GB2078705A

GB2078705A - Apparatus for the determination of biochemical oxygen demand

Info

Publication number: GB2078705A
Application number: GB8121654A
Authority: GB
Original assignee: Corning Glass Works
Current assignee: Corning Glass Works
Priority date: 1978-02-24
Filing date: 1979-02-23
Publication date: 1982-01-13
Also published as: JPS54124557A; GB2014979A; FR2418204B1; FR2418204A1; JPS6218233B2; DE2905391A1; GB2014979B; DE2905391C2; GB2078705B; CA1117668A

Abstract

An apparatus for the determination of the biochemical oxygen demand of an organic waste in an aqueous medium which comprises a sampling and/or sensing means serially connected to an immobilized microbe reactor, which is an aerobic reactor comprising a porous inorganic support which is suitable for the accumulation of a biomass, which in turn is serially connected to a sampling and/or sensing means is disclosed.

Description

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GB 2 078 705 A 1

SPECIFICATION

Apparatus for the Determination of Biochemical Oxygen Demand

This invention relates to an apparatus for the determination of biochemical oxygen demand (BOD).

5 Published U.K. Patent Application No. 2,014,979 (application No. 79 06584) relates to a method 5

for processing organic waste in an aqueous medium which comprises passing an organic waste-containing aqueous medium through a first immobilized microbe reactor which is an aerobic reactor comprising a porous inorganic support which is suitable for the accumulation of a biomass; and then through a second immobilized microbe reactor which is an anaerobic reactor comprising a controlled-10 pore, hydrophobic inorganic membrane comprising a porous inorganic support which is suitable for the 10 accumulation of a biomass wherein at least 90 per cent of the pores of the inorganic membrane have diameters of from 10~6 to 10~4 cms (from 100 to 10,000 A).

It also relates to an apparatus which may be used in accordance with such a method.

It further relates to an apparatus for the determination of the biochemical oxygen demand of an 15 organic waste in an aqueous medium which comprises a sampling and/or sensing means serially 15

connected to a first immobilized microbe reactor, which is an aerobic reactor comprising a porous inorganic support which is suitable for the accumulation of a biomass, which is serially connected to a second immobilized microbe reactor, which is an anaerobic reactor comprising a controlled-pore, hydrophobic inorganic membvane comprising a porous inorganic support which is suitable for the 20 accumulation of a biomass, which is serially connected to a sampling and/or sensing means. 20

A variety of methods for the disposal or organic waste, either industrial or agricultural, are available. Some of these methods, such as burial, land-fill and dumping at sea, have a negative environmental impact and are not desirable. On the other hand, methods are available for converting organic waste to a source of energy and/or a usable product and include biological aerobic or anaerobic 25 fermentation, thermophilic aerobic digestion, destructive distillation (including 25

hydrocarbonization and pyrolysis) and incineration. See, for example, W. J. Jewell et af, "Methane Generation from Agricultural Wastes: Review of Concept and Future Applications," Paper No.

NA74—107, presented at the 1974 Northeast Regional Meeting of the American Society of Agricultural Engineers, West Virginia University, Morgantown, West Virginia, U.S.A., August 18 to 21, 1974. Of 30 this latter group, biological anaerobic fermentation appears to be the most promising and has received 30 considerable attention in recent years.

Current interest in biological anaerobic fermentation appears to be due, at least in part, to the development of the anaerobic filter. See, for example, J. C. Young et al, Jour, Water Poll, Control Fed., 41, R160 (1969); P. L. McCarty, "Anaerobic Processes", a paper presented at the Birmingham Short 35 Course on Design Aspects of Biological Treatment, International Association of Water Pollution 35

Researth, Birmingham, England, September 18, 1974; and J. C. Jennett et af. Jour, Water Poll, Control Fed., 47, 104 (1975). The anaerobic filter is basically a rock-filled bed similar to an aerobic trickling filter. In the anaerobic filter, however, the waste is distributed across the bottom of the filter. The flow of waste is upward through the bed of rocks so that the bed is completely submerged. Anaerobic 40 microorganisms accumulate in the spaces between the rocks and provide a large, active biological 40 mass. The effluent typically is essentially free of biological solids. See. J. C. Young et at, supra, at R160.

