Abstract: A screw press has a cylindrical screening section mounted to a frame. The screening section is able to rotate but can be prevented from rotating. A sprayer system is operable to spray water on the screening section. In a cleaning process, the screening section is rotated while water is sprayed against it. Optionally, the power required to rotate the screen may be provided by an auger drive mechanism. The screening section may have openings sized to retain flocculated solids. The screw press may be used to thicken a sludge from a waste water treatment plant.

Abstract: Waste or organic material is compressed at a pressure sufficient to burst cells, for example 50 bar or more, and separated into a dry fraction and a wet fraction. The wet fraction is treated in an anaerobic digester to produce biogas after removing grit. The wet fraction is diluted, preferably with sludge, before it is degritted. Optionally, floatables are removed from the fraction before it is added to the digester.

Abstract: Feed water is processed in an anaerobic digester. A solid-liquid separation device, for example a sludge screw thickener, treats a stream drawn from the digester in a recirculation loop. The solids portion is returned to the digester to increase the solids retention time and the TSS concentration in the digester. A liquid portion with less than 5% of the solids in the stream is removed and optionally treated further. The flow rate to the solid-liquid separation device is preferably greater than the influent flow rate. The solid-liquid separation device may receive digestate at a TSS concentration of 4% or more and return a solids portion having a TSS concentration of over 10%. The feed water is preferably one or more industrial waste streams having a COD concentration of 20,000 to 50,000 mg/L and a TSS concentration from 1-5%. The organic loading rate may be 10-12 kg/COD/m3/day.

Abstract: Sludge from an anaerobic digester is treated to recover one or more of fibers, or solids or liquids with a high nutrient content. The solids or liquids can be used as a fertilizer. The fibers can be used in a plant growing medium. Solids are separated from liquids in the sludge and dried. The solids may be dried to produce a flake or pellet. Ammonia in the liquids is recovered and used to produce a concentrated acidic ammonium salt solution. This solution may be mixed with the solids to produce a nitrogen enhanced solid. The fibers and solids or liquids can also be used in combination to produce an enhanced plant growing medium. A device and process for removing ammonia from a liquid can be used in the system or separately.

Abstract: A digester tank has a servicing device that allows access to the interior of the digester tank. The sealing device may have a movable retention wall adapted to resist the pressure of the gas inside the digester by one or more of a) increasing the bending resistance of the retention wall, for example by inflating pockets in the wall, b) forcing the lower edge of the retention wall downwards, for example by weight, a mechanical arm or inflating pockets, and c) providing a mechanical structure within the retention wall, for example a non-moving cage-like structure. A sealing device with a fixed wall has a pipe with an isolation valve between the headspace of the tank and the inside of the sealing device. In operation, a seal may be formed across the separation curtain by raising the level of the liquid contents and closing the isolation valve.

Abstract: Solid waste, for example source separated organics (SSO) or commercial and industrial (C&I) waste or both, are treated by first pressurizing the waste against a screen to produce a solids fraction and a liquid fraction. The liquid fraction can be treated in an anaerobic digester. The solids fraction is pulverized or milled, for example with a hammer mill, preferably after being diluted. The pulverized or milled waste is separated again to provide a second solids faction and a second liquid fraction. The liquid fraction can be treated in an anaerobic digester. The solids fraction is primarily inert and can be landfilled, preferably after being washed.

Abstract: Sludge from an anaerobic digester is treated to recover one or more of fibers, or solids or liquids with a high nutrient content. The solids or liquids can be used as a fertilizer. The fibers can be used in a plant growing medium. Solids are separated from liquids in the sludge and dried. The solids may be dried to produce a flake or pellet. Ammonia in the liquids is recovered and used to produce a concentrated acidic ammonium salt solution. This solution may be mixed with the solids to produce a nitrogen enhanced solid. The fibers and solids or liquids can also be used in combination to produce an enhanced plant growing medium. A device and process for removing ammonia from a liquid can be used in the system or separately.

Abstract: Sludge from an anaerobic digester is treated to recover one or more of fibers, or solids or liquids with a high nutrient content. The solids or liquids can be used as a fertilizer. The fibers can be used in a plant growing medium. Solids are separated from liquids in the sludge and dried. The solids may be dried to produce a flake or pellet. Ammonia in the liquids is recovered and used to produce a concentrated acidic ammonium salt solution. This solution may be mixed with the solids to produce a nitrogen enhanced solid. The fibers and solids or liquids can also be used in combination to produce an enhanced plant growing medium. A device and process for removing ammonia from a liquid can be used in the system or separately.

Abstract: Waste solids are treated by pyrolysis at a temperature over 700 degrees C. to produce char and a gas. The gas is treated in an anaerobic digester. In one system, gas and digestate are brought into contact in a diffusion cone. In another option, headspace gas above the digestate is re-circulated through the digestate, for example by way of an eductor downstream of the diffusion cone.

Abstract: A waste stream is treated by anaerobic digestion. A process is described involves a step of separating solids from digestate, and returning separated solids to a digester. Optionally, there may be a step of solids separation in which larger solids are removed from the digester. A process and apparatus are described for treating waste sludge from a wastewater treatment plant in an anaerobic digester. Feed sludge is thickened or solids are separated from digestate and returned to the digester. Additional co-digestion waste may be added to the digester. The process and apparatus may be used in a retrofit of an existing wastewater treatment plant.

