METHOD FOR DETERMINING SUSPENDED MATTER LOADS CONCENTRATIONS IN A LIQUID

Abstract

Systems, methods and kits monitor suspended matter loads concentration in a liquid. The systems, methods and kits collect environmental variables, comprising the pressure p at a depth L in said liquid and the liquid depth L at which said pressure p is collected to provide the value of the pressure p0 which is the aerial pressure. The systems, methods and kits further insert said environmental variables in an equation and calculate the suspended matter loads volumetric concentration in the liquid from the absolute pressure p measured at the depth L in the liquid.

Claims

1. A method of determining suspended matter loads volumetric concentration in a liquid, wherein said method comprises the steps of: a) measuring environmental variables comprising: the absolute pressure p at a depth L in said liquid, wherein absolute pressure p is measured by a single immersed pressure sensor disposed at the depth L in the liquid; and the liquid depth L at which said pressure p is measured by the single immersed pressure sensor wherein the liquid depth L is measured by a liquid-depth probe; b) inserting, with a data management system, said measured environmental variables in an equation, wherein the single immersed pressure sensor and the liquid-depth probe are connected to the data management system, wherein the equation is: $C_v=\frac{{}_w\left(T\right)}{{}_s-{}_w\left(T\right)}.Math.\left(\frac{p-p_0}{\mathrm{gL}.Math..Math.{}_w\left(T\right)}-C_{v.Math..Math.\mathrm{salt}}.Math.\frac{{}_{\mathrm{salt}}-{}_w\left(T\right)}{{}_w\left(T\right)}-1\right)$ $\mathrm{or}$ $C_v=\frac{{}_w\left(T\right)}{{}_s-{}_w\left(T\right)}.Math.\left(\frac{p-p_0}{\mathrm{gl}.Math..Math.{}_w\left(T\right)}-1\right)$ wherein, L is the depth at which said absolute pressure p is measured, expressed in m, p is the absolute pressure measured at a depth L in said liquid, expressed in Pa, p0 is aerial pressure, expressed in Pa, g is gravitational acceleration, expressed in m/s.sup.2, Cv is suspended matter loads volumetric concentration, expressed in m.sup.3/m.sup.3, s is density of said suspended matter loads, expressed in kg/m.sup.3, Cvsalt is dissolved salt volumetric concentration, expressed in m.sup.3/m.sup.3, w(T) is density, expressed in kg/m.sup.3, of said liquid at the temperature T, expressed in C., and salt is density of salt, expressed in kg/m.sup.3; and c) calculating, with the data management system, the suspended matter loads volumetric concentration in the liquid, via the equation from the measured absolute pressure p measured by the first pressure sensor at the measured depth L in the liquid measured by the liquid-depth probe.

2. The method according to claim 1, wherein the step of providing the value of the pressure p0 is performed by measuring the pressure above the liquid.

3. The method according to claim 1, wherein the temperature T of said liquid is collected and the density of the liquid is calculated according to the following equation: $.Math..Math.w\left(T\right)=\frac{.Math..Math.w\left(T.Math..Math.0\right)}{1+\left(T-T.Math..Math.0\right)}$ wherein, w(T) is the density, expressed in kg/m.sup.3, of said liquid at the temperature T, w(T0) is the density, expressed in kg/m.sup.3, of said liquid at known temperature T0, is the volumetric thermic expansion coefficient of the liquid, expressed in C..sup.1, T is the temperature of the liquid, expressed in C., and T0 is the temperature at which the reference density of the liquid is known, expressed in C.

4. The method according to claim 3, wherein the liquid is water and the volumetric thermic expansion coefficient is calculated according to the following equation:
=10.sup.6(62.67914+15.84576T0.11758T.sup.2) wherein, T is the temperature of the water, expressed in C.

5. The method according to claim 1, wherein suspended matter loads mass concentration, obtained from the suspended matter loads volumetric concentration, ranges from 0.25 kg/m.sup.3 to 1000 kg/m.sup.3.

6. The method according to claim 1, wherein the steps a) to c) are repeatable at intervals of time of at least 30 seconds.

7. The method according to claim 1, wherein the method is performed when the liquid is in an open channel flow, an estuary, a river, an industrial conduit, an irrigation channel, an urban conduit, a sedimentation tank, a settling basin, a tank, a reservoir, or other liquid bodies container.

