MONITORING DEVICE FOR TOXIC SUBSTANCES IN WATER

On-site probes capable of transmitting signals are currently available for aquatic ecosystems although they only measure hydraulic parameters (for example, water level, flow) and inorganic chemical components (for example, oxygen, pH, suspended solids, etc.). In general, these probes have several disadvantages: they are for specific parameters and / or are intended for laboratory use and / or they are expensive and / or they are demanding maintenance and / or the interpretation of the results is difficult. In view of the limitations observed in the state of the art, the need has been seen to improve the diagnosis of the waters for pollutants. Additionally, rapid detection of pollutants would be desirable, for human and ecosystem safety, for example, at the exit of wastewater treatment stations (WWTP) or for drinking water supply. The present invention is intended to address these and other problems. In general, a device for monitoring toxic substances in water is proposed, which includes a first reference chamber with a purifying filter and a second monitoring chamber with an inert filter (figure 1). Both chambers are submersible and each has: an inlet and an outlet for the flow of water, a housing module to house at least one biofilm, and a fluorimeter to measure the fluorescence in the biofilm. The housing module must receive external light for the biofilm. The device also incorporates a data acquisition unit to collect the fluorescence measurement of the biofilm in each chamber. Thus, it is possible to establish a local comparison between a biofilm with purified water from toxic substances and another biofilm with raw water and, with this, discriminate functional changes due to contaminants. This specificity allows to rule out changes in the biofilm caused by other factors. For example, there are variations in climatic conditions that are not due to contamination but that cause changes in the biofilm and, therefore, could generate false positives of contamination. The device can optionally integrate passive samplers for organic and metal contaminants. By extracting the sample contained in the passive sampler and analysis, which can be analyzed later in the laboratory, supplemental information can be provided and it serves as confirmation that the changes in the biofilm are actually due to contaminants. Likewise, it also serves to recognize if the functioning of the filters is correct. The device can optionally have a data transmission system. The data transmission system can communicate with other remote systems in charge of reviewing the information and acting accordingly. For example, taking actions such as generating alarms in case of contamination, maintenance notices, etc. Materials used to manufacture the monitoring device are cheap and reusable, biofilms can be easily cultivated both in field and in laboratory, fluorimeters have very different prices depending of their characteristics, it is recommended to use pulse amplitude modulated technology in order to measure not only fluorescence but also other parameters such as photosynthetic efficiency.

In FIG. 1 a diagram is schematically shown according to a realization, the monitoring device 30 allows a continuous detection of the presence of contamination in the water. Device 30 uses biofilm 5. Biofilm 5 is a very sensitive living community and serves as the primary detection element. Device 30 has a configuration that avoids interpretation errors generated by external factors not related to the presence of contaminants that are to be detected. In operation, device 30 detects changes by means of biofilm 5 fluorescence measurements made in two different spaces, immersed in the aquatic environment, through its corresponding fluorimeters 6. A first space serves as a local reference with which to have conditions in the environment without toxic substances. Changes in the environment due to the presence of toxic substances are monitored over a second space. To create these two spaces in contact with the aquatic environment, chambers 1, 2 are designed. Among other specific properties, both chambers 1, 2 must allow the biofilm 5 to develop. In case of contamination, the reference chamber 1 must keep the biofilm 5 in water purified from contaminants, in order to identify the change suffered by the other biofilm 5 that is in the monitoring chamber 2 exposed to contaminants that exist in the middle. In reference chamber 1, the incoming water is purified from contaminants, but maintains other characteristics (temperature, pH, nutrients, etc.). The measurements of biofilm 5 from each chamber 1, 2 are compared. Based on this comparison, if there is a significant difference, the monitoring device 30 is capable of generating a warning signal. With this warning signal an alert can be issued. For example, the warning signal can be easily transmitted using wireless technology such as WiFi. The monitoring device 30 thus makes it possible to verify the quality of the water continuously. The design also supports the use of passive samplers to detect contamination by pesticides, pharmaceutical compounds and heavy metals, among others. For this, it can integrate, in addition to a biofilm 5, a passive sampler for inorganic contaminants 4 (DGT) and a passive sensor for organic pollutants 3 (POCIS). These passive sensors 3, 4 can be used as a backup for chemical analysis and identification of contaminants. The type of fluorimeter 6 used is preferably pulse amplitude modulated PAM for rapid evaluation of changes in structural and functional indicators. In order to establish whether the differences in measurement of the fluorimeter 6 of the reference chamber 1 and the fluorimeter 6 of the monitoring chamber 2 are significant, they are calibrated in the field and in the laboratory. It should be noted that biofilm 5 is usually grown in clean water conditions. Biofilm 5 reacts to exposure to contaminants with changes in functional parameters (eg, photosynthesis efficiency, basal fluorescence, etc.). These changes are detectable by fluorimeter 6. Advantageously, the presence of a local reference avoids false positives. Often external factors not related to toxicity can affect the values ​​measured in the biofilm. For example, these parameters are influenced by temperature, turbidity, or nutrients. Previously, a proper calibration is performed in the laboratory. With the measurements, various parameters can be obtained, among which the following can be mentioned:

