MXPA01005772A - APPARATUS AND METHOD FOR MEASURING NOx - Google Patents

Abstract

The invention relates to apparatus and a method for measuring Nox in biochemical processes, and to apparatus and methods for real time measuring the nitrification and/or denitrification rate of a liquid with or without suspended solids.

Description

APPARATUS AND METHOD FOR MEASURING NOx AND NITRIFICATION / DENITRIFICATION RATES IN BIOCHEMICAL PROCESSES.

FIELD OF THE INVENTION The present invention relates to apparatuses and methods for measuring amounts of NOx (nitrate (NO3) and / or nitrite (NO2)) and nitrification / denitrification rates in the liquid and controlling the treatment thereof.

BACKGROUND OF THE INVENTION The microorganisms used in sludge or waste from industrial and municipal water treatment plants decompose or degrade contaminants for the treatment of the water desired in these plants. The control and efficient operation of the process require the fast and precise determination of the information on the activity of the microorganisms. This has proven to be a difficult task in view of the wide variety of materials and contaminants that typically enter the treatment systems. Also, variations in the amount of wastewater that is treated, such as daily, weekly or seasonal changes, can dramatically change numerous important factors in the treatment process, such as pH, temperature, dissolved oxygen, nutrients and the like, alteration of which It can be highly detrimental to the proper wastewater treatment. Wastewater treated inappropriately poses serious hazards to human health. Various processes of biological nutrient removal (BNR) are frequently used in systems / plants / biochemical processes. The "BNR" is used in the following in a very generic sense, especially any biochemical process that uses microorganisms to remove nutrients. In BNR processes, contaminants in liquids such as wastewater, particularly carbon sources (measured as a biochemical oxygen demand or BOD), ammonia, nitrates, phosphates and the like, are digested by activated sludges in anaerobic, anoxic and aerobic stages (oxic), also known in the art. In the anaerobic stage, the wastewater, with or without passing through a preliminary sedimentation process, is mixed with activated return sludge (RAS), sometimes here referred to later as "mixed liquor". This is, of course, important for quantifying the various pollutants in wastewater. One of those contaminants that is important to quantify is the amount of NOx. This is because the quantification of the amount of NOx provides valuable information about the processes of nitrification and denitrification. Also, it is important to determine the nitrification or denitrification rate to facilitate the adjustment of various system parameters, such as retention time, to improve the treatment process and increase the efficiency of the treatment system in response to this important information.

BRIEF DESCRIPTION OF THE INVENTION One aspect of the invention includes a method for measuring the nitrification rate for a liquid that includes the isolation of a first liquid sample at t0; record a value of ammonia [NH3]? present in the first sample at a predetermined time ti; isolating a second sample of liquid and introducing air into the second sample of liquid after another predetermined time t2; finish the introduction of air into the second sample of liquid and adjust the pH of the second sample to t3; registering another ammonia value [NH3J2 in the second sample at a predetermined time U; and determine the nitrification rate of the liquid according to the following formula: NR =? [NHal? T where NR is the nitrification rate,? t is t2 - 13 and? [NH3] is [NH3]? - [NH3] 2. Another aspect of the invention includes another method for measuring a nitrification rate for liquids including isolating a first and second liquid samples and introducing air in the second liquid sample at t0; record a value of ammonia [NH3]? present in the first sample and finish the introduction of air in the second sample to you; record a value of ammonia [NH3] 2 present in the second sample at time t2; and determine the nitrification rate of the liquid according to the following formula: NR =? FNH-J? T where NR is the nitrification rate,? t is ti - 12 and? [NH3] is [NH3]? - [NH3] 2. The words "ammonia" ([NH 3]) and "ammonium" ([NH 4) hereinafter are frequently used interchangeably with respect to the concentration of ammonia in the aqueous phase. This is because at a given pH there is a chemical equilibrium between ammonia molecules and ammonium ions in the aqueous phase. This equilibrium is described in the following way with the equilibrium constant equal to one, at pH = 9.25.

