Patent Application
20120156711
None.
This invention was not federally sponsored.
The present invention relates to the environmental characterization of liquid wastes in general, such as activities of monitoring, control and also treatment. More specifically it relates to a self-calibration system and method that allows the joined performance of optoelectric and respirometric sensors for instant and accurate ascertainment of the Biochemical Oxygen Demand (BOD) in liquid industrial wastes (RILES).
The BOD (Biochemical Oxygen Demand) is an important index for monitoring organic pollution in liquids. It is an indirect measurement of the amount of organic material present in liquids in general and water in particular, which can be biologically degraded by microorganisms. Since the dissolved oxygen is completely consumed during the process of biochemical degradation of the organic material, its amount can be expressed, in an equivalent manner, in terms of the amount of oxygen required (respirometry). Thus, the BOD is able to identify in a quantitative manner the existing degradable load in waste waters or in a receptor body.
Depending on temperature conditions, other nutrients availability and absence of inhibitors, the whole degradation process normally takes approximately 20 days. As a partial analytical measure, but statistically representative of the organic load of a liquid waste, a conventional method has been used, denominated BOD5, which consists of incubating the sample for 5 days at 20° C. Even though this is a normalized method, it is complicated and its major disadvantage is that the BOD quantification process takes 5 days, a lapse of time that does not allow for making timely and efficient decisions.
Due to the previously mentioned problem of response time in determining the BOD, it has been endeavored to perform almost instant online BOD determinations without waiting the 5 days of incubation for the conventional test to be performed.
For this reason, the prior art has utilized ultraviolet and fluorescence spectroscopic techniques that, when used together in a sequential manner, allow a determination of the BOD of a sample with high reproducibility and reliability in approximately 2 to 3 minutes.
The Chilean patent application, document CL 3256-2004 entitled “Determination of BOD in RILES using a UV-fluorescence method” describes optoelectric equipment for BOD determination in RILES (liquid industrial wastes) from industrial plants, in rivers, channels and lakes, wherein this equipment consists of two sensors, one for UV absorption and the other for fluorescence emission. Both work sequentially in the same sample and the combined data are processed by a nonlinear neuronal network. However, the error in determining the BOD using this technique is between 15 to 20% when compared to the BOD value determined by the normalized standard chemical method. While this is a considerable amount of error, the result is obtained in seconds.
The prior art has developed different types of biosensors based on respirometry and related methods that can determine the BOD of a sample in situ and in real time, and also to perform the measurement in a simple and rapid manner (in minutes). The biosensors consist of a combination of a transductor and a biological element, such as oxygen electrodes and microorganisms respectively.
The prior art on-line measuring systems consist basically of a unit (membrane or bioreactor) colonized by microorganisms (they can be specific to the liquid to be monitored), which is kept in a continuous flow due to a recirculation pump and fed with waste liquid by peristaltic pumps. Simultaneously, another pump saturates the liquid to be monitored (container fixed to the equipment or system) with oxygen, and a probe measures the dissolved oxygen in the liquid. This measurement can be performed with different configurations.
For instance, microorganisms immobilized in polyacrylamide gel and an oxygen electrode can be used (see “A Rapid method for Estimation of BOD by using Immobilized Microbial Cells” by Isao Karube et al. Biotechnology and Bioengineering Vol XIX, p. 1535-1547, 1977).
Also, the registry of the respirometric activity of the microorganisms in a reactor can be employed, which are extracted in a small amount (aliquot) from a chemostat.
STIP ISCO GmbH has a biosensor named biox 1010, which measures in an automatic manner the BOD and toxicity of water from different origins. The utilized method is respirometric, based on a microbial culture originated from the water to be monitored which is gradually deposited on insoluble supports inside the reactor (see EP 0369490), whose composition, concentration and activity are constant. It metabolizes the organic matter of the samples so that the oxygen consumed for its oxidation enables the determination of the BOD values and toxicity.
The apparatuses and methods previously described are deficient because they hold a limited amount of biomass which decreases the range of measurement of waters with low BOD. This is also the case with devices and methods that use membranes supported on the oxygen sensor. Additionally, devices and methods based on microorganisms supported on insoluble material must be generated in situ from the bacteria present in the liquid to be monitored. This makes it impossible to design the microbiological load of the reactor. Further, it requires a colonization period of many days that must be repeated every time the biofilm is deteriorated as a result of use or toxicity.