- YII, photosynthetic yield, in a range from 0 to 100% theoretically, and with normal values ​​for a biofilm in good condition between 60% and 70%;

- Basal fluorescence: represents an indirect measure of biomass and can rise or grow or remain constant during exposure, (the range depends on the calibration of the sensor that is done prior to installation);

- Y (NPQ), yield of regulated non-photochemical fluorescence quenching, that represents the energy that cells emit in the form of heat, is a protection mechanism and is an indicator of stress;

- Y (NO), yield of non-regulated non-photochemical fluorescence quenching: this parameter indicates a dysfunction of the photosynthesis and / or protection mechanisms.

In fact: YII + Y (NPQ) + Y (NO) = 100%, if the cells lower their energy by photosynthesis, the energy expended in heat or used, for example, for detoxification will grow. Laboratory tests indicate the relationship between effect and toxic mixture. The local reference also allows to appreciate small variations that would be confused with effects by non-toxic factors.

The monitoring device 30 can be coupled to a data acquisition unit 18 (which can be submersible) wired to a surface equipment 19, located out of the water and powered by an energy production system 26, for example, energy renewable for greater autonomy. In the surface equipment 19, a communication unit allows the possibility of sending the acquired information for processing, for example, to a remote computer 21 that, among other actions, is in charge of issuing an alert based on the data received. Different types of alerts can be set depending on the estimated degree of toxicity.

The monitoring chamber 1 and the reference chamber 2 are installed in the direction of the water flow so that the current can transport possible contaminants to the sensors. Both chambers can be manufactured with a cylindrical shape in methacrylate (PMMA), sometimes commonly called Plexiglas with a thickness of about 3 mm with a capacity of several liters.

In the reference chamber 1, the water passes through a semipermeable membrane 7 and reaches an activated carbon purifying filter 8. When the activated carbon is in the form of grains, the purifying filter 8 includes elements, for example, a housing also made of PMMA material, or another inert material (or another material with similar characteristics), with a perforated base to allow water to escape, but not carbon, this perforated base has regular 1-2 mm diameter holes. To prevent accidental release of granular activated carbon, an additional 5 mm thick layer of glass wool or another inert semi-permeable membrane can also be added to the filter base. In this way, the water arrives clean and without material from the filter itself to the biofilm 5.

In the monitoring chamber 2, the water passes through a semipermeable 7 to the inert filter 9 of glass wool where it arrives at the biofilm 5 not purified. The inert filter 9 includes the same elements of the purifying filter 8 with the difference that it is filled with glass wool instead of activated carbon.

Chambers 1, 2 are specially designed to ensure that the biofilm 5 has water, light and nutrient flow to survive. Among other considerations, it must allow the passage of light, be sufficiently resistant to withstand working conditions, and be inert with respect to the substances to be analyzed. For example, PET is not suitable because it can adsorb contaminants. Preferably, it should be a low cost, acid and dilute solvent resistant, so that it is easy to clean. It should be noted that other components of each chamber 1, 2, such as screws or rivets, must also be made of inert materials. For these parts, stainless steel or polytetrafluoroethylene (PTFE) also known as Teflon are suitable materials.

As mentioned, an inert and semipermeable membrane 7 is placed at the entrance and exit of the reference chamber 1, allowing the preferential passage of certain substances over others. The membrane can, for example, be made of sulfurone polyester (PES) material. Membrane 7 has various functions:

- Retain excess suspended solids (that may interfere with the fluorimeter).

