Manufacturing in China does not mean a lack of environmental policy. The factory is ISO 14000 certified and subject to strict controls by local authorities (water agencies, ministries of the environment).
By definition, the printed circuit board industry is a polluting activity, we use all kinds of materials and products that require reprocessing.
For the record, we work with many substances (gold, tin, nickel, cobalt, copper, silver, zinc, tungsten, resins, inks, etc.) as many elements in liquid, pasty and solid form that can't be rejected in nature.
The factory is equipped with purification plants however, the treatment does not stop there, the sludge resulting from the purification are then incinerated while the liquid waste requires treatment by approved companies.
Soiled rags, pots and drums have their own drains.