8. A system for measuring suspended matter loads concentration in a liquid, the system comprising: the liquid; and an apparatus comprising: a single immersed pressure sensor disposed at a depth L in the liquid and able to measure the absolute pressure p at said depth L in the liquid, a liquid-depth probe disposed above the liquid and able to measure a liquid depth L above the single immersed pressure sensor, and a data management system connected to at least the single immersed pressure sensor and the liquid-depth probe, wherein the data management system executes software programmed to: a) collect the measured absolute pressure p and the measured liquid depth L measured by the first pressure sensor and the liquid-depth probe, and optionally a temperature sensor and an additional pressure sensor disposed above the liquid, b) insert the measured absolute pressure p and the measured liquid depth L in an equation, wherein the software comprises the equation and the equation is: $C_v=\frac{{}_w\left(T\right)}{{}_s-{}_w\left(T\right)}.Math.\left(\frac{p-p_0}{\mathrm{gL}.Math..Math.{}_w\left(T\right)}-C_{v.Math..Math.\mathrm{salt}}.Math.\frac{{}_{\mathrm{salt}}-{}_w\left(T\right)}{{}_w\left(T\right)}-1\right)$ $\mathrm{or}$ $C_v=\frac{{}_w\left(T\right)}{{}_s-{}_w\left(T\right)}.Math.\left(\frac{p-p_0}{\mathrm{gl}.Math..Math.{}_w\left(T\right)}-1\right)$ wherein, L is the depth at which said absolute pressure p is measured, expressed in m, p is the absolute pressure at a depth L in said liquid, expressed in Pa, g is gravitational acceleration, expressed in m/s.sup.2, Cv is suspended matter loads volumetric concentration, expressed in m.sup.3/m.sup.3, s is density of said suspended matter loads, expressed in kg/m.sup.3, Cvsalt is dissolved salt volumetric concentration, expressed in m.sup.3/m.sup.3, w(T) is density, expressed in kg/m.sup.3, of said liquid at the temperature T, expressed in C., and salt is density of salt, expressed in kg/m.sup.3; and c) calculate, via the equation, and display said suspended matter loads concentration from the measured absolute pressure p measured by the first pressure sensor at the measured depth L in the liquid measured by the liquid-depth probe.

9. A kit of parts for the measurement of suspended matter loads volumetric concentration in a liquid comprising: a single immersed pressure sensor able to be disposed at a depth L in the liquid and able to measure the absolute pressure p at said depth L in the liquid, a liquid-depth probe able to measure a liquid depth L above the single immersed pressure sensor, optionally an additional pressure sensor able to measure the pressure p0 above said liquid, and software able to perform the method according to claim 1.

10. The kit of part according to claim 9, further comprising a temperature sensor configured to measure a temperature T in a liquid.

11. The kit of parts according to claim 9, further comprising a data management system.

12. The kit of parts according to claim 11, wherein the data management system comprises a processor, and a memory encoding one or more programs coupled to the processor.

13. The kit of parts according to claim 11, wherein said data management system is configured to execute the software in order to: a) collect the measurements of the single immersed pressure sensor, the liquid-depth probe, and optionally, an additional pressure sensor and/or a temperature sensor, b) insert said collected measurements in equations, and c) calculate, via the equation, and display the suspended matter loads concentration.

14. The kit of parts according to claim 9, wherein the liquid-depth probe is an ultrasound probe or a radar probe.

15. The method according claim 1, wherein the absolute pressure p is measured by a single measure performed by the single immersed pressure sensor and the single immersed pressure sensor is the sole pressure sensor disposed or immersed in the liquid.

16. The method according to claim 1, wherein the aerial pressure p0 is measured by an additional pressure sensor and the temperature T of the liquid is measured by a temperature sensor, wherein the additional pressure sensor and the temperature sensor are connected to the data management system.

17. The method according to claim 16, wherein the single immersed pressure sensor is a piezo-electric type pressure sensor, the liquid-depth probe is selected from the group consisting of an ultrasound probe, a radar probe and image analysis probe, and the temperature sensor is a thermometer immersed in the liquid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] FIG. 1 represents a schematic view of the system for collecting and monitoring the suspended matter loads volumetric concentration according to an embodiment of the present invention.

[0052] FIG. 2a is a graphical representation of the suspended matter loads volumetric concentration (dynamic conditions), expressed in m.sup.3/m.sup.3 over a time-period.

