An advanced control strategy for biological nutrient removal in continuous systems based on pH and ORP sensors

[EN] A fuzzy logic-based control system that uses low-cost sensors for controlling and optimizing the biological nitrogen removal in continuous systems has been developed. The novelty of this control system is the use of several pH, ORP, and dissolved oxygen (DO) sensors instead of on-line nitrogen sensors/analyzers. The nitrogen control system was developed and implemented in a UCT pilot plant fed with wastewater from a full-scale plant. The developed nitrification controller allows the effluent ammonium concentration to be maintained below the effluent criteria discharge with the minimum energy consumption. The denitrification process controller allows the energy consumption derived from pumping to be minimized, as the control system only increases the internal recycle flow rate when the anoxic reactor reveals further capacity for denitrification. This advanced control strategy offers an attractive alternative to on-line, nitrogen analyzer-based control systems since it involves lower investment, maintenance, and operational costs that are derived from the instrumentation. (C) 2011 Elsevier B.V. All rights reserved.The authors would like to express their gratitude to the Ministry of Science and Education for the financial support (Project reference CTM2005-06919-C03-01/TECNO). Financial support from Entitat Publica de Sanejament d'Aigues Residuals de la Comunitat Valenciana and Depuracion de Aguas del Mediterraneo is also gratefully acknowledged.Ruano, MV.; Ribes, J.; Seco Torrecillas, A.; Ferrer, J. (2012). An advanced control strategy for biological nutrient removal in continuous systems based on pH and ORP sensors. Chemical Engineering Journal. 183:212-221. https://doi.org/10.1016/j.cej.2011.12.064S21222118

An improved sampling strategy based on trajectory design for application of the Morris method to systems with many input factors

[EN] In this paper, a revised version of the Morris approach, which includes an improved sampling strategy based on trajectory design, has been adapted to the screening of the most influential parameters of a fuzzy controller applied to WWTPs. Due to the high number of parameters, a systematic approach has been proposed to apply this improved sampling strategy with low computational demand. In order to find out the proper repetition number of elementary effects of each input factor on model output (EEi) calculations, an iterative and automatic procedure has been applied. The results show that the sampling strategy has a significant effect on the parameter significance ranking and that random sampling could lead to a non-proper coverage of the parameter space. (C) 2012 Elsevier Ltd. All rights reserved.This research study has been supported by the Spanish Research Foundation (CICYT Project reference CTM2005-06919-C03-01/TECNO), which is gratefully acknowledged.Ruano García, MV.; Ribes, J.; Seco Torrecillas, A.; Ferrer, J. (2012). An improved sampling strategy based on trajectory design for application of the Morris method to systems with many input factors. Environmental Modelling & Software. 37:103-109. https://doi.org/10.1016/j.envsoft.2012.03.008S1031093

Modeling light and temperature influence on ammonium removal by Scenedesmus sp. under outdoor conditions

