Abstract:
A liquid analyser has a reactor portion and an associated measurement portion. A sample pump is operable to deliver a liquid sample to a reactor vessel. A base pump supplys a base solution to the reactor vessel. An ozone generator supplies ozone to the reactor vessel. The liquid sample is oxidised in the reactor vessel by means of hydroxyl radicals which are generated using the base solution and ozone to reduce complex components of the liquid sample to their lowest state in solution. The oxidised sample solution is delivered to an optical detector in the measurement portion to determine the concentration of one or more selected materials such as nitrogen, phosphorous or a heavy metal in the oxidised sample solution.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to a system for the analysis of one or more selected components in a liquid, and particularly in aqueous solutions.  
       SUMMARY OF THE INVENTION  
       [0002]     According to the invention, there is provided an analytical method for measuring the quantity of one or more selected components in a liquid sample, including: 
        taking a liquid sample;     oxidising the liquid sample by means of hydroxyl radicals which are generated using a base solution and ozone for reducing complex components of the liquid sample to their lowest state in solution; and     measuring the concentration of one or more selected materials in the oxidised liquid sample solution.        
 
         [0006]     In one embodiment the method includes: 
        delivering the liquid sample to a reactor vessel;     adding a base liquid having hydroxyl ions to the liquid sample;     adding ozone to the liquid sample and mixing the solution to form hydroxyl radicals which attack chemical bonds and reduce them to their lowest state;     cutting off the ozone; and     delivering oxidised sample liquid from the reactor vessel to a detector which is operable for determining the concentration of one or more selected materials in the oxidised sample liquid.        
 
         [0012]     In another embodiment the method includes adding acid to the sample liquid in the reactor vessel and sparging to remove carbonate.  
         [0013]     In a further embodiment the method includes adding a catalyst to the sample liquid for reducing oxalate to carbonate.  
         [0014]     In another embodiment the catalyst is a metallic catalyst.  
         [0015]     In another embodiment the catalyst is manganese.  
         [0016]     In another embodiment the detector is an optical detector.  
         [0017]     In another embodiment the method includes mixing the sample liquid with an associated reagent to form a coloured complex prior to delivering the coloured complex to the optical detector and measuring the coloured complex in the optical detector to give an indication of the content of the selected material or materials present in the sample liquid.  
         [0018]     In another embodiment the selected material is a nitrogen compound.  
         [0019]     In another embodiment the selected material is a phosphorous compound.  
         [0020]     In another embodiment the selected materials are both a nitrogen compound and a phosphorous compound.  
         [0021]     In another embodiment the selected material is ammonia.  
         [0022]     In another the selected material is a heavy metal.  
         [0023]     In another embodiment the selected material is chosen from the group including iron, copper, aluminium, cobalt, magnesium, and nickel.  
         [0024]     In another embodiment the optical detector includes a light source together with at least one diode for optical measurement and a measurement cell through which light is directed from the light source for detection by the diode.  
         [0025]     In another embodiment a photodiode array is provided in the optical detector for optical measurement of the liquid samples.  
         [0026]     In another embodiment the method includes cleaning and flushing the detector between measuring different liquid samples.  
         [0027]     In another embodiment the ozone is cut off either before or after adding the acid.  
         [0028]     In another embodiment the ozone is cut off during the addition of the acid.  
         [0029]     In another embodiment some ozone is added to the liquid sample prior to adding base solution to the liquid sample.  
         [0030]     In another embodiment the method includes the step of stripping carbon dioxide from the reactor vessel and delivering the carbon dioxide through a carbon dioxide analyser for determining a value for carbon present in the liquid sample.  
         [0031]     In another aspect the invention provides a liquid analyser, including: 
        a reactor vessel;     an ozone generator having an ozone outlet connected to the reactor vessel to deliver ozone to the reactor vessel;     a sample pump having an inlet for connection to a source of a liquid to be tested, and an outlet connected to the reactor vessel;     a base pump having an inlet for connection to a base solution reservoir and an outlet connected to the reactor vessel;     the reactor vessel having an outlet for discharge of oxidised liquid sample from the reactor vessel;     means for delivering oxidised liquid sample from said outlet to a detector, said detector been operable to measure the concentration of one or more selected materials in the oxidised liquid sample.        
