Abstract: A wastewater treatment apparatus of the present invention is configured to biologically filter wastewater through multimedia by consecutively performing two stages (the first and second stages) for a multimedia biological filtration process. A carbon source and coagulant are respectively injected during the first and second multimedia biological filtration processes. The first stage multimedia biological filtration process is carried out in anoxic conditions and the second stage multimedia biological filtration process is carried out in aerobic conditions. The media for the first and second stage biological filtration processes are arranged in large-middle-middle large-small size. Thus, the present invention can secure excellent treated water while minimizing loss of water-head by maximizing reflux capability of solids.

Abstract: A modular system for reclamation of a fluid includes a cavitation reactor operative to mechanically oxide the fluid and an ion precipitation system that receives the oxidized fluid from the cavitation reactor and thereafter introduces one or more ions at various locations to initiate precipitation of select materials. The system and associated methodology further includes injecting dissolved air and emulsion breaking chemistry into the fluid before cavitation, coalescing emulsified particulates from the fluid and saturating the fluid in an air saturation chamber that is operable to form a microbial filter.

Abstract: A water treatment unit includes a mixing chamber surrounding the upper end of a riser containing an impeller. Water can be moved from a body of water up through the riser, and out through laterally directed openings into the chamber adjacent to an air inlet. The water moving out the laterally directed openings of the stand pipe, mixes with air drawn in through the air inlet to oxygenate the water, and the oxygenated water exits the chamber into the body of water through one or more water outlets in the lower portion of the chamber due to the head developed by the inflow of water into the chamber. The outward flow of water from the chamber can cause a toroidal or other desired flow of water within the body of water surrounding the water treatment apparatus.

Abstract: The invention, belongs to the field of wastewater treatment technology, is a two-phase anaerobic reactor enhanced by addition of zero valent iron (ZVI). In the reactor, 2˜4 ZVI-filling layers are settled in the middle of the anaerobic hydrolysis-acidification tank, the effluent of which is fed into the rear anaerobic methanogenic tank. The degradation of organics is effectively enhanced in the anaerobic hydrolysis-acidification tank with dosing of ZVI, which may produce more acetic acid that is a desired substrate for the subsequent methanogenesis. Meanwhile, the acidic environment of the hydrolysis-acidification tank is helpful for the dissolution of ZVI to maintain its activity. The reactor is reasonably designed with high performance and strong shock resistance in anaerobic treatment of various wastewaters. Tests in lab-scale showed that hydrolysis-acidification and methanogenesis in this combined system were significantly improved compared with a reference reactor without addition of ZVI.

Abstract: A system for enhancing an activated sludge process including at least one biological reactor. A weighting agent impregnation subsystem is coupled to the biological reactor for mixing biological flocs and weighting agent to impregnate the weighting agent into the biological flocs to form weighted biological flocs. A weighting agent recovery subsystem is configured to recover the weighting agent from the weighted biological flocs and reintroducing the recovered weighting agent to the weighting agent impregnation subsystem.

Abstract: The invention relates to bio-electrochemical systems for treating wastewater, and sour gas produced by anaerobic digestion of organic material. The invention further relates to novel anode/cathode pairing schemes, and electric and hydraulic architectures for use in bio-electrochemical systems.

Abstract: A method of cleaning filtration modules for the treatment of raw water, or wastewater, or activated sludge, is provided by circulating particles in untreated water. The deposits located on the filter membrane outer surfaces are removed by the mechanical action of the particles, without significantly damaging the membrane. Initially, untreated water, wastewater, or activated sludge is chemically-mechanically pretreated. Then the untreated water or wastewater polluted with biologically active material is discharged into a membrane bioreactor system having a filtration unit including at least one filtration tank. At least one submerged filtration membrane module is present in the filtration tank. The untreated water or wastewater in this filtration tank is filled with particles and circulates inside the filtration tank. The particles are non-porous, biologically resistant polymer particles.

Abstract: A treatment system for removing a plurality of pollutants from wastewater includes a removal device for removing a plurality of gross solids from the wastewater, an aeration device for reducing a biochemical oxygen demand (BOD) and a chemical oxygen demand (COD) of the wastewater and a bioreactor containing a bacterial biofilm, said bioreactor including a plurality of cells configured for operation on a predetermined drain fill cycle.