Abstract: An anaerobic digester is fed a feedstock, for example sludge from a municipal wastewater treatment plant, and produces a digestate. The digestate is dewatered into a cake. The cake may be dried further, for example in a thermal drier. The cake is treated in a pyrolysis system to produce a synthesis gas and biochar. The gas is sent to the same or another digester to increase its methane production. The char may be used as a soil enhancer.

Abstract: A waste stream is treated by anaerobic digestion. A process is described involves a step of separating solids from digestate, and returning separated solids to a digester. Optionally, there may be a step of solids separation in which larger solids are removed from the digester. A process and apparatus are described for treating waste sludge from a wastewater treatment plant in an anaerobic digester. Feed sludge is thickened or solids are separated from digestate and returned to the digester. Additional co-digestion waste may be added to the digester. The process and apparatus may be used in a retrofit of an existing wastewater treatment plant.

Abstract: An anaerobic digester is fed a feedstock, for example sludge from a municipal wastewater treatment plant, and produces a digestate. The digestate is dewatered into a cake. The cake may be dried further, for example in a thermal drier. The cake is treated in a pyrolysis system to produce a synthesis gas and biochar. The gas is sent to the same or another digester to increase its methane production. The char may be used as a soil enhancer.

Abstract: A waste stream is treated by anaerobic digestion. A process is described involves a step of separating solids from digestate, and returning separated solids to a digester. Optionally, there may be a step of solids separation in which larger solids are removed from the digester. A process and apparatus are described for treating waste sludge from a wastewater treatment plant in an anaerobic digester. Feed sludge is thickened or solids are separated from digestate and returned to the digester. Additional co-digestion waste may be added to the digester. The process and apparatus may be used in a retrofit of an existing wastewater treatment plant.

Abstract: Low strength wastewater such as municipal sewage is treated using an anaerobic digester. In some examples, a wastewater stream is separated into a solids rich portion and a solids lean portion. The solids lean portion is treated, for example to remove nitrogen. The solids rich portion is treated in an anaerobic digester, preferably with influent or recuperative thickening. In another example, the wastewater stream is fed to an anaerobic digester and solid-liquid separation stages downstream of the digester return active bacteria and undigested organics to the digester. Both cases may use a process train comprising treatment in an anoxic tank followed by a nitritation tank with a portion of the effluent from the nitritation tank recirculated to the anoxic tank to provide nitritation and denitritation.

Abstract: An apparatus for recovering nutrients or water from digestate comprises one or more solid-liquid separation units, an ammonia stripping device, and a gas scrubbing unit. In a process, digestate is separated into a solids portion and a liquid portion. Ammonia is stripped from the liquid portion and converted into an ammonium salt solution which may be sold or used as, or blended with, a fertilizer product. Optionally, at least part of the remaining liquid portion may be concentrated to produce brine. The brine is mixed with the solids portion. The mixture may be dried and used as, or blended with, a fertilizer product. Optionally, a least part of the remaining liquid portion may be re-used as dilution water in a digester. A solids portion of the digestate, and one or both of an ammonium salt solution and a brine, may be used as fertilizer without thermal drying.

Abstract: Low strength wastewater such as municipal sewage is treated using an anaerobic digester. In some examples, a wastewater stream is separated into a solids rich portion and a solids lean portion. The solids lean portion is treated, for example to remove nitrogen. The solids rich portion is treated in an anaerobic digester, preferably with influent or recuperative thickening. In another example, the wastewater stream is fed to an anaerobic digester and solid-liquid separation stages downstream of the digester return active bacteria and undigested organics to the digester. Both cases may use a process train comprising treatment in an anoxic tank followed by a nitritation tank with a portion of the effluent from the nitritation tank recirculated to the anoxic tank to provide nitritation and denitritation.

Abstract: In a waste treatment system and process, relatively low and high solids concentration streams are treated in generally parallel anaerobic reactors. The reactors may share a common wall or gas collecting cover. The reactors may also share a common downstream aerobic treatment unit. Solids produced during downstream treatment of effluent from one or both anaerobic reactors may be returned to the high solids concentration stream. The low solids concentration stream may be treated in an attached growth anaerobic digester.

Abstract: A biofilm carrier screen is adapted for use with a moving bed bioreactor (MBBR). The screen has a screening body connected to an effluent pipe. The effluent pipe optionally has two parts separated by a union, preferably a pitless adapter. The screening body can be lifted from a bioreactor tank for maintenance after disconnecting the union. The screening body may have an aerator to provide bubbles to disperse biofilm carriers from the screening body. The screening bod may extend downwards from a mount near the top of the tank. In the case of an anaerobic MBBR, the screening body may extend downwards from a service box through a cover over the tank.

Abstract: An apparatus for recovering nutrients from digestate comprises one or more solid-liquid separation steps, and dryer, an ammonia stripping device, and an evaporator. In a process, digestate is separated into a solids portion and a liquid portion. Ammonia is stripped from the liquid portion and converted into an ammonium solution or salt which may be used as, or blended with, a fertilizer product. At least part of the remaining liquid portion is concentrated to produce brine. The brine is mixed with the solids portion. The mixture is dried and may be used as, or blended with, a fertilizer product.