GB2312278A - Organic and/or biological pollution monitor - Google Patents

Organic and/or biological pollution monitor Download PDF

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Publication number
GB2312278A
GB2312278A GB9608194A GB9608194A GB2312278A GB 2312278 A GB2312278 A GB 2312278A GB 9608194 A GB9608194 A GB 9608194A GB 9608194 A GB9608194 A GB 9608194A GB 2312278 A GB2312278 A GB 2312278A
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liquid
steps
liquid sample
wavelengths
sample
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GB2312278B (en
GB9608194D0 (en
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Boghos Awanes Manook
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/18—Water
    • G01N33/1826—Water organic contamination in water
    • G01N33/1846—Total carbon analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/33—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using ultraviolet light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
    • G01N21/53—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke
    • G01N21/532—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke with measurement of scattering and transmission
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/85—Investigating moving fluids or granular solids
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/18—Water
    • G01N33/1806—Water biological or chemical oxygen demand (BOD or COD)
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/18—Water
    • G01N33/186—Water using one or more living organisms, e.g. a fish
    • G01N33/1866—Water using one or more living organisms, e.g. a fish using microorganisms
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/15—Preventing contamination of the components of the optical system or obstruction of the light path
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/18—Water
    • G01N33/1893—Water using flow cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/20—Controlling water pollution; Waste water treatment

Abstract

In order to monitor pollution, the concentration of organic and/or biological matter present in a liquid sample is determined from measurements of UV and visible light absorption and scatter at a number of wavelengths (including 254nm) and measurements of dissolved oxygen performed on both sample and reference liquids. Light from a UV tube 21 passes through three windows 24/34 into separate sample and reference flow-cells 14, 16 or a single flow-cell 14. Direct light passes out to detectors 28/38 through three wavelength filters 26/36, and scattered light to detectors 32/42 through filters 30/40. A microprocessor (49) calculates COD, TOC and BOD after compensation using the dissolved oxygen measurements and, optionally, ambient and liquid temperature measurements. Sprays 57, 58, 59 may clean the flow-cell 14. The whole apparatus including pumps and valves for the liquids may be in a single housing.

Description

Organic and/or Biological Pollution Monitoring of Liquids Based on UViVisible Light Absorption/Scatter and Dissolved Oxygen Measurements This invention relates to an Organic and/or Biological Pollution Monitoring System based on combinations of ultra-violet (UV) absorbance and scattering principles along with the measurement of the dissolved oxygen (DO) to determine the organic and/or biological matters present in a liquid. It is of particular application for on-line/in-line monitoring of water quality at locations, such as, for example, industrial or water/waste treatment plants, rivers and reservoirs.
A number of instruments are available in the market place for determining the organic or biological pollution in water, involving the measurement of parameters such as BOD (biochemical oxygen demand), TOC (total organic carbon) or COD (chemical oxygen demand). The parameter that is traditionally of most interest is the BODs (5 represents days of sample incubation). There is a need for an on-line/in-line monitoring system whose measurements can be inferred to the instantaneous BOD measurement of the liquid sample. A number of on-line, continuous BOD, TOC and COD monitors have been developed, based on a variety of techniques, and are available in the market place. Some are prohibitively expensive while others, although cheaper, require considerable maintenance and servicing.
The existing UV-absorbance based monitors are based on the principle that a particular substance (organic) will absorb light of a particular wavelength (or wavelengths), so that the reduction in the intensity of light of that wavelength, when transmitted through a sample containing that substance, can be related to the concentration of that substance. Some organic compounds (e.g. Aromatics), that have conjugated double bonds, absorb light in the .Uv wavelength region and research has shown that absorbance measurement taken in that region, and in particular at 254nm, can be related to COD, TOC and BOD parameters. While the respirometeric type instruments determine the biological pollution, they however may not be capable of identifying the organic (chemical) based pollution.
The performance of the present UV-absorbance based monitors has, however, been in many cases disappointing in that the absorption readings (usually at 254nm) have been shown to be unreliable as an indication of organic pollution due to the dependence on other, unknown factors. Attempts, in the past have been made to compensate for turbidity in liquid samples and recently other compensating features (for example conductivity, pH and colour) were added.
