview about economic aspects suggested that, continuous monitoring of wastewater quality could be technically feasible and cheaper than traditional chemical-based monitoring.
The influence of tubificid worms on nutrient translocation from water to fish farm sediments accumulating in settling ponds was addressed under laboratory conditions. Small microcosms of 0.5 L were filled up with 35 g of sludge from a fish farm settling pond and 0.15 L of filtered settling pond water. The experimental set up consisted of one control line (no worms added), a second experimental line with 1 mg of tubificid worms center dot g(-1) fresh sediment (550 individuals center dot m(-2)) and a third experimental line with 40 mg of tubificid worms center dot g(-1) fresh sediment (22 000 individuals center dot m(-2)). Nutrients translocation was determined by monitoring overlaying water concentration of ammonia, nitrate and phosphate for ten days. Results showed that abundances of 550 individuals center dot m(-2) had no significant influence on the fluxes of nutrients here considered. However, the influence of higher abundances of tubificids (22 000 individuals center dot m(-2)) was of significant extent on the translocation of nitrate and phosphate. Accordingly, bioturbation of tubificids caused 55% lower nitrate uptake by the sediment when compared to control conditions. Phosphorus released by the sediments of the control condition was ca. 90% higher than that recorded under abundances of tubificids (22 000 individuals center dot m(-2)). Results obtained allowed us to estimate that fish farm settling ponds highly colonized by tubificid worms (22 000 individuals center dot m(-2)) may contribute to decrease phosphorus discharge (in terms of soluble phosphorus) in ca. 5 g of P center dot ton(-1) of fish produced.
Sediment microbial fuel cell (sMFC) represents a variation of the typical configuration of a MFC in which energy can be harvested via naturally occurring electropotential differences. Moreover, constructed wetlands show marked redox gradients along the depth which could be exploited for energy production via sMFC. In spite of the potential application of sMFC to constructed wetlands, there is almost no published work on the topic. The main objective of the present work was to define the best operational and design conditions of sub-surface flow constructed wetlands (SSF CWs) under which energy production with microbial fuel cells (MFCs) would be maximized. To this aim, a pilot plant based on SSF CW treating domestic sewage was operated during six months. Redox gradients along the depth of SSF CWs were determined as function of hydraulic regime (continuous vs discontinuous) and the presence of macrophytes in two sampling campaigns (after three and six months of plant operation). Redox potential (EH) within the wetlands was analysed at 5, 15 and 25 cm. Results obtained indicated that the maximum redox gradient was between the surface and the bottom of the bed for continuous planted wetlands (407.7 ± 73.8 mV) and, to a lesser extent, between the surface and the middle part of the wetland (356.5 ± 76.7 mV). Finally, the maximum redox gradients obtained for planted wetlands operated under continuous flow regime would lead to a power production of about 16 mW/m2.
Constructed wetlands are a popular form of waste-water treatment that have proliferated across Europe and the rest of the world in recent years as an environmentally conscious form of waste water treatment. The ability to monitor the conditions in the bed and control input factors such as heating and aeration may extend the lifetime of the reed bed substantially beyond the ten year lifetime normally reached. The Autonomous Reed Bed Installation (ARBI) project is an EU FP7 initiative to develop a reed bed with automated control over input parameters based on readings taken from embedded sensors. Automated remedial action may improve bed treatment efficiency, and prolong the life of the bed and avoiding the need to refurbish the bed, which is both time consuming and costly. One critical parameter to observe is the clog state of the reed bed, as this can severely impact on the efficiency of water treatment to the point of the bed becoming non-operable. Magnetic resonance (MR) sensors can be a powerful tool in determining clogging levels, and has previously been explored in the literature. This work is based on a conference paper (2nd International Conference "Water resources and wetlands", 2014) and details magnetic sensors suitable for long-term embedding into a constructed wetland. Unlike previous studies this work examines a probe embedded into a wetland.
