Abstract: A polymer-free method and self-draining self-cleaning apparatus for treatment of water with high total dissolved solids including optional pretreatment, precipitation/flocculation, and separation. The pH is raised by addition of caustic soda and/or soda ash. In a vertical clarifier silo, the feed is gently mixed to cause dissolved solids to precipitate and agglomerate to form suspended flocculates. The clarifier includes an internal mixer surrounded by a cylindrical tube diffuser. Rotation of the mixer provides gentle dual circulation patterns within the clarifier that allow for flocculates of a predetermined size to settle from suspension. The clarifier may also include one or more vertical recirculation lines to recirculate some of the heavier flocculates at the bottom of the vessel into the mixer chamber to enhance precipitation via the seeding effect. The suspended flocculates are stripped from the feed water in a centrifugal separator. The clarifier silo may be trailer mounted for rapid deployment.

Abstract: Disclosed herein is an apparatus and method for adding a lubricating additive to a diesel fuel.

Abstract: Ballast water treatment apparatus and methods for preventing foreign aquatic invasive species form entering marine ecological zones by translocation in ship's ballast water. The apparatus includes a housing, a filter member, and UV water treatment chambers. Methods include use of a ship's fire hydrant system or ballast water discharge port for moving ballast water from the ship's ballast tanks into the apparatus for filtration and treatment. In-port service vessels and barges as well as dock-side service vehicles are equipped with the various treatment and filtration apparatus to provided in-port or dock-side ballast water treatment services. Related methods are also provided.

Abstract: The invention relates to a method and apparatus for removing impurities from waste water by electroflotation. The waste water to be cleaned is conducted through an electrolytic cell. Electrolysis is performed between two electrodes (1, 2) of different electronegativities, such that the more electronegative electrode (1), which is non-wearing in a cleaning process, is used for producing hydrogen gas and hydroxyl ions from water. The less electronegative electrode (2), which is an active, wearing electrode in a cleaning process, is used for producing metal ions in a solution to be cleaned. In addition to this basic reaction, a desired oxidation-reduction reaction is initiated in the cell in a strictly controlled electric field for removing one or more designated impurities from cleaned water.

Abstract: A portable water treatment system and apparatus is disclosed that can effectively and efficiently treat aqueous fluids by quickly and reliably adjusting and controlling the free residual level of disinfectants, contaminants or additives through the addition of one or more treating agents such as oxidizing chemicals and/or other special-purpose additives, and that can continuously store, log, retrieve and report the related fluid composition data and other operating parameters on a real-time basis at either the use site or a remote location. A preferred use for the subject system and apparatus is managing the chemistry of disinfectant, contaminant and/or additive levels in aqueous fluids used in hydraulic fracturing operations, and controlling the free residual levels of the disinfectant or contaminants within the fluids, including fluids maintained in frac tanks during temporary cessation of a hydraulic fracturing operation.

Abstract: Methods and apparatus of embodiments of the invention relate to treating water including contacting a liquid stream with a source comprising inorganic and/or divalent ions and separating the stream into an effluent and a fluid comprising less sulfate than the stream, wherein the effluent comprises more sulfate and more inorganic and/or divalent ions than the stream. Methods and apparatus relate to treating water including a reaction unit comprising an inlet for feed fluid and an inlet for inorganic and/or divalent ions and a separator unit comprising an inlet for output from the reaction unit, an outlet for effluent, and an outlet for fluid comprising less sulfate than the feed fluid. Some embodiments include introducing the fluid comprising less sulfate than the stream into a subterranean formation.

Abstract: Methods and apparatus of embodiments of the invention relate to treating water including contacting a liquid stream with a source comprising inorganic and/or divalent ions and separating the stream into an effluent and a fluid comprising less sulfate than the stream, wherein the effluent comprises more sulfate and more inorganic and/or divalent ions than the stream. Methods and apparatus relate to treating water including a reaction unit comprising an inlet for feed fluid and an inlet for inorganic and/or divalent ions and a separator unit comprising an inlet for output from the reaction unit, an outlet for effluent, and an outlet for fluid comprising less sulfate than the feed fluid. Some embodiments include introducing the fluid comprising less sulfate than the stream into a subterranean formation.

