Underdrain useful in the construction of a filtration device

An array of underdrains capable of being fixed onto the bottom of a plurality of wells with separation material substantially therebetween, thereby providing a flow path wherein fluid placed in the wells is flowable first into and through said separation material, then into and ultimately out of the underdrain;

• the array of underdrains comprising a monolithic construction, and having an upstream side and a downstream side, said fixation to said wells being enabled proximate said upstream side, said flow of fluid out of said underdrain occurring proximate said downstream side;
• the underdrain having a spout at said downstream side,
• the spout having a central axis and comprising an inner side surface, an outer side surface, and a floor having an inner and an outer end surface, the inner side surface defining a fluid pathway through said spout that runs substantially along said central axis, the fluid pathway terminating downstream at said inner end surface, said spout floor having a plurality of microholes provided therethrough or therearound where the plurality of microholes have diameters ranging from approximately 0.02 mm to approximately 0.76 mm and where the outer side surface of the spout runs substantially parallel with the central axis of the spout and wherein the outer side and end surfaces of said spout have a coarse microstructure formed by the use of an appropriately rough-textured mold, or by mechanical or chemical roughening.