Valorisation of liquid digestate from organic waste: stripping, thermophilic anaerobic digestion and membrane technologies for resources recovery, and emerging contaminants assessment

An innovative valorisation train to recover energy, nutrients and water from the liquid fraction of the digestate of the organic fraction of municipal solid waste ( ld -OFMSW) was evaluated at bench-scale. The process consisted of ammonia stripping, a thermophilic anaerobic membrane bioreactor (tAnMBR) for biogas production, membrane contactors for residual ammonia recovery from tAnMBR permeate, and regenerated reverse osmosis (RO) membranes for water reclamation. Direct feeding of raw ld -OFMSW into the tAnMBR led to ammonia inhibition, which was mitigated by a stripping pre-treatment at 55 °C, reducing ammonia nitrogen from 3.80 to 0.82 g L -1 and allowing a COD removal > 80 % by the tAnMBR at a high loading rate (3.1 kg COD m −3 d -1 ). Membrane contactors recovered nearly 100 % of the residual ammonium, and RO produced high water quality. High removal rates of antibiotics, pesticides and hormones were achieved. The process combination proved to be a promising approach for ld -OFMSW valorisation.