[0053] FIG. 2b is a graphical representation of the observed versus known suspended sediment volumetric concentration in static conditions in a tank.

[0054] FIG. 3 represents a schematic view of a drilled tube in which a pressure sensor and a temperature sensor may be set.

DETAILED DESCRIPTION OF THE INVENTION

[0055] According to a first aspect, the present invention relates to a method for determining suspended matter loads volumetric concentration in a liquid, wherein said method comprises the steps of: [0056] a) collecting environmental variables comprising: [0057] the absolute pressure p at a depth L in said liquid, [0058] the liquid depth L at which said pressure p is collected, and providing the value of the pressure p0 which is the aerial pressure, [0059] b) inserting said environmental variables in an equation, [0060] c) calculating the suspended matter loads volumetric concentration in the liquid from the absolute pressure p measured at a depth L in the liquid.

[0061] The term environmental variables as used herein refers to parameters to be measured and essential to obtain an accurate volumetric concentration of the suspended matter loads.

[0062] The present method uses densimetric technique based on precise absolute pressure measurement for production of high-resolution temporal records of suspended matter loads. The method may be suitable for monitoring suspended matter loads volumetric concentrations at high concentrations. The method may be suitable to follow with high accuracy very turbid waters when the turbidity is created by very fine particles. Very fine particles may be clay and silt, or other particles of interest to the industry. The highest the concentration, the highest is the accuracy of the present method.

[0063] The volumetric concentration may be converted to the corresponding mass concentration of suspended matter loads in the liquid. Said mass concentration may be calculated by the multiplication of said volumetric concentration with the density of said suspended matter loads. The mass concentration of suspended matter loads may be expressed in kg/m.sup.3. Said mass concentrations in suspended matter loads may range from 0.25 kg/m.sup.3 to 1000 kg/m.sup.3. More preferably, said mass concentrations in suspended matter loads may range from 5 kg/m.sup.3 to 100 kg/m.sup.3.

[0064] The method comprises the measurement of a pressure at a depth in the liquid. The pressure measured at a depth in the liquid is noted p and is an absolute pressure. The liquid may be in a container or transported in an open channel. Preferably, the pressure in the liquid may be measured at a depth close to the channel or container bottom without interfering with it. The pressure p may be measured by a first pressure sensor. First pressure sensors can be any type of known pressure sensors having an accuracy better than 0.2% FS. The term FS means full-scale. Preferably, first pressure sensors may be of the piezo-electric type.

[0065] The method comprises the measurement of the liquid depth above the first pressure sensor. The measurement of the liquid depth may be determined with an ultrasound probe. Alternatively, the measurement of the liquid depth may be determined with a radar probe. The measurement of the liquid depth is noted L. The liquid depth probe may be fixed outside the liquid. Alternatively, the liquid depth probe may be fixed next to the first pressure probe.

[0066] The method may comprise the determination of the aerial pressure which can be the pressure above the liquid or the atmospheric pressure. Such determination can be made by any known method. In a preferred embodiment, the method may comprise the measurement of the pressure above the liquid. The pressure measured above the liquid is noted p0. In a more preferred embodiment, the pressure above the liquid may be the ambient atmospheric pressure. The pressure p0 may be measured by a second pressure sensor. Said second pressure sensor can be any type of known pressure sensors. The pressure p0 measured above said liquid is used for correction, permitting a more accurate value of the suspended matter loads concentration. In case of constant pressure conditions above the liquid, a known value of the aerial pressure is sufficient to implement the present method successfully. Thus, the measurement of the aerial pressure above the liquid can be omitted. However, the value of the aerial pressure p0 should be inserted in the equations in order to obtain the suspended matter loads volumetric concentration. In case of variable pressure conditions above said liquid, monitoring the pressure value p0 and inserting the value in an equation enable a more accurate measurement.

[0067] The method may comprise the measurement of the temperature of said liquid. The temperature of the liquid may be measured to determine the density of the liquid at said temperature. The measurement of the temperature is noted T. Temperature sensors can be any known temperature sensors. The temperature may be measured by the thermistor or the thermocouple principle. Preferably, the selected temperature measurement principle is the one already implemented and built-in in the immersible high-performance pressure transducer as described with respect to the first and second pressure sensor. Preferably, the temperature sensor is a thermocouple immersed in the liquid. Temperature sensor may be disposed at any distance apart the first pressure sensor. Preferably, the temperature sensor and the first pressure sensor are located close to each other.

