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[EN] According to previous research, it has been proved that wastewater treatment plants (WWTPs) can retain more than 90 % of the MPs contained in wastewater. However, a significant fraction of the MPs removed in WWTPs is retained in the sludge floc and this may lead to an environmental issue since biosolids can be used as fertilizers. The purpose of this research was to evaluate how the presence of polyethylene (PE) could interfere with the activated sludge performance. For this, a sequencing batch reactor (SBR) was continuously fed during 93 days with synthetic sewage and PE microbeads. It was observed that 98 +/- 2% of the total amount of MPs that entered SBR was accumulated in the activated sludge. Despite the high accumulation of MPs in the sludge, the depuration performance of the reactor was not compromised. However, the presence of MPs decreased the richness (Chao1) and abundance-based coverage estimators (ACE) and diversity (Shannon) of the bacterial community on day 93. Based on the analysis of the diversity indices and the relative abundances of microbial taxa, it was concluded that MPs had selective effects on activated sludge microbial community. However, MPs did not affect the abundance of nitrifying and denitrifying bacteria in the sludge., Authors thank the Spanish Ministry of Science, Innovation and Universities for the financial support (Reference of the project: RTI2018-096916-B-I00)

[EN] Although wastewater treatment plants can retain a high percentage of microplastics (MP) arriving at the facilities, no method for extracting and characterizing these microparticles has been still standardized in these units. This study investigated three protocols of chemical digestion, prior to analysis of microplastics, one directed to the effluents, using peroxidation, and two for activated sludge (peroxidation and Fenton). The samples (primary effluent, secondary effluent and activated sludge) were collected from a wastewater treatment plant (WWTP) located in Valencia (Spain). In addition, four common types of polymers (Low density polyethylene-LDPE, Polypropylene-PP, Polystyrene-PS and Polyethylene terephthalate-PET) were used to assess the influence of reagent exposure on microparticle integrity. Peroxidation was effective in treating the studied effluents (primary and secondary) and was also identified as the ideal protocol for activated sludge. The analysis showed that the use of H2O2 does not compromise the identification of the polymers evaluated by FTIR and also significantly reduced the concentration of suspended solids, resulting in an efficient visual separation of the microparticles. After been properly separated, the microparticles were characterized according to their size, colour and shape, and a fraction submitted to identification by mu-ATR-FTIR/ATR-FTIR. In all samples, a high presence of microfibers (MF) was observed, corresponding to more than 90% of the microparticles. However, in relation to secondary effluents, only 9% of these MF were identified as plastics, the remaining ones corresponded to cotton. The fragments found in the samples were classified as secondary in origin, and were mainly PE and PP, lower than 1 mm size., Authors thank the Spanish Ministry of Science, Innovation and Universities for the financial support (Reference of the project: RTI2018-096916-B-I00).

This work was supported by the Spanish Ministerio de Economia y Competitividad. (CTM2014-54546-P).

[EN] The performance of an osmotic membrane bioreactor (OMBR) for treating tannery wastewater at laboratory scale has been evaluated in this study. The forward osmosis (FO) membrane tested was CTA-NW from HTI. As draw solution, actual waste water from an absorption column for ammonia separation, which consists mainly of ammonium sulphate was used. The study was focused on the salt reverse flux during the OMBR operation, membrane water flux, biomass characteristics and membrane fouling. Regarding membrane water flux change with the time, the measured values diminished from 3.44 to 0.72 LMH due to the membrane fouling and the salt accumulation in the biological reactor. The stable mixed liquor conductivity value at the end of the experiment was 29.8 mS·cm¿1. The chemical oxygen demand (COD) removal efficiencies were maintained near 80% until the first 50 days of operation, considering the soluble COD in the reactor instead of the COD in the membrane permeate for the performance calculation. Thence, COD removal efficiencies decreased progressively due to the accumulation of non degradable COD coming from the tannery wastewater. Concerning to the membrane fouling, FESEM/EDX analysis corroborated that organic fouling was predominant on the membrane active layer., This study was supported by the Spanish Ministry of Economy and Competitiveness through the project RTC-2015-3582-5-AR.

