Simultaneous anoxic biological phosphorus and nitrogen removal with energy recovery

SIMULTANEOUS REMOVAL OF NITROGEN AND BIOLOGICAL PHOSPHORUS

ANOXIC WITH ENERGY RECOVERY

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority for US Application No. 12 / 981,984, filed on December 30, 2010, entitled SIMULTANEOUS REMOVAL OF NITROGEN AND ANOLOGICAL BIOLOGICAL PHOSPHORUS WITH ENERGY RECOVERY, which is a continuation request in part and io claims priority for U.S. Application No. 12 / 886,321 filed on September 20, 2010, entitled SIMULTANEOUS REMOVAL OF NITROGEN AND ANOXIC BIOLOGICAL PHOSPHORUS, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Removing various components of wastewater, such as nitrogen, carbon, and phosphorus can be a difficult and expensive process that in some cases may require the addition of a carbon source to the wastewater treatment process. Additionally, a high concentration of dissolved oxygen used in many wastewater treatment processes contributes substantially to the cost of using the energy of a wastewater treatment plant. A carbon source, such as methanol, can be added to the process in an anoxic tank, for example, to help with denitrification. Additionally, an aerated tank may require high concentrations of dissolved oxygen to promote oxidation of oxygen demand (BOD) and ammonia. However, the addition of a carbon source and the need for high concentrations of dissolved oxygen are costly and contribute significantly to increasing them to treat wastewater.

SUMMARY OF THE INVENTION

The embodiments of the invention are defined by the claims below, not this summary. For that reason, a high-level description of various aspects of the invention is provided here, to provide an overview of the description, and to present a selection of concepts that are further described in the detailed description section below. This summary is not intended to identify key characteristics or essential characteristics of the claimed subject matter, nor is it intended to be used solely as an aid to determine the scope of the claimed subject matter.

In a first aspect, a process is provided to treat wastewater with simultaneous removal of organic matter, nitrogen, and phosphorus with energy recovery. The process includes providing a stream containing ammonia in a pretreatment tank that produces at least excess sludge, biogas, and a pretreated stream. The pretreated stream has at least 45% less carbon than the stream containing ammonia. Additionally, the biogas comprises at least methane and carbon dioxide. The process additionally includes flowing the pretreated stream and returning the active sludge to a anoxic tank that operates under anoxic conditions and mixing the pretreated stream and the return of the active sludge into the anoxic tank to form a mixed liquor, thus initiating phosphorus release and fermentation of particulate organic matter and organic matter%

dissolved. Additionally, the process includes transferring the mixed liquor to an aerated tank that operates under microaerophilic conditions. A concentration of dissolved oxygen in the aerated tank is less than 1.0 mg / l of the mixed liquor, which is effective in promoting simultaneous nitrification, denitrification, phosphorus release, and phosphorus uptake. Also, the process includes transferring the mixed liquor to a membrane tank that separates the treated effluent from the active sludge containing microorganisms. A first portion of the active sludge returns to the anoxic tank as the active return sludge. In a second aspect, a method is provided to reduce ammonia in a flow while recovering energy. The method includes providing a stream containing ammonia in a pre-treatment tank comprising anaerobic microorganisms that react with the stream containing ammonia to produce biogas and a pretreated stream. Additionally, the method includes contacting the pretreated stream with a stream containing oxygen under effective treatment conditions to form a first stream of product, the ammonia index in the stream pretreated with oxygen in the stream containing oxygen is about 2.28 g of O₂/ g of N-NH₃ (2.28 grams of oxygen per gram of nitrogen in ammonia) or less. The method further includes exposing the first product stream to organic matter under effective treatment conditions at a ratio of approximately 0.57 g of COD / g of N-NH₃ (0.57 grams of chemical oxygen demand (COD) per gram of nitrogen in ammonia) or less.

In a third aspect, a system is provided to treat wastewater with simultaneous removal of organic matter, nitrogen, and phosphorus with energy recovery. The system includes a pretreatment tank that receives sewage from plant Influents and that includes^cAnaerobic microorganisms that react with sewage from plant tributaries to produce, at least, blogs comprising methane, excess sludge, and a pretreated stream, the pretreated stream has at least 45% less carbon than sewage from plant influences. The system also includes an anoxic tank that receives the pretreated comment and the active return mud. The anoxic tank operates under anoxic conditions to promote denitrification, phosphorus release and fermentation of particulate organic matter and dissolved organic matter. Additionally, the system includes an aerated tank that receives a mixed liquor from the anoxic tank. io A concentration of dissolved oxygen in the aerated tank is less than 1.0 mg / l of the mixed liquor to effectively promote the development of phosphorus release bacteria that are present in the active return sludge received inside the anoxic tank. Phosphorus release bacteria in active return sludge allow the release of phosphorus and the fermentation of particulate organic matter in the anoxic tank. The system additionally includes a membrane tank that separates the wastewater from plant effluents from the active sludge, from which a part of the anoxic tank is recycled as the active return sludge.

