Abstract: An automatically controlled wastewater treatment process can include automatically controlling nitrification and denitrification capacity in a water source. The nitrification and denitrification capacity can be automatically controlled simultaneously. In addition, the wastewater treatment process can also include automatically controlling solids retention time (SRT) and biological phosphorus removal in a water source as well as automatically controlling the removal of water from a containment device.

Abstract: The present invention relates to a floating filter module installed in a water treatment apparatus, such as in a public water treatment plant, a village water supply facility, a public sewage treatment plant, a wastewater treatment plant, or a village sewage treatment plant, in order to remove contamination particles.

Abstract: The system and method is directed to improved separation or clarification of solids from a solids-laden liquid and removal of entrained gasses. A liquid to be treated is introduced into the inlet of a solid-liquid separator modified to include one or more sources of vibrational energy. The liquid is directed through a conduit within the separator. This conduit can be configured into a tortuous flow path to assist in the separation of solids from the liquid. Vibrational energy is applied to the flow path, preferably through the flow path conduit. As solids fall out of solution, they are collected. The clarified liquid is also collected. A vacuum can be applied to the system to assist in moving the solid-liquid mixture through the system and to provide vacuum clarification. Electrocoagulation electrodes and gas sparging can also be employed along with height adjustable weirs and an oil accumulator.

Abstract: A method of controlling the operation of a plurality of ultraviolet lamp fixtures in an ultraviolet fluid disinfection system is presented here. The method begins by detecting an operating state, condition, or characteristic of the system. In response to the detecting, the method determines an appropriate lamp regulation scheme to be applied to the plurality of ultraviolet lamp fixtures in the system. The system can then apply the determined lamp regulation scheme to individually regulate operation of the plurality of ultraviolet lamp fixtures.

Abstract: A separator system for separating feed material into a liquid component and a solids component. The separator system has a roller system supported adjacent to a feed chamber. The roller system comprises a base roller and a press roller. Base perforations are formed in the base roller. The base roller is supported such that a first portion of the base roller is in contact with the feed material within the feed chamber such that a liquids portion of the feed material may flow through the perforations in the base roller. The base roller is rotated such that the base roller removes a solids portion of the feed material from the feed chamber in a solids mat on the surface of the base roller. The press roller engages the solids mat on the base roller to force liquids in the solids mat through the base perforations in the base roller.

Abstract: A method and an apparatus for treating a liquid containing impurities may include a filtering chamber configured to permit granular media to interact with liquid containing impurities, thereby removing impurities from the liquid to produce filtrate; a filtrate section for receiving the filtrate; a gas supplying system for delivering gas to the granular media in the filtering chamber for transport of a portion of the granular media to a granular media washer; a reject section in fluid communication with the granular media washer for receiving a reject mixture comprising liquid and impurities from the granular media washer; and a control unit that is configured to determine whether the portion of the granular media is being transported properly based on an amount of reject mixture in the reject section.

Abstract: An oil skimmer system on a marine vessel. The preferred embodiment contemplates a pickup wing pivotally mounted between two hulls in the forward section of the marine vessel, which is formed to collect and direct the oil to the pickup wing. The pickup wing is dynamically repositionable, the pickup wing mount having provided a mechanism for vertically positioning the unit in real time such that the front of the pickup wing is situated just below the water surface, to provide maximum collection of contaminants (in this case, hydrocarbons) floating thereupon. In the preferred embodiment of the invention, the pickup wing has a “teardrop” cross sectional profile, and is configured such that fluid motion over the its forward section, either from vessel motion or fluid current, provides a skimming action, so as to urge the surface contaminants over the wing and into a recovery area, where it is separated from the water and pumped into a collection tank.

Abstract: The present invention relates to a device for treating ballast water using an electrolysis method so as to prevent ship explosions, and to a method for controlling the prevention of ship explosions using same. The device for treating ballast water using an electrolysis method is installed in a ship, wherein the apparatus comprises: a partition wall for separating an explosion danger zone in which a ballast tank is installed, and a safety zone in which the apparatus for treating ballast water is installed; a chlorine-injection tube linearly passing through said partition wall so as to connect the apparatus for treating ballast water to the ballast tank; and a compressor installed in said chlorine-injection tube so as to maintain a positive pressure in said chlorine-injection tube by transferring water into said chlorine-injection tube, even when an operation using the chlorine-injection tube is stopped.