Abstract: By adding an iron salt, the sedimentation property, the concentration property, and the filtration property of sludge in an activated-sludge mixed liquor in a biological treatment tank are effectively improved and treated water of high quality is efficiently provided. When an iron salt such as ferrous chloride, ferric chloride, or polyferric sulfate is added to organic wastewater and the organic wastewater is biologically treated, the iron salt is added to the organic wastewater and mixing is conducted; and the water mixture is mixed with activated sludge and biologically treated. By mixing organic wastewater and an iron salt at a pH close to an optimum pH for ferric hydroxide in advance, the turbidity of the treated water due to the formation of iron oxide or ferrous carbonate is suppressed.

Abstract: Wastewater treatment systems, methods and apparatus for polishing a wastewater stream comprising a plurality of contaminants are provided. One system includes a vessel containing a plurality of natural media filtration agents selected to remove selected ones of the plurality of contaminants from the wastewater stream. In one embodiment, the vessel includes a bed of bauxite residue and at least one other natural media filtration agent. In another embodiment, the vessel includes a bed of compost and at least one other natural media filtration agent. The vessel includes a wastewater inlet that is in fluid communication with one or more of the natural media filtration agents. The vessel includes a wastewater outlet that is in fluid communication with one or more of the natural media filtration agents.

Abstract: A blood treatment system is primed with a replacement liquid that flows directly into the access line of the blood circuit. The replacement liquid may be replacement fluid or blood stored in the replacement bag or the pre-blood pump (PBP) bag. These replacement liquids from the replacement and PBP bags are also used during blood treatment. These replacement liquids are blood or a replacement fluid and, particularly, have electrolyte levels the same as or similar to the electrolyte levels in the vascular blood of the patient.

Abstract: A filter apparatus is provided. The filter includes a filter element that carries an additive for the treatment of coolant filtered by the filter. The additive is contained within an additive chamber. A dissolvable seal is positioned over an outlet of the filter to prevent the undesirable leakage of additive during non-operation.

Abstract: A purifying device adapted to perform a method of photochemical elimination of xenobiotics present in water. The purifying device comprises a photochemical reactor unit having at least one inlet for contaminated water and one outlet for purified water, it provides a flow path for continuously flowing water from said inlet to said outlet, and is equipped with a radiation source module providing ultraviolet radiation in a wavelength range ranging from 100 to 280 nm. The purifying device further comprises at least one membrane filtration unit designed to perform ultra filtration and connected upstream of said photochemical reactor unit via said inlet and at least one device for supplying air or dioxygen to the water comprised in the photochemical reactor unit. Further, a purification method is provided, using the device of the invention.

Abstract: A portable fluid ozonation apparatus includes a container for treating and storing fluid, a filter that attaches to the container and an ozone generator. In use, a fluid is dispensed into the container and optionally passed through the filter. At this point, power is supplied to the ozone generator which operates for a period of time necessary for disinfecting the fluid. Additives and post filters can be utilized in conjunction with the ozonation apparatus in order to obtain sufficient purified fluid within a short time frame.

Abstract: A pressurized wastewater effluent chlorination system including a treatment tank defining a contact chamber and an aeration chamber. The treatment tank receives wastewater effluent. The system includes a pressure vessel within a liquid chlorine storage container positioned in or near the treatment tank. Preferably, the pressure vessel is a floating vessel having a check valve at its bottom, enabling the vessel to fill with a predetermined amount or measured charge of chlorine depending on the position of a float on the vessel. In response to a timer control or float switch, a valve operates to communicate air pressure from a compressor to the vessel to displace the measured charge of liquid chlorine into the wastewater effluent in the contact chamber. Effluent flow and air discharge into the contact chamber enhances mixing of the chlorine and the effluent.

Abstract: An apparatus for treating liquid includes a tank having a water inlet for receiving water, a treated water outlet for outputting treated water and a flow path between the inlet and the outlet. An injection section of the tank is located along the flow path of the tank with an outlet toward a bottom of the tank. Ozonated liquid containing ozone microbubbles is injected through an injection manifold positioned within the injection section of the tank. The ozone microbubbles adsorb to impurities in the ozonated water. A separation section of the tank is positioned downstream of the outlet of the injection section. The separation section has a contact surface such that the ozonated water travels upward to contact the contact surface and such that at least a portion of the ozone microbubbles adsorb to the contact surface.

