Avaliação do desempenho de lagoas de alta taxa no tratamento de esgoto pré-desinfectado submetidas a diferentes níveis de radiação solar

• Autor(a) principal: Santiago, Aníbal da Fonseca
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/836
• topic: Lagoa de alta taxa; Tratamento simplificado de esgoto; Produção de biomassa algal; High rate algal ponds; Simplified wastewater treatment; Algal biomass production; CNPQ::ENGENHARIAS::ENGENHARIA SANITARIA

This study addresses the theme of high rate algal ponds (HRAP), a simplified system for wastewater treatment and algal biomass production. Among other purposes, such biomass can be used for bioenergy generation. The assessment of the system s performance focused on the effects of solar radiation and of different loads of heterotrophic bacteria prior to the HRAP. Solar radiation is known to be the primary source of energy for this system. Differently from other stabilization ponds, the HRAP is shallow and presents movement of the liquid mass, thus the intensity at which radiation affects its performance is amplified. Shading screens were used to provide the different radiation levels. The possibility of an ultraviolet (UV) pre-disinfection system was assessed in order to verify if decreasing of bacteria load prior to the HRAP and minimizing competition between such organisms and the microalgae would allow greater photosynthetic productivity. The HRAP was also assessed as post-treatment of an Upflow Anaerobic Sludge Blanket (UASB) reactor, which is widely used in developing countries since it is a cheap and easy operation option. The experiment consisted of 12 pilot scale HRAPs in parallel and was monitored over 10 months. The results showed that under average photosynthetically active radiation levels, there were higher DO production and diurnal pH variation, although there was no productivity increase in terms of volatile solids. The HRAPs under maximum shading (78%) did not present severe limitation regarding removals of organic matter, nutrients and Escherichia coli. The HRAPs which received pre-disinfected effluent presented higher DO production and pH variation during the day, indicating that such combination provided for more photosynthetic activity. Moreover, these units presented higher percentage of chlorophyll a in the biomass, which possibly accounts for the higher proportion of algae/bacteria. However, the capacity of removing organic matter and nutrients remained unaltered, whereas E. coli removal was lower for the HRAPs which received pre-disinfected effluent. The HRAP system presented satisfactory capacity for the post-treatment of UASB reactor effluent. The applicability of such combination must take into account the need of using of the biomass produced in the HRAP.