WO1998003855A1

WO1998003855A1 - Carbon monitoring system for water treatment and purification

Info

Publication number: WO1998003855A1
Application number: PCT/US1997/012927
Authority: WO
Inventors: Richard D. Godec
Original assignee: Sievers Instruments, Inc.; Petropavlovskikh, Viatcheslav A.
Priority date: 1996-07-05
Filing date: 1997-07-03
Publication date: 1998-01-29

Abstract

The present invention relates to an apparatus and process for determining the organic, inorganic, and total carbon content of water for use in water treatment and purification systems, and having special application in monitoring recycled water in a controlled human living environment, such as aboard a space station. The apparatus includes a first conversion device for sequentially converting all of the inorganic carbon in a water sample into carbon dioxide, and a second conversion device for converting all of the organic carbon in water sample into carbon dioxide; and first and second carbon dioxide detectors (38, 54) for determining the carbon dioxide content of such water sample at locations downstream of the first and second conversion devices (48, 52), respectively; where a conversion device can oxidize carbon products by ultraviolet light irradiation of water or by addition of oxidizing agents into water sample.

Description

CARBON MONITORING SYSTEM FOR WATER TREATMENT AND PURIFICATION

The present invention relates generally to an apparatus and process for monitoring the organic, inorganic, and total carbon content of water for use, for example, in water treatment and purification systems, and having special application in monitoring recycled water in a controlled human living environment, such as aboard a space station.

BACKGROUND OF THE INVENTION

In a controlled human living environment where there is little or no access to supplemental resources, such as aboard an orbiting space station, it is necessary to recycle waste water for reuse. Prior to reuse, waste water must be treated to remove impurities, particularly various organic contaminants. For example, in one common system, waste water is treated by passing it through a column or canister packed with an ion-exchange resin and/or various adsorbents. Such materials for this purpose are well known in the art.

For example, water recycling systems have been used by the Russians on their space stations Salyut and Mir since 1975. Water reclamation systems are also now being designed by the United States, Russia and other countries for the International Space

Stations (ISS). All of these systems currently remove organic contaminants from waste water with ion-exchange resins and adsorbents. The National Aeronautics and Space Administration (NASA) Johnson Space Center is responsible for establishing ISS water quality and monitoring requirements, and for providing in-flight monitoring to protect crew health.

To ensure that the capacity of such resins and adsorbents is not exhausted, thereby permitting undesirable, possibly even dangerous, contaminants to "break through" into the recycled water, it has been conventional practice to replace the resins and adsorbents frequently, usually well before these materials have been fully used. The result is incomplete and inefficient usage of the ion-exchange resins and adsorbents thereby increasing supply costs, labor requirements, and system disruptions. In addition, this inefficiency leads to additional materials requirements thereby adding cargo weight and taking up valuable space in a confined environment.

These and other problems with and limitations of the prior art could be addressed with a compact, light-weight, reliable, high-speed and high-precision analyzer capable of efficiently monitoring the organic, inorganic and total carbon content of recycled water emerging from the ion-exchange or similar purification treatment aboard a space vehicle or in a similar environment. Monitoring carbon content in space, for example, would enable complete, efficient use of the ion-exchange resins and adsorbents, minimizing resupply costs while simultaneously protecting the health of the crew. These resins and adsorbents could then be fully utilized until carbon content values, as measured by the analyzer, exceeded predetermined limits. At that point, the water purification chemicals would be replaced thereby maximizing the efficiency of this system. Apparatus and methods for measuring the carbon content of water samples in general are well known in the art. For example, U.S. Patent No. 5, 132,094, issued July 21, 1992, is directed to "Method and Apparatus for the Determination of Dissolved Carbon in Water. " An article entitled "New Technology of TOC Analysis in Water" by R. Godec et al. appears in Ultrapure Water. Vol. 9(10) at pp. 17-22 (Dec. 1992). Another article entitled "Recent Advances in the Measurement of Total Organic Carbon in Water" by R.

Hutte et al. appears in Proceedings of Microcontamination (San Jose, CA Sept. 21-23, 1993) at pp. 509-518.

None of the prior art in this field, however, adequately addresses the numerous difficulties and complications that arise when trying to carry out even simple, seemingly conventional analyses under the conditions of microgravity experienced in space.

Liquid/gas separation problems, fluid transport and storage requirements, and the need to avoid even the most minor of leakages and the resultant contamination in a low gravity environment render prior art methods and apparatus in this field essentially useless in a space station or comparable environment. The present invention results in a carbon analyzer of general application that can be used in any orientation with a high degree of safety in both common and many specialized applications. While the apparatus and process described herein has particular application aboard a space vehicle, it will be apparent to those skilled in the art that the apparatus and process of this invention, with various modifications, may also be useful in other applications, such as for land-based carbon monitoring systems.

OBJECTS OF THE INVENTION

Accordingly, a principal object of this invention is to provide a self-contained apparatus and related process for monitoring the organic ("OC"), inorganic ("IC"), and total carbon ("TC") content of water.

It is a specific object of this invention to provide an apparatus and process for monitoring the purity of water in various controlled living environments.

Another specific object of this invention is to provide a compact, light-weight, reliable, high-speed analyzer for monitoring the carbon content of recycled water aboard a space craft or in comparable environments.

Still another object of this invention is to provide a carbon analyzer suitable for operation under low-gravity conditions.

Yet another object of this invention is to provide a carbon analyzer with additional capabilities of monitoring the pH and conductivity of recycled water samples.

The most important objective is to provide a highly reliable, safe analyzer to measure OC, IC, TC, conductivity and pH in water, and for monitoring water treatment and purification systems.

Other objects and advantages of the present invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises, but is not limited to, the processes and related apparatus, involving the several steps and the various components, and the relation and order of one or more such steps and components with respect to each of the others, as exemplified by the following description and the accompanying drawings. Various modifications of and variations on the processes and apparatus as herein described will be apparent to those skilled in the art, and all such modifications and variations are considered within the scope of the invention.

SUMMARY OF THE INVENTION A carbon analyzer and a process for operating it have been developed for a Life

Sciences Risk Mitigation Flight Experiment to be conducted on upcoming space flights. The carbon analyzer of this invention measures Organic Carbon (OC), Inorganic Carbon (IC) and Total Carbon (TC). The analytical range for each of these parameters is from 1 to 50,000 μg/L. The analyzer's capabilities can be augmented to include measurement of pH (e.g. from 0 to 14 pH units) and conductivity (e.g. from 1 to 200 μmho/cm). Fluid handling and gas/liquid separation features required for enhanced reliability in microgravity have been incorporated into the design, along with features needed to satisfy the safety requirements of the joint U.SJRussian space program. An actual flight unit is projected to weigh 47 lb. , occupy a space of only 1.6 ft³, and consume only 41 W of electrical power. The analyzer is designed so that only simple analysis and maintenance procedures need to be performed while in orbit.

In one representative embodiment, the carbon monitoring system of this invention comprises in combination: (a) means for introducing a relatively small, measured, recycled water sample into the system; (b) means for converting inorganic carbon content in the water sample to carbon dioxide (CO₂); (c) means for sensing and measuring the carbon dioxide based on inorganic carbon in the water sample; (d) means for removing the carbon dioxide from inorganic carbon from the water sample; (e) means for converting organic carbon in the water sample to carbon dioxide; (f) means for sensing and measuring the carbon dioxide based on such organic carbon in the water sample; (g) means for recycling and reusing a predominant proportion of the materials used in connection with the carbon detection process; and (h) means for collecting a non-hazardous waste product that represents substantially only the volume of the water samples. In this embodiment, total carbon concentration (TC) is calculated by adding the inorganic and organic carbon concentrations as sensed and measured above.

In an alternative embodiment, the carbon monitoring system of this invention comprises means for bypassing the inorganic carbon removal means and, instead, directing the water sample from the IC sensing and measurement means directly to the means for converting organic carbon to carbon dioxide. In this embodiment, the second CO₂ sensing and measurement means will measure total carbon content (TC), and the organic carbon (OC) concentration will then be calculated by subtracting the inorganic carbon content from the total carbon (OC = TC - IC). In still other embodiments, the carbon monitoring system of this invention may comprise a pH sensor and/or a conductivity sensor positioned along a second water sample flow path running in parallel with the carbon sampling and measurement flow path of the apparatus.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1 is a schematic flow chart of a preferred embodiment of the carbon monitoring system of this invention.