- Stabilize the water flow so that it is the same in the two chambers.

- Avoid rapid colonization of the biofilm with resistant species to maintain a sensitive biofilm for a longer time.

- Ensure a low flow of water through the purifying filter 8 to ensure efficiency in the removal of contaminants.

The water entering the reference chamber 1 is purified with activated carbon or a material with similar characteristics. Polar organic contaminants are retained, generally with an octanol-water partition coefficient, KOW≤3, and heavy metals.

The octanol-water partition coefficient of a substance (KOW), is the ratio of the concentrations of that substance in a biphasic mixture of two immiscible solvents in equilibrium: n-octanol and water. This coefficient therefore measures the differential solubility of a solute in these two solvents. N-octanol has been chosen because it is an organic compound that simulates either the lipid material of the biota, or in organic particles and sediments. This coefficient gives an idea of ​​the hydrophobic character of a substance or the affinity towards lipids of a substance dissolved in water.

It should be noted that the purifying filter 8 does not contain substances harmful to the biofilm, for example, a biological filter with bacteria would be inappropriate since it could alter the biofilm. It must allow the flow of water, for example, with ultrafiltration membranes it would be necessary to put a pump to allow the flow of water. Preferably inexpensive, easily replaceable, reusable. For all of the above, activated carbon is a good choice, it is heat reactivable and reusable.

Additionally, it is desirable for it to be a homogeneous material to avoid accumulation of water in a filter area, and to homogeneously reach the entire volume of the filter. One possibility is that it is granular because it has less opposition to the flow of water.

On the other hand, in the monitoring chamber 2, the water after passing through the passage membrane 7 reaches an inert filter 9 of glass wool or similar characteristics. In this case, the inert filter 9 must not react with organic or polar pollutants (KOW ≤ 3) or with heavy metals, but it must meet the rest of the characteristics noted above for the purifying filter 8.

The hydrodynamic design of the two chambers 1, 2 must ensure adequate retention of contaminants. For example, a cylindrical shape ensures an even distribution of the water flow that passes through the filters. Since biofilm 5 is a living microbial community with regenerative capacity, it requires little maintenance.

It is recommended to improve the efficiency of the device, that the biofilm 5 is grown in a clean point and then transferred to the device. In this way, it is facilitated that the most sensitive species are present.

The design of the device 30 must allow a relative isolation of the biofilm within the reference chamber 1 and the monitoring chamber 2, which minimizes the colonization of resistant species by means of pass 7 membranes at the entrance and exit of both chambers. A balance is sought that slows colonization by resistant species without completely isolating biofilm 5 to maintain water flow. The extracts of the passive collectors 3, 4 can be analyzed for a better determination of the quality and characteristics of the water. In this way it is also possible to ensure not only a better identification of contaminants but also the proper functioning of the filters 8, 9.

Versatility, the properties of the filters 8, 9 can be chosen to adapt specifically to the local conditions of the water to be analyzed. Typically, the useful life of a filter varies from two weeks to several months, depending on the quality of the water.

FIG. 2 is an example of an exploded view of a possible monitoring camera 2 that is coupled to electronic means to acquire, transmit and process the information coming from the monitoring camera. Although not shown in this figure, the reference camera would also be coupled with the same electronic means. In the monitoring chamber 2 it can be seen how several biofilms 5 are housed in a housing module 10 that is inside the chamber and is manufactured in PMMA.

In this embodiment, the filter 9 has an associated tubular lateral structure that defines an inner smaller chamber made of PMMA or another material with similar characteristics.

Housing module 10 can be easily removed at one end of chamber 1, 2, and is made of PMMA. To hold the elements, the PTFE screws 27 (rivets or similar) are used on a closure 17. In this example, the housing module 10 has the capacity to hold up to five biofilms 5. The construction guarantees illumination, essential for the growth of the biofilm 5. All the materials used in the assembly of the device (PMMA, PTFE and stainless steel) are resistant and inert. Thanks to the inert filter 9, nutrients and eventually micro-contaminants penetrate.

To ensure correct illumination of the biofilm 5, an orientation of the housing module 10 towards the surface must be maintained. For this, the mass distribution is carried out in chamber 2, or an additional structure such as a ballast, a counterweight, some ties, etc. can be used, that guarantees this orientation.

