Microalgae treatment removes nutrients and reduces ecotoxicity of diluted piggery digestate.
Liquid digestate is considered as an important by-product of anaerobic digestion of agriculture wastes. Currently, it is very often directly spread on local agricultural land. Yet recently concerns on its environmental risk of this processing has begun to rise. On the other hand, investigations on the effectiveness of microalgae for wastewater treatment have started to consider also this complex matrix. In this study, we cultured the green alga Chlorella vulgaris in diluted digestate coming from the anaerobic digestion of pig slurry and corn, with the aim to significantly reduce its toxicity and its very high nutrient concentration. For this purpose, a battery of toxicity tests composed of four acute and two chronic bioassays was applied after the alga cultivation. Results were compared with those obtained in the initial characterization of the digestate. Results show that highly diluted piggery digestate can be a suitable medium for culturing microalgae, as we obtained a high removal efficiency (>90%) for ammonia, total nitrogen and phosphate, though after a few days phosphorus limitation occurred. Toxicity was significantly reduced for all the organisms tested. Possible solutions for optimizing this approach avoiding high dilution rates are discussed.
Laboratory of Aquatic Ecosystems, Department of Life Sciences and System Biology, University of Turin, via Accademia Albertina, 13, 10123 Turin, Italy.
Marta
M
Franchino
Mycotheca Universitatis Taurinensis, Department of Life Sciences and System Biology, University of Turin, viale Mattioli, 25, 10125 Turin, Italy.
Valeria
V
Tigini
Mycotheca Universitatis Taurinensis, Department of Life Sciences and System Biology, University of Turin, viale Mattioli, 25, 10125 Turin, Italy.
Giovanna Cristina
GC
Varese
Pelagosphera s.c.r.l., via Umberto Cosmo, 17/bis, 10131 Turin, Italy.
Rocco
R
Mussat Sartor
Laboratory of Aquatic Ecosystems, Department of Life Sciences and System Biology, University of Turin, via Accademia Albertina, 13, 10123 Turin, Italy. Electronic address: francesca.bona@unito.it.
Francesca
F
Bona
D000818:Animals; D001673:Biodegradation, Environmental; D048408:Chlorella vulgaris / Q000254:growth & development / Q000378:metabolism; D008372:Manure / Q000032:analysis*; D058086:Microalgae / Q000254:growth & development* / Q000378:metabolism*; D018570:Risk Assessment; D034421:Sus scrofa; D018675:Toxicity Tests; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000032:analysis*
D008372:Manure; D062065:Wastewater
Algal productivity; Ammonia toxicity; Chlorella vulgaris; Ecotoxicology; Fertilisers; Removal efficiency