| Home | << 1 >> |
|
Cofre, C., Campos, J. L., Valenzuela-Heredia, D., Pavissich, J. P., Camus, N., Belmonte, M., et al. (2018). Novel system configuration with activated sludge like-geometry to develop aerobic granular biomass under continuous flow. Bioresour. Technol., 267, 778–781.
Abstract: A novel continuous flow system with “flat geometry” composed by two completely mixed aerobic tanks in series and a settler was used to promote the formation of aerobic granular sludge. Making similarities of this system with a typical sequencing batch reactor (SBR), for aerobic granules cultivation, the value of the tank 1/tank 2 vol ratio and the biomass recirculation rate would correspond with the feast/famine length ratio and the length of the operational cycle, respectively, while the settler upflow liquid velocity imposed would be related to the settling time. From the three experiments performed the best results were obtained when the tank 1/tank 2 vol ratio was of 0.28, the sludge recycling ratio of 0.25 and the settler upflow velocity of 2.5 m/h. At these conditions the aggregates had settling velocities between 29 and 113 m/h, sludge volume index at 10 min (SVI10) of 70 mL/g TSS and diameters between 1.0 and 5.0 mm.
|
|
Diaz, C., Belmonte, M., Campos, J. L., Franchi, O., Faundez, M., Vidal, G., et al. (2020). Limits of the anammox process in granular systems to remove nitrogen at low temperature and nitrogen concentration. Process Saf. Environ. Protect., 138, 349–355.
Abstract: When partial nitritation-anammox (PN-AMX) processes are applied to treat the mainstream in wastewater treatment plants (WWTPs), it is difficult to fulfil the total nitrogen (TN) quality requirements established by the European Union (<10g TN/m(3)). The operation of the anammox process was evaluated here in a continuous stirred tank reactor operated at 15 degrees C and fed with concentrations of 50 g TN/m(3) (1.30 +/- 0.23 g NO2- -N/g NH4+-N). Two different aspects were identified as crucial, limiting nitrogen removal efficiency. On the one hand, the oxygen transferred from the air in contact with the mixed liquor surface favoured the nitrite oxidation to nitrate (up to 75 %) and this nitrate, in addition to the amount produced from the anammox reaction itself, worsened the effluent quality. On the other hand, the mass transfer of ammonium and nitrite to be converted inside the anammox granules involves relatively large values of apparent affinity constants (k(NH4+app) : 0.50 g NH4+-N/m(3) ; k(NO2-app) 0.17 g NO2--N/m(3)) that favour the presence of these nitrogen compounds in the produced effluent. The careful isolation of the reactor from air seeping and the fixation of right hydraulic and solids retention times are expected to help the maintenance of stability and effluent quality. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Keywords: Anammox; Dissolved oxygen; Granular biomass; Nitrogen; SRT; Temperature
|
|
Ludlow, J., Jalil-Vega, F., Rivera, X. S., Garrido, R. A., Hawkes, A., Staffell, I., et al. (2021). Organic waste to energy: Resource potential and barriers to uptake in Chile. Sustain. Prod. Consum., 28, 1522–1537.
Abstract: Achieving net-zero greenhouse gas emissions by 2050 requires a step-change in resource manage-ment, and the utilisation of organic waste is currently an untapped opportunity in Latin America. This study carries out a quantitative and qualitative assessment of organic waste-to-energy potentials for the Chilean context. First, it produces a comprehensive quantification of organic waste, including annual crop residues, horticulture residues, livestock manure and OFMSW by region; then it estimates the energy potential of these bioresources; and finally, it conducts a series of stakeholder interviews determining barriers to greater waste-to-energy utilisation. The results show that the total bioenergy potential from waste is estimated at 78 PJ/yr (3.3% of annual energy demand), being livestock manure (41%) and annual crop residues (28%) the main sources, arising mostly from three regions. The stakeholder elicitation concluded that financial, technical, and institutional barriers prevent waste utilisation, highlighting the needs to address elevated investment costs and high reliance on landfilling practices, which together with public policies could enable the full exploitation of these resources to ensure energy security and resource efficiency. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
|
|
Pedrouso, A., Aiartza, I., Morales, N., Vazquez-Padin, J. R., Rogalla, F., Campos, J. L., et al. (2018). Pilot-scale ELAN (R) process applied to treat primary settled urban wastewater at low temperature via partial nitritation-anammox processes. Sep. Purif. Technol., 200, 94–101.
