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The Industrial Technology Research Institute (ITRI) in Taiwan conducted laboratory assessments on phosphorus-containing aluminum etching wastewater from optoelectronic plants. Employing fluidized bed crystallization (FBC), ITRI was able to produce iron phosphate crystals that can be repurposed as valuable resources. This process was combined with an electrolytic recovery unit, which reduces the iron-containing sludge from the FBC process and recycles it back into the FBC for further crystallization, minimizing sludge waste. Under FBC treatment at a pH of approximately 7 and an Fe/P ratio of 1.1–1.25, the total phosphorus concentration in the effluent was reduced from around 200 mg/L to below 30 mg/L, with total iron concentration under 30 mg/L. Following coagulation and sedimentation, effluent phosphorus dropped below 10 mg/L, and iron levels were below 1 mg/L, achieving a phosphorus removal efficiency of 90％ and a crystallization rate of 85％.

The operation of fluidized bed crystallization (FBC) is relatively complex, as factors such as ferrous sulfate dosage, pH, upflow velocity, and reaction time all play a critical role in phosphorus removal efficiency. Due to variations in influent water quality, operators often find it challenging to make timely and accurate adjustments based solely on experience. To align with advancements in digital technology and artificial intelligence, this phosphorus recovery system incorporates smart control. Input parameters include influent phosphorus concentration, flow rate, ferrous sulfate concentration, dosing amount, pH, recycle flow rate, ORP, EC, temperature, effluent phosphorus concentration, and effluent iron concentration. The output parameters include effluent phosphorus concentration, effluent iron concentration, phosphorus removal rate, and crystallization efficiency. Through multi-parameter optimization, the system can directly control equipment such as the pH controller, ferrous sulfate dosing pumps, and recycle pump speed.

Author：羅英維,張倖偉,徐淑芳,古宏麒,黃博煜

★Article source: IWA ASPIRE 2025 Conference