The anaerobic filter, however, is best suited for the treatment of water-soluble organic waste. See J. C. Young ef al, supra, at R160 and R171. Furthermore, very long retention times of the waste in the filter are required in order to achieve high reductions in the chemical oxygen demand (COD) of the 45 waste to be treated. That is, depending upon the COD of the waste stream, reductions in COD of from 45 36.7 per cent to 93.4 per cent required retention times of from 4.5 to 72 hours. See J. C. Young et al, supra, at R167. In addition such results were achieved using optimized synthetic wastes which were balanced in carbon, nitrogen and phosphorus content and which had carefully adjusted pH values.

Accordingly, there remains a great need for a waste processing method which may tolerate the "50 presence of solids in the waste stream and which may more rapidly process the waste on an "as is" 50 basis.

The present invention provides an apparatus for the determination of the biochemical oxygen demand of an organic waste in an aqueous medium which comprises a sampling and/or sensing means serially connected to an immobilized microbe reactor, which is an aerobic reactor comprising a porous 55 inorganic support which is suitable for the accumulation of a biomass, which in turn is serially 55

connected to a sampling and/or sensing means.

As used herein, the term "biodegradable" means that at least some of the organic waste must be capable of being degraded by microorganisms. As a practical matter, usually at least 50 per cent, by weight, of the organic waste will be biodegradable. It may be necessary or desirable, however, to utilize 60 waste having substantially lower levels of biodegradable organic matter. 60

Thus, the organic waste or the aqueous medium containing such waste may contain nonbiodegradable organic matter and inorganic materials, provided that the organic waste and aqueous medium are essentially free of compounds having significant toxicity toward the microbes present in the reactor.

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In general, the nature of the aqueous medium is not critical. In most instances, water will constitute at least 50 per cent, by weight, preferably from 80 to 98 per cent, by weight, of the aqueous medium.

Frequently, the waste stream may be used without pre-treatment. Occasionally, it may be desirable or necessary to dilute the waste stream with water, to separate from the waste stream 5

excessive amounts of solids or excessively coarse solids which might interfere with the pumping equipment necessary to move the aqueous medium through the apparatus or the increase the pH of the aqueous medium by, for example, the addition of an inorganic or organic base, such as potassium carbonate, sodium hydroxide or triethylamine. Alternatively, solid or essentially non-aqueous organic waste may be diluted with water as desired. 10

As mentioned above, the reactor contains a porous inorganic support which is suitable for the accumulation of a biomass.

Preferably, the inorganic support in the reactor is a porous, high surface area inorganic support which is suitable for the accumulation of a high biomass surface within a relatively small volume. More preferably at least 70 per cent of the pores of the inorganic support have diameters at least as large as f5 the smallest major dimension, but less than five times the largest major dimension, of the microbes present in the reactor. Most preferably, the average diameter of the pores of the inorganic support is from 0.8 to 220 fx (from 8x10-5 to 2.2x 10-2 cms).

As used herein, the expression "high surface area inorganic support" means an inorganic support having a surface area of greater than 0.01 m2 per gram of support. In general, surface area is 20

determined by inert gas adsorption or the B.E.T. method; see, e.g., S. J. Gregg and K.S.W. Sing,

"Adsorption, Surface, Area, and Porosity", Academic Press, Inc., New York, 1967. Pore diameters, on the other hand, are most readily determined by mercury intrusion porosimetry; see, e.g., N. M. Sinslow and J.J. Shapiro, "An Instrument for the Measurement of Pore-Size Distribution by Mercury Penetration", ASTM Bulletin No. 236, Feb. 1959. 25

In general, the inorganic support may be either siliceous or non-siliceous metal oxides and may be either amorphous or crystalline. Examples of siliceous materials include glass, silica, cordierite, wollastonite and bentonite. Examples of non-siliceous metal oxides include alumina, spinel, apatite,

nickel oxide and titania. Also, the inorganic support may be composed of a mixture of siliceous and non-siliceous materials, such as alumino-cordierite. Cordierite materials, such as the one employed in 30 the Examples below are preferred.