The present invention attempts to overcome the above mentioned problems associated with the prior art, to provide an inexpensive, accurate and reliable monitor that can be readily used in a variety of applications.
The present invention provides a method of determining the amount of organic and/or biological matters present in a liquid sample and comprises the following steps (a) Using one (or more) Uv light source (either low pressure mercury or laser based), either pulsed or continuous, to obtain a number of wavelengths both in the UV and visible regions.
(b) Passing the selected UV and/or visible lights, at a number of wavelengths and angles, through the liquid and defined reference samples.
(c) Passing lights at a number of wavelengths (for example 220 nm, 254nm, and 285nm wavelengths) in the UV region, through a reference sample or alternatively directly (through air), and sensing the emergent lights, at each particular wavelength and angle; (d) Passing lights at a number of wavelengths (for example 220 nm, 254nm, and 285nm wavelengths) in the UV region, through the liquid sample, and sensing the emergent lights, at each particular wavelength and angle; (e) Passing lights at a number of wavelengths (for example 220 nm, 254nm, and 285nm wavelengths) in the UV region, through the reference sample or alternatively directly (through air), and sensing the scattered lights, at each particular wavelength and angle; (f) Passing lights at a number of wavelengths (for example 220 nm, 254nm, and 285nm wavelengths) in the UV region, through the liquid sample, and sensing the scattered lights, at each particular wavelength and angle; (g) Passing lights, using the UV source used in ( a), at a number of wavelengths (for example 470nm, 565nm, wavelengths) in the visible region (of the UV source), through a reference sample or alternatively directly (through air), and sensing the emergent lights, at each particular wavelength and angle; (h) Passing lights, using the source used in( a), at a number of wavelengths (for example 470nm, 565nm, wavelengths) in the visible region (of the UV source), through the liquid sample, and sensing the emergent lights, at each particular wavelength and angle; (i) Passing lights, using the UV source used in ( a), at a number of wavelengths (for example 470nm, 565nm, wavelengths) in the visible region (of the UV source), through a reference sample, and sensing the scattered lights, at each particular wavelength and angle; (j) Passing lights, using the source used in ( a), at a number of wavelengths (for example 470nm, 565nm, wavelengths) in the visible region (of the UV source),through a liquid sample, and sensing the scattered lights, at each particular wavelength and angle; (k) The measurement of dissolved oxygen (DO) of the reference sample (if necessary) for comparison purposes.
(1) The measurement of dissolved oxygen (DO) of the liquid sample to determine the biological activities within the sample.
(m) The measurement of the temperatures of the liquid and reference samples along with the ambient temperatures to compensate for the UV light source, all the photodiodes and DO sensors.
(n) Determining the amount of organic and/or biological matters in the liquid sample from the measured emergent lights (c and g) of the reference sample, measured reduction in the emergent lights (d and h), and the measured scattered lights (e, f, i and j) of the liquid and reference at each particular wavelength by a calculation of the combination of the absorbance and scattered lights (both in the UV and visible regions) in which the results from steps (b) to (h) and (i) to (j) are used to enhance the measurement, establish the biological activities and provide long term stability.
(o) Determining the amount of organic and/or biological matters in the sample from the measured dissolved oxygen (DO) (I and m), which are used to enhance the BOD measurement, establish the biological activities and provide long term stability.
(p) Determining the amount of suspended solids present in the liquid sample from the measured reduction in the emergent lights (g) and the measured scattered lights (h) at each particular wavelength by a calculation, of the combination of the absorbed and scattered lights in which the results are used for compensation purposes to enhance the measurement as described in steps (n) to (o).
It has been discovered that some of the fine particulate matter, present in the liquid sample, can be attributed to organic (and/or biological) matter and specifically at low concentrations of the organic substance. The measurements in steps (c) and (e) of the emergent and scattered UV lights, (directly through air or through a reference sample), at a particular wavelength can, therefore, enhance the determination of the organic and/or biological matter considerably.
