The use of water-based inks in corrugated packaging offers numerous environmental benefits. However, the wastewater generated during production and equipment cleaning presents a significant challenge. Proper wastewater treatment is crucial for maintaining regulatory compliance and environmental responsibility. This article explores various treatment methods and highlights the realities of wastewater disposal in the corrugated packaging industry.
1. Chemical Oxidation and Coagulation Process
Water-based ink wastewater contains pigments, starch, and surfactants. To remove contaminants efficiently, chemical oxidation combined with coagulation can be employed. Studies show that adding 15g/L of NaClO as an oxidizing agent, along with 0.2g/L of coagulant FCH3 and adjusting the pH to 8.5, can achieve a 94% COD removal rate and 100% color removal. This method is highly effective for breaking down organic pollutants and improving wastewater clarity.
2. Ultrafiltration Technology
Ultrafiltration (UF) is an advanced membrane separation technique that can effectively remove suspended solids and high molecular weight substances from wastewater. When wastewater passes through three UF membrane units:
- COD removal reaches 92%
- Concentrated liquid solids reach 99g/L (approximately 10%)
- Permeate turbidity is reduced to 0.13-0.4 NTU
However, ultrafiltration is not as effective for removing soluble contaminants, which must be treated with additional processes.
3. Combined Coagulation-Flotation and Bio-Oxidation Process
A combination of coagulation flotation and biological oxidation can treat wastewater efficiently by integrating different treatment stages:
- Initial flotation removes large suspended solids
- Coagulation (using polyaluminum chloride and caustic soda) reduces COD by 47.6%
- Anaerobic conditioning followed by secondary biological oxidation further reduces COD levels to 67mg/L
This method is particularly suitable for wastewater treatment plants handling mixed industrial and domestic wastewater.
4. Iron-Based Micro-Electrolysis Process
The micro-electrolysis process involves treating wastewater with iron filings and hydrochloric acid to achieve 85% COD reduction and 95% color removal. The optimal conditions for this process include:
- Adjusting pH to 4.0
- Adding 10% iron filings and 16.67% activated carbon
- Allowing a reaction time of 60 minutes
This method is effective for pre-treatment, reducing organic load before secondary treatment.
5. Chemical Coagulation Treatment
Using coagulants such as FeCl3·6H2O combined with chitosan as a flocculant, this method can achieve:
- 87% COD removal (from 5638 mg/L to 634 mg/L)
- 99% color reduction (from 240 times to below 10 times)
The process is cost-effective and easy to implement, making it a viable option for small- and medium-sized packaging plants.
6. Integrated Coagulation-Flotation, Micro-Electrolysis, and SBR Treatment
For heavily polluted wastewater (COD > 2800 mg/L, color 1500+), a multi-stage approach is necessary. A combination of coagulation flotation, micro-electrolysis, and sequencing batch reactor (SBR) treatment can achieve:
- 74.6% COD reduction through coagulation flotation
- 28.6% additional COD removal via micro-electrolysis
- 82.2% final COD removal with SBR treatment
After treatment, final effluent COD levels reach 71.9 mg/L, meeting environmental discharge standards.
