Cross-Flow Filtration of Thermophilic Night-Soil Fermentation Suspension

Abstract

Thermophilic fermentation suspension of night-soil was filtrated in cross-flow mode using various thermostable membranes. The influence of operating conditions on flux was studied.
Limiting fluxes were obtained, and higher feed velocity and lower feed concentration resulted in a higher limiting flux. Difference in membrane module structure had a great effect on this limiting flux. The fluxes obtained with a flat membrane module (NTR-C70-F) were three to five times higher than those with a tubular one.
A gel layer was formed on the membrane surface. This layer had a large permeate resistance, and its specific filtration resistance was about 4.5×10¹⁵m·kg^-1 at 300 kPa.
In a long-term pilot test, the permeate flux was stable at about 1.6m³·m^-2·d^-1 at a feed velocity of 2m·s^-1.
It was also found that the permeate solution contained a great deal of NH₄-N and Cl^- compared with commercial hydroponic culture solution.