 
         [0038]     In another embodiment said delivering means includes a sample chamber connected to the outlet of the reactor vessel for reception of oxidised liquid sample from the reactor vessel, an analysis pump having an inlet connected to the sample chamber and an outlet connected to the detector.  
         [0039]     In another embodiment means is provided for delivering a cleaning fluid to the detector for cleaning the detector.  
         [0040]     In another embodiment means is provided for delivering a flushing fluid to the detector.  
         [0041]     In another embodiment the detector is an optical detector.  
         [0042]     In another embodiment means is provided for mixing a reagent with the oxidised sample liquid upstream of the detector.  
         [0043]     In another embodiment said means is a reagent pump having an inlet connected to a reagent reservoir and an outlet connected to an inlet of a mixer, the outlet of the analysis pump also being connected to the mixer inlet, an outlet of the mixer being connected to the detector.  
         [0044]     In another embodiment an acid pump is provided having an inlet for connection to an acid reservoir and an outlet connected to the reactor vessel.  
         [0045]     In another embodiment means is provided for cleaning a sample delivery line communicating between the sample pump and the reactor vessel. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0046]     The invention will be more clearly understood by the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:  
         [0047]      FIG. 1  is a schematic illustration of a liquid analyser according to the invention;  
         [0048]      FIG. 2  is a schematic illustration of another analyser according to a second embodiment of the invention;  
         [0049]      FIG. 3  is a schematic illustration of another analyser according to a third embodiment of the invention;  
         [0050]      FIG. 4  is a schematic illustration of another analyser according to a fourth embodiment of the invention;  
         [0051]      FIG. 5  is a schematic illustration of another analyser according to a fifth embodiment of the invention;  
         [0052]      FIG. 6  has schematic illustrations showing a sampling valve portion of the analysers in different modes of operation; and  
         [0053]      FIG. 7  has schematic views similar to  FIG. 6  showing the sampling valve in another mode of operation. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0054]     Referring to the drawings and initially to  FIG. 1  thereof, there is illustrated a liquid analyser according to the invention indicated generally by the reference numeral  1 . The liquid analyser  1  comprises a reactor portion indicated generally by the reference numeral  2  and an associated measurement portion indicated generally by the reference numeral  3 . In this case the measurement portion  3  is adapted for measurement of the total nitrogen content of a sampled liquid.  
         [0055]     A sample pump  7  has an inlet  8  connected by an inlet line  9  to the liquid to be tested. An outlet  10  of the sample pump  7  is connected by a sample delivery line  11  to a sampling valve  12  for delivery of a liquid sample to a first sample inlet  14  of the sampling valve  12 .  
         [0056]     The sampling valve  12  has an internal flow controller  15  which controls flow of liquid through the sampling valve  12 . Operation of this flow controller  15  is shown schematically in  FIG. 6 . In  FIG. 6 ( a ) the flow controller  15  is shown connecting the first sample inlet  14  with a bypass outlet  16 . The bypass  16  connects to a bypass line  18 . In this configuration a liquid sample is delivered by the sample pump  7  to the bypass line  18 .  FIG. 6 ( b ) shows the flow controller  15  rotated through 90° to connect the first sample inlet  14  with a sample valve reactor outlet  20  which communicates through a transfer pipe  21  with a sample inlet  22  of the reactor vessel  5 . In this configuration a liquid sample is delivered by the sample pump  7  to the reactor vessel  5 .  FIG. 6 ( c ) shows the flow controller  15  rotated through a further 90° to connect the outlet  20  with a base inlet  25 . The base inlet  25  connects to a base inlet line  26  leading from an outlet  27  of a base pump  28 . An inlet  29  of the base pump  28  connects via an inlet line  30  to a base reservoir  31 .  
         [0057]     The reactor vessel  5  has an outlet  35 . A circulation pump  36  is mounted in a pipe  37  connected between the outlet  35  and a recirculation inlet  38  of the reactor vessel  5 .  
