The present invention is related with the environmental characterization of liquid residue, as much as what refers to control and monitoring activities, as of treatment, more specifically with a biosensor for determining the biochemical oxygen demand (BOD) by respirometry.
The BOD is an important index for the organic pollution monitoring in liquids, therefore, is an indirect measure of the amount of organic material in liquids, in general and in water in particular, that can be biologically degraded by microorganism, since the dissolved oxygen get consumed during the degradation biochemical process of the organic material, then the said oxygen quantity can be expressed in equivalent form in terms of the quantity of required oxygen (respirometry), thus, the BOD is capable of identify in a quantitative way the degradable charge existing in residual water or in a body receptor.
Depending on temperature conditions, other nutrients availability and absence of inhibitors, the whole degradation process takes normally about 20 days. As a partial analytic measure, but statistically representative of the organic charge of a liquid residue, a conventional method denominated BOD5 has been used that consist in incubating the sample for 5 days at 20° C., However this is a method that although is normalized, it is complicated and above all it duration of 5 days for quantifying the BOD does not allows to take opportune and efficient operational actions.
Consequently with the former, different types of biosensors have been developed based on respirometry and also associated methods that allows to know the BOD in situ and on real time , and obtain this measurement in a simple and fast form (in the order of minutes).
The biosensor consists on a combination of a transducer and a biological element, for example as microorganism and oxygen electrodes (see
The on-line measurement systems consist basically in an unity (membrane or bioreactor), populated of microorganism (that can be specific of the liquid to be monitored) in which a continuous flow is maintained through a recirculating pump, being feed by peristaltical pumps that load the residual liquid simultaneously other pump saturates of oxygen the monitoring liquid (recipient fixed to the equipment or system), and a probe for the measurement of dissolved oxygen. This measurement can be made with different configurations.
By example immobilized microorganism on polyacrylamide gel and a oxygen electrode are used (“A rapid method for estimation of BOD by using Microbial Cells”, Isao Karube and cls., Biotechnology and Bioengineering Vol XIX , p.1535-1547, 1977).
Also the respirometric activity register of the microorganisms in a reactor is used, which are extracted in a little quantity (aliquot) from a chemostat.
STIP ISCO GmbH has a biosensor named biox 1010, for the measurement of the content of BOD and toxicity in an automatic form waters of different origin. The method used is respirometric, based on a microbial culture coming from the water to be monitored that gradually deposits over insoluble supports inside the reactor (EP 0369490), whose composition, concentration and activity are constant. It metabolizes the organic matter of the samples such that consumed oxygen for it oxidation allows to know the BOD and toxicity values.
The apparatus and method previously described have the difficult of containing a limited quantity of biomass that reduces the range of measurement to waters with low BOD. Is the case of those that use membranes supported over the oxygen sensor. On the other hand those based on microorganism supported over insoluble material, must be generated in situ over the base of the bacteria present in the liquid to be monitored making impossible design the microbiological load of the reactor and requiring priming time of many days that must be repeated every time that the biofilm get deteriorated because of use or toxicity.
In the case of apparatus based on feed from a chemostat, the operative requirements make necessary a great number of feeding pumps, empty, air, recirculation and wash generating highly complex equipment, sharing the limiting of priming time
In the actual invention this problems are approached and for giving a solution it is proposed a removable cartridge that contains an adjustable number of capsules inside of which there are adjustable masses of immobilized microorganisms, allowing the design of a simple apparatus and the use of a reactor with less prime times. Reactors of this type can be stored in cold allowing the replacement of the operating reactor easily.
In this way, the present invention provides a system that operates like a biosensor, for the fast measurement of DBO, where the apparatus used as respirometric element is a cartridge type removable and disposable bioreactor (BTC)(1), in which the biomass is encapsulated in a polymeric organic matrix suspended in a support solution which, in the preferred modality is calcium chloride.
As shown in
In order to start the measurement, it is necessary to inject a sample, which is obtained from an aliquot of the canals, rivers or lakes (RILES) (7), inside the BTC (1) trough a second inlet (70). The injected sample is pulse type (the whole sample is injected at a time).
Before injecting the sample, the BTC is acquiring data from the dissolved oxygen sensor (200) to an acquiring data equipment, inside zone 1 (see
Once the data is obtained, the dissolved Oxygen consumption and recovery zones data are selected, that is to say zones 2 and 3, where they are numerically integrated to obtain a first area under the curve (A1).
Zones 1 and 4 are worked with the data of the respective base lines. An interpolation is done creating a theoretical base line corresponding to the dissolved oxygen consumption zone (zone 2) and the dissolved oxygen recovery zone (zone 3). The theoretical base line is integrated with which a second area under the curve is obtained (A2).
To calculate the “Respirometric area” the resulting areas must be subtracted according to:
Respirometric areaRIL=A2−A1
The evaluation of BOD, can be done of different forms, one way is comparing the Respirometric AreaRIL versus the respirometric area of standard or known values of DBO measured previously.
Other way is comparing the Respirometric areaRIL versus a calibrated curve previously constructed with standard known BOD solutions.
BOD=f(Respirometric area)
The cartridge type bioreactor (BTC) has an immobilized quantity of biomass on capsules (100), which was previously generated, that means, we have a preexistent biomass quantity that can be adjusted to the capsule (100), the capsule size (100) is also adjustable within certain limits, while the capsules number is also adjustable to the BTC size (1). All this indicates that the operation characteristics of the removable and disposable BTC (1) can be adjusted to the user requirements.
The BTC priming or activating time is less than the commercial alternatives available today, this prime or activating time goes from 4 hours to 1 day.
The BTC (1) is constructed from a cartridge of inert material with adapters for: inlet for feeding the support solution (40), outlet of liquid (41), measurement sample inlet (70), air inlet (50), air outlet (51), dissolved oxygen sensor (200) that in a preferred modality is removable. Additionally contains the capsules suspended on storing liquid or in support liquid when is in operation.
The capsule forming solution consist on 1% sodium alginate where a population of bacteria Enterobacter sakasakii was introduced and previously homogenized and formerly isolated from residual water until reaching to a microbial concentration of 0.5 grams dry biomass/liter of capsule. This solution was dropped from the capsule device to a hardening solution of calcium chloride, 0.05 molar, generating capsules on the order of 1 millimeter diameter.
For constructing the BTC, 20 grams of capsules suspended on 40 cc of support liquid were used, consisting in a calcium chloride solution 0.05 molar.
The capsules were stored cold on trypticase soy (TSY) solution diluted on calcium chloride 0.05 molar solution.
Number | Date | Country | Kind |
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84-2005 | Jan 2005 | CL | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2006/050235 | 1/17/2006 | WO | 00 | 1/18/2008 |