Here we will define advanced wastewater treatment as any process above and beyond the typical primary and secondary wastewater treatment processes, such as tertiary treatment, but also to include unique, proprietary and powerful appraoches to those steps.
Nine times out of ten the purpose of advanced wastewater treatment is to achieve a higher level of wastewater treatment, with a higher quality effluent all things being relative.
This question is pretty much answered by the nature of advanced wastewater treatment, to achieve a higher level of the treatment of wastewater, usually involving higher environmental compliance but also a higher level of environmental stewardship and social responsibility.
There are myriad approaches to advanced wastewater treatment, all of which involved specialized wastewater treatment equipment and wastewater chemicals.
Quite frankly nowadays everyone should be using some sort of advanced wastewater treatment process, everyone meaning companies, industries, municipalities involved with industrial wastewater treatment.