It has also been discovered that some of the organic and/or biological matters, present in the sample, may respond also at wavelengths (such as 220nm or 285nm) in the UV region, alongside the 254nm. The measurements in steps (c) and (d) of the emergent, and scattered (e) and (f) UV lights at wavelengths, for example 220nm and 285nm (beside 254nm) can be advantageous, in some applications, to enhance considerably the measurement in steps (d) and (e) of the UV lights to determine the organic and/or biological matter, present in the liquid sample.
The measurement in steps (c) and (e) of the UV lights, of the reference sample, are used to compensate and enhance the measurement of the emergent (d) and scattered (f) uV lights through the liquid sample. The emergent (c) and scattered (e) uV lights of the reference, at the selected wavelengths, can be measured through air (directly) or through a suitable sample such as clean water (depending on the applications).
The measurement of the emergent visible lights (obtained from the UV source) as in steps (g) and (i) of the reference sample and scattered visible lights (obtained from the uV source) as in steps (h and j), at the selected wavelengths (for example 565nm), can be used to determine the amount of non-organic suspended solids concentration and/or turbidity present in the liquid sample The measurement of the suspended solids concentration and/or turbidity may be used to enhance and compensate for the effect of non-organic particulates, present in the liquid sample, on the organic and/or the biological matter of interest.
The measurement ofthe emergent visible lights (obtained from the UV source) as in steps (g and i) of the reference sample and scattered visible lights (obtained from the UV source) as in steps (h and j), at the selected wavelengths (for example 470nm), can be used to determine the amount of colour present in the liquid sample The measurement of the colour may be used to enhance and compensate for the organic and/or biological matters of interest, present in the liquid sample.
It has been also been discovered that excessive presence of organic and/or biological matters, in the liquid sample, can affect the dissolved oxygen (DO) level. The measurement therefore of the DO, in the liquid and reference samples, can be relevant to check, compensate and if possible establish the broad nature of the organic and/or biological matters present in the liquid sample. The differential in the DO levels, between the liquid sample and the reference sample, will be used in an algorithm, either separately, to establish the nature of the BOD, or as a means of compensation for the organic/biological matters present in the liquid sample. The DO measurements will also be used, in applications where the liquid sample is biologically active, to determine the BOD concentration.
The present invention also provides apparatus suitable for use in all or part of the method described above. The apparatus comprises firstly a means of passing WfVisible lights, at different wavelengths, through the liquid and reference samples and measuring the emergent WfVisible lights from both liquid and reference samples, secondly a means for making measurement of the scattered WfVisible lights of both liquid and reference samples, thirdly a means of making measurement ofthe dissolved oxygen (DO) in both the liquid and reference samples, and fourthly a means of cleaning all optical windows and sensors. The said apparatus includes a processing means for use in steps (n) and (p) for carrying out the calculation to determine the amount of organic and/or biological matters present in the liquid sample.
The apparatus may be provided in a stand-alone housing and/or in a portable form. The first, second, third and fourth means may be provided in a single measuring cell, so as to minimise errors caused by the fluctuations (for example in temperature), or separate in individual flow-cells.
The present invention also provides a means of cleaning the surfaces of the optical windows and the sensors, which are in contact with the liquid sample, by projecting ajet of any suitable mixture of liquid and/or air (either cold, hot or steam), at suitable intervals controlled by the processing means.
The invention also provides a monitoring system for use in a method for determining the amount of organic and/or biological matters in a liquid source, which system comprises monitoring apparatus as described earlier, in combination with the above described cleaning apparatus.
