Assessing the phytotoxicity of wastewater from the structured-bed hybrid baffled reactor (SBHBR) for agricultural reuse during the germination phase.

This study investigated the quality of anaerobic (AnE) and oxic/anoxic (O/A) effluents from a continuous-feed structured-bed hybrid baffled reactor (SBHBR) treating dairy wastewater impacts on lettuce and cucumber germination. While sustainable technologies like SBHBR have successfully removed organic matter and total nitrogen from dairy wastewater, residual concentrations may still represent a risk to water resources. Therefore, phytotoxicity bioassays were conducted with lettuce and cucumber seeds in contact with effluent during early stages to evaluate the potential implications of dairy wastewater reuse in agriculture. The study also explored the potential of SBHBR technology in promoting water resource preservation and creating a sustainable energy and nutrient cycling system. The physicochemical parameters of both effluents were characterized, and the phytotoxicity was evaluated by measuring the germination index (GI), root length (RL), the number of germinated seeds (SG), and epicotyl elongation (EE) for both lettuce and cucumber. The study revealed that the O/A effluent demonstrated lower phytotoxicity than the AnE effluent. The mean results indicate that the O/A zone wastewater was more conducive to cucumber germination than the AnE zone. Moreover, a positive influence of organic matter in the effluent on root growth and epicotyl elongation in cucumber, as well as the presence of nitrogen on the germination index, in both plant species. These findings emphasize the importance of considering effluent characteristics for suitable irrigation, highlighting SBHBR's potential as an effective solution for treating and reusing dairy wastewater in agriculture. This approach helps conserve water resources and promote a sustainable energy and nutrient cycling system.

The dissolved methane recovery from treated sewage in upflow anaerobic sludge blanket (UASB) reactors: The energy demand, carbon footprint and financial cost.

The goal of this research was to quantify the energy demand and carbon footprint over the life cycle, along with the financial cost, of sewage treatment with the recovery of dissolved methane (d-CH4). The sewage treatment is composed of pre-treatment, followed by treatment in upflow anaerobic sludge blanket (UASB) reactors, trickling filter and secondary decanter, post-treatment with disinfection, and biogas recovery in the three-phase separator of the UASB reactor. The methods used in this study were attributional life cycle assessment and techno-economic analysis - LCA and TEA, respectively. The energy demand, carbon footprint and financial cost for 1 m3 sewage treatment in the evaluated scenario without d-CH4 recovery (S1) were 3.4 MJ, 1.7 kg CO2eq and 0.17 USD respectively, while those with d-CH4 recovery (S2) varied by 12%, -16% and 2.3% compared to S1. The produced biogas for lower heating value in S2 (2.6 MJ) was 27% higher than that in S1 (2.0 MJ) and this varied from 1.3 MJ to 4.6 MJ in the scenarios for different influent chemical oxygen demand (COD) in the sewage treatment plant (STP) and COD removal efficiency in the UASB reactor. The highest eco-efficiency for 1 MJ heat production from the STP biogas was achieved in the scenario with d-CH4 recovery, higher influent COD, higher COD removal efficiency in the UASB reactor, d-CH4 saturation, photovoltaic electricity supply, and a higher energy efficiency in d-CH4 recovery combined (S2,COD+,R+,S,PV,EE+), which reduced the energy demand by 55%, carbon footprint by 66% and financial cost by 63% compared to S1. Furthermore, the STP functionality change from a single-product (biogas) to a multi-product (biogas, water for reuse and biosolid fertilizer) approach (S1,WR, BF and S2,WR,BF) made the biogas a competitive product compared to those from fossil sources. Therefore, resource recovery from the sewage treatment in higher influent COD, higher COD removal efficiency, the use of a more efficient, clean and economical electricity source and higher energy efficiency in d-CH4 recovery in a multi-product STP contribute to achieving the energy self-sufficiency over the life cycle while reducing the carbon footprint and financial cost of its products.

Evaluating the potential of a new reactor configuration to enhance simultaneous organic matter and nitrogen removal in dairy wastewater treatment.

The dairy industry is a very productive sector worldwide and known for producing great volumes of wastewater that is rich in organic matter and nutrients. Apart from fat, the organic matter in such effluents is easily degradable, demanding an external carbon source for conventional denitrification. In this manner, new configurations of reactors promoting a suitable environment for more sustainable nitrogen removal are beyond required-they are paramount. Therefore, the performance of a structured-bed hybrid baffled reactor (SBHBR) with anaerobic and oxic/anoxic chambers was designed and assessed for treating different dairy wastewaters. A combination of baffled and biofilm-structured systems under intermittent aeration was the solution proposed to obtain a new method for nitrogen removal under low COD/TN ratios. The COD/TN ratios tested were 2.1 ± 0.6, 0.84 ± 0.5, and 0.35 ± 0.1 in the inlet of the O/A chambers for operational stages I, II, and III, respectively. The SBHBR provided COD removal efficiencies above 90% in all experimental stages. During stage III, the process had nitrification and denitrification efficiencies of 85.9 ± 17% and 85.2 ± 9%, respectively, resulting in a TN removal efficiency of 74.6 ± 14.7%. Stoichiometric calculations were used to corroborate the activity of bacteria that could perform the anammox pathways as their main mechanisms.

