Detail trickling filter, with minimum depth for treatment plant.
Drawing labels, details, and other text information extracted from the CAD file (Translated from Spanish):
Viewnumber, Sheetnumber, Perforated hg pipe, Indicates meaning, Comes from primary settler, Door lock, Volcanic stone, Driving channel, Perforated hg pipe, Pipe anchor, Comes from primary settler, Percolating filter plant, scale, section, scale