NH3 + H2O < = NH4 + + OH "Measurements of ammonia [NH3] and ammonium [NHY] are substantially equivalent as long as the pH value of the solution is known.It is advantageous to measure the concentration of ammonium, [NrV], at a lower pH (pH < 6), while measuring ammonia concentration [NH3], is more convenient at high pH (pH> 8) The discussion of this invention sometimes refers to the concentration of ammonia as [NH3] measured with a selective ammonia probe, with the understanding that at a lower pH, this can be replaced by [NrV] measured with a selective ammonium ion probe.The invention also includes a method for measuring NOx in liquids, especially wastewater, This The method is different from other methods of analysis in that there is no need to prepare the sample by filtration or other solids removal method.The method includes isolating a sample of wastewater, adjusting the pH and / or ionic strength of the sample at a predetermined level for a predetermined time interval ti; register a value of [NO?]? present in the sample with a selective NOx probe (s); register another value of [NO?] 2 present in the sample after another predetermined time interval t2; determine the concentrations of NOx in the sample at each predetermined time interval ti and t2 according to the following formula: wherein a and b are linear coefficients of the NOx probe and the mV reading is of the selective NOx ion probe (s); determine the changes in NOx according to the following formula:? [NOJ = [NOJ2 - [NOJ ?; and determine the NOx concentration of the sample according to the following formula: [NOx] = [NOx]? ? jNOx] •? t In yet another aspect of the invention, the denitrification rate can be determined. The denitrification rate (DR) can be determined as follows: isolate a sample of liquid a to; register a value of [NOx]? present in the sample at a predetermined time ti; register a value of [NO?] 2 present in the sample at a predetermined time t2; and determine the rate of denitrification of the liquid according to the following formula: where ? [NOx] is [NOJí - [NOJ2 and? T = t2 - ti BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a schematic of a typical wastewater treatment process that uses embodiments of the invention and shows the number of sites in which the detectors can be installed through the system. Figure 2 shows a schematic front elevational view of one embodiment of the apparatus of the invention used to monitor a bioreactor tank. Figure 3 shows a schematic front elevational view of another embodiment of the apparatus of the invention used to monitor a bioreactor tank. Figure 4 shows a schematic exploded view, taken partially in section, of the wastewater sampling apparatus according to aspects of the invention. Figure 5 shows a schematic exploded view, taken partially in section, of the wastewater sampling apparatus according to another embodiment of the invention.

Figure 6 shows a schematic view, partially taken in section, of the solution dispensing apparatus according to aspects of the invention. Figure 7 is a block diagram of a method for measuring Nox and a method for calibrating a Nox analyzer according to aspects of the invention. Figure 8 is a block diagram of a method for determining the waste water denitrification rate. Figure 9 is a block diagram of a method for determining the nitrification rate of waste water. Figure 10 is a block diagram of another method for determining the nitrification rate of the wastewater.