Constructed wetlands are a popular form of waste-water treatment that have proliferated across Europe and the rest of the world in recent years as an environmentally conscious form of waste water treatment. The ability to monitor the conditions in the bed and control input factors such as heating and aeration may extend the lifetime of the reed bed substantially beyond the ten year lifetime normally reached. The Autonomous Reed Bed Installation (ARBI) project is an EU FP7 initiative to develop a reed bed with automated control over input parameters based on readings taken from embedded sensors. Automated remedial action may improve bed treatment efficiency, and prolong the life of the bed and avoiding the need to refurbish the bed, which is both time consuming and costly. One critical parameter to observe is the clog state of the reed bed, as this can severely impact on the efficiency of water treatment to the point of the bed becoming non-operable. Magnetic resonance (MR) sensors can be a powerful tool in determining clogging levels, and has previously been explored in the literature. This work is based on a conference paper (2nd International Conference
Non-homogeneous mixing of methane (NHM) within closed chambers was studied under laboratory conditions. The experimental set-up consisted of a PVC vented chamber of 5.3 litres of effective volume fitted with a power-adjustable 12 V fan. NHM within the chamber was studied according to fan position (top vs lateral), fan airflow strength (23 vs 80 cubic feet per minute) and the mixing time before sample withdrawal (5, 10, 15 and 20 minutes). The potential bias of methane flux densities caused by NHM was addressed by monitoring the difference between linearly expected and estimated flux densities of ca. 400, ca. 800 and ca. 1,600 mg CH4.m-2 d-1. Methane within the chamber was under non-homogeneous conditions. Accordingly, methane concentrations at the bottom of the chamber were between 20 to 70% higher than those recorded at the middle or top sections of the chamber, regardless of fan position, fan air-flow strength or time before sample withdrawal. NHM led to notable biases on flux density estimation. Accordingly, flux density estimated from top and middle sampling sections were systematically lower (ca. 50%) than those expected. Flux densities estimated from bottom samples were between 10% higher and 25% lower than expected, regardless of the flux density considered.
'Subsurface-flow constructed wetlands have become a very popular cost effective and green technology for treatment of waste water throughout Europe and the rest of the world. Original predictions over the longevity of constructed wetlands were approximately 50 -100 years (Conley et al 1991). However, it has become disappointingly apparent that these systems are clogging and have on average a lifetime of less than 10 years (Griffin et al 2008). Currently when a wetland becomes clogged, the whole site has to be refurbished and the reeds regrown, which takes several years and has significant economic consequences for the operators.
Our project ARBI aims to develop and trial an Autonomous Reed Bed Installation containing a magnetic resonance probe, can be deployed in several locations within a wetland to give measurements at different depths. By measuring the relaxation times of MR, sufficient information can be obtained to determine the clog state of the gravel bed of a wetland. This would enable the operators to isolate those areas of the bed where the problem resides and make a partial intervention, without the need to remove and re-plant the whole reed bed. When the system is developed, we will have potential for application in other water treatment systems based on subsurface flows like: slow rate sand filters, and river bank filtration.
The project will have major benefits for those organisations who would like to install reedbeds but have resisted doing because of concerns over performance and maintenance costs. These will increase the potential size of the market for reedbed installers and benefit the SMEs in the consortium who currently are operating in a constrained market which has not achieved its true potential.'
Non-homogeneous mixing of methane (NHM) within closed chambers was studied under
laboratory conditions. The experimental set up consisted of a PVC vented chamber of 5.3
litres of effective volume implemented with a power-adjustable 12V fan. NHM was addressed by injecting a known volume of methane and extracting, afterwards, gas samples from the top, middle and bottom sections of the chamber. NHM within the chamber was studied under different experimental situations such as the fan position (top vs lateral), fan airflow strength (23 vs 80 cubic feet per minute) and the mixing time before sample withdrawal (5, 10, 15 and 20 minutes). The potential bias of methane flux densities caused by NHM was addressed by monitoring the difference between linearly expected and estimated flux densities of ca. 400, ca. 800 and ca. 1600 mg CH4.m-2.d-1. Results showed that methane within the chamber was under non-homogeneous conditions. Accordingly, for mixing times before sample withdrawal ranging from 5 to 20 minutes methane concentrations at the bottom of the chamber were between 20% to 70% higher than those recorded at the middle or top sections of the chamber, regardless the fan position or fan airflow strength. Furthermore, NHM led to notable biases on flux density estimation. Accordingly, flux density estimated from top and middle sampling sections were systematically lower (ca. 50%) than those expected, regardless the flux density considered. Alternatively, flux densities estimated from bottom samples showed a lesser bias (between 10% higher to 25% lower than expected flux densities).