[EN] The ammonium removal rate of the microalga Scenedesmus sp. was studied under outdoor conditions. Microalgae were grown in a 500 L flat-plate photobioreactor and fed with the effluent of a submerged anaerobic membrane bioreactor. Temperature ranged between 9.5 WC and 32.5 WC and maximum light intensity was 1,860 μmol·m2·s1. A maximum specific ammonium removal rate of 3.71 mg NH4 þ-N·g TSS1·h1 was measured (at 22.6 WC and with a light intensity of 1,734 μmol·m2·s1). A mathematical model considering the influence of ammonium concentration, light and temperature was validated. The model successfully reproduced the observed values of ammonium removal rate obtained and it is thus presented as a useful tool for plant operation.This research work has been supported by the Spanish Ministry of Education, Culture and Sports (CTM2011-28595-C02-01/02) jointly with the European Regional Development Fund (ERDF) and Generalitat Valenciana (ACOMP2013/203), which are gratefully acknowledged. This research was also supported by the Spanish Ministry of Education, Culture and Sport via a pre-doctoral FPU fellowship to the first author (AP2009-4903). The authors also gratefully acknowledge the support from the water management entities of the Generalitat Valenciana (EPSAR).Ruiz Martinez, A.; Serralta Sevilla, J.; Seco Torrecillas, A.; Ferrer, J. (2016). Modeling light and temperature influence on ammonium removal by Scenedesmus sp. under outdoor conditions. Water Science & Technology. 74(8):1964-1970. https://doi.org/10.2166/wst.2016.383S19641970748Åkerström, A. M., Mortensen, L. M., Rusten, B., & Gislerød, H. R. (2014). Biomass production and nutrient removal by Chlorella sp. as affected by sludge liquor concentration. Journal of Environmental Management, 144, 118-124. doi:10.1016/j.jenvman.2014.05.015Bernard, O., & Rémond, B. (2012). Validation of a simple model accounting for light and temperature effect on microalgal growth. Bioresource Technology, 123, 520-527. doi:10.1016/j.biortech.2012.07.022Brennan, L., & Owende, P. (2010). Biofuels from microalgae—A review of technologies for production, processing, and extractions of biofuels and co-products. Renewable and Sustainable Energy Reviews, 14(2), 557-577. doi:10.1016/j.rser.2009.10.009Broekhuizen, N., Park, J. B. K., McBride, G. B., & Craggs, R. J. (2012). Modification, calibration and verification of the IWA River Water Quality Model to simulate a pilot-scale high rate algal pond. Water Research, 46(9), 2911-2926. doi:10.1016/j.watres.2012.03.011Giménez, J. B., Robles, A., Carretero, L., Durán, F., Ruano, M. V., Gatti, M. N., … Seco, A. (2011). Experimental study of the anaerobic urban wastewater treatment in a submerged hollow-fibre membrane bioreactor at pilot scale. Bioresource Technology, 102(19), 8799-8806. doi:10.1016/j.biortech.2011.07.014Kurano, N., & Miyachi, S. (2005). Selection of microalgal growth model for describing specific growth rate-light response using extended information criterion. Journal of Bioscience and Bioengineering, 100(4), 403-408. doi:10.1263/jbb.100.403McGinn, P. J., Dickinson, K. E., Park, K. C., Whitney, C. G., MacQuarrie, S. P., Black, F. J., … O’Leary, S. J. B. (2012). Assessment of the bioenergy and bioremediation potentials of the microalga Scenedesmus sp. AMDD cultivated in municipal wastewater effluent in batch and continuous mode. Algal Research, 1(2), 155-165. doi:10.1016/j.algal.2012.05.001Reynolds, C. S. (2006). The Ecology of Phytoplankton. doi:10.1017/cbo9780511542145Rouzic, B. L., & Bertru, G. (1997). Phytoplankton community growth in enrichment bioassays: Possible role of the nutrient intracellular pools. Acta Oecologica, 18(2), 121-133. doi:10.1016/s1146-609x(97)80069-0Ruiz-Martinez, A., Serralta, J., Pachés, M., Seco, A., & Ferrer, J. (2014). Mixed microalgae culture for ammonium removal in the absence of phosphorus: Effect of phosphorus supplementation and process modeling. Process Biochemistry, 49(12), 2249-2257. doi:10.1016/j.procbio.2014.09.002Ruiz-Martínez, A., Serralta, J., Romero, I., Seco, A., & Ferrer, J. (2015). Effect of intracellular P content on phosphate removal in Scenedesmus sp. Experimental study and kinetic expression. Bioresource Technology, 175, 325-332. doi:10.1016/j.biortech.2014.10.081Ruiz-Martínez, A., Serralta, J., Seco, A., & Ferrer, J. (2015). Effect of temperature on ammonium removal in Scenedesmus sp. Bioresource Technology, 191, 346-349. doi:10.1016/j.biortech.2015.05.070Singh, G., & Thomas, P. B. (2012). Nutrient removal from membrane bioreactor permeate using microalgae and in a microalgae membrane photoreactor. Bioresource Technology, 117, 80-85. doi:10.1016/j.biortech.2012.03.125Wang, B., & Lan, C. Q. (2011). Biomass production and nitrogen and phosphorus removal by the green alga Neochloris oleoabundans in simulated wastewater and secondary municipal wastewater effluent. Bioresource Technology, 102(10), 5639-5644. doi:10.1016/j.biortech.2011.02.054Wang, L., Min, M., Li, Y., Chen, P., Chen, Y., Liu, Y., … Ruan, R. (2009). Cultivation of Green Algae Chlorella sp. in Different Wastewaters from Municipal Wastewater Treatment Plant. Applied Biochemistry and Biotechnology, 162(4), 1174-1186. doi:10.1007/s12010-009-8866-7Wu, Y.-H., Li, X., Yu, Y., Hu, H.-Y., Zhang, T.-Y., & Li, F.-M. (2013). An integrated microalgal growth model and its application to optimize the biomass production of Scenedesmus sp. LX1 in open pond under the nutrient level of domestic secondary effluent. Bioresource Technology, 144, 445-451. doi:10.1016/j.biortech.2013.06.065Wu, Y.-H., Hu, H.-Y., Yu, Y., Zhang, T.-Y., Zhu, S.-F., Zhuang, L.-L., … Lu, Y. (2014). Microalgal species for sustainable biomass/lipid production using wastewater as resource: A review. Renewable and Sustainable Energy Reviews, 33, 675-688. doi:10.1016/j.rser.2014.02.026Xin, L., Hong-ying, H., & Yu-ping, Z. (2011). Growth and lipid accumulation properties of a freshwater microalga Scenedesmus sp. under different cultivation temperature. Bioresource Technology, 102(3), 3098-3102. doi:10.1016/j.biortech.2010.10.05

