Combined Membrane-Trickling Filter Wastewater Treatment System

Domestic wastewater is a main cause of water pollution. The idea of this research is to manage wastewater with an on-site treatment system. The proposed system is a modified trickling filter with a chitosan membrane coated matrix bed at the bottom, followed up by a conventional matrix bed. The system is called a combined membrane–trickling filter system. A φ0.5 m × H1.15 m unit was made as the studied model. The matrix materials were φ0.5 inch × 1 inch rigid PVC elements formed into a perforated wall of 35 openings each. The coated matrix was prepared by casting a chitosan solution synthesized from shrimp shells on the matrix as a thin membrane layer. The characteristics of the chitosan solution were as follows: viscosity 4200-4500 centipoise, degree of deacetylation 84.4%, and molecular weight 1.8×106 Dalton. Raw domestic wastewater was taken from the equalization tank of the Sipraya Water Quality Improvement Factory in Bangkok. Using a bar screen and rotating fine screen, large and fine objects were removed. It was found that the chitosan membrane acted as the initial organic layer for the microbial adherence and developed to become a biofilm for wastewater treatment. The developed biofilm in the lower portion of the tower provided better efficacy of the combined system. The culture balance between autotrophs and heterotrophs in the developed biofilm was controlled by raw wastewater characteristics