[0068] The time resolution between two consecutive sets of measurements may be very short. In one embodiment, to avoid inaccuracy measurements of suspended matter loads when the liquid is in a dynamic system, like an open channel flow, environmental variables may be measured over a period of time suitable for integration, i.e. a time-integration period. The time-integration period may be at least 30 seconds. Preferably, the time-integration period may be 1 minute. Alternatively, the time-integration period may be longer than 1 minute. Values of each environmental variables inserted in the equation may be a linear average of values collected over the time-integration period. In a dynamic system, suspended matter loads concentration may be monitored semi-continuously. In another embodiment, when liquid is in a static system, values of each environmental variables may be a single value collected by the sensors and/or the probe. Preferably, the steps a) to c) of the present method may be repeatable at intervals of time of at least 30 seconds, preferably 1 minute. In a static system, suspended matter loads concentration may be monitored continuously. Thus, the present method may enable the following of the decantation of suspended matter loads.

[0069] The method may provide the measurement of the depth L above the first pressure sensor simultaneously with the measurement of said pressure p. The pressure p in the liquid varies with the liquid depth L. By simultaneously collecting the liquid depth L and the pressure p in the liquid, and compensating for changes in ambient aerial pressure, suspended matter loads volumetric concentration may be calculated with excellent accuracy.

[0070] The volumetric concentration of suspended matter loads is monitored using environmental variables previously measured. The volumetric concentration of suspended matter loads may be calculated according the following equation (I):

[00001]$\begin{array}{cc}\mathrm{Cv}=\frac{.Math..Math.w}{.Math..Math.s-.Math..Math.w}.Math.\left(\frac{p-p.Math..Math.0}{\mathrm{gL}.Math..Math..Math..Math.w}-1\right)& \left(I\right)\end{array}$

[0071] wherein,

[0072] L is the depth at which said pressure p is collected, expressed in m,

[0073] p is the pressure at a depth L in said liquid, expressed in Pa,

[0074] p0 is the aerial pressure, expressed in Pa,

[0075] g is the gravitational acceleration, expressed in m/s.sup.2,

[0076] Cv is the suspended matter loads volumetric concentration, expressed in m.sup.3/m.sup.3,

[0077] s is the density of said suspended matter loads, expressed in kg/m.sup.3,

[0078] w is the density of said liquid at the temperature T, expressed in kg/m.sup.3.

[0079] Preferably, s may be the suspended sediment density. More preferably, if suspended sediment are quartz sands, s is 2650 kg/m.sup.3, which is the density of quartz. If suspended matter loads nature is unknown, s may be taken as equal to 2500 kg/m.sup.3. Alternatively, s may be determined by a known process.

[0080] The mass concentration Cw may be obtained by the equation (II):

Cw=Cvs (II)

[0081] wherein,

[0082] Cw is the suspended matter loads mass concentration, expressed in kg/m.sup.3,

[0083] Cv is the suspended matter loads volumetric concentration, expressed in m.sup.3/m.sup.3,

[0084] s is the suspended matter loads density, expressed in kg/m.sup.3.

[0085] The pressure p0 may be considered as an environmental constant, like the medium ambient atmospheric pressure. The pressure p0 may also be considered as an environmental variable and be monitored with a pressure sensor placed above the liquid during the measurements of the depth L and the pressure p.

[0086] The liquid density w is slightly temperature dependent. Temperature in the liquid may be measured in order to determine the density of the liquid more exactly. The liquid density w may be calculated according to the following equation (III):

[00002]$\begin{array}{cc}.Math..Math.w\left(T\right)=\frac{.Math..Math.w\left(T.Math..Math.0\right)}{1+\left(T-T.Math..Math.0\right)}& \left(\mathrm{III}\right)\end{array}$

[0087] wherein,

[0088] w(T) is the density, expressed in kg/m.sup.3, of said liquid at the temperature T,

[0089] w(T0) is the reference density, expressed in kg/m.sup.3, of said liquid at known temperature T0,

[0090] is the volumetric thermic expansion coefficient of the liquid, expressed in C..sup.1,

[0091] T is the temperature of the liquid, expressed in C.,

[0092] T0 is the temperature at which the reference density of the liquid is known, expressed in C. T0 may be any temperature, since the w(T0) is known.