[EN] Osmotic membrane bioreactor (OMBR) is an emerging membrane process which has gained interest in the recent years because of the low energy consumption and the high effluent quality. The osmotic membrane bioreactor combines a forward osmosis (FO) membrane and a biological treatment. However, salt reverse flux is the main problem because of the negative effect of the salt concentration increase in the reactor on the microbial activity. This is the reason why the study of a suitable draw solution (DS) is very important in the overall performance of the reactor. This study compares the process performance using two draw solutions: a 53 g L-1 NaCI solution and a real waste water solution (waste water from an absorption column consisting mainly of SO42- and NH4-N with concentrations of 153 g L-1 and 19 g L-1, respectively). The comparison is focused on the salt reverse flux during the reactor operation, the mixed liquor characteristics, the membrane fouling and the overall performance. The results indicated that the industrial wastewater showed a higher salt reverse flux, but also a less severe fouling and a higher the osmotic pressure difference in comparison with the NaCl solution. In terms of chemical oxygen demand (COD) removal efficiencies, both draw solutions attained values higher than 80%, though the efficiency was slightly lower when the industrial effluent was used as DS. This was related to the higher conductivity reached in the bioreactor when the industrial effluent was used as draw solution. In spite of it, the use of this industrial effluent as draw solution is strongly recommended because of the high permeate fluxes yielded, the low membrane fouling and the lack of necessity of regenerating the draw solution. (C) 2017 Elsevier B.V. All rights reserved., This study was supported by the Spanish Ministry of Economy and Competitiveness (Spain) through the project RTC-2015-3582-5-AR.

[EN] Tannery wastewater has a high environmental impact due to its low biodegradability. Sequencing batch reactors (SBRs) are an established method for treating highly polluted wastewater. To minimize the hydraulic retention time (HRT) of the SBRs, various HRT values were tested and the best value was chosen according to the removal efficiency of the soluble chemical oxygen demand (COD). A series of experiments was then carried out with two cationic polyelectrolytes added to the system in two different modes to improve the effluent quality. Both modes were evaluated in terms of the soluble COD, suspended solid concentration, and turbidity of the final effluent. The results showed that reducing the HRT to two days did not diminish the COD removal efficiencies., This work was supported by the Universitat Politecnica de Valencia (Project Ref.: PAID-06-10-2269).

Costs reduction in the activated sludge process in municipal wastewater treatment plants (MWWTPs) has nowadays become of paramount important due to the current economic situation. One of the saving measures that are being currently studied is the reduction of sludge production. In this work, the influence of the addition of chlorine dioxide to a sequencing batch reactor (SBR) on the sludge production and on the process performance has been studied. After preliminary jar-tests to select the ClO2 concentration range to be studied, two series of experiences were carried out. In the first series of experiments two laboratory SBRs were operated in parallel to test the effect of three different ClO2 doses. In the second one, three laboratory SBRs were operated in parallel to go on studying the influence of the chlorine dioxide addition on the SBRs performance and to compare two different dosing strategies (directly to the reactor and mixing the oxidant with a part of the sludge in a separated tank). SBRs treated simulated municipal wastewater and they were operated with the same operating strategy. Results showed that doses of 5 and 10 mg ClO2/gTSS entailed severe deterioration of the biological process, meanwhile the dose of 2 mg ClO2/gTSS hardly decreased the COD removal performance, implying a reduction of sludge production of 20.2%. An increase of the dose up to 2.5 mg ClO2/gTSS increased the reduction of the sludge production up to 43.4%, when the oxidant was added directly to the reactor in the anoxic reaction phase., Authors thank Fomento Agricola Castellonense S.A. (FACSA) for the support in the project.

