DETERMINING THE ORGANIC CONTENT OF A FLUID

Abstract: The organic content is determined by: (a) reacting a sample of a fluid containing organic matter (such as viable biomass or soluble or insoluble organic compounds) with excess oxidising agent; (b) permitting enzyme catalysed release of oxygen from any unreacted oxidising agent; and (c) measuring the volume of oxygen liberated from the sample; wherein the volume of oxygen liberated provides a measure of the organic content of the fluid.

Description: Determining the Organic Content of a Fluid The present Invention is concerned with a method of determining the organic content (such as, for example, the biomass content) of a fluid; in particular the invention is concerned with a method of determining the organic content of a fluid which may be operated in a continuous process. Frequently, in industrial waste treatment, waste water treatment or in brewing plants or the like, an accurate measurement of the organic content of a fluid may be required so as to determine, for example, the treatment or filtration efficiency of the plant. Typically, any such measurements are taken only once during a working day, which is insufficient to identify fluctuating organic loads within the fluid, thus leading to inefficient treatment of the fluid due because of use of non- optimal conditions for treatment of the fluid. Furthermore, waste water of both domestic and industrial origin is frequently treated by a biological aerobic process which uses suspended micro-organisms (the activated sludge process) . The biomass concentration is an important parameter in maintaining effluent quality. It is generally measured off-line as dry weight. On-line probes based on, for example, turbidity, are generally unreliable and measure inert particles and dead cells. We have now developed a method of determining the organic content of a fluid, which can be used for organic compounds or for biomass, and which can provide more effective monitoring and process control and hence optimisation of the treatment process. Thus, according to the present invention there is provided a method of determining the content of organic matter of a fluid (generally an aqueous fluid) , which method comprises: (a) reacting a sample of the fluid with an oxidising agent; (b) permitting enzyme catalysed release of oxygen from unreacted oxidising agent; and (c) measuring the volume of oxygen liberated from the sample; wherein the volume of oxygen liberated provides a measure of the content of organic matter of the fluid. The volume may be measured as an absolute volume, or as a rate of evolution (in other words, the volume evolved in a unit time) . In one embodiment of the invention the method may be used to provide a measure of the living or viable biomass content of a fluid, such as for example, the content of active aerobic cells in a sample of fluid. Thus, advantageously, the method can be used to determine the amount of microbes present in, for example, aerobic biotreatment processes. In this embodiment the fluid may be subjected to chemical or physical treatment to disrupt the cells, either prior to, or co-incident with, step (a) ; it is not necessary for the oxidising agent to be in excess. In further embodiments (such as when the organic matter comprises soluble or insoluble organic compounds, such as hydrocarbons or cellulose present in the fluid) , the oxidising agent is present in excess relative to the organic matter. In this embodiment, the reaction of the sample with excess oxidising agent causes organic material contained in the fluid to be oxidised, and residual unreacted oxidising agent, when reacted with the enzyme, releases oxygen from the oxidising agent which may then be measured. The volume of oxygen liberated provides a measure of the content of organic matter of the fluid, because the volume of oxygen liberated is substantially inversely proportional to the volume of organic matter in the sample. In this embodiment of the invention, the method may be used to determine the organic content of a fluid, such as the organic load of effluent in, for example, waste water treatment plants or the like. In this embodiment, the resulting mixture from step (a) is contacted with an immobilised enzyme, capable of releasing oxygen from any unreacted oxidising agent. In this embodiment of the invention, the oxidising agent is, preferably, reacted with the sample of fluid separate from the immobilised enzyme for sufficient time to oxidise substantially all of the organic matter present. The sample of fluid is, preferably, acidified prior to reaction with the oxidising agent. Thus, advantageously, the fluid can be kept at a pH sufficient to inhibit activity of any micro-organisms present which may possess peroxidase activity. The sample may also be subjected to further treatment prior to oxidation, such as homogenisation, or heat treatment or both. The temperature of the process may be kept at a temperature not substantially less than biological temperature, or, alternatively, the fluid may be heated so as to further inhibit any peroxidase activity of micro-organisms, and also to increase the oxidising ability of the oxidising agent. Preferably the oxygen liberated may be measured using a pressure transducer or the like, such as a low-flow gas meter. Thus, the organic content of the sample at any given time may be determined, for example, in a continuous treatment process. Preferably the oxidising agent to be used in each of the embodiments is hydrogen peroxide, typically in liquid form, which advantageously, is easy to handle and relatively inexpensive for large industrial scale use. The amount of hydrogen peroxide to be used in the first embodiment (where the organic matter comprises non-viable organic compounds) , which hydrogen peroxide is in excess of the organic matter in the sample, may be determined using a feedback mechanism. The feedback mechanism may comprise reacting a sample of the fluid with hydrogen peroxide in the method according to the invention, and measuring the volume of oxygen liberated. Increasing amounts of hydrogen peroxide may be reacted with the sample until such time as oxygen is liberated following reaction with the enzyme; this is indicative of excess oxidising agent. Preferably, the enzyme used in each of the embodiments is a peroxidase or catalase. Thus, advantageously, where the method is used for determining viable or living biomass, the catalase is one naturally present in the cells. Preferably, the measurements by the gas meter of the oxygen liberated from the sample are passed to a data acquisition system for processing, where, advantageously, the information may be calibrated to produce an accurate reading of the organic matter present. The method according to the invention may be used in a wide range of industrial applications such as in waste water treatment or brewing. The method also allows continuous monitoring of micro¬ organisms present, in for example, aerobic biotreatment processes, or monitoring of receiving waters. The efficiency of a treatment process may be determined by monitoring the organic content of the fluid prior to the treatment process using the method according to the invention and comparing the readings obtained with readings of the organic content of the fluid obtained after the treatment process. Preferably, the data acquisition system provides for a feed-back mechanism to selectively control the treatment process, thus ensuring optimisation of the treatment conditions of the fluid. In one embodiment, substantially the whole process may be controlled by a microprocessor, or the like. Thus, advantageously, the treatment and monitoring processes may be automatic. Exemplary embodiments of the invention will be more clearly described with reference to the accompanying drawing by way of example only, wherein Figure 1 is a schematic diagram of one embodiment of the invention; Figure 2 is a schematic diagram of an alternative embodiment of the invention. Referring to Figure 1, there is illustrated a method of determining the organic content of a fluid which consists of adding to a pre-acidified fluid sample, an excess of oxidising hydrogen peroxide in a first mixing chamber and passing the fluid, containing residual hydrogen peroxide, to a chamber for reaction with an immobilised enzyme, such as a catalase or a peroxidase, in order to liberate the oxygen of the residual hydrogen peroxide. Measurements of the liberated oxygen are then taken by a low flow gas meter, and the information passed to a data acquisition system or microprocessor unit controlling the treatment process and which determines the organic load of the fluid sample. The microprocessor then ensures any necessary adjustments of the treatment conditions to be applied to the fluid to ensure optimum treatment conditions for the fluid which may contain a fluctuating organic load. Where the biomass content of a fluid is to be measured, the method used is that shown in Figure 2. A sample of the fluid is passed into a chamber where the integrity of the cells is disrupted. The cells then pass into another reaction chamber where a constant supply of hydrogen peroxide is introduced. Chemical or physical treatments can be used to disrupt the cells. This can be coincident with the hydrogen peroxide mixing stage or, as above, in a prior treatment step. The catalase which is naturally present in the aerobic cells catalyses the release of oxygen from the hydrogen peroxide added. The rate of flow of oxygen liberated represents a measurement of the viable aerobic or facultative biomass in the sample. Measurements of the liberated oxygen are taken by a low flow gas meter, as described above.