BRIEF DESCRIPTION OF THE DRAWINGS

Further illustrative embodiments of the present invention are described in detail with reference to the attached figures, and wherein:

FIGURE 1 illustrates a schematic view of a wastewater treatment process, in accordance with an embodiment of the present invention;

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FIGURE 2 illustrates a schematic view of an alternate wastewater treatment process, in accordance with an embodiment of the present invention;

FIGURE 3 illustrates a reduction in energy use in a wastewater treatment plant as a result of the implementation of the embodiments of the present invention;

FIGURE 4 illustrates a reduction of ammonia and phosphate when the embodiments of the present invention are implemented in a wastewater treatment plant;

FIGURE 5 illustrates a bar graph showing the concentrations of phosphorus, dissolved oxygen, and nitrates in each tank;

FIGURE 6 illustrates a schematic view of a wastewater treatment process with energy recovery, in accordance with an embodiment of the present invention;

FIGURE 7 illustrates a schematic view of a wastewater treatment process using an upflow anaerobic sludge mantle reactor (UASB), in accordance with an embodiment of the present invention;

FIGURE 8 illustrates a schematic view of a wastewater treatment process using chemically enhanced primary treatment (CEPT), in accordance with an embodiment of the present invention;

FIGURE 9 illustrates a schematic view of a wastewater treatment process using a one-stage active sludge system, in accordance with an embodiment of the present invention;

FIGURE 10 illustrates a schematic view of a wastewater treatment process using a one-stage active sludge system, in accordance with an embodiment of the present invention;

FIGURE II illustrates a bar graph showing a comparison of energy intensity using various water treatment systems, in accordance with an embodiment of the present invention; and

FIGURE 12 illustrates a bar graph showing a comparison of energy generation from biogas, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The subject matter of the embodiments of the present invention is described herein specifically to meet the legal requirements. But the description itself is not intended to necessarily limit the scope of the claims. On the contrary, the subject matter claimed can be incorporated in other forms to include different stages or combinations of similar stages with those described herein, in conjunction with other present and future technologies. The terms should not be construed to imply any particular order between or by various stages described herein unless and except when the order of the individual stages is explicitly described.

<img file="CO6541589A2_D0001.tif" />

FIGURE 1 illustrates a schematic view of a wastewater treatment process 10. More specifically, the wastewater treatment process provides a cost and energy efficient method for the simultaneous removal of nitrogen, phosphorus, and organic matter from waters residuals of plant influents. Although many systems require a source of external carbon and high levels of dissolved oxygen, the embodiments of the present invention do not require it, and in fact require very low amounts of dissolved oxygen and carbon compared to amounts normally used in the treatment systems of sewage water. For example, many systems require an external source of carbon for phosphorus removal and nitrogen removal, but in the embodiments of the present invention, nitrogen removal only requires minimal amounts of carbon, since this mainly uses ammonia. Additionally, phosphorus removal uses particulate and dissolved carbon (for example, particulate organic matter) that is present in wastewater, rather than just dissolved carbon or an external carbon source. In the embodiment of FIGURE 1, three separate tanks are used to simultaneously remove nitrogen, phosphorus, and organic matter from the sewage of plant influences 12. As used herein, the sewage from plant influences 12 is a raw wastewater that has not yet been treated and therefore has not yet entered a wastewater treatment system, such as wastewater treatment systems. described here

A first tank shown in FIGURE 1 is an anoxic tank 16 that receives at least two streams, which includes sewage from plant influences 12 and active return sludge 14. As will be discussed further here, the ι5 active return sludge 14 it is a part of the active sludge that is recycled from the third tank, to the membrane tank 20, in one or more of the other tanks, such as the anoxic tank 16. As used herein, the active sludge is a comment that has been separated from the plant effluent. This active sludge stream contains a microbial mass, in addition to nitrates and dissolved oxygen. The microbial mass includes a variety of biological components, including bacteria, fungi, protozoa, rotifers, etc. Although both heterotrophic and autotrophic microorganisms can reside the active sludge, heterotrophic microorganisms normally predominate. Heterotrophic microorganisms obtain energy from organic carbonaceous matter in sewage from plant influences for the synthesis of new cells. These microorganisms then release energy through the conversion of organic matter into compounds, such as carbon dioxide and water. Autotrophic microorganisms in the active sludge generally reduce oxidized carbon compounds, such as carbon dioxide, for cell growth. These microorganisms obtain their energy by oxidizing ammonia with nitrate, known as nitrification, which is described here further.

As mentioned above, the active return sludge 14 is a part of the active sludge that is produced by the separation step (for example, membrane tank or membrane bioreactor) at the end of the treatment process. The active return sludge 14 is recycled in the anoxic tank 16 and provides the tank with microbial mass, residual oxygen, nitrates, and nitrites. It should be noted that phosphorus release does not normally occur in anoxic tanks with the active return sludge that has nitrates and dissolved oxygen, but in the embodiments of the present invention, phosphorus release occurs in the anoxic tank 16. Phosphorus release occurs because the bacteria that are

Μ used to consume phosphorus are also present in the active return sludge 14. Additionally, phosphorus release occurs due to hydrolysis and fermentation conditions of particulate organic matter present in the influent wastewater. As used herein, hydrolysis is the decomposition of polymeric organic matter into monomers by microbial action. In one embodiment, hydrolysis refers to a chemical reaction during which the molecules are divided into hydrogen cations and hydroxide anions in the process of a chemical mechanism. This type of reaction is used to break down certain polymers. As such, instead of only using dissolved organic matter as the carbon source for phosphorus removal, the embodiments of the present invention allow particulate and dissolved organic matter to be used as a carbon source for the removal of match. Normally particulate organic matter cannot be used, but because it is fermented here, it can be used as a carbon source, thus eliminating the need for an external carbon source.

