Ozonation as Pretreatment of Digested Swine Manure Prior to Microalgae Culture
César Ruiz Palomar,
Alfonso García Álvaro,
Daphne Hermosilla,
Antonio Gascó,
Raúl Muñoz,
Ignacio de Godos
Affiliations
César Ruiz Palomar
Department of Chemical Engineering and Environmental Technology, School of Agrarian Engineering, Campus Duques de Soria, University of Valladolid, 42005 Soria, Spain
Alfonso García Álvaro
Department of Chemical Engineering and Environmental Technology, School of Agrarian Engineering, Campus Duques de Soria, University of Valladolid, 42005 Soria, Spain
Daphne Hermosilla
Department of Forest and Environmental Engineering and Management, Universidad Politécnica de Madrid, José Antonio Novais 10, 28040 Madrid, Spain
Antonio Gascó
Department of Forest and Environmental Engineering and Management, Universidad Politécnica de Madrid, José Antonio Novais 10, 28040 Madrid, Spain
Raúl Muñoz
Institute for Sustainable Processes, University of Valladolid, 47011 Valladolid, Spain
Ignacio de Godos
Department of Chemical Engineering and Environmental Technology, School of Agrarian Engineering, Campus Duques de Soria, University of Valladolid, 42005 Soria, Spain
Anaerobic digestion of animal manure generates biogas and removes biodegradable organic matter, while most of the nitrogen and phosphorous remains at very high levels after the process. A subsequent microalgae culture in the digestate provides nutrient uptake at very low operational and installation costs. However, the dark color of manure digestate prevents light penetration, reducing the rates of algae growth. Ozonation was researched as a strategy for color removal followed by microalgae culture. Although similar biomass production was achieved in treated and untreated digestates (1.09 vs. 0.99 g L−1), the positive effect of ozonation was evidenced by the significantly higher rates of photosynthetically produced oxygen: 0.804 and 0.18 mg O2 mg−1 TSS min−1, respectively, in ozonated and untreated digestates, revealing a four times higher rate of algae activity. However, this considerable higher activity was not correlated with better performance in nutrient removal since the microalgae treatment was assayed at a considerably reduced scale with a high ratio of illumination per volume. An operational costs analysis revealed that ozonation could be competitive against other strategies of color reduction such as dilution or coagulation/flocculation processes.