Comparative homology of Pleurotus ostreatus laccase enzyme: Swiss model or Modeller?

Laccases stand out in the industrial context due to their versatile biotechnological applications. Although these enzymes are frequently investigated, currently, Pleurotus ostreatus laccase structural model is unknown. Therefore, this research aims to predict and validate a P. ostreatus laccase theoretical model by means of comparative homology. The laccase target's primary structure (AOM73725.1) was obtained from the NCBI database, the model was predicted from homologous structures obtained from the PDB (PDB-ID: 5A7E, 2HRG, 4JHU, 1GYC) using the Swiss-Model and Modeller, and was refined in GalaxyRefine. The models were validated using PROCHECK, VERIFY 3D, ERRAT, PROVE and QMEAN Z-score servers. Moreover, molecular docking between the laccase model (Lacc4MN) and ABTS was performed on AutoDock Vina. The models that were generated by the Modeller showed superior stereochemical and structural characteristics to those predicted by the Swiss Model. The refinement made it difficult to stabilize the copper atoms which are typical of laccases. The Lacc4MN model showed the interactions between the amino acids in the active site of the laccase and the copper atoms, thereby hinting the stabilization of the metal through electrostatic interactions with histidine and cysteine. The molecular docking between Lacc4MN and ABTS showed negative free energy and the formation of two hydrogen bonds involving the amino acids ASP 208 and GLY 268, and a Pi-sulfur bond between residue HIS 458 and ABTS, which demonstrates the typical catalytic functionality of laccases. Furthermore, the theoretical model Lacc4MN presented stereochemical and structural characteristics that allow its use in silico tests.Communicated by Ramaswamy H. Sarma.

Enhanced anaerobic digestion of post-hydrothermal liquefaction wastewater: Bio-methane production, carbon distribution and microbial metabolism.

Hydrothermal liquefaction (HTL) is a cost-effective and environment-friendly technology for using biomass to produce bio-crude oil. The critical challenge of HTL is its complicated aqueous product containing high concentrations of organics and diverse toxicants. This paper reports the continuous anaerobic digestion of raw and zeolite-adsorbed Chlorella HTL wastewater using up-flow anaerobic sludge bed reactors. The bio-methane production capacity, total carbon distribution and microbial response were investigated. The anaerobic process was severely suppressed when more than 20% raw wastewater was fed; while it showed essentially improved performance till 60% pre-treated wastewater was added. Produced methane contained 17.3% of the total carbon in feedstock, which was comparable with the value (16.7%) when 25% of raw wastewater was added. The metagenomic analysis revealed distinct microbial community structures in different stages and feedstock shifts. The abundance of functional genes was consistent with anaerobic digester performance.

Anaerobic digestion of aqueous phase from hydrothermal liquefaction of Spirulina using biostimulated sludge.

Hydrothermal liquefaction is a process that converts wet biomass into biofuels, more specifically bio-crude oil. During the process, post hydrothermal liquefaction waste water (PHWW) is generated, rich in nutrient and organic matter, however potentially toxic. Anaerobic digestion of PHWW from Spirulina, was evaluated using biostimulated sludge as a strategy to optimize the process. The biostimulation was conducted in a sequential batch reactor fed with organic acids and methanol aiming at development of acetogenic and methanogenic microorganism. Anaerobic biodegradability batch assays were performed, with biostimulated sludge and with non-biostimulated sludge, using increasing PHWW concentrations. Biostimulated sludge were more favourable for reaching higher methane yields at higher organic matter concentrations in comparison to non-biostimulated sludge, presenting less inhibition at conditions tested. Biostimulation was a key process to select and favour potential microorganisms involved in specialized uptake of recalcitrant compounds, such as Mesotoga and Methanomethylovorans.

Potential benefits of near critical and supercritical pre-treatment of lignocellulosic biomass towards anaerobic digestion.

