The valorization of biogas slurry with a pilot dual stage reverse osmosis membrane process

Biogas slurry is an environmental pollution source if it is discharged without proper treatment. In this work, a membrane system is designed to concentrate, and hence to recover the nutrient in the biogas slurry. The effects of pre-treatment technology, pH, temperature, operating pressure and module types of the reverse osmosis unit were studied via analyzing the chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, conductivity in the permeate and retentate, and the volume concentration ratio. A dual stage reverse osmosis (RO) process is also applied to further enhance the performance, the concentration ratio reaches above 5 within 80 mins of operation, while the nutrient recovery and water recovery rates are 98% and 92.52%, respectively. The COD and ammonia nitrogen rejection rates are 99.41% and 99.11%, respectively; the quality of the permeate is in accordance with the national standard for water discharging. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.