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472 PROCEEDINGS OF INTERNATIONAL SCIENTIFIC CONFERENCE ON APPLIED BIOTECHNOLOGYfrom an ammonium production plant. The research was conducted for 1 year, with stable nitrogen treatment efficiency, and welldeveloped biomass within the gel-bead. The successful test has shown great potential for more widespread application of these technologies in the treatment of wastewater, especially wastewater with high ammonium concentrations, and environments with many unfavorable factors for microorganisms. Xiaofan Zhang [2] summarized the outstanding advantages of immobilization technology including: (1) can maintain high density and activity of microorganisms in the treatment tank, thereby improving the efficiency of pollutant treatment; (2) microbial biomass increases less, thereby reducing the pressure on excess sludge treatment; (3) granular biomass significantly improves the sedimentation and dewatering process after treatment, (4) can be applied to many types of industrial wastewater; (5) Biomass immobilization helps microorganisms develop stably and resist toxins and adverse environmental conditions.Beside, there are currently several different materials used to fabricate hydrogel to immobilize microorganisms for wastewater treatment such as polyvinyl alcohol (PVA), alginate (SA), PEG, polyurethane (PU), etc. [4], of which PVA and SA are commonly used. PVA is a material with low toxicity, high biocompatibility, good substrate adsorption, and low production cost [5,6]. However, pure PVA gel has poor mechanical properties. Therefore, their application and development are limited to long-term applications. Recently, the method of adding nano-sized fillers to the composition of bio-immobilization gel beads is considered an effective way to solve this problem [7]. Among them, graphene oxide (GO) is a potential material for fillers due to its good mechanical properties, super biocompatibility, and large specific surface area. Therefore, the study %u201cImmobilization of activated sludge by a biomaterial based on PVA/SA/Graphene oxide for application in