Vegetable crop residues, such as sugarcane bagasse (SCB), despite their limited biodegradability, are potential materials for anaerobic processes because of their low cost, high availability, and sugar content. The difficulty of biodegrading this type of material is primarily related to its chemical composition and to the complex interactions between its compounds (cellulose, hemicelluloses, and lignin). Thus, the following supercritical and near critical carbon dioxide (CO2) pre-treatments were evaluated with and without the addition of sodium hydroxide (NaOH): (i) 40°C/70 kgf·cm-2; (ii) 60°C/200 kgf·cm-2; and (iii) 80°C/200 kgf·cm-2, aiming to enhance the anaerobic biodegradability of SCB. The methanogenic production of SCB increased in all cases in which the material was pre-treated, except the case in which NaOH was used together with a high temperature. The condition using CO2 at 60°C/200 kgf·cm-2 was highlighted with a lignin removal of 8.07% and an accumulated methane production of 0.6498 ± 0.014 LN (273.15K, 1.01325 × 105 Pa), 23.4% higher than the value obtained with the untreated material. This condition also showed the highest net energy at the energy balance that was calculated for comparison with the tested conditions. The results showed that pre-treatments with near critical and supercritical fluids have the potential to reduce structural obstacles of lignocellulosic materials and to enhance their anaerobic biodegradability.

Anaerobic digestion of post-hydrothermal liquefaction wastewater for improved energy efficiency of hydrothermal bioenergy processes.

Hydrothermal liquefaction (HTL) is a promising process for converting wet biomass and organic wastes into bio-crude oil. It also produces an aqueous product referred to as post-hydrothermal liquefaction wastewater (PHWW) containing up to 40% of the original feedstock carbon, which reduces the overall energy efficiency of the HTL process. This study investigated the feasibility of using anaerobic digestion (AD) to treat PHWW, with the aid of activated carbon. Results showed that successful AD occurred at relatively low concentrations of PHWW (≤ 6.7%), producing a biogas yield of 0.5 ml/mg CODremoved, and ∼53% energy recovery efficiency. Higher concentrations of PHWW (≥13.3%) had an inhibitory effect on the AD process, as indicated by delayed, slower, or no biogas production. Activated carbon was shown to effectively mitigate this inhibitory effect by enhancing biogas production and allowing digestion to proceed at higher PHWW concentrations (up to 33.3%), likely due to sequestering toxic organic compounds. The addition of activated carbon also increased the net energy recovery efficiency of AD with a relatively high concentration of PHWW (33.3%), taking into account the energy for producing activated carbon. These results suggest that AD is a feasible approach to treat PHWW, and to improve the energy efficiency of the HTL processes.

Chemical characterization and anaerobic biodegradability of hydrothermal liquefaction aqueous products from mixed-culture wastewater algae.

This study examined the chemical characteristics and the anaerobic degradability of the aqueous product from hydrothermal liquefaction (HTL-ap) from the conversion of mixed-culture algal biomass grown in a wastewater treatment system. The effects of the HTL reaction times from 0 to 1.5 h, and reaction temperatures from 260 °C to 320 °C on the anaerobic degradability of the HTL-ap were quantified using biomethane potential assays. Comparing chemical oxygen demand data for HTL-ap from different operating conditions, indicated that organic matter may partition from organic phase to aqueous phase at 320 °C. Moderate lag phase and the highest cumulative methane production were observed when HTL-ap was obtained at 320 °C. The longest lag phase and the smallest production rate were observed in the process fed with HTL-ap obtained at 300 °C. Nevertheless, after overcoming adaptation issues, this HTL-ap led to the second highest accumulated specific methane production. Acetogenesis was identified as a possible rate-limiting pathway.

Characterization of aqueous phase from the hydrothermal liquefaction of Chlorella pyrenoidosa.

This study investigated the characteristics of aqueous phase from hydrothermal liquefaction of low-lipid microalgae Chlorella pyrenoidosa. The interactions of operating conditions, including reaction temperature, retention time and total solid ratio were evaluated by response surface methodology. The chemical oxygen demand, total nitrogen and total phosphorus were selected as indicators of the property of AP. Results indicated that total solid ratio was found to be the dominant factor affecting the nutrient recovery efficiencies of AP. Based on energy recovery, GC-MS indicated that the AP at two optimized operating conditions (280 °C, 60 min, 35 wt.% and 300 °C, 60 min, 25 wt.%) were observed to have a higher concentration of organic acids (10.35% and 8.34%) while the sample (260 °C, 30 min, 35 wt.%) was observed to have the highest concentration of N&O-heterocyclic compounds (36.16%).