One of the main drawbacks for the application of membranes technologies to the treatment of textile effluents is the fouling. Fouling phenomenon causes a flux decline and reduces the quality of the treated water. Previous studies have pointed at dyes that remain in the water after rinse processes, as one of the fouling agents. In this study several UF and NF membranes were tested using three synthetic reactive dyes solutions as feed streams. The influence of applied transmembrane pressure (TMP) on normalised flux, color, COD and salt retentions was studied. The extent of fouling phenomenon was evaluated in terms of filtration resistance (R s/R t ratio) and normalized flux also with TMP. The obtained results showed that R s/R t for NF and 1kDa membranes were not nearly affected by TMP, except for 10kDa one. In these cases R s/R t ratio was lower than 0.5 showing a negligible fouling phenomenon. Similar tendency was observed with the normalized flux results. For the 10kDa one, the normalized flux decreased progressively with TMP reaching a total normalized flux reduction of 60%, This work was supported by Ministerio de Asuntos Exteriores y Cooperacion of Spain (project ref: A/024821109). We also thank the technicians from the Microscope Services from UPV for their support in SEM analysis.

Textile industries are rated as the most polluting among all industrial sectors taking into account both wastewater volume and composition. In order to be able to reuse these effluents, membrane technologies have been proven as a viable alternative. However, these technologies show some drawbacks, such as the retentate stream management and the worsening of their performance due to membrane fouling. Therefore, effluents must be pre-treated in order to prevent fouling. Membrane technologies also provide some alternatives for these pre-treatments by means of the application of ceramic ultrafiltration among others. This work studies the performance of ceramic membranes by carrying out experiments with three commercial ceramic membranes with molecular weight cut-offs (MWCO) of 30, 50 and 150 kDa, respectively. Moreover, the effect of cross-flow velocity (CFV) was studied by performing the essays at different flow velocities of 3, 4 and 5 m/s. According to the obtained results, ceramic UF membranes proved to be a feasible pre-treatment alternative. Permeate flux increased as flow velocity was increased for most of the cases, owing to the fact that the cake layer formation was limited. Furthermore, flux decline along operating time was negligible for the higher flow velocities, whereas it was noticeable for the lowest flow velocity tested. For the lowest MWCO analyzed, lower cross-flow velocities were needed in order to limit the cake layer formation and reach the steady-state. This implies that, although fouling was significant for all the three molecular weight cut-off studied, it was much more noticeable when MWCO was increased. Slightly better results in terms of permeate quality were achieved as MWCO was lower. In addition, higher chemical oxygen demand (COD) and conductivity retention coefficients were obtained for the lowest cross-flow velocity. Turbidity and color removals seemed to be more influenced by water composition than CFV, with rejections higher than 99% and between 84 and 98%, respectively.

Wastewater reclamation and reuse are being widely implemented due to the lack of fresh water. When salinity is a limiting parameter to obtain the required water quality for agricultural uses, a desalination step is necessary to achieve it. Therefore, techniques such as nanofiltration (NF) or reverse osmosis (RO) can play an important role and have to be deeply studied in order to implement an economically feasible tertiary treatment. In this work, NF of a secondary effluent from a municipal wastewater treatment plant has been evaluated for increasing feed concentration in order to reach a final conversion of approximately 75%. Experiments were carried out with a laboratory plant containing a spiral wound membrane (DURASLICK-2540, General Electric) with an active area of 2.2m2. Tests were performed increasing volume concentration factors (VCFs) up to almost 4 and replicated three times to confirm the results statistically. After NF experiments an RO step of the retentate was carried out in order to concentrate the final brine. In NF experiments, for the highest VCF values, fluxes recommended for the membrane maker (17 Lm−2 h−1) were produced at a transmembrane pressure (TMP) of 3.2 bar. The TMP hardly increased with the VCF. NF membranes yielded a conductivity retention index around 42%, reaching nearly 99% for sulphate ions and only 23% for chloride ions.

Water scarcity makes industrial wastewater reuse necessary, especially in those industries characterized by both high water consumptions and extremely polluted effluents as textile industries. Membrane technologies are very efficient to treat industrial effluents for water reuse successfully, since their application entails important reductions in pollutant concentration. In the present work, a direct treatment of a textile industry effluent by means of a combination of ultrafiltration (UF) followed by a final nanofiltration (NF) stage is presented. Two different NF membranes were tested in order to compare their behaviors. For that, the influence of the feed water pH and transmembrane pressure (TMP) of the NF process were investigated. The UF results showed that the highest permeate fluxes were achieved at pH 11. Related to NF experiments, NF270 reached for the same operational conditions higher fluxes and salts rejection values than the Duraslick NF. No influence of pH was found for the permeate flux. However, the pH effect was manifest for the salts rejection. Although COD, color, and turbidity removals were high in all tests, Duraslick NF showed an average slightly better removal of COD and color. The results obtained confirm the viability of this treatment for water reuse in most of the different processes carried out in these kinds of industries.

