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Campos, J. L., Crutchik, D., Franchi, O., Pavissich, J. P., Belmonte, M., Pedrouso, A., et al. (2019). Nitrogen and Phosphorus Recovery From Anaerobically Pretreated Agro-Food Wastes: A Review. Front. Sustain. Food Syst., 2, 11 pp.
Abstract: Anaerobic digestion (AD) is commonly used for the stabilization of agro-food wastes and recovery of energy as methane. Since AD removes organic C but not nutrients (N and P), additional processes to remove them are usually applied to meet the stringent effluent criteria. However, in the past years, there was a shift from the removal to the recovery of nutrients as a result of increasing concerns regarding limited natural resources and the importance given to the sustainable treatment technologies. Recovering N and P from anaerobically pretreated agro-food wastes as easily transportable and marketable products has gained increasing importance to meet both regulatory requirements and increase revenue. For this reason, this review paper gives a critical comparison of the available and emerging technologies for N and P recovery from AD residues.
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Campos, J. L., Dumais, J., Pavissich, J. P., Franchi, O., Crutchik, D., Belmonte, M., et al. (2019). Predicting Accumulation of Intermediate Compounds in Nitrification and Autotrophic Denitrification Processes: A Chemical Approach. Biomed Res. Int., 2019, 9 pp.
Abstract: Nitrification and sulfur-based autotrophic denitrification processes can be used to remove ammonia from wastewater in an economical way. However, under certain operational conditions, these processes accumulate intermediate compounds, such as elemental sulphur, nitrite, and nitrous oxide, that are noxious for the environment. In order to predict the generation of these compounds, an analysis based on the Gibbs free energy of the possible reactions and on the oxidative capacity of the bulk liquid was done on case study systems. Results indicate that the Gibbs free energy is not a useful parameter to predict the generation of intermediate products in nitrification and autotrophic denitrification processes. Nevertheless, we show that the specific productions of nitrous oxide during nitrification, and of elemental sulphur and nitrite during autotrophic denitrification, are well related to the oxidative capacity of the bulk liquid.
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Crutchik, D., & Campos, J. L. (2021). Municipal Wastewater Reuse: Is it a Competitive Alternative to Seawater Desalination? Sustainability, 13(12), 6815.
Abstract: Water scarcity is becoming a global challenge to attempts to narrow the water demand-supply gap. To overcome this problem, it is sensible to consider alternative technologies that can exploit non-conventional water resources. The choice of such technologies should be, however, carefully analyzed, because any choice might be unfeasible from an economic point of view. In this work, a methodology to select the most appropriate non-conventional water resource, out of municipal wastewater and seawater, was proposed. Specifically, we attempted to determine which alternative provides cheaper water supply and production costs for domestic uses, depending on the wastewater treatment system used and the water plant capacity. The production of water under three scenarios was analyzed: (i) a city that has a conventional wastewater treatment plant (WWTP); (ii) a city that uses primary treatment and submarine outfalls to treat municipal wastewater; (iii) seawater desalination. The proposed methodology was tested in Chilean cities that are located in areas where water is a scarce resource. The results showed that the reuse of municipal wastewater represents a cost-competitive alternative to seawater desalination, mainly when municipal wastewater is treated in a conventional WWTP and when water flow demand is higher than 1500 m(3)/d. In contrast, seawater desalination becomes more profitable than wastewater reuse when the treatment of municipal wastewater is based on the use of submarine outfalls. This study provides a useful economic tool for promoting municipal wastewater reuse as a non-conventional water source for supplying water to cities that suffer from water scarcity in Chile and in similar areas of the world.
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Crutchik, D., Franchi, O., Caminos, L., Jeison, D., Belmonte, M., Pedrouso, A., et al. (2020). Polyhydroxyalkanoates (PHAs) Production: A Feasible Economic Option for the Treatment of Sewage Sludge in Municipal Wastewater Treatment Plants? Water, 12(4), 12 pp.
