Search

Scenedesmus obliquus (ACOI 204/07) microalgae were cultivated in cattle wastewater in vertical alveolar flat panel photobioreactors, operated in batch and continuous mode, after previous digestion in a hybrid anaerobic reactor. In batch operation, removal efficiencies ranges of 65 to 70% of COD, 98 to 99% of NH 4 + and 69 to 77.5% of PO 4 -3 after 12days were recorded. The corresponding figures for continuous flow were from 57 to 61% of COD, 94 to 96% of NH 4 + and 65 to 70% of PO 4 -3 with mean hidraulic retention time of 12days. Higher rates of CO 2 fixation (327-547mgL -1 d -1 ) and higher biomass volumetric productivity (213-358mgL -1 d -1 ) were obtained in batch mode. This microalgae-mediated process can be considered promising for bioremediation and valorization of effluents produced by cattle breeding yielding a protein-rich microalgal biomass that could be eventually used as cattle feed., (Copyright © 2018 Elsevier B.V. All rights reserved.)

New data on biogas production and treatment of cattle wastewater were registered using an upflow anaerobic sludge blanket-anaerobic filter (UASB-AF) hybrid reactor under mesophilic temperature conditions (37 °C). The reactor was operated in semi-continuous mode with hydraulic retention times of 6, 5, 3 and 2 days and organic loading rates of 3.8, 4.6, 7.0 and 10.8 kg COD t m -3 d -1 . Biogas volumes of 0.6-0.8 m 3 m -3 d -1 (3.8-4.6 kg COD t m -3 d -1 ) and 1.2-1.4 m 3 m -3 d -1 (7.0-10.8 kg COD t m -3 d -1 ), with methane concentrations between 69 and 75%, were attained. The removal of organic matter with values of 60-81% (COD t ) and 51-75% (COD s ) allowed methane yields of 0.155-0.183 m 3 CH 4 kg -1 COD t and 0.401-0.513 m 3 CH 4 kg -1 COD s to be obtained. Volatile solids were removed in 34 to 69%, with corresponding methane yields of 0.27 to 0.42 m 3 CH 4 kg -1 VS removed . The good performance of the novel hybrid reactor was demonstrated by biogas outputs higher than reported previously in the literature, along with the quality of the gas obtained in the various experimental phases. The hybrid reactor investigated in this study presents comparative advantages, particularly in relation to conventional complete mixture units, considering economic factors such as energy consumption, reactor volume and installation area.

The increased demand for energy results in an increase in fossil fuel consumption. However, the planet's oil deposits will soon reach unsustainable levels, presenting an opportunity for biofuels. In this study, cattle wastewater (CWW) was used to cultivate a microalgae consortium in photobioreactors. Seven rounds of experiments were carried out with the addition of CO2 (ControlCO2), ozone application for 10, 20, and 30 min (O3T10, O3T20, and O3T30), and a combination of CO2 and ozone (O3T10CO2 and O3T20CO2). Maximum dry biomass (18.63 g/L) and CO2 biofixation (8047.79 mg/L/d) were obtained in O3T20CO2. A total of 48% of lipid was registered in O3T30 and O3T20, indicating that microalgae were stressed when exposed to ozonized wastewater. C16:0 was detected in higher concentrations in all experiments. O3T30, O3T10CO2, and O3T20CO2 had values for C18:3 in accordance with the requirements of EN 14,214. Projections show that a farm with 2000 animals could produce 430 g of biofuels per kg of biomass and fixed 2.67 tCO2/y. Removals of up to 100% for NH3–N, 99.6% for P, and 91.7% for COD were recorded. The data indicates a possibility for CWW bioremediation and biofuel production in significant quantity and quality in comparison to the current scenario of microalgae cultivation. [ABSTRACT FROM AUTHOR]