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Two municipal wastewater treatment plants (WWTPs), based on activated sludge process (ASP) and rotating biological contactors (RBC) as biological treatments, were comparatively evaluated in terms of their operational conditions, bacterial content and physicochemical characteristics of their derived sludge (SL) to determine their influence on odor impact. The average values of influent wastewater flow, inlet chemical oxygen demand (COD) and COD removal efficiency were (ASP-WWTP vs. RBC-WWTP): 447 vs. 689 m3/d, 300 vs. 423 mg/L and 88.28 vs. 83.17%, respectively. Regarding the global odor emissions, ASP-WWTP and RBC-WWTP had a similar odor emission rate (11,177 ouds and 12,784 ouE/s, respectively), with sludge thickening and dewatering being the major sources of odor in both facilities. Proteobacteria, Bacteroidetes and Firmicutes were the three predominant phyla in both WWTPs, representing the 83% in ASP-SL and the 97% in RBC-St. RBC-SL showed lower bacterial biodiversity than ASP-SL. The higher odor concentration from the sludge handling activities in RBC-WWTP were linked to the significative increments iii the abundance of Porphyromonadaceae, Clostridiales, Lachnospiraceae (obligate anaerobe) and Moraxellaceae (aerobic) families compared to ASP-WWTP. However, when odor emissions were evaluated pei· equivalent inhabitant (El), a higher value was obtained for ASP-WWTP (16.22 ouE/s·El) compared to RBC-WWTP (6.84 ou E/s·El). [ABSTRACT FROM AUTHOR]

This study evaluates the feasibility of using simultaneous mass balances of different nutrients as a tool for optimizing feeding composition in anaerobic digestion. Different ratios, among them total chemical oxygen demand/total Kjeldahl nitrogen (TCOD/TKN) and soluble chemical oxygen demand/TCOD (SCOD/TCOD), were assessed. The TCOD/total volatile solids (TVS) ratio was 1.73 kg O2/kg TVS, while, with the exception of the sewage sludge, pig slurry and animal wastes, a linear relationship was established between phosphorus and nitrogen (0.06 kg P/kg TKN (R2 = 0.9045)). The study was applied to different mixtures of waste (cucumber, quince, tomato, strawberry waste, vinasse, glycerol, tomato plant, pig slurry, sewage sludge, fish waste, landfill leachate and viscera). The mass balance was performed for 50 mixtures chosen at random, containing three different wastes. After evaluating the theoretical optimal values determined by the mass balances, the most promising data were compared with the experimental results of the anaerobic co-digestion of one of the three waste mixtures. As predicted by the mass balances, the codigestion of glycerol, strawberry extrudate and fish waste (41:54:4 in VS) improved methane production to a maximum value of 0.308 m3 CH4/kg TVSadded for an organic loading rate of 0.62-4.26 kg TVS/m3·d. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) offer a suitable alternative to conventional solvents in terms of both performance and cost-effectiveness. Some DESs also offer certain green features, the greenness of which is notoriously enhanced when combined with water. Aqueous DES dilutions are therefore attracting great attention as a novel green medium for biotechnological processes, with the aqueous dilutions of reline – a DES composed of urea and choline chloride – being one of the most studied systems. Despite their macroscopic homogeneous appearance, both 1H NMR spectroscopic studies and molecular dynamics simulations have revealed the occurrence of certain dynamic heterogeneity at a microscopic molecular level. Ultrasonic measurements were also used with the aim of getting further insights but nonconclusive results were obtained. Herein, we have studied aqueous reline dilutions by Brillouin spectroscopy given its proved suitability for detecting local structure rearrangements in liquid mixtures of H-bonded co-solvents. Brillouin spectroscopy revealed the formation of a co-continuous structure resulting from local structure rearrangements and micro-segregation into aqueous and DES phases. Interestingly, there is agreement between 1H NMR and Brillouin spectroscopy when pointing to the DES content where microphase segregation and formation of co-continuous structures occurred. [ABSTRACT FROM AUTHOR]

The composting process of six different compostable substrates and one of these with the addition of bacterial inoculums carried out in a dynamic respirometer was evaluated. Despite the heterogeneity of the compostable substrates, cumulative oxygen demand (OD, mg O2 kg VS) was fitted adequately to an exponential regression growing until reaching a maximum in all cases. According to the kinetic constant of the reaction (K) values obtained, the wastes that degraded more slowly were those containing lignocellulosic material (green wastes) or less biodegradable wastes (sewage sludge). The odor emissions generated during the composting processes were also fitted in all cases to a Gaussian regression with R2 values within the range 0.8-0.9. The model was validated representing real odor concentration near the maximum value against predicted odor concentration of each substrate, (R² = 0.9314; 95% prediction interval). The variables of maximum odor concentration (ouE/m³) and the time (h) at which the maximum was reached were also evaluated statistically using ANOVA and a post-hoc Tukey test taking the substrate as a factor, which allowed homogeneous groups to be obtained according to one or both of these variables. The maximum oxygen consumption rate or organic matter degradation during composting was directly related to the maximum odor emission generation rate (R² = 0.9024, 95% confidence interval) when only the organic wastes with a low content in lignocellulosic materials and no inoculated waste (HRIO) were considered. Finally, the composting of OFMSW would produce a higher odor impact than the other substrates if this process was carried out without odor control or open systems. [ABSTRACT FROM AUTHOR]