DETAILED DESCRIPTION OF THE INVENTION In order to effectively control the operation of the BNR process, it is necessary to regulate specific process parameters based on the biological activity of the microorganisms in the anaerobic, anoxic and / or oxic stages of the treatment. Wastewater treatment plants are frequently subjected to severe transition conditions, such as diurnal variations in organic loads. The proper evaluation and control of a BNR process requires a current and accurate determination of the amount of NOx and ammonia in the mixed liquor, the nitrification rate and the denitrification rate, among other things, in a variety of environments and under a number of conditions. The apparatus for quantifying ammonia and / or NOx and / or the nitrification rate and / or the denitrification rate can be used in all stages of a WWTP or any combination thereof. The incorporation of an apparatus in a typical WWTP is shown schematically in Figure 1. The NOx and / or ammonia measurements can be taken at any point or site in the system shown in Figure 1. This includes multiple measurement sites within a selected stage, if desired. The application and general use of the apparatus in the anaerobic, anoxic and / or aerobic stages of a typical wastewater treatment plant will now be discussed. One embodiment of the apparatus for sampling wastewater is shown in Figure 2. A bioreactor tank 1 (or, alternatively, a wastewater channel) contains wastewater 2 and / or sludge. The detection apparatus is mounted on top of the bioreactor tank 1 and extends into the wastewater 2. The apparatus includes a central control and an analysis unit 20 connected to an optional monitor / computer 13 by a wired or wireless connection 22. Similarly, the central control and the analysis unit 20 are connected to the detection probe 10 by means of a wired connection 24. The container of the motor 26 is also connected to the central control and to the analysis unit 20 by means of of a wired connection 28. The energy is supplied to the motor container 26 also by a wired connection 28. The detection probe 10 is placed inside the detection chamber 8 and electrically connected to the central control and the analysis unit 20 to detect changes in the amount of ammonia or ammonia or NOx concentration in the wastewater samples depending on the configuration. At a low pH, a preferred ammonium ion selective probe is an ammonium probe manufactured by HACH or NICO. At an average pH a preferred ammonia detection probe is an ammonia gas probe also manufactured by NICO or HACH. A preferred probe or probes of the preferred NO3 and / or NO2 ion are manufactured by NICO. Of course, other devices can be used as probes while the same or similar detection capabilities are available. The optional monitor / computer 13 may be of any suitable type such as a personal computer or the like. The device 52 consists of two containers (one stores ammonia or NOx calibration solution and the other stores pH adjusting solution and / or ionic strength adjustment solution) and a supply device for each, for example, a pump . The device 52 is connected to the central control and to the analysis unit 20 by the wire 54. The device 52 provides calibration of ammonia or NOx and pH adjusting solution and / or solution of adjustment of the ionic resistance to the liquid (e.g. residuals) in the detection chamber 8 connected by the tube 53 through the feed holes 55. The pH adjusting solution, typically a base for the average pH and an acid for the low pH, can be selected from a large variety of solutions that alter the pH. The bases include NaOH, KOH and the like. The acids include HCl, acetic acid and the like. The solution of ionic strength adjustment, typically solution of AI2 (SO) 3, or solution of AI2 (SO) 3, Ag2SO4, H3BO3, and sulfamic acid, can be selected from a wide variety of solutions for the adjustment of ionic strength of the wastewater sample. The device 52 is described in detail below in conjunction with Figure 6. The sampling unit 11 is mounted on a movable support 30 which is able to move substantially vertically up and down to move the sampling unit 11 inside. and outside the wastewater 2. The precise structure of the mobile support 30 is not critical as long as the preferred capacity or mobility of the sampling unit 1 1 is achieved. The detection probe 10 has its detection end located inside the detection chamber 8. The detection chamber 8 has an opening 66 and a movable adjacent cover 32 which moves vertically up and down along the channels guide 34 and close or seal the opening 66. Figure 3 shows another embodiment of the apparatus for sampling wastewater. The modality shown in Figure 3 is similar to that of Figure 2 except that the apparatus is provided by providing additional sampling capabilities. Specifically, another detection chamber 8 having a probe is mounted, adjacent to the detection / probe camera configuration shown in Figure 2. Of course, additional connections are provided to the control and analysis unit 20 and the solution provided by the device 52. Figure 4 shows the detection chamber 8 having a detection probe 10A with a detection end 50A. The detection probe 10A can be an ammonia, ammonium detection probe or a NOx detection probe. The detection chamber 8 also has an optional detection probe 10B with a detection end 50B. The optional detection probe 10B is a probe for pH. The sensing chamber 8 further away the feed holes 55A and 55B. The feed device 52 feeds the pH adjusting solution and / or the ion resistance adjustment solution into the detection chamber 8 through the feed hole 55B. The feed device 52 feeds ammonia or NOx into the detection chamber 8 through the feed hole 55A. The propeller 48 is located internally of the detection chamber 8 and stir or agitate the samples when the probes 10A and 10B are in operation. The cover 32 is in an open position which, when closed, covers the opening 66. The propeller 48 is connected to the engine container 26 by means of a series of coaxial tubes 102, 104 and 106. An adapter 108 and a sleeve of axial thrust support 1 12 contained within and fixed to the intermediate tube 104. The outer tube 102 is mounted to the base 101. The adapter 108 is fixed to the threaded rod 110 to either open or close the cover 32 depending on the direction of the motor of the linear drive motor 1 16. The intermediate pipe 104 travels axially only if the dredge induced in the intermediate pipe 104 exceeds a quantity of torque required by linear drive motor 1 16 to rotate on the threaded rod 110. This dredge can be induced by the propeller 48 fixed to the intermediate tube 104 and / or any bushing or other equipment in contact with the intermediate tube 104. The axial thrust support sleeve 112 holds the support 114 which carries a tension to of the central tube 106 when the cover 32 is closed. The support 114 allows the intermediate tube 104 to rotate independently of the central tube 106 and transfers the axial movement of the tube 104 to the central tube 106. The outer tube 102 supports both the base 101 and the chamber 8 while protecting the internal parts. The chamber 8 is substantially sealed to the outer tube 102 and when the cover 32 is pulled against the chamber 8 the interior space of the chamber 8 is sealed. When the linear drive motor 116 rotates in one direction the threaded rod 1 10 travels downwards, pushing the cover 32 open. When the nut 118 reaches the axial thrust support 119, the threaded rod 110 does not travel further axially and this causes the intermediate tube 104 to substantially equalize the speed of the motor. The chamber 8 is then in an open condition and the propeller 48 induces an exchange of fluids between the interior and the exterior of the chamber 8. When the linear driver motor 16 rotates in the opposite direction, the threaded rod 110 travels upward, pulling cover 32 closed. When the chamber 8 is closed, the axial movement of the threaded rod 1 10 is prevented by the tension on the intermediate tube 104. This causes the intermediate tube 104 to rotate at the same speed as the motor 116. The chamber 8 is then in the closed position such that the fluid is retained within the chamber 8 while being constantly mixed by the propeller 48. Figure 5 shows another embodiment of a configuration of the chamber 8 containing an optional additional detection probe. All other components are the same as shown in Figure 4. The optional detection probe 10C has a detection end 50. The optional detection probe 10C is a probe for dissolved oxygen. This is connected to the control and analysis unit 20 by means of convention 24C. Referring to Figure 6, the device 52 is constructed to accurately dispense various solutions to other components of the total system. The device 52 includes a housing 198 and preferably contains two solution containers 200 and 202, although it may be configured to contain only one or more than two solution containers. Containers 200 and 202 have corresponding solution pumps 204 and 206 connected to their respective solution containers with feed lines of pumps 208 and 210. The pump supply lines are preferably equipped with a pointed or needle-like device 212 and 214 extending through the housing 198. Each solution container is preferably made of a plastic material that is punctured by the needle or pointed device, whereby when the solution container is lowered on top of the needle, it drills the container to provide access to the solution. More preferably, the container is formed to push the liquid in the solution container to flow towards the needle device. Since it is important that the solutions remain free of contamination and that they retain their precise concentrations, for measurement purposes, it is important that they are sealed. However, when emptying the container, it is very preferred to provide a means for the air to fill the space created within the container when the solution is removed. This can be done by a number of means, although it is highly preferred to use the needle type device 216 and 218 to pierce the solution containers 200 and 202 and provide air access to the interior of the solution containers. The needle type device 216 and 218 are connected to the air lines 230 and 232.

