Enhancement of nutrient removal from swine wastewater digestate coupled to biogas purification by microalgae Scenedesmus spp.

This work investigated the effects of swine wastewater-derived biogas on microalgae biomass production and nutrient removal rates from piggery wastewater concomitantly with biogas filtration. Photobioreactors with dominant Scenedesmus spp. were prepared using non-sterile digestate and exposed to different photoperiods. In the presence of biogas and autotrophic conditions microalgae yield of 1.1 +/- 0.2 g L (1) (growth rate of 141.8 +/- 3.5 mg L (1) d (1)) was obtained leading to faster N-NH3 and P-PO43 assimilation rate of 21.2 +/- 1.2 and 3.5 +/- 2.5 mg L (1) d (1), respectively. H2S up to 3000 ppmv was not inhibitory and completely removed. Maximum CO2 assimilation of 219 +/- 4.8 mg L (1) d (1) was achieved. Biological consumption of CH4 up to 18% v/v was verified. O-2 up to 22% v/v was controlled by adding acetate to exacerbate oxygen demand by microorganisms. Microalgae-based wastewater treatment coupled to biogas purification accelerates nutrient removal concomitantly producing valuable biomass and biomethane. (C) 2015 Elsevier Ltd. All rights reserved.