[0093] is temperature dependent. may be determined by an experimental determination using known method. may be found in reference chemical property tables known in the art.

[0094] Alternatively, may be calculated by an equation allowing an optimum accuracy of the value.

[0095] When the liquid is water, , expressed in C..sup.1, may be calculated using the following equation (IV):

=10.sup.6(62.67914+15.84576T0.11758T.sup.2) (IV)

[0096] wherein,

[0097] T is the water temperature, expressed in C.

[0098] For example, when the liquid is water and the temperature T=20 C., may be 0.000207 C..sup.1.

[0099] When the liquid is not water, another equation has to be used in order to determine the exact value of .

[0100] In applications such as industrial brines or the estuarine environment where the liquid may have high salinity, the method may be complemented by a local measurement of electrical conductivity, which allows to account for density changes attributable to the presence in significant amounts of dissolved ions. Electrical conductivity may be measured at the depth L where the pressure p is measured. Hence, the volumetric concentration of suspended matter loads in a liquid may be optionally calculated according the following equation (V):

[00003]$\begin{array}{cc}\mathrm{Cv}=\frac{.Math..Math.w\left(T\right)}{.Math..Math.s-.Math..Math.w\left(T\right)}.Math.\left(\frac{p-p.Math..Math.0}{\mathrm{gL}.Math..Math..Math..Math.w\left(T\right)}-\mathrm{Cvsalt}.Math.\frac{.Math..Math.\mathrm{salt}-.Math..Math.w\left(T\right)}{.Math..Math.w\left(T\right)}-1\right)& \left(V\right)\end{array}$

[0101] wherein,

[0102] L is the depth at which said pressure p is collected, expressed in m,

[0103] p is the pressure at a depth L in said liquid, expressed in Pa,

[0104] p0 is the pressure above said liquid, expressed in Pa,

[0105] g is the gravitational acceleration, expressed in m/s.sup.2,

[0106] Cv is the suspended matter loads volumetric concentration, expressed in m.sup.3/m.sup.3,

[0107] Cvsalt is the dissolved salt volumetric concentration, expressed in m.sup.3/m.sup.3,

[0108] s is the density of said suspended matter loads, expressed in kg/m.sup.3,

[0109] salt is the density of salt, expressed in kg/m.sup.3,

[0110] w(T) is the density, expressed in kg/m.sup.3, of said liquid at the temperature T, expressed in C.

[0111] Cvsalt and salt are either environmental variables or environmental constants. salt may be found in reference chemical property tables known in the art.

[0112] Cvsalt and salt may be calculated using known methods. For example, Cvsalt may be experimentally determined by the electrical conductivity measured in the liquid. In that case a conductivity probe may be added aside the first pressure sensor. Conversion of measured electrical conductivity into the value Cvsalt may rely on an assumption of the dominant salt effectively present. Salt effectively dominating brine composition or estuarine water composition may be NaCl. Standard open-channel applications can generally be treated neglecting the effect of dissolved salt.

[0113] In a preferred embodiment, the suspended matter loads volumetric concentration may be monitored in a real-time manner. Said concentration may be continuously or semi-continuously monitored.

[0114] As previously mentioned, the method of the present invention may be performed to monitor the volumetric concentration of suspended matter loads in a liquid. Said liquid may be in an open channel flow, an estuary, a river, an industrial conduit, an irrigation channel, an urban conduit, a sedimentation tank, a settling basin, a tank, a reservoir, or any other liquid bodies container. Preferably, said liquid may be in an open flow channel. Preferably, said liquid may be water, oil, derivatives or mixtures thereof. Said derivatives may be liquid residues from oil cracking. More preferably, said liquid may be water.

[0115] For example, a numerical model was done to control the applicability of the method (FIG. 2a). The dark squares represent the Cv determined by the method of the present application, together with the corresponding vertical error bar. The continuous curve represents a numerical simulation of fine evolution of Cv during a time-period. The results depicted in FIG. 2a are obtained using an immersed pressure sensor with an accuracy of 0.025% FS (full-scale). It is noted that, presently, pressure sensors of comparatively higher accuracy (0.010% FS) are already proposed on the market at reasonable price. Use of these modern, higher-performance pressure sensors would thus allow reducing even further the vertical error bars represented in the diagram. FIG. 2a provides thus a conservative estimate of what can be achieved nowadays when implementing the new suspended matter monitoring method.

