Sludge management modeling to enhance P-recovery as struvite in wastewater treatment plants

[EN] Interest in phosphorus (P) recovery and reuse has increased in recent years as supplies of P are declining. After use, most of the P remains in wastewater, making Wastewater Treatment Plants (WWTPs) a vital part of P recycling. In this work, a new sludge management operation was studied by modeling in order to recover Pin the form of struvite and minimize operating problems due to uncontrolled P precipitation in WWTPs. During the study, intensive analytical campaigns were carried out on the water and sludge lines. The results identified the anaerobic digester as a "hot spot" of uncontrolled P precipitation (9.5 gP/kg sludge) and highlighted possible operating problems due to the accumulation of precipitates. A new sludge line management strategy was simulated therefore using DESASS (c) software, consisting of the elutriation of the mixed sludge in the mixing chamber, to reduce uncontrolled P precipitation and to obtain a P-rich stream (primary thickener supernatant) to be used in a crystallization process. The key operating parameters were found to be: the elutriation flow from the mixing chamber to the primary thickener, the digestion flow and the sludge blanket height of the primary thickener, with optimized values between 70 and 80 m(3)/d, 90-100 m(3)/d and 1.4-1.5 m, respectively. Under these operating conditions, the preliminary results showed that P concentration in the primary thickener overflow significantly increased (from 38 to 100 mg PO4-P/L), which shows that this stream is suitable for use in a subsequent crystallization reactor to recover P in the form of struvite. (C) 2017 Elsevier Ltd. All rights reserved.This work was co-financed by the European Financial Instrument for the Environment (LIFE +) as part of the PHORWater Project (LIFE12 ENV/ES/000441).Martí Ortega, N.; Barat, R.; Seco Torrecillas, A.; Pastor Alcañiz, L.; Bouzas Blanco, A. (2017). Sludge management modeling to enhance P-recovery as struvite in wastewater treatment plants. Journal of Environmental Management. 196:340-346. https://doi.org/10.1016/j.jenvman.2016.12.074S34034619

Implementation of a global P-recovery system in urban wastewater treatment plants

[EN] Current wastewater treatment plants (WWTPs) paradigm is moving towards the so-called water resource recovery facilities in which sewage is considered a source of valuable resources. In particular, urban WWTPs are crucial systems to enhance phosphorus (P) recycling. This paper evaluates the implementation of a P-recovery system in Calahorra WWTP combining the operation of a new sludge line configuration coupled to a struvite crystallisation reactor at demonstration-scale. This new configuration consisted in the elutriation in the gravity thickener of the mixed sludge contained in the mixing chamber in order to reduce the phosphate load to the anaerobic digestion. The results indicated that the P available in the primary sludge overflow was nearly five times more than the obtained for the conventional configuration (1.88 vs. 0.39 gP/kg sludge treated), and the uncontrolled P precipitation inside the anaerobic digester was reduced by 43%. Regarding the total P entering the WWTP, 19% of the total P could be recovered with the new configuration proposed in comparison with 9% in the previous conventional configuration. The average recovery efficiency in the crystallisation plant was 86.9 0.4%, yielding a struvite recovery of 8.0 +/- 0.6 kg/d (0.67 +/- 0.04 kg/m(3) fed to the crystalliser). The potential struvite production with the new configuration would be around 41 kg/d (15 t/y) crystallising the thickener supernatant which could be increased up to around 103 kg/d (38 t/y) treating all the P enriched streams (thickener supernatant and centrate streams). The paper demonstrates that WWTPs can contribute to reduce P scarcity, resulting in environmental and economic benefits. (C) 2019 Elsevier Ltd. All rights reserved.This work was co-financed by the European Financial Instrument for the Environment (LIFE +) as part of the PHORWater Project (LIFE12 ENV/ES/000441). The authors also like to acknowledge the support received from Consorcio de Aguas y Residuos de La Rioja and from EDAR del Cidacos (Calahorra).Bouzas Blanco, A.; Martí Ortega, N.; Grau, S.; Barat, R.; Mangin, D.; Pastor Alcañiz, L. (2019). Implementation of a global P-recovery system in urban wastewater treatment plants. Journal of Cleaner Production. 227:130-140. https://doi.org/10.1016/j.jclepro.2019.04.126S13014022

