Do reed-beds take up a lot of space?

Not really.

Our vertical flow reed-beds are generally sized on the basis of 2.5 m2/person equivalent.

Our Sub-Surface Flow-Horizontal Flow Reed-beds, which we only use for tertiary treatment and polishing, are sized on the basis of 1.0 m2/person equivalent.

Our Overland Flow-Horizontal Flow Reed-beds, used in the same way, are sized on the basis of approximately 2.0 m2/person equivalent.