In wastewater, organic matter is presented as particulate organic matter and dissolved organic matter. Three main tests are used to determine organic matter in wastewater. These include biological oxygen demand (BOD), total organic carbon (TOC), and chemical oxygen demand (COD). Unlike dissolved organic matter, particulate organic matter takes the form of suspended solids found in wastewater. As discussed further here, the particulate organic matter undergoes the hydrolysis process to convert the particles into soluble solids, thus allowing higher phosphorus removal rates when the embodiments of the present invention are used.

Phosphorus release and phosphorus uptake refer to the process of phosphorus-accumulating organisms (ODPs) that store polyphosphates as an energy reserve in intracellular granules. Under anaerobic conditions, the

PAO release orthophosphates, using energy to accumulate simple organic materials and store them as polyhydroxyalkanoates (PHA). In aerobic conditions, or at least conditions where there is some oxygen, nitrites, or nitrates present, ODPs grow in stored organic material, using some of the energy to take orthophosphate and store it as polyphosphate. As such, when the ODP stores carbon for future growth, the ODP also releases phosphorus, sometimes simultaneously. When the PAO uses stored carbon, they capture phosphorus using preferably nitrite as an electron acceptor. As will be described further here, an aerated tank has low levels of dissolved oxygen, but the PAO still captures phosphorus. When oxygen, nitrite or nitrate are present, the PAO can still obtain carbon energy. Therefore, when carbon is abundant, the PAO stores it in its cells and waits for conditions where an electron acceptor is present so that they can use carbon for phosphorus growth and uptake. The phosphate is then removed in the residual active sludge 26, which is generally the active sludge that is not recycled 30 to the anoxic tank 16. The development of the ODP population will be discussed here further. The anoxic tank 16 operates under anoxic conditions such that there is little or no dissolved oxygen, but nitrates may be present (for example, NO₂ and not₃). A continuous oxygen deficit is maintained in the anoxic tank.

The anoxic tank 16, in one embodiment, has a mixer that mixes sewage from plant influences 12 and active return sludge 14 to form a mixed liquor. The mixed liquor, as used herein, simply refers to a mixture of sewage from plant influences 12 and active return sludge 14. The mixing index can be adjusted, in addition to adjusting the flow rate of the active return sludge 14, to control the release of phosphorus in the anoxic tank 16. It should be noted that the addition of external carbon source, such as methanol, is avoids in the embodiments of the present invention such that there is no additional source of carbon necessary to carry out the embodiments of the present invention. In addition to phosphorus release, denitrification also occurs in the anoxic tank 16. Denitrification is the purification of nitrites or nitrates to give nitrogen gas, and occurs when microbes consume oxygen from nitrites or nitrates. More specifically, denitrification is a microbially facilitated process of deasimilatory reduction of nitrate that ultimately produces molecular nitrogen (N₂), which returns to the atmosphere. Nitrates and nitrites are converted into nitrogen gas through a denitrification process. Denitrification generally reduces the oxidized forms of nitrogen in response to the oxidation of an electron donor, such as organic matter which, here, is present in the active return sludge 14. This process is mainly performed by heterotrophic microorganisms in an environment where oxygen is depleted, or where oxygen consumption exceeds the oxygen supply rate, such as anoxic tank 16 and aerated tank 18. Using the embodiments of In the present invention, the denitrification process is also carried out by autotrophic nitrifiers under conditions of low oxygen dissolved in the anoxic tank 16 and the aerated tank 18. The following reactions illustrate denitrification, which includes an illustrative redox reaction:

(1) NO₃'-&gt; Noy NO + N₂O - + N₂(g) ιΤ (2) 2 N0₃ + 10e '+ 12Η' - * Ν₂ + 6Η₂Ο

Particulate organic matter and dissolved organic matter from sewage from plant influences 12 are fermented in the anoxic tank. The

5. Conditions in the anoxic tank in the embodiments of the present invention induce high rates of hydrolysis and fermentation of particulate organic matter, which provides excess fermented organic matter which is needed for the denitrification reaction, allowing simultaneous release of phosphorus and PHA formation. The fermentation of io particulate organic matter allows additional carbon to be used for phosphorus removal. The average stoppage time of the influent wastewater flow in the anoxic tank can vary from 1 hour to 10 hours. In one embodiment, the concentration of dissolved oxygen in the anoxic tank is less than 0.3 mg / L. In further embodiments, the concentration of dissolved oxygen in the anoxic tank is less than 0.2 mg / L. In an even further embodiment, the concentration of dissolved oxygen in the anoxic tank is 0.1 mg / L or less. Additionally, the recirculation rates of the active return sludge can vary between 0.3 and 6 times the influent flow rate.

In anoxic mixed liquor it is transferred to an aerated tank 18. Although a single aerated tank 18 is illustrated in FIGURE 1, multiple aerated tanks can be used, and can be configured in parallel or in series. Alternatively, an aerated tank may be used, but the aerated tank may have more than one compartment through which the mixed liquor flows. The purpose of having more than one compartment is to improve the kinetic conditions of the general process that minimizes the volume of the tank. Opclonally, a portion of the active sludge is transferred to the aerated tank to provide an additional microbial population ft necessary to ferment dissolved and particulate organic matter and to promote phosphorus release. This is advantageous in those cases where nitrate concentrations in the membrane tank are excessively high. Unlike many aerated tanks, the aerated tank

18 provided by the embodiments of the present invention are operated under very low dissolved oxygen concentrations, such as microaerophilic conditions, which promote the development of the microbial population (e.g., phosphate accumulating organisms (PAO)) used for the release and uptake of match. In general, this bacterial population is capable of storing phosphorus, such as in the form of polyphosphates, and metabolizes them for energy production and cellular synthesis, which results in the removal of phosphorus from the system through the active sludge. This particular microbial population is unable to develop where there are high concentrations of dissolved oxygen. Because this particular bacterial population is capable of developing in the aerated tank 18, they are also present in active return sludge 14 that is recycled to the anoxic tank 16, thus allowing the release of phosphorus in the anoxic tank 16. The Phosphorus uptake can occur simultaneously with the release of phosphorus in the aerated tank 18.

