All of the plants we have used so far have used vertical flocculation. It works well for low flow rates but is significantly more difficult to drain than a horizontal flocculator.
In order to accommodate higher flow rates, we have started to develop a code for horizontal flocculation. These are much easier to drain than vertical flocculators, so we are considering using them for low flow rates as well.
The design tool will do calculations to find the minimum flow rate that should be used for horizontal flocculation for a given design.