Textile industry processes (dyeing, bleaching, printing and finishing) require a high-water consumption generating high amounts of wastewater. According to the literature, typically 200 and 500 L of water are needed to produce 1 kg of finished product [1]. This fact in combination with the current water scarcity makes necessary textile wastewater reuse. In this work, nanofiltration of biologically treated textile wastewater has been evaluated testing three nanofiltration membranes. It was studied that the influence of different volume concentration factors (VCF) on the permeate flux and salts and COD rejections. Nanofiltration experiments were carried out in a laboratory plant equipped with a pressure vessel containing one spiral wounded membrane element. The membranes tested were Ds-5 DK and DURASLICK from General Electric and Fluid System® TFC® SR®2 from KMS. For all membranes, the COD values in the permeate were negligible and flux reduction was not severe even for the maximum operating VCF (3). According to the permeate characteristics the main use of the treated water is for machinery washing processes and print implements.

Water scarcity is becoming a serious problem in the Mediterranean countries. To minimize negative effects, wastewater reclamation can be one of the possible solutions. Reverse osmosis (RO) is the process that ensures the highest water quality. Thus, the required quality goal can be reached adjusting the wastewater portion to be treated and the portion directed to the blending tank. In this work, a study with a low-pressure RO pilot plant was conducted in the laboratory. A spiral wound composite polyamide membrane (ESPA1-2540, Hydranautics) with an active area of 2.59 m2 was tested for increasing volume concentration factors (VFC). Thus, the membrane elements behaviour within a pressure vessel in a full-scale plant was simulated. The experiments were run three times to confirm statistically the results. These ones showed an almost constant permeate flux (17L m−2 h−1) while keeping the transmembrane pressure constant at 6.8 bar with a VCF of 2.5. Concerning the salt retention, it was observed a slightly reduction on increasing the VFC. However, the permeate conductivity was lower than 80 µS/cm in all cases.

One of the main environmental problems of tannery industries is due to the liquid effluents generated in their processes. It contains high amounts of organic matter, sulphates and chlorides. In fact, the wastewater stream that comes from the pickling process can reach nearly 75 mS/cm of conductivity. The present work is focused on the reclamation of pickling wastewater after applying a nanofiltration (NF) process. The retentate stream, with a high sulphates concentration, can be reused in pickling baths whereas the permeate stream, with a high chlorides concentration, can be pumped to the soaking drums. In this work a detailed study of the use of the NF permeate stream in the soaking process and its effect on the quality of the final leather is performed. At the same time, a reduction of the salt content in the final tannery effluent is accomplished. NF experiments with pickling wastewater were performed in a laboratory plant equipped with a pressure vessel that contains one spiral wound membrane element (Desal-5 DK from GE-OSMONICS) with an effective membrane area of 2.51 m 2 . The operating conditions of the experiments were a transmembrane pressure of 15 bar, 400 L h -1 of feed flow rate and a temperature of 25°C. It was studied the influence of the feed pH on the membrane performance (flux and salts rejection). The results showed that the maximum permeate flux was obtained at wastewater pH. The measured quality parameters of the final leathers soaked with NF permeates demonstrated that leathers did maintain the necessary quality for the final product.

Due to the water scarcity in Spain and in particular in the Mediterranean areas such as Valencian Region, water authorities have enhanced the wastewater reuse in the municipalities. Different treatments can be applied according to the aim of the wastewater reclamation. In this work different alternatives of tertiary treatment (conventional treatments and one treatment including ultrafiltration) were evaluated using two pilot plants (2 m 3 /h of capacity) located in the wastewater treatment plant of Quart-Benager in Valencia. Settling (with and without chemicals addition), conventional sand filtration, UV disinfection and ultrafiltration were the processes included in the different alternatives. Results showed that the most efficient conventional alternative consisting in settling + filtration + UV radiation and the treatment including ultrafiltration eliminated almost the 100% of the total coliforms. However COD removal was very much higher in the alternative including ultrafiltration (60%) in comparison with the other process combinations.

