Part B: Sludge sewage pre-treatment and codigestion Technical Note 5 – Anaerobic co-digestion of domestic sewage and microalgal biomass with and without solar thermal pre-treatment

Abstract

Sewage treatment plants have been investigated in order to identify sustainable options for managing the by-products. Due to the widespread use of upflow anaerobic sludge blanket reactors (UASB) for the treatment of sewage in Brazil, one of these solutions would be the use of a high rate algal pond as a post-treatment for this effluent. In addition to being efficient in removing pollutants, the microalgal biomass produced can be introduced in the UASB reactor, being co-digested with raw sewage. This practice would increase methane production at UASB. However, little is known about the co-digestion of microalgae and raw sewage in these reactors. This technical note (TN) aims to report the most important aspects of this practice, as well as to clarify the weaknesses and potentialities for future full-scale implementation. This TN also proposes a sustainable way, based on solar radiation, for the thermal treatment of microalgae. Promising results show a 35% to 40% increase in methane production in UASB with microalgae co-digestion with and without pre-treatment, respectively, compared to a control reactor without co-digestion.