Ultrafiltration of residual fermentation brines from the production of table olives at different operating conditions

[EN] The membrane process of ultrafiltration (UF) has been investigated as a pretreatment previous to the further recovery and concentration of phenolic compounds from residual table olives fermentation brines. Two UF membranes were tested: a permanently hydrophilic polyethersulfone (PES) membrane with a molecular weight cut-off (MWCO) of 30 kDa and a PES membrane with a MWCO of 5 kDa. Transmembrane pressure and crossflow velocity were varied from 1 to 3 bar and from 2.2 to 3.7 m s(-1), respectively. The best membrane in terms of permeate flux and selectivity was that with MWCO of 5 kDa and the best operating conditions were transmembrane pressure of 3 bar and crossflow velocity of 2.2 m s(-1). In these conditions permeate flux was 21.6 L h(-1).m(-2), while the rejection of COD and phenolic compounds were 50.0% and 21.9%, respectively and the removal of colour and turbidity was almost complete. In addition, an alkaline cleaning protocol was proposed, which was effective to restore the initial permeability of the selected membrane. (C) 2018 Elsevier Ltd. All rights reserved.The authors of this work wish to gratefully acknowledge the financial support of CDTI (Centre for Industrial Technological Development) depending on the Spanish Ministry of Science and Innovation (INNPRONTA program, ITP-20111020).Carbonell Alcaina, C.; Alvarez Blanco, S.; Bes-Piá, M.; Mendoza Roca, JA.; Pastor Alcañiz, L. (2018). Ultrafiltration of residual fermentation brines from the production of table olives at different operating conditions. Journal of Cleaner Production. 189:662-672. https://doi.org/10.1016/j.jclepro.2018.04.127S66267218

Biological treatment of hypersaline wastewater from table olive processing: Process performance and protist population under different operating conditions

[EN] Biological treatment of fermentation brines from table olive processing (FTOP) entails many difficulties due to their very high salinity and high COD concentration, which include some phenolic compounds. These extreme conditions limit the biodiversity of the microbial population. Experiments treating FTOP were performed in laboratory sequencing batch reactors (SBR) changing operating conditions during their operation, in order to study the effects on the SBR performance and on the protist population. The statistical study showed that the SBRs with high influent COD, pH and volatile solids and low influent phenol concentration, hydraulic retention time and temperature achieved the highest COD removal efficiencies. These operational conditions also provided the highest ciliate population and the lowest flagellate presence. (C) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.The authors of this work thank the financial support of CDTI (Centro para el Desarrollo Tecnologico Industrial) depending on the Spanish Ministry of Science and Innovation. We also gratefully acknowledge Pedro Cuesta (Apoyo a la Docencia y la Investigacion. UCM) for his suggestions and help with the statistical analysis and the use of SPAD v8.0 software.Ferrer-Polonio, E.; Pérez Uz, B.; Mendoza Roca, JA.; Iborra Clar, A.; Pastor Alcañiz, L. (2017). Biological treatment of hypersaline wastewater from table olive processing: Process performance and protist population under different operating conditions. Journal of Industrial and Engineering Chemistry. 56:364-374. doi:10.1016/j.jiec.2017.07.033S3643745

Effect of alternating anaerobic and aerobic phases on the performance of a SBR treating effluents with high salinity and phenols concentration