Due to the high conductivity of the global wastewater from a tannery industry, wastewater reuse is only possible if a reverse osmosis process is implemented in the wastewater treatment. The supernatant of a physical-chemical treatment is still very polluted, containing high COD values between 3000 mg/l and 4000 mg/l and conductivities of nearly 20 ms/cm. In this work, a combination of filtration, ultrafiltration and reverse osmosis is evaluated as treatment for the physical-chemically treated wastewater. Filtration was carried out using microfilters as a previous stage to ultrafiltration process. Ultrafiltration tests were performed in a laboratory plant. Organic membranes from Orelis with different cut-offs were tested to optimize the rejection and the permeate flux. Finally, the reverse osmosis step was carried out using an ESPA-1 membrane from Hydranautics. Results showed high COD values in ultrafiltration permeates (between 2000 and 3000 mg/l). A polyethersulfone membrane with cut-off of 30 kD was chosen for the pre-treatment of the reverse osmosis membrane. Permeate fluxes of the reverse osmosis membrane reached 40 l/(m 2 h) at 30 bar. Though membrane fouling was not observed during RO experiments, an industrial scale plant should pay special attention to a probable flux decrease due to the scaling if a high conversion is aimed.

Tannery industries generate wastewater containing high sulphate concentrations as sulphates are salts widely used in the tanneries as auxiliary matter. Some residual floats from tanneries (pickling, chrome tanning and dyeing) contribute to the final sulphate discharge. In order to predict NF membrane behaviour after filtering different tannery floats, a simulated wastewater was made. The effect of conductivity on the permeate flux and on chloride and sulphate retention was studied. Experiments were carried out in a laboratory plant equipped with a spiral-wound module of 2.51 m2 of active surface. Chloride retention lower than 20% was measured, and the membrane permeate fluxes were around 18 L·m−2·h−1 for feed conductivities higher than 85 mS/cm.

Physical-chemical and biological processes are the most common methods for the textile effluents treatment. However, in many occasions the pollutants removal efficiency can be increased through the combination of these conventional methods with advanced ones. In this paper, initially the ozonation influence on the coagulation-flocculation process has been studied in textile wastewater from a dyeing, printing and finishing industry. Thus, several jar-tests were carried out using wastewater before and after an ozonation process, with reaction times of 30 and 60 min. It can be highlighted that a short time preozonation enhanced the coagulation process, achieving after sedimentation COD and turbidity reductions of 57% and 95%, respectively. After that, two different NF membranes were tested using as feeding stream the wastewater after the ozone and physical-chemical stages in order to reduce the water conductivity and COD. NF experiments were carried out in a laboratory plant containing a plane module with an effective area of 120 cm2. The membranes tested were Desal DK-5 from Osmonics and NF-90 from Dow Chemical. The results showed that the COD and conductivity of the nanofiltration permeates were around 100 mg/L and 0.5 mS/cm, respectively with NF-90 membrane.

The main environmental problem of textile industries is the high water consumption for their processes. Thus it is very important to reuse wastewater, especially in areas with a water scarcity such as Comunidad Valenciana (Spain). The goal of this work is wastewater reuse combining chemical neutralization, physicochemical treatment and membranes. Neutralization studies were conducted in order to select the most appropriate neutralizing agent in terms of conductivity of the neutralized wastewater. For the physicochemical treatment four coagulants from the Cibaâ Company (Mangasol 5389, Mangasol 6348, Zetag 7103 and Alcyl 955) were compared by carrying out jar tests using different concentrations and pH values. The experimental tests were made according to the statistics program Statgraphics. After that, nanofiltration experiments of the physicochemically treated wastewater were performed in a laboratory plant equipped with a pressure vessel containing one spiral-wound membrane element (A = 2.51 m2). The operating conditions were: transmembrane pressure of 20 bar, cross-flow velocity of 1.66 m/s and a temperature of 25°C. The membrane tested was the Desal DK2540 from Osmonics. Physicochemical experiments showed that the Zetag 7130 coagulant achieved higher reductions in COD and turbidity. In addition, the sludge volume was lower than 100 mL/L. NF experiments showed that permeates, COD and conductivity were around 100 mg/L and 1000 μS/cm, respectively, with a volume concentration factor of 2.5. As a result, the combination of physicochemical treatment and nanofiltration provided treated water with good enough quality to be reused in the industry.