Abstract: A method and apparatus for sanitizing a water dispenser that dispenses water for human consumption is disclosed. The dispenser can be in the form of any dispenser that dispenses water for human consumption employing a reservoir that dispenses water through one or more spigots. Water in the reservoir is sanitized with an air/ozone gas mixture that is transmitted to a porous polymeric diffuser having a central bore and a porous wall. The porosity of the porous wall defines bubble size.

Abstract: A wastewater treatment system is provided having a reactor, first and second bio media and an aeration system. The first bio medium is located proximate an inlet end of the reactor and extends vertically between a top water level and the reactor's floor. The second bio medium is located proximate an outlet end of the reactor and extends vertically between a bottom water level and the reactor's floor. The media are adapted for retaining solids within the reactor as clarified water is withdrawn after treatment. The first bio media is further adapted to act as a baffle thereby causing wastewater to flow generally uniformly into a primary reactor zone. The aeration system includes a plurality of diffusers, some of which may be located adjacent or underneath the bio media and are adapted for promoting the shaking the bio media when activated in order dislodge excessive biomass therefrom.

Abstract: The present invention relates to an anaerobic reactor (10) for the treatment of industrial and other wastewaters at psychrophilic temperatures, the reactor comprising a mixing chamber (12) in which is located, during use, a granular sludge fluidised bed, the reactor further comprising a biofilm chamber (16) fed from the mixing chamber and housing a biofilm colonised pumice-based carrier material, and a separation chamber (18) in fluid communication with the biofilm chamber and in which treated effluent and biogas produced within the reactor are separated.

Abstract: A carbon adsorption vessel for use in a CIP (carbon in pulp) or CIL (carbon in leach) process may be constructed. A slurry is obtained having dissolved (leached) precious metals. The slurry is brought into contact with carbon particles and is passed through a retention screen in the vessel. The dissolved precious metals adhere onto the carbon particles. An air lift pump provides the pressure differential necessary to drive the slurry through the retention screen, wherein the carbon particles are retained by the retention screen and the slurry passes through the retention screen. After passing through the retention screen, the slurry is received in to a receiving vessel that may be situated at, below or above the level of source vessel.

Abstract: An apparatus, system, and process for wastewater treatment. The apparatus can include a basin for receiving a liquid to be treated, the liquid having a direction of flow, and a plurality of pendant sheets for supporting the growth of microorganisms, disposed within the basin and in contact with the liquid, wherein the pendant sheets are oriented parallel to the direction of flow of the liquid.

Abstract: A device for purifying water includes: a reactor housing having an inlet opening for supplying polluted water and an outlet opening for draining the purified water from the reactor housing; hydrodynamic cavitation means arranged in the reactor housing for causing cavitation in the polluted water; main light means for irradiating the polluted water with ultraviolet light, wherein the main light means provide a polychromatic and/or monochromatic pulsed ultraviolet light, which is synchronized selectively with the specific cavitation event(s) in the polluted water.

Abstract: A biofilter is provided. The biofilter comprises a housing; an inlet defining an upstream end of the housing; an outlet defining a downstream end of the housing; a chamber comprising an upstream opening and a downstream opening, the chamber configured to contain a filtration medium; and a counter flow generator for generating a counter flow of water in an upstream direction in the chamber. Related methods and systems are also provided.

Abstract: A method of wastewater treatment is described. The method includes: (i) receiving wastewater produced after anaerobic digestion; (ii) performing a first type of treatment on wastewater to produce wastewater having a first property which is capable of changing; (iii) preventing the first property from changing; (iv) performing a second type of treatment on wastewater; and wherein the first property includes at least one property selected from a group consisting of biochemical oxygen demand (“BOD”) level, dissolved oxygen level, solid content and nutrient level.

Abstract: An apparatus for water filtration, that includes a macroalgal attachment means defining a first macroalgal attachment surface and a bubbling means including, a housing defining a gas inlet and a set of gas bubble ports, and a coupling means. The coupling means secures the macroalgal attachment means to the bubbling means and aligns the first macroalgal attachment surface with the set of gas bubble ports such that a first portion of the gas bubbles to be produced by the gas bubble ports are directed to travel along the first macroalgal attachment surface in contact with the first macroalgal attachment surface.