The biological treatment of hypersaline wastewaters with high COD and phenols concentration requires long hydraulic retention times and much energy for aeration. In this work aeration time reduction in the reaction phase was studied in two sequential batch reactors (SBR) treating fermentation brine from table olive processing wastewater. To study the influence of an anaerobic phase on the SBR performance (for COD and phenolic compound removal efficiencies), different anaerobic/aerobic reaction times were evaluated. SBR-1 was operated with an anaerobic/aerobic hours ratio of 0/22, 8/14 and 14/8 and SBR-2 with a ratio of 22/0, 14/8 and 8/14. Results showed that the maximum organic matter reduction was obtained under aerobic reaction conditions (ratio 0/22) with a 82.3% and 77.9% of COD and total phenols removal, respectively. However, optimal conditions were considered to prevail for an anaerobic/aerobic ratio of 8/14, since the reactors performances were similar with lower energy consumption. Thus, 82.3% and 79.5% of COD and 77.9% and 78.3% of total phenols were removed in SBR-1 and SBR-2, respectively.The authors of this work thank the financial support of CDTI (Centre for Industrial Technological Development) depending on the Spanish Ministry of Science and InnovationFerrer-Polonio, E.; Garcia Quijano, NT.; Mendoza Roca, JA.; Iborra Clar, A.; Pastor Alcañiz, L. (2016). Effect of alternating anaerobic and aerobic phases on the performance of a SBR treating effluents with high salinity and phenols concentration. Biochemical Engineering Journal. 113:57-65. doi:10.1016/j.bej.2016.05.010S576511

Simultaneous concentration of nutrients from anaerobically digested sludge centrate and pre-treatment of industrial effluents by forward osmosis

[EN] In the last years, forward osmosis (FO) has gained increasing prominence, new membranes are being developed and new applications are being considered. In this study, the recovery of nitrogen and phosphorus of the anaerobically digested sludge centrate was studied by FO using two industrial effluents characterized by high osmotic pressure (residual stream from an absorption process for ammonia elimination and brine from a seawater desalination facility) as draw solutions. The experiments were carried out in a laboratory plant testing two FO membranes (CTA-NW and Aquaporin Inside membrane). Results showed that nitrogen concentration was achieved with both membranes and both draw solutions. The use of the effluent from ammonia absorption enhanced of the nitrogen concentration in the feed stream to the FO membrane. The reached concentration factor in the laboratory tests was 1.61 when Aquaporin membrane was used. Phosphorus could not be concentrated because of its precipitation as calcium phosphate (confirmed by EDX analysis) as a consequence of the high calcium concentration of the municipal wastewater.This study was supported by the Spanish Ministry of Economy and Competitiveness through the project RTC-2015-3582-5-AR.Soler Cabezas, JL.; Mendoza Roca, JA.; Vincent Vela, MC.; Lujan Facundo, MJ.; Pastor Alcañiz, L. (2018). Simultaneous concentration of nutrients from anaerobically digested sludge centrate and pre-treatment of industrial effluents by forward osmosis. Separation and Purification Technology. 193:289-296. https://doi.org/10.1016/j.seppur.2017.10.058S28929619

A comparative study of the influence of salt concentration on the performance of an osmotic membrane bioreactor and a sequencing batch reactor

[EN] BACKGROUNDAn osmotic membrane bioreactor (OMBR) is a wastewater treatment technique that presents low energy requirements, low membrane fouling and high removal of nutrients and organic matter. However, reverse salt flux is the main disadvantage because it causes conductivity increase in the bioreactor. This study compares the performance of a sequencing batch reactor (SBR) and an OMBR in terms of chemical oxygen demand (COD) removal, soluble microbial products (SMP) and extracellular polymeric substances (EPS) production. For that, the influent conductivity in the SBR was increased as this increases conductivity in the osmotic membrane bioreactor. RESULTSComparing the results obtained at two mixed liquor suspended solids (MLSS) concentrations in terms of membrane fouling, a concentration of 5 g L-1 of MLSS was chosen for the comparison with the SBR. The SBR achieved slightly higher COD removal efficiencies than the OMBR is spite of the accumulation of cellular debris in the membrane bioreactor. The accumulation of SMP and EPS in the OMBR was also higher than in the SBR due to the cellular debris and organic matter accumulation. In both reactors the microbial activity measured in terms of standard oxygen uptake rate decreased due to the increase of salt concentration in the bioreactor. CONCLUSIONSAs a conclusion, OMBR will be especially feasible when the draw solution is a residual stream of the same industry, like tannery wastewater or table olive processing. (c) 2017 Society of Chemical IndustryThis study was supported by the Spanish Ministry of Economy and Competitiveness through the project RTC-2015-3582-5-AR.Soler Cabezas, JL.; Lujan Facundo, MJ.; Mendoza Roca, JA.; Vincent Vela, MC.; Pastor Alcañiz, L. (2018). A comparative study of the influence of salt concentration on the performance of an osmotic membrane bioreactor and a sequencing batch reactor. Journal of Chemical Technology & Biotechnology. 93(1):72-79. https://doi.org/10.1002/jctb.5321S727993

