[China Packaging Network News] During the production and application of water-based inks, a significant amount of wastewater is generated due to equipment cleaning. The frequent color changes in these inks result in complex chemical compositions in the wastewater, characterized by high COD (Chemical Oxygen Demand), high chroma, and poor biodegradability. If released into water bodies, this wastewater can cause severe environmental pollution. Therefore, the treatment of such wastewater is crucial, and the methods used are closely related to the type and properties of the aqueous inks.
Currently, research and practical applications in treating water-based ink wastewater mainly focus on pretreatment techniques combined with biological processes. These include chemical coagulation, electrolysis, coagulation flotation, coagulation flotation-microelectrolysis, and chemical oxidation-coagulation. Among these, the electrolytic method has shown promising results, especially in domestic applications, offering several advantages that make it a preferred choice for preliminary treatment.
Electrolysis is an effective technique that is adaptable to various types of wastewater. It operates at room temperature, requires low energy, and produces minimal secondary pollution. The process involves using iron as the anode and aluminum as the cathode, where the electrochemical reactions lead to the generation of hydroxyl radicals (OH·) that degrade organic pollutants into carbon dioxide, water, and simple compounds. Additionally, the electrolysis process facilitates air flotation, which helps in removing suspended solids from the wastewater.
The mechanism of electrolytic decontamination includes oxidation, reduction, coagulation, and flotation. Oxidation occurs through both direct and indirect pathways, while reduction takes place via electron transfer on the cathode. Coagulation happens as metal ions form hydroxides that adsorb pollutants, and flotation is aided by gas bubbles that carry contaminants to the surface.
Another commonly used method is the UASB (Upflow Anaerobic Sludge Blanket) process, which combines anaerobic filtration with activated sludge technology. This process converts organic pollutants into biogas, a renewable energy source. The UASB reactor is known for its efficiency, low cost, and ease of operation, making it widely adopted in wastewater treatment.
Air flotation is another method that uses tiny air bubbles to lift suspended particles to the surface, allowing them to be removed. While effective, it has limitations, such as equipment complexity and corrosion issues in oily wastewater.
Coagulation involves adding chemicals to destabilize colloidal particles, causing them to aggregate and settle. This method is often used as a pretreatment step and is effective for treating various types of wastewater.
Biological contact oxidation is a popular technique that utilizes biofilms to break down organic matter. Microorganisms attached to solid media degrade pollutants, leading to efficient wastewater purification. This method offers high volumetric loading, no sludge recirculation, and strong adaptability to varying conditions.
Membrane Bioreactors (MBRs) combine biological treatment with membrane separation, providing high-efficiency wastewater treatment. MBRs are compact, easy to operate, and produce high-quality effluent. They have gained popularity in recent years, especially in treating complex industrial wastewaters.
Overall, the combination of these methods ensures effective and sustainable wastewater treatment, addressing the challenges posed by water-based ink waste.
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