In addition to phosphorus release and phosphorus uptake, nitrification and denitrification also occurs in the aerated tank 18. In one embodiment, nitrification, denitrification, and phosphorus release occurs simultaneously to the aerated tank 18. As previously described, Denitrification is a microbially facilitated process of deasimilatory reduction of nitrate that ultimately produces nitrogen gas by reducing oxidized forms of nitrogen. On the one hand, nitrification is the decomposition of ammonia in nitrate and water. More particularly, nitrification is the biological oxidation of ή

ammonia with oxygen in nitrite followed by the oxidation of nitrites in nitrates. Generally two groups of organisms are responsible for the oxidation of ammonia and nitrite. These two groups are bacteria that oxidize ammonia (AOB) and archaebacteria that oxidize ammonia (AOA). A second group is the bacteria that oxidize nitrites, NOB, is responsible for the oxidation of nitrites to nitrates. The following equations represent the nitrification processes:

<td></td><td> (3)</td><td>NH₃+ CO₂ + 1.5 O₂ + AOA / AOB NO₂-</td>

<td></td><td> (4)</td><td>NO₂- + CO₂ + 0.5 O₂ + NOB -&gt; NO₃’</td>

<td> 10</td><td> (5)</td><td>NH₃ + O₂'+ NO₂- + 3H⁺+ 2e</td>

<td></td><td> (6)</td><td>NO₂· + H₂O '+ NO₃- + 2H⁺ + 2e.</td>

However, in the embodiments of the present invention, the reactions represented by equations (4) and (9) occur to a minimum, thereby reducing the need for oxygen and obtaining significant savings in energy use. In some embodiments, very little nitrate or no nitrate is found in the mixed liquor because reactions (4) and (6) have a small percentage of the general process as in equation (I) above, mainly nitrites in contrast of the nitrates are those that are converted into nitrogen gas. As in equation (2), less than ten electrons are needed to convert nitrite to nitrate gas. In embodiments of the present invention, these electrons, unlike coming from methanol or another external carbon source, come from ammonia. In the embodiments of the present invention, PAO bacteria can also use nitrites as electron acceptors for denitrification. This will be discussed in more detail below. As shown by reactions (3) and (5) above, ammonia is used to convert nitrites to nitrogen gas. Carbon is required as an external source, some of the ammonia used for reactions (3) and (5), but some of the ammonia is also used as a source of electron reduction for denitrification. This is how nitrification and denitrification can occur in systems with low oxygen concentrations and without an external carbon source.

Additionally, microaerophilic conditions allow the fermentation of dissolved and particulate organic matter in the aerated tank 18, which normally would not occur with higher concentrations of dissolved oxygen.

As mentioned above, nitrification and denitrification occurs in aerated and anoxic tanks, in accordance with the embodiments of the present invention. Conventional nitrification-denitrification is represented by reactions (7), (8), and (9) below. Reaction (9) is the net of reactions (7) and (8). Many times, this sequence of reactions requires a high concentration of dissolved oxygen and an external source of carbon. Here, approximately 4.57 grams of O are required for the reaction₂ per gram of NNH₃ (7) and approximately 2.86 grams of COD-O are required for the reaction₂per gram of N-NO₃ (8). The equations are as follows:

(7) 1NH₃ + 2O₂ -&gt; 1HNO₃ + H₂O (8) ¡HN0¡ + Organic Matter N₂+ H¡0

Reactions (9) and (10) below illustrate a process called a nitrification shortcut 25 where the initial reaction, or reaction (10) is directed only to nitrites, resulting in the need for oxygen and organic matter demand. Approximately 3.43 grams of O are required₂ per gram of N-NH₃ for τ \ reaction (9) and approximately 1.71 grams of COD-O are required₂ per gram of N-NH₃ for the reaction (10). In one case, when the first group of previous reactions (reactions (7) - (8)) is compared with the second group of reactions ahead (reactions 9) - (10)), the oxygen demand is reduced by approximately 25% (4.57 g of O₂ / g of N-NH₃ -3.43 g of O₂/ g of N-NH₃ = 1.15 g of O₂ / g of N-NH₃) and the need for organic matter is reduced by approximately 40% (2.86 g of O₂/ g of N-NO₃ -1.71 g of O₂ / g of N-NH₃ = 1.15 g of COD / g of N-NH₃). This set of reactions occurs in the anoxic tank and the aerated tank with PAO bacteria, which preferably catalyze the reaction (10) forward.