Abstract: A method and apparatus for conducting supercritical wet oxidation reactions wherein any precipitated solids do not contact the solid side walls of the containment vessel so as to prevent any of these precipitated solids from adhering to or corrode the vessel walls is provided. To do this, a controlled, continuous flow of clean fluid, preferably under supercritical conditions, is introduced to the process so as to form a film-like, clean fluid surface between the physical containment vessel walls and the supercritical wet oxidation reactants.

Abstract: A wastewater treatment system comprising a first chamber adapted to receive wastewater and arranged to perform a first treatment process (e.g., aerobic and/or anaerobic processes), a second chamber positioned to receiving wastewater from the first chamber and including an ozone contactor assembly that infuses ozone into the second chamber, and a storage tank positioned to receive treated water from the second chamber. The ozone contactor assembly comprises a first conduit having an intake, a discharge, a downwardly-angled portion, and an upwardly-angled portion (e.g., U-shaped). An ozone generator is positioned to provide ozone to a lower portion of the first conduit (preferably near the bottom of both the downwardly- angled portion and the upwardly-angled portion). The ozone contactor assembly can include additional conduits structured similar to the first conduit and feeding into each other, and each including an ozone generator.

Abstract: A method for treatment of an aqueous oily solution includes combining the aqueous oily solution with one or more miscible organic solvents to produce a mixture of precipitated solids and a liquid phase; separating the precipitated solids from the liquid phase; separating the liquid phase at least into an organic phase and an aqueous phase; and removing at least a portion of one or more oily substances from the organic phase. A system for treatment of an aqueous oily solution is also presented.

Abstract: The invention concerns a water treatment device comprising a reactor (1) and means for injecting (2) at least one reagent into said reactor, characterized in that it comprises means for supporting said injection means mobile relative to said reactor (1) between an active position whereby the injecting means (2) are arranged inside said reactor and a retracted position whereby the injecting means (2) are brought outside said reactor.

Abstract: Systems and associated methods for treating contaminant-containing wastewater are provided. The systems generally include a reducing zone for reducing the oxidation-reduction potential of the water and a clean-up zone comprising zero valent iron for removing at least a portion of the contaminant from the contaminant-containing water. The systems are operable to remove one or more contaminants from the contaminant-containing water and are operable for extended durations without clogging due to the formation of iron hydroxides.

Abstract: The invention relates to a device (2) for purifying water (6, 9) contaminated with organic substances, that is drained or collected from filters, especially fuel filters (4) or elements of a fuel system. Said device is characterised in that hydroxyl radicals are formed from the water (6, 9) by means of a separating device (8), said hydroxyl radicals oxidising the impurities, especially organic substances, as much as possible, and converting them into compounds such as CO2.

Abstract: A method and apparatus for treating slurries of organic solids is disclosed. A slurry of organic solids is admixed with hydrogen peroxide, followed by exposure to microwave irradiation resulting in the heating of the mixture and enhanced hydrolysis of the organic solids. The treated slurry of organic solids can then be further treated in a variety of downstream processes, including solid separation, digestion and fermentation. The supernatant portion of the treated slurry of organic solids can be a source from which to recover compounds such as nutrients (for example nitrogen, phosphate, potassium, magnesium, calcium) or industrial organic compounds (such as acetic acid, propionic acid, butyric acid), or as a source of readily biodegradable organic compounds for supplementing a biological wastewater treatment process, digester or fermenter.

Abstract: Disclosed are improved methods and apparatus for radiolabeling, particularly methods and apparatus for large scale in-line radiolabeling of products, such as proteins and antibodies.

Abstract: A water reaction tank for reacting water containing suspended solids with a flocculant includes a housing having an input, an output, and a water flow path between the input and the output. The flow path has a mixing section and a reaction section. Sealable flocculant ports are provided for inserting a flocculant into the mixing section of the housing. Each of the mixing section and the reaction section contains baffles. The mixing section baffles encourage turbulent flow to increase contact with the flocculant, and the reaction section baffles encourage turbulent flow and increase the length of the water flow path.

Abstract: A method and apparatus is provided for treating water with already-slaked lime to arrive at a lime slurry that is in a solution or suspension, and delivering the thus treated water to a separating device which separates grit particles therefrom, to recover a high quality lime/water solution or suspension. An automated system controls the addition of lime and water to a lime mixing vessel. An acid wash system is provided which comprises an automated method and apparatus for removing scale buildup, for delivering an acid wash solution to the lime mixing vessel, the lime slurry holding tank and/or the delivery system, or any of them, thereby dissolving the scale buildup.

