Case Study 03
High-Color Papermaking Wastewater Decolorization
Challenge
A paper mill producing dyed paper products faced difficulties treating highly colored wastewater generated by its dyeing and coating processes.
The wastewater contained residual dyes and organic compounds, resulting in high color intensity and elevated COD levels. Conventional inorganic coagulants alone did not provide sufficiently stable color removal, making it difficult to achieve the required pretreatment quality.
The customer needed a chemical treatment program that could effectively reduce wastewater color and organic pollution before subsequent treatment.
A chemical treatment program combining a composite water decoloring agent and polyacrylamide (PAM) was evaluated through laboratory jar testing.
Solution
Decolorization
A composite water decoloring agent was added at a reported dosage of approximately 1,666 mg/L to promote color removal and destabilize color-related impurities.
pH Adjustment
The pH was adjusted from 6.8 to a target range of 7–8 to support the treatment process.
Flocculation
PAM was added at 5–15 mg/L to promote floc formation and improve solid-liquid separation.
Settling
The treated sample was allowed to settle. Clear separation between the flocs and treated water was observed within approximately 5–10 minutes.
Results
Laboratory jar testing reported the following results:
COLOR REDUCTION
99.4%
From 10,000 to 60 dilution times
COD REDUCTION
73.3%
3,000 → 800 mg/L
FINAL pH
7.5
Adjusted from an initial 6.8
SETTLING TIME
5–10 min
Clear floc separation observed