Abstract: Anaerobic treatment of water is performed under anaerobic conditions with a biofilm formed on a surface of a fluid non-biological carrier in a reaction vessel. Stable high-load treatment is performed by preventing the blockage of the reaction vessel caused by the flotation and adhesion of the non-biological carrier in the reaction vessel and effectively recovering the settleability of the carrier floating owing to adhering air bubbles by simple means. A reaction vessel is charged with a fluid non-biological carrier having a size in the range of 1.0 to 5.0 mm and a settling velocity in the range of 200 to 500 m/h. Part of the carrier that has floated and flowed out of the reaction vessel is fed downward through a pipe having a vertical height of 50 cm or more so as to remove air bubbles adhering to the carrier and is returned to the reaction vessel.

Abstract: A fluid purification unit includes a case including a hollow and a plurality of openings communicating with the hollow to flow a fluid inside into the hollow and outside from the hollow, the case including combining protrusions formed on a first face and concave portions formed on a second face opposite to the first face, each of the combining protrusions having a first cross sectional area and being regularly arranged in a first direction and at a first interval and each of the concave portions having a second area corresponding to the first cross sectional area and being arranged at a second interval corresponding to the first interval.

Abstract: A wastewater treatment system includes wastewater having nitrogen-containing compounds, an anoxic zone having denitrifying bacteria, and an aerobic zone having nitrifying bacteria. The anoxic zone is coupled to the aerobic zone, and wastewater flows from the anoxic to the aerobic zone or vice versa. A fluidized bed heat exchanger configured to accept heat from a heat engine and to transfer the heat from the heat engine to the wastewater is positioned in the aerobic zone or the anoxic zone. The fluidized bed heat exchanger includes particulate media, and fluidization of the particulate media scrubs bacterial growth from portions of the fluidized bed heat exchanger. Treating wastewater can include flowing wastewater having nitrogen-containing compounds into a biological reactor having an anoxic zone and an aerobic zone, and heating the wastewater with heat from a heat engine to facilitate denitrification reactions in the anoxic zone and nitrification reactions in the aerobic zone.

Abstract: A biological wastewater treatment system is provided which is adaptable to small, shop fabricated package plants and large, assembled in place plants, and which can be operated as a secondary treatment, activated sludge process, for suspended solids and BOD removal, or a tertiary treatment, activated sludge process, for suspended solids, BOD, nitrogen and phosphorus removal. The system includes a wastewater pump and an air aspirator-mixer to provide aeration, sludge recirculation and waste, and wastewater recirculation for the secondary and tertiary treatment processes. The aeration system with the air aspirator-mixer transfers oxygen to the wastewater, and is located outside aeration tanks. The wastewater pump and air aspirator-mixer system lends itself to continuous and cyclic aeration and oxic and anoxic treatment processes. The multiple use of the wastewater pump for aeration, recirculation and sludge waste minimizes the number of pumping systems required and eliminates air blowers.

Abstract: This invention relates to the field of human waste handling, treatment and disposal in mobile public carriers. In particular the invention is directed to a self- sustained bio-digester for onboard degradation of human waste.

Abstract: A system for enhancing an activated sludge process including at least one biological reactor. A weighting agent impregnation subsystem is coupled to the biological reactor for mixing biological flocs and weighting agent to impregnate the weighting agent into the biological flocs to form weighted biological flocs. A weighting agent recovery subsystem is configured to recover the weighting agent from the weighted biological flocs and reintroducing the recovered weighting agent to the weighting agent impregnation subsystem.

Abstract: A method is for the treatment of ballast water, in which the ballast water is carried into a ballast tank via a down pipe and in which an underpressure created at the upper portion of the down pipe induces the formation of gas bubbles in the ballast water. Before flowing into the down pipe, the ballast water is carried via a throttling device into a closed container at the upper portion of the down pipe, the closed container having a flow area larger than the flow area of the down pipe.

Abstract: An apparatus for a programmable self sanitizing water dispenser apparatus with a digital controller as well as a programmable method for generating ozone for cleaning the reservoir and the water contained within it. The apparatus includes an anti-spill receiver that houses the controller and that can contain a ozone generator.

Abstract: A system for mixing a gas in a fluid including an inlet section in fluid communication with a fluid source and a gas source, a nozzle, and a flow reverser. The inlet section has a throughbore in which the fluid and the gas combine to form a treated fluid. The nozzle receives the treated fluid from the inlet section and accelerates the treated fluid. The flow reverser has an open end in fluid communication with the nozzle and a closed end. The nozzle is oriented relative to the flow reverser to direct the treated fluid toward the closed end of the flow reverser. The flow reverser receives the treated fluid from the nozzle and mixes the treated fluid.