For a more complete description of the inorganic support reference may be made to Published U.K. Patent Application No. 2,004,300.

As mentioned above, the inorganic support in the reactor provides a locus for the accumulation of microbes. The porous nature of the support not only permits the accumulation of a relatively high 35

biomass per unit volume of reactor, but also aids in the retention of the biomass within the reactor.

As used herein, the term "microbe" (and derivations thereof) is meant to include microorganisms which degrade organic materials, e.g. utilize organic materials as nutrients. This terminology, then,

also includes microorganisms which utilize as nutrients one or more metabolites of one or more other microorganisms. Thus, for example, the term "microbe", includes algae, bacteria, moulds and yeasts. 40 The preferred microbes are bacterial, moulds and yeasts, with bacteria being most preferred.

In general, the nature of the microbes present in the reactor is not critical. It is only necessary that the biomass in the reactor be selected to achieve the desired results. Thus, such biomass may consist of a single microbe species or several species, which species may be known or unidentified.

Furthermore the biomass in the reactor need not be strictly aerobic, provided that the primary functions 45 of the reactors are consistent with the designation thereof as aerobic. The term "primary function" as used herein means that at least 50 per cent of the biomass in the reactor functions in accordance with the reactor designation.

Examples of microbes which may be employed in the aerobic reactor include strict aerobic bacteria, such as Pseudomonas f/uorescens and Acinetobacter calcoaceticus; facultative anaerobic 50 bacteria, such as Escherichia cohBacillus subtilis. Streptococcus faecalis. Staphylococcus aureus, Salmonella typhimurium, Klebsiella pheumoniae, Enterobacter cloacae and Proteus vulgaris; moulds such as Trichoderma viride and Aspirgillus niger, and yeasts, such as Saccharomyces cerevisiae and Sacchoromyces ellipsoideus.

As mentioned above the microbes employed in the reactor are selected on the basis of the result 55 desired.The choice of microbes may be influenced by efficiency, operating parameters, such as temperature and flow rate, microbe availability or microbe stability.

In general, the microbes are introduced into the reactor in accordance with conventional procedures. For example, the reactor may be seeded with the desired microbes, typically by circulating through the reactor an aqueous microbial suspension. Alternatively, the microbes may be added to the 60 waste stream at a desired point. In cases where the waste stream already contains the appropriate types of microbes, the passage of such waste through the reactor will in due course establish the requisite microbe colonies in the reactor.

Among suppliers of porous inorganic support materials are the following : Alcoa (Registered

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Trade Mark), Catalytic Chemical Co. Ltd., Coors, Corning Glass Works, Davison Chemical, Fuji Davison Co. Ltd., Harrisons & Crosfield (Pacific) Inc., Kaiser Chemicals, Mizusawa Kagaku Co. Ltd., Reynolds Metals Company (Chemicals Division), Rhodia, Inc. (Chemical Division) and Shokubai Kasei Co. Ltd.

It should be apparent to those skilled in the art that the configuration of the reactor is not critical.

Most often, the reactor will be a conventional cylindrical or tubular plug flow-type reactor, such as are 5 described in the Examples below. Accordingly, the reactor typically comprises a cylinder or tube open at both ends which contains the inorganic support. Such cylinder is composed of a suitable material which is impervious to both gases and liquids. Suitable materials include glass, stainless steel, glass-coated steel and poly(tetrafluoroethylene). The reactor is optionally jacketed, especially where it is either desirable or necessary to contain, isolate, analyze, utilize, or otherwise handle gaseous products 10 evolved during the process. The jacket, if present, may be constructed from one of the conventional materials, such as those listed above.

