| Apparatus and method for denitrification of treated water from aerobic wastewater treatment systems -> Monitor Keywords |
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Apparatus and method for denitrification of treated water from aerobic wastewater treatment systemsRelated Patent Categories: Liquid Purification Or Separation, Processes, Treatment By Living Organism, Anaerobically, With Subsequently Aerobically Treating LiquidApparatus and method for denitrification of treated water from aerobic wastewater treatment systems description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070215542, Apparatus and method for denitrification of treated water from aerobic wastewater treatment systems. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims the priority of U.S. Provisional Application No. 60/760,618 filed on Jan. 20, 2006, the disclosure of which is incorporated herein by reference for all purposes. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to aerobic wastewater treatment systems, particularly residential wastewater treatment systems and, more particularly, to the denitrification of treated wastewater from such aerobic wastewater treatment systems. [0004] 2. Description of Prior Art [0005] Typical residential aerobic wastewater treatment systems comprise a pre-treatment vessel or tank, an aerobic digestion vessel or tank and a pump vessel or tank. In operation, the raw wastewater, which can be a mixture of so-called black water and grey water from a residence flows to the pre-treatment tank where the bulk of the solids settle out. The largely solids free water from the pre-treatment tank flows into the aerobic digestion tank where under the influence of an oxygen containing gas, the bacteria aerobically digests the organic solids carried over from the pre-treatment tank. Most aerobic digestion tanks (aeration tank) are comprised of a so-called aeration chamber and a clarifier chamber, digestion of the suspended and dissolved organic solids being conducted in the aeration chamber, substantially clarified water being removed from the clarifier chamber which then flows by gravity into the pump tank, a holding tank or in some cases for direct disposal. [0006] Wastewater generally contains large amounts of nitrogen in the form of nitrates (NO.sub.3.sup.-), nitrites (NO.sub.2.sup.-), ammonia (NH.sub.4.sup.+) and nitrogen gas (N.sub.2). All these forms of nitrogen are biochemically interconvertible, the former three being nitrogen nutrients. Nitrogen nutrients from wastewater can lead to the nutrient enrichment of water bodies causing excessive growth of aquatic plants (algae). The dissolved oxygen in the water body becomes depleted when the aquatic plants die, fall to the bottom and then are decomposed by bacteria. The oxygen depletion can reduce the population of indigenous fish and other oxygen-consuming organisms. Nitrogen nutrients from wastewater have also been linked to ocean "red tides" that poison fish and cause illness in humans. Lastly, nitrogen nutrients in drinking water may contribute to miscarriages and is known to be the cause of a serious illness in infants called "Blue Baby Syndrome". Of the nitrogen nutrients, nitrates cause the greatest problem. [0007] Accordingly, it is important for aerobic wastewater treatment system to produce treated wastewater which, to the extent possible, is nitrogen nutrient poor and, in particular, contains the minimum possible amount of nitrates. [0008] It is known that there are denitrifying bacteria that can convert dissolved nitrate into harmless nitrogen gas. For denitrifying bacteria to work, several things are required: (1) a source of energy, e.g., organic material, (2) an anoxic environment (one with little to no dissolved oxygen present), (3) nitrates, and (4) efficient mixing and residence time. [0009] To deal with the problem of producing nitrogen nutrient and more particularly nitrate-free treated wastewater from aerobic wastewater treatment plants, it has been proposed to recycle a portion of the effluent from the pump tank to the pre-treatment tank. Although in the pretreatment tank there is sufficient energy available in the form of organic matter, and nitrogen nutrients are plentiful, it is difficult to ensure that the system is anoxic. Further, the mixing/residence time between the denitrifying bacteria and the recycled nitrates are in question. In any event, it has generally been accepted that this method results in reduced nitrogen nutrients, particularly nitrate content in the treated wastewater which is removed from the system. [0010] A typical residential aerobic wastewater treatment plant has a treatment capacity of 500 gallons a day. In the prior art system, recycle of too large of a volume of the treated wastewater from the pump tank to the pretreatment tank can overload the clarifier tank. However, conventionally prior art systems operate in this manner. In this regard, this recycle occurs whenever the pump in the pump tank is discharging the treated wastewater from the pump tank. [0011] Accordingly there is clearly a need for a more efficient and reliable method and/or apparatus for denitrifying treated wastewater from aerobic wastewater treatment systems. SUMMARY OF THE INVENTION [0012] According to one aspect of the present invention, treated wastewater from an aerobic wastewater treatment system (AWTS) is analyzed for a given set of conditions specific to the AWTS to determine total nitrogen nutrients, i.e., the sum of nitrates, nitrites and ammonia. Based on the amount of total nitrogen nutrients present in the effluent, a compressor, pump or the like which supplies air or other oxygen-containing gas to the aeration chamber of an aerobic wastewater treatment plant is cycled to alternatively provide an anoxic environment and an aerobic environment in the aerobic chamber for predetermined periods of time. This cycling is conveniently controlled by a timer/controller connected to the pump and can vary, both as to frequency and duration, depending upon a variety of empirically observed parameters of the particular AWTS. [0013] In another aspect of the present invention the pump compressor which is used to introduce the