\ NH_}+-0₂ -&gt; UiNO₂+} H₂O (9) ²

IHNO₂ + Organic Matter -&gt; - N, + H, 0 (10) 2

The group of reactions labeled below (11) and (12) occur in the anoxic tank and the aerated tank. In some cases, this group of reactions is called the nitrification-denitrification process. As shown in equation (11), ammonia and oxygen are converted into nitrogen gas, nitrous acid and water. The organic matter is then used to convert nitrous acid into nitrogen gas, water, and carbon dioxide. Approximately 2.28 grams of O are required₂ per gram of N-NH₃ for the reaction (11) and approximately 0.57 grams of COD per gram of N-NH is required₃ for the reaction (12). When the three groups of reactions are compared, that third group of reactions (reactions (13) - (15)) require at least amounts of oxygen. The saving in organic matter is approximately 80% (2.86 g of O₂ / g of N-NO3 - 0.57 g of COD / g of N-NH₃ = 2.29 g of O₂ / g N) when

Λ compares with the amount of organic matter required for the third group of reactions below the first group of reactions (reaction (7) - (8)). Additionally, the required oxygen savings between the first and third group of equations is approximately 50% (4.57 g of O₂ / g of N-NH₃ 5 2.28 g of O₂ / g N-NH₃ = 2.28 g of O₂ / g N).

(11) - fíNO, + Organic Matter —i —IV, + H, 0 + CO, (12) ³ 6

With reference to FIGURE 1, the mixed liquor is then transferred from the aerated tank 18 to the third tank, shown here as a membrane tank 20, for a solid-liquid separation stage where the microorganisms are separated from the treated water. In active sludge processes, such as those described here, dissolved organic pollutants are transformed into water, carbon dioxide, and biomass, resulting in excess sludge production. The membrane tank 20 separates this sludge from the treated plant effluent 22. In one embodiment, the membrane tank is a membrane bioreactor that is a combination of a membrane process (e.g., microfiltration, ultrafiltration, hollow fiber, flat sheet , tubular) with a suspended growth bioreactor. A bioreactor refers to a device that supports a biologically active environment. Because a bioreactor must be associated with a separation unit to recover the biomass and purified liquid, and from the deficiencies and inconvenience of separate units, membrane bioreactors are used to provide the same result or better results, but in One unit As such, a membrane bioreactor is an association of a biological reactor and a cross flow filtration. In one case, the membrane tank 20 is aerated to provide water turbulence to scrub the submerged membrane filter. In one embodiment, the membrane filter uses microfiltration, but in another embodiment, ultrafiltration is used.

The result of the membrane filtration that occurs in the membrane tank 20 has at least two outflows, including treated plant effluent 22 and the active sludge 24, of which a part is recycled to the anoxic tank 16, and in some embodiments, to the aerated tank 18. As used herein, as the treated plant effluent 22 has the current leaving the third tank that has been treated for the removal of carbon, nitrogen, phosphorus, and other unwanted constituents, the excess of the active sludge is shown as the active sludge 26. The amount of active sludge 24 that is recycled to the anoxic tank 16 varies, but in some cases it varies anywhere from 50% to 600% of the amount of wastewater from plant influences 12 entering the anoxic tank 16. As such, for each gallon of sewage from plant influences 12, 0.5 to 6 gallons of active return sludge 14 can be added to the anoxic tank 16. In an alternative embodiment, the third tank in the embodiment of FIGURE 1, although Illustrates how a membrane tank 20 is a clarifier. The clarified ones are tanks used to separate, thicken and recycle the active sludge. Typically, clarifiers have a larger footprint than membrane bioreactors.

Referring now to FIGURE 2, a schematic view of an alternate wastewater treatment process is illustrated. An anoxic tank 16a, an aerated tank 18a, and a membrane tank 20a are illustrated in the embodiment of FIGURE 2 and operate in a manner similar to those described in FIGURE 1. Here, an anaerobic tank 28 is added downstream of , or after the anoxic tank 16a and upstream, or before the aerated tank 18a. In general, anaerobic tank 28 operates under anaerobic conditions, or under the absence of oxygen. Anaerobic tank 28 is a non-aerated tank, such that oxygen is not added and there are no nitrates. The contents are mixed in the aerobic tank 28 such that a mixer is present. The embodiment of FIGURE 2, or specifically when an anaerobic tank 28 is added to the system, conditions are used where the characteristics of the organic matter present in the Influent wastewater stream are such that additional retention time is needed for hydrolysis and fermentation of particulate organic matter. In one embodiment, the release of additional phosphorus in the anaerobic tank 28 takes place. In a manner similar to that described in FIGURE 1, the wastewater from Plant Influents 12a is mixed with the active return sludge 14a in an anoxic tank 16a. The mixed liquor is first transferred to an anaerobic tank 28, then to an aerated tank 18a, and finally to a membrane tank 20a. Leaving the membrane tank 20a is the treated plant effluent 22a and the active sludge 24a. A part of the active sludge 24a is recycled to the anoxic tank 16a as the active return sludge 14a, and optionally, a part is also recycled to the aerated tank 18a.

The residual active sludge 26a, in one embodiment, is discarded.

FIGURE 3 illustrates a graph 300 showing a reduction in energy use in a wastewater treatment plant as a result of the implementation of the embodiments of the present invention. As mentioned, when concentrations of dissolved oxygen are kept at a minimum in the aerated tank, energy use costs are significantly reduced, since the costs of adding dissolved oxygen can amount to up to 50% of total energy costs for a sewage treatment plant.

·7&gt;

As indicated by the "initiated trial", the technology described here was tested and it was found that energy costs are significantly reduced at least partially due to the low amounts of dissolved oxygen required in the aerated tank. As shown, before the test, the highest energy use is approximately 64,000 kWh / month, while the highest after the test is approximately 54,000 kWh / month, although the levels reach much lower amounts for the previous months.