Abstract: A grey water treatment system for use in conjunction with a water softener, including a grey water holding tank including a first inlet configured to receive grey water and a second inlet configured to receive spent brine from the water softener. The spent brine is mixed with the grey water in the holding tank to flocculate suspended solids in the grey water for subsequent removal.

Abstract: A method of removing mineral hardness of water comprises selecting a mineral hardness solubility constant modifier capable of at least partially precipitating insoluble mineral hardness material from water containing mineral hardness. A pressurized flow of the water containing mineral hardness is generated. The mineral hardness solubility constant modifier is added to the pressurized flow of water containing mineral hardness to form water bearing precipitate mineral hardness. The water bearing precipitate mineral hardness is filtered to at least partially remove the precipitated insoluble mineral hardness material from the water bearing precipitate mineral hardness to form post-filtered water.

Abstract: A process for removing microorganisms and/or precursors of disinfection by-products from a medium sought to be treated comprising treating the medium with one or more elements capable of forming an oxide, a hydroxide, and/or an oxyhydroxide through corrosion is disclosed. A system for effecting the removal or inactivation of microorganisms and/or disinfection by-product precursors is also contemplated.

Abstract: A system and method includes an aeration subsystem that excites enzymes in the liquid waste passing through the septic system. The aeration subsystem includes a compressor section that compresses the liquid waste and an injector section that injects oxygen into the compressed liquid waste. The system further includes a driver subsystem for driving the compressor section and a control subsystem for activating and deactivating the driver subsystem.

Abstract: A system for producing emulsions includes a liquid supply system, an emulsification system in liquid connection with the liquid supply system to receive a first liquid and a second liquid from the liquid supply system while in operation to be used to produce an emulsion therefrom, and a surfactant recovery system connected to the emulsification system to receive the emulsion when produced from the first and second liquids. The second liquid is immiscible with the first liquid, and the surfactant recovery system recovers at least a portion of surfactant from the emulsion when the emulsion is received from the emulsification system.

Abstract: Apparatus, methods and systems for processing waste are provided. For example, a system for processing waste, wherein the waste comprises hard particulates embedded therein, can be provided. The system can comprise a waste disruptor, wherein the waste disruptor disrupts the waste and releases at least one of the embedded hard particulates from the disrupted waste; a segregator, wherein the segregator segregates at least one of the released hard particulates from the waste; and a dilution unit, wherein the dilution unit dilutes the waste. In some embodiments, the system can include a waste loader that provides waste continuously to the waste disruptor, which is configured to disrupt at least a portion of the continuously provided waste.

Abstract: Selenium in the form of a reduced species such as selenocyanate is oxidized to produce an oxidized selenium species such as selenate or selenite, and then a biological reduction process is used to remove selenium from the oxidized selenium species. In an example, a chemical oxidant is added to a wastewater containing selenocyanate to produce selenate and selenite. The partially treated wastewater is then fed to a reactor containing a fixed media supporting a biofilm with selenium reducing organisms. The selenium in the selenate and selenite is reduced to an insoluble form of selenium, such as elemental selenium, which precipitates from the wastewater.

Abstract: A device for separating platelets from a fluid suspension comprises a mixing chamber operable to receive and mix fluid suspensions and an aggregating agent to form platelet aggregates and residual fluid components. A filter can be configured to be in fluid communication with the mixing chamber and can be further configured to collect platelet aggregates and allow residual fluid components to pass therethrough. The mixing chamber and the filter are operable by a user without input from an external energy source.

Abstract: Technologies are generally described for a nanoparticle filter and system effective to move a nanoparticle from a fluid to a location. In some examples, the method includes providing the fluid including the nanoparticles. In some examples, the method further includes applying a first light to the fluid to create a first plasmon. In some examples, the first plasmon is effective to aggregate the nanoparticles to generate a nanoparticle aggregation. In some examples, the method includes applying a second light to the fluid to create a second plasmon. In some examples, the second plasmon is effective to move the nanoparticle aggregation to a location.

