In our visit [review of posted video-instruction(s)] to a city's/town's municipal wastewater treatment plant (WWTP) or the Water resource recovery facility (WRRF), we noticed wastewater treatment for the (i) liquid-portion, and (ii) solids/sludge(s)-portion. Please identify, in a separate (paragraphic) listing, those units/processes observed on each of the two municipal wastewater-treatment processes (or, the treatment trains).