Abstract: A rotating screen has one or more panels arranged into a cylinder, or drum. The panels have openings in a micro-screening range, for example 100 microns or less. Wastewater to be screened is fed to the interior of the drum. The drum rotates constantly but the rotation may be discontinuous and the speed of rotation may be variable. The drum may be cleaned by an air knife. If the wastewater contains oil and grease, a short hot water spray may be provided before cleaning with the air knife. Optionally, an internal auger conveys solids down the length of the drum to an outlet. The rotating screen may be used for primary treatment of wastewater. The rotating screen may be used produce screenings with a dried solids concentration of 5% or more, for example 6-7%. The primary sludge may be treated in an anaerobic digester.

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: In a wastewater treatment system, feed water is processed by anaerobic digestion, preferably in an anaerobic moving bed bioreactor (AnMBBR). Effluent from the AnMBBR passes through one or more solid-liquid separation units. A solids portions is treated by hydrolysis or suspended growth anaerobic digestion. A liquid portion of the hydrolysis or suspended growth anaerobic digestion effluent is returned to the AnMBBR or blended with effluent from the AnMBBR. The AnMBBR effluent may be treated with an aerobic moving bed bioreactor (MBBR) before the one or more solid-liquid separation steps. Membrane filtration may provide a first solid-liquid separation step. A thickened waste stream may be withdrawn from a recirculation loop flowing from the first solid-liquid separation unit to the MBBR. Optionally, a solids portion separated from the feed water upstream of the AnMBBR may also be treated by hydrolysis or suspended growth anaerobic digestion.

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: An immersed membrane filtration system is operated in view of an electricity pricing programs in which the price of electricity varies over time. Examples of such programs include time of use pricing, critical peak pricing and critical peak rebate programs. Alternatively, the filtration system may be operated, for example as part of a smart grid, in view of requests or demands by an electrical utility for time limited reductions in energy use. During a high energy cost period of time, one or more membrane units are shut down. Preferably, aeration of the still operating membrane units is not increased. The flux of the still operating trains may be increased towards a pre-determined maximum permitted flux, or towards a maximum flux that is calculated in view of operational parameters such as water temperature or viscosity. Optionally, during a low energy cost period of time, one or more additional membrane units may be turned on.

Abstract: A static screen used upstream of a membrane assembly within a water treatment system has a screening surface with a number of openings distributed over its area. Liquid flows through the screening surface to reach the membrane assembly. Various shapes of screening surfaces are described including three-dimensional bodies with openings at or near their lower ends. Methods for cleaning the screen are described including aeration, backwashing and lowering down the water level in an upstream section by partially or completely draining a tank. Various treatment systems or process designs incorporating the screen are described. Screen elements may be made in two or more parts comprising a supporting structure and a separation layer and may be mounted on a conduit or pan.