Abstract: In some embodiments, a wastewater treatment system may reduce contaminants in water. A system may include one or more basins which include a substrate that supports a biofilm. The bacteria used to form the biofilm may be selected to maximize the reduction of contaminants in water. Various components of the wastewater treatment system may be optimized to improve the efficiency and energy consumption of the wastewater system.

Abstract: A process for affecting reductive conversion reactions in a reactor using the palladized bacterial cellulose immobilized on a support for reductive conversion reactions in a reactor.

Abstract: An energy conserving wastewater treatment system capable of being fueled by alternate fuel sources comprises a synthesis gas generator that produces synthesis gas from a fuel and an organic waste digester that produces biogas. A combined synthesis gas and biogas storage reservoir that is in communication with both the synthesis gas generator and the organic waste digester. At least one boiler is in communication with the combined synthesis gas and biogas storage reservoir.

Abstract: Constructed wetland wastewater treatment equipment under low temperature for continuous operation which includes: three-section substrates filled in a constructed wetland, ventilation pipes being arranged in the substrates, a height of a bed of the constructed wetland being higher than a height of the substrates; a double wall being filled with an organic substance used as a barrier at periphery of the constructed wetland; a water distributing pipe disposed at a top of the three-section substrates and a water collecting pipe disposed at a bottom of the three-section substrates; and a water inlet pipe connected to an upper portion at one end of the three-section substrates and a water outlet pipe connected to a lower portion at the other end of the three-section substrates, a water outlet of the water outlet pipe being higher than the height of the bed of the constructed wetland.

Abstract: A water treatment apparatus includes a plurality of meshed tubes made of synthetic yarn and provided with cilia; a plurality of tube stack cages containing the meshed tubes; and an aeration diffuser positioned between the tube stack cages and configured to provide air so that to-be-treated influent water moves to the tube stack cages. The hollow interior of the filter media, i.e. meshed tubes, enables water to move in any direction, and the high porosity maximizes the area for filtering of suspended solids and attachment of microorganisms. The resulting efficiency of removal of suspended solids and soluble organic material is far greater than conventional methods. Arrangement of diffusers in the middle of the reaction tank and between the tube stack cages and aeration by them result in perfect mixing in the reaction tank. The load of suspended solids and soluble organic materials is evenly distributed over the entire filer media.

Abstract: Aqueous liquid having an oxygen demand flows into a treatment vessel where it is treated by suspended aerobic bacterial solids in the presence of dissolved oxygen. A pressurised flow of the treated liquid passes to a clarifying membrane separator effective to separate the flow into a discharge stream of clear liquid and a pressurised recycle stream concentrated in the aerobic bacterial solids. A first oxic gas is employed to scour the membranes and is conveyed away from the membrane separator in the pressurised recycle stream. The pressurised recycle stream is returned to under the surface of the liquid in the treatment vessel. A second oxic gas is introduced either into the pressurised recycle stream or into a further pressurised stream of aqueous liquid flowing into the same volume. The rate of introduction of the oxic gases is controlled with reference to the pH and dissolved oxygen concentration of the liquid in the vessel.

Abstract: The invention provides a system for treatment of wastewater. A pumping system pumps wastewater from a source basin to a recipient basin, while a conduit allows gravitational flow of water from a source basin to a recipient basin when the pumping system is inactive. A controller activates the pumping system to pump wastewater from the source basin to a recipient basin when a wastewater level in the source basin is at a first predetermined height or when a rate of gravitational flow wastewater from the source basin to the recipient basin is below a first predetermined flow rate. The controller also turns off the pumping system when the water level in the source basin is at a source basin minimal level and the water level in the recipient basin is at a recipient basin maximal level. The invention also provides a method for operating a wastewater treatment of the invention, and a pumping system for use in the system of the invention.

Abstract: Described herein are methods and devices for biologically treating water and/or wastewater. The methods and devices for treating waste water may be enhanced using an air-lift device which moves water and/or solids using volumes of air. This device can provide occasional surges of water using large bubbles which are able to move great volume of liquid while minimizing dissolved oxygen transfer to the surrounding liquid. Use of the devices and processes herein provides a simple, eloquent approach to waste water treatment with less operation and maintenance costs than conventional devices and/or processes.

