Photoresist-Material Production Wastewater Treatment Project Status:
Wastewater type: Photoresist-material production wastewater
Technology: Electrochemical oxidation
Test scales: 10 L module and 50 L pilot module
Primary target: Chemical Oxygen Demand (COD)
Peak reported COD removal: 99.9%
1. TREATMENT CHALLENGE
Wastewater from photoresist-material production can contain a very high load of organic compounds and may require deep oxidation before discharge, reuse or downstream polishing.
The supplied test program evaluated electro-oxidation at two module scales. The COD concentrations in both tests were extremely high, providing a useful demonstration of electro oxidation treatment system under concentrated organic loading.
2. 10 L MODULE: COD REMOVAL PERFORMANCE
Initial COD: 64,710 mg/L
Final COD: 2,468 mg/L
Treatment time: 19.5 hours
Final reported COD removal: 96.19%
Selected points:
Time COD (mg/L) COD Removal
0 h 64,710 0%
4.5 h 20,170 68.8%
7.5 h 5,945 90.8%
10.5 h 4,212 93.5%
13.5 h 3,085 95.2%
19.5 h 2,468 96.19%
The 10 L energy series reports:
– 29.0 kWh per ton of wastewater at 7.5 h, with 0.49 kWh per kg COD.
– 40.29 kWh/t at 10.5 h, with 0.67 kWh/kg COD.
– 52.78 kWh/t at 13.5 h, with 0.86 kWh/kg COD.
– 73.2 kWh/t at 19.5 h, with 1.18 kWh/kg COD.
3. 10 L MODULE: ENGINEERING INTERPRETATION
Most of the COD removal occurred during the early-to-middle part of the treatment. The process exceeded 90% removal by 7.5 hours. Continued treatment reduced COD further, but the incremental removal became smaller while cumulative electricity consumption continued to increase.
This illustrates a common design trade-off in advanced oxidation: achieving the final few percentage points of COD removal can require substantially more treatment time and energy than the initial bulk removal. The economically preferred endpoint therefore depends on the required effluent target and whether another downstream process is available.
4. 50 L PILOT MODULE: COD REMOVAL PERFORMANCE
Initial COD: 58,690 mg/L
Final COD: 45 mg/L
Treatment time: 11.5 hours
Final reported COD removal: 99.9%
Selected points:
Time COD (mg/L) COD Removal
0 h 58,690 0%
1.5 h 13,840 76.4%
4.5 h 6,682 88.6%
7.5 h 3,160 94.6%
9.5 h 1,324 97.7%
10.5 h 376 99.4%
11.5 h 45 99.9%
The 50 L COD-removal test demonstrates extremely deep oxidation, reducing the residual COD to only 45 mg/L.
5. 50 L ENERGY TEST
The worksheet provides a separate 50 L electricity-consumption time series with sampling at 2.0, 4.5, 6.5, 8.5, 10.5, 12.5, 14.5, 16.5, 18.5, 20.5 and 22.5 hours.
Reported cumulative electricity consumption ranged from 30.25 kWh/t at 2 hours to 627.48 kWh/t at 22.5 hours. The reported specific electricity consumption ranged from 0.67 kWh/kg COD at 2 hours to 10.7 kWh/kg COD at 22.5 hours.
Important: The 50 L COD-removal series ends at 11.5 hours, whereas the 50 L energy series continues to 22.5 hours and uses a different sampling schedule. These should be treated as separate reported test series and should not be matched point-for-point without additional source information.
6. SCALE-UP OBSERVATION
The 50 L test reached a higher removal percentage in a shorter reported treatment time than the 10 L test: 99.9% in 11.5 hours versus 96.19% in 19.5 hours. This does not by itself prove that larger scale is inherently more efficient, because the worksheet does not provide enough information about current density, electrode area-to-volume ratio, hydrodynamics, initial wastewater composition or operating conditions to normalize the two experiments.
The result does, however, show that the electro oxidation process can achieve near-complete COD destruction in this wastewater under the tested pilot conditions.
7. INDUSTRIAL RELEVANCE
Possible applications include:
– Deep COD removal for difficult electronics/materials manufacturing wastewater.
– Pre-treatment of high-strength process wastewater before biological treatment.
– Final polishing for water reuse or stringent discharge requirements.
– Treatment of concentrated batch streams rather than dilution into a larger wastewater flow.
– Integration with recovery, membrane or evaporation processes.
8. ENGINEERING NOTES AND DATA LIMITATIONS
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The worksheet does not state pH, current/current density, electrode area, conductivity, chloride concentration, temperature, flow rate or detailed organic composition. Electricity data should be used only in the context of the reported tests until these operating variables are available.
9. KEY TAKEAWAY
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Niobium-based BDD electro-oxidation demonstrated very high COD destruction in photoresist-material production wastewater. The 10 L module reduced COD from 64,710 to 2,468 mg/L (96.19%), while the 50 L pilot COD test reduced COD from 58,690 to 45 mg/L (99.9%).
Source: User-supplied Worldia BDD wastewater test workbook, worksheet “光刻胶材料生产废水”.