In the case of an apparatuses based on feeding from a chemostat, the operational requirements include a large number of feeding, draining, ventilation, recirculation, and cleaning pumps, which creates highly complex equipment that requires a long colonization time.
Another patent document is the application CL 84-2005 (PCT/EP2006/050235), entitled “Respirometry biosensor for rapid BOD determination in waters, which consists of a removable cartridge-type bioreactor (CTB), a system and method for rapid BOD determination.” It describes a cartridge that contains an adjustable number of capsules, which in turn hold immobilized adjustable masses of microorganisms, thereby permitting the design of a simple apparatus and use of a bioreactor with shorter colonization times. Reactors of this type can be cold stored allowing easy replacement of the operating reactor.
However, all the devices and methods previously described have shown to work with restrictions related to the range of operation and response time and not widely used in industrial applications. As of yet, a joined performance of optoelectric sensors and biosensors with control algorithms that allow its calibration has not been achieved. For that reason there, is not a dominant design for rapid BOD determination.
The advantage of the optoelectronic method is its immediateness of response, which can be within the range of 10 to 15 seconds; however, the obtained result is not extremely accurate. This value, though, is within an order of magnitude of the real BOD. The advantage of the respirometry method is that the response is direct, but it can take hours to obtain a BOD result.
The present invention provides a system and method that combines the fast response time of the optoelectric signal and the simplicity of the respirometric cartridge wherein the greater accuracy of the respirometric biosensor is added to the speed of the optoelectric sensor, with the purpose of improving the accuracy of the measurements and the speed of the integrated monitoring process and on-line control of the environmental variable of interest and removing the operative restrictions of a fixed work range that cannot be set according to the BOD to be determined.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. The features listed herein and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
It should be understood that while the preferred embodiments of the invention are described in some detail herein, the present disclosure is made by way of example only and that variations and changes thereto are possible without departing from the subject matter coming within the scope of the following claims, and a reasonable equivalency thereof, which claims I regard as my invention.
In this manner, the present invention provides a system and method that integrates optoelectronic sensors and biosensors, wherein the first step combines the instant methodology with the optoelectric sensors that enables a user to set the boundaries or define the range of work requested to the biosensor. The boundaries or range of work will depend on the organic load of the sample, which at the same time will determine, as a second step, the volume of the sample entering the respirometry biosensor. The volume of the sample will also be adapted to the measurement range of the cartridge.
In fact, both the methodology and device work in parallel form, out of phase by a small period of time that is equal to the processing of the RIL (liquid industrial waste) sample. This sample is analyzed by the sensors, such as UV, fluorescence, or both, which are denominated optoelectronic sensors, such as the ones described in the patent application CL 3256-2004, wherein the sample is processed in a processing unit, according to the organic load of the analyzed sample.
As shown in
The received data are processed by the process and control unit (4) to determine with certainty the type of organic load of the sample and a computational program decides whether to apply a simple linear correlation, polynomial correlation, or neuronal networks, as the one disclosed in the patent application CL 3256-2004.
In this manner, a microprocessor defines, through specialized algorithms, a range of work for the respirometric unit (6), which is achieved by controlling the opening of the entrance valve (5) of the respirometric unit (6), thereby defining the entrance volume, such as in ml., to the respirometric unit (6).
The respirometric unit can be similar to the one defined in the application CL 84-2005. In this manner, the BOD that is determined will not exceed the upper limit (saturation) or lower limit (does not measure) of the measuring range of the removable and disposable cartridge type biosensor (BTC). The biomass, located inside of the disposable cartridge type biosensor, is encapsulated in a polymeric organic matrix suspended in a maintenance solution, where the maintenance solution is preferably calcium chloride.
In this manner it is achieved a fast and accurate measurement of BOD of the RILES analyzed by the present invention. The results can be obtained locally. In other words, the results can be read directly from the device. Alternatively, the results can be read remotely wherein the wireless means of transmitting the results is preferred. However, the transmission of the results can be accomplished through cables if wireless means are not possible.