         [0058]     The ozone generator  6  has an outlet line  41  leading to ozone inlet  42  of the reactor vessel  5 . An ozone outlet pipe  43  leads from the reactor vessel  5  through an ozone destructor  44  and exhaust valve  46  to exhaust.  
         [0059]     An acid pump  47  has an inlet  48  and outlet  49 . The inlet  48  connects through inlet pipe  50  with an acid reservoir  51 . The outlet  49  connects through acid delivery line  52  with the reactor vessel  5 .  
         [0060]     The reactor vessel outlet  35  also connects through a discharge line  55  with an inlet pipe  56  of a sample chamber  57 . A stop valve  57  is mounted in the discharge line  55 . An analysis pump  58  has an inlet  59  and outlet  60 . The inlet  59  connects through a suction line  61  with the sample chamber  57 . The outlet  60  of the analysis pump  58  connects through a delivery line  64  with a detector  66 . The detector  66  has a light source  67  for directing light through a translucent measurement cell  68  located in the delivery line  64 . Light transmitted by the light source  67  through the measurement cell  68  is sensed by a detector  69  located at an opposite side of the measurement cell  68 . Downstream of the measurement cell  68  the delivery line  64  leads to a drain  72 .  
         [0061]     A cleaning pump  85  has an inlet  86  connected by cleaning fluid suction pipe  87  to a cleaning fluid reservoir  88 . An outlet  89  of the cleaning pump  85  connects through a cleaning fluid supply line  90  and a cleaning fluid 3-way valve  91  with the delivery line  64 .  
         [0062]     A flushing pump  95  has an inlet  96  connected by a water suction pipe  97  to a water supply  98 . An outlet  99  of the water pump  95  connects through water delivery line  100  with a flushing valve  101  in the delivery line  64 .  
         [0063]     In operation, the sample pump  7  is operated to deliver a liquid sample through the sampling valve  12  and out through the bypass line  18 . The flow controller  15  is in the position shown in  FIG. 6 ( a ).  
         [0064]     When a fresh liquid sample is at the sampling valve  12  the flow controller  15  rotates clockwise by 90° to the position shown in  FIG. 6 ( b ) and a measured quantity of the liquid sample is pumped into the reactor vessel  5  by the sample pump  7 . Typical sample volumes are up to 10 ml and may be reduced in steps to 0.4 ml depending on the range to be measured.  
         [0065]     The flow controller  15  of the sampling valve  12  is rotated clockwise by a further 90° into the position shown in  FIG. 6 ( c ). In this position the sample remaining in the transfer pipe  21  is flushed by base delivered from the base pump  28  through the sampling valve  12 . This also raises the pH in the reactor vessel  5  to greater than pH 12 and preferably about pH 14.  
         [0066]     The circulation pump  36  is operated, the ozone generator  6  is switched on and the oxygen flow control device  45  gives a measured flow of oxygen gas through the ozone generator  6  and into the reactor vessel  5 . The sample is oxidised in the reactor vessel  5  using hydroxyl radicals.  
         [0067]     At the same time, the flow controller  15  in the sampling valve  12  is reversed through 180° returning to its start position which is shown in  FIG. 6 ( a ). The sample pump  7  is run in reverse, emptying the sample line  11 . Conveniently at the same time, the spent fluid from a previous reaction was collected in a container as it was discharged through the drain outlet  23 , a cleaning valve  110  mounted in the bypass line  18  can be activated while the sample pump  7  is running in reverse, and this acidic material is then used to wash the sample line  11  and keep it clean, without the use of additional chemicals. This can be seen more clearly in  FIG. 5 .  
         [0068]     When oxidation is complete, the acid pump  47  is operated and the pH in the reactor vessel  5  is reduced to below pH 1. Any carbon dioxide in the liquid is sparged off by the flow of oxygen.  
         [0069]     The acid also contains a small amount of catalyst, for example manganese. This is used as a catalyst in the reaction, and it is desirable as it converts oxalate to carbon dioxide gas. The purpose of the catalyst is to eliminate interference from oxalate (it also supports 100% recovery of all carbon). By using a combination of acids with and without catalyst this technique can be extended to Include measurement of oxalates in the sample.  