Fig. 2 is a representative graph on a log-log scale illustrating the relationship between electrical conductivity and carbon content in a deionized water sample.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As shown in Fig. 1, carbon analyzer 10 according to this invention comprises a sample inlet system 12 which takes a calibrated water sample, for example from a 25 ml. syringe, and injects the sample into the carbon monitoring system at a controlled, continuous, optionally predeterminable variable flow rate using suitable pumping means, for example a syringe or peristaltic tubing pump. At a pump rate of 2.5 ml. /minute, for example, it would take 10 minutes to inject the full 25 ml. sample into the analyzer. Such pumping means may optionally be located at other appropriate locations, e.g. at exit flow line 22 in Fig. 1 , thereby drawing sample through the apparatus. Upon introduction into the analyzer system, the water sample or portion thereof may enter a 3-way valve 14, or similar fluid flow control means, for directing the sample along one of two internal flow paths through the analyzer, one being a referencing flow path, the other being a carbon-sensing flow path. The fluid flow paths through the analyzer are defined by fluid conduits of suitable dimensions and are made of a substantially inert material. Along a first, or referencing, fluid flow path 60 are located a conductivity sensor 16 and/or a pH sensor 18. Downstream from the conductivity and/or pH sensors along such first flow path, the sample may pass through another 3-way valve 20, or similar flow control means, where it is directed along an exit flow line 22 (which optionally comprises a back pressure regulator 24) to a waste collection reservoir 26.

Reservoir 26 holds the waste solution, consisting of sample water plus any reagents. Reservoir 26 is easily replaced when full. The waste solution is not generally hazardous because the acidity of such solution, optionally comprising one or more reagents as hereinafter described, can be neutralized with solid sodium bicarbonate or other acid acceptor added to each reservoir unit 26.

By way of example, during the first three minutes of the analysis sequence, the portion of the water sample introduced into the analyzer system can be directed along first conductivity and/or pH-sensing flow path 60. The temperature of the sample may be measured in or near either or both sensors 16 and 18, and the responses of the sensors then automatically adjusted to a reference temperature, e.g. 25 °C. This procedure provides a standardized reference point for comparing conductivity and/or pH readings for multiple water samples which may possibly be at differing temperatures over time.

Upon completion of the conductivity and/or pH measurements for referencing purposes, valve 14 may be switched to redirect another portion of the water sample along a second, or carbon-sensing, flow path 80 through the analyzer. Alternatively, in another embodiment of this invention, conductivity sensor 16 (and its associated temperature sensor if any) and/or pH sensor 18 (and its associated temperature sensor, if any) may optionally be located in line 80. Line 60 may then be, optionally, eliminated. At a mixer 28, or similar means, the water sample may be optionally mixed with one or more reagents supplied by means of one or more reagent pumps 30 from a reagents system 32 comprising, for example, reservoirs or supplies 34, 36 of first and second reagents respectively. One of said reagents may be a material, such as an acid or acidic solution, for converting inorganic carbon present in the water sample to carbon dioxide. Further, one of said reagents may be a material, such as oxygen or an oxidant, for converting organic carbon in the water sample to carbon dioxide.

In one embodiment of this invention, a first reagent stored, e.g. in reservoir 34 consists essentially of an acid or acidic solution, for example 6M phosphoric acid. With certain limitations, other strong, inorganic mineral acids, such as sulfuric acid, or solutions thereof, may be used as such reagent. Hydrochloric acid is normally not considered acceptable as such first reagent. Nitric acid on the other hand, may be used as such first reagent if it is cool and not sufficiently concentrated to cause premature oxidation of organic carbon in the water sample. Inorganic carbon in the water sample may be present in the form of CO₂, bicarbonate ions (HCO₃ ), and/or carbonate ions (CO₃ ²). The total concentration of carbon in these three forms is defined as inorganic carbon (IC) concentration. Through acidification, bicarbonate and carbonate ions are converted to CO₂ according to the following familiar chemical reactions:

(1 ) HCO.^" + H ^* == C0₂ + H₂ 0

(2) C0₃ + 2// ' tf. 2H₂0

The first dissociation constant of carbonic acid is, as is well known, about 4.45x10⁷ at 25°C, which means that at pH 6.35 about half of any free and combined CO₂ is present as free CO₂ and at pH 5.40 about 90% of any free and combined CO₂ is present as free CO₂. Hence, if the pH of the sample is less than about 6.3, it may not be necessary to contact the sample with any acidic material to promote the foregoing chemical reactions. After the water sample is optionally mixed with acidic reagent at a mixer or mixing junction 28, the mixed stream is directed into a first region of a first CO₂-detector means or carbon dioxide sensor 38. In a preferred embodiment of this invention, carbon dioxide sensor 38 comprises a membrane/conductivity-type CO₂ sensor comparable to that described in U.S. Patent No. 5,132,094, although other CO₂ sensing systems known in the art my be used. CO₂ sensor 38 may operate in conjunction with a supply 40 of deionized water operated in a closed-loop, regenerating system. Fresh deionized water is transferred from reservoir 40 into a second region of first sensor 38 via fluid outlet conduit 42, where it passes into contact with a suitable CO₂-ρermeable membrane 39, and back to reservoir 40 via fluid inlet conduit 44. Some of the CO₂ in the water sample introduced into first sensor 38 on the other side of such membrane is transferred to the deionized water loop via such membrane. The membrane allows CO₂ to pass, but passage of other gases and ions is inhibited. Once in the deionized water loop, CO₂ establishes equilibrium with hydrogen ions (H⁺) and HCO₃ , and the concentration of these ions is measured using, for example, a temperature-compensated conductivity cell or other sensor. The concentration of IC in the sample is then calculated from the conductivities measured with this cell. The deionized ("DI") water and the water sample (which may be optionally acidified) tend to come into equilibrium across the membrane with respect to free (i.e. , unionized) CO₂ not with respect to total free-and-ionized CO₂. The following table gives the amount of free CO₂ as percent of free and combined (total) CO₂ at selected pH's at 25 ° C.

%free CO, pϋ

50 6.35

10 5.40

1 4.36

0.1 3.35

In the DI water the pH is the natural pH of dissolved CO₂. The following table gives the conductivity and pH at 25 °C for various concentrations of total free-and- combined CO₂ in DI water. milligrams/liter %CO₂ conductivity total CO, ionized microSiemens/cm EH

0 100 0.0550 7.00

0.001 80.2 0.0574 6.96

0.01 68.5 0.0883 6.69

0.1 35.3 0.323 6.09

1 13.0 1.170 5.53

10 4.3 3.88 5.01

100 1.4 12.45 4.50

At equilibrium, as noted above, the free CO will attain the same vapor pressure (i.e. , essentially the same concentration) on both sides of the membrane. Such equilibrium may be established by flowing the DI water at a predetermined rate on one side of the membrane countercurrently to the flow of sample on the other side of such membrane, also at a predetermined rate. As understood by those of ordinary skill in the art, the appropriate flow rates depend on the lengths of the flow paths and the permeability of the membrane to CO₂. Such equilibrium may also be established by flowing the CO₂ containing sample on one side of the membrane against a non-flowing volume of DI water on the other side of the membrane. Periodically, e.g. every few minutes, the DI water is pulsed out (flushed out) with fresh DI water through a conductivity sensor. The peak conductivity compared to the base conductivity (see table above) may be used as a measure of ionized CO₂. Alternatively, the integrated area of conductivity (optimally corrected for base line conductivity, e.g. 0.0550 micro-Siemens/cm) by time or volume of flow may be used for such measure.

When the actual conductivity of the DI water has been measured, the table above may be used for determining carbon content by immediately giving milligrams per liter total CO₂, which may then be converted to milligrams C per liter by multiplying by 0.273. Fig. 2 plots milligrams C/liter versus conductivity on a log-log scale (i.e. to the base 10) and may be used to readily convert measured conductivities, corrected to 25 °C, to mg/1 C. Similar tables and graphs may be constructed for any desired temperature or the data can be corrected to a standard temperature, e.g. 25 °C.