The objective of the present work was to determine the optimal redox gradient that can be obtained in sub-surface flow constructed wetlands (SSF CWs) to maximize the energy production with microbial fuel cells (MFCs). To this aim, a pilot plant based on SSF CW was evaluated for vertical redox profiles. Key operational and design parameters surveyed that influences redox conditions in SSF CW were the presence of plants (Phragmites australis) and the flow regime (continuous and discontinuous flow regime). Redox potential (EH) within the wetlands was analysed at a 5, 15 and 25 cm depth. Results obtained indicated that EH daily variation within the wetlands was small for depths of 5 cm and 25 cm, regardless operational or design conditions. On the contrary, the redox variation was of notable extent at 15 cm depth and ranging from +50 mV to – 300 mV, and especially pronounced for discontinuous flow planted wetlands. Overall, discontinuous flow and planted wetlands showed a higher redox potential at the bottom of the wetlands (between 50 and 100 mV higher) than those unplanted operated at a continuous flow. Furthermore, the maximum attainable redox gradient under the conditions here considered (redox difference between the
surface of the wetland and the bottom or the middle part of the bed) is between 350 and 450 mV, being the continuous flow planted wetlands the configuration that offers the best balance between the maximum redox gradient and its stability along the day. Finally, the redox gradients obtained for planted wetlands operated under continuous flow regime would lead to a power production ranging of some 40 mW/m2 of wetland.
'At a time with an urgent need to conserve water resources, efficient sanitation systems play a key role in sustainability. They can ensure that the vital resource Water is recovered from waste and can be re-used at the same time as protecting human health and the environment. The SWINGS project consortium will establish an optimal methodology for nutrient and energy recovery from wastewater (WW) at the same time as making the water safe for reuse, all in a manner conducible to rural communities in developing countries, with India as the concrete example. In particular, the SWINGS project will enlist already optimized municipal WW treatment concepts and combine 'green' and sustainable technologies. The result will be enhances water recycling and re-use, decreased energy consumption, and production of useful by-products from the process as secondary resources. Thus, treated WW will be transformed to soil enrichment resource, to irrigation water, to aquaculture farm feed, via sustainable sanitation that safeguards the local drinking water supply in India.
The starting point of the SWINGS project will be anaerobic digestion (AD) and constructed wetlands (CW) that will be configured with environmentally sustainable disinfection technologies, like water solar disinfection. Pilot plants will be designed and constructed in India that combine the treatment methods mentioned above, after which the new systems will be established in steady-state operation, and then, the AD-CW configurations optimized. Systems for disinfection of the effluent will be implemented and on-line monitoring of pathogen load attempted. Finally, life cycle assessment of several treatment configurations will be used to develop a decision support system for future selection of sustainable and efficient treatment technologies in developing countries like India. The project will publish articles and hold workshops in order to disseminate its results, especially to SMEs and to public authorities.'
