IN THE FIELD
Recycling and reuse of water resources from industrial wastewater in Taiwan
By Wan-Ju Wei , assistant chief engineer, CTCI Corporation
petrochemicals. Before the construction of water reclamation plant (WRP), different kinds of membrane module pilot tests were carried out, including submerged MBR (S-MBR) of various brands, and pressurised MBR (P-MBR). RO and EDR were also tested. Eventually, S-MBR and RO were chosen as they fit better with the wastewater characteristics and the available construction space of this plant. Originally, after oil removal, the petrochemical wastewater would be discharged through the traditional activated sludge biological treatment process followed by sedimentation and sand filtration units. As this was the first time that the MBR+RO treatment process was introduced for wastewater reclamation in this petrochemical plant, the owner retained the original wastewater treatment facility, and only intercepted 6,000m 3 /day of oil-removed wastewater for the MBR+RO treatment process, with the rest of the wastewater treated and discharged. After the performance test, this WRP can generate a capacity of more than 3,900m 3 /day reclaimed water. Through the MBR+RO treatment process, the amount of organic pollutant chemical oxygen demand (COD) can be lowered from about 300mg/L to 30mg/L by MBR unit, with the rest being almost completed removed through RO unit. Moreover, the total dissolved solids (TDS) in the raw wastewater can be processed to less than 15mg/L, down from roughly 2,000mg/L. With the reclaimed water as an alternative to freshwater, the owner addressed the water shortage
Although Taiwan has an average annual rainfall of 2,515mm — which is 2.5 times of the global average — it remains one of the countries facing water scarcity due to uneven rainfall during wet and dry seasons, and the rough terrain that makes it difficult to collect rainwater. In order to solve water shortage in Taiwan, a national water resources management master plan was approved in August 2021 to serve as a blueprint for future infrastructure construction and the management of the nation’s water supply. The master plan centres around the promotion of three major initiatives that will bolster each region’s water supply capabilities to increase water reuse and recycling, and strengthen the management and resilience of the nation’s water supply. A goal to reduce water usage is to increase the reclamation rate of industrial wastewater from 70-80% by 2031.
Over the past 10 years, CTCI has carried out industrial wastewater reclamation using membrane bioreactors (MBRs) or electrodialysis reversal (EDR) combined with reverse osmosis (RO) technology for wastewater reclamation in refineries and petrochemical plants. CTCI also used biological treatment, physicochemical softening, and membrane technologies to treat effluents in Taiwan’s science and industrial park to produce higher-quality reclaimed water for semiconductor industrial use. The reclaimed industrial water not only meets the government’s goal of stable water supply and the development of reclaimed water sources, but also enables factories to maintain stable operation. Firstly, a petrochemical plant in southern Taiwan mainly produces olefins and aromatic hydrocarbon
Flow chart of the wastewater
reclamation system in a petrochemical plant producing olefins and aromatic hydrocarbons (Image: CTCI Taiwan)
32 Water & Wastewater Asia | September-October 2024
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