The conductivity sensor does not generally give microSiemens/cm directly unless the sensor per se is designed to do so. Instead, generally, the ratio of current measured to voltage measured must be corrected by a so-called "cell constant. " Further, it is not generally practical to allow the DI water to reach absolute equilibrium with the solution. However, at a given temperature and at predetermined, reproducible contact times by the sample stream and the DI water with the membrane, the degree of approach to equilibrium will be reproducible. One may correct the above table and Fig. 2 by analyzing one or more known samples. Alternatively one may construct conversion tables, conversion graphs, or algorithms representing either solely or in substantial part analyses of a plurality of known samples.

The following procedure is representative: A. establishing one or more conversion tables, conversion graphs, or algorithms for predetermined contact times of sample stream and a DI water stream with a given CO₂-permeable membrane;

B. contacting a sample stream and a DI water stream with said membrane for said predetermined contact times; C. measuring the concentration of carbon dioxide which has permeated the membrane and optionally measuring the temperature or controlling the temperature to a predetermined value;

D. from the established conversion table(s), graph(s), and/or algorithm(s), determining the concentration of carbon and/or carbon dioxide in the sample stream; and, E. from time to time re-establishing such conversion table(s), graph(s), and/or algorithms or determining one or more correction factors for such table(s), graph(s), and/or algorithm(s) with the aid of one or more samples having known concentrations of carbon and/or carbon dioxide.

Although if is preferred to measure the concentration of carbon dioxide which has permeated the membrane by absorbing such CO₂ in DI water and measuring the conductance or resistance of such DI water by direct contact with micro-electrodes, other means of measuring such permeated CO₂ may be used. For example, the concentration of CO₂ in such DI water may be measured by electrode-less means, e.g. by using a capacitor or coil which is part of a radio-frequency resonant circuit. As shown by the table above, pH measurements reflect CO₂ concentration. The latter may also be measured with CO₂ or bicarbonate specific electrodes, e.g. the anion exchange micro-electrodes described in U.S. Patent Nos. 5,141,717 and 3,558,279, incorporated herein in their entirety.

The CO₂ which permeates the membrane may also be allowed to accumulate in a gas phase instead of in DI water. The concentration of CO , may then be measured by infrared absorption or by an ion specific electrode, either continuously or on a pulsed basis. The gas phase may also contain air (including CO₂-free air) or other appropriate gas, or the CO₂ permeating the membrane may be continuously or periodically swept out by a vacuum.

A preferred membrane at this time comprises a copolymer of tetrafluoroethylene and a perfluoroalkyl vinyl ether available from du Pont (Wilmington DE, U.S.A.) under the tradename Teflon PFA. Depending on the details of the application and the apparatus, other membranes may be useful . The permeability (in Barrers) to CO₂ of some alternative membranes are listed below:

Polytrimethylsilylpropyne 93,100 Silicone rubber (polydimethylsiloxane) 3,200

Natural rubber 130

Polystyrene 11

Polycarbonate (Lexan, TM General Electric Co.) 10

Poly ether sulfone 7.4 Cellulose Acetate 6.0

Poly sulfone 4.4

Polyetherimide (Ultem, TM General Electric Co.) 1.5 Polyimide (Kapton, TM du Pont Co.) 0.2

Polyamide (Nylon 6) 0.16 PVC 0.16 (A "Barrer" is 10^'10 ml per cm² area per second per cm Hg pressure difference per cm of membrane thickness). In the absence of interfering permeants, membranes having a high CO₂ permeation rate permit very compact sensor or sensors having a very rapid response time, limited by the diffusion through any stagnant or laminar flow liquid regions at the membrane-liquid interfaces. If interfering permeants may be present, then a membrane having good selectivity for CO₂ versus the interfering permeant may be desirable even if such membrane has a comparatively low CO₂ permeability.

The above discussion has been directed to the measurement of inorganic carbon, e.g. free and combined CO₂, but it obviously applies equally well to the determination of Total Carbon ("TC") and/or organic carbon ("OC") resulting from the conversion of carbon in organic compounds to free and combined CO₂, all as discussed more fully below.

The deionized water used in first sensor 38 is provided by deionized water supply 40, which, for example, recycles water through a small mixed-bed ion-exchange resin 70 utilizing suitable pumping means 72. Such mixed bed ion-exchange resins are conventional and well known in the art, as are suitable pumping means. Such ion-exchange resin continually removes HCO₃ and other ions from the water (except those resulting from the intrinsic dissociation of water) thereby maintaining the purity of the water in the closed loop. The useful life of the resin under normal expected operating conditions may be, for example, about five years. In other embodiments of this invention, the conductivity of the deionized water leaving CO₂ sensor 38 may be determined by electrode-less means well known in the art. Alternatively, the deionized water loop may be replaced by an appropriate gas, e.g. air or nitrogen, and the concentration of CO₂ diffusing across the permeable membrane measured by absorption of infrared radiation. Sensor 38 may instead be a CO₂ specific electrode. In one embodiment of this invention, the water sample leaving first carbon dioxide sensor 38 passes through a 3-way valve 46, or similar means, and is then directed to a carbon dioxide removal module 48 for removing CO₂ from the sample, for example utilizing technology similar to that described in U.S. Patent No. 5,132,094. In a preferred embodiment, the carbon dioxide removal module (ICR) 48 comprises microporous, hollow fibers contained in a sealed vacuum degasser made from polypropylene, Teflon^®, polysulfone or other suitable materials. The ICR may have a shell and tube configuration.

Emerging from module 48, the water sample may pass through yet another mixer or mixing junction 50, or similar means, where it is mixed with a suitable quantity of a second reagent, e.g. an oxidation agent, pumped by reagent pump means 30 from reagent reservoir or supply 36. Such second reagent may comprise a material that promotes or causes the oxidation of organic carbon in the water sample, at least under certain process conditions. In a preferred embodiment, such second or oxidizing reagent consists essentially of an aqueous solution of ammonium persulfate ((NH₄)₂S₂O₈). Alternative possible oxidizing agents for use as such second reagent include other inorganic persulfates, such as sodium persulfate (Na₂S₂O₈), potassium persulfate, dissolved oxygen (O₂), ozone (O₃), hydrogen peroxide, inorganic peroxy compounds, and/or dichromate salts. The oxygen, ozone and/or hydrogen peroxide may be made in situ by means well known in the art. The oxidation of organic carbon in the water sample to CO₂ by such oxidizing agent may further be promoted by irradiating the mixture with ultraviolet (UV) light, for example as the sample passes through oxygenation reactor 52 in a quartz or similar UV-transmitting coil. Means other than UV light may be used to promote the oxidation of organic carbon in the sample. For example, heat, certain catalysts such as silver ions (Ag ⁺), or platinum wool, or any combination thereof may also be useful for this purpose. The source of UV light may be a low or medium pressure mercury arc lamp, a doped mercury arc lamp, a coherent or non-coherent Xenon or doped Xenon excimer lamp, for example.

By way of example, if organic carbon is present in the water sample in the form of methanol (CH₃OH), when persulfate is added to the sample and the reaction is initiated by UV light in reactor 52, the following chemical reactions occur:

(3) CH₃OH + S₂O_t ² + H₂0 -» C0₂ + 6HSO (4) CH₃OH 60H' CO„ + SH₂0

The OH* radical is formed by the decomposition of S₂O_g ² or by the photolysis of water or dissolved oxygen. OH* is a powerful oxidant having a very short half-life in water. Similar reactions convert other common organic carbon compounds found in water to carbon dioxide and very small quantities of harmless byproducts. The role of UV in the above reactions is that the energy from UV light appears to result in the formation of hydroxy radicals (OH«) and other active products from the photolysis of oxygen, water and persulfate ion. The hydroxy radicals and other active products then completely oxidize organic compounds to form CO₂, as shown in equation (4) above. Alternatively, where the concentration of organic carbon in the sample is relatively low, for example on the order of about 1 ,000 μg/L or less, it may be possible to eliminate the oxidizing agent completely and rely solely on UV radiation of the sample, such as in reactor 52, to initiate the oxidation of organic carbon compounds to CO₂. The advantages of such an embodiment are simplicity, reduced use of oxidizing reagent, and even lower concentrations of byproducts in the effluent waste stream.