Abstract: A method and system for treatment of flow-back and produced water from a hydrocarbon well in which fracturing operations are carried out using a phase separation and creating of positive charge in the water.

Abstract: This disclosure is directed to the regulated injection of a chemical(s), solution(s) or material(s) hereafter referred to as chemicals into stormwater runoff, other surface waters or other fluid streams to promote the removal of a pollutant(s) or to alter the properties of the water. Specifically, and depending upon the types of chemicals injected, the physical, chemical and/or biological properties of the water can be altered. The invention provides a passive system to alter stormwater runoff or other surfaces. The system may be deployed at a remote site, such as a construction site, and implemented with minimal or zero external power requirements.

Abstract: Apparatuses and methods for level control in a fluid purification apparatus. The apparatuses and methods include a fluid purification apparatus and a level sensor that regulates operation of the fluid purification apparatus. The level sensor may further operate a bypass valve or a heater.

Abstract: The invention is a method for treating fluid in a main fluid reservoir, e.g., a pool, spa, or water tank, etc., using ozonated air. A fluid filter is placed in an auxiliary fluid reservoir located in or next to the main fluid reservoir. An ozone generator pumps a combination of ozone and air into the auxiliary reservoir. Fluid in the auxiliary reservoir passes through a filter and back into the main reservoir without the use of any fluid pump. More specifically, a vertical lift tube is placed beneath the auxiliary fluid reservoir so that the open top of the lift tube is within the auxiliary reservoir. Fluid from the main reservoir is fed to the bottom of the lift tube. Ozone and air from the ozone generator is also piped into the lift tube near its bottom. The fluid flows through the filter due to the effect of ozone and air bubbles released by a diffuser at the bottom of the lift tube.

Abstract: The device described in the present invention can separate fine solid particles in suspension in a viscous liquid, withdrawing a clear liquid from the top of the device, and a dense liquid charged with solid particles is withdrawn from the bottom. The invention also concerns the application of this device to the separation of catalyst particles in a liquid phase Fischer-Tropsch synthesis process.

Abstract: A system for monitoring water chemistry of a recreational water installation includes a sensor configured to detect bather load in the recreational water installation and a controller configured to determine a required adjustment to the water chemistry of the recreational water installation based upon the detected bather load.

Abstract: An apparatus and a method for filling a container containing a dry powdered salt concentrate for use in dialysis with purified fluid and removing the trapped air or gases generated during the filling of the container, while maintaining the required fluid level in the container and without the need for evacuating gases from the container prior to filling.

Abstract: Skimmers, barges and related methods recover heavy oil or bitumen from contaminated water environments such as tailings ponds. The skimmer has an articulated mesh-like conveyor driven around a drum by a drive sprocket. A pusher mechanism discharges bitumen or heavy oil from cavities in the conveyor. In one embodiment, the skimmer includes an automatic depth control system. In other embodiments, knife-edged shear plates remove heavy oil or bitumen adhering to the conveyor and drum. A barge may incorporate multiple parallel skimmers. The barge may include a bitumen-transfer pump having an annular fluid-injection flange that generates an annulus of lubricating fluid inside a discharge hose. A method of skimming heavy oil or bitumen involves using a skimmer that automatically adjusts its elevation or depth based on a control signal generated by a depth sensor. Another method recovers and transfers bitumen by lubricating the discharge hose using the annular fluid-injection flange.

Abstract: The invention is directed to a purifying device for sludge under water and a method for operating the same. The device includes a main fixing frame having an accommodating portion assess to the outside, a hollow liquid container in the accommodating portion, wherein the liquid container is provided with a liquid-flow hole and at least a backwash hole, multiple filters on the liquid container, and a pump connected to the liquid-flow hole at the liquid container through a liquid pipeline. The method includes steps: moving the liquid container having the filters to an area having a liquid to be filtered; leading the liquid to flow into the liquid container through the filters filtering out solid particles contained in the liquid; and leading a fluid to flow into the liquid container such that the filters can be backwashed accompanying with an external cleaning device if the filters are clogged.