Regarding the elimination of the disturbance of the suspended sediment greater than 0.1-0.2 μm and to limit the colonization of biofilm 5 with resistant species, membranes 7 are placed, for example semi-permeable and micro-porous hydrophilic polyether sulfone (PES) membranes, with porosity 0.1-0.2 μm. PMMA 16 supports for the membranes with 27 stainless steel screws are placed at the entrance and exit of chambers 1, 2.

The placement of passive samplers 3, 4 should maximize the exposure of the sorbent surface. The biofilm 5 and the fluorimeter 6 are placed immediately after the filters 8, 9 ensuring the contact of the biofilm 5 with possible micro-contaminants present in the aquatic environment. Furthermore, the biofilm 5, which is exposed to light, is placed approximately 2-3 mm from the fluorimeter 6, ensuring a correct reading of the fluorescence signals. The tube-like chamber design offers good hydrodynamics and good filter efficiency.

See experimentally obtained values:

2.8-7.4 mL / min / cm2 @ 0.7 bar, 10 ps with a 0.1 μm PES semipermeable 7-pass membrane;

19.3-34.6 mL / min / cm2 @ 0.7 bar, 10 ps with 0.2 μm PES semipermeable 7-pass membrane.

These values ​​have been shown to allow growth, as well as the accumulation of micro-contaminants in the biofilm 5, the accumulation of contaminants also in the passive samplers 4, 5.

Although the manufacturing material is very resistant, it may be advisable in certain environments to place both chambers 1, 2 inside a protective stainless steel cage. The cage can be used to maintain proper orientation for the light to reach the biofilm 5. Also to prevent theft or impact of stones brought by the current.

Regarding electronic means, there are multiple solutions to collect and process data from measurements. One possibility to transmit data from the two passive sensors 4, 5 is to do it through an underwater cable 16 (RS-485 / S) that leaves the device through a small exit hole 14 in each camera 1, 2 to one data acquisition unit 18 with waterproof coating. The data can be recorded in a storage memory, for example in an internal ring buffer and on a non-removable micro SD card. The data acquisition unit 18 is connected via a waterproof cable 16 (RS-485 / S) to the surface equipment 19, located out of the water and powered by an energy (preferably renewable) production system 26, composed of one or two solar panels or, in places with low exposure to sunlight, a submerged hydraulic turbine that converts water energy into mechanical energy plus a hydroelectric generator that converts this mechanical energy into electricity.

It is possible to define a monitoring system that includes one or more devices 30 for comprehensive management of water monitoring in different locations. Each surface equipment 19 is in charge of transmitting data to a fixed destination, for example, virtually to a cloud server 20 by means of a transmission unit 23 that can be a telephone or satellite modem with Wi-Fi technology or similar. The data stored in the cloud 20 can be accessed and analyzed from a remote computer 21 with which, in the event of a significant difference in measurements between the two cameras 1, 2, it can program the automatic sending of a warning signal 24 to a number of recipients. For example, the alert can be transmitted to surveillance personnel through one or more surveillance terminals 22. The surveillance terminal 22 can, for example, be a smartphone with a mobile app or a computer, tablet, etc.

Various useful functionalities can be added, for example sensor control, or the reading recorded by them. For example, in the case of fluorimeter 6, control software can be installed to perform a pulse saturation analysis and a standard fluorescence parameter calculation. The used can define the execution of easily programmable custom experimental procedures using batch files. Data export in CSV (Comma Separated Values) format can also be implemented to record original fluorescence traces, saturated pulse data, and light response curve parameter estimates.

The passive integrated sensors 3, 4 that are capable of accumulating organic compounds such as pesticides, pharmaceuticals and heavy metals can be recovered and the extracts can be analyzed in the laboratory, using chromatographic and mass spectrophotometric techniques, in the event of a significant change detected in the biofilm 5. This would be the way to deal with an episode of contamination. The adsorbents can be extracted and analyzed, providing valuable information, for example to identify the compounds possibly responsible for the toxic effects registered in the biofilm.