Suitable sources of UV include low-pressure, medium pressure and high pressure mercury arc lamps; doped mercury arc lamps; incoherent or coherent excimer lamps, e.g. Xenon (172 nm), Argon chloride (175 nm), Argon fluoride (193 nm), Krypton chloride (222) and Krypton fluoride ( 249 nm); and other gas discharge lamps. It is preferred if such sources include a substantial amount of radiation within the range 160 to 260 nm.

On leaving reactor 52, the water sample may be directed into a first region of a second CO₂-detector means or carbon dioxide sensor 54, which may also comprise a membrane/conductivity detection unit or other detection technology as described above for sensor 38. Similarly to sensor 38, sensor 54 may operate in conjunction with a deionized water supply, such as supply 40, operated as a closed-loop, regenerating system. Fresh deionized water is transferred from reservoir 40 into a second region of sensor 54 via fluid outlet conduit 56, where it passes into contact with a selective membrane in sensor 54, and then flows back to reservoir 40 via fluid inlet conduit 58. The water returning to reservoir 40 may be recycled through a mixed-bed ion-exchange resin 70, as previously described, to remove any bicarbonate or other ions and thereby restore this water to a pure, deionized state. Similarly to the operation of CO₂ sensor 38 in connection with measuring IC, CO₂ sensor 54 may measure conductivity from which the concentration of OC in the sample may be calculated. Total carbon concentration in the sample is then calculated by summing the inorganic and organic carbon (TC=IC + OC). In certain particularly preferred embodiments of this invention, oxidizing agent addition, UV irradiation, temperature control and flow rate regulation may be carried out in predetermined programs, while holding other system parameters constant, for purposes of referencing results and/or optimizing performance. Thus, in one such embodiment, one or more oxidizing agents are added to samples in a predeterminable addition program over time of amounts of the oxidizing agents relative to a predetermined volumetric flow rate of the sample, the addition program including at least one amount of the oxidizing agents which is less than that which is sufficient to oxidize all of the organic carbon in the sample to oxidized carbon products and also including at least one other amount which is greater than that which is sufficient to oxidize all of the organic carbon to oxidized carbon products In another such embodiment, the UV irradiation of samples is carried out in a predetermined irradiation program over time of ultraviolet light intensities relative to a predetermined volumetric flow rate of the sample, the irradiation program including at least one intensity which is less than that which is sufficient to oxidize all of the organic carbon in the sample to oxidized carbon products and also including at least one other intensity which is greater than that which is sufficient to oxidize all of the organic carbon to oxidized carbon products.

In a third such embodiment, using a combination of oxidizing agent and UV irradiation, one or more oxidizing agents are added to samples in a predeterminable amount of said oxidizing agent relative to a predetermined volumetric flow rate of the sample while also irradiating the sample within the reactor system with a source of ultraviolet light in a predeterminable irradiation program over time of ultraviolet light intensities relative to the predetermined volumetric flow rate of the sample, the irradiation program including at least one intensity which is less than that intensity which is sufficient to oxidize all of the organic carbon in the sample to oxidized carbon products and also including at least one other intensity which is greater than that which is sufficient to oxidize all of the organic carbon to oxidized carbon products.

In a fourth such embodiment, one or more oxidizing agents are added to samples in a predeterminable amount of said oxidizing agent relative to a predetermined volumetric flow rate of the sample, while controlling the temperature of the sample within the reactor system to a predeterminable temperature program over time, said temperature program including at least one temperature which is less than that which is sufficient to oxidize all of the organic carbon in the sample to oxidized carbon products and also including at least one other temperature which is greater than that which is sufficient to oxidize all of the organic carbon to oxidized carbon products. In still a fifth such embodiment, one or more oxidizing agents are added to samples at a predeterminable constant rate over time, while also irradiating the sample within the reactor system with a source of ultraviolet light at a pedetermined intensity of ultraviolet light constant over time and varying the volumetric flow rate of the sample according to a predeterminable flow rate program over time, said flow rate program including at least one flow rate which is greater than that flow rate which is sufficient to oxidize all of the organic carbon in the sample to oxidized carbon products and also including at least one other flow rate which is less than that flow rate which is sufficient to oxidize all of the organic carbon to oxidized carbon products.

The several foregoing procedures for varying certain system parameters according to a predetermined pattern or program, which may be automated and computer-controlled, can be utilized individually or in two or more combinations as deemed appropriate.

On leaving CO₂ sensor 54, the water sample, now perhaps contaminated with very small amounts of acid (from the optional acidification step) and very small amounts of oxidation byproducts (from the optional oxidation step), passes through T-junction 20, from which it is directed through optional back pressure regulator 24 to optional waste collection reservoir 26. Back pressure regulator 24 is set to maintain the water sample in the fluid system at a predetermined pressure, such as 15 psig. Waste collection reservoir 26 may be of any desired size, consistent with minimizing the overall size of the carbon analyzer, but optimally it may be sized to contain waste samples from about ten analyses, i.e. with 25 ml. samples, reservoir 26 may be large enough to contain at least 250 ml. of fluid.

In an alternative embodiment of this invention, also illustrated in Fig. 1, under certain conditions it may be desirable to completely bypass the carbon removal module 48 and instead to direct the water sample from valve 46 to mixer 50 through another fluid conduit, such as conduit 47. In such embodiment, it will be apparent to those skilled in the art that a second reagent can be added to the water sample at any point along the flow path defined by conduit 47 between valve 46 (even valve 14) and reactor 52. It has been determined that using the ICR 48 for removing CO₂ from the sample will lead to more accurate results when the ratio of OC:IC concentrations is about 0.1 or less (i.e. relatively low OC concentrations). More particularly, it has been found that when the ratio of OC:IC is 0.1 or less, the removal of CO₂ from inorganic sources prior to measuring for organic carbon makes it possible to measure OC concentration with an accuracy of ±5% utilizing the carbon analyzer of this invention.

On the other hand, when the OC:IC ratio is greater than 0.1 (i.e. relatively high OC concentrations), the accuracy of the OC measurement is maximized by bypassing ICR module 48. The explanation for this phenomenon appears to be that the ICR 48 may introduce a small amount of organics into the sample (on the order of 1 to 5 -.g/L), and the effect of this addition on the analytical results is avoided by bypassing the ICR when it is not really needed. When the OC:IC ratio is greater than 0.1 and the ICR 48 is bypassed, the second

CO₂ sensor 54 will now be measuring the total carbon concentration TC. In this case, organic carbon in the sample is calculated by subtracting the inorganic from the total carbon concentration (OC = TC-IC).

The apparatus as described above is compact, light weight, and adapted to meet the rigorous and unusual requirements of conditions aboard a space vehicle. Fluid handling and gas/liquid separation features required for enhanced reliability under microgravity conditions may be incorporated in the system design. For example, the system, including all fluid reservoirs, may be fully sealed and pressurized. The novel design of this apparatus fully satisfies the current safety requirements of the joint U.SJRussian space program.

More particularly, special safety features may be incorporated into the apparatus of this invention to ensure that the various reagents remain contained inside the analyzer. Protection against overpressunzation of the sample stream and deionized water loop can be provided, along with protections against electrical shocks, glass particulates, sparking and fires. For example, containment of possibly hazardous liquids used in the analyzer can be ensured by such precautions as using triple containment of the reagents, rendering the waste solution in reservoir 26 nonhazardous by the addition of sodium bicarbonate or other acid acceptors to neutralize acid, and providing for leak detection at key points such as the ICR module 48. Protection against overpressunzation can be attained through proper design and use of a back pressure regulator 24, use of pressure sensors at key locations, and computerized shut-down of the system when necessary. These and other similar safety feature may be incorporated into the apparatus as desired.