Abstract: Sludge is a by-product of municipal wastewater treatment plants (WWTPs) and its management contributes significantly to the operating costs. Large WWTPs usually have anaerobic sludge digesters to valorize sludge as methane and to reduce its mass. However, the low methane market price opens the possibility for generating other high value-added products from the organic matter in sludge, such as polyhydroxyalkanoates (PHAs). In this work, the economic feasibility of retrofitting two types of WWTPs to convert them into biofactories of crude PHAs was studied. Two cases were analyzed: (a) a large WWTP with anaerobic sludge digestion; and (b) a small WWTP where sludge is only dewatered. In a two-stage PHA-production system (biomass enrichment plus PHAs accumulation), the minimum PHAs cost would be 1.26 and 2.26 US$/kg PHA-crude for the large and small WWTPs, respectively. In a single-stage process, where a fraction of the secondary sludge (25%) is directly used to accumulate PHAs, the production costs would decrease by around 15.9% (small WWTPs) and 19.0% (large WWTPs), since capital costs associated with bioreactors decrease. Sensitivity analysis showed that the PHA/COD (Chemical Oxygen Demand) yield is the most crucial parameter affecting the production costs. The energy, methane, and sludge management prices also have an essential effect on the production costs, and their effect depends on the WWTP's size.
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Crutchik, D., Frison, N., Eusebi, A. L., & Fatone, F. (2018). Biorefinery of cellulosic primary sludge towards targeted Short Chain Fatty Acids, phosphorus and methane recovery. Water Res., 136, 112–119.
Abstract: Cellulose from used toilet paper is a major untapped resource embedded in municipal wastewater which recovery and valorization to valuable products can be optimized. Cellulosic primary sludge (CPS) can be separated by upstream dynamic sieving and anaerobically digested to recover methane as much as 4.02 m(3)/capita.year. On the other hand, optimal acidogenic fermenting conditions of CPS allows the production of targeted short-chain fatty acids (SCFAs) as much as 2.92 kg COD/capita . year. Here propionate content can be more than 30% and can optimize the enhanced biological phosphorus removal (EBPR) processes or the higher valuable co-polymer of polyhydroxyalkanoates (PHAs). In this work, first a full set of batch assays were used at three different temperatures (37, 55 and 70 degrees C) and three different initial pH (8, 9 and 10) to identify the best conditions for optimizing both the total SCFAs and propionate content from CPS fermentation. Then, the optimal conditions were applied in long term to a Sequencing Batch Fermentation Reactor where the highest propionate production (100-120 mg COD/g TVSfed.d) was obtained at 37 degrees C and adjusting the feeding pH at 8. This was attributed to the higher hydrolysis efficiency of the cellulosic materials (up to 44%), which increased the selective growth of Propionibacterium acidopropionici in the fermentation broth up to 34%. At the same time, around 88% of the phosphorus released during the acidogenic fermentation was recovered as much as 0.15 kg of struvite per capita . year. Finally, the potential market value was preliminary estimated for the recovered materials that can triple over the conventional scenario of biogas recovery in existing municipal wastewater treatment plants. (C) 2018 Elsevier Ltd. All rights reserved.
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Crutchik, D., Morales, N., Vazquez-Padin, J. R., & Garrido, J. M. (2017). Enhancement of struvite pellets crystallization in a fullscale plant using an industrial grade magnesium product. Water Sci. Technol., 75(3), 609–618.
Abstract: A full-scale struvite crystallization system was operated for the treatment of the centrate obtained from the sludge anaerobic digester in a municipal wastewater treatment plant. Additionally, the feasibility of an industrial grade Mg(OH) (2) as a cheap magnesium and alkali source was also investigated. The struvite crystallization plant was operated for two different periods: period I, in which an influent with low phosphate concentration (34.0 mg P . L (-1)) was fed to the crystallization plant; and period II, in which an influent with higher phosphate concentration (68.0 mg P . L (-1)) was used. A high efficiency of phosphorus recovery by struvite crystallization was obtained, even when the effluent treated had a high level of alkalinity. Phosphorus recovery percentage was around 77%, with a phosphate concentration in the effluent between 10.0 and 30.0 mg P .L- 1. The experiments gained struvite pellets of 0.5- 5.0 mm size. Moreover, the consumption of Mg(OH) (2) was estimated at 1.5 mol Mg added . mol P recovered (-1). Thus, industrial grade Mg(OH) (2) can be an economical alternative as magnesium and alkali sources for struvite crystallization at industrial scale.
