Garment wastewater mainly originates from washing, dyeing, and finishing processes in garment manufacturing. Its water quality typically exhibits the following characteristics:
1. High organic matter concentration: Contains large amounts of fiber debris, sizing agents (such as PVA), dyes, and auxiliaries, resulting in high COD (Chemical Oxygen Demand) and BOD (Biochemical Oxygen Demand).
2. Deep color: Wastewater discharged from the dyeing and printing stages often has a strong color, especially when synthetic dyes are used, making decolorization difficult.
3. Large pH fluctuations: Depending on the process, the pH may be strongly acidic (e.g., pickling) or strongly alkaline (e.g., alkali boiling), typically between 2 and 12.
4. High suspended solids content: Originates from fabric fibers, cotton lint, dust, etc., resulting in a significant SS (suspended solids) concentration.
5. High salt content: The dyeing and printing process uses large amounts of salts (such as sodium sulfate and table salt) to promote dyeing, leading to increased conductivity.
6. Toxicity and Bioinhibition: Some dyes, auxiliaries, or heavy metals (such as decomposition products of azo dyes) are toxic to microorganisms, affecting the efficiency of biological treatment.
These characteristics necessitate a comprehensive approach to garment wastewater treatment processes, combining physicochemical (e.g., coagulation and sedimentation), biological (e.g., A/O process, MBR), and advanced treatment (e.g., ozone oxidation, activated carbon adsorption) components.