Reliable operation of a carbon analyzer under microgravity conditions requires, at a minimum, three key features: gas bubbles must be removed from the liquid sample; gases must be separated from the deionized water; and the deionized water must be efficiently circulated in closed loops through the CO₂ sensors. Gas bubble removal from the water sample can be achieved at the sample inlet stage by means of an in-situ gas separator in the sample syringe. Once the sample is injected into the analyzer system, constant sample stream pressurization maintains liquid-vapor equilibrium. Gas separation from the deionized water may be achieved by initially degassing the deionized water and thereafter maintaining it at substantially constant pressure. Efficient circulation of the deionized water may be achieved by means of positive displacement gear pumps or peristaltic pumps. The carbon analyzer of this invention may be specifically designed for reliable operation under the following ranges of operating conditions, which correspond to observed and anticipated conditions aboard a space station:

Operating Environmental Data

Temperature, °C 5 to 40

Relatively humidity, % 10 to 80 (noncondensing) and

95 (noncondensing) for 3 hr/day Atmospheric composition, % Oxygen up to 40 (350 mm Hg maximum partial pressure)

Carbon dioxide 3 (max.)

Pressure, mm Hg 450 to 970

Supply voltage, VDC 27.5 (Nominal)

Mir potable water characteristics Free gas, %(V/V) 5 (max.)

OC, μg/L 1,300 to 6,800

IC, μg/L 5,000 to 32,000

TC, /xg/L 6,500 to 37,500

OC:IC Ratio 0.04 to 0.56 pH 6.8 to 8.0

Conductivity, μmho/cm 36 to 182

Non-ooeratine Environmental Data Temperature, °C 5 to 40

Pressure, mm Hg 5 to 970 (for up to 24 hr) Pressure change rate, mm Hg/min -30 to +30

Example A carbon analyzer in accordance with this invention was prepared and tested to demonstrate performance relative to established requirements for a number of parameters. Table 1 below summarizes the results of these tests:

TABLE 1 - REQUIREMENTS AND DEMONSTRATED PERFORMANCE Parameter Requirement Demonstrated Performance

Mission Duration, days 90+ 365 Number of analyses 37 140 Types of samples Recycled potable water, Satisfies requirement ground-test samples

Analytical OC, μg/L 1 to 50,000± 15μg/L or Satisfies requirement

5%

IC.μg/L 1 to 50,000± 15μg/L or Satisfies requirement

5%

TC,μg/L 1 to 50,000± 15μg/L or Satisfies requirement

5 %

PH O to 14 ±0.1 Satisfies requirement Conductivity, μmho/cm 1 to 200 at 25°C ±0.2 or 5% Satisfies requirement Sample volume, mi- 50 (maximum) 25 Analysis time, min. 30 (maximum) Satisfies requirement No. of calib. standards Not specified 2

Calibration time, min. 45 (maximum) 30 Data storage capacity 370 analyses (on RAM card) 3,200 Data downloading via RS-232 port Satisfies requirement Physical Weight, lb. 54 (maximum) 47

Dimensions, in. (HxWxD) 8.9x19.3x16.3 (maximum) Satisfies requirement Volume, ft³ 1.6 (maximum) Satisfies requirement Electrical Power consumption, W 120 (maximum) 41

Standby power, W 0 Satisfies requirement

Acoustic noise, dB 60 (maximum) 58

In still another embodiment of this invention, carbon monitoring of recycled water utilizing the carbon analyzer as described above may be integrated with a computerized data storage, processing and retrieval system. For example, data obtained during a flight experiment can be stored on a Flash RAM card in the analyzer. This card has for example a capacity of 4 megabytes, and may store data in triplicate to minimize the chance of losing data because of damage to the RAM card by cosmic radiation in orbit. The three copies of the data may be in different locations on the RAM card, and the analyzer may automatically compare the copies when the data are downloaded. Such comparison ensures that the downloaded data are undamaged because each data point must match the corresponding information in at least one other copy. In the unlikely event that no match exists (i.e. , the same data point in at least two of the copies was damaged), then the analyzer may flag that data point as being faulty. Data can be downloaded from the RAM card for example through an RS-232 port, or the RAM card can be removed and transported to the ground.

It has further been found that the carbon monitoring system of this invention lends itself to a variety of improvements and enhancements which improve speed of operation, efficiency, accuracy, safety and/or other operating parameters.

For example, in one embodiment of the invention as described above, persulfate is used to oxidize organic carbon in the sample. The flow rate of the persulfate reagent solution can be selected by the operator before the analysis, based on information or prediction about the concentration of organics in the water sample. If the persulfate flow rate is too low, however, the organics may not be completely oxidized in reactor 52, resulting in low OC measurements in sensor 54. If the persulfate flow rate is too high, on the other hand, then excessive oxygen is produced in the UV reactor, and these bubbles may create "noise" (and erroneous readings) in OC sensor 54, and may require the operator to perform a maintenance procedure to eliminate the bubbles. Obviously, in this mode of operation, the operator must know or be able to predict something about the sample, and if every sample is different (as might be the case when the samples are in an autosampler), a considerable amount of operator time may be required for making the flow rate adjustments of the oxidizing agent or the sample. Furthermore, the concentration of organics may change without the operator's knowledge, potentially causing an analyzer failure or analysis errors.

An alternative mode of operation is to analyze each sample several, e.g. four, times. The first measurement may be called a "preliminary measurement. " It may be performed while the previous sample is being flushed out of the analyzer with new sample. Based on the OC value obtained during such preliminary measurement, the flow rate of persulfate or the sample is adjusted for the three "analytical measurements" . Other than the first flow rate, the remaining three choices may be linear ramps of flow rate up or down with respect to time. Because the persulfate or sample flow is ramped, it can accommodate a range of TOC concentrations, rather than just a single concentration or narrow band of concentrations. As a result, the analyzer correctly selects the proper persulfate or sample flow rate, based on the composition of each sample. Since such ramp procedure may be automated, it can be performed while the analyzer is unattended, and is not susceptible to human error. Therefore, operating and maintenance labor may be reduced, and the accuracy of the obtained data has the potential of being enhanced. In such mode, OC concentration reported by the analyzer for that sample may not necessarily be the average of the three analytical measurements. Instead, the results of the three analyses may undergo statistical evaluation by the analyzer's software so that if one of the three measurements is invalid because of noise, a bubble or any other reason, it may be rejected, and the other two measurements averaged. In the case of a continuously flowing sample stream, the variables contributing to the extent of oxidation of organics in the sample are: rate of flow of the sample stream; rate or amount of oxidant added relative to flow rate and oxygen demand of the organics and other reducing agents in the sample stream; and, intensity of UV radiation. Any or all of such variables can be varied in a pattern to give information on under-oxidation, complete oxidation and/or over-oxidation. Although it is convenient to ramp up or down one of these variables continuously or in discrete steps, the values of a variable may be selected in any order, even a random order. The analyzer's data processor may then, for example, consider the OC (or TC) measurement as a function of decreasing sample flow rate, or increasing oxidizer flow rate; or increasing UV intensity, selecting the maximum value of OC (or TC) found or averaging high values, which are within a predeterminable difference from each other, e.g. 5% . Preferably the data processor is programmed to accept a maximum value as the "true" value only if values before and after are smaller or equal within some predeterminable difference, e.g. 5%. If such is not the case, then the function of OC (or TC) versus decreasing sample flow rate, increasing oxidant flow rate, increasing UV intensity may still be increasing and an increment in such independent variables might have resulted in a higher OC (or TC) value. The date processor may obviously be programmed to flag "maximum" values in which the adjacent values are not smaller or equal. The data processor may be programmed to fit a suitable curve to the data, based on historical experience and interpolate or extrapolate a maximum value of OC (or TC).

Still another optional enhancement of the carbon monitoring system of this invention pertains to an improvement in the step of promoting the oxidation of organic carbon in the sample to CO₂ by exposure to UV light. One common technique for doing so is to use a mercury vapor lamp to produce UV radiation. But, in applications where the presence of mercury may be considered a potential health hazard, the use of mercury-free sources of

UV light may be desirable. Most of the light emitted by the mercury vapor lamp is at the wavelength of 254 nm, a relatively low energy. More UV light can be obtained by using some conventional, high-intensity lamps, but they generate excessive heat which must be eliminated from the analyzer. In an alternative embodiment of this invention, the analyzer utilizes a Xenon excimer lamp that efficiently generates UV light at a peak emission at 172 nm, and provides considerably more energy than is obtainable with the mercury lamp. The intensity of the emission can be changed by changing the gas pressure and current applied to the lamp. The wavelength can be changed by changing the composition of the gas(es) inside the lamp. The lamp may be integrated with the housing of oxidation reactor 52 and the quartz or other UV permeable coil that contains the sample.