Turning now to FIGURE 4, a bar graph 400 is illustrated that shows a reduction in ammonia and phosphate when the embodiments of the present invention are implemented in a wastewater treatment plant. As shown here, concentrations of influent ammonia are about 72 mg / l, but fall to about 1 mg / l after sewage from plant influents is treated using the treatment methods described here. Additionally, Phosphate Influent concentrations fall from about 64 mg / l to about 4 mg / l after sewage from plant influents is treated using the treatment methods described here.

Example

The following example illustrates a plant that has two parallel trains, which includes a first train (train A) and a second train (train B). The tanks in each of the trains are identical and are in the same location. However, the location in the tanks is different. Train A represents a typical process that would occur without the use of the embodiments of the present invention, while Train B represents a process that uses the embodiments of the present invention, such as a low concentration of dissolved oxygen in the aerated tank, as previously discussed. For example, as shown in Table 1 below, the concentration of dissolved oxygen in the aerated tank of train A is 1.3 mg / l, while the concentration of dissolved oxygen in the aerated tank of train B is 0.1 mg / l . As shown by the levels of phosphorus and nitrate / nitrite removal, in train B compared to those in train A, lower levels of dissolved oxygen in the aerated tank allow the development of bacteria that remove phosphorus in the aerated tank . These phosphorus-removing bacteria are then present in the active return sludge (not shown) from the membrane tank back to the anoxic tank. Phosphorus release is observed in the anoxic tank of train B, although not in the anoxic tank of train A. The net phosphorus collection takes place in the aerated tank of train B and not in the aerated tank of train A. Therefore , the highest levels of phosphorus uptake and removal occur in the process. As a result, the phosphorus levels in the membrane tank or the plant effluent are 3.65 mg / l for train B, which is much lower than the levels in the membrane tank for train A, which is 7.41 mg / l Similarly, nitrification - simultaneous denitrification takes place in the aerated tank of train B while nitrification only occurs in the aerated tank of train A, as reflected by the significantly greater difference in nitrate concentration. The nitrate / nitrite levels in the membrane tank for train B are 7.15-30 mg / l, which is lower than the levels of 8.31 mg / l in the membrane tank of train A.

Continuing with the example described above and illustrated in Table 1 below, FIGURE 5 illustrates a bar graph 500 showing the concentrations of phosphorus, dissolved oxygen, and nitrates in each tank. Compared to phosphorus levels, for example, you can see that the levels

Ίλ are much lower in the membrane tank for train B than for train A, which is partly due to the low concentrations of dissolved oxygen in the aerated tank.

Table 1. Concentrations of dissolved oxygen, phosphorus, and nitrates in a typical process (Train A) and processes using the embodiments of the present invention (Train B).

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Returning to FIGURE 6 on time, a schematic view 600 of a wastewater treatment process with energy recovery is illustrated, in accordance with an embodiment of the present invention. The embodiments of the present invention described herein are referred to in FIGURE 6 as a process.

Anox-P 620. The Anox-P 620 process, in the embodiments, relates to systems such as that described in FIGURE 1 that includes an anoxic tank, at least one aerated tank, and a membrane tank. However, in the embodiment of FIGURE 6 prior to the Anox-P 620 process, a 612 carbon removal pretreatment process is added to the general process. The functionality of the 612 carbon removal pretreatment process is to remove a substantial amount of carbon from the sewage of plant influents

610 In general, soluble organic matter and particulate organic matter become an insoluble gas, referred to herein as a 614 biogas. Because the Anox-P 620 process as described herein requires less carbon than other systems, the amount of Carbon present in sewage from plant influences 610 may be greater than what is currently needed. Other wastewater systems require much more carbon (for example, to remove nitrogen) in such a way that using a 612 carbon removal pretreatment process would not yet be considered due to the carbon in the sewage of plant 610 influents, in addition to the carbon in excess of that in the sewage of 610 plant influents, which would require treatment of sewage. By removing so much carbon from the influent stream in the pretreatment process, less oxygen is used in the aerated tank to remove the carbon. As such, the main advantages of the system as shown in FIGURE 6 is that methane is produced, and that less air or oxygen is required in the Anox-P 620 process. Additionally, the size of the tanks required for the Anox-P 620 process can be reduced when compared to the Anox-P process when carbon is not removed by a pretreatment process. The 612 carbon removal pretreatment process can utilize various technologies that are capable of removing a substantial amount of carbon from an influent stream. A few of these technologies are listed and described here for the purpose of example only, and it does not mean that they limit the embodiments of the present invention. For example, some of the carbon removal technologies may include an anaerobic process, such as an upflow anaerobic mud blanket reactor (UASB), a chemically enhanced primary treatment (CEPT), and an active sludge system of a stage (sometimes referred to as A in the NB process). Again, these technologies are listed for example purposes only, since there are other available technologies not mentioned here because of

Shortly. More details are discussed in each of these example technologies with respect to the subsequent figures.