'The here proposed NAwATech Europe proposal is closely interconnected with the partner project NaWaTech India. In order to reach the maximal impact the two projects have formed one common work plan for both projects, targeting the same objectives, will present their results at the same web-site and formed a joint management team. Providing adequate water supply and sanitation, particularly in urban areas, is a challenging task for governments throughout the world. This task is made even more difficult due to predicted dramatic global changes. In order to cope with water shortages in urban areas, there is a need for a paradigm shift from conventional end-of-pipe water management to an integrated approach. This integrated approach should include several actions such as: (i) interventions over the entire urban water cycle; (ii) optimisation of water use by reusing wastewater and preventing pollution of freshwater source; (iii) prioritisation of small-scale natural and technical systems, which are flexible, cost-effective and require low operation and maintenance. Natural water systems, such as manmade wetlands and sub-soil filtration and storage via soil aquifer treatment and bank filtration, are such systems. NaWaTech stands for natural water systems and treatment technologies to cope with water shortages in urbanised areas in India. The concept is based on optimised use of different urban water flows by treating each of these flows via a modular natural system taking into account the different nature and degree of pollution of the different water sources. Thus, it will cost-effectively improve the water quality of urban surface water and restore depleting groundwater sources. Due to the multi-barrier approach, these systems will also be able to treat heavily polluted water (i.e. wastewater) in order to reuse them and to supplement traditional sources to cope with water shortages today and in the future.'
The effects of design and operational factors on the dynamics of ciliated protozoa in constructed wetlands (CWs) treating wastewater remain poorly known, although bacterivory by ciliates could have important implications for nutrient cycling in these systems. We conducted a greenhouse experiment with eight wetland mesocosms (1 m2) fed with synthetic wastewater to assess how macrophyte species (Phragmites australis, Phalaris arundinacea, and Typha angustifolia), location within CW (longitudinal, depth), and temporal fluctuations affect ciliate abundance and diversity. Urosoma similis was the most abundant taxon, but Hypotrichidae, Scuticociliates, Drepomonas revoluta, and Acineria uncinata were also abundant. Longitudinal location had the highest impact on ciliate dynamics, with more abundant and diverse communities in the initial section of wetlands. P. australis/T. angustifolia and P. arundinacea had the most and least favorable conditions for ciliates, respectively, but differences among macrophytes were mostly not significant. Ciliate abundance appeared to decline from August to November, most likely because of lower temperature and plant inputs of organic matter and oxygen. Depth had no apparent impact on ciliate dynamics, suggesting that sampling at multiple depths in CW is not necessary to adequately monitor ciliate communities. Overall, our results suggest that macrophytes, location, and date of sampling influenced ciliated dynamics but stress the need for direct manipulative experiments of ciliate abundance, diversity, and composition conducted on a full annual cycle to better understand the impact of ciliates on nutrient cycling in CWs. This is especially true to determine if the associations found in our principal component
analysis are robust.
Pedescoll, A.; Knowles, P.; Davies, P.A; Garcia, J.; Puigagut, J. Water, air and soil pollution Vol. 223, num. 5, p. 2263-2275 DOI: 10.1007/s11270-011-1021-4 Data de publicació: 2012-06 Article en revista
'More than water scarcity, diseases and civil wars, Africa is also the least wealthy continent, in terms of economic and financial resources. These combined and tightly linked problems have led to a restricted range of choices, affordable for African countries, to deal particularly with the water issue, as a major topic. Polluted water treatment before use has been their almost unique solution to deal with a growing water scarcity. The treatment of water and elimination of pollutants, mainly pathogenic organisms, xenobiotics and heavy metals, although itself presents significant challenges, is crucial for human health and environmental considerations. However, most regions in developing countries cannot afford the costs of advanced and specialized systems.
Numerous water cleaning methods are based in natural, plants or micro-organisms, biochemical processes. Biotechnology is a useful tool that is delivering improved products and process for environmental sustainability, and promises a range of benefits to manage the industrial WW economically and effectively around the world. Some biotechnological techniques are quite sophisticated but others are simple, cost effective and adapted to local conditions and resources of developing countries.
These natural biological treatment systems include lagooning, land treatment, phytodepuration, or constructed wetlands systems. They can be applied as secondary or tertiary purification treatment, allowing the removal of pathogenic microorganisms and the degradation of the organic pollutants, so that waste water can be recycled for irrigation and domestic use and hence reduce the pressure on the hydric resources. Other biotechnological techniques to be taken into account within this proposal are biofiltration, membrane bioreactors and algae and other aquatic crops’ application for wastewater purification.'