Abstract: A single stage partial nitritation and anammox granular pilot scale reactor (600 L) was operated to treat primary settled sewage in an urban wastewater treatment plant. The fed wastewater contained low total nitrogen concentrations of 6-25 mg TN/L and the system operated without temperature control ranging from 18 to 12 degrees C. A control strategy, based on the pH value, was applied to stop the aeration supply. The pH set-point was fixed at 6.0 and allowed obtaining a total nitrogen removal efficiency approximately of 50% treating a load of 67 mg TN/(L.d) without the addition of any chemicals. Although nitrite oxidizing bacteria were present in the inoculated sludge, when the pH-based control was implemented (day 30) the ammonium oxidation was favored compared to the nitrite oxidation activity. Then, the system operated stable the rest of the operational period (days 30-94) despite the presence of organic matter in the wastewater and the high variability of nitrogen load and temperature during the operation. Nitrogen was autotrophically removed accomplishing the stringent discharge limits (10 mg TN/L) and nitrate concentrations in the effluent lower than 3 mg NO3--N/L. Both biomass concentration and granules size increased during the operational period indicating the growth of the biomass inside the reactor and therefore the potential treatment capacity.
|
|
Perez-Quezada, J. F., Perez, C. A., Brito, C. E., Fuentes, J. P., Gaxiola, A., Aguilera-Riquelme, D., et al. (2021). Biotic and abiotic drivers of carbon, nitrogen and phosphorus stocks in a temperate rainforest. Forest. Ecol. Manag., 494, 119341.
Abstract: Forest ecosystems are recognized for their large capacity to store carbon (C) in their aboveground and belowground biomass and soil pools. While the distribution of C among ecosystem pools has been extensively studied, less is known about nitrogen (N) and phosphorus (P) pools and how these stocks relate to each other. There is also a need to understand how biotic and abiotic ecosystem properties drive the magnitude and distribution of CN-P stocks. We studied a temperate rainforest in southern South America to answer the following questions: 1) how are C-N-P total stocks distributed among the different ecosystem pools?, 2) how do C:N, C:P and N:P ratios vary among ecosystem pools?, and 3) which are the main biotic and abiotic drivers of C-N-P stocks? We established 33 circular plots to estimate C, N, and P stocks in different pools (i.e. trees, epiphytes, understory, necromass, leaf litter, and soil) and a set of biotic (e.g., tree density and richness) and abiotic variables (e.g., air temperature, humidity and soil depth). We used structural equation modeling to identify the relative importance of environmental drivers on C-N-P stocks. We found that total ecosystem stocks (mean +/- SE) were 1062 +/- 58 Mg C ha-1, 28.8 +/- 1.5 Mg N ha-1, and 347 +/- 12.5 kg P ha-1. The soil was the largest ecosystem pool, containing 68%, 92%, and 73% of the total C, N, and P stocks, respectively. Compared to representative temperate forests, the soil of this forest contains the largest concentrations and stocks of C and N. The low P stock and wide soil C:P and N:P ratios suggest that P may be limiting forest productivity. The ecosystem C-N-P stocks were mainly driven by abiotic properties measured in the study area, however for N stocks, variables such as plant diversity and canopy openness were also relevant. Our results provide evidence about the importance not only of understanding the differences in C, N, and P stocks but also of the factors that drive such differences. This is key to inform conservation policies related to preserving old-growth forests in southern South America, which indeed are facing a rapid land-use change process.
|
|
Simon, F., Girard, A., Krotki, M., & Ordonez, J. (2021). Modelling and simulation of the wood biomass supply from the sustainable management of natural forests. J. Clean. Prod., 282, 124487.
Abstract: Wood biomass is an important energy resource, which can contribute to reduce the dependence on fossil fuels. The research undertakes the microeconomic approach to estimate the technical availability and operational costs of woody biomass production with a higher level of precision than other models present in the literature, as it considers the entire supply chain of the sustainable management of natural forests. This study introduces a tool, which is applied to estimate supply curves and costs of wood biomass extraction from natural forests in the 7th Region of Chile. The simulation indicates that 531,015 tons/year of wood biomass is available in natural forests of the Region under study, with extraction costs ranging from 24.51 to 56.68 US$/ton, or an average total cost of 40.97 US$/ton. The parametric analysis revealed that the maximum admissible distance to the nearest transport route and the transportation costs are the two most influential variables in the estimation of wood biomass supply and cost. Reducing the admissible distance from 5 km to 1 km reduced the availability of biomass by 80%, while a variation of +/- 50% of transportation costs translated into +/- 18.3% variation of total extraction costs.
The proposed method can be used to identify the technical-economic potential of wood biomass from natural forests in any commune, province, region, or country; as it has the flexibility to allow tests with multiple scenarios and parameters depending on the specific characteristics of the area to be analysed. Essentially, the purpose of this tool is to serve the assessment processes of the identification of new wood biomass resources, allowing decision makers to increase the potential of sustainable and cost-effective woody biomass for heat and electricity generation, and at the same time reduce greenhouse gas emissions and the dependence on fossil fuels. |