Each pump 204 and 206 connected to the respective solution containers is connected to the control and analysis unit 20 (not shown in Figure 6), by line 222 and 224. Pumps 204 and 206 are also connected to a chamber ( s) of detection 8 (not shown in Figure 6), by means of the supply lines of the solution to supply the quantity of dosed or precise solution to the detection chamber (s) 8 at the specific time. Of course, the solution inside the containers may vary. However, the preferred solution (s) are ammonium chloride or sodium nitrate. The pH and / or the solution (s) for adjusting the ionic strength can also be kept inside the containers. Other solutions can be used according to the particular need. The solutions can, of course, be in various concentrations as needed. He does not? it is frequently the main part of the pollutants in wastewater. Therefore, a quick and easy method for real-time measurement of NOx in wastewater is highly advantageous. Accordingly, one aspect of the invention involves measuring the amount of NOx in the wastewater. This is done by a method of measuring NOx in liquids that includes isolating a sample of liquid; adjust the pH and / or the ionic strength of the sample at time t0; recording a NOx value present in the sample with NOx selective probe (s) at a predetermined time ti; registering another NOx value present in the sample after another predetermined time t2; determining NOx concentrations in the sample at each predetermined time ti and t2 according to the following formula: wherein a and b are linear coefficients of the NOx probe (s); determine the change in NO? in the sample according to the following formula: determine the NOx concentration of the sample according to the following formula: [NOx] or = [NOx]! -? TNOxl • (- 10)? T This method is shown in the upper part of the flow chart shown in Figure 7. The NOx analyzer can be calibrated according to the lower portion of the block diagram shown in Figure 7 and according to the following method: Collect a sample of mixed liquor from the wastewater treatment tank and conduct the NOx analysis as described above, except that the sample is not discharged to the treatment tank after the NOx concentration is measured. Intermediate parameters and results such as [NOx] ?, [NOx] 2, mVi, mV2,? [NOx] /? T are saved for use in the calibration step. b) After the NOx concentration is measured, a predetermined volume of nitrate or nitrite solution is injected into the sample container such that the concentration of NOx in the container increases by a? [NOx] c1, (e.g. 0.5 ml of 1000 ppm of NaNO3 or NaNO2 solution for? [NO?] C1 = 1 ppm, assuming that the sampling chamber has a volume of 500 ml.) C) Wait until t3 seconds to take the third mV reading of the probe [mV3]. d) Inject a second dose of calibration solution such that the concentration of NOx increases by a? [NOx] c2, (for example, 2.0 ml of 1000 ppm NaNO3 solution or NaNO2 for? [NOx] c2 = 5 ppm, taking note the first dose of calibration solution.) e) Wait until seconds to take the fourth mV reading of the probe [mV4]. f) Use the following equations to calculate the linear coefficients of log [NOx] 0 - (ta-to)? [NOx] /? T +? [NOx] c1 = a • mV3 + b log [NOx] 0 - (-tb)? [NOx] /? T +? [NOx] c2 = a • mV4 + b g) Use the recently obtained a and b to calculate [NOx] 0 of mV0. If the newly calculated [NOx] 0 substantially corresponds to the original [NOx] or, then the calibration is judged successful, otherwise, use the newly calculated [NOx] 0 to repeat the calibration process. The calibration is considered complete when the difference between [NOx] 0 'and [NOx] 0i + 1 is within a predetermined acceptable range. h) Download the sample to the treatment tank and start a new measurement cycle. i) NOx analyzer callibration can be carried out as frequently as each measurement cycle, or daily. The default calibration frequency is preferably once a day. This is even more advantageous for determining the nitrification rate. There are two preferred methods for making such a determination according to the invention. In a first modality, the method includes: a) isolating a first sample of liquid at t0 b) measuring the concentration of ammonia [NH3]; or ammonium [NH +]? present in the sample at a predetermined time ti, then release the first sample to the treatment tank; c) isolating a second liquid sample and introducing air into the second liquid sample after another predetermined time t; d) finishing the introduction of air in the second liquid sample and adjusting the pH of the second sample to t3; e) recording another value of ammonia [NH3] 2 or ammonium [NH4 +] 2 in the second sample at a predetermined time; and f) determine the nitrification rate of the liquid according to the following formula: NR =? [NH3] /? T OR NR =? [NH4 +] /? T where NR is the nitrification rate,? t is t3 - 12 and? [NH3] is [3 - [NH3] 2 or? [NH +] is [NH4 +] t - [NH4 +] 2. This method is represented in the flow chart shown in Figure 10. In the second mode which uses two sampling units (as shown in Figure 3), the method includes: a) isolating a first and second sample of liquid and introducing air in the second liquid sample at t0; b) measure the concentration of ammonia [NH3]? or ammonium [NH4 +] present in the first sample; c) finish the introduction of air into the second sample to you; d) measure the concentration of ammonia [NH3] 2 present in the second sample; and e) determine the nitrification rate of the liquid according to the following formula: NR =? [NH3] /? T or NR =? [NH4 +],? T where NR is the nitrification rate,? t is ti - t0 and? [NH3] is [NH3]? - [NH3] 2 or? [NH4 +] is [NH4 +]! - [NH4 +] 2. This method is outlined in the flow chart shown in Figure 9. The preferred operation of the ammonia analyzer in the measurement mode is as follows: a) collecting a sample of mixed liquor from the wastewater treatment tank. b) Inject pH adjusting solution to bring the pH of the aqueous phase to approximately 12.0. This can be done either through a predetermined amount or through feedback control by means of a pH probe. This is registered at time zero, t0. c) Wait until you have seconds to take the first mVi reading of the ammonia probe. d) Wait until t2 seconds to take the first mV reading of the ammonia probe. e) Use the following equation to calculate the ammonia concentrations of mV and mV2, where a and b are linear coefficients of the ammonia probe. a • mV + b [NH3] = 10 f) The amount of NH3 released from the sample is calculated as: ? [NH3] /? T = [[NH3] 2 - [NH3]? ] / (t2 - ti) g) The ammonia concentration of the sample is calculated as: [NO3] 0 = [NO3]? -? rNO3l • (ti - 10)? t h) After the measurement of the ammonia concentration, the sample is discharged to the treatment tank, and a fresh sample is taken for the next analysis. The ammonia analyzer is preferably calibrated according to the following method; a) Collect a sample of mixed liquor from the wastewater treatment tank and conduct the ammonia analysis as described above, except that the sample is not discharged to the treatment tank after the ammonia concentration is measured. Intermediate parameters and results such as [NH3]?, [NH3] 2, mVi, mV2,? [NH3] /? T are stored for use in the calibration step. b) After the ammonia concentration is measured, a predetermined volume of ammonia solution is injected into the sample container such that the concentration of ammonia in the container is increased by a? [NH3] c1, (eg, 0.5 ml of 1000 ppm of NH4CI-N solution for? [NH3] c1 = 1 ppm, considering that the sampling chamber has a volume of 500ml.) c) Wait at t3 seconds to take the third mV reading of the probe ( mV3). d) Inject a second dose of calibration solution such that the concentration of ammonia is increased by a? [NH3] c2, (for example, 2.0 ml of 1000 ppm of NH4CI-N solution per? [NH3] c2 = 5 ppm , taken into account from the first dose of calibration solution.) e) Wait until seconds to take the fourth mV reading of the probe (mV4). f) Use the following equations to calculate the linear coefficients of ammonia, a and b: log [NH3] 0 + (t3-t0)? [NH3] /? T +? [NH3] c1 = a • mV3 + b log [NH3] 0 + (-to)? [NH3] /? T + a • mV4 + b g) Use recently obtained a and b to calculate [NH3] 0 of mV0. If the newly calculated [NH3] 0 corresponds substantially to the original [NH3] 0, then the calibration is judged successful, otherwise, use the [NH3] 0 calculated again to repeat the calibration process. The calibration is considered complete when the difference between [NH3] 0 'and [NH3] 0i + 1 is within a predetermined acceptable range. h) Download the sample to the treatment tank and start a new measurement cycle. The calibration of the ammonia analyzer can be carried out as frequently as each measurement cycle, or daily. The default calibration frequency is preferable once a day.