In more general terms, the reactor will normally be shaped in such a manner as to provide one or more channels for the passage of a fluid. Where multiple channels are provided, such channels may provide independent flow of the fluid through such channels or they may be serially connected. The 15 aqueous medium may flow through such channels or around such channels. Thus, the inorganic support may be contained in such channels or located around such channels. For example, given the cylindrical reactor described above, the inorganic support may be contained within the cylinder or tube. Alternatively, the cylinder or tube may be jacketed and the inorganic support may be located between the jacket and the cylinder or tube. Hence, the aqueous medium may flow either through or around the 20 cylinder or tube.

Under normal circumstances, the reactor is maintained at ambient temperature. Indeed, the process is most preferably carried out at ambient temperature. While process temperatures are critical only to the extent that the microbes present in the reactor remain viable, as a practical matter, the process will generally be carried out at a temperature of from 10 to 60°C. In those instances where an 25 elevated temperature is desired, the preferred temperature range is from 30 to 35°C.

The present invention provides an apparatus for the determination of the biochemical oxygen demand (BOD) of a biodegradable organic waste in an aqueous medium. Such apparatus comprises: a sampling and/or sensing means serially connected to the aerobic reactor described above, which reactor in turn is serially connected to a sampling and/or sensing means. 30

As used herein, the term "sampling and/or sensing means" is meant to include a sampling means, a sensing means and a sampling and sensing means.

Accordingly, the sampling and/or sensing means may be nothing more than a port, fitted with, for example, a stopcock or rubber septum, to provide a means for the manual withdrawal of a sample from the waste stream. Alternatively, such sampling means may be an automated sampling device which 35 automatically removes samples of a precise size at predetermined intervals and stores such samples for future handling or analysis.

Examples of suitable sensing means include dissolved oxygen sensor, conductivity sensor,

ammonium ion sensor and pH electrode. Actually, various sensing means may be used which will detect measurable differences in the organic waste-containing aqueous medium which are the result of 40 the biochemical conversions taking place in the apparatus for determining BOD.

As contemplated by the present invention, a sampling and sensing means may be a combination of a sampling means and a sensing means. For example, an automated sampling device may be serially connected to an automated device for determining COD by a chromic acid oxidation procedure.

Furthermore, the two sampling and/or sensing means need not be physically discrete or separate. 45 That is, with appropriate connecting and waste stream directing means, a single sampling and/or sensing means may be employed in the present BOD apparatus. Thus, when using a single sampling and/or sensing means, the waste stream or a portion thereof is first passed through the sampling and/or sensing means. The waste stream then enters the aerobic reactor. Upon exiting the aerobic reactor, the waste stream or a portion thereof is directed to the sampling and/or sensing means by 50 appropriate connecting and directing means which are well known to those skilled in the art.

The present invention is illustrated by the following Examples.

The sewage employed in the following Examples was obtained from the inlet pipe to the Corning, New York, U.S.A., Municipal Sewage Waste Treatment Plant. The sewage was stored at from 4 to 6°C. Prior to use, the sewage was filtered through cheesecloth and glass wool to remove coarse particulate 55 matter. Sewage was collected either weekly or biweekly.

Example 1

A two-litre reagent bottle provided with a side arm at the bottom was connected, via a length of "Tygon" tubing attached to the side arm, to the inlet port of a Fluid Metering, Inc. Model RP G-6 pump (Fluid Metering, Inc., Oyster Bay, New York, U.S.A.). The outlet port of the pump was attached again via 60 'Tygon" tubing to the bottom of a vertically-mounted 9x 150 mm Fisher and Porter chromatographic column (obtained from Arthur H. Thomas Co., Philadelphia, Pa. U.S.A.). The column was charged with 6.5 g of cordierite (CGZ) carrier having a pore diameter distribution of from 2 to 9 /u (from 2x10~4 to 9x 10~4 cms) and an average pore diameter of 4.5 fi (4.5x10-4 cms). The top of the column was

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connected by "Tygon" tubing to the inlet port of a cell having sealably mounted therein the dissolved oxygen sensor of a Diffusion Oxygen Analyzer (International Biophysics Corp., Irvine Ca„ U.S.A.). The outlet port of the cell was connected by 'Tygon" tubing to a receiving vessel. Another dissolved oxygen sensor was placed in the reagent bottle which served as a waste stream reservoir. Each dissolved oxygen sensor was standardized against air-saturated water at 21.9% saturation.