Abstract: An anaerobic digestion device includes a digester body configured to receive organic waste and a plurality of plates coupled to one another so as to divide an interior volume of the digester body into a plurality of compartmentalized chambers. The compartmentalized chambers are movable relative to the digester body to advance a slurry of said organic waste along a length of the digester body. A plurality of ports spaced along the digester body and arranged to vent biogas from the digester body. A storage vessel is configured to receive and store biogas received from the digester body via the ports, and a heating system configured to heat the digester body. The heating system is fuelled by the biogas vented from the digester body.

Abstract: A wastewater treatment facility with a rotating biological contactor (“RBC”) system. The RBC sits in a tank that receives wastewater to be purified. The tank supports a rotatable shaft. One or more stages of rotating disk assembles progressively purify incoming wastewater. Each stage is oriented transversely to the shaft and has a plurality of disk assemblies. Each disk assembly has a number of disks. Each of the disks comprises multiple concentric arcuate segments. The segments are provided with two generally radially extending edges, two circumferential edges that extend between the two radially extending legs, and a front face and a back face. Posts extend from the front and back faces of the disks for stirring wastewater and for offering a site for adherence of biomass suspended in the wastewater. Connecting members interconnect adjacent disks and optionally define a flow channel therebetween.

Abstract: A method of and apparatus for treating liquids flowing in a thin film around a source of wave energy to directly expose the liquid to the wave energy, preferably generated in whole or part by an electrical arc between carbon electrodes. In addition to the wave energy generated by the electrical arc, energy generated by cavitation of the flowing liquid may be used in treating the liquid.

Abstract: Method and system for treating wastewater includes treating sludge with ozone in a plug-flow type reactor to cause lysis of biosolids in the sludge. The ozonated sludge may be provided to an anaerobic or anoxic section of the wastewater treatment system to aid the denitrification processes occurring in the anaerobic or anoxic section of the wastewater treatment system or to other sections of the wastewater treatment system such as a fermenter, an aerobic digester, or an anaerobic digester.

Abstract: The present invention relates to a portable biofilter and degasser.

Abstract: Disclosed herein are systems and processes for treating a Waste Stream comprising biosolids, the Waste Stream provided at varying flow rates and solids concentrations so as to achieve an SOUR of 1.5 mg O2/g/hr or less and an ORP of at least +300 mV. The system includes a biosolids manipulation device to adjust the volume of suspended solids as a percent of the total volume of the Waste Stream to five (5) percent or less; a chemical oxidant feed device to dose the Waste Stream with an oxidant such as chlorine dioxide, ozone, or similar oxidant, and a treatment vessel associated with said chemical oxidant feed device through which said Waste Stream flows, wherein said chemical oxidant feed device and said treatment device are configured so as to achieve a dose rate between 25 and 200 parts per million of the Waste Stream and substantially complete mixing of the oxidant within 30 seconds of dose delivery in the treatment vessel.

Abstract: A wastewater treatment process uses enhanced primary treatment to remove suspended solids from raw wastewater. Primary sludge is treated in a fermenter. Primary effluent is treated by biological nutrient removal (BNR) to produce a treated effluent and waste activated sludge (WAS). The WAS is treated in an anaerobic digester, which also treats sludge from the fermenter. Anaerobic digestate is separated to provide a liquid effluent. The liquid effluent is stripped of phosphorous and returned to the BNR as a source of readily biodegradable carbon. Liquid in the fermenter may also be separated to provide a liquid rich in volatile fatty acids (VFAs). This liquid is returned to the BNR when additional VFAs are required.

Abstract: In some embodiments, a wastewater treatment system may reduce contaminants in water. A system may include one or more bioreactors which include a substrate that supports a biofilm. The bacteria used to form the biofilm may be selected to maximize the reduction of contaminants in water. Various components of the wastewater treatment system may be optimized to improve the efficiency and energy consumption of the wastewater system.

Abstract: An anaerobic waste water purification upflow reactor, includes a vessel (1) containing biomass granules, elements for injecting influent into a lower part of the vessel, a three-phase separator (3) for separating gas, liquid and solid, which is located in an opposite upper part of the vessel, and elements for collecting effluent out of an upper part of the three-phase separator. The three-phase separator (3) includes two solid/liquid settlement zones (12, 13) positioned one above the other in the direction of the upflow (9), above a lower zone provided with gas separation element (10). The reactor includes effluent recirculation elements including element for extracting effluent from the vessel between the two settlement zones and element for re-injecting the extracted effluent into a lower part of the vessel (1).