Caracterização e cinética do tratamento anaeróbio de efluentes de laticínios / Characterization and kinetics of the anaerobic treatment of dairy wastewaters

A geração de efluentes do setor de laticínios é imensa e, em função do conteúdo emulsionado de gorduras, tais efluentes são tidos como de difícil degradação. O presente artigo teve como objetivo a caracterização dos efluentes gerados por um laticínio que processa 800 L de leite por dia, relacionando suas características com as ocorrências na planta. Este laticínio produz leite pasteurizado, mussarela, queijo Minas frescal, sorvete e iogurte. O efluente dos processos concomitantes de produção de mussarela e pasteurização de leite foi utilizado para alimentação de um reator UASB (upflow anaerobic sludge blanket) híbrido (UASBh), e através da aplicação de cargas orgânicas volumétricas crescentes, foi realizado o estudo cinético do sistema. A maior carga específica calculada para os efluentes estudados foi referente ao processamento de mussarela, em função do abundante volume de soro descartado. As concentrações de sais e metais encontradas nos efluentes analisados se mostraram muito aquém das recomendadas como necessárias ao balanceado crescimento do consórcio anaeróbio. A concentração de lipídeos não representou problema em efluentes da produção de iogurte, uma vez que foram sempre inferiores a 18,9 mg.L-1 (valores típicos de efluentes diluídos). O reator do tipo UASBh operou de forma estável com carga orgânica volumétrica (COV) média aplicada de até 8,9 kg.m-3.d-1, carga esta superior à preconizada na literatura como segura. Com COV média aplicada de 15,4 kg.m-3.d-1, a velocidade de consumo de substrato não acompanhou o aumento da oferta, mantendo-se praticamente constante, resultando em queda na eficiência do processo e em sua estabilidade.

The generation of effluents from the dairy industry is huge and deemed difficult degradation, depending on the content of emulsified fats.This study aimed to characterize the effluent emitted by a dairy which process 800 L of milk daily, relating its features to the events at the plant. The plant processes pasteurized milk, cheese, ice-cream and yogurt. The effluent of the concurrent processes of mozzarella making and milk pasteurization was used to power a hybrid UASB reactor. By applying increasing volumetric organic loads, we performed a kinetic study of the system. The most specific charge calculated for the effluent was from the mozzarella processing due to the large volumes of whey discarded. The concentrations of salts and metals found in wastewater analyzed were very below to the required and recommended by balanced growth of the anaerobic consortium. The lipids concentration in effluent was not a problem in the production of yogurt, since they were lower than 18.9 mg L-1 (typical values of diluted effluents). The UASBh reactor presented stability when the applied organic loading rate (OLR) was until 8.9 kg.m-3.d-1. With superior values, the rate of substrate consumption did not follow the increase in supply of organic matter, remaining almost constant, resulting in a drop in efficiency and stability.

Avaliação e perspectiva de aplicação de mecanismos de desenvolvimento limpo em indústrias de alimentos e bebidas no Brasil / Potential assessment of prospective application of clean development mechanisms concerning Brazilian food and beverage industries

Este trabalho tem como objetivo discutir o potencial de aplicação de Mecanismo de Desenvolvimento Limpo (MDL) por indústrias de alimentos e bebidas no Brasil. Evocando dados oficiais, a presente análise demonstra que a indústria de alimentos e bebidas é capaz de aumentar sua participação em projetos de MDL. Com base nos dados apresentados, pode-se perceber que o setor estudado (a) tem um elevado potencial de economia de energia, (b) possui fontes consideráveis de biomassa, (c) é capaz de reduzir suas emissões em grande medida e (d) pode melhorar o seu tratamento de resíduos. Tendo em mente as emissões de gases de efeito estufa, efluentes líquidos e disponibilidade de biomassa, respectivamente, verificam-se níveis mais elevados no setor de alimentos e bebidas em comparação com qualquer outro setor industrial, muito em função da biodegradabilidade de suas emissões. Tal fato sugere que a indústria de alimentos e bebidas tem grande potencial para implementar projetos de desenvolvimento sustentável.

This study aims at discussing the potential exploitation of Clean Development Mechanism (CDM) by Brazilian food and beverage industry. By evoking official data (e.g. Brazilian Energy Balance Report and Brazilian Initial Communication to United Nations Conference on Climate Change), the present analysis demonstrates that Brazilian food and beverage industry is positively able to enhance its participation at proposed CDM projects and thus contribute to greenhouse effect mitigation. Based on presented data and as far as the food and beverage industrial sector is concerned, one may realize that (a) it has a high potential for energy saving, (b) it possesses considerable sources of biomass, (c) it is able to reduce its emissions to a large extent and (d) it may improve its residue treatment. Bearing in mind GHG emission, liquid effluents and biomass availability, food and beverage industry present higher levels than any other industrial sector. This fact suggests that the food and beverage sector has a considerable potential to implement sustainable development projects, thus helping to reduce pollutant emission to the environment.