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Crutchik, D., Rodrigues, S., Ruddle, D., & Garrido, J. M. (2018). Evaluation of a low-cost magnesium product for phosphorus recovery by struvite crystallization. J. Chem. Technol. Biotechnol., 93(4), 1012–1021.
Abstract: BACKGROUND: The development of a cost-effective process of struvite crystallization requires the selection of appropriate sources of alkali and magnesium. In this study, the effectiveness of two industrial grade products, MgO and Mg(OH)(2), as magnesium and alkali sources to recover phosphorus as struvite were investigated and compared in a first set of experiments. Subsequently, the use of industrial Mg(OH)(2) was compared in two different struvite crystallization systems, an upflow fluidized bed reactor (FBR) and a continuous stirred tank reactor (CSTR) coupled to a settler tank. RESULTS: At the same operational conditions, the consumption of MgO was higher than Mg(OH)(2) consumption. Moreover, industrial Mg(OH)(2) consumption for FBR and the CSTR operation was 1.6 and 1.1 1 mol Mg added mol(-1) P precipitated, respectively. This difference was caused by the high mixing intensity and the higher contact time between the Mg(OH)(2) slurry and the influent in the CSTR, favouring the conversion. CONCLUSIONS: Both industrial grade magnesium products are promising options for struvite crystallization. However, Mg(OH)(2) was more effective than the starting material, MgO, to recover phosphorus. Struvite crystallization by adding an industrial grade Mg(OH)(2) could be economically viable with regard to alternative physico-chemical P removal processes using metal salts, increasing the attractiveness of this P recovery process. (C) 2017 Society of Chemical Industry.
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Crutchik, D., Rodriguez-Valdecantos, G., Bustos, G., Bravo, J., Gonzalez, B., & Pabon-Pereira, C. (2020). Vermiproductivity, maturation and microbiological changes derived from the use of liquid anaerobic digestate during the vermicomposting of market waste. Water Sci. Technol., 82(9), 1781–1794.
Abstract: Recently, it has been suggested that the liquid fraction of anaerobic digestate, derived from the treatment of wastewater and solid wastes, could be used in vermicomposting as a solution to its disposal, and even for its valorization. Nevertheless, the literature does not provide enough information about its impact on the process of vermicomposting itself and on the final quality of the end-product. In this study, the effect of different doses of digestate in the vermicomposting process treating market waste is assessed measuring earthworm population dynamics, the bacterial community succession present in the vermibeds, as well as maturation and the end-quality of the vermicompost. Our results show that the addition of liquid digestate to the vermibeds increased the earthworms biomass, i.e. 71%, 94% and 168% in control, and vermibeds with 30% and 60% digestate, respectively. Further, the increase in the amount of N in the vermicompost decreased as the digestate addition increased, i.e. 75%, 8%, 3%. The maturity achieved was high in all treatments as shown by the C/N ratio, 7.98, 7.40 and 10.20, and the high seed germination rate, above 90%. Finally, the succession of the microbial community was not disturbed and compositional stabilization was reached after 92 days.
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Crutchik, D., Rodriguez-Valdecantos, G., Bustos, G., Bravo, J., Gonzalez, B., & Pabon-Pereira, C. (2020). WATER SCIENCE AND TECHNOLOGY. Water Sci. Technol., 82(9), 1781–1794.
