Device for analyzing fluid samples

An analyzing system for analyzing fluid samples includes a measuring buoy immersible in a body of fluid to be tested. The buoy forms a sample chamber in which samples of the fluid are to be tested. The sample chamber communicates with a settling chamber through a chamber opening, and the settling chamber communicates with the body of fluid through a floor opening formed in the buoy below the chamber opening. A gas exchange apparatus communicates with the sample chamber and with a source of air or gas for introducing the air or gas into the sample chamber to drain sample fluid therefrom, and for discharging the air or gas from the sample chamber to admit sample fluid into the sample chamber from the settling chamber. A testing device is disposed in the sample chamber for testing the sample fluid, and is connected to a control and analysis device.

BACKGROUND OF THE INVENTION
 The invention relates to a device for analyzing fluid samples consisting of
 a sample chamber containing at least one testing device, which comprises a
 control and analysis device and a filling and draining device, through
 which, respectively, a fluid sample taken from a quantity of fluid is fed
 into the sample chamber and removed from it.
 A typical area of application for such testing equipment is in waste water
 analysis. In this type of application, a fluid sample is taken from the
 waste water and tested in the sample chamber. Frequently, a reagent is
 added in the sample chamber and its reaction with the fluid sample is
 completed and measured. Gas-selective or ion-selective sensors, pH
 sensors, photo-optical sensors, and other sensors are commonly used for
 tests performed inside the sample chamber. A gaseous reaction product
 which develops during the reaction can be fed into a measuring device
 designed specifically for measuring this product, such as a CO.sub.2
 detector (published journal article by M. Levermann, "TOC Testing in an
 On-line Process", publication "Chemie, Umwelt, Technik" [Chemistry,
 Environment, Technology], 94, pages 12-15).
 To fill the sample chamber, the fluid sample must be conveyed from the
 available quantity of fluid, such as waste water, through a supply line
 An unavoidable feature of such testing, particularly of waste water
 samples, is that deposits form in the fluid lines used to fill and drain
 the sample chamber. Unless they are routinely flushed--a relatively
 expensive procedure--there is a risk that these lines may become clogged.
 Consequently, the objective of the invention is to design a device of the
 type specified initially in such a way that the sample chamber can be
 easily filled and drained without running the risk of clogging the fluid
 lines and incurring the substantial expense of rinsing.
 SUMMARY OF THE INVENTION
 According to the invention, this objective is solved in that the sample
 chamber is arranged in a measuring buoy immersible in a quantity of fluid
 and is connected to the outside of the measuring buoy via a chamber
 opening, that at least one testing device is arranged in the measuring
 buoy, and that the filling and draining device exhibits a gas exchange
 apparatus with which a gas which displaces the fluid sample is fed into
 and removed from the sample chamber.
 Moving the sample chamber from a measuring device located outside the fluid
 to a measuring buoy immersible in the quantity of fluid eliminates the
 need for fluid lines which tend to become clogged. The sample chamber
 located inside the fluid being tested can be directly filled and drained
 without the need for any fluid lines.
 As at least the section of the measuring buoy that contains the sample
 chamber is immersed into the fluid being tested, removing the gas in the
 sample chamber is sufficient for filling the sample chamber, i.e., by
 opening the sample chamber to the atmosphere, in the simplest case. The
 hydrostatic pressure of the fluid surrounding the measuring buoy forces
 the fluid sample into the sample chamber. To empty the sample chamber, a
 pressurized gas, such as air, is supplied by the gas exchange device to
 press the fluid sample out of the sample chamber. The intensity of the gas
 supply can be chosen so as to produce turbulence in the fluid sample in
 the sample chamber, thereby effectively rinsing and cleaning the sample
 chamber and the chamber opening with very simple means. This essentially
 eliminates clogging of the chamber opening.
 The control and analysis device can be positioned in a remote location
 relative to the measuring buoy and be linked to the buoy by cables or
 lines. If need be, reagents and/or gases are--in addition to electric
 measuring signals and, if applicable, electric control impulses or an
 electric power supply--transported via lines that connect the measuring
 buoy with the remotely placed control and analysis device. Compared to the
 transport of fluid samples, the transport of these materials is completely
 unproblematic and does not lead to the risk of contamination or clogging.
 Alternatively, the control and analysis device can also be arranged in the
 measuring buoy.