Abstract: A method for controlling treatment of an industrial water system is disclosed. The method comprises the steps of providing an apparatus for controlling delivery of at least one treatment chemical, the apparatus comprising at least one sensor and an electronic input/output device carrying out a protocol; measuring a parameter of the industrial water system using the at least one sensor; relaying the measured parameter to the electronic device; adjusting the protocol based on the measured parameter; delivering a concentrated treatment chemical into a stream of the industrial water system according to the adjusted protocol, the concentrated treatment chemical comprising an active ingredient, the active ingredient traced as necessary, the active ingredient having a concentration; repeating the measuring, the adjusting, and the delivering; and optionally repeating the steps for n-number of parameters, n-number of active ingredients, and/or n-number of concentrated treatment chemicals.

Abstract: A hemofiltration system and method for pumping blood from a patient's blood stream into an access line, introducing an anticoagulant solution into the pumped blood, filtering the pumped blood and delivering it to a return line, introducing a substitution fluid into the pumped blood, introducing a calcium and magnesium solution into the blood traveling through the return line, and returning the blood back to the patient's blood stream.

Abstract: The present invention provides a water purification apparatus and method using a pressurized micro-filter preprocessed with a coagulation inclined-plate sedimentation reservoir and a pore-control fiber filter for improvement of a recovery rate, which removes the dissolved organic materials and the turbidity of raw water through a preprocess by a flash mixer, a two-stage coagulation reservoir and an inclined-plate sedimentation reservoir, thereby making it possible to reduce the use of coagulants, the generation of sludge by-products, the inflow load of membranes, and the facility size in comparison with the conventional standard water purification processes.

Abstract: The present invention discloses a system and method for self-cleaning filters without having to open the filter housing. Wash nozzles are integrated with the filter housings such that when the filters are clogged, both back-wash and regular washing can be performed with practically no down time. Moreover, without opening the filter housing, the hazardous components of the fluid to be filtered can be contained and dealt with before they escape the filter housing, thereby significantly reduces the environmental impact and harm to the working crew.

Abstract: The present invention relates to a device for separating fluid mixtures, in particular for separating oil and water in a vacuum container, into which the fluid mixture is injected by means of an adjustable truncated-cone round jet nozzle.

Abstract: A separation unit for separating oil from oily water has a first oil to water ratio and the separation unit comprises a body which defines an inner chamber and which has a first end-wall and an opposite second end-wall and first and second side-walls that extend between the first end-wall and the second end-wall. The inner chamber is at least partly delimited by the first end-wall and the second end-wall, the first side-wall and the second side-wall. The separation unit further comprises a third wall which constitutes a separation wall extending from the first end-wall towards the second end-wall and divides the inner chamber into a first and a second sub-chamber. An inlet is defined at the first side-wall and the first end-wall and a first outlet is defined at the second side-wall and the first end-wall. A passage is defined at the third wall and the second end-wall and a fluid path from the inlet which passes through the first sub-chamber and the passage and the second sub-chamber to the first outlet.

Abstract: A method of recording and monitoring the operation and status of devices operating to purify water employed in the operation of a dialysis clinic, by providing a software program that monitors water purification devices that include a water softener, brine tank and reverse osmosis machine. This computer program is a data logging system that enables the user to monitor and record the status and performance of water purification equipment that is housed and used in a dialysis clinic. The software program will be used by technicians that work in three shifts on a daily basis to ensure that the water being purified for dialysis treatment is within an acceptable range of purity. This software replaces a paper logging system and is more versatile in security, accuracy, function and reporting.

Abstract: A stormwater filtration system includes one of a filter cartridge structure or a filter basket structure. The structure includes an internal collection space surrounded by a filter media bed, an outlet opening toward the bottom of the internal collection space for delivering water out of the structure, and a valve assembly associated with the outlet opening. The valve assembly is configured to provide a variable flow out of the outlet opening according to level of water within the internal collection space.

Abstract: A method for keeping constant a pH of a medical liquid being drained from a container includes adding CO2 and at least one other gas or gas mixture to the container during the draining of the medical liquid. An apparatus associated with the method has an outflow for the medical liquid, at least one inflow for the CO2 and an inflow for the other gas or gas mixture, and an electronic control for the determination and automatic supply of a quantity of the CO2 during the draining of the medical liquid.

Abstract: A pump in fluid communication with the outlet of a fluid purification apparatus. A pump may furthermore provide fluid to the inlet of the fluid purification apparatus. An embodiment includes a fluid driven rotating inlet device in fluid communication with the inlet of the fluid purification apparatus and an outlet impeller in fluid communication with the outlet of the fluid purification apparatus.

