A simplified process of swine slurry treatment by primary filtration and Haematococcus pluvialis culture to produce low cost astaxanthin

•Swine slurry after filtration can act as substrate for Haematococcuspluvialis.•Filtration removed a large amount of N-NH4 and enrich slurry of N-NO3 with benefit for algae.•Algae growth led to a drastic reduction in macro and micronutrients concentration in the slurry.•Haematococcus pluvialis accumulated astaxanthin in nutrient-deprived conditions.•Low-cost filtration and microalgae growth allow the production of added value products.

A simplified process for treating swine slurry through primary filtration and subsequent depuration of the filtrate with the astaxanthin-rich microalga Haematococcus pluvialis is proposed. The first step comprises a low-cost filtration system capable of reducing 66% of ammonia, 7% of phosphorus and 19% of chemical oxygen demand, and increasing the concentration of nitrate, being this useful for subsequent growth of the algae. The second step comprises the discontinuous cultivation of H. pluvialis in diluted filtered slurry. The optimal dilution was researched by testing undiluted and 2, 4 and 8-fold diluted filtrate. This step led to a drastic reduction in macro and micronutrients concentration (up to 99% for NO3-N and NH4-N, 98% for TP and 26% for chemical oxygen demand). After H. pluvialis growth the accumulation of astaxanthin took place for 14 d in nutrient-deprived conditions: an astaxanthin accumulation of 1.27% on a dry weight basis was measured. These results indicate the possibility to couple low-cost filtration and microalgae production to recover nutrients from swine wastewaters and to add value by producing valuable astaxanthin for the feed market or for an on-farm utilization as feed addictive.