| 摘要: | 台灣雖雨量充沛，但受限於地形高聳及河川坡陡流急，約七成雨水直接入海，導致蓄水效能不足。聯合國因此將台灣列為全球第18 缺水國。隨著環境保護需求日益提升，國內產業逐步推動廢水回收再利用，並以廢水零排放(Zero Liquid Discharge, ZLD)為目標。零排放相關設備的技術發展與操作維護，不僅攸關企業環保績效，亦為推動循環經濟之核心基礎。
本研究以某光電廠A 之廢水處理系統為案例，藉由導入蒸發及乾燥單元以實現ZLD。由於高溫處理方式能耗龐大，首先以逆滲透與倒極式電透析濃縮廢水，以提升水回收率並降低後端處理負荷。所得高鹽濃縮液進入一次濃縮槽，再經機械式蒸氣再壓縮系統(Mechanical Vapor Recompression, MVR)與滾筒式常壓乾燥機進行蒸發與乾燥，最終產生含水率低於20%的固體鹽類，並由合格處理業者進行後續處置。實廠數據顯示，MVR 每年處理約131,400 m³廢水，柴油成本約13,140,000 元，計算單位處理成本100 元/m³；而滾筒式常壓乾燥機每年僅處理8,760 m³廢水，卻需32,412,000 元柴油費用，單位成本高達3,700 元/m³，顯示其為系統能耗主要來源。
為改善滾筒式常壓乾燥單元之高能耗，本研究採用抽真空以降低廢水沸點，並優化真空度與操作條件後導入實廠。結果顯示，在相同處理水量下，單位成本降至1,863 元/m³，較原系統降低49.6%；年柴油消耗量減少321,756 L，相當於約850 公噸CO₂排放削減(依據環保署柴油燃燒排放係數2.64 kg CO₂/L 計算)。此外，蒸餾過程產生之冷凝水具回收再利用潛能，可進一步提升整體系統效益。
綜合而言，本研究驗證以真空乾燥取代常壓乾燥，能顯著降低能耗與碳排放，兼具經濟性與環境效益，對台灣產業推動廢水零排放具重要參考價值。;Although Taiwan receives abundant rainfall, its steep terrain and rapid river flows cause approximately 70% of precipitation to discharge directly into the ocean, resulting in limited water storage capacity. Consequently, the United Nations has ranked Taiwan as the 18th most water-scarce country in the world. With increasing demands for environmental protection,domestic industries have progressively promoted wastewater reclamation and reuse, targeting Zero Liquid Discharge (ZLD) as a key objective. The technological development, operation,and maintenance of ZLD-related facilities are not only crucial to corporate environmental performance but also constitute a core foundation for advancing the circular economy.
This study investigates the wastewater treatment system of a photovoltaic manufacturing plant (Plant A) as a case study, in which ZLD is achieved through the integration of evaporation and drying units. Given the high energy consumption associated with high-temperature treatment processes, reverse osmosis (RO) and electrodialysis reversal (EDR) were first applied to concentrate the wastewater, thereby increasing water recovery and reducing the load on
downstream processes. The resulting high-salinity concentrate was fed into a primary concentration tank and subsequently treated by a Mechanical Vapor Recompression (MVR) system and an atmospheric rotary drum dryer for evaporation and drying. Ultimately, solid salts with a moisture content below 20% were produced and disposed of by certified waste treatment
contractors. Full-scale operational data indicate that the MVR system treats approximately 131,400 m³ of wastewater annually, with a diesel cost of about NT$13,140,000 corresponding to a unit treatment cost of NT$100/m³. In contrast, the atmospheric rotary drum dryer processes
only 8,760 m³ per year yet incurs a diesel cost of NT$32,412,000 resulting in a unit cost as high as NT$3,700/m³, identifying it as the primary source of energy consumption in the system.
To address the excessive energy demand of the atmospheric rotary drum drying unit, this study introduced vacuum operation to reduce the boiling point of the wastewater and optimized the vacuum level and operating conditions prior to full-scale implementation. The results show that, under the same treatment capacity, the unit cost was reduced to NT$1,863/m³, representing a 49.6% reduction compared with the original system. Annual diesel consumption decreased by 321,756 L, equivalent to an estimated reduction of approximately 850 metric tons of CO₂ emissions (calculated using the Environmental Protection Administration diesel emission factor of 2.64 kg CO₂/L). In addition, the condensate generated during the distillation process exhibits
potential for recovery and reuse, further enhancing the overall system efficiency.
In summary, this study demonstrates that replacing atmospheric drying with vacuum drying can significantly reduce energy consumption and carbon emissions while providing both economic and environmental benefits. The findings offer valuable reference for Taiwanese industries seeking to implement wastewater zero liquid discharge strategies. |
