The membrane process had been applied for the advanced treatment of pig farm biogas slurry. As studied, this physical pretreatment, with low cost and high efficiency of the suspended solids removal and nutrient retention, is required to control membrane fouling. The combined process of paper filtration and ultrafiltration in a pilot scale was applied in the present study. The main objective was to explore and identify the feasibility of the new process for the pretreatment of the separation liquid of pig farm biogas slurry. A precision identification experiment of paper filtration and the multi-batch repetitive experiments of the combined process were designed. The results showed, at the identified paper filtration precision of 50μm and an operating pressure of 0.3 bar of the ultrafiltration process, that the flux rate at the stable stage of the multi-batch operation was around 295.00 L/h. The combined process achieved an overall processing rate of 345.41 ± 18.81 L/h and a volume permeation proportion of 82.45% ± 0.85%. The TSS was removed by 95.71%, but total nitrogen (TN) and ammonia nitrogen (NH₃-N) were retained by 76.29% ± 2.04% and 73.74% ± 2.10%, respectively. Comprehensively, the requirement for the pretreatment was obtained.
Keywords: biogas slurry; paper filtration; the combined process; ultrafiltration.