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.
Premi extraordinari doctorat curs 2010-2011, àmbit de Ciències
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.
Aquacultural Engineering Society Superior Paper Award
Freshwater fish farms in Quebec are facing stringent phosphorus discharge limits of 4.2 kg P per tonne of fish produced. Most phosphorus in fish farm effluents is found in particulate form (uneaten food, feces,
etc.). Physical separation systems such as microscreens, filter beds, Cornell-type circular tanks and settling tanks have been proposed to remove solids from raceway and recirculation fish farm effluents but these
technologies are relatively expensive and labour intensive for small pond based production facilities, as mostly found in Quebec. A novel sediment retention system (SRS), consisting of a 1m3 truncated pyramid, was installed at the bottom of an earth pond, below a surface aerator. The objective of this study was to determine the feasibility of collecting and removing sediments by using the SRS and to determine its particulate phosphorus removal efficiency. Solids accumulated in the SRS were quantified and characterised weekly, for 10 weeks. Fish production, food supply, rain events and fish harvesting were also monitored over the course of the study period. The total solids (TS) accumulation rate in the SRS was, on average, 4.0 kg/d with a volatile solids fraction of 7.8% and the P accumulation rate was, on average, 12.4 g P/d. The P removal efficiency obtained with the SRS was 24% of the total P not taken up by fish (effluent P, PEFF). Assuming that 50% of the PEFF was in the particulate form, the removal efficiency of
the SRS was 47%. Lab-scale results correlated with the P mass balance calculations to show that sediments from earth ponds can play an active role in the sorption of soluble phosphorus. Approximately 30% of the P removed from the SRS was attributed to previous sorption/precipitation of soluble P into inorganic forms. The Langmuir model fitted the sorption isotherm of phosphorus onto earth pond soil and the maximum sorption constant obtained was 1.3mg P/g soil. Fish harvesting was identified as the main
external factor affecting sediments and phosphorus accumulation in the SRS. It was concluded that an SRS located under the aerator surface is a suitable and efficient strategy to collect and remove particulate
phosphorus generated from fish production in earth ponds.
Pedescoll, A.; Passos , F.; Alba, E.; Garcia, J.; Puigagut, J. IWA International Conference on Wetlands Systems for Water Pollution Control p. 1-3 Data de presentació: 2010-10-08 Presentació treball a congrés
Gagnon, V.; Maltais-Landry, G.; Puigagut, J.; Chazarenc, F.; Brisson, J. Water, air and soil pollution Vol. 212, num. 1-4, p. 483-490 DOI: 10.1007/s11270-010-0362-8 Data de publicació: 2010-10 Article en revista
Pedescoll, A.; Corzo, A.; Alvarez, E.; Puigagut, J.; Garcia, J. IWA International Conference on Wetlands Systems for Water Pollution Control p. 1-3 Data de presentació: 2010-10 Presentació treball a congrés
The aim of this study was to verify under lab conditions the reliability, repeatability and accuracy of the
falling head method (FHM) for hydraulic conductivity measurements. TheFHMis a reliable procedure that has slight variations (less than 10%) in repeated measurements and turns out to be a reliable technique to record the hydraulic conductivities typically described for clogged and unclogged subsurface-flow
constructed wetlands (from 4 to ca. 360 m/day). The accuracy of the method is acceptable considering difficulties in the measurement of hydraulic conductivity in highly conductive media. Accordingly, results
show measurement deviations of 20% when compared with a laboratory constant head method for highly conductive media (higher than 250 m/day), and 80% for media with low hydraulic conductivity (lower than 50 m/day). The main conclusion of the present paper is that of the FHM is a reliable and repeatable technique for hydraulic conductivity measurements and it is accurate enough for on-site clogging assessment in full-scale constructed wetlands.