Abstract: A sewage treatment plant, on the liquid side, is operated so as to effect nitrification and denitrification within a single tank and simultaneously to remove water, without the need for separate clarification. An aerobic/anoxic zone is maintained in a single tank, wherein the SymBio process of U.S. Pat. No. 5,906,746 is maintained. This is combined with the advantages of an MBR process, by placing a series of membrane separators within the tank and continuously withdrawing nearly pure water. Supplemental process air provided in the MBR tank is controlled by the SymBio process to maintain simultaneous nitrification and denitrification in a single tank and thus reducing the additional process air requirements.

Abstract: In the liquid side of sewage treatment process, a combination aerobic/anoxic stage is closely monitored such that phosphorus can be removed as well as nitrogen. As in a known process, the aerobic/anoxic stage is monitored as to a coenzyme of the active bacteria. When the bacteria of flocs within this stage show a switch to anaerobic condition via such coenzyme, the low dissolved oxygen level in the stage is maintained for a preselected period of time or to a preselected extent of the anaerobic condition, before oxygen is added. This somewhat brief anaerobic condition within the flocs is sufficient to release significant amounts of phosphorus into the liquid. When aeration then is increased, enhanced biological phosphorus uptake is effected. A small aerobic stage is included after the aerobic/anoxic stage to ensure maximum phosphorus uptake, and in one embodiment this stage includes a membrane separator, allowing downstream secondary clarification to be eliminated.

Abstract: An underdrain filtration system has improved perforation structure, the perforations being positioned to admit the filtrate into a plenum defined by elongated underdrain rib structures of the system. Instead of drilled or laser-cut holes or slits, the slits are formed by stamping discs from the stainless steel plate, such that the discs extend parallel to the surrounding flat area but are raised just sufficiently to define a plurality of slits under each disc, preferably two to four slits, each being an arc of slightly less than 180°, 120° or 90°, respectively. A pair of metal bridges remain to integrally connect the raised disc and the surrounding flat field. Consistent perforation width is achieved, at, for example, 0.010″ width varying by less than 0.001″ in either direction, improving consistency of pressure drop.

Abstract: A clarifier in a sewage treatment process includes efficient scum removal within the influent well, with discharge of the scum and other floatables as a dedicated waste stream separate from return activated sludge and biological scum collected in the clarifier. In one embodiment the scum removal system has an inclined scum ramp at the leading edge of each of two scum removal troughs, with a forward edge below the liquid surface. The scum troughs pass through an arc of rotation, building up scum, which accumulates and is pushed forward by the scum ramp. At least once per revolution, the moving scum ramp approaches a stationary scum surface blade that extends partially under the liquid surface and provides a barrier to the forwardly pushed scum. This blade contacts and slides up the ramp, sweeping the scum up the ramp and into the scum trough.

Abstract: A clarifier in a sewage treatment process includes efficient scum removal within the influent well, with discharge of the scum and other floatables as a dedicated waste stream separate from return activated sludge and biological scum collected in the clarifier. Foam contained within the influent well may be treated with bacteria-killing agents or with anti-foaming agents. In one embodiment the scum removal system has an inclined scum ramp at the leading edge of each of two scum removal troughs, with a forward edge below the liquid surface. The scum troughs pass through an arc of rotation, building up scum, which accumulates and is pushed forward by the scum ramp. At least once per revolution, the moving scum ramp approaches a stationary scum surface blade that extends partially under the liquid surface and provides a barrier to the forwardly pushed scum. This blade contacts and slides up the ramp, sweeping the is scum up the ramp and into the scum trough.

Abstract: An underdrain unit of the type having air and water backwash for backflushing a granular filtration system has improved retention structure for retaining folded, perforated stainless steel underdrain plates against the floor of the tank drain. The retention structure is in the form of hollow horizontal tubes which not only hold the folded plates in place but also serve to deliver backwashing air. Thus, instead of air delivery tubes being mounted above a series of brackets that hold the folded plates in place against the floor, the air delivery in the system of the invention is via the same structural element which retains the folded plates. Embodiments are described for gravel bed systems and for sand filter systems.

Abstract: A clarifier in a sewage treatment process includes efficient scum removal within the influent well, with discharge of the scum and other floatables as a dedicated waste stream separate from return activated sludge and biological scum collected in the clarifier. In one embodiment the scum removal system has an inclined scum ramp at the leading edge of each of two scum removal troughs, with a forward edge below the liquid surface. The scum troughs pass through an arc of rotation, building up scum, which accumulates and is pushed forward by the scum ramp. At least once per revolution, the moving scum ramp approaches a stationary scum surface blade that extends partially under the liquid surface and provides a barrier to the forwardly pushed scum. This blade contacts and slides up the ramp, sweeping the scum up the ramp and into the scum trough.

