  The aim of this study was to assess the potential environmental impacts
associated with high rate algal ponds (HRAP) systems for wastewater treatment
and resource recovery in small communities. To this aim, a Life Cycle
Assessment (LCA) and an economic assessment were carried out evaluating two
alternatives: i) a HRAPs system for wastewater treatment where microalgal
biomass is valorised for energy recovery (biogas production); ii) a HRAPs
system for wastewater treatment where microalgal biomass is reused for
nutrients recovery (biofertiliser production). Additionally, both alternatives
were compared to a typical small-sized activated sludge system. The results
showed that HRAPs system coupled with biogas production appeared to be more
environmentally friendly than HRAPs system coupled with biofertiliser
production in the climate change, ozone layer depletion, photochemical oxidant
formation, and fossil depletion impact categories. Different climatic
conditions have strongly influenced the results obtained in the eutrophication
and metal depletion impact categories, with the HRAPs system located where warm
temperatures and high solar radiation are predominant showing lower impact. In
terms of costs, HRAPs systems seemed to be more economically feasible when
combined with biofertiliser production instead of biogas.