Fate of endocrine disruptor compounds in an anaerobic membrane bioreactor (AnMBR) coupled to an activated sludge reactor

[EN] The occurrence and fate of three groups of micropollutants - alkylphenols, pentachlorophenol and hormones - were studied in a pilot plant consisting of an anaerobic membrane bioreactor (AnMBR) coupled to an activated sludge reactor (University of Cape Town configuration - UCT). Under anaerobic conditions, the octylphenol and technical-nonylphenol soluble concentrations increased producing negative degradation ratios (i.e., -175 and -118%, respectively). However, high 4-n-nonylphenol and bisphenol-A degradation ratios (92 and 59% for 4-n-nonylphenol and bisphenol-A, respectively) as well as complete pentachlorophenol, estrone, 17 beta-estradiol and 17 alpha-ethinylestradiol removal were observed. Under aerobic conditions (UCT), octylphenol, technical-nonylphenol, 4-n-nonylphenol and bisphenol-A degradation ratios were higher than 84%. The AnMBR thus removes a high proportion of 4-n-nonylphenol, pentachlorophenol, estrone, 17 beta-estradiol and 17 alpha-ethinylestradiol, but requires a later post-treatment process (such as UCT) to improve bisphenol-A, octylphenol and technical-nonylphenol degradation ratios. The overall AnMBR-UCT degradation ratios were 48% and 70% for octylphenol and technical-nonylphenol, respectively, and higher than 97% for 4-n-nonylphenol and bisphenol-A. The AnMBR produced a higher micropollutant accumulation in the sludge than the UCT: removal by adsorption in the AnMBR process was between 0.5 and 10%, and less than 0.5% in the UCT process. The combination of AnMBR and UCT technologies produces an effluent stream with low concentrations of micropollutants.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO, CTM2011-28595-C02-01 and CTM2011-28595-C02-02) and the European Regional Development Fund (ERDF).Abargues Llamas, MR.; Ferrer, J.; Bouzas Blanco, A.; Seco Torrecillas, A. (2018). Fate of endocrine disruptor compounds in an anaerobic membrane bioreactor (AnMBR) coupled to an activated sludge reactor. Environmental Science: Water Research & Technology (Online). 4(2):226-233. https://doi.org/10.1039/c7ew00382jS2262334

Characterization of activated sludge settling properties with a sludge collapse-acceleration stage

