In the first system, which is precisely the lower lateral discharge, or also called lateral channel drain, the filtrate comes out from the lower part of the filter plate and is conveyed through a curve into a special tray (which is normally open) used precisely for collection of filtrate.
In some cases there is also an exclusion tap to prevent a single plate from discharging onto the channel.
This is useful when during the filtration phase we realize from the color of the filtrate that a cloth is broken and we can thus exclude that cloth from filtration.