Railway mail delivery – Projectors
Patent
1995-12-27
1997-06-24
Porta, David P.
Railway mail delivery
Projectors
250432R, G01J 300
Patent
active
056419660
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
Present invention relates to a method of measuring amounts/ of chemical compounds and quality parameters of chemical and physical character in waste water, process water, sea/lake-water etc. Examples of such quality parameters are amounts of nitrate, ammonium, orthophosphate, total nitrogen, total phosphorus and iron as well as chemical oxygen demand (COD) and turbidity. The present invention, furthermore, relates to a method of classification of aqueous suspensions. Data from known categories and classes of aqueous suspensions are thereby collected and analysed, after which unknown samples through measurements can be assigned to any or some of the known classes. Deviations from known class patterns can also be registered.
PRIOR ART
Certain amount and quality parameters are during purification of for example waste water by routine measured in order to monitor the effect of the various purification steps. A measurement of the amounts of nitrate and ammonium during the nitrification and denitrification steps is of a particularly great interest. Ammonium is during the nitrification step oxidised to nitrate by way of air being pumped through the water whereby air oxygen causes the oxidisation. Nitrate is during the denitrification step transformed into nitrogen in that enzymes from certain bacteria catalyze this transformation reaction. It is thereby required that the bacteria are allowed to work in a carbon high-energy environment, for example in a sludge containing organic carbon or in that such an environment is created by addition of for instance methanol or ethanol.
Off-line and on-line measurements of chemical and physical parameters are usually distinguished. Samples are in off-line measurements collected in receptacles thereto designed, often bottles or tubes. Accurately measured amounts of these collected samples are thereafter manually treated by the analytical chemist, thus taking care of filtering, addition of selective reagents, mixing, heating, transferring of the mixture to a detector cell, calculation of the amount by putting the reading in relation to previously performed calibrations and registration and reporting of the result. Certain parts of this chain of logistics can be subject to automation. In some automatic off-line analysers, the only thing the analyst has to do is to put the samples in a sample-changer, after which certain or all parts of aforementioned work chain are carried out automatically. Characterising for all off-line measurements is, however, that the collecting of samples per se and the transfer of these to an analyser/detector of any kind requires a human achievement. In on-line measurements, however, the method is temporarily or permanently linked to the detector in that a continuous supervision of various processing parameters is obtained. This supervision can be completely automated, i.e. without manual work elements.
Commercially available continuous indicators for nitrate and ammonium are often based on electrochemical measuring. Valid for nitrate is that the electromotive force (e.m.f) between a nitrate selective electrode and a reference electrode is registered. An example of the structure of a nitrate selective electrode having good selectivity properties is disclosed in the British Patent GB 1.565.988. The amount of nitrate in the sample solutions can be calculated by measuring e.m.f in a number of solutions having known amounts of nitrate followed by a measurement of the e.m.f in the sample solutions. This procedure is not without objections. The membrane of the nitrate selective electrode is sensitive to disruptions in the form of deposits and functional disorders resulting from chemical depletion caused by continuous stirring or a continuously passing stream of sample and standard solutions. Other in the sample matrix occurring anions, such as chloride, also interfere with the measurement, which must be compensated for during the calibration of the electrode system. The Swedish Patent SE 9003014-9 discloses a way and a device to overcome s
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Ross et al., "Potentiometric Gas Sensing Electrodes", Pure and Applied Chemistry, vol. 36, No. 4, 473-487, (1973). no month.
Thomas et al., "Ultraviolet multiwavelength absorptiometry (UVMA) for the examination of natural waters and wastewaters", Fresenius J. Anal. Chem., vol. 338, 234-237, 1990. no month.
Beemster et al., "On-line and In Situ Detection of Nitrates with Ultraviolet-Visible Absorption Spectrometry (UVAS)", American Water Works Association, Water Quality Technology Conference, Nov. 10-14, 1991.
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Karlberg Bo
Karlsson Mikael
Bruce David Vernon
Porta David P.
Tecator AB
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