Integration of Microalgae Cultivation in a Biogas Production Process from Organic Municipal Solid Waste: From Laboratory to Pilot Scale

摘要

In this study, the feasibility of integrating microalgae cultivation in a biogas productionprocess that treats the organic fraction of municipal solid waste (OFMSW) was investigated.In particular, the biomass growth performances in the liquid fraction of the digestate, characterized byhigh ammonia concentrations and turbidity, were assessed together with the nutrient removalefficiency. Preliminary laboratory-scale experiments were first carried out in photobioreactorsoperating in a continuous mode (Continuous-flow Stirred-Tank Reactor, CSTR), to gain preliminarydata aimed at aiding the subsequent scaling up to a pilot scale facility. An outdoor experimentalcampaign, operated from July to October 2019, was then performed in a pilot scale raceway pond(4.5 m2), located in Arzignano (VI), Italy, to assess the performances under real environmentalconditions. The results show that microalgae could grow well in this complex substrate, althoughdilution was necessary to enhance light penetration in the culture. In outdoor conditions, nitrificationby autotrophic bacteria appeared to be significant, while the photosynthetic nitrogen removal wasaround 12% with respect to the inlet. On the other hand, phosphorus was almost completely removedfrom the medium under all the conditions tested, and a biomass production between 2–7 g m?2 d?1was obtained.