[0116] The present method for determining the suspended sediment volumetric concentration was also applied in static conditions, such as in a tank. The testing was performed in laboratory conditions. The first pressure sensor was immersed at 0.27 m from the bottom of a 2.50 m deep tank. Water level was measured externally and kept constant at 2.00 m. Pressure above the liquid and temperature of the liquid were known and remained constant during the experiment. FIG. 2b represents the observed versus known suspended sediment volumetric concentration in these experimental conditions. Six different, known, volumetric concentrations of dry matter (density of 2710 kg/m.sup.3) were observed using the absolute pressure measurements. The results show a quite linear profile of the measurement which indicates that the present method is effective for determining the suspended sediment volumetric concentration in a liquid. The slight deviation observed was due to the relatively low volumetric concentrations. Indeed, the results may be influenced by accuracy of the pressure sensor and of the liquid-depth probe. At higher suspended sediment concentrations, the deviation will be less pronounced.

[0117] According to a second aspect of the present invention, a kit of parts is provided for measurement of suspended matter loads volumetric concentration. Said kit of parts comprises a first pressure sensor 11 able to be disposed at a depth L in the liquid and able to measure the absolute pressure p at said depth L in the liquid, a liquid-depth probe 8 able to measure a liquid depth L above the first pressure sensor 11 and a software able to perform the method of the present invention.

[0118] Said kit may further comprise a second pressure sensor 7 able to measure a pressure p0 above said liquid.

[0119] Said kit may further comprise a temperature sensor 12 able to measure a temperature T in a liquid.

[0120] Said kit of parts may further comprise a data management system 10. Said data management system 10 may comprise a processor and a memory encoding one or more programs coupled to the processor. In addition, said data management system 10 may be configured to perform software. Said software may be programmed to perform the following steps: [0121] collect the measurements of environmental variables provided by said first pressure sensor 11, said liquid-depth probe 8 and optionally said second pressure sensor 7 and/or said temperature sensor 12, [0122] insert said measurements in equations, [0123] calculate and display said suspended matter loads volumetric concentration

[0124] The liquid-depth probe may be disposed above the liquid. Alternatively, the liquid-depth probe may be disposed at the surface of the liquid. Preferably, said liquid-depth probe may be an ultrasound probe or a radar probe or an image analysis probe disposed externally to the water flow. Disposing this probe externally may reduce risks of probe damage or fouling in high-concentration conditions.

[0125] Optionally said kit may comprise a probe for measuring the electrical conductivity of the liquid. As most of the conductivity probes also measure temperature, this option may allow eliminating the need of separate thermometer 12.

[0126] Alternatively, an assembly comprising a plurality of first pressure sensors 11, and of temperature sensors 12 may be provided. Hence, the concentration may be monitored at various points or depth in the liquid.

[0127] According to another aspect of the invention, the kit of parts of the present invention may be used for performing the present method for monitoring the suspended matter loads volumetric concentrations.

[0128] FIG. 1 represents a schematic view of the apparatus 1 for collecting and monitoring the suspended matter loads volumetric concentration in a liquid 2, such as water, in a container 3. For example, the container 3 may be an open flow channel, a river bed or a reservoir. The liquid temperature may be measured by a thermometer 12. The pressure p in the liquid may be collected by a first pressure sensor 11. Preferably, the first pressure sensor 11 and the temperature sensor 12 may be disposed at the same depth, close to each other. More preferably, the first pressure sensor and the temperature sensor may be provided within the measuring device 4. The pressure p0 above the liquid may be collected by a second pressure sensor 7. The measuring device 4 may comprise means for grounding 6. Said means for grounding 6 ensure the stability of the measuring device 4 in the liquid 2. Said means for grounding may be a cable affixed to a support 9 or a counterweight. Said support 9 may be an element overhanging the liquid. Said support may be a bridge or an element affixed on the top of a container 3. The measurement of the liquid depth may be collected with an ultrasound probe 8. In one embodiment, said ultrasound probe 8 determines the height L1 between said ultrasound probe 8 and the liquid. The cable 6 has a length L2. The liquid-depth L is determined by removing the height L1 from L2. The ultrasound probe 8 and the second pressure sensor 7 may be affixed to a horizontal support 9. In a preferred embodiment of the invention represented in FIG. 3, said measuring device 4 comprising the first pressure sensor 11 and the temperature sensor 12 may be hanged inside a vertical pipe 5 with holes drilled into it at regular intervals in order to reduce the effects of turbulence on the first pressure sensor 11. In a preferred embodiment, the upper side of the vertical pipe 5 is drilled at regular intervals and the lower side of the vertical pipe under the measuring device is netted like a grid in order to evacuate excessive amount of sediments which would have decanted within vertical pipe 5. The measuring device 4 is placed close to the liquid bed. The distance between the lower part 14 of the measuring device 4 and the bottom 13 of the container 3 is L. Said distance L may range from 1 to 50 cm, preferably from 5 to 30 cm. The first pressure sensor 11 and the temperature sensor 12 communicate or are connected to the data management system 10. Furthermore, said data management system 10 is also connected or in communication with the second pressure sensor 7 and with the liquid-depth probe such as the ultrasound probe 8. All the probes may be fitted to a corresponding conditioner unit. The role of the conditioner unit is to perform the necessary amplification and primary filtering of the signal, as well as providing electric power to the transducer.