The column was seeded by continuously recirculating a volume of sewage through the column at a flow rate of 1 ml/min for five days. A sterile, standard BOD solution containing 150 mg/litre each of glutamic acid and glucose was passed through the column at 0.37 m/min for 24 hours as a preconditioning to ensure adequate bioaccumulation prior to collecting oxygen uptake data. The standard BOD solution then was passed through the column or immobilized aerobic microbe reactor. The effluent per cent saturation was measured at three different flow rates. In each case, the per cent saturation of the feed in the reservoir was 21.9% and the effluent per cent saturation reading stabilized within 20 to 60 min after changing the flow rate. The results are summarized in Table I.

Table I Oxygen Uptake

Flow Rate (ml/min) Effluent % Saturation

0.19 7a

0.37 10

2.07 18.5

"Decreased to 4.5 after an additional 12 hours.

From Table I, it is apparent that oxygen uptake is inversely proportional to the flow rate. Oxygen uptake, expressed as the percentage of dissolved oxygen consumed, is summarized in Table II and was calculated in accordance with the following formula:

Feed % Sat'n—Eff. % Sat'n "Feed % Sat'n

102 consumed= x 100

Table II

Percentage of Dissolved Oxygen Consumed

Flow Rate, ml/min % 02 Consumed

0.19 68a

0.37 54

2.07 16

"Increased to 79% after an additional 12 hours.

Example 2

The procedure of Example 1 was repeated, except that the column was seeded with 200 ml of an overnight tryptic soy broth culture of Escherichia coli( 10® cells/ml) and the standard BOD solution was replaced with sterile broth. After the 24-hour preconditioning period, the effluent per cent saturation was measured and found to be 0%; the broth per cent saturation originally was 21.9%. Thus, 100% of the dissolved oxygen was consumed.

The Examples clearly demonstrate the feasibility of measuring a difference in an organic waste-containing aqueous medium, which difference is the result of biochemical conversions (oxidations) taking place in the BOD apparatus.

Such a measurable difference then is readily correlated to BOD by known procedures. For one example of such a correlation, see I Karube et al Biotechnol. Bioeng., 19,1535 (1977). Thus, for a given aerobic reactor, passing standard solutions having varying concentrations of organic material at a given flow rate will yield a set of, for example, oxygen uptake data. The BOD values of such standard solutions may be determined by conventional methods to give a set of conventional BOD values. The two sets of data may then be combined in graphical form to give a standard curve for each flow rate employed. The BOD of an organic waste in an aqueous medium is then determined quickly and simply by passing such aqueous medium through the BOD apparatus and comparing the data obtained with the appropriate standard curve.

Claims

1. An apparatus for the determination of the biochemical oxygen demand of an organic waste in an aqueous medium which comprises a sampling and/or sensing means serially connected to an immobilized microbe reactor, which is an aerobic reactor comprising a porous inorganic support which is suitable for the accumulation of a biomass, which in turn is serially connected to a sampling and/or sensing means.

2. An apparatus as claimed in claim 1 comprising a single sampling and/or sensing means.

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3. An apparatus as claimed in claim 1 comprising two separate sampling and/or sensing means of the same type.

4. An apparatus as claimed in any of claims 1 to 3 comprising sampling and/or sensing means comprising a dissolved oxygen sensor.

5 5. An apparatus as claimed in claim 1 or claim 3 comprising sampling and/or sensing means 5

comprising an ammonium ion sensor.

6. An apparatus as claimed in claim 1 substantially as herein described.

7. An apparatus as claimed in claim 1 substantially as herein described with reference to the Examples.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1982. Published by the Patent Office,

25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.