Abstract: An aerobic treatment process is operated to reduce overall oxygen requirements, to maintain general pH balance and to produce a low-coliform solids effluent. From the system's clarifier a slurry of concentrated solids is moved to a premix basin, where the slurry is vigorously aerated for a sufficient time to raise microbial activity and dissolved oxygen content. The aerated, microbially active sludge is then moved to a gravity thickener basin, in which solids are allowed to settle to the bottom without aeration, to establish a quiescent state in the settled sludge and also an anoxic stage. This causes the sludge to be denitrified by microbial action, raising and stabilizing the pH of the sludge. Separated supernatant liquid is decanted and removed from the gravity thickener. The sludge is moved into an aerobic digester, where the sludge is aerated and nitrification occurs but using less aeration than normally required in a digester, due to the effect of anoxic/aerobic phases.

Abstract: A clarifier basin in a wastewater treatment system includes a sludge collection manifold structure which allows individual visual inspection and monitoring of sludge flows from individual sludge removal tubes, representing different sludge collection zones in the basin. The width from front to back of each clarifier arm is maintained to a minimum by providing a baffle adjacent to the outflow of each sludge removal tube. This defines a separate sludge flow for each sludge removal tube, although the flows are integrated beyond the baffles in the common channel. The benefits of high velocity sludge flow, minimal arm width and individual monitoring and sampling outflow from each removal tube are maintained, while providing an arrangement which is structurally sound, minimal in weight and less costly than many previous clarifier systems.

Abstract: Improved gas distribution and mixing is achieved in a gas/liquid mixing basin particularly for aerobic or anaerobic sewage digesters. In addition to a draft tube positioned generally centrally in the aeration or anaerobic basin and served by one or more gas-releasing diffusers, the system of the invention includes peripheral draft tubes surrounding the central draft tube, each tube having at least one gas diffuser within. The circulation of liquid and gas bubbles from the larger, central draft tube is supplemented by circulation from the peripheral draft tubes. In particular, "dead areas" or less active areas of the liquid, which are not sufficiently reached by gas-mixing from a single draft tube in many basin configurations, are reached by circulation from the peripheral draft tubes and such dead areas are virtually eliminated.

Abstract: A substantially gas tight tank cover is designed such that the structural beams of the cover serve also as an air distribution system for bubbling air through a liquid in the tank. Vertically oriented gas bubbler and orifice devices include hardware enabling easy access to the orifice and bubbler from the top of the tank cover. The design is such that all necessary maintenance including major repairs can be performed from the cover without draining the basin or removing the cover. The system is particularly adaptable to sewage treatment plants, but is advantageous for other applications as well, wherein gases are to be bubbled through liquids at multiple locations.

Abstract: An improvement is provided in a water or wastewater clarifier drive mechanism to permit access to or removal of the hoop gear assembly without draining the clarifier or disconnecting the drive cage from the pier that supports it. A torque transfer ring is provided to couple the drive cage support to the hoop gear. A plurality of support screws are employed to temporarily support the drive cage support on the drive housing during maintenance operations. With the drive cage support supported on the drive housing, the torque transfer ring may be removed, thereby providing unobstructed access to the hoop gear and bearings for maintenance or replacement. A maintenance platform is also described that is adapted to be temporarily supported by the drive cage support and to provide clearance for removal of the torque transfer ring and the hoop gear or bearing assembly.

Abstract: A device for extracting liquid from sludge which uses a perforate conveyor belt to carry the sludge through the device. A portion of the belt carrying the sludge is supported by a grid support system which includes a series of wear support members. These wear support members each have a rigid body member having an insert wear strip slidably mounted on the rigid body member which can easily be removed from the device without disconnecting the body member from the device.

Abstract: A gas diffuser is provided for water and wastewater treatment. The gas diffuser unit includes a vertical open-bottomed injection pipe extending downwardly and having a plurality of vertical slot-shaped ports adjacent the open bottom. A gas bubble distribution body including a lip portion is located above the open bottom of the injection pipe, and a conical shaped deflector may be mounted on the gas injection pipe above the distribution body. Gas released from the vertical slot-shaped ports forms relatively large diameter bubbles which rise due to buoyancy. The large diameter gas bubbles are broken into smaller diameter gas bubbles and are evenly distributed upon the bottom surface of the gas bubble distribution body above the open bottom of the injection pipe. The lip portion on the gas distribution body promotes turbulence in the rising bubbles, and produces smaller diameter gas bubbles.

Abstract: An orifice device, which includes fluid guidance structure and a flow restriction, for use in a diffused aeration system for treating polluted wastewater is disclosed. The device is inserted directly into the run of a tee-joint which connects a fluid injection pipe to a fluid manifold. The orifice device is provided with fluid guidance structure to reduce fluid turbulence as the flow of fluid changes direction from horizontal to vertical. The orifice device also is provided with an orifice to backpressure fluid and enhance even distribution of fluid among several injection pipes. The upper exterior of the orifice device is threaded to be engageable with the interior of a threaded tee-joint. The orifice device is removeable in order to facilitate cleaning and maintenance of the aeration system.

Abstract: A self-supporting underdrain unit to be placed upon the substantially horizontal floor of a filter tank to provide a liquid filtration system is disclosed. The self-supporting underdrain unit provides separately controllable fluid and exhaust gas header systems for backwashing. The exhaust gas and backwashing fluid are mixed in a turbulent mixing zone to provide superior backwashing and cleansing action.