It is also advantageous to determine the denitrification rate (DR). The determination of DR depends on NOx concentrations. this is calculated according to the method shown in the flow chart of Figure 8. The method includes: a) isolating a sample of liquid at t0; b) measuring the concentration of NOx ([NOx]?) present in the sample at the predetermined time; c) measuring the concentration of NOx ([NOx] 2) present in the sample at a predetermined time t; and d) determining the rate of denitrification of the liquid according to the following formula; DR =? [NO?? T where ? [NOx] is [NOx]? - [NOx] 2 and? T = t2 - ti. A practical application that determines the nitrification rate NR in the control and monitoring of wastewater treatment processes is to evaluate and optimize the operation of the bioreactors. When the NR is measured on a real time basis, the information will respond as follows: 1) If the activated sludge has a nitrification ability, that is, the presence of nitrification bacteria in the biomass. A low or near zero NR value indicates that the nitrifying population in the biomass is low or does not exist, while a high value of NR indicates an appropriate nitrification process. 2) Under the current of wastewater that the plant loads, to what degree has nitrification been achieved ?. When determining the NR, the time required for the proper removal of ammonia can be calculated based on the nutrient load. This required nitrification time can be compared to the current hydraulic retention time in the bioreactor to see if the appropriate nitrification can be obtained. 3) What is the best aeration rate to achieve the desired degree of nitrification ?. The optimum air supply rate can be reached when the air supply calculated from the NR value equals the actual air demand in the nitrification process. Over aeration will result in deterioration of biomass and energy waste, while under aeration can cause improper treatment of wastewater. Both cases can be avoided with an appropriate aeration control with the NR as one of the control parameters. 4) What is the best mean residence time in the cell (MCRT) of the biomass in the bioreactor for the desired degree of nitrification? The population of nitrification bacteria can be estimated from the value of the NR. This estimate allows the operator to determine the appropriate mean residence time in the cell (MCRT) for the desired growth of the nirification bacteria in the biomass. The MCRT can be used to control the waste of the activated sludge. 5) What level of biomass concentration is needed to be maintained in the bioreactor to achieve nitrification ?. When the value of the NR is high, it means a high population of nitrification bacteria, the plant may have to use a low concentration of biomass in the bioreactor to achieve nitrification, while a lower NR alerts to maintain a higher concentration of biomass in the bioreactor. 6) The measurement of the NR also allows the operator of the wastewater treatment plant to estimate that both the wastewater affluent plant can deal with the existing installation, of the above plan the expansion or modification of the plant.