Conventional membrane/conductivity detection technology sometimes permits bubbles of gas to pass through the membrane in the transfer module and enter the deionized water that circulates through the conductivity sensor used to measure CO₂. When this happens the analyzer produces incorrect measurements. It is a possible maintenance task for the operator to open the analyzer, disconnect the tubing from the transfer module, and allow the bubble to be dislodged by the pressure of the deionized water circulating through the opened tubing. Instead, the dislodging of bubbles can be automated requiring no operator action.

Such maintenance action can be performed in a preactive manner as a form of preventive maintenance; thus, incorrect measurements may be avoided and no analysis time is wasted. By inserting a three-way valve in the deionized water supply, water coming from the conductivity sensors enters the valve, and is directed to one of two locations in such supply. These locations differ in the pressure drop that is applied to the transfer module and conductivity sensor, depending upon the sizing of two restrictors. In the normal position, only 1 psid is applied across the transfer modules and conductivity sensors, for example. In the alternative position, the pressure differential may be increased to, for example, 20 psid, enough to force any bubbles out of the transfer module and conductivity sensor. The valve may be put in this second position when a new sample is introduced into the analyzer, and/or just before the final measurements are made during that analysis.

Gas bubbles may occur in a liquid sample at the syringe or other pumping means used to inject the samples into the analyzer. The presence of bubbles may cause measurement errors because the bubbles change the flow rate and/or the pressure of the liquid, or of the concentration of oxidant or acid in the sample. By capturing the bubbles inside the syringe or other pumping means, the accuracy and precision of the measurements made by the analyzer can be improved.

The capturing of bubbles inside a syringe can be accomplished utilizing a screen or hydrophilic microporous membrane at the outlet. The screen or membrane retains gas bubbles so they do not leave the syringe as the sample is dispensed. It has been found that such improved design results in a reliable and efficient means of separating bubbles from liquids, especially in the microgravity of space. This improvement eliminates the need for exceptionally complex hardware that would be required if it were not used.

Key components of the carbon removal module may be a vacuum degasser, containing for example a bundle of CO₂ permeable hollow fibers. The acidified sample solution flows over one surface of the hollow fibers, and carbon dioxide exits the solution through the fibers. The permeable carbon dioxide may be swept away from the fibers by a stream of purified air or by a vacuum. Sample stream pressurization may be used to reduce the size of any bubbles that may exist in the sample, increasing the likelihood that they will be swept out of the analyzer, and reducing the chance that they may be caught in locations where they could cause measurement errors. In the rare event that such hollow fibers might fail, sample solution could leak into the air or vacuum space resulting in erroneous data or damage to the analyzer hardware. In the usual technology, there is no means to automatically detect such a failure. In accordance with one embodiment of the invention, the module includes a simple, inexpensive sensor to detect such a failure. The analyzer's software monitors the output of such sensor, and, when a failure is detected, the operator receives a warning message. In addition, the vacuum degasser may be automatically bypassed so that the leak is prevented, while still allowing data to be acquired by the analyzer. The operating principle of this sensor is detection of increase in the conductivity due to any liquid in the air or vacuum stream. Under normal circumstances, the air or vacuum stream may contain a small amount of condensate having a low conductivity. When the hollow fibers leak, however, the liquid becomes highly conducting because the liquid contains acid and oxidizing agent. Preferably the hollow-fibers are operated with a pressure gradually extending from the outside to the inside of the fibers. In the event of occurrence of a weak or weakened spot in a fiber, the fiber will collapse upon itself safely sealing off such spot.

Other improvements in the carbon monitoring system of this invention relate to the storage of the acid and oxidizing agent reagents. Some reagents used in analytical instruments are not stable when dissolved in water. Solution of these reagents can be stored for limited periods of time before they are used in the instruments, and while they are in the instruments. Such limitation increases labor costs because of the need for frequent replacement of the solutions and for monitoring the age of solutions. Costs are increased because of the need for replacement of solutions when they become too old, even though they may have never been used. Such also increases the environmental burden of disposing of the un-used chemicals.

A prior solution to this problem has been to use as oxidizing reagent a 15% (W/V) solution of ammonium persulfate. This solution has, however, a shelf life of about 90 days. Since the analyzer may not be used for extended periods, and the cost of replacing the reagent is high, the improvement incorporates a device when may be called a Reagent System, in which there are a plurality of bags (e.g. , four) of dry persulfate crystals (which have an indefinitely long shelf life). Each bag may contain sufficient crystals to make enough solution for 90 days of operation. Therefore, the improved Reagent System can operate for several 90-day periods (e.g., four) before it must be maintained. Water that is to be mixed with the crystals is contained in a number of syringes 37, one for each bag of crystals. A mechanism is provided for mixing the water with the crystals when necessary, and for directing the resulting solution into the analyzer.

The ammonium and sodium salts of persulfate are very soluble in water, e.g. respectively about 580 grams per 1000 grams water at 0 °C, and 550 grams per 1000 ml solution at 20°C. Therefore, for example, to make about a 15% solution of either salt, about 5.7 ml of water must be added to such bag for each gram of dry persulfate salt in the bag and the mixture agitated or allowed to stand until an essentially homogeneous solution is obtained. On the other hand, potassium persulfate is soluble only to the extent of about 53 grams per 1000 water at 20 °C. Therefore, in this case, it is sufficient to flow water more or less continuously through such salt in such bag with adequate contact time to obtain a substantially saturated solution having about 5 % persulfate salt.

In the present state-of-the-art for carbon monitoring, persulfate and phosphoric acid reagents are contained in bags. The bags are mounted in plastic boxes which are used to ship the reagents in the bags to analyzers around the world. The microporous Teflon^® bags commonly used to hold the persulfate reagent have been found to be subject to breakage during shipment. Tests of such bags have shown that when a filled bag (inside a plastic box over packed in a cardboard box) is dropped a distance of six to nine feet, the bag often breaks at the seam at the bottom of the bag. There also are typically seams at the two edges of the bag, and these sometimes also break. It is desirable to reduce or eliminate this breakage. According to this aspect of the invention, the bag is reconfigured so that the seam that normally is at the bottom of the bag is relocated to the middle The hard plastic box which contains the bag supports the seam in this position, so the bag does not break when dropped, even 12 ft. The other two seams are also supported by the plastic box when the bag is made somewhat wider than the old-style bag. Twelve bags made using the new approach were drop tested extensively and did not break, regardless of the number of drops experienced.

Any reagents used in the analyzer of this invention must not contribute significant amounts of IC and/or OC to the analyses. Further, such reagents must not extract from, or produce from, the reagent storage containers and associated conduits significant amounts of IC and/or OC. For persulfate solids and solutions, Teflon TFE, FEP or PFA (du Pont Co., Wilmington, DE, U.S.A.) are preferred for direct contact. Equivalent products from other suppliers may be substituted. Also suitable are Viton A (polyvinylidene fluoride-co- hexafluoropropylene); Viton B or G (polyvinylidene fluoride-co-hexafloropropylene-co- tetrafluoroethylene); Viton GLT (polyvinylidene fluoride-co-tetra fluoroefhylene-co- perfluoromethylvinyl ether); Kalrez (polytetrafluoroethylene-co-perfluoromethylvinyl ether); all available from du Pont Co., Wilmington, DE, U.S.A. and equivalent products from other suppliers.

Also, suitable, but less preferred for persulfate are Kanekalon (poly acrylo-nitrile- co-vinyl chloride, Kanegafuchi, Tokyo, Japan) and Orion (poly acrylonitrile, du Pont Co. , Wilmington, DE, U.S.A.) and equivalent products from other suppliers. For aqueous solutions of persulfate (and for dry sodium or potassium persulfate), microporous sheet is preferred which allows oxygen gas (from the slow decomposition of the persulfate) to escape but, in the case of solutions, inhibits the escape of liquid solution. Preferred is microporous Teflon TFE, e.g. Goretex (W.L. Gore and Associates, Elkton, MD, U.S.A.). Suitable for phosphoric acid are Noryl polyphenylene oxide (General Electric Co., Pittsfield, MA, U.S.A.), Lucite poly methyl methacrylate, Teflon, and Hypalon (du Pont Co., Wilmington, DE, U.S.A.), Kanekalon polyacrylonitrile-co-vinyl chloride (Kanegafuchi, Tokyo, Japan) and Kynar polyvinylidene fluoride (Pennwalt, Philadelphia, PA, U.S. A) and equivalent products from other suppliers.