[0129] Alternatively, an assembly comprising a plurality of measuring devices 4 may be provided. Hence, the concentration may be monitored at various points or depth in the liquid. Each measuring device may independently communicate with the data management system 10. The method for determining the suspended matter loads volumetric concentration may be performed independently for each measuring device. Said assembly may further comprise one or more liquid-depth probes 8. Said assembly may further comprise one or more primary pressure sensors 11 in order to reduce the bias generated by strongly, turbulent, dynamic effects. Said one or more first pressure sensors 11 may be disposed at the same depth in the liquid. Each of said one or more first pressure sensors 11 measure an absolute pressure p. The average of each absolute pressure measured by each first pressure sensor is used in the present method.

EXAMPLES

Example 1

[0130] The present method is performed to monitor or determine the volumetric concentration of sediments in a river. The first pressure sensor is hung in a tube in order to be located near the bed of the river where suspended sediments volumetric concentration is to be measured. The temperature sensor is also hung in the tube, and is located next to the first pressure sensor. The liquid-depth probe is fixed on a bridge above the first pressure sensor and the temperature sensor. The second pressure sensor is located next to the liquid-depth probe.

[0131] The three sensors and the probe are connected to a data management system. Before measuring the suspended matter loads concentrations in the liquid, it is possible to input the environmental constants used in equations. Environmental constants are maximal expected water depth (allowing tuning electronic gain of the pressure transducer to improve measuring accuracy), suspended matter loads density, and reference water density at known temperature. The user inserts environmental constants into the software performed by the data management system as well as the periodicity of measurements (e.g. 30 seconds). Then, software performed by the data management system records environmental variables (p; p0; L; T) during 30 seconds. The data management system calculates the means of said variables over this period of time. Finally, software performed by the data management system inserts means calculated into the equation as presently described. The suspended sediment concentration is displayed.

Example 2

[0132] The present method is performed to monitor the concentration of sediments in a tank or the density of the liquor contained in a tank. The first pressure sensor is fixed on the bottom of the tank where the suspended sediments volumetric concentration is to be measured. The temperature sensor is fixed next to the first pressure sensor. The liquid-depth probe is fixed underneath the roof of the tank, above the first pressure sensor and the temperature sensor. The second pressure sensor is located next to the liquid depth probe underneath the roof of the tank.

[0133] The three sensors and the probe are connected to a data management system. Before measuring the suspended matter loads volumetric concentrations in the liquid, it is possible to calculate the environmental constants used in the calculations. Environmental constants are suspended matter loads density; reference liquid density at known temperature. The user inserts environmental constants into the software performed by the data management system. There is no need to collect environmental variables over a period of time because of the non-dynamic state of the system. Then, data system management collects and records environmental variables (p; p0; L; T) in a real-time manner. Finally, the data system management inserts environmental variables into the equations to calculate and display the suspended sediment concentration.

[0134] The terms and descriptions used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the invention as defined in the following claims, and their equivalents, in which all terms are to be understood in their broadest possible sense unless otherwise indicated. As a consequence, all modifications and alterations will occur to others upon reading and understanding the previous description of the invention. In particular, dimensions, materials, and other parameters, given in the above description may vary depending on the needs of the application.