2.7.4 Wastewater Treatment Process
Wastewater generated in the PWB production processes is treated at each step;
however, wastewater generated from similar processes is pooled to a tank for
treatment. The wastewater treatment methods employed in this subcategory are
primarily for water reuse in the plant. The pH of the wastewater is often adjusted
in tanks before discharge or recycles. The use of reactive chemicals for rinsing and
multiple drag-out baths will further reduce the pollution level of the wastewater
emanating from the plant. The combined electrolysis and chemical precipitation is a
very good process of removing and recovering lead and tin from the waste stream.
Sludge dewatering and sludge processing for the recovery of metal are part of the
processes applicable to the wastewater treatment.
2.7.5 Treatment Technologies and Cost
All the treatment technologies identified under this subcategory are classified both as
best practicable control treatment (BPT) and best available technologies (BAT). The
costs involving best practicable control treatment (BPT) and best available technologies (BAT) are stated in Table 4.38.
Table 4.36 Printed wiring board pollution outputs
Process
Air
emissions
Process wastes (liquids/
wastewaters)
Other wastes (solids/rcra)
Board
preparation
Particulates,
acid fumes,
and VOCs
Spent acids and spent alkaline
solutions
Sludge and scrap board
material
Electroless
plating
Spent electroless copper baths,
spent catalyst solutions
Waste rinse water and sludges
from wastewater treatment
Imaging
Organic
vapors and
acid fumes
Spent developing solution ,
spent resist material, spent acid
solutions, and aqueous metals
F001-5, depending on concentration and mixture of solvents. Sludges from
wastewater treatment
Electroplating Acid fumes,
ammonia
fumes, and
VOCs
D008 (lead), D002, D003,
spent etchants, spent acid solutions, spent developing solutions, spent plating baths
F006, F007, and F008
Solder
coating
VOCs and
CFCs
PWD assembly and
soldering
VOCs and
CFCs
Metals (nickel, silver, and copper), D008 (lead), flux residue,
spent deionized water; spent
solvents
Solder dross, scrap boards,
filters, gloves, rags, wastewater treatment sludge
168
O. S. Amuda et al.
Wastewater generated in the PWB production processes is treated at each step;
however, wastewater generated from similar processes is pooled to a tank for
treatment. The wastewater treatment methods employed in this subcategory are
primarily for water reuse in the plant. The pH of the wastewater is often adjusted
in tanks before discharge or recycles. The use of reactive chemicals for rinsing and
multiple drag-out baths will further reduce the pollution level of the wastewater
emanating from the plant. The combined electrolysis and chemical precipitation is a
very good process of removing and recovering lead and tin from the waste stream.
Sludge dewatering and sludge processing for the recovery of metal are part of the
processes applicable to the wastewater treatment.
2.7.5 Treatment Technologies and Cost
All the treatment technologies identified under this subcategory are classified both as
best practicable control treatment (BPT) and best available technologies (BAT). The
costs involving best practicable control treatment (BPT) and best available technologies (BAT) are stated in Table 4.38.
Table 4.36 Printed wiring board pollution outputs
Process
Air
emissions
Process wastes (liquids/
wastewaters)
Other wastes (solids/rcra)
Board
preparation
Particulates,
acid fumes,
and VOCs
Spent acids and spent alkaline
solutions
Sludge and scrap board
material
Electroless
plating
Spent electroless copper baths,
spent catalyst solutions
Waste rinse water and sludges
from wastewater treatment
Imaging
Organic
vapors and
acid fumes
Spent developing solution ,
spent resist material, spent acid
solutions, and aqueous metals
F001-5, depending on concentration and mixture of solvents. Sludges from
wastewater treatment
Electroplating Acid fumes,
ammonia
fumes, and
VOCs
D008 (lead), D002, D003,
spent etchants, spent acid solutions, spent developing solutions, spent plating baths
F006, F007, and F008
Solder
coating
VOCs and
CFCs
PWD assembly and
soldering
VOCs and
CFCs
Metals (nickel, silver, and copper), D008 (lead), flux residue,
spent deionized water; spent
solvents
Solder dross, scrap boards,
filters, gloves, rags, wastewater treatment sludge
168
O. S. Amuda et al.