One form of organic and/or biological pollutant monitor of a liquid source, and one type of cleaning apparatus, constructed in accordance with the invention, will now be described, by way of example only, with reference to accompanying drawings, in which: Figure (lea) is a partially cut-away schematic view of the monitor where the various lights are measured through the liquid sample and reference sample using two seperate flow-cells Figure (1 b) is a partially cut-away schematic view of the monitor where the various lights are measured through the liquid and reference samples using a single flow-cell; Figure (2a) is a schematic sectional view of the measuring flow-cell monitoring and the cleaning system; to a larger scale than that of Figure (la); Figure (2b) is a schematic sectional view of the measuring flow-cell monitoring and the cleaning system; to a larger scale than that of Figure (lob); Figure (3a) is a partially cut-away schematic view of the monitoring system where the various lights and sensors are measured through the liquid sample and a reference sample; to a larger scale than that given in of Figure (2a); Figure (3b) is a partially cut-away schematic view of the monitoring system where the various lights and sensors are measured through the liquid sample and a reference sample; to a larger scale than that given in of Figure (2b); Figure (3c) is a partially cut-away schematic side-view of the measuring flow-cell monitoring and cleaning system where various lights are measured through the liquid sample and a reference sample of Figure (3a) for a given Lw wavelength; Figure (3d) is a partially cut-away schematic side-view of the measuring flow-cell monitoring and cleaning system where the DO and temperature sensors are measuring through the liquid sample and reference samples of Figure (3a); Figure (4) is a partially cut-away schematic view of the jet set mechanics for each individual optical windows and sensor.
The organic and/or biological pollution monitoring system, with the individual optical window and sensor cleaning, is capable of being used for on-line/in-line, continuous monitoring of liquid quality in a variety of on-site locations, such as, for example rivers, reservoirs or industrial effluent outlets.
The monitoring system (1) comprises a single, weatherproof, portable unit separated into three compartments (2), (3), (4) containing a cleaning fluid pump (11) and reference sample pump (15), a measuring liquid sample flow-cell (14) and reference sample flow-cell (16) with various optical windows, lenses, interference filters, photodiodes, sensors and their individual cleaning units, and a microprocessor based electronics, respectively. The liquid source inlet (5) is connected to the liquid sample flow-cell (14) in the central compartment (3). A multi-way valve (13, 7) is provided for the purposes of draining (8) and liquid sample dilution. During the operation, the liquid sample is continuously discharged via the outlet (18). The reference sample can (continuously or intermittently) flow through the flow-cell (16) via the inlet (6) and the multiway solenoid valve (17) and then is discharged via the outlet (19) or drained via (9).
In the main compartment (3), the liquid sample and reference sample flow-cells (14, 16) are surrounded by an array of light sources and sensors. A tubular, for example a Pen-Ray type, UV light source comprising a low pressure mercury (or laser based) lamp (21), which can be either in a pulsed or continuous mode of operation, is suitably inserted in screen tube (22) and arranged so that three (or more) apertures are made available to produce narrow beams of light.
Both the UV light source (21) and the screen tube (22) are suitably fixed along the length of the liquid sample flow-cell (14) and the reference sample flow-cell (16). The light intensity ofthe Lw source (21) is controlled, via the box (20), so as not to cause excessive heat, ozonation, or liquid sample sterilisation since this could alter the results of the COD, TOC or the BOD measurement.
Three quartz (ore fused silica) lenses (23A, 23B, 23C), which collimate the three light beams, are positioned between the quartz (or filmed silica) optical windows (24A, 24B, 24C) and the screen tube (22). The three (or more) collimated emergent Lw light sources pass through the liquid sample, in the flow cell (14), via quartz (or fused Silica) optical windows (24A, 24B, 24C, 25A, 25B, 25C) positioned on both side ofthe flow cell (14). The three (or more) optical band-pass interference filters (26A, 26B, 26C), suitably positioned on the other side of the liquid sample flow-cell (14), are used to separate the wavelengths of interest, of emergent collimated light sources. The three (or more) receiving quartz (or fused silica) lenses (27A, 27B, 27C) will focus the above selected emergent wavelengths onto sensitive silicon photodiodes (28A, 28B, 28C).
The scattered lights caused by the particles present the liquid sample, emerging via the three (or more) quartz (or fused Silica) optical windows (29A, 29B, 29C) positioned at an angle (for example at 900) on the top side of the liquid sample flow-cell (14), pass through the three (or more) optical band-pass interference filters (30A, 30B, 30C), suitably positioned above the mentioned optical windows (29A, 29B, 29C) to separate the wavelengths of interest. The three (or more) receiving quartz (or fused silica) lenses (31A, 31B, 31C) will focus the above emergent wavelengths onto the three (or more) sensitive silicon photodiodes (32A, 32B, 32C).