The denitrification rate, DR, can be used in the monitoring and control of biological denitrification within the wastewater treatment process. When DR is measured on a real time basis, the information can answer the following: 1) What is the denitrification capacity in the bioreactor? Based on the measured value of the DR, information on the nitrate loading to the anoxic zone, the hydraulic retention time in the anoxic zone, and the desired degree of denitrification, one can estimate how much of the wastewater can be treated by the plant. 2) What is the optimal rate of internal recycling for the anoxic zone ?. The nitrate charge for the anoxic zone mainly comes from the internal recycling of the nitrified mixed liquor at the end of the aerobic zone of a bioreactor, referring to Figure 1 for the location of the internal denitrification recycling. Knowing the DR allows the precise control of the internal recycling, thus achieving the full use of the anoxic zone and avoiding the waste of over-recycled pumping energy. 3) Is there any factor that limits the achievement of optimal denitrification ?. The measurement of the DR allows the evaluation of denitrification activity in terms of carbonaceous nutrients and nitrate loads. A low DR indicates an endogenous denitrification, since the carbonaceous nutrient is limited. The increased carbonaceous nutrient load improves the denitrification process. A high DR, on the other hand, predicts an active denitrification state. Increasing internal recycling improves the total removal of nitrogen from the wastewater stream. The invention can be applied to any kind of microbial process including, but not limited to, purification of wastewater (municipal, industrial and the like), biological pharmaceutical production, mixing, fermentation or any other process involving populations of mixed or pure microorganisms. .