Abstract: A method for monitoring and/or controlling the process flow of a waste water system having waste water in waste water lines, comprising the steps as follows: measuring volume flow of waste water at a location remote from a waste water cleaning plant; measuring at least one additional waste water relevant parameter at the location remote from the waste water cleaning plant; evaluating the measurement data and detecting system relevant events; and undertaking measures in the waste water cleaning plant and/or at the location remote from the waste water cleaning plant as a function of the system relevant event. Furthermore, the invention relates to a system for performing the method.

Abstract: A process and an apparatus are provided for controlling a filtration plant having at least one vacuum filter, at least one vacuum pump and at least one filter tank, by which a medium that is to be filtered and that includes solid particles and liquid is separated into a concentrate including predominantly solid particles and a filtrate comprising predominantly liquid. The method may include: determining at least one first parameter of the filtration plant in the form of a residual moisture content of the concentrate and/or of a density of the filtrate as a function of time or a second parameter of the filtration plant, forming a derivative of the at least one first parameter after the time or the second parameter as at least one first characteristic, determining the sign of the at least one first characteristic, and controlling the filtration plant as a function of the determined sign.

Abstract: A unitary water treatment system for filtering and purifying untreated water is disclosed that has a filtration compartment, a transfer compartment, and a purification compartment. The untreated water flows into the filtration compartment, then into the transfer compartment, and then into the purification compartment. A fill valve is provided at the inlet of the water treatment system; a transfer valve is provided between the transfer and purification compartments; and a drain valve is provide at the exit of the purification compartment. A UV lamp is placed in the center of the purification compartment to expose water trapped in the purification compartment to light in a desired frequency range to kill bacteria and viruses.

Abstract: A fryer apparatus includes a cooking chamber, at least one heating element in the cooking chamber, a filter pan that filters cooking medium from the cooking chamber, a drain valve that controls flow of cooking medium from the cooking chamber, and a filter pump that pumps filtered cooking medium from the filter pan to the cooking chamber. Inlet orifices are disposed in the cooking chamber, and selectively eject filtered cooking medium into the cooking chamber. A controller controls the drain valve to adjust the rate of flow from the cooking chamber, and selectively activates at least inlet orifice of the plurality of inlet orifices to eject filtered cooking medium into the cooking chamber. The controller is configured to control the drain valve and the selective activation of the at least one inlet orifice to maintain a substantially constant level of cooking medium in the cooking chamber throughout a filtering operation.

Abstract: An in-line flow separator comprises an uphill section of pipeline which, in use, carries a gravitationally stratified flow of a first liquid and a second denser liquid. The second liquid forms a sump extending uphill from the foot of the uphill section, and an interface between the first and second liquids on the uphill section is inclined from the horizontal. An extraction port in the pipeline extracts the second liquid from the sump.

Abstract: Apparatus and method for increasing the concentration of a chemical substance in a fluid comprise a micro-fluidic elongated channel formed in a substrate, with the channel being in fluid-flow communication with an ambient region along its elongated dimension. In general, the fluid includes first and second chemical substances having different vapor pressures. The apparatus includes an evaporation controller for increasing the evaporation rate of the fluid from the channel into the ambient region, thereby increasing the concentration of the lower vapor pressure (LVP) substance in the portion of the fluid remaining in the channel and increasing the concentration of the higher vapor pressure (HVP) substance in the portion of the fluid evaporated into the ambient region.

Abstract: The present invention relates to a filtration method, a filter-incorporated tip and a filtration device, and its object is to perform efficient and swift isolation of a target substance.

Abstract: An apparatus and a method for filling a container containing a dry powdered salt concentrate for use in dialysis with purified fluid and removing the trapped air or gases generated during the filling of the container, while maintaining the required fluid level in the container and without the need for evacuating gases from the container prior to filling.

Abstract: An automatic draining system is provided. The system includes a floating valve having a density less than a first fluid and greater than a second fluid. The floating valve has a floating position that allows the first fluid to pass through a floating valve opening when the floating valve compartment is filed with the first fluid, and a sealing position that prevents the first and second fluids from passing through the floating valve opening when the floating valve compartment is not filled with the first fluid. Also included is a solenoid valve in fluid communication with the floating valve compartment. The solenoid valve has a solenoid opening that is open when the solenoid valve is energized and is closed when the solenoid valve is de-energized. Further included is a filter media downstream of the solenoid valve that filters the first liquid prior to the first fluid exiting the system.