A further three (or more) suitable apertures, are provided on the other side of the screen tube (22) of the tubular Lw light source (21), to produce three (or more) collimated emergent Lw light sources, via quartz (or fused Silica) lenses (33A, 33B, 33C), pass through the reference sample flow-cell (16), via quartz (or fused Silica) optical windows (34A, 34B, 34C), (35A, 35B, 35C) positioned on both side of the reference sample flow cell (16). The three (or more) optical band-pass interference filters (36A, 36B, 36C), suitably positioned on the other side of the reference sample flow-cell (16), are used to separate the wavelengths of interest, of emergent collimated light sources. The three (or more) receiving quartz (or fused silica) lenses (37A, 37B, 37C) will focus the above selected emergent wavelengths onto sensitive silicon photodiodes (3spa, 38B, 38C).
The scattered lights caused by the particles may be present in the reference sample, emerging via the three (or more) quartz (or fused Silica) optical windows (39A, 39B, 39C) positioned at an angle (for example at 90 ) on the top side of the reference sample flow-cell (16), pass the three (or more) optical band-pass interference filters (40A, 40B, 40C), suitably positioned above the mentioned optical windows (39A, 39B, 39C) to separate the wavelengths of interest. The three (or more) receiving quartz (or fused silica) lenses (41A, 41B, 41C) will focus the above emergent wavelengths onto the three (or more) sensitive silicon photodiodes (42A, 42B, 42C).
The three (or more) optical band-pass interference filters (26A) match (31 A; 3 6A, 41 A) and (26B) match (31B, 36B, 41B) and (26C) match (31C, 36C, 41C).
Alternative arrangements (Figures ib and 2b) can also be made by allowing both the liquid sample flow-cell (14) and reference sample flow-cell (16) to flow sequentially through one flow-cell (14), to reduce costs. The reference and the liquid samples are pumped into the flow cell (14), via the multi-way valve (7). This arrangement will eliminate the need for the reference flow-cell (16) and its associated components.
The temperature probes (43, 45) and DO sensors (44, 46), suitably positioned inside the liquid sample flow-cell (14) and the reference sample flow-cell (16), will measure the temperature and dissolved oxygen level respectively of both samples. These probes (43,45) and (44, 46) are used in the calculation algorithm for the organic and/or biological matter concentration in the liquid sample. The ambient temperature probe (47) is located inside the compartment (3).
It has been discovered that biological (or otherwise) fouling of the optical windows (and sensors) is very common in most applications. Each individual set of optical windows (and sensors), in contact with the liquid sample, need, therefore, to be cleaned to ensure that the organic pollution measurement, over a long period of time, is unaffected by the fouling process.
The sensors are cleaned by projecting a suitable fluid jet on the optical windows (57, 58, 59), and the sensors (60, 61) which are in contact with the liquid sample. The cleaning fluid inlet (10) is connected to the pump (11), via tubing. The solenoid valve (12) will allow the cleaning process, of all the optical windows and sensors, to proceed. The cleaning of the optical windows (and sensors) can be carried out simultaneously via the main solenoid valve (12) only.
The optical window (and sensors) cleaning sequence is controlled by the microprocessor (49) can be programmed by the user to define the cleaning cycle time, for example on an hourly, or daily basis. During the cleaning process, the fluid is drained via the multi-way valve(13 or 7).
Each set ofjet mechanics as shown in Figure (4) comprises a body (52) with an inlet (53) and a narrow tubular opening (54) of different sizes, suitable for each application, with various end (55) geometries, such as rectangular, allowing the projection of a specific jet spray width with specific pressure exertion on the face of each individual sensor head. Each set ofjet mechanics (52) will also contain a means of non-return valve (56) to prevent the liquid source from entering the cleaning fluid. The inlet ports of the jet sets (57, 58, 59, 60, 61) are linked to a solenoid valve (12) via a flexible tube.
Both the liquid (43, 45) and ambient (47) temperature probes are used for compensation purposes of the photodiode sets (28, 32, 38, 42) and the dissolved oxygen sensors (44, 46), by the microprocessor (49) as well as to be shown on the display (50).