Determination of fouling mechanisms in polymeric ultrafiltration membranes using residual brines from table olive storage wastewaters as feed

[EN] In this work, the fouling mechanisms that dominate the ultrafiltration of residual brines from table olive packing plant wastewaters were investigated. For that purpose, Hermia's models adapted to crossflow filtration, resistance-in-series model and a model combining intermediate blocking and cake formation mechanisms were fitted to the experimental data. Tests were performed with a 5 kDa polyethersulfone membrane at transmembrane pressures between 1 and 3 bar and crossflow velocities between 2.2 and 3.7 m s(-1). Results demonstrated that the resistance-in-series model was the most accurate to predict permeate flux evolution with time. The predominant fouling mechanism was cake formation followed by intermediate blocking/adsorption. The fouling resistances that were determined by means of the resistance in series model were tested using a well-established mathematical model proposed by Mondal and De that also combines both fouling phenomena (intermediate pore blocking and cake formation). Results demonstrated that the predicted resistances are consistent with those determined by Mondal and De's model. (C) 2016 Elsevier Ltd. All rights reserved.The authors of this work wish to gratefully acknowledge the financial support of CDTI (Centre for Industrial Technological Development) depending on the Spanish Ministry of Science and Innovation (INNPRONTA program, ITP-20111020).Carbonell Alcaina, C.; Corbatón Báguena, MJ.; Alvarez Blanco, S.; Bes-Piá, M.; Mendoza Roca, JA.; Pastor Alcañiz, L. (2016). Determination of fouling mechanisms in polymeric ultrafiltration membranes using residual brines from table olive storage wastewaters as feed. Journal of Food Engineering. 187:14-23. https://doi.org/10.1016/j.jfoodeng.2016.04.016S142318

Eliminación de contaminantes emergentes en aguas residuales mediante oxidación avanzada con ozono y ultrasonidos

Algunos contaminantes emergentes, principalmente fármacos de diferentes clases así como drogas de abuso, pueden estar presentes en las aguas residuales urbanas, no siendo posible su eliminación mediante las técnicas convencionales de depuración. Se ha realizado un estudio en planta piloto en dos estaciones depuradoras de aguas residuales (EDAR), Font de la Pedra (Muro de Alcoy) y Molina de Segura (Murcia), con el fin de determinar la eficacia de eliminación de ciertos contaminantes emergentes mediante un tratamiento terciario de oxidación avanzada con ozono.Removal of emerging pollutants in sewage water subjected to advanced oxidation with ozone and ultrasound Emergent pollutants, mainly pharmaceuticals from different therapeutically classes and drugs of abuse, can be presents in urban sewage water, being not effective removed through conventional sewage water treatments. The objectives of this study, conducted at a modular mobile pilot plant in two different WWTP: Font de la Pedra STP (Muro de Alcoy) and Molina de Segura STP (Murcia), were the determination and the comparison between the removal efficiency of those contaminants through the conventional sewage water treatments, and with a tertiary treatment applied consisting on Advanced oxidation processes (AOP) based on ozone treatments, and ultrasounds

Soil pollution by nonylphenol and nonylphenol ethoxylates and their effects to plants and invertebrates