Claims (27)

CLAIMS.

1. A method for measuring a nitrification rate for a liquid, comprising: a) isolating a sample of liquid a to; b) measure the concentration of ammonia [NH3]? or ammonium [NH4 +]? present in the sample at a predetermined time ti; c) isolating another sample of liquid and introducing air into said other liquid sample after another predetermined time t2; d) finishing said air introduction in said other liquid sample and adjusting the pH of said other sample to t3; e) measure the concentration of ammonia [NH3] 2 or ammonium [NH +] 2 in said other sample at a predetermined time W, and f) determine the nitrification rate of the liquid according to the following formula: NR =? INHgl or NR =? fNH 1? t? t where NR is the nitrification rate,? t is t3 - 12 and? [NH3] is [NH3]? - [NH3] 2 or? [NH4 +] is [NrVli - [NH4 +] 2.

2. The method for measuring a nitrification rate according to claim 1, characterized in that it further comprises the repetition of steps a) -f) at selected intervals to determine changes in the nitrification rate.

3. The method for measuring a nitrification rate according to claim 1, further characterized in that said ammonia [NH3] values are determined with an ammonia selective probe.

4. The method for measuring a nitrification rate according to claim 1, further characterized in that said ammonium [NH +] values are determined with an ammonium ion selective probe.

5. The method for measuring a nitrification rate according to claim 3, characterized in that it further comprises periodically calibrating said ammonia selective probe.