The microprocessor (49) analyses the data received from the photodiodes, temperature and dissolved oxygen sensors in order to determine the COD and/or TOC and/or BOD concentration, suspended solids concentration and/or turbidity. Each of the parameters can be displayed by operation ofthe keypad (51), situated in the compartment (4).
The microprocessor (49) will carry out all the control and measurement required and calculate each individual parameter mentioned above, using suitable algorithms, which are expanded below :a) Operate the appropriate pump (15), multi-way valves (13 or 7) and (17) to allow both the liquid and reference samples to flow through via either both flow-cells (14, 16) or a single flow-cell (14) during the measurement period.
b) control the operation of the UV light source (21) either on a continuous or pulsed basis via the box (20).
c) Carry out the appropriate data acquisition of each photodiode (28, 32, 38, 42), temperature probes (43,45, 47) and dissolved oxygen probes (44, 46) when using either both flow-cells (14, 16) or a single flow-cell (14).
d) Appropriate liquid temperature compensation is implemented by the microprocessor (49) on the DO measurement carried out by the probes (44, 46), when using either both flow-cells (14, 16) or a single flow-cell (14).
e) Appropriate liquid and ambient temperature (43, 45, 47) and DO (44, 48) compensation is implemented, when using either both flow-cells (14, 16) or a single flow-cell (14), on the algorithm resident in the microprocessor (49) to measure the BOD concentration in the liquid sample.
g) The temperature compensated DO (44, 46) measurements,when using either both flow cells (14, 16) or a single flow-cell (14), both in the liquid and reference samples, are used in the algorithm resident in the microprocessor (49) to measure the BOD concentration in the liquid sample.
h) The emergent and scattered UV lights, when using either both flow-cells (14, 16) or a single flow-cell (14), are used by the microprocessor (49) to calculate the organic and/or biological matter. The photodiodes, (28, 32, 38 and 42), are temperature compensated.
i) The turbidity measurement, when using either both flow-cells (14, 16) or a single flow cell (14), is calculated by the microprocessor (49) using visible lights of the Lw source.
The photodiodes, (24, 28, 33, 38), are temperature compensated.
The microprocessor (49) implements suitable checking procedures algorithm on each individual sensor mentioned above, using either both flow-cells (14, 16) or a single flow-cell (14), and thus control the cleaning system (57, 58, 59, 60, 61) using the following steps which are expanded below :a) Empty the liquid flow-cell (14) by draining (8) the liquid sample via the multi-way valve (13 or 7) and then check if the flow-cell (14) is empty.
b) After step (a) is completed, fill the liquid flow-cell (14) with a suitable fluid, such as distilled or clean tap water and check, either individually or collectively, the condition of all the optical windows and sensor heads and raise cleaning flags to execute the cleaning procedures accordingly.
c) Empty the liquid sample flow-cell (14) by draining the liquid (8), mentioned in (b) above, via the multi-way valve (13 or 7) and then check if the flow-cell (14) is emptied.
d) Fill the liquid sample flow-cell (14) with the appropriate standard solution to calibrate the appropriate sensor head concerned. Empty the liquid sample flow-cell (14) by draining (8) the above mentioned solution via the multi-way valve (13 or 7).
e) After steps (b and c) are completed, the microprocessor (49) determines that the optical windows and probes (24, 25, 29, 443, 44 45, 46) require cleaning, jet streams are projected (such as cold/hot water, suitable detergents, alcohol, or biocide in diluted forms or otherwise) on the face of the active part of the optical windows and probes, by opening the solenoid valve (12). During the cleaning action, the fluid is continuously drained via the multi-way valve (13 or 7) through the outlet (8). The above action is repeated until the cleaning algorithm, resident in the microprocessor (49), is completed fully and satisfactorily. After the cleaning process is completed apply step (d) if necessary for calibration purposes.
The cleaning and/or calibration procedures mentioned above (from c to k) can be implemented collectively by cleaning all the probes simultaneously. The cleaning cycle as well as period can be programmed to suit the user requirements. During the cleaning process, zero calibration of each sensor can be established and stored for future data calculations of various parameters.
