A specific example is the requirement to desalinate or deionise water prior to environmental discharge. That requirement introduces a waste stream (brine) which may be impossible to handle in practical terms. Technology is commercially available, at very high capital and operating cost (energy intensive) to concentrate brine to a moist solid. This is commonly called Zero Liquid Discharge (ZLD), but disposal or re-use routes for the concentrate are frequently non-existent, especially for operations that are not located on the coast where ocean disposal may be feasible. Storage of salt concentrate on-site becomes the only option, and that means creating an environmental legacy that needs to be managed in perpetuity, with ongoing risk of leakage.
A specialised Process Engineer understands that each case is unique. Although there are various generic processes that are commonly employed, every raw water source is different, each with a different chemical composition that depends on local geological, weather and anthropogenic influences. For example, water quality in a specific catchment is impacted by weathering of the particular rock and soil types that are present, as well as influences of livestock and agricultural processes. Underground waters, such as those produced from mining operations, are influenced by the chemistry of the rock surrounding and within the aquifer, as well as the source of the water before it enters the aquifer.