[EN] The sedimentability of the activated sludge can be affected by the presence of a large variety of coagulants and polymers from a previous physical-chemical process. In this paper, the activated sludge settling process in industrial wastewater treatment plants where the sludge does not settle in a conventional way is studied. The two observed constant hindered settling velocity stages and the instant the intermediate sludge acceleration period occurs are described. A variation of the Richardson and Zaki model is used to characterize the two stages of constant settling velocity. The concentration of suspended solids, where a sudden decrease of hindered settling velocity was observed, is calculated. Finally, a new hypothesis to explain the processes triggering the collapse of the initial homogeneous sludge structure and the existence of an acceleration period is formulated.Asensi Dasí, EJ.; Alemany Martínez, E.; Seco Torrecillas, A.; Ferrer, J. (2019). Characterization of activated sludge settling properties with a sludge collapse-acceleration stage. Separation and Purification Technology. 209:32-41. https://doi.org/10.1016/j.seppur.2018.07.006S324120

Micropollutants removal in an anaerobic membrane bioreactor and in an aerobic conventional treatment plant

The paper expresses an attempt to tackle the problem due to the presence of micropollutants in wastewater which may be able to disrupt the endocrine system of some organisms. These kinds of compounds are ubiquitously present in municipal wastewater treatment plant (WWTP) effluents. The aim of this paper is to compare the fate of the alkylphenols-APs (4-(tert-octyl)) phenol, t-nonylphenol and 4-p-nonylphenol and the hormones (estrone, 17ß-estradiol and 17¿-ethinylestradiol) in a submerged anaerobic membrane bioreactor (SAMBR) pilot plant and in a conventional activated sludge wastewater treatment plant (CTP). The obtained results are also compared with the results obtained in a previous study carried out in an aerobic MBR pilot plant. The results showed that the APs soluble concentrations in the SAMBR effluent were always significantly higher than the CTP ones. Moreover, the analyses of the suspended fraction revealed that the AP concentrations in the SAMBR reactor were usually higher than in the CTP reactor, indicating that under anaerobic conditions the APs were accumulated in the digested sludge. The aerobic conditions maintained both in the CTP system and in the aerobic MBR favoured the APs and hormones degradation, and gave rise to lower concentrations in the effluent and in the reactor of these systems. Furthermore, the results also indicated that the degradation of APs under aerobic conditions was enhanced working at high solid retention time (SRT) and hydraulic retention time (HRT) values. © IWA Publishing 2012.This research was financially supported by the Government of the Region of Valencia (Generalitat Valenciana), within the research project 'Application of Water Framework Directive 2000/60/EC on endocrine disruptors and priority substances in coastal areas in the Comunidad Valenciana' and by the Spanish Research Foundation (MICINN, project CTM2008-060809-C02-01/TECNO), within the research project 'Feasibility of the SAMBR technology to treat urban wastewater, and the technical and economic feasibility to industrial implementation'.Agargues Llamas, MR.; Robles Martínez, Á.; Bouzas Blanco, A.; Seco Torrecillas, A. (2012). Micropollutants removal in an anaerobic membrane bioreactor and in an aerobic conventional treatment plant. Water Science and Technology. 65(12):2242-2250. doi:10.2166/wst.2012.145S22422250651

Use of rumen microorganisms to boost the anaerobic biodegradability of microalgae

[EN] A laboratory bioreactor using rumen microorganisms to treat Scenedesmus spp. biomass was operated for 190 days. At first the bioreactor operated as a Rumen-like Fermenter (RF) with a Sludge Retention Time (SRT) of 7 days. The RF was subsequently transformed into an anaerobic digestion system including two configurations: continuously-stirred tank reactor and anaerobic membrane bioreactor in which different SRT values of up to 100 days were assessed. Methane production peaked at 214 mL CH4 g−1 CODIn with a SRT of 100 days. COD removal and BDP peaked at above 70% and 60%, respectively, at the highest SRT, with no pre-treatment prior to microalgae digestion. The waste sludge production dropped to 0.133 mg VSS mg−1 CODIn after a SRT of 100 days.This work was funded by the Spanish Ministry of Economy and Competitiveness with the support from the European Commission through the European Regional Development Funds (MINECO, CTM2011-28595-C02-01 and CTM2011-28595-C02-02), which are gratefully acknowledged. The authors would also express their gratitude to the Education, Invetigation, Culture and Sports Council from the Valencian Generality for the Post-Doctoral fellowship awarded to Juan Bautista Gimenez Garcia (APOSTD/2016/104). The authors are thankful to Ion Perez Baena (Universitat Politecnica de Valencia, Institut de Ciencia i Tecnologia Animal) for kindly providing the ruminal fluid used in this study.Gimenez, JB.; Aguado García, D.; Bouzas, A.; Ferrer, J.; Seco Torrecillas, A. (2017). Use of rumen microorganisms to boost the anaerobic biodegradability of microalgae. Algal Research. 24:309-316. https://doi.org/10.1016/j.algal.2017.04.0033093162