         [0070]     When all the carbon dioxide has been released, the stop valve  57  downstream of the reactor vessel outlet  35  opens, the exhaust valve  46  closes and the liquid in the reactor vessel  5  is dumped to the sample chamber  57 . A drain valve  62  of the sample chamber  57  is closed so that the liquid remains trapped in the sample chamber  57 .  
         [0071]     At this point nitrogen analysis of the liquid in the sample chamber  57  starts.  
         [0072]     However, in order to save time, the oxidation process as described previously repeats to prepare a new sample liquid for testing. Prior to reception of the sample liquid in the sample chamber  57  the measurement portion  3  will be made ready for analysis by filling the measuring cell  68  with clean water, delivered through the delivery line  64  by the water pump  95 , and a blank spectrum is obtained for the clean water sample.  
         [0073]     The analysis pump  58  is run until the measuring cell  68  is full of oxidised sample delivered from the sample chamber  57  by the analysis pump  58 . The light source  67  switches on. The light source  67  can conveniently be provided by a deuterium lamp, which gives a good spectral output from below 200 nm to above 400 nm. Other light sources may be used for measurement in different spectral areas. The spectrum is measured using the detector  69  which has a photodiode array. The primary measuring frequency is 217 nm, and other frequencies can be used for comparison. This spectrum is compared with the blank spectrum obtained for the clean water as mentioned above and the measurement is calculated to give a measurement of total nitrogen content in the sample.  
         [0074]     The nitrogen measuring system is then cleaned. The analysis pump  58  runs in reverse, emptying the delivery line  64 . The drain valve  62  opens, a purge valve  63  changes state so that a flow of oxygen gas from the flow controller  45  forces the liquid in the sample chamber  57  through the drain valve  62  and out to drain  23 .  
         [0075]     The cleaning valve  91  changes state, and the cleaning pump  85  is run for about two seconds flushing the measuring cell  68  with a cleaning fluid. A typical cleaning solution will be HCl in water approximately 1.8N. This cleaning fluid remains in the measurement cell  68  for about one minute. The cleaning pump  85  is then run for two seconds and then in reverse for two seconds. This has the effect of pushing the contaminated cleaning fluid down the drain  72  and at the same time recovering the cleaning fluid used to flush the contaminated cleaning fluid from the measuring cell  68 . When the cleaning pump  85  has run in reverse for approximately two seconds then the measurement cell  68  and lines from the cleaning valve  91  to the drain should be empty.  
         [0076]     The flushing valve  101  is then opened and the water pump  95  is run for about twenty seconds filling flushing water through the delivery line  64  washing any traces of cleaning fluid from the measurement cell  68  and filling the measurement cell  68  with clean water ready for measuring the blank spectrum as described previously. This process described above is then repeated at timed intervals as required.  
         [0077]     Referring now to  FIG. 2  there is shown another liquid analyser according to a second embodiment of the invention indicated generally by the reference numeral  120 . This is largely similar to the liquid analyser described previously with reference to  FIG. 1  and like parts are assigned the same reference numerals. The measurement portion  3  of the liquid analyser  120  in this case further includes a reagent pump  121  having an inlet  122  connected by a suction pipe  123  with a reagent reservoir  124 . An outlet  125  of the reagent pipe  121  discharges through pipe  126  into the delivery line  64 . A mixer  127  which optionally includes a heater or a hydrolysing unit is provided in the delivery line  64  for mixing reagent with the sample liquid discharged from the analysis pump  58  prior to delivery of the mixture to detector  66 .  
         [0078]     In operation, the liquid sample is prepared in the reactor and delivered to the sample chamber  57  in the same way as was described previously for the liquid analyser of  FIG. 1 . For nitrogen analysis the analysis pump  58  runs and after a short delay of about three seconds the reagent pump  121  runs. The fluids discharged from the pumps  58 ,  121  mix in the mixture tube  127 . When mixed, the mixture is pumped into the measuring cell  68  and measured, typically at a single wavelength. Both nitrogen and phosphate can be measured at 400 nm. The measurement is calculated from this reading and the blank spectrum. The measurement portion  3  is cleaned in the same way as described previously for the liquid analyser of  FIG. 1 . The process is repeated at timed intervals.  