oxygen-containing gas into the aeration chamber is connected to a by-pass circuit having an inlet, an outlet, a first branch and a second branch. The inlet is connected to the pump. Disposed in the first branch is a solenoid valve while a flow restrictor, e.g., an orifice plate or the like, is disposed in the second branch. The outlet from the by-pass circuit is connected to a feedline which in turn is connected to a diffuser disposed in the aeration chamber. In this embodiment, the pump or compressor runs continuously meaning that when the solenoid valve is open in the first branch, air flow enters the feedline substantially unabated and is subsequently ejected into the treated wastewater and the aeration chamber through the diffuser. When the solenoid is in the closed position, flow through the first branch is stopped but, since the pump is running continuously, a reduced flow of oxygen-containing gas passes through the second branch containing the flow restrictor to ensure that at least some oxygen-containing gas is entering the aeration chamber through the diffuser thereby ensuring that there is sufficient turbulence in the aeration chamber to prevent the settling of any solids in the treated wastewater in the aeration chamber. In this embodiment as noted, the pump runs continuously ensuring that at all times there is mixing of solids in the aeration chamber. A timer/controller is connected to the solenoid valve and depending upon empirically derived conditions for the AWTS, opens and closes the solenoid valve to cycle the treated wastewater in the aeration chamber between alternate aerobic and anoxic/denitrification environments. [0014] In yet another embodiment of the present invention, there is a dissolved oxygen (DO) probe disposed in the aeration chamber and connected to a DO controller. The DO controller in turn is connected to the pump or compressor and is also connected to a timer. In an alternative embodiment, the DO controller can be connected to a system monitor which can set off an alarm, advise regulatory authorities of a variety of aspects of the particular AWTS, etc. In this embodiment, the timer/controller serves to determine macro denitrification and aerobic treatment periods. Thus, the timer/controller can be programmed, again based on empirical measurements as described above made on the particular AWTS system, so as to establish the relative lengths of the denitrification period and the aerobic digestion period. Thus, by way of example only, the timer/controller in communication with the DO controller can signal the pump to turn on for one hour during the aerobic treatment periods or cycle and turn off for two hours during the denitrification cycle. However, during those respective cycles, the DO controller via the DO probe is determining the DO in the aeration chamber. Depending upon which cycle the system is in, i.e., the denitrification cycle or the aerobic treatment cycle, the DO controller, based on the measurement of DO in the water in the aeration chamber, will periodically turn the pump on and off so as to, in the denitrification cycle, maintain the oxygen level between zero and 1 part ppm, i.e., greater than 0 and less than 1 ppm (anoxic condition) and, during the aerobic treatment cycle, maintain the DO level in the water in the aeration chamber above 1, preferably between 1 and 4 ppm. Thus, the DO controller in conjunction with the DO probe acts as a micro or fine tuner of the system in both the denitrification and aerobic treatment cycles. [0015] In still another embodiment of the present invention, a variation of two of the above described embodiments is employed. In this embodiment, there is a by-pass circuit as described above as well as a DO probe, a DO controller, and a timer. In this embodiment, the DO controller is connected to the solenoid valve rather than the pump, the pump running continuously. Accordingly, if, for example, during a denitrification cycle the DO controller in combination with the DO probe detects excess oxygen rendering the system aerobic and therefore unsuitable for denitrification, the DO controller will close the solenoid valve until the oxygen level in the denitrification cycle returns to the desired level, i.e., between just greater than zero and just less than 1 ppm. Conversely, in the aerobic treatment cycle, should the DO controller detect anoxic conditions in the aeration chamber, the solenoid valve would be open to allow full flow of oxygen-containing gas into the aeration chamber. Additionally, as discussed above, the DO controller can be used in this embodiment to ensure that the amount of DO does not exceed a desired level, e.g., about 3 ppm. In this embodiment, since the pump is running continuously, circulation of solids in the aerobic chamber continues, minimizing settling of the solids. BRIEF DESCRIPTION OF THE DRAWINGS [0016] FIG. 1 shows a typical aeration vessel used in a typical AWTS in conjunction with a pump and timer, shown schematically. [0017] FIG. 2 shows another embodiment of the present invention, and in addition to the aeration vessel of an AWTS, shows a by-pass circuit connected between the pump and the air diffuser as well as a timer/controller connected to a solenoid valve forming part of the by-pass circuit. [0018] FIG. 3 shows an aeration vessel together with a DO probe, a DO controller, a timer/controller and a system monitor. [0019] FIG. 4 shows another embodiment of the present invention including an aeration vessel, a by-pass circuit such as shown in FIG. 2, but in addition shows a DO probe, a DO controller, a timer/controller and a system monitor as shown in FIG. 3. DESCRIPTION OF THE PREFERRED EMBODIMENTS Continue reading about Apparatus and method for denitrification of treated water from aerobic wastewater treatment systems... Full patent description for Apparatus and method for denitrification of treated water from aerobic wastewater treatment systems Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Apparatus and method for denitrification of treated water from aerobic wastewater treatment systems patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. 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