6. The method for measuring a nitrification rate according to claim 4, characterized in that it further comprises periodically calibrating said selective ammonium ion probe.

7. The method for measuring a nitrification rate according to claim 1, further characterized in that said liquid contains organic matter.

8. The method for measuring a nitrification rate according to claim 7, further characterized in that at least a portion of said organic matter is capable of releasing ammonia.

9. The method for measuring a nitrification rate according to claim 1, further characterized in that said liquid is unfiltered.

10. The method for measuring a nitrification rate according to claim 1, further characterized in that said liquid is wastewater. 1 1.

A method for measuring a nitrification rate for liquids comprising: a) isolating a first and second liquid samples and introducing air into said second liquid sample at t0; b) measure the concentration of ammonia [NH3]? or ammonium [NH +]? present in said first sample; c) finishing the introduction of air in said second sample to you; d) measuring the concentration of ammonia [NH3] or ammonium [NH +] present in said second sample; and e) determine the nitrification rate of the liquid according to the following formula: NR =? fNHal or NR =? [NH4J? t? t where NR is the nitrification rate,? t is ti - 12 and? [NH3] is [NH3]! - [NH3] 2 or? [NH +] is [NH4 +]? - [NH4 +] 2.

The method for measuring a nitrification rate according to claim 1, characterized in that it further comprises the repetition of steps a) -d) at selected intervals to determine changes in the nitrification rate.

13. The method for measuring a nitrification rate according to claim 1 1, further characterized in that said ammonia values are determined with a selective ammonia probe.

14. The method for measuring a nitrification rate according to claim 1 1, further characterized in that said ammonium values are determined with a selective ammonium ion probe.

15. The method for measuring a nitrification rate according to claim 13, characterized in that it also comprises periodically calibrating said selective ammonia probe.

16. The method for measuring a nitrification rate according to claim 13, characterized in that it further comprises periodically calibrating said selective ammonium ion probe.

17. The method for measuring a nitrification rate according to claim 1 1, further characterized in that said liquid contains organic matter.

18. The method for measuring a nitrification rate according to claim 17, further characterized in that at least a portion of said organic matter is capable of releasing ammonia.

19. The method for measuring a nitrification rate according to claim 1, further characterized in that said liquid is unfiltered.

20. The method for measuring a nitrification rate according to claim 1 1, further characterized in that said liquid is wastewater.

21. A method of measuring NOx in liquid comprising: a) isolating a sample of liquid; b) adjusting the pH and / or the ionic strength of said sample to time t0; c) recording an mVi value present in said sample with a selective NOx probe at a predetermined time ti; d) registering another mV2 value present in said sample after another predetermined time t2; e) determining the concentrations of NOx in said sample at each of the predetermined times ti and t2 according to the following formula: wherein a and b are linear coefficients of the NOx probe; f) determine the changes in NOx in the sample according to the following formula:? [NOx] = [NOx] 2 - [NOx] 1; and g) determine the NOx concentration of the sample according to the formula: following [NOx] = [NOx]! -? TNOxl • (ti - to)? T where? T is t2 - ti.

22. The liquid NOx measurement method according to claim 21, characterized in that it further comprises discharging said sample and repeating steps a) - g).

23. The liquid NOx measurement method according to claim 21, characterized in that it further comprises periodically calibrating said nitrate and / or nitrite selective probe.

24. A method for measuring a denitrification rate for a liquid comprising: a) isolating a sample of liquid at t0; b) measure the concentration of [NOx]? present in said sample at a predetermined time ti; c) measuring the concentration of [NOx] 2 present in said sample at a predetermined time t2; and d) determine the rate of denitrification of the liquid according to the following formula: DR =? [NOx] /? t, Where? [NOx] is [NOx]? - [NOx] 2 and? T = t2- ti.

25. The method defined in accordance with claim 24, further characterized in that it comprises steps a) -d) at selected intervals to determine changes in the nitrification rate.

26. The method defined in accordance with claim 24, further characterized in that said values of [NOx] are determined with a nitrate and / or nitrite selective probe.

27. The method defined in accordance with claim 24, further characterized in that said liquid is wastewater.