**3.2 Land requirements**

The increasing land prices and scarcity of available land resources are becoming one of the bottlenecks for WWTP management issues [54]. Land requirement for the WWTPs directly affects its performance and costs. The land requirement per m2 /p.e. for UASB+DHS and UASB+TF systems are shown in **Table 2**. The available literatures show that the land required for the construction of UASB+DHS is almost 10 times less than UASB+TF. Though having the same external design, this difference could be explained by the supporting media. The DHS sponges are comparatively smaller and light weight in comparison to the most frequently used media such as stones, gravel, plastics etc. which implies much higher tank volumes and areas. Nonetheless, having the similar working principle, the packing of the media in DHS system resulted in smaller footprint.