Other sensors, such as a flowmeter, can be added to suit some applications to determine the gross pullution. Level switches can also be incorporated in the flow-cells (14, 16) to check that the flow-cells are empty or full.

Claims (20)

1. A method for determining the various primary measurement parameters such as COD, TOC and BOD in a liquid source, along with Suspended Solids concentration, Turbidity, Temperature and Dissolved Oxygen (DO), comprising the following steps : (a) Passing the selected Visible lights, at a number of wavelengths, through the liquid sample and sensing the emergent Visible light at different wavelengths; and, (b) Passing the selected Visible lights, at a number of wavelengths, through a defined reference sample and sensing the emergent Visible light at different wavelengths; and, (c) Passing the selected Visible lights, at a number of wavelengths, through the liquid sample and sensing the scattered Visible light at different wavelengths; and, (d) Making a measurement to provide indication of the Dissolved Oxygen (DO) of the liquid and reference samples.
(e) Determining the amount of organic/biological matters in the liquid sample from the measured absorption/scatter in the Visible lights by a calculation in which the results from steps (a) to (d) are used for compensation (or otherwise) purposes.
2. A method as claimed in claim 1, wherein Visible lights of (254nm and/or 220nm and/or 285nm) and (470nm or 565nm) wavelengths are used in steps (a) to (c).
3 A method as claimed in claims 1 to 2, wherein steps (a) and (b) comprises of passing Visible lights, at a number of wavelengths, through the liquid source and defined reference samples and measuring the amount of emergent Visible lights as in steps (a) and (b).
4. A method as claimed in claims 1 to 3, wherein step (c) comprises of passing UV/visible lights, at a number of wavelengths, through the liquid sample and measuring the amount of scattered UV/visible lights as in steps (c).
5. A method as claimed in claim 1 or 4, wherein the measurement of the dissolved oxygen (DO) concentration in both the liquid and reference samples is carried out.
6. A method as claimed in claim 1 or 5, wherein steps in any one of claims 1 wherein steps (a) to (f) are carried out under the same conditions.
7. A method claimed in any of claims 1 to 6 including additional steps of measuring one or more variable(s).
8. A method claimed in any of claims 7 wherein the additional variables are measured for compensation purposes.
9. A method claimed in any of claims 6, 8 wherein the additional steps are carried out on the liquid (and/or reference) sample under the same conditions as in steps (a) to (f).
10. A method claimed in any one claims of 7 to 9, wherein additional variables are the temperature of the liquid and reference samples.
11. A method as claimed in any one of claims of 7 to 9, wherein an additional variable is the ambient temperature.
12. A method as claimed in any one of claims of 7 to 11, wherein the BOD of the liquid sample is determined.
13. A method as claimed in any one of claims of 7 to 11, wherein the organic matter concentration (such as COD and/or TOC) in a liquid sample is determined, substantially as herein before described, with reference to the accompanying drawings.
14. Apparatus for determining the amount of organic and/or biological matter in a liquid sample, the apparatus comprising firstly a means of passing W/Visible lights, at different wavelengths, through the liquid and reference samples and measuring the emergent W/Visible lights from both liquid and reference samples, secondly a means for making measurement of the scattered W/Visible lights of both liquid and reference samples, thirdly a means of making measurement of the dissolved oxygen (DO) in both the liquid and reference samples, fourthly a means for cleaning and checking all optical windows and sensors.
15. Apparatus as claimed in claim (14), including processing means for determining the amount of organic and/or biological matters in the liquid sample from an output from the first, second and third means.
16. Apparatus as claimed in claim (14) or claim (15), wherein the apparatus can be constructed either by only the first means, or by the second means, or by the third means, or can be constructed by all four means.
17. Apparatus as claimed in claims (14) to claim (16), wherein the apparatus can be constructed in a single housing and/or portable.
18. Apparatus as claimed in any one of claims (14) to (17), wherein the first, second, third and fourth means are provided in one or two measuring flow-cells.
19. Apparatus as claimed in any one of claims (14) to (18), including means of measuring one or more additional variables as specified in any one claims (7) to (11).