In embodiments, the carbon that is removed from the sewage from plant influences 610 takes the form of methane (CH₄) and / or carbon dioxide (CO₂). In one embodiment, a 614 biogas comprising methane and carbon dioxide is formed. Biogas 614, once formed, is directed to other processes that are not described here, but collectively referred to as the use of biogas 616. This biogas 614, for example, can be used energy in fuel cells, microturbines, generators, etc. to generate electrical energy to compensate part or all of the electrical energy used in the water treatment plant. Here, carbon dioxide can be removed before being used in these systems. Alternatively, biogas 614 can be treated (for example, removed from carbon dioxide) and improved, such as by removing most of the carbon dioxide to produce natural gas, which can be used in a compressed form to produce compressed natural gas. , CNG, or alternatively it can be liquefied to produce liquefied natural gas, LNG. In one case, approximately 60% of the carbon present in the sewage from plant 610 influents is removed via the processes and reactions that occur in the 612 carbon removal pretreatment process such that approximately 40% of the carbon is it remains in the pretreated stream 618. In another case, approximately 70% of the carbon present in the sewage from plant influences 610 is removed via the processes and they react that occur in the 612 carbon removal pretreatment process so that approximately 30% of the carbon remains in the pretreated stream

618 In still other cases, less than 60% of the carbon, such as 45% of the carbon, is removed from the Influent stream via the pretreatment process of

3rd carbon removal 612. Biogas 614 itself, in one embodiment, is comprised of up to 80% methane. The other portion of biogas 614 may be a mixture of carbon dioxide, nitrogen, and hydrogen sulfide in different proportions. The proportion of methane with another portion may vary significantly depending on the operating conditions of the wastewater treatment plant, and thus the examples provided herein are for example purposes only and do not mean that they limit the embodiments of the present invention. For example, the percentage of methane in one embodiment may be 50%, but in an alternate embodiment it may be 80%. As mentioned, compared to traditional wastewater treatment systems, much less carbon is required using the embodiments described herein to convert nitrogen in the ammonia to nitrogen gas, water, and carbon dioxide. As such, it is feasible to remove a large percentage of carbon from sewage from Plant Influents, such that sufficient carbon is still available in the Anox-P process to convert nitrogen to the products listed above. Using other systems that treat sewage in a similar manner, it would not be possible to remove this amount of carbon, or no carbon at all, since these systems normally require the addition of carbon, in addition to the carbon present in the wastewater. Combining carbon removal pretreatment and the Anox-P process allows a highly efficient process that removes carbon, nitrogen, phosphorus, and fermentation of dissolved and particulate organic matter from wastewater without the need for external carbon sources and recovering Energy in the form of biogas.

In one embodiment, the conditions in the 612 carbon removal pretreatment process include a temperature of 18 ° C or more. When temperatures are lower than this, the same results can be obtained but with efficiencies that are slightly lower, such as a carbon removal of approximately 40-60%, rather than approximately 70%. In one case, a part of the influent sewage from plants 610 is derived before entering the carbon removal pretreatment process 612 and mixed with the pretreated stream 618. This can occur when there is a high concentration of ammonia, or high amounts of nitrogen in this stream, such as sewage with wastewater components of the food industry or some water reuse applications. Some of the incoming flows can be derived in such a way that there is more carbon in the pretreated stream 618 before it enters the Anox-P 620 process. When ammonia or nitrogen levels in general are high, more carbon is needed to remove the nitrogen in the Anox-P 620 process.

FIGURE 7 illustrates a schematic view 700 of a wastewater treatment process utilizing an upflow anaerobic mud blanket reactor (UASB), in accordance with an embodiment of the present invention. In general, a UASB reactor is a methanogenic digester that produces at least methane. A UASB reactor is a form of anaerobic digester that is typically used in wastewater treatment. An anaerobic process is used by the UASB reactor where a blanket of granular sludge is formed that is suspended from the tank. In general, wastewater flows up through the mud in the blanket so that the wastewater is treated by anaerobic microorganisms. In some cases, flocculants are used to aid in sludge blanket suspension. A byproduct comprising methane is produced, usually in high concentrations. As mentioned, biogas can be captured and used as an energy source, such as offsetting the energy requirements of the wastewater treatment plant. The temperature in the UASB reactor is typically 18 ° C or more. Additional UASB reactor conditions include a hydraulic retention time of at least 3 to 24 hours, and the mud retention time is at least 15 days.

Even more, the overflow rate is about or less than 3 ples / hour. Biochemical processes in typical UASB reactors normally include hydrolysis or solubilization, acldogenla or acetogenla, and methanogeny. The first stage of hydrolysis normally takes 10-15 days for complex organics to be solubilized so that they can be absorbed into bacterial cells when they are degraded by endoenzymes. The second stage of acldogenesis uses another group of organisms to form organic acids. The third stage of methanogeny implies that anaerobic bacteria that produce methane complete a decomposition process.

As shown in FIGURE 7, wastewater from plant influences 710 is directed to a UASB 712 reactor. As a result of the reactions taking place in the UASB 712 reactor, biogas 714, which normally includes methane, is produced, nitrogen, and carbon dioxide. Also from the UASB reactor 712 there is a stream of mud 718, which is directed to the processing of mud 726. In some cases, a part 716 of the wastewater from Plant Influents 710 is derived around the UASB reactor 712 to the pretreated stream 720. This normally occurs when the wastewater from Plant Influents 710 includes a high amount of ammonia in such a way. that more carbon is needed in the Anox-P 722 process. The pretreated stream

720 It then flows to the Anox-P 722 process, which produces the plant effluent 724.

Turning now to FIGURE 8, a schematic view 800 of a wastewater treatment process using chemically enhanced primary treatment (CEPT), according to an embodiment of the present invention, is shown. In general, CEPT involves chemicals, such as metal salts and / or polymers, which are previously added to a primary sedimentation vessel so that chemicals produce suspended particles that are grouped through coagulation and flocculation. This provides a faster and more thorough aggregation time for the particles in such a way that the efficiency of the treatment is improved. Many times, no residual metals are found in the supernatant. Some of the other chemicals used in the CEPT may include ferric chloride and aluminum sulfate, in the CEPT process a CEPT tank, such as a sedimentation tank, can be used. The advantages of CEPT with other processes include an efficient and cheaper option when compared to conventional types of treatment.