Since certain changes may be made in the above-described apparatuses and processes without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted in an illustrative and not in a limiting sense.

Having described the invention, what we claim is:

Claims

1. An apparatus for separately determining the inorganic and organic carbon content of a water sample, said apparatus comprising a fluid circulation system including at least a first fluid flow path and, associated with said first fluid flow path: injection means for introducing a water sample into said first fluid flow path at an upstream location; fluid circulation means for moving said sample along said first fluid flow path from said upstream location to a downstream location; along said first fluid flow path between said upstream and downstream locations, at least first and second conversion means for sequentially converting substantially all of the inorganic carbon and thereafter substantially all of the organic carbon in said sample into carbon dioxide; and, first and second CO₂- detector means for determining the carbon dioxide content of said sample downstream respectively of said first and second conversion means.

2. An apparatus according to claim 1 further comprising carbon removal means, for removing carbon dioxide from said sample, located along said first fluid flow path between said first CO₂-detector means and said second conversion means.

3. An apparatus according to claim 2 further comprising alternate flow path means for said sample to bypass said carbon removal means and valve means to regulate the flow of said sample either through said carbon removal means or through said alternate path means.

4. An apparatus according to claim 1 further comprising means for collecting and storing a plurality of said samples at said downstream location.

5. An apparatus according to claim 1 wherein said first conversion means comprises a quantity of at least a first reagent, means for storing said first reagent in fluid communication with said first fluid flow path, and means for mixing a portion of said first reagent with said sample at a location upstream of said first CO₂-detector means.

6. An apparatus according to claim 5 wherein said first reagent comprises an acid.

7. An apparatus according to claim 1 wherein said second conversion means comprises at least a UV light source irradiating a portion of said first fluid flow path at an irradiation location between said first and second CO₂ detector means.

8. An apparatus according to claim 7 wherein said first fluid flow path is defined by a tubular wall consisting essentially of UV-transparent material at said irradiation location.

9. An apparatus according to claim 8 wherein said UV-transparent material is quartz.

10. An apparatus according to claim 7 wherein said second conversion means further comprises a quantity of at least a second reagent, means for storing said second reagent in fluid communication with said first fluid flow path, and means for mixing a portion of said second reagent with said sample between said first CO₂-detector means and said UV light source.

11. An apparatus according to claim 10 wherein said reagent is an oxidation agent.

12. An apparatus according to claim 7 wherein said second reagent consists essentially of one or more persulfate salts.

13. An apparatus according to claim 1 wherein at least one of said first and second CO₂-detector means comprises a sample region and a deionized water region separated by a CO₂-permeable membrane.

14. An apparatus according to claim 1 wherein both said first and second CO₂- detector means comprise a sample region and a deionized water region separated by a CO₂- permeable membrane.

15. An apparatus according to claim 14 wherein said first and second CO₂- detector means are in fluid communication with a source of deionized water.

16. An apparatus according to claim 15 further comprising fluid outlet and fluid inlet means respectively between said source of deionized water and each of said first and second CO₂-detector means.

17. An apparatus according to claim 16 further comprising ion-exchange means for removing ions from said deionized water.

18. An apparatus according to claim 4 wherein said means for collecting and storing samples comprises a waste reservoir located downstream from said second CO₂- detector means.

19. An apparatus according to claim 18 further wherein said waste reservoir has the capacity to hold at least ten of said samples.

20. An apparatus according to claim 1 wherein said fluid circulation means comprises means for pressurizing said fluid circulation system.

21. An apparatus according to claim 20 wherein said means for pressurizing said fluid circulation system comprises pump means at an upstream location and a back pressure regulator at a downstream location.

22. An apparatus according to claim 21 wherein said back pressure regulator is located along said circulation system between said second CO₂-detector means and a downstream waste reservoir.

23. An apparatus according to claim 1 further comprising pH measurement means located along a portion of said circulation system.

24. An apparatus according to claim 1 further comprising electrical conductivity measurement means located along a portion of said circulation system.

25. An apparatus according to claim 1 further comprising both pH measurement means and electrical conductivity measurement means located along a portion of said circulation system.

26. An apparatus according to claim 25 further wherein said pH measurement means and electrical conductivity measurement means are located along a second fluid flow path of said circulation system.

27. A process for separately determining the inorganic and organic carbon content of a water sample comprising the following steps: introducing a water sample into a sealed, pressurized fluid circulation system; moving said sample from an upstream location of said system to a downstream location; at a first location along said circulation system, converting substantially all of the inorganic carbon in said sample to carbon dioxide, and thereafter measuring the carbon dioxide in said sample; at a second location along said circulation system downstream from said first location, converting substantially all of the organic carbon in said sample to carbon dioxide, and thereafter measuring the carbon dioxide in said sample.

28. A process according to claim 27 wherein said sample is mixed at said first location with an effective amount of at least a first reagent sufficient to convert substantially all of the inorganic carbon in said sample to carbon dioxide.

29. A process according to claim 28 wherein said first reagent is pumped to said first location from a first reagent reservoir in fluid communication with said circulation system.

30. A process according to claim 28 wherein said first reagent comprises an acid.

1. A process according to claim 27 wherein said sample is exposed at said second location to an effective amount of UV radiation sufficient to convert substantially all of the organic carbon is said sample to carbon dioxide.

32. A process according to claim 31 further including the step of removing carbon dioxide from said sample prior to the UV radiation step.

33. A process according to claim 31 further wherein said sample is mixed at a third location along said circulation system, upstream of said UV radiation, with an effective amount of at least a second reagent sufficient to convert the organic carbon in said sample to carbon dioxide.

34. A process according to claim 33 wherein said second reagent is pumped to said third location from a second reagent reservoir in fluid communication with said circulation system.

35. A process according to claim 33 wherein said second reagent comprises an oxidizing agent.

36. A process according to claim 35 wherein said oxidizing agent consists essentially of one or more persulfate salts.

37. A process according to claim 27 further including the step of measuring the pH of the sample.

38. A process according to claim 27 further including the step of measuring the electrical conductivity of the sample.

39. A process according to claim 27 including the steps of measuring both the pH and the conductivity of the sample.

40. Apparatus for determining variable concentrations of organic carbon in water, said apparatus comprising a reactor system for oxidizing said variable concentrations of organic carbon to concentrations of oxidized carbon products, said reactor system including entrance conveying means for conveying said water at predeterminable volumetric flow rates into said reactor system, exit conveying means for conveying said water out of said reactor system, and means for determining concentrations of oxidized carbon products in said water, said reactor system further comprising at least a means selected from the group consisting of: (a) means for adding one or more oxidizing agents to said entrance conveying means in a predeterminable addition program over time of amounts of said oxidizing agents relative to a predetermined constant volumetric flow rate of said water, said addition program including at least one amount of said oxidizing agents which is less than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products and also including at least one other amount which is greater than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products; (b) means for irradiating said water within said reactor system with a source of ultraviolet light in a predetermined irradiation program over time of ultraviolet light intensities relative to a predetermined constant volumetric flow rate of said water, said irradiation program including at least one intensity which is less than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products and also including at least one other intensity which is greater than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products; (c) means for adding one or more oxidizing agents to said entrance conveying means at a constant predeterminable amount of said oxidizing agent relative to a constant predetermined volumetric flow rate of said water and for irradiating said water within said reactor system with a source of ultraviolet light in a predeterminable irradiation program over time of ultraviolet light intensities relative to said predetermined volumetric flow rate of water, said irradiation program including at least one intensity which is less than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products and also including at least one other intensity which is greater than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products; (d) means for adding one or more oxidizing agents to said entrance conveying means in a predeterminable constant amount of said oxidizing agents relative to a predetermined constant volumetric flow rate of said water and for controlling the temperature of said water within said reactor system to a predeterminable temperature program over time, said temperature program including at least one temperature which is less than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products and also including at least one other temperature which is greater than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products; and, (e) means for adding one or more oxidizing agents to said entrance conveying means at a constant predeterminable rate and for irradiating said water within said reactor system with a source of ultraviolet light at a predetermined constant intensity of ultraviolet light and for varying the volumetric flow rate of said water in a predeterminable flow rate program over time, said flow rate program including at least one flow rate which is greater than that flow rate which is sufficient to oxidize all of said organic carbon to oxidized carbon products and also including at least one other flow rate which is less than that flow rate which is sufficient to oxidize all of said organic carbon to oxidized carbon products.