20. Apparatus as claimed in any one of claims 13 to 19, wherein the processing means is adapted to calculate the BOD of the liquid sample.
20. Apparatus as claimed in claim (14) and (19), wherein the processing means uses the measured additional variables for compensations purposes.
21. Apparatus as claimed in any one of claims (14) to (20), wherein the processing means is adapted to calculate the BOD of the liquid sample.
Amendments to the claims have been filed as follows 1. A method for determining the various primary measurement parameters such as COD, TOC and BOD in a liquid sample, comprising the following steps : (a) Passing UV or visible light, at a number of selcted wavelengths, through the liquid sample and sensing the emergent light at different wavelengths; (b) Passing the selected wavelengths of light through a defined reference sample and sensing the emergent light at different wavelengths, (c) Passing the selected wavelengths of light through the liquid sample and sensing the scattered light at different wavelengths; (d) Making a measurement to provide an indication of the Dissolved Oxygen (DO) of the liquid and reference samples; and (e) Determining the amount of organic or biological matter in the liquid sample from the measured absorption and scatter of the light by a calculation in which the results from steps (a) to (d) are used.
2. A method as claimed in claim 1, wherein light of (254nm and/or 220nm and/or 285nm) and (470nm or 565nm) wavelengths are used in steps (a) to (c).
3 A method as claimed in any one of Claims 1 and 2, wherein steps (a) and (b) further comprise the step of measuring the amount of emergent light.
4. A method as claimed in any one of claims 1 to 3, wherein step (c) further comprises the step of measuring the amount of scattered light.
5. A method as claimed in claim 1, wherein steps (a) to (d) are carried out under the same conditions.
6. A method claimed in any of claims 1 to 5 including additional steps of measuring one or more additional variable(s).
7. A method claimed in claim 6 wherein the additional variables are measured for compensation purposes.
8. A method claimed in any one of claims 6 and 7 wherein the additional steps are carried out on the liquid (and/or reference) sample under the same conditions as in steps (a) to (d).
9. A method claimed in any one of claims 6 to 8, wherein the additional variables are the temperature of the liquid and reference samples.
10. A method as claimed in any one of claims of 6 to 8, wherein the additional variable is the ambient temperature.
11. A A method as claimed in any one of claims of 6 to 10, wherein the BOD of the liquid sample is determined.
12. A method as claimed in any one of claims of 6 to 10, wherein the organic matter concentration in a liquid sample is determined, substantially as herein before described, with reference to the accompanying drawings.
13. Apparatus for determining the amount of organic and/or biological matter in a liquid sample, the apparatus comprising firstly a means of passing Lw or Visible light, at different wavelengths, through the liquid and reference samples and measuring the emergent light from both liquid and reference samples, secondly a means for making measurement of the scattered light of both liquid and reference samples, thirdly a means of making measurement of the dissolved oxygen (DO) in both the liquid and reference samples, fourthly a means for cleaning and checking all optical windows and sensors.
14. Apparatus as claimed in claim (13), including processing means for determining the amount of organic and/or biological matters in the liquid sample from an output from the first, second and third means.
15. Apparatus as claimed in any one of claims 13 and 14, wherein the apparatus is constructed in a single housing.
16. Apparatus as claimed in any one of Claims 13 to 15, wherein the apparatus is portable.
17. Apparatus as claimed in any one of claims 13 to 16, wherein the first, second, third and fourth means are provided in one or two measuring flow-cells.
18. Apparatus as claimed in any one of claims 13 to 17, including means for measuring one or more additional variables as specified in any one of claims 9 and 10 19. Apparatus as claimed in claim 18, wherein the processing means uses the measured additional variables for compensations purposes.
GB9608194A 1996-04-19 1996-04-19 Organic and/or biological pollution monitoring of liquids based on UV/visible light absorbtion/scatter and dissolved oxygen measurements Expired - Fee Related GB2312278B (en)

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GB2553218A (en) * 2016-08-25 2018-02-28 Rs Hydro Ltd Water quality sensing
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GB9608194D0 (en) 1996-06-26

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