Comparison of Membrane Separation Effects on Treating Liquid Digestate from Large-scale Chicken Farm Biogas Engineering

Considering difficulty of treating large amounts of liquid digestate from large-scale chicken farm biogas engineering，pilot scale integrated membrane separation equipment was developed.The separation effect of membrane technology on the reduction of COD，ammonia nitrogen and nutrients in the liquid digestate was studied.Results showed that process combination of‘bag filter+ultrafiltration（UF）+nanofiltration（NF）+reverse osmosis（RO）’achieved the COD rejection rate of 96.5%，and the ammonia nitrogen rejection rate of 63.8%.Through process combination of‘bag filter+UF+two-stage RO’，COD in the final permeate was reduced to 66 mgL with COD rejection rate up to 99.2%，while ammonia nitrogen in the final permeate was reduced to 530 mgL with ammonia nitrogen rejection rate of 82.4%.Process of‘UF+two-stage RO’achieved better separation effect on chicken manure liquid digestate than‘UF+NF+RO’.Humic acid and amino acid in the liquid digestate was concentrated under the action of RO.RO concentrate could be further used for production of liquid fertilizer or for other development and utilization.