Tannery industries generate wastewater containing high concentrations of sulfates. In the pickling process, the presence of sulfates is due to the sulfuric acid added for pH lowering, and chromium is used as Cr 2 (SO 4 ) 3 in the tanning process. Concentrations higher than 2000 mg/L are usual in tannery wastewater, and the legal standard is 1000 mg/L beginning in 2005 in Catalonia (Spain). In this work, an evaluation of sulfate concentrations in the different residual streams of a tannery was carried out. Then, the possibilities of treating the pickling and tanning wastewaters (a part of the acidic tannery wastewaters) were studied and nanofiltration experiments using Osmonics membranes (Desal DK-2540) were carried out in a laboratory plant equipped with a spiral-wound module with 2.51 m 2 of active surface. Sulfate retention of more than 90% was achieved, and permeate quality was good enough to be reused. Finally, different alternatives to concentrate management were discussed, including its reuse in the pickling process.

Water scarcity in Mediterranean areas such as Comunidad Valenciana (Spain) makes water reuse necessary in high water-consuming industries. Previous studies by our research group showed that nanofiltration (NF) membrane permeates could be reused in some processes of finishing, dyeing and printing in the textile industry. In this work, biologically treated textile wastewaters were subjected to ozonation as a pre-treatment stage to NF. The aim was to reduce organic matter in order to prevent membranes from fouling and to oxidize organic wastewater compounds that could damage the membrane material. NF experiments were carried out in a laboratory plant equipped with a pressure vessel containing one spiral-wound membrane element (2.51 m2 of active surface). With ozonation, wastewater COD was reduced up to three different levels (160, 135 and 82 mg/L). NF experiments with wastewaters of different organic matter concentrations were carried out studying the effect of increasing the feed concentration periodically. Conductivity retentions higher than 65% were achieved, with no significant flux decay observed during the experiments.

The main goal of this work was to study the feasibility of the combination of physico-chemical treatment with nanofiltration to reuse wastewater of a printing, dyeing and finishing textile industry. For the physico-chemical treatment two coagulants (one containing Al3+ and another containing Fe2+) were compared by carrying out jar-tests using different chemical concentrations and pH values. After that, nanofltration experiments with physico-chemically treated wastewater were performed at different operating pressures and cross-flow velocities. The results showed that the COD and conductivity of the nanofiltration permeates were lower than 100 mg/L and 1000 μS/cm respectively.

This work is focused on the treatment of a textile plant wastewater. The industry mainly manufactures socks, stockings and panties, and the water is treated in order to be reused. The wastewater was characterized and jar-tests experiments were carried out with different coagulants and flocculants, at different concentrations and pH in order to obtain clarified water that can be treated by means of ultrafiltration (UF) or nanofiltration (NF). The combination of the physico-chemical treatment and the nanofiltration leads to a COD removal of almost 100%.

Ultrafiltration and nanofiltration processes were used to treat synthetic reactive dyes aqueous solutions and a raw textile effluent supplied from rinsing baths of Spanish textile industry. The influence of the reactive dyes molecular weights and the effect of the used membranes types and cut-offs were investigated with regard to the permeate flux at different transmembrane pressures (2–7 bar for UF and 4–15 bar for NF). The extent of colour retention, COD and conductivity was determined in order to monitor the membrane's separation efficiencies aiming at waste water treatment, water reuse and chemical usage minimisation. High COD retentions (80–100%) were achieved using UF and NF processes. Good conductivity rates (80%) and high COD and colour retention rates (> 90%) were obtained for both NF 200 and NF 270 membranes for all studied dyes solutions. An improvement of the rinsing wastewater quality was obtained using UF and NF processes.

This work was supported by the Spanish Ministerio de Educación y Ciencia (CTM2004-03130/TECNO).