         [0079]     Referring to  FIG. 3  there is shown another liquid analyser according to a third embodiment of the invention indicated generally by the reference numeral  130 . This liquid analyser  130  is largely similar to the liquid analyser described previously and like parts are assigned to the same reference numerals. In this case, the measurement portions  3  of the analysers shown in  FIGS. 1 and 2  have essentially been combined and the operation is largely similar. However, a separate nitrogen analyser pump  58 ( a ) and a phosphate analyser pump  58 ( b ) are provided for delivery of liquid from the sample chamber  57  through separate nitrogen detector  66 ( a ) and phosphate detector  66 ( b ) respectively.  
         [0080]      FIG. 4  shows another liquid analyser according to a fourth embodiment of the invention indicated generally by the reference numeral  140 . Parts similar to those described previously are assigned the same reference numerals. This is essentially the same as the liquid analyser shown in  FIG. 1  except that In this case a carbon dioxide analyser  141  is mounted in the outlet pipe  43  between the reactor vessel  5  and the ozone destructor  44 . Analysers, such as infra red analysers for example, for other materials could be inserted here also. The carbon dioxide analyser  141  measures the carbon dioxide gas released from the oxidised solution in the reactor vessel  5  when the pH is reduced to one. With an appropriate calibration the gas measurement can be converted to total carbon, or total organic carbon if the total inorganic carbon is known. The carbon dioxide analyser  141  or other analyser could similarly be inserted in any of the liquid analysers shown in  FIGS. 2, 3  and  5  if desired.  
         [0081]     In this case also a 3-way acid control valve  142  is provided in the acid delivery line  52 . This valve  142  has an inlet  143  connected to the outlet  49  of the acid pump  47 , a first valve outlet  144  connected to the reactor vessel  5  and a second valve outlet  145  which connects to the base inlet line  26  for delivery of acid to the base inlet  25  the sampling valve  12 . Normally the second outlet  145  will be shut and the first outlet  144  will be open. This configuration corresponds to the configuration shown in  FIG. 1 . The valve  142  can be switched to shut the first outlet  144  and open the second outlet  145 . This allows acid to be delivered to the reactor vessel  5  with the liquid sample initially to lower the pH. Carbon dioxide formed can be stripped off to measure total inorganic carbon present in the sample prior to switching back the valve  142  and adding the base to the reactor vessel  5 .  
         [0082]     Referring now to  FIG. 5  there is shown another liquid analyser according to a fifth embodiment of the invention indicated generally by the reference numeral  150 . Parts similar to those described previously are assigned the same reference numerals. This is largely similar to the liquid analyser shown in  FIG. 1  however in this case provision is provided for cleaning the sample delivery line  11  by collecting the spent chemicals for the reactor vessel  5 . These are collected in a vessel  151  which has a safety overflow  152  to the drain  23 . When the sample pump  7  runs in reverse and the cleaning valve  110  is switched so that the upper line  154  is open and the lower bypass drain line  155  is closed the spent chemicals are brought from the vessel  151  and drawn through the sample valve  12  and into the sample line  11  and through the sample pump  7  and out through the inlet line  9  to clean the sample loop.  
         [0083]      FIG. 7  shows operation of the valve  12  for very small samples. In  FIG. 7 ( a ) the sample liquid is pumped y sample pump  7  through valve  12  to bypass line  18 . The controller  15  is then turned through 180°, as shown in  FIG. 7 ( b ), and the sample used for analysis in the liquid container in the valve  12 . The volume of this sample is 0.08 ml. The sample is flushed into the reactor vessel  5  by the base or acid where appropriate delivered through line  26 . The controller  15  is then returned through 180° to the position shown in  FIG. 7 ( a ) for reception of the next sample.  
         [0084]     The concentration of various materials in the oxidised solution can be measured either directly or by colorimetric methods such as those outlined below.  
