Water-based inks are widely used in printing industries, but their production and application generate wastewater due to equipment cleaning. The complex chemical composition of this wastewater is caused by the varying colors of the inks, which makes it challenging to treat. This type of wastewater typically has high COD (Chemical Oxygen Demand), high color intensity, and poor biodegradability. If released into water bodies, it can cause severe environmental pollution. Therefore, the treatment process must be carefully designed based on the characteristics of the ink used.
Among the various treatment methods, electrolysis has shown promising results. It has been studied and applied in many regions, including China, where it has proven effective for pretreatment before biochemical processes. Electrolysis offers several advantages: it generates hydroxyl radicals that help degrade organic pollutants into less harmful substances, reduces secondary pollution, enhances the biodegradability of wastewater, and is energy-efficient. Additionally, it can be used as a standalone or integrated method. For example, at Maoming Bantian Ink Co., Ltd., the combination of electrolysis and biological treatment successfully met discharge standards.
The electrolysis process involves using iron as an anode and aluminum as a cathode. Under electric current, the anode dissolves into Fe²⺠ions, while hydrogen gas forms at the cathode. These reactions create Fe(OH)₂, which acts as a coagulant, and new ecological hydrogen with strong reducing power that breaks down pollutants. The process includes oxidation, reduction, coagulation, and air flotation, making it highly effective.
Another key technology is the UASB (Up-flow Anaerobic Sludge Blanket) process. It combines anaerobic filtration and activated sludge methods, converting organic matter into biogas. Developed in the 1970s, it uses a three-phase separator to enhance efficiency. The formation of granular sludge significantly improved its performance, making it a popular choice for treating industrial wastewater.
Air flotation is another technique that removes suspended particles and oils by attaching them to air bubbles, which rise to the surface. While effective, it has limitations such as mechanical complexity and corrosion issues in oily wastewater.
Coagulation involves adding chemicals to destabilize colloidal particles, allowing them to settle. It’s commonly used in treating dyeing and oily wastewater, often as a pretreatment step.
Biological contact oxidation is a biofilm-based method where microorganisms attach to fillers, breaking down organic matter. It offers high efficiency, no sludge bulking, and good adaptability to fluctuating conditions.
Lastly, Membrane Bioreactors (MBRs) combine biological treatment with membrane filtration, offering high-quality effluent and compact design. They have gained popularity globally, especially for treating high-concentration and refractory wastewater. In China, MBRs are increasingly used for domestic and industrial applications, showing excellent performance in various scenarios.
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