Abstract: A method of ballasting a cover of a sludge digester that is comprised of a storage tank and the cover. The method includes placing a ballast into the storage tank in a first predetermined position, placing the cover onto the storage tank, lowering a lifting member of a lifting device through an access port in the cover and into the storage tank, securing the lifting member to the ballast, using the lifting device to lift the lifting member and the ballast until the ballast is in a second predetermined position that is substantially above the first predetermined position, engaging a support bracket attached to the cover with a support member; and securing the ballast to the cover with the support member while the ballast is in a third predetermined position that is substantially below the second predetermined position.

Abstract: A method of ballasting a cover of a sludge digester that is comprised of a storage tank and the cover. The method includes placing a ballast into the storage tank in a first predetermined position, placing the cover onto the storage tank, lowering a lifting member of a lifting device through an access port in the cover and into the storage tank, securing the lifting member to the ballast, using the lifting device to lift the lifting member and the ballast until the ballast is in a second predetermined position that is substantially above the first predetermined position, engaging a support bracket attached to the cover with a support member; and securing the ballast to the cover with the support member while the ballast is in a third predetermined position that is substantially below the second predetermined position.

Abstract: A method of ballasting a cover of a sludge digester that is comprised of a storage tank and the cover. The method includes placing a ballast into the storage tank in a first predetermined position, placing the cover onto the storage tank, lowering a lifting member of a lifting device through an access port in the cover and into the storage tank, securing the lifting member to the ballast, using the lifting device to lift the lifting member and the ballast until the ballast is in a second predetermined position that is substantially above the first predetermined position, engaging a support bracket attached to the cover with a support member; and securing the ballast to the cover with the support member while the ballast is in a third predetermined position that is substantially below the second predetermined position.

Abstract: A retractable sediment collection device for use in settling tanks is disclosed which has means for collecting and removing sediment from the floor of the settling tank. The retractable sediment collection device is structured to move back and forth along the floor of a tank to remove the sediment therefrom. The retractable sediment collection device includes a lifting mechanism which engages a sediment collector and raises it from the floor of the tank. Although the retractable sediment collection device is suitable for use in any kind of settling tank, it is particularly suited for use in closed tanks where access to the interior of the tank is limited through a single opening. The retractable sediment collector may be raised from floor of the tank to the top of the tank where the operating mechanisms can be accessed for repair or maintenance without removing the entire sediment collector from the tank.

Abstract: A gas-holding sludge digester is disclosed having a sideskirt which telescopes in a liquid chamber which is separate from a main digester tank and wherein the ballast is structured to increase gas pressure of the gas contained within the cover as the sideskirt telescopes upward.

Abstract: A sludge digester having a main tank in conjunction with a gas-holding cover is disclosed. The cover includes a roof and a depending sideskirt which telescopes in relationship to the main tank. Positioned at the bottom edge of the sideskirt are a multitude of ballast members. A chamber, adapted to contain a quantity of liquid, is associated with the main tank. The sideskirt and the ballast members are submerged within the liquid contained within the chamber to form a gas tight seal of the cover with the main tank. The chamber also includes a system for maintaining a predetermined liquid level in the chamber dependent on the position of the ballast members in the chamber.

Abstract: A sludge digester gas-holder is disclosed having a gas-holding cover with ballast members submergible in a liquid medium contained within a chamber circumscribing the upper portion of the tank wall and separate from the main tank cavity.

Abstract: A cover and erection method for a tank, sedimentation device or building cover constructed over or within a generally continuous upstanding circular side wall (30), made up of a series of concentric spaced thrust rings (11, 12, 21) having multiple short curved radial beams (14, 19) bridging the annuli between the rings and cover plates (17, 21) extending across the spaces between adjacent ones of the beams between each of the spaced rings. Erection may be from the wall inwardly or from the center to the wall. In either event an intermediate thrust ring is temporarily supported at an elevation above and within the side wall and the beams set across the rings in relatively short radial spans prior to welding of beams and plates to the respective rings. By this technique, small lightweight beams can be utilized for building large-diameter covers or domes with each rise span being of relatively small length.

Abstract: A digestor includes a tank and an inverted dish-shaped cover, the lower end of which extends into sludge contained within the tank. The cover is ballasted by a number of ballast members which resemble tubs and which are integrally formed of concrete. Each ballast member is mounted with its cavity facing upwardly so that the ballast cavities automatically fill with sludge upon start-up of the digestor. When partially surfaced above the sludge, the predetermined total weight of sludge in the ballast members causes a substantial increase in the pressure exerted by the cover on the contained gas than would be exerted by the cover and unfilled ballast members.

Abstract: An improved anaerobic digester 10 includes a cylindrical concrete sidewall 16 having a plurality of guide channel assemblies 40 bolted thereto at uniformly spaced locations along its circumference. The digester further includes a cover 18 adapted to be buoyed upwardly above the surface of the liquid by the digester gas. The digester cover is guided by roller assemblies 70 that cooperate with the guide channel assemblies 40. When gas is not present within the digester, the cover is supported by the cooperation of a plurality of stop tubes 76 and 78 that project radially outwardly of the cover from a thrust ring 24 incorporated at its periphery and a plurality of stop members 60 and 62 that are affixed to the guide channel assemblies at readily accessible locations close to the top of the tank.