Background, aim, and scope. Nonylphenol polyethoxylates (NPEOs) are a widely used class of nonionic surfactants known to be toxic and endocrine-disrupting contaminants. Their use and production have been banned in the European Union and substituted by other surfactants considered as environmentally safer. However, their use continues in many countries without any legal control. Discharges of effluents from wastewater treatment plants and the application of sewage sludge application, landfilling, and accidental spillage to soils are the major sources of NPEOs in the environment. The biodegradation of these surfactants is relatively easy, leading to the accumulation of the simplest chemical forms of nonylphenol ethoxylates (NP, NP1EO, and NP2EO) and nonylphenol carboxy acids (NP2EC or NP1EC). However, these are also the most toxic end-products and have a higher environmental persistence. Compared to aquatic ecosystems, not much is known about the effects of NPEOs in terrestrial organisms, with few studies mainly centered on the effects on plants and soil microorganisms. The main aim of this study is to provide the range of concentrations of NPEOs with ecotoxicological effects on different plants and soil invertebrate species. In addition, we aim to identify the main soil properties influencing their toxicity. Materials and methods. Two natural soils collected and OECD artificial soil were used in toxicity bioassays. Two different NPEO formulations were tested. On the one hand, a technical mixture of NPEOs containing chain isomers and oligomers with an average of eight ethoxy units was used for the experiments and is referred to herein as NP8EO. On the other hand, technical-grade 4-nonylphenol 95% purity was also used and called NP in this study. The chemicals were applied and mixed with soil as an acetone solution. The toxicity of NP8EO and NP was assessed in different taxonomical groups (plants, earthworms, enchytraeids, and collembolans) according to their respective standardized methods. The effect on lethal and sublethal endpoints was assessed and, by means of linear and non-linear regression models, the NPEO concentration causing 10% and 50% inhibition was estimated. The influence of soil properties on the toxicity was assessed using generalized linear models (GLM). Results. The chemicals tested showed contrasting toxicities, NP being clearly more toxic than NP8EO. There were also substantial differences in the sensitivity of the species and endpoints, together with clearly different toxicities in different soils. Plants were the least affected group compared to soil invertebrates, since plant endpoints were unaffected or only slightly inhibited. In soil invertebrates, reproduction was the most affected endpoint compared to growth or survival. Toxicity was the lowest in OECD artificial soil in comparison to natural soils, with a lower organic matter content. Discussion. The higher toxicity of NP, both in plant and soil invertebrate bioassays, is consistent with previously published studies and its relatively high persistence in soil. The low phytotoxicity of NP8EO and NP, unaffected at concentrations over 1 g NP kg−1, also accords with the known low uptake in plants. The effects on soil invertebrates appeared at lower concentrations than observed in plants, enchytraeids being less affected by NP8EO than earthworms and collembolans. Drastic inhibition in the invertebrate's endpoints generally appeared over 1 g kg−1 for NP8EO and below 1 g kg−1 for NP. The range of concentrations with effects is in agreement with the few similar studies published to date. Generally, the lowest toxicity values were obtained in OECD soil, with the highest organic matter content, while the highest toxicity was found in the PRA soil, with the lowest content. However, few of the models developed by GLM identified organic carbon as a significant factor in decreasing the bioavailability and toxicity of NPEO. The probable explanation for this is the simultaneous contribution of other soil properties and in particular the limited number of soils used in the bioassays. Conclusions. A low ecotoxicological risk of NPEOs might be expected for plants and soil invertebrates, since the usual concentrations in soils (below 2.6 mg kg−1) are clearly less than the lowest concentrations reported to be toxic in our study. Recommendations and perspectives. Although the apparent risk of NPEOs for soil ecosystems is limited, such risks should not be neglected since significant concentrations in soil could be reached with elevated application rates or when highly polluted sludges are used. More importantly, NPEO concentrations in soils should be maintained low given the extremely high toxicity for aquatic organisms. Despite the reduced leaching of NPEOs, runoff events might transport NP attached to soil particles and affect adjacent aquatic ecosystems