Every wastewater is ...

Every wastewater is different, hence, one technology which is economical and efficient for that wastewater treatment in that economical range, will not be economical/efficient for another type of wastewater.

Also, both the terms are contradictory, Economical and Efficient for New Technology.

Consider, desalination process, RO based desalination is economical compared with evaporation and condensation. But comparatively, has less efficiency. Still generally incorporated in various desalination project.

However, oil-rich countries do the later one, as there is no economical constrain.

As you are looking for some cost efficient  and portable  size, easy to operate, long shelf life technology or system.

but the question is for which type of wastewater. This is very general question.

Kindly enlighten us regarding the type of wastewater. 

So that, actual experts, sorry marketers, can give their suggestions and share their experiences with the existing technologies in there respective treatment plants, for your kind of wastewater.