Effective Treatment of Wastewater from Water-Based Inks: Methods and Best Practices

Water-based inks are commonly used in the production process of printing and packaging. However, the cleaning of equipment used with water-based inks produces a significant amount of wastewater. This wastewater contains various compounds, such as ink residues, starch, and surfactants, which require proper treatment before disposal. In this article, we will explore six key wastewater treatment methods that can efficiently handle wastewater from water-based ink processes, while also meeting environmental compliance standards.

1. Chemical Oxidation and Coagulation

The primary components of wastewater from water-based inks include the ink itself, starch, and surfactants. Chemical oxidation followed by coagulation is an effective method for treating this wastewater. Oxidizing agents such as potassium permanganate (KMnO?), hydrogen peroxide (H?O?), and sodium hypochlorite (NaClO) are used to decolorize the water.

In a trial using NaClO as the oxidizing agent (15g/L) and FCH3 as the coagulant (0.2g/L) at an adjusted pH of 8.5, the chemical oxygen demand (COD) removal rate reached 94%, while color removal achieved 100%. This process has proven to be highly effective in reducing pollutants and ensuring cleaner wastewater discharge.

2. Ultrafiltration Technology

Ultrafiltration is a membrane-based technique that removes particles and dissolved contaminants from wastewater. When wastewater is passed through three sets of ultrafiltration modules, the COD removal rate reaches 92%. The concentrate retains solid content up to 99g/L (approximately 10%), while the turbidity of the filtered water remains between 0.13 to 0.4 NTU.

While this method provides high COD removal rates, its effectiveness can vary based on the solubility of pollutants in the wastewater. Soluble contaminants can pass through the membranes, requiring additional treatment steps for complete removal.

3. Coagulation, Flotation, and Contact Oxidation

This combined treatment method is highly effective for wastewater that contains water-based ink, kitchen waste, and domestic sewage. After removing larger suspended solids, coagulation flotation is applied to separate liquids and solids. The treated wastewater is then mixed with kitchen and domestic sewage, where it undergoes anaerobic adjustment followed by secondary biological contact oxidation.

The result is a reduction in COD from as high as 182,000 mg/L to 67 mg/L, with color removal from 4000 times to less than 10 times. This method has proven effective, stable, and resilient to operational shocks.

4. Micro-Electrolysis with Iron Chips

In this method, raw wastewater is first treated with hydrochloric acid (HCl) to adjust the pH, followed by sedimentation pre-treatment. The COD levels drop from 6,000–8,000 mg/L to around 800–1,000 mg/L, and color intensity reduces significantly.

The water is then subjected to micro-electrolysis, which uses iron chips and coke to treat the wastewater. This process further reduces COD by 50% and color by 90%. By combining sedimentation pre-treatment with micro-electrolysis, the overall COD removal reaches 85%, and color removal exceeds 95%.

5. Chemical Coagulation

This traditional treatment method employs common coagulants such as FeSO?·7H?O, FeCl?·6H?O, and polyaluminum chloride (PAC) to coagulate the suspended particles. After selecting the optimal coagulant—FeCl?·6H?O (80 mg/L)—and adjusting the pH to 4.0, the addition of chitosan (0.8 mg/L) as an auxiliary coagulant achieves COD removal rates of 87% and color removal rates of 99%.

This process significantly reduces COD from 5,638 mg/L to 634.5 mg/L and color intensity from 240 times to below 10 times. The results show that chemical coagulation can be an efficient and cost-effective treatment method.

6. Coagulation, Flotation, Micro-Electrolysis, and Sequencing Batch Reactor (SBR) Technology

A combination of coagulation flotation, micro-electrolysis, and SBR technology provides one of the most comprehensive wastewater treatments. In this process, raw water with an initial COD of 2,805 mg/L undergoes sedimentation and oil separation, achieving a 20.4% COD reduction. After coagulation flotation, the COD removal reaches 74.6%, and further treatment with micro-electrolysis boosts the COD removal rate to 82.2%.

Finally, the wastewater is processed in a sequencing batch reactor (SBR), which further reduces the COD to 71.9 mg/L (97.4% removal) and lowers the color intensity by 98%. This multi-step approach ensures excellent removal rates and improves the biological treatability of the wastewater.

Conclusion

The proper treatment of wastewater from water-based ink processes is crucial for both environmental sustainability and regulatory compliance. The methods outlined above—ranging from chemical oxidation and ultrafiltration to advanced techniques like micro-electrolysis and SBR—offer effective solutions for different levels of wastewater contamination. By selecting the right treatment strategy, companies can significantly reduce pollutants in their effluent, improve water quality, and contribute to a cleaner, more sustainable production environment.

Given the complexity of wastewater treatment for water-based inks and the chemical knowledge required, it is often best to leave these matters to professionals. A reliable, stable wastewater treatment system specifically designed for ink waste can help you avoid potential issues and ensure that your operations comply with environmental regulations. By investing in the right technology, you not only protect your business but also contribute to a cleaner environment.