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Paint Spray Booth Wastewater Treatment And Sludge Dewatering System Process Description

Paint Sludge wastewater is from assembly line painting operations typically in metal finishing operations for appliances, sporting goods, outboard motors motorcycles, furniture.

Paint sludge is generated in facilities that use a water curtain to catch paint overspray. The parts hang on a conveyor that moves in front of the water curtain. As the painter sprays the parts, the overspray is caught in the water curtain behind the parts. The wastewater contains paint sludge and particles that must be removed prior to discharge to sewer.

Wastewater treatment of paint sludge requires pH adjustment while a de-tackifying chemical is added. The paint sludge and chips will then settle rapidly.

The typical method to treat spray booth paint sludge wastewater is as follows:

Stage 1 De-tackifying/pH adjustment:
pH is controlled to ~8 with caustic using the pH controller. A de-tackifying agent is added to prevent the sludge from sticking to pipes, clarifier plates etc. The pH adjustment also ensures effluent pH compliance.

Clarifier, Inclined Plate:
The wastewater is introduced into the clarifier where the settling particles land on the inclined plates and are directed downward and into the sludge chamber. The clarified treated water then exits the top of the clarifier and flows downstream to sewer or further treatment if necessary.

Clarifier Sludge Handling:
The resulting clarifier waste sludge is periodically removed from the clarifier at a slow rate and sent to the sludge holding tank where it further thickens and accumulates a batch for disposal or processing in a filter press. The sludge is mixed and conditioned with a filter aid such as DE to improve porosity and filterability which will improve cake dryness and prevent premature blinding of the filter cloths.

Sludge Dewatering:
The thickened clarifier sludge is allowed to accumulate sufficiently to provide a full batch for the Filter Press. The filter press is prepared with a precoat of DE used to prevent blinding of the filter cloths. . Once the filter press is pre-coated with DE the sludge is pumped until the filter press is full. The filter press is then emptied of the “cake” which is a semi solid of approximately 20-60 % solids. Sludge cake is high in paint solids and should be disposed of according to environmental regulations.


  • Appliance makers

  • Automotive, truck, bus, motorcycle

  • Car, truck and bus body parts makers

  • Sport equipment makers (outboard engines, snowmobiles, etc)

  • Aerospace – Air Craft

  • Furniture