Patent ID: 7926510

Claim:
A riser system for mounting vertically on an access opening at the top of a wastewater treatment tank comprising: an adaptor ring, for affixing to the top of a tank, and for receiving a riser or a lid, having an upper end comprising a circumscribing L-shape surface, wherein a first portion of the surface runs horizontally and circumferentially and a second portion runs circumferentially and vertically, plurality of tabs spaced apart around the circumference of the upper end, and a lower end, for affixing to the top of a wastewater treatment tank; and, a riser, for mounting on the adaptor ring or on another like riser, having an upper end comprising a circumscribing L-shape surface, wherein a first portion of the surface runs horizontally and circumferentially and a second portion runs circumferentially and vertically, a plurality of tabs spaced apart around the circumference of the upper end; a lower end having a circumscribing L-shape surface, wherein a first portion of the surface runs horizontally and circumferentially and a second portion runs circumferentially and vertically, and a plurality of L-shape slots spaced apart around the circumference of the lower end, each slot having an open lower end which runs vertically and an upper end which runs circumferentially; wherein said slots are spaced apart and shaped for receiving said tabs, so that each tab is moveable vertically and then horizontally within the slot in which it is received, when the riser and adaptor ring are mated, and, when two like risers are mated; and, wherein at least one of said circumferential running portions of at least one of said circumscribing L-shape surfaces has micro-grooves.