Nutrient recovery from agricultural digestate by integrated ultrafiltration and reverse osmosis: effect of pretreatment strategies from laboratory to demonstrative scale

Agricultural digestate, a nutrient-rich by-product of biogas production, can provide valuable nutrients for fertilizers, but recovering them efficiently remains a challenge. This study compared different treatments to improve membrane filtration and nitrogen recovery from digestate. Adjusting its acidity to pH 4 produced the best results, helping liquid pass through the membranes and retaining more nitrogen in the final concentrated product. Tests at a demonstration plant confirmed these benefits under real operating conditions, supporting more sustainable nutrient recycling.