Abstract: A system for extracting liquid from a mass comprising a portable platform having an upper surface, a system mass input, a polymer feeding and blending system on the upper surface, a liquid extraction assembly on the upper surface, and piping having a first section between the system mass input and the polymer feeding and blending system, and a second section between the polymer feeding and blending system and the liquid extraction assembly. The system is configured to have mass inputted into the system mass input, transport the mass to the polymer feeding and blending system through the first section of the piping, inject polymer into the mass in the polymer feeding and blending system, and transport the mass from the polymer feeding and blending system to the liquid extraction assembly. Pressure from mass forced into the liquid extraction assembly forces liquid in the mass to exit the mass.

Abstract: A mixing unit may be disposed under water of a circular reservoir tank. The mixing unit squirts out water at an upward, outward and skewed angle so as to facilitate rotation of the water within the tank and vertical mixing of the water so as to destratify the temperature gradients within the water.

Abstract: An immersion-type membrane separation apparatus having a novel structure, which enables a practically applicable level of cleaning of a separation membrane by means of an ultrasonic wave generated by an ultrasonic transducer and can exhibit steady filtration performance for a long period. An ultrasonic transducer for cleaning and removing matters adhering to a separation membrane during the filtration of raw water is provided. The matters adhering to the separation membrane is cleaned and removed by means of an ultrasonic wave emitted from the ultrasonic transducer transducer. The separation membrane is made of polytetrafluoroethylene (PTFE).

Abstract: A microbial desalination cell includes an anode, a cathode, a saline solution chamber and a cathode rinsing assembly. The anode is at least partially positioned within an anode chamber for containing an aqueous reaction mixture including one or more organic compounds and one or more bacteria for oxidizing the organic compounds. The cathode is directly exposed to air. The saline solution chamber is positioned between the anode and the cathode, and is separated from the anode by an anion exchange material and from the cathode by a cation exchange material. The cathode rinsing assembly is for rinsing the cathode with a catholyte.

Abstract: A system and method for photochemical treatment of liquid substances with ultraviolet light inside liquid conveying tubings. The system includes an elongated polymeric light guiding liquid conveyance tube having first and second open ends and an internal surface defining the interior and liquid conveying conduit of the tube, and a UV light source, which is optically connected to the interior and liquid conveying conduit of the tube. The light guiding tube includes one or multiple concentric layers of polymeric materials selected from a group that includes thermoplastic and thermosetting polymers, elastomers and composites. The tube has at least one UV light transmitting polymeric material layer having a lower refractive index value than the refractive index value of the liquid substance conveyed within the tube.

Abstract: A vessel and method for removing immiscible fluid from contaminated water, the vessel comprising: at least one chamber; an injection line in fluid communication with an inlet of the one chamber; bubble generation means in fluid communication with the injection line for injecting gas bubbles into the injection line and allowing mixing in the injection line of the gas bubbles and the contaminated water to form an inlet fluid; an inlet weir within the chamber adjacent the inlet; an immiscible fluid weir within the chamber; a trough for collecting the immiscible fluid and allowing the immiscible fluid to flow out of the at least one chamber through an immiscible fluid outlet; and a cleaned water outlet generally at the bottom of the chamber; wherein when the inlet fluid is injected into the chamber, it passes through the inlet and over the inlet weir, the cleaned water flows downwardly toward the cleaned water outlet, and a remaining mixture of the immiscible fluid and the gas bubbles floats through the chamber t

Abstract: A water treatment method is provided for helping to partially or completely remove sodium and methane gas from water. In the method, water is combined with a reactant that is formulated to combine with the sodium in the water and form a compound. The water and compound are then passed through a bed of media for helping to separate the compound from the water. The method also includes aerating the water to release gases contained therein by breaking the water into microdroplets by passing it through a screen. Additionally, the method may include a step wherein the water is passed through an acidic resin for facilitating a cation exchange where additional sodium is removed. A water treatment apparatus for performing the method is also provided.

Abstract: A system and method for remediating a body of water and collecting suspended and dissolved solids therefrom are provided. The system includes a water-impervious lining positionable in a depression in or adjacent a body of water. The lining and depression define a treatment vessel, which includes a treatment portion, an outlet portion for containing treated water, and an outflow weir between the treatment portion and the outlet portion. Water to be treated is transported from the water body to the treatment portion. An entrapment element is delivered and mixed into the transported water, the entrapment element for capturing suspended and dissolved solids in the transported water and effecting a separation between the captured solids and water cleansed therefrom. The captured solids can be removed from the treatment basin, and the cleansed water can move through a channel in the outflow weir into the outlet portion.

