The pretreatment module of skid-mounted painting wastewater treatment equipment achieves efficient removal of paint sludge through a multi-stage physical separation and chemical demulsification process. Its core mechanism can be broken down into the following technical pathways:
Traditional pretreatment often relies on a single screen for interception, but skid-mounted equipment improves interception efficiency through "coarse and fine screen linkage." The coarse screen (5-10mm gap) first removes large-sized rags, metal shavings, and other impurities, preventing subsequent pump blockage; the fine screen (1-3mm gap) further intercepts tiny paint sludge particles, reducing subsequent reagent consumption. Some equipment uses a rotatable screen with an automatic reverse function to prevent screen blockage and ensure continuous operational stability.
For stable emulsions formed by paint mist in water, skid-mounted painting wastewater treatment equipment employs a combined "demulsifier + coagulant" dosing strategy. Demulsifiers (such as aluminum sulfate and ferric chloride) disrupt the emulsion system through charge neutralization, causing oil-water separation; coagulants (such as PAC and PAM) aggregate tiny paint sludge particles into large flocs through adsorption bridging. Some equipment integrates an automatic dosing system, adjusting the dosage of chemicals in real time based on the turbidity of the wastewater to avoid secondary pollution caused by overuse.
Air flotation separation is the core step in the pretreatment of skid-mounted equipment. Its principle is to generate 20-50μm microbubbles through a dissolved air system. These bubbles adhere to the surface of alum flocs, forming flocs with a density less than water, which float to the surface to form a scum layer. A scum scraper periodically scrapes the scum into a collection tank, achieving solid-liquid separation. Some equipment uses "vortex air flotation" technology, which uses a vortex pump to generate negative pressure to draw in air, eliminating the need for an additional compressed air system, reducing energy consumption while improving flotation efficiency.
To cope with the impact of high-concentration paint sludge, skid-mounted equipment is often equipped with a filter press or screw press for deep dewatering. The filter press uses mechanical pressure to reduce the moisture content of the scum from over 95% to 60%-70%, forming a stackable sludge cake; the screw press uses the squeezing force generated by the rotation of the screw shaft to achieve continuous dewatering, suitable for treating small-flow wastewater. The dehydrated paint sludge is treated as hazardous waste and disposed of by a professional organization to avoid environmental risks from indiscriminate discharge.
The modular design of the skid-mounted equipment allows for flexible adaptation to different treatment scenarios. For example, for water-based paint wastewater, the amount of demulsifier added can be reduced and the coagulant ratio optimized; for solvent-based paint wastewater, the dissolved air efficiency of the flotation system needs to be enhanced to handle more difficult-to-separate fine particles. Some equipment integrates an online monitoring system, providing real-time feedback on indicators such as SS (suspended solids) and COD (chemical oxygen demand), providing data support for process adjustments.
The ease of maintenance of the pretreatment module directly affects the long-term operating efficiency of the equipment. The skid-mounted painting wastewater treatment equipment adopts designs such as quick-opening manholes and removable screens for easy regular cleaning of internal residual paint sludge; key components such as the dissolved air tank and release device of the flotation system are made of corrosion-resistant materials to extend their service life; the automatic backwashing system can clean the filter screen regularly to prevent clogging and subsequent reduction in treatment capacity.
Through the integration of the above technologies, the pretreatment module of skid-mounted painting wastewater treatment equipment can achieve a paint residue removal rate of over 90%, creating favorable conditions for subsequent biochemical treatment. Its compact and integrated design makes it particularly suitable for space-constrained paint shops or temporary work environments, making it an important technological direction in the field of industrial wastewater treatment.
