Recently, the 300 m³ double-membrane gas holder supplied for a paper mill wastewater treatment project in Vietnam was successfully installed. The gas holder is primarily used to collect and store biogas generated during the anaerobic treatment of papermaking wastewater. It features stable gas storage, constant-pressure output, excellent corrosion resistance, and reliable operational safety. Once commissioned, the system will effectively improve the efficiency of biogas collection and utilization, provide a stable gas supply for downstream applications such as power generation and boiler combustion, and help the paper mill reduce energy consumption, recover valuable resources from wastewater, and achieve greener, low-carbon production.