         [0085]     Total Phosphate Analysis  
         [0086]     The Total Phosphorus is measured by Vanadomolybdophosphoric Acid Colorimetric Method (Standard Methods for the Examination of Water and Wastewater, 20 th  Edition, 1998, APHA, AWWA,WEF. Method 4500-P B and C.). The principle of method is that in Phosphate containing solutions, Ammonium Molybdate reacts in an acid medium to form a Heteropoly Acid, Molybdophosphoric Acid. The reagent used in analysis is called Vanadate-Molybdate Reagent. In the presence of Vanadium the Vanadomolybdophosphoric Acid (yellow colour) is formed. The intensity of the yellow colour at 400 nm is proportional to the Phosphate concentration in the solution. Above techniques measure Total Reactive Phosphorus, Total Acid-Hydrolysable Phosphorus, Total Phosphorus (after oxidation with Ozone and Hydroxyl Radicals) and Total Organic Phosphorus.  
         [0087]     Total Nitrogen Analysis  
         [0088]     The Total Nitrogen in samples (oxidised with Ozone and Hydroxyl Radicals) is measured with UV Spectrophotometric Screening Method (Standard Methods for the Examination of Water and Wastewater, 20 th  Edition, 1998, APHA, AWWA,WEF. Method 4500-NO 3  B.). The principle of this technique is the absorbance of UV light at 217-220 nm is proportional to the Nitrate concentration in the solution. The oxidation with Ozone and Hydroxyl Radicals allows measuring Total Nitrogen, which includes Ammonia Nitrogen, Organic Nitrogen and Nitrite.  
         [0089]     The Total Nitrogen may also be measured by a Colorimetric Method. The reagent used in this method is an Acid Reagent. The principle of this technique is absorbance at 40 nm due to the yellow colour formation between Nitrate and Acid complex is proportional to the Nitrate concentration n the solution. After oxidation with Ozone and Hydroxyl Radicals, this technique can measure Total Nitrogen including Ammonia Nitrogen, Organic Nitrogen and Nitrite.  
         [0090]     Total Copper Analysis  
         [0091]     The Total Copper is measured by Bathocuproine Method (Standard Methods for the Examination of Water and Wastewater, 20 th  Edition, 1998, APHA, AWWA,WEF. Method 3500-Cu C.). The principle of method is that Cuprous ion forms a water-soluble orange coloured chelate with Bathocuproine Disulfonate reagent. The absorbance of the colour at 484 nm is proportional to the copper concentration in the solution. After oxidation with ozone and hydroxyl radicals, all liquid samples containing copper compounds can be analysed with this method.  
         [0092]     Total Aluminium Analysis  
         [0093]     The Total Aluminium is measured by Erichrome Cyanine R Method (Standard Methods for the Examination of Water and Wastewater, 20 th  Edition, 1998, APHA, AWWA,WEF. Method 3500-Al B.). The principle of method is that with Erichrome Cyanine R dye, Aluminium solutions forms a red to pink complex, which exhibits maximum absorption at 535 nm. The intensity of the developed colour is proportional to the Aluminium concentration in solution. After oxidation with Ozone and Hydroxyl Radicals, all liquid samples containing Aluminium compounds can be analysed with this technique.  
         [0094]     By applying similar standard measuring techniques other materials such as Cobalt, Manganese, Nickel etc. can also be analysed in the oxidised solution using the methods and apparatus of the invention.  
         [0095]     It will be appreciated that the measurement portion of the analyser can be adapted as shown in  FIG. 1  to provide a direct measurement of e.g. nitrogen in the sample using a photodiode array in the detector. Alternatively the measurement portion may be adapted for the addition of a colouring reagent, as shown in  FIG. 2 , prior to analysis and detection of a single characteristic wavelength. Different reagents can be provided for association with different flecked materials the analyser is requested to measure.  
         [0096]     In the specification the terms “comprise, comprises, comprised and comprising” or any variation thereof and the terms “include, includes, included and including” or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation and vice versa.  
         [0097]     The invention is not limited to the embodiments hereinbefore described, but may be varied in both construction and detail within the scope of the appended claims.