The waste is sorted by type e.g. if it contains heavy metal salts versus nasty organics. Quite a lot of this is recycled. Heavy metal concentrates are cheaper t

The waste is sorted by type e.g. if it contains heavy metal salts versus nasty organics. Quite a lot of this is recycled. Heavy metal concentrates are cheaper to refine than fresh ore; quite a few labs sell their waste to companies that extract the underlying metals. Nasty organics are often incinerated, which renders them harmless. There is an entire industry around optimally managing chem lab waste. It doesn’t go to the landfill unless it has been thoroughly processed for both value and toxicity. Industrial chemistry is a low-margin business, companies extract every bit of value from their waste stream that they can.