Claims: CLAZMS : 1. A method of determining the content of organic matter of a fluid, which method comprises: (a) reacting a sample of said fluid with an oxidising agent; (b) permitting enzyme catalysed release of oxygen from unreacted oxidising agent; and (c) measuring the volume of oxygen liberated from said sample; wherein the volume of oxygen liberated provides a measure of the organic content of said fluid. 2. A method according to claim 1, wherein said oxidising agent is present in an amount in excess relative to said organic matter. 3. A method according to claim 2, wherein said enzyme is immobilised, said release of oxygen being permitted by contacting the resulting mixture from step (a) with said immobilised enzyme. . A method according to any of claims l to 3, wherein said sample of fluid is acidified prior to reaction with said oxidising agent. 5. A method according to any of claims 1 to 4, wherein said sample of fluid is homogenised or heat treated, or both, prior to reaction with said oxidising agent. 6. A method according to any preceding claim, wherein step (a) is carried out for sufficient time to oxidise substantially all of said organic matter present in said sample of fluid. 7. A method according to any preceding claim, which further comprises accelerating the oxidation of said organic matter in step (a) . 8. A method according to claim 7, wherein said oxidation of said organic matter is accelerated by means of ultra-violet light, heating or addition of metal ions. 9. A method according to any preceding claim, wherein the amount of oxidising agent used is monitored by a feedback control mechanism. 10. A method according to claim 9, wherein said feedback control mechanism comprises reacting successively increasing amounts of said oxidising agent with said sample until oxygen has been liberated following reaction of said resulting mixture with said enzyme, which release of oxygen is monitored to provide an indication of excess oxidising agent. 11. A method according to claim 1, wherein the content of organic matter is the viable aerobic cell content of said fluid. 12. A method according to claim 11, which further comprises chemically or physically disrupting the integrity of said cells either prior to or coincident with step (a) . 13. A method according to claim 11 or 12, wherein said enzyme is one present in said cells. 14. A method according to any preceding claim, wherein said enzyme is a peroxidase or catalase. 15. A method according to any preceding claim, wherein said oxidising agent is hydrogen peroxide. 16. A method according to claim 15, wherein said hydrogen peroxide is provided as a liquid. 17. A method according to any preceding claim, which further comprises maintaining the reactants at a temperature not substantially less than biological temperature. 18. A method according to any preceding claim, wherein the oxygen liberated is measured using a pressure transducer. 19. A method according to claim 18, wherein said pressure transducer is a low-flow gas meter. 20. A method according to any preceding claim, wherein the measurements of said liberated oxygen are processed by means of a data acquisition system. 21. A method of monitoring the efficiency of a treatment process, which comprises monitoring the organic content of a fluid both before and after said treatment process using a method according to any of claims 1 to 20, and comparing the readings obtained. 22. A method according to claim 21, wherein a data acquisition system is used to provide a feedback mechanism for selectively control optimisation of the treatment conditions of said sampled fluid. 23. A method according to claim 21 or 22, which is controlled by a microprocessor.

Inventors: DINSDALE RICHARD MARK, HAWKES DENNIS, HAWKES FREDA, DINSDALE, RICHARD, MARK, HAWKES, DENNIS, HAWKES, FREDA
Applicants: DINSDALE RICHARD MARK, HAWKES DENNIS, HAWKES FREDA, UGCS UNIVERSITY OF GLAMORGAN C, DINSDALE, RICHARD, MARK, HAWKES, DENNIS, HAWKES, FREDA, UGCS (UNIVERSITY OF GLAMORGAN COMMERCIAL SERVICES
Application year: 1995
Main classification: G01N33
IPC codes: C12Q1