P-recovery in a pilot-scale struvite crystallisation reactor for source separated urine systems using seawater and magnesium chloride as magnesium sources

[EN] Practical recovery of a non-renewable nutrient, such as phosphorus (P), is essential to support modern agriculture in the near future. The high P content of urine, makes it an attractive source for practicing the recovery of this crucial nutrient. This paper presents the experimental results at pilot-plant scale of struvite crystallisation from a source-separated urine stream using two different magnesium sources, namely magnesium chloride and seawater. The latter was chosen as sustainable option to perform P-recovery in coastal areas. Real seawater was used to assess in a more realistic way its efficiency to precipitate P as struvite, since its composition (with noticeable concentration of ions such as Ca2+, SO42¿, Na+, ¿) could lead to the formation of impurities and other precipitates. 0.99¿g of struvite was obtained per litre of urine irrespective of the operational conditions tested. In all tested conditions, precipitation efficiencies exceeded 90% and recovery efficiencies were higher than 87%, with an average struvite crystal size higher than 110¿¿m (and up to 320¿¿m, depending on the experimental conditions) in the harvested struvite samples. Almost pure struvite was obtained when MgCl2 was used as precipitant, while amorphous calcium phosphate and other impurities appeared in the precipitates using seawater as magnesium source. However, the lower settling velocity of the amorphous precipitates in comparison with the struvite precipitates suggests that their separation at industrial scale could be relatively straightforward.This research work was possible thanks to FCC Aqualia participation in INNPRONTA 2011 IISIS IPT-20111023 project (partially funded by The Centre for Industrial Technological Development (CDTI) and supported by the Spanish Ministry of Economy and Competitiveness).Aguado García, D.; Barat, R.; Bouzas Blanco, A.; Seco Torrecillas, A.; Ferrer, J. (2019). P-recovery in a pilot-scale struvite crystallisation reactor for source separated urine systems using seawater and magnesium chloride as magnesium sources. The Science of The Total Environment. 672:88-96. https://doi.org/10.1016/j.scitotenv.2019.03.485S889667

Effect of intracellular P content on phosphate removal in Scenedesmus sp. Experimental study and kinetic expression

The present work determines the effect of phosphorus content on phosphate uptake rate in a mixed culture of Chlorophyceae in which the genus Scenedesmus dominates. Phosphate uptake rate was determined in eighteen laboratory batch experiments, with samples taken from a progressively more P-starved culture in which a minimum P content of 0.11% (w/w) was achieved. The results obtained showed that the higher the internal biomass P content, the lower the phosphate removal rate. The highest specific phosphate removal rate was 6.5 mgPO4 P gTSS -1 h -1 . Microalgae with a P content around 1% (w/w) attained 10% of this highest removal rate, whereas those with a P content of 0.6% (w/w) presented 50% of the maximum removal rate. Different kinetic expressions were used to reproduce the experimental data. Best simulation results for the phosphate uptake process were obtained combining Steele equation and Hill function to represent the effect of light and intracellular phosphorus content, respectively.This research work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO, CTM2011-28595-C02-01/02) jointly with the European Regional Development Fund (ERDF) which are gratefully acknowledged.Ruiz Martínez, A.; Serralta Sevilla, J.; Romero Gil, I.; Seco Torrecillas, A.; Ferrer, J. (2015). Effect of intracellular P content on phosphate removal in Scenedesmus sp. Experimental study and kinetic expression. Bioresource Technology. 175:325-332. https://doi.org/10.1016/j.biortech.2014.10.08132533217