Normally, CEPT processes consist of bar sieves, a sand trap, a solid-liquid separation stage such as a sedimentation tank, which in one embodiment is a primary clarifier. Other types of solid-liquid separation steps, such as sieving or floating dissolved air can also be used.

As shown in FIGURE 8, sewage from plant influences 810 enters CEPT 812, where mud 814 from CEPT 812 is first directed to the thickening part 816, then mud 816 is directed to anaerobic digestion 820. As a result of anaerobic digestion 820, biogas 822 is formed, consisting, at least, of methane and carbon dioxide. Additionally, sludge 824 from anaerobic digestion is sent to sludge processing 826. From CERT 812, the pretreated effluent 828 is sent to the process

Anox-P 820, where plant effluent 832 is generated that has very small amounts of nitrogen, phosphorus, etc. The excess sludge 834 of the AnoxP 830 process is sent to anaerobic digestion 820 for stabilization and additional generation of methane.

With reference to FIGURE 9, a schematic view 900 of a wastewater treatment process using a one-stage active sludge system, according to an embodiment of the present invention is described. A two-stage active sludge system is usually referred to as the process.

AB, where the first stage, or stage "A" is for COD reduction using a sand tank, bioreactor, and intermediate clarifier, and the second stage, or stage "B" is for nitrification and removal of N and normally it includes a bioreactor and a secondary clarifier, however, in the embodiment of FIGURE 9, only the first stage is used while the second stage is replaced with the Anox-P process as described herein. The effluent is directed to the Anox-P process for further processing. In some embodiments up to 90% of the carbon present in the influent stream can be removed through a one-stage active sludge system. The one-stage active sludge system described in FIGURE 9 may have a mud retention time (SRT) of 0.5 days.

It is usually a high index but there is also a low SRT of less than 1 day, and sometimes as low as 0.5 days. COD removal (carbon removal) is approximately 70-80%.

As shown in FIGURE 9, sewage from plant influences 910 enters the active sludge system of a stage 912. The excess sludge 914 of this system flows to thickening 916, and then sludge 918 flows to a anaerobic digestion As a result of anaerobic digestion 920,

3 ^ Blog 922 is formed, and may include methane and carbon dioxide. The pretreated effluent 924 of the active sludge system of a stage 912 enters the Anox-P 916 process, when the plant effluent is formed by the removal of nitrogen, phosphorus, etc. FIGURE 10 illustrates a schematic view 1000 of a wastewater treatment process using a one-stage active sludge system, in accordance with an embodiment of the present invention.

FIGURE 10 illustrates a more detailed view of the active sludge system of a stage 912 of FIGURE 9. Wastewater from plant influents

1010 they are directed to a sand tank 1012 whose effluent 1014 is sent to a bioreactor 1016. From the bioreactor 1016, the effluent 1018 is sent to an intermediate clarifier 1020. The intermediate clarifier 1020 marks the end of the active sludge system of a stage, such that the pretreated effluent 1028 is sent to the Anox-10 P 1030 process for further processing. A part of the sludge 1022 of the intermediate clarifier 1020 can be recycled with the current entering the sand tank 1012 as the active return sludge 1026, and a part for further treatment such as excess sludge 1024 is derived.

Turning now to FIGURE 11, a bar graph of an energy intensity comparison using various water treatment systems is shown, in accordance with an embodiment of the present invention. Energy utilization is compared and shown in FIGURE 11. The bar graph compares a conventional nitrification denitrification process (“typical” labeling), which results from a neutral energy wastewater treatment plant (“Strass”), and finally with an anaerobic pretreatment combined with Anox-P treatment as described here (Anaerobic Pretreatment + Anox P). As shown, the energy required for anaerobic pretreatment combined with the Anox-P system is reduced when compared to other systems. Another reason for this is that the energy utilization required for aeration is approximately 50% of the other systems, although full nltrlficaclón-denitrification is still achieved, even with an external carbon source. In one embodiment, the sludge from the pre-treatment process and the residual active sludge from the Anox-P process undergo anaerobic digestion. The biogas from the digestion process can be used to generate energy at the site.

With reference to FIGURE 12, a bar graph illustrates a comparison of energy generation from biogas, in accordance with an embodiment of the present invention. The power generation shown in FIGURE 12, in one embodiment, is from the anaerobic digestion of the sludge produced by various processes. FIGURE 12 illustrates the energy conversion efficiency of energy in methane produced converted into electrical energy.

Many different arrangements of various described components, as well as components not shown, are possible without departing from the scope of the claims below. Embodiments of the technology have been described with the intention of being illustrative as opposed to restrictive. Alternate embodiments will be apparent to the readers of this description. Additionally, the alternative means to implement the aforementioned can be completed without departing from the scope of the claims below. Certain features and sub-combinations are useful and can be used without reference to other features and sub-combinations and are contemplated within the scope of the claims.