41. A process for determining variable concentrations of organic carbon in water by means of an apparatus comprising a reactor system for oxidizing organic carbon in water to oxidized carbon products, said reactor system including entrance conveying means for conveying liquid into said reactor system and exit conveying means for conveying liquid out of said reactor system, said process comprising the step of conveying said water at predeterminable volumetric flow rates through said entrance conveying means into said reactor system, said process also comprising one or more steps selected from the group consisting of: (a) adding one or more oxidizing agents to said entrance conveying means in a predeterminable addition program over time of amounts of said oxidizing agents relative to a predetermined volumetric flow rate of said water, said addition program including at least one amount of said oxidizing agents which is less than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products and also including at least one other amount which is greater than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products; (b) irradiating said water within said reactor system with a source of ultraviolet light in a predetermined irradiation program over time of ultraviolet light intensities relative to a predetermined volumetric flow rate of said water, said irradiation program including at least one intensity which is less than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products and also including at least one other intensity which is greater than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products; ( c) adding one or more oxidizing agents to said entrance conveying means at a predeterminable amount of said oxidizing agent relative to a predetermined volumetric flow rate of said water and irradiating said water within said reactor system with a source of ultraviolet light in a predeterminable irradiation program over time of ultraviolet light intensities relative to said predetermined volumetric flow rate of water, said irradiation program including at least one intensity which is less than that intensity which is sufficient to oxidize all of said organic carbon to oxidized carbon products and also including at least one other intensity which is greater than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products; ( d) adding one or more oxidizing agents to said entrance conveying means in a predeterminable amount of said oxidizing agent relative to a predetermined volumetric flow rate of said water and controlling the temperature of said water within said reactor system to a predeterminable temperature program over time, said temperature program including at least one temperature which is less than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products and also including at least one other temperature which is greater than that which is sufficient to oxidize all of said organic carbon to oxidized carbon products; (e) adding one or more oxidizing agents to said entrance conveying means at a predeterminable constant rate over time and irradiating said water within said reactor system with a source of ultraviolet light at a predetermined intensity of ultraviolet light constant over time and varying the volumetric flow rate of said water according to a predeterminable flow rate program over time, said flow rate program including at least one flow rate which is greater than that flow rate which is sufficient to oxidize all of said organic carbon to oxidized carbon products and also including at least one other flow rate which is less than that flow rate which is sufficient to oxidize all of said organic carbon to oxidized carbon products; and, ( f) determining the concentration of oxidized carbon products in said water.

42. Apparatus for determining a concentration of organic carbon in water, said apparatus comprising a reactor system for oxidizing said concentration of organic carbon to concentrations of oxidized carbon products, said reactor system including entrance conveying means for conveying said water at predeterminable volumetric flow rates into said reactor system, also including exit conveying means for conveying said water out of said reactor system, said reactor system further comprising one or more means selected from the group consisting of: (a) means for adding one or more oxidizing agents to said entrance conveying means in a predeterminable program-over-time of amounts of said oxidizing agents relative to a predetermined constant volumetric flow rate of said water; (b) means for irradiating said water within said reactor system with a source of ultraviolet light in a predetermined program-over-time of ultraviolet light intensities relative to a predetermined constant volumetric flow rate of said water; (c) means for adding one or more oxidizing agents to said entrance conveying means at a constant predeterminable amount of said oxidizing agents relative to a constant predetermined volumetric flow rate of said water and for irradiating said water within said reactor system with a source of ultraviolet light according to a predetermined program-over- time of ultraviolet light intensities relative to said predetermined volumetric flow rate of water; (d) means for adding one or more oxidizing agents to said entrance conveying means in a predeterminable constant amount of said oxidizing agents relative to a predetermined constant volumetric flow rate of said water and for controlling the temperature of said water within said reactor system to a predetermined program-over-time of temperatures; (e) means for adding one or more oxidizing agents to said entrance conveying means at a constant predeterminable rate and for irradiating said water within said reactor system with a source of ultraviolet light at a predetermined constant intensity of such ultraviolet light and for varying the volumetric flow rate of said water in a predeterminable program-over-time; means for determining patterns-over-time of concentrations of oxidized carbon products in said water, said patterns-over-time corresponding to said programs-over-time; and means for calculating from said patterns-over-time said concentration of organic carbon in said water.

43. A process for determining a concentration of organic carbon in water by means of an apparatus comprising a reactor system for oxidizing organic carbon in water to oxidized carbon products, said reactor system including entrance conveying means for conveying liquid into said reactor system and exit conveying means for conveying liquid out of said reactor system, said process comprising the step of conveying said water at predeterminable volumetric flow rates through said entrance conveying means into said reactor system, said process also comprising one or more steps selected from the group consisting of: (a) adding one or more oxidizing agents to said entrance conveying means in a predeterminable program-over-time of amounts of said oxidizing agents relative to a predetermined volumetric flow rate of said water; (b) irradiating said water within said reactor system with a source of ultraviolet light in a predetermined program-over-time of ultraviolet light intensities relative to a predetermined volumetric flow rate of said water; (c) adding one or more oxidizing agents to said entrance conveying means at a predetermined amount of said oxidizing agent relative to a predetermined volumetric flow rate of said water and irradiating said water within said reactor system with a source of ultraviolet light in a predeterminable program-over-time of ultraviolet light intensities relative to said predetermined volumetric flow rate of water; (d) adding one or more oxidizing agents to said entrance conveying means in a predetermined amount of said oxidizing agent relative to a predetermined volumetric flow rate of said water and controlling the temperature of said water within said reactor system to a predeterminable program-over-time; (e) adding one or more oxidizing agents to said entrance conveying means at a predetermined rate constant over time and irradiating said water within said reactor system with a source of ultraviolet light at a predetermined intensity of ultraviolet light constant over time and varying the volumetric flow rate of said water according to a predeterminable program-over time; (f) determining patterns-over-time of concentrations of oxidized carbon products in said water, said patterns-over-time corresponding to said programs-over-time; (g) calculating from said patterns-over-time said concentration of organic carbon in water.

44. The apparatus of claim 40 or 42 or the processes of claims 41 and 43 in which said source of ultraviolet light in a member of the group consisting of low pressure, medium pressure and high pressure mercury arc lamps, doped mercury arc lamps, Xenon, Argon chloride, Argon fluoride, Krypton chloride, Krypton fluoride incoherent and coherent excimer lamps, and other gas discharge lamps which produce a substantial amount of radiation within the range of from about 160 to about 260 nm.

45. The apparatus of claim 40 or claim 42 which includes means for dislodging bubbles automatically.

46. The process of claim 41 or claim 43 which includes a step for dislodging bubbles.

47. The apparatus of claim 40 or 42 or the process of claim 41 or 43 in which the entrance conveying means includes means for removing bubbles from said water.

48. The apparatus of claim 40 or 42 or the process of claim 41 or 43 in which the entrance conveying means includes a membrane type degasser.

49. The apparatus of claim 40 or 42 or the process of claim 41 or 43 in which the entrance conveying means includes a membrane type degasser having liquid conductivity measuring means on the gas permeate side of said degasser.

50. The apparatus of claim 40 or 42 in which said means for adding one or more oxidizing agents includes a demountable container adapted to contain a predetermined quantity of a dry, water soluble oxidizing agent, and also includes integral with said apparatus means for adding a predetermined volume of water to said container or for adding water to said container at a predetermined rate.

51. The apparatus of claim 40 or 42 in which said means for adding one or more oxidizing agents includes a demountable container having the property of remaining intact when filled with oxidizing agent, packed in a hard plasic box and oveφacked in a cardboard box and dropped a distance of from about 6 to about 9 feet.

52. The apparatus of claim 40 or 42 in which said means for adding one or more oxidizing agents includes a demountable container fabricated from inert microporous polymer permeable to gas but passage resistant to liquid water.