Abstract: The disclosure relates to a separation process. An aerated inlet mixture of fluid and solids is fed to a flotation separation vessel and is separated into an upper float layer and a lower clarified layer. The upper float layer is withdrawn from the vessel when the height of the upper float layer exceeds the height of an overflow conduit and forms a concentrated solids effluent. The lower clarified layer is withdrawn from the separation vessel as a clarified fluid effluent. The separation process is performed continuously using a control process that maintains a relatively stable distribution between the lower clarified layer and the upper float layer. The control process is a closed loop process that monitors the instantaneous height of the vessel contents and computes an error function based on the instantaneous height and a set-point height. The error function is used to periodically adjust the outlet flowrate of the clarified fluid effluent. The resulting process has improved stability (e.g.

Abstract: Disclosed and claimed is a method of removing contaminants from a process stream or stabilizing a system parameter in the process stream. The method includes providing a filtration system in communication with a controller, wherein the controller is operable to automatically initiate a flow from the process stream into the filtration system when the system parameter of the process stream is within above an upper threshold value and/or below a lower threshold value; and activating the filtration system, wherein the flow comprises a flow rate through the filtration system and the controller is operable to adjust the flow rate.

Abstract: A method and apparatus is provided for water filtration of a milk of lime solution that contains water, impurities, and grit particles, in which the milk of lime solution enters a vessel, and wherein turbulence is created in the vessel, by which larger grit particles settle out of the milk of lime solution, to form a bed of grit particles in the lower end of the vessel, such that grit particles and impurities are filtered from the lime-treated water that comprises a milk of lime solution, with water then being drawn off, that may be discharged out one or more dosing locations and/or recycled back for further filtration, as may be desired.

Abstract: A disc filter having a controller for controlling or minimizing effluent surges is provided. The disc filter is operative to carry out a method or process for controlling the flow of effluent produced by the disc filter. The basic method entails sensing one or more process variables that are a function of the effluent, and based at least in part on the sensed process variables, the disc filter controls the flow of the effluent by implementing various control functions such as: 1) rotating the rotary filter discs of the disc filter one revolution or less without backwashing; 2) rotating the rotary filter discs more than one revolution at a relatively slow speed without backwashing; 3) rotating the rotary filter discs for one revolution or more at a relatively slow speed while backwashing; 4) rotating the rotary filter discs at a relatively high speed with or without backwashing; and 5) rotating the filter discs one revolution or more and periodically backwashing.

Abstract: The present invention is directed to a method and apparatus for improved separation or clarification of solids from a solids-laden liquid. Entrained gasses can also be removed. A liquid to be treated is introduced into the inlet of a solid-liquid separator modified to include one or more sources of vibrational energy. The liquid to be treated is directed through a conduit within the separator. Preferably the conduit within the separator is configured into a tortuous flow path to assist in the separation of solids from the liquid. Vibrational energy is applied to the flow path, preferably through the flow path conduit. As solids fall out of solution, they are collected. The clarified liquid is also collected. A vacuum can be applied to the system to assist in moving the solid-liquid mixture through the system and to provide vacuum clarification. Electrocoagulation electrodes and gas sparging can also be employed.

Abstract: A rainwater collection system is described which includes generally a rainwater routing system and a collection unit. The rainwater routing system may comprise a first flush diversion unit designed to discharge to a run-off path, an initial amount of rainwater such that initial particulate matter from rooftops, etc., are not collected. The rainwater routing system may comprise a pre-treatment unit, the pre-treatment unit designed to remove particulate matter from the rainwater. The collection unit of the rainwater collection system comprises a storage tank having an internal day tank compartment. The described rainwater collection system allows for the collection of rainwater with a substantially reduced amount of particulate matter.

Abstract: When a separation membrane (3) is washed with a chemical solution that is a sodium hypochlorite solution, which has a high concentration, diluted with membrane treated water stored in a chemical solution tank (6), an ammonic nitrogen concentration in membrane-treated water is monitored with a monitoring device (9), and a control device (8) controls a chemical solution dosing pump (7) using the concentration measured by the device (9) to adjust a dilution rate. Thereby, even when water quality of membrane-treated water varies, a sodium hypochlorite concentration in backwashing water can be retained constant, and fluctuation in the chemical washing effect can be prevented.