 Preferably, at least one reagent dosing device, which opens into the sample
 chamber and is connected to a reagent source located outside the measuring
 buoy via a hose assembly, is arranged in the measuring buoy. As a result,
 the types of tests that require the chemical reaction of the fluid sample
 with one or more reagents--which is often the case in waste water
 analysis--can also be performed in the sample chamber. As there is no risk
 of the transport lines for fluids or gaseous reagents becoming clogged,
 these lines can also be installed across relatively large distances
 between the measuring buoy and a supply unit.
 Preferably, the gas exchange device exhibits a gas pump arranged in the
 measuring buoy and connected to the sample chamber which can be connected
 to a gas source located outside the measuring buoy via a hose assembly. As
 this type of hose assembly is also not subject to the risk of clogging, it
 can easily be installed across larger distances.
 According to a preferred embodiment of the invention, the sample chamber
 opening may open into a settling chamber with a hole in its bottom which
 is arranged underneath the sample chamber in the measuring buoy. It may be
 necessary to separate the solid matter component prior to analysis,
 particularly when analyzing the aqueous component of activated sludge in a
 sewage treatment plant. The settling chamber connected upstream from the
 sample chamber is used to hold the fluid sample during a filling pause, so
 that the activated sludge settles or concentrates in the lower portion of
 the settling chamber before the fluid sample, which has been pre-cleaned
 in this manner, is allowed to enter the sample chamber.
 To control this filling process over time, a fill level sensor is
 preferably positioned near the chamber opening connecting the settling
 chamber to the sample chamber and is connected to the control unit for the
 gas exchange device. The fill level sensor is used to determine when the
 settling chamber is full. When this occurs, the filling process is
 interrupted so that the sludge component can settle in the settling
 chamber. This filling process is resumed once this preset time period has
 expired.
 To analyze activated sludge in which gas bubbles are constantly rising, it
 has proven to be advantageous to place a deflection object at a distance
 from the floor opening of the settling chamber which extends beyond the
 perpendicular projection of the perimeter of the floor opening on all
 sides. This deflection object prevents gas bubbles from entering the
 settling chamber and the sample chamber.
 According to another advantageous embodiment of the invention, the sample
 chamber is linked to a gas supply line for a reaction gas, the chamber
 opening can be locked by means of a valve, and a gas discharge line with a
 locking valve runs from the sample chamber to an analysis device located
 at a distance from the measuring buoy. This makes it possible to subject
 the fluid sample drawn into the sample chamber to a reaction with the
 reaction gas when the chamber opening is locked, and to subsequently
 remove this reaction gas from the measuring buoy and convey it to a
 remotely positioned analysis device, so that the necessary analysis can be
 completed there.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
 The device for measuring the NH.sub.4 content of water depicted in FIGS. 1
 and 2 exhibits a measuring buoy 2 immersible in the waste water 1 being
 tested which is connected, via schematically indicated lines 3, to a
 remotely positioned control and analysis device 4. A sample chamber 5 is
 arranged in the measuring buoy 2 which contains the waste water sample to
 be tested. A stirring apparatus 6 protrudes into the sample chamber 5. The
 sample chamber 5 has a chamber opening 7 in its floor through which the
 sample chamber 5 can be filled and emptied. A settling chamber 8 with a
 volume which exceeds that of the sample chamber is positioned below the
 chamber opening 7 in the measuring buoy 2. The settling chamber 8 has a
 floor opening 9, under which a deflection object 10 is positioned at a
 distance. The deflection object 10 extends beyond the perpendicular
 projection of the perimeter of the floor opening 9 on all sides, thereby
 preventing rising gas bubbles from entering the settling chamber 8 through
 the floor opening 9. A fill level sensor 11 is positioned near the chamber
 opening 7 that connects the settling chamber 8 with the sample chamber 5.
 In the illustrative example depicted in FIGS. 1 and 2 a testing device
 invention of, an NH.sub.3 probe 12, which is connected to the control and
 analysis device 4, protrudes into the sample chamber 5. A hose assembly 14
 leads from a reagent source (not depicted) positioned outside the
 measuring buoy 2 to a solenoid valve 15, which forms a reagent dosing
 device for delivering a reagent into the sample chamber 5. In an analogous
 manner, a hose assembly 17 with a locking solenoid valve 16 is used to
 deliver calibration standard to the sample chamber 5.
 A pH probe 18, which also protrudes into the sample chamber 5, is used to
 measure the pH value in the fluid sample. An air line, which contains a
 solenoid valve 19, also opens into the sample chamber 5.
 To analyze a waste water sample, the sample chamber 5 and the settling
 chamber 8 are emptied by adding air or gas, which is achieved by opening
 the solenoid valve 19. When a solenoid valve 20 also connected to the
 sample chamber 5 is opened, the air contained in the sample chamber 5 and
 in the settling chamber 8 escapes through a hose assembly 21, and the
 settling chamber 8 is filled until the fill level sensor is activated.