Abstract: An exemplary liquid purifying apparatus includes beads in contact with the liquid, a lighting element, and a driving member. Each bead has a purifying coating comprised of a nano material formed thereon. The lighting element has the beads positioned thereon. The driving member is configured for driving the lighting element to rotate, thereby rotating the beads in the liquid.

Abstract: The invention aims at enabling, in a catalytic decarbonation apparatus, inert particles coated with calcium carbonate to be constantly and systematically extracted from the reactor, with no risk of clogging the discharge pipes. Therefor, said pipes (7?a, 7?b) have an inside diameter ranging between 40 and 60 mm and they have a downward incline up to their connection to an outside discharge conduit (8?), except, possibly, a horizontal portion starting from the orifice through which they emerge into the reactor (1?).

Abstract: Apparatus and method for hydrolyzing biological material for safe disposal thereof without the necessity of incineration or use of disinfectants are described. An alkaline solution having a concentration and an amount effective for hydrolyzing the biological material is brought into contact therewith by means of rotating paddles which both pound the biological material into small pieces and thoroughly mix the alkaline solution with the material under pressure and at elevated temperature. Following the hydrolysis of the biological material, a chosen portion of the water is removed from the alkaline solution and from the liquefied biological material, such that the resulting product solidifies when cooled. The present safe disposal of the biological material does not require incineration thereof, the addition of disinfectants thereto, or the discharge of liquid effluent containing processed biological material into the sewage system.

Abstract: A system and method of separating grease from water in used cooking oil prior to collection and removal of the grease from the restaurant or other facility where the used cooking oil was created, collected or stored.

Abstract: A water reaction tank for reacting water containing suspended solids with a flocculant includes a housing having an input, an output, and a water flow path between the input and the output. The flow path has a mixing section and a reaction section. Sealable flocculant ports are provided for inserting a flocculant into the mixing section of the housing. Each of the mixing section and the reaction section contains baffles. The mixing section baffles encourage turbulent flow to increase contact with the flocculant, and the reaction section baffles encourage turbulent flow and increase the length of the water flow path.

Abstract: A method and system for removing from an aqueous system which is contaminated therewith: (1) mercury present as colloids, ions and/or organically bound compounds, and (2) hydrocarbons solubilized, dispersed, and/or emulsified in the said system. Pursuant to the invention the aqueous system to be treated (such as “produced water”) is passed successively through three filtration stages. The first filtration stage is provided with absorption media which effects reduction/removal of dispersed organically bound mercury species and of the dispersed and partially dissolved hydrocarbon phases, as well as of some colloidal mercury and other dissolved metallic species. The second filtration stage utilizes a salt modified reticulated granular filtration media for reduction/removal of slightly dissolved hydrocarbon phases, mercury in colloidal and ionic form and other dissolved metals.

Abstract: An adjustable Venturi is disclosed, and having a plurality of inlet ports providing substances to be mixed with a flow of fluid through the Venturi. In one embodiment, the Venturi is constructed having an inlet portion, an outlet portion, with an annular mixing chamber coupled to inlet ports so that substances provided through inlet ports are mixed in the mixing chamber, and such mixture introduced into the flow. A gasket sealably disposed between inlet portion and outlet portion is selectable in thickness, for adjusting width of a Venturi interface between the inlet portion and outlet portion. In another embodiment, the inlet portion and outlet portion are fitted in an elongated opening, and are replaceable to change operational characteristics of the Venturi. A replaceable disk having a central opening and substance-providing passageways is disposed between the inlet portion and outlet portion, and may be changed to change characteristics of the Venturi.

Abstract: The invention relates to a device for treating urea-containing water. The invention also relates to a domestic toilet provided with such a device. The invention also relates to an animal accommodation provided with such a device. In addition, the invention comprises a method for treating urea-containing water. The device comprises a nitrification unit adapted to oxidize urea to nitrates and carbon dioxide, wherein the nitrification unit is also provided with an oxygen feed, a gas discharge and a throughfeed for feed of waste water nitrified by the nitrification unit to a filtration unit connected to the nitrification unit. The nitrification unit preferably comprises nitrifying bacteria.