Abstract: A method for removing contaminants from a fluid-material comprising: providing at least one substrate comprising a three-dimensional knit in an initial configuration made of knitted polymeric fiber which substantially resumes the initial configuration after it is released from stretching or compressing force; and submerging said at least one substrate in a fluidic material for treatment of the fluidic material.

Abstract: A fluid treatment system includes a fluid source, at least one anaerobic reactor vessel, and at least one aerobic reactor vessel. The anaerobic reactor vessel contains retaining a set of retaining structures that are at least partially coated with an anaerobic biofilm. The aerobic reactor vessel contains an aerobic biofilm. When fluid from the fluid source is exposed to the anaerobic biofilm, the anaerobic biofilm removes one or more metal substances from the fluid. When the fluid is exposed to the aerobic biofilm, the aerobic biofilm may cause organic materials in the fluid to metabolize. The system also may include a precipitation reactor that separates divalent metals from the fluid, a settling facility that forms a slurry comprising separated metals, and a neutralization reactor that modifies the fluid to a substantially neutral pH.

Abstract: A wastewater treatment system includes wastewater having nitrogen-containing compounds, an anoxic zone having denitrifying bacteria, and an aerobic zone having nitrifying bacteria. The anoxic zone is coupled to the aerobic zone, and wastewater flows from the anoxic to the aerobic zone or vice versa. A fluidized bed heat exchanger configured to accept heat from a heat engine and to transfer the heat from the heat engine to the wastewater is positioned in the aerobic zone or the anoxic zone. The fluidized bed heat exchanger includes particulate media, and fluidization of the particulate media scrubs bacterial growth from portions of the fluidized bed heat exchanger. Treating wastewater can include flowing wastewater having nitrogen-containing compounds into a biological reactor having an anoxic zone and an aerobic zone, and heating the wastewater with heat from a heat engine to facilitate denitrification reactions in the anoxic zone and nitrification reactions in the aerobic zone.

Abstract: A water treatment unit includes a mixing chamber surrounding the upper end of a riser containing an impeller, Water can be moved from a body of water up through the riser, and out through laterally directed openings into the chamber adjacent to an air inlet, The water moving out the laterally directed openings of the stand pipe, mixes with air drawn in through the air inlet to oxygenate the water, and the oxygenated water exits the chamber into the body of water through one or more water outlets in the lower portion of the chamber due to the head developed by the inflow of water into the chamber. The outward flow of water from the chamber can cause a toroidal or other desired flow of water within the body of water surrounding the water treatment apparatus.

Abstract: A wastewater treatment system includes an outer tank, an aeration chamber partition located within the outer tank and forming an aeration chamber, and a draft tube located within the outer tank and vertically extending into the bottom of the aeration chamber to communicate the aeration chamber with an outer chamber formed. A submerged aerator is located within the draft tube. An inlet communicates influent into the aeration chamber and an outlet communicates effluent out of the outer tank. A scum baffle prevents floating solids from entering the outlet. The outer tank has an effluent weir which supports the scum baffle and the scum baffle has an upward facing flange that supports the aeration chamber partition. An air intake pipe extending to the aerator through an upper end of the draft tube has support members engaging a top of the draft tube to support the aerator within the draft tube.

Abstract: In a sewage treatment plant that includes anaerobic digestion, ammonia-laden filtrate from anaerobic digestion is treated for breakdown of ammonia and optionally for removal of nitrogen, while at the same time thickening the waste activated sludge, preferably with membrane thickeners. This is efficiently done in a two stage process. Liquid filtrate from this subsystem can then be sent back to the head of plant or it can be disinfected. Preferably the filtrate discharged from the subsystem is denitrified, although in some plants it may be desirable to retain some of the nitrates for odor reduction at the head of plant, providing oxygen to neutralize hydrogen sulphide.

Abstract: Uses of a method of producing small bubbles of gas in a liquid include gas transfer in airlift bioreactors and anaerobic digesters, and particle separation. The method uses a source of the gas under pressure, a conduit opening into a liquid and oscillating the gas passing along the conduit. The oscillation is effected by fluidic oscillator, comprising a diverter that divides the supply into respect outputs, each output being controlled by a control port, wherein the control ports are interconnected by a closed loop. Separation of algae from water involves delivering a laminar flow of microbubbles in the range 10 to 100 ?m diameter. Such bubbles also deliver a laminar flow in bioreactors that delivers enhanced liquid flow despite the small bubbles, which improves mixing and also enhances efficiency of gas exchange and retention of the bubbles in the reactor.