Abstract: Systems, apparatus and methods are described that control and manage water collection and treatment. One or more sensors monitor and measure levels of contaminants, other chemicals and or environmental conditions in a well of a tank, well and/or collection station and/or in inflow and/or outflow mains. An additive that can include one or more of ozone, oxygen, a bioagent, bleach, peroxide and other chemicals, and selected to treat chemicals and/or contaminants in water, can be mixed with water in the well and the main. An infusion assembly deployed within the tank is adapted to mix the water and additive into a body of water in the well. A processor configured to control the rate at which the additive is provided to the infusion assembly or force main based on measurements of contaminants received from the first and second sensors.

Abstract: A grey water dividing and treatment system is provided. A drain system of the grey water dividing and treatment system receives grey water from a grey water producing source. A grey water dividing apparatus of the grey water dividing and treatment system divides the grey water received from the drain system into a number of cells, and determines a contamination level of each of the cells. Grey water treatment tanks of the grey water dividing and treatment system receive the grey water from the grey water dividing apparatus based on the determined contamination level of each of the cells and treat the grey water.

Abstract: Embodiments of the invention are directed toward a novel pressurized vapor cycle for distilling liquids. In an embodiment of the invention, a liquid purification system is revealed, including the elements of an input for receiving untreated liquid, a vaporizer coupled to the input for transforming the liquid to vapor, a head chamber for collecting the vapor, a vapor pump with an internal drive shaft and an eccentric rotor with a rotatable housing for compressing vapor, a condenser in communication with the vapor pump for transforming the compressed vapor into a distilled product, and an electric motor with motor rotor and magnets hermetically sealed within the fluid pressure boundary of the distillation system.

Abstract: Skimmers, barges and related methods recover heavy oil or bitumen from contaminated water environments such as tailings ponds. The skimmer has an articulated mesh-like conveyor driven around a drum by a drive sprocket. A pusher mechanism discharges bitumen or heavy oil from cavities in the conveyor. In one embodiment, the skimmer includes an automatic depth control system. In other embodiments, knife-edged shear plates remove heavy oil or bitumen adhering to the conveyor and drum. A barge may incorporate multiple parallel skimmers. The barge may include a bitumen-transfer pump having an annular fluid-injection flange that generates an annulus of lubricating fluid inside a discharge hose. A method of skimming heavy oil or bitumen involves using a skimmer that automatically adjusts its elevation or depth based on a control signal generated by a depth sensor. Another method recovers and transfers bitumen by lubricating the discharge hose using the annular fluid-injection flange.

Abstract: A separator for separating F.O.G. from an effluent that contains F.O.G. includes a tank, an inlet to the tank for receiving effluent that contains F.O.G., and an outlet to allow grey water to leave the tank. The tank has a size to enable stratification of a layer of F.O.G. present in the tank on water in the tank, and first and second thermocouples are positioned at differing levels in the tank. Conductors couple the thermocouples to sensors, and differing voltages in the thermocouples can be sensed to determine if the thermocouples are surrounded by F.O.G. or water.

Abstract: The present invention relates to a porous media-mediated high speed filtration device for easy backwash, wherein the inflow water to be filtered is guided to an upper portion of the high speed filtration device and is filtered by downflow and porous media are backwashed for maintaining optimum filter efficiency by blocking the flow of inflow water and water to be treated after sensing the level of the inflow water or the change in the flux of the water to be treated, supplying backwash water and/or air by upflow through a backwash equipment to separate pollutants in the porous media by the collision and friction between the porous media by flowing of the porous media through the stream of the backwash water, placing the porous media in a stationary location, and discharging the pollutants through a discharge pipe of the high speed filtration device before the pollutants settle. In addition, the present invention comprises a backwash method of the high speed filtration device using porous media.

Abstract: The present invention concerns a filter (5) for a return line (L1, L2) for hydraulic oil to a hydraulic tank (2), which filter (5) comprises a filter element (11). According to the invention, the filter (5) is arranged to filter the hydraulic oil through the filter element (11) when the hydraulic oil lies below a first oil level (H1) in the filter (5), and the filter (5) comprises an arrangement (15) to lead the hydraulic oil past the filter element (11) when the oil level (H) in the filter (5) exceeds the first oil level (H1).