Abstract: A sealing system for a covered tank, particularly a fixed gas-sealing tank in a wastewater treatment system, includes a thrust ring positioned just inside the tank rim, secured to a series of radial beams for the cover. Preferably supported on corbels anchored to the interior tank wall, the thrust ring has an outwardly extending generally horizontal flange that overlies the edge of the tank rim. To this flange and to the top of the tank rim is secured a flexible membrane seal, around the periphery of the tank. The membrane seal is easily installed, reliable as a seal, and can be efficiently replaced when needed.

Abstract: A sealing system for a covered tank, particularly a fixed gas-sealing tank in a wastewater treatment system, includes a thrust ring positioned just inside the tank rim, secured to a series of radial beams for the cover. Preferably supported on corbels anchored to the interior tank wall, the thrust ring has an outwardly extending generally horizontal flange that overlies the edge of the tank rim. To this flange and to the top of the tank rim is secured a flexible membrane seal, around the periphery of the tank. The membrane seal is easily installed, reliable as a seal, and can be efficiently replaced when needed.

Abstract: A vertical motion mixer has a drive mechanism with two axes of guidance for vertical motion. A reciprocating yoke is fixedly secured to the driving shaft for the mixer, without any guide bearing for the mixer driving shaft. The mixer drive unit is of compact and simplified design with minimal moving parts, and including drive gearing with planetary gears to minimize wear during reciprocating movement.

Abstract: In a municipal sewage treatment system, a biological process tank, typically an anaerobic digestion process, has a flexible, inflated membrane cover. At least one draft tube mixer is installed on the tank, interrupting the gas supported cover with a platform having a flat base and may have upwardly extending sides that generally follow the contour of the inflated cover. The draft tube is connected to the platform and preferably supported on the floor of the tank. The mixer mechanism can be lifted out of the draft tube without escape of gas from the inflated cover.

Abstract: A reciprocating motion disk for mixing wastewater in a tank of a treatment plan is optimized for geometry, along with cycling speed and stroke length, to cause effective mixing velocity throughout the tank.

Abstract: A reciprocating motion disk for mixing wastewater in a tank of a treatment plan is optimized for geometry, along with cycling speed and stroke length, to cause effective mixing velocity throughout the tank.

Abstract: A reciprocating motion disk for mixing wastewater in a tank of a treatment plan is optimized for geometry, along with cycling speed and stroke length, to cause effective mixing velocity throughout the tank.