Current biomonitoring (in particular for biofilms) fails to properly assess the impacts of micropollutants, there is an increasing need (and social expectation) for the development of functional indicators and monitoring devices for the monitoring of aquatic health. The device proposed is very promising to tackle this objective. Indeed, continuous monitoring methods for surface water quality need to be developed and improved, especially in the current clime: the device propose a continuous online monitoring, filling this gap.

The presence of the reference chamber allows to rule out changes in the biofilm caused by other factors and consider only changes produced by pollutants.

Another advantage of the device is that it can be designed in a versatile way depending on the working environment. For example, the filter material can be chosen according to the type of contaminants the user wants to retain.

On-site probes capable of transmitting signals are currently available for aquatic ecosystems although they only measure hydraulic parameters (for example, water level, flow) and inorganic chemical components (for example, oxygen, pH, suspended solids, etc.). In general, these probes have several disadvantages: they are for specific parameters and / or are intended for laboratory use and / or they are expensive and / or they are demanding maintenance and / or the interpretation of the results is difficult. In view of the limitations observed in the state of the art, the need has been seen to improve the diagnosis of the waters for pollutants. Additionally, rapid detection of pollutants would be desirable, for human and ecosystem safety, for example, at the exit of wastewater treatment stations (WWTP) or for drinking water supply.

The device is of particular interest to water manager and industries to check Waste Water Treatment Plants (WWTP) outflows, drinking water and river water quality with the goal to act as a warning system and to reduce up to 50% the costs of intensive monitoring (assuming that rives in good status will be only checked in remote). The device is particularly indicated in case of reuse of outflows of WWTP for agricultural purposes and other purposes directly related with human health. Considering a wide application in WWTPs outflows check (about 71,000 municipal WWTPs are operational at present in the EU and Switzerland), the impact in EU society will include an improved water quality diagnosis leading to a reduction of monitoring costs and higher water safety, resulting in the improvement of the ecosystem and human health. Users of the technology will be environmental and laboratory technicians related with water quality control (WWTPs, river monitoring). Beneficiaries of the technology will be the same clients, for saving money in water monitoring and gain in efficiency and citizens for the improvement in water safety.

Benefits:

Current biomonitoring (in particular for biofilms) fails to properly assess the impacts of micropollutants, there is an increasing need (and social expectation) for the development of functional indicators and monitoring devices for the monitoring of aquatic health. The device proposed is very promising to tackle this objective. Indeed, continuous monitoring methods for surface water quality need to be developed and improved, especially in the current clime: the device propose a continuous online monitoring, filling this gap.

The presence of the reference chamber allows to rule out changes in the biofilm caused by other factors and consider only changes produced by pollutants.

Another advantage of the device is that it can be designed in a versatile way depending on the working environment. For example, the filter material can be chosen according to the type of contaminants you want to retain.

On-site probes capable of transmitting signals are currently available for aquatic ecosystems although they only measure hydraulic parameters (for example, water level, flow) and inorganic chemical components (for example, oxygen, pH, suspended solids, etc.). In general, these probes have several disadvantages: they are for specific parameters and / or are intended for laboratory use and / or they are expensive and / or they are demanding maintenance and / or the interpretation of the results is difficult. In view of the limitations observed in the state of the art, the need has been seen to improve the diagnosis of the waters for pollutants. Additionally, rapid detection of pollutants would be desirable, for human and ecosystem safety, for example, at the exit of wastewater treatment stations (WWTP) or for drinking water supply.

Applications:

The device is of particular interest to water manager and industries to check Waste Water Treatment Plants (WWTP) outflows, drinking water and river water quality with the goal to act as a warning system and to reduce up to 50% the costs of intensive monitoring (assuming that rives in good status will be only checked in remote). The device is particularly indicated in case of reuse of outflows of WWTP for agricultural purposes and other purposes directly related with human health. Considering a wide application in WWTPs outflows check (about 71,000 municipal WWTPs are operational at present in the EU and Switzerland), the impact in EU society will include an improved water quality diagnosis leading to a reduction of monitoring costs and higher water safety, resulting in the improvement of the ecosystem and human health. Users of the technology will be environmental and laboratory technicians related with water quality control (WWTPs, river monitoring). Beneficiaries of the technology will be the same clients, for saving money in water monitoring and gain in efficiency and citizens for the improvement in water safety.

Current development status

Laboratory prototypes

Desired business relationship

Technology selling

Patent licensing