 After a settling pause, during which the sludge component in the fluid
 sample and, if applicable, other precipitable substances have settled to
 the bottom of the settling chamber 8, the solenoid valve 20 is reopened
 and the effects of the hydrostatic pressure of the surrounding waste water
 result in the filling of the sample chamber 5.
 Then the solenoid valve 15 is opened, allowing caustic solution to flow
 into the sample chamber 5 until the pH level at the probe 18 has reached a
 value of about 11. At a pH level of 11, the entire NH.sub.4, once
 adequately mixed, is present in the form of NH.sub.3 and is measured by
 the NH.sub.3 probe 12 and subsequently analyzed by a computer in the
 control and analysis device 4. A new measuring cycle can then be performed
 as described above.
 To calibrate the system, a standard line 17 can be connected to the sample
 chamber 5 via a solenoid valve 16, thus allowing a standard fluid to be
 fed into the chamber and an automatic calibration to be performed.
 An NO.sub.3 measuring device (not depicted) may be similarly equipped. In
 this case, an NO.sub.3 probe replaces the NH.sub.3 probe 12 described
 above. Furthermore, an additional conductivity probe is mounted in the
 sample chamber 5.
 In each of the following illustrative examples, the same reference codes
 that are used in FIGS. 1 and 2 are used to designate identical parts.
 FIGS. 3 and 4 depict, in an illustrative example of the invention, a device
 for measuring the nitrate-phosphate content of waste water. An optical
 measuring cell 22, which transmits a signal to the control and analysis
 device 4 when a color change occurs in the fluid sample as a result of the
 measured addition of reagent through the hose assembly 14 and the solenoid
 valve 15, is arranged in the sample chamber 5.
 FIGS. 5 and 6 depict a device for measuring the nitrate content of waste
 water by means of an optical measuring device 23 which is arranged in the
 measuring buoy 2. A fiber optic transmitter 24 projects a light beam onto
 a reflector 25 in the sample chamber 5, where it is reflected and strikes
 a fiber optic receiver 26. The electric power needed to drive the optical
 device 23 and to transmit the signal to the control and analysis device 4
 is provided through electric cables 27. A compressor 28, which is
 connected to the sample chamber 5 via a solenoid valve 29, serves as a gas
 exchange apparatus for filling and emptying the sample chamber 5 and the
 settling chamber 8. Once the sample chamber 5 has been drained, a
 reference reading can be taken to compensate for the signal changes
 attributable to dirt particles on the fiber optic transmitter 24, on the
 reflector 24 and/or on the fiber optic receiver 26.
 The illustrative example of the invention depicted in FIGS. 7 and 8
 represents a device for analyzing the oxidizable carbon content (TOC
 content) of waste water. In this case, the measuring buoy 2 is also
 immersed in the waste water 1. A pH probe 30 protrudes into the sample
 chamber 5.
 To feed reaction gas (O.sub.3) into the sample chamber 5, a gas feed line
 32 lockable with a solenoid valve 31 opens into the floor of the sample
 chamber 5 underneath a frit 33. To prevent the reaction gas being fed into
 the sample chamber 5 from evacuating the sample chamber 5, a valve 34
 positioned near the chamber opening 7 is closed when reaction gas is fed
 into the sample chamber 5.
 A fill level sensor 35 protruding into the sample chamber 5 emits a signal
 when the sample chamber 5 is completely full. Acid or alkaline solutions
 can be fed into the sample chamber 5 through solenoid valves 36 and/or 37.
 Once it has reacted with the waste water sample in the sample chamber 5,
 the reaction gas passes through a solenoid valve 38 and a gas removal line
 39 and is conveyed to an analysis apparatus arranged in a control and
 analysis device positioned at a distance from the measuring buoy 2. The
 analysis of the discharged reaction gas performed there yields a reading
 for the TOC content of the waste water being analyzed.
 In FIG. 7, a settling chamber 8 is indicated by dash-dot lines in the lower
 portion of the measuring buoy 2. This is meant to suggest that this type
 of settling chamber 8 can be eliminated. It may be necessary, particularly
 during TOC analysis, to eliminate the settling of solid matter components
 in the waste water under analysis if these solid matter components must
 also be considered when measuring the TOC content.