Abstract: Recently, it has been suggested that the liquid fraction of anaerobic digestate, derived from the treatment of wastewater and solid wastes, could be used in vermicomposting as a solution to its disposal, and even for its valorization. Nevertheless, the literature does not provide enough information about its impact on the process of vermicomposting itself and on the final quality of the end-product. In this study, the effect of different doses of digestate in the vermicomposting process treating market waste is assessed measuring earthworm population dynamics, the bacterial community succession present in the vermibeds, as well as maturation and the end-quality of the vermicompost. Our results show that the addition of liquid digestate to the vermibeds increased the earthworms biomass, i.e. 71%, 94% and 168% in control, and vermibeds with 30% and 60% digestate, respectively. Further, the increase in the amount of N in the vermicompost decreased as the digestate addition increased, i.e. 75%, 8%, 3%. The maturity achieved was high in all treatments as shown by the C/N ratio, 7.98, 7.40 and 10.20, and the high seed germination rate, above 90%. Finally, the succession of the microbial community was not disturbed and compositional stabilization was reached after 92 days.
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Pedrouso, A., Vazquez-Padin, J. R., Crutchik, D., & Campos, J. L. (2021). Application of Anammox-Based Processes in Urban WWTPs: Are We on the Right Track? Processes, 9(8), 1334.
Abstract: The application of partial nitritation and anammox processes (PN/A) to remove nitrogen can improve the energy efficiency of wastewater treatment plants (WWTPs) as well as diminish their operational costs. However, there are still several limitations that are preventing the widespread application of PN/A processes in urban WWTPs such as: (a) the loss of performance stability of the PN/A units operated at the sludge line, when the sludge is thermally pretreated to increase biogas production; (b) the proliferation of nitrite-oxidizing bacteria (NOB) in the mainstream; and (c) the maintenance of a suitable effluent quality in the mainstream. In this work, different operational strategies to overcome these limitations were modelled and analyzed. In WWTPs whose sludge is thermically hydrolyzed, the implementation of an anerobic treatment before the PN/A unit is the best alternative, from an economic point of view, to maintain the stable performance of this unit. In order to apply the PN/A process in the mainstream, the growth of ammonia-oxidizing bacteria (AOB) should be promoted in the sludge line by supplying extra sludge to the anaerobic digesters. The AOB generated would be applied to the water line to partially oxidize ammonia, and the anammox process would then be carried out. Excess nitrate generated by anammox bacteria and/or NOB can be removed by recycling a fraction of the WWTP effluent to the biological reactor to promote its denitrification.
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Valenzuela-Heredia, D., Panatt, C.:, Belmonte, M., Franchi, O., Crutchik, D., Dumais, J., Vazquez-Padin, J. R., et al. (2022). Performance of a two-stage partial nitritation-anammox system treating the supernatant of a sludge anaerobic digester pretreated by a thermal hydrolysis process. Chem. Eng. J., 429, 131301.
Abstract: A two-stage system (partial nitritation (PN) and anammox processes) was used to remove nitrogen from the dewatering liquor originating from the thermal hydrolysis/anaerobic digestion (THP/AD) of municipal WWTP sludge. Two strategies were tested to start up the PN reactor: 1) maintaining a fixed hydraulic retention time (HRT) and increasing the ammonium loading rate (ALR) by decreasing the feeding dilution ratio and 2) feeding undiluted dewatering liquor and gradually decreasing the HRT. With diluted feeding, the reactor performance had destabilization episodes that were statistically correlated with the application of high specific ammonium (> 0.6 g NH4+-N/(g TSS.d)) and organic (> 0.7 g COD/(g TSS.d)) loading rates. The second strategy allowed stable PN reactor operation while treating ALR up to 4.8 g NH4+-N/(L.d) and demonstrating that dilution of THP/AD effluents is not required. The operating conditions promoted the presence of free nitrous acid levels (> 0.14 mg HNO2-N/L) inside the PN reactor that inhibited the proliferation of nitrite oxidizing bacteria.
Batch activity tests showed that the inhibitory effects of organic compounds present in the THP/AD dewatering liquor on the ammonia oxidizing bacteria activity can be removed in the PN reactor. Thus, aerobic pretreatment would not be necessary when two-stage systems are used. The PN reactor effluent was successfully treated by an anammox reactor.
An economic analysis showed that using two-stage systems is advantageous for treating THP/AD dewatering liquor. The implementation of an aerobic pre-treatment unit is recommended for WWTPs capacities higher than 5.10(5) inhabitants equivalent when one-stage systems are used.
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