 The device depicted in FIG. 9 is used to determine the biological oxygen
 requirement (BSB) of waste water. The device is designed as a measuring
 buoy 2 immersible in the waste water. A drivable rotor 40 arranged in the
 sample chamber 5 is propelled to rotate around the vertical axis 42 by a
 motor 41. The outer surface 43 of the rotor 40 forms a biological growth
 surface. There is only a small gap 44, which forms the reaction chamber,
 between the outer surface 43 of the rotor 40 and the wall 5a of the sample
 chamber 5.
 The sample chamber 5 is in direct contact with the surrounding fluid via
 the chamber opening 9 in the floor. The sample chamber 5 is surrounded by
 an aeration chamber 45, which serves to ventilate and temper the dilution
 water being used. To this end, an aerator 46, which is connected to an air
 supply valve 47, and a heater 48 project into the aeration chamber 45. The
 aeration chamber 45 opens into the sample chamber 5 through an overflow
 opening 49. Dilution water is fed into the aeration chamber 45 through a
 line 51 and a supply device 50, which may be featured as either a pump or
 a valve.
 Once a test has been completed, the tempered dilution water is aerated in
 the aeration chamber 45. As this occurs, the air is discharged from the
 measuring buoy 2 through the overflow opening 49, the upper portion of the
 sample chamber 5, and through an air discharge valve 52.
 Following sufficient aeration, the air supply valve 47 is closed and the
 valve 50 for the water supply is opened. As soon as a sufficient fill
 level is registered by a contact maker, the air discharge valve 52 is
 closed.
 The tempered and aerated dilution water now displaces the waste water
 mixture from the preceding test in the sample chamber 5, and it is
 discharged through the chamber opening 9. A new test begins as soon as the
 waste water mixture in the sample chamber 5 has been replaced with
 dilution water. Waste water is then sucked into the sample chamber 5 by a
 dosing pump 53. An oxygen probe 54 is used to determine the oxygen
 consumption per unit of time and, consequently, the BSB.
 The use of the rotor 40 as the carrier of the biological growth surface
 ensures that this growth surface comes into homogeneous contact with all
 of the sample in the sample chamber 5. The fact that the volume of the
 sample chamber 5 is very small may be considered particularly advantageous
 in this regard.
 The device for determining the BSB depicted in FIG. 10 differs primarily
 from the device described above in that it operates without dilution
 water. In this case, a rotor 40 drivable by the motor 41 is also arranged
 in the sample chamber 5. Its outer surface 43 forms the biological growth
 surface. The chamber opening 9 in the floor of the sample chamber 5 opens
 into an aeration chamber 45, which surrounds both the floor and the
 perimeter of the sample chamber 5. This aeration chamber 55 has an opening
 56 for the waste water in its floor. The rotor 40 is connected to an
 aerator 57 which protrudes into the aeration chamber 45. A line connected
 to an air supply valve 58 feeds into the sample chamber 5. The remaining
 parts are identified by the same reference numbers used to designate
 identical parts in FIG. 9.
 The sample chamber 5, which forms the reaction chamber, and the aeration
 chamber 45 are evacuated by air flowing in through the valve 58. Then the
 hydrostatic pressure of the surrounding waste water forces waste water
 through the opening 56 and into the aeration chamber 45, where it is
 aerated and tempered. The aerated waste water is then pressed into the
 sample chamber 5 through the chamber opening 9. The oxygen probe 54
 measures oxygen consumption per unit of time and converts this value into
 the biological oxygen requirement (BSB).
 FIG. 11 depicts a device for determining the chemical oxygen requirement
 (CSB) featured as an immersible measuring buoy. An air or ozone supply
 line which is lockable by means of a valve 58 opens into the sample
 chamber 5. Reagents can be supplied through a reagent valve 59. A pH probe
 60 protrudes into the sample chamber 5. Air or ozone can be evacuated from
 the sample chamber 5 through a discharge valve 61. An ozone measuring
 probe 62 is used to determine the ozone content. The chamber opening 9 of
 the sample chamber 5 is lockable by means of a valve 63.
 The sample chamber 5 is filled when the intake valve 58 and the discharge
 valve 61 are open. The pH level is set to a preset value ranging from 3 to
 5.
 The waste water in the sample chamber 5 is gassed with ozone. After a
 sufficient amount of gassing has taken place, the ozone generator (not
 depicted) is switched off. Once the intake valve 58, which is featured as
 a three-way valve, has been switched, preset amounts of air or oxygen only
 are forced through the valve and against the surface of the water. When
 valve 63 is open, the ozone consumption per unit of time measured at the
 chamber opening 9 represents a measure for the CSB. Testing is repeated
 once the chamber has been emptied.