WO2012164122A2 - Procédé de traitement de boues résiduelles - Google Patents

Procédé de traitement de boues résiduelles Download PDF

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Publication number
WO2012164122A2
WO2012164122A2 PCT/ES2012/070355 ES2012070355W WO2012164122A2 WO 2012164122 A2 WO2012164122 A2 WO 2012164122A2 ES 2012070355 W ES2012070355 W ES 2012070355W WO 2012164122 A2 WO2012164122 A2 WO 2012164122A2
Authority
WO
WIPO (PCT)
Prior art keywords
sludge
biogas
anaerobic digester
metals
anaerobic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/ES2012/070355
Other languages
English (en)
Spanish (es)
Other versions
WO2012164122A3 (fr
Inventor
Abdón Fausto ACEVEDO ÁLVAREZ
Roberto TORÍO ACHA
Laura GARCÍA RODRÍGUEZ
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Socamex S A
Original Assignee
Socamex S A
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Socamex S A filed Critical Socamex S A
Publication of WO2012164122A2 publication Critical patent/WO2012164122A2/fr
Publication of WO2012164122A3 publication Critical patent/WO2012164122A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/28—Anaerobic digestion processes
    • C02F3/2866—Particular arrangements for anaerobic reactors
    • C02F3/2893—Particular arrangements for anaerobic reactors with biogas recycling
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/02—Biological treatment
    • C02F11/04—Anaerobic treatment; Production of methane by such processes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/26—Treatment of water, waste water, or sewage by extraction
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/101—Sulfur compounds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel

Definitions

  • the present invention relates generally to the field of treatment and purification of wastewater. More specifically, the invention relates to a novel method of treating residual sludge that provides an optimization of biogas production as well as an improvement in the quality of the biogas produced, while improving the quality of the final sludge obtained.
  • sulfatorreductive bacteria BSR
  • BM methanogenesis
  • SSR sulfatorreductive bacteria
  • the sulphide generated in the anaerobic procedure is in equilibrium with the 3 ⁇ 4S. Therefore the biogas generated in the anaerobic digester may contain amounts of 3 ⁇ 4S that cause corrosion problems of equipment and facilities as well as an unpleasant smell.
  • the solution used for this problem is the dosage of metal salts (Sulfides precipitating in the mud), and performing gas washing.
  • the present invention therefore relates to a process for treating residual sludge obtained in a wastewater treatment plant.
  • the procedure comprises the steps of:
  • an increase in biogas production an improvement in the quality of said biogas produced (ie, a reduction in the amount of 3 ⁇ 4S present in the biogas produced) as well as obtaining a final dehydrated sludge, free of metals and unpleasant odors.
  • the final sludge obtained has a higher degree of sanitation than those obtained by prior art procedures, thereby allowing its proper use in agricultural applications by greatly minimizing its impact on the environment.
  • Figure 1 represents a diagram of an installation for carrying out the process according to a preferred embodiment of the invention.
  • FIGS 2A, 2B and 2C show graphs showing the concentrations of 3 ⁇ 4S and O2 in the biogas produced according to various embodiments of the process of the present invention. Detailed description of the invention
  • the first stage of the process of the present invention is the pretreatment of the residual sludge to perform its hydrolysis and the extraction of metals therefrom.
  • the demetalization step is preferably performed, although not necessarily, by the addition of at least one extractant compound.
  • said extracting compound is selected from the group consisting of inorganic acids, organic acids and chelating agents, and even more preferably said at least one extracting compound is citric acid or acetate.
  • the specific choice of the extractant used will depend on the metal content of the residual sludge in each specific case, and is part of the abilities of one skilled in the art.
  • Said stage of metal extraction, or demetalization is also carried out at an optimum pH, preferably at pH 2.
  • pH 2 value is optimal for the removal of the vast majority of metals, and therefore It is used according to the preferred embodiment of the present invention.
  • metals such as, for example, Cu, Al and Ni
  • these metals are usually not significantly present in the sludge. residuals, and generally do not pose a problem for the subsequent agricultural application of said mud.
  • metal extraction can be carried out at a pH value other than 2 (for example, at pH 11), or even various stages of metal extraction can be performed at different pH values.
  • centrifugation is performed to separate, on the one hand, the supernatant comprising the extracted metals, and on the other hand the sedimented sludge.
  • the supernatant is subsequently subjected to a draining step, pH correction and finally filtration.
  • Said filtration is preferably carried out by microfiltration or ultrafiltration membranes. In this way, it is possible to guarantee the quality of the supernatant by avoiding the use of sedimentators and clarifiers, which depend greatly on the hydraulic load and the physicochemical characteristics of the floc formed, thus ensuring the passage of all organic matter into the phase of metal free digestion.
  • the purification of said flow containing the extractants employed is carried out, through the use of cation exchange resins.
  • it is optimally allowed to recirculate said extractants for use in a subsequent residual sludge treatment process, thus reducing the overall cost of the procedure by reducing the amount of new extractants needed.
  • said sludge is preferably in a partially dehydrated state (a dry matter content of 4 to 12%). Said sedimented sludge is then conducted to a full-mix anaerobic digester in which it undergoes anaerobic digestion, thus allowing, as will be explained further below, the elimination of 3 ⁇ 4S.
  • anaerobic digestion of the sedimented sludge according to the process of the present invention is carried out under microaerophilic conditions, which allows the addition of additional reagents to be minimized thereby minimizing the impact on the environment of subsequent reuse of the sludge. final obtained.
  • salts for example of the ferric chloride type
  • the microaerophilic conditions in the anaerobic digester can be obtained either by the introduction of air or, preferably, by the introduction of oxygen-enriched air.
  • an oxygen concentrator equipment is available from the air. Said equipment provides the anaerobic digester with oxygen-enriched air, which preferably has a concentration in 96% oxygen. This reduces the unnecessary dilution of methane content as a result of the contribution of nitrogen, the major component of the air.
  • pure oxygen can of course also be used to provide the microaerophilic conditions required for the process of the present invention, however this will have an effect on the cost of the process, especially on an industrial scale.
  • the anaerobic digester comprises a biogas chamber that preferably occupies, although not necessarily, 20% of the total volume of the anaerobic digester.
  • the volume of anaerobic digester occupied by said biogas chamber will depend on the specific characteristics of the residual sludge being treated, such as for example the flow rate of said sludge.
  • oxygen enriched air or unenriched air according to other embodiments of the invention
  • introduction of oxygen enriched air (or unenriched air according to other embodiments of the invention) into the anaerobic digester is preferably carried out through the biogas chamber.
  • the introduction of air (enriched or not enriched in oxygen) into the biogas chamber is carried out by an air flow of 0.72 to 1.44 1 air / 1 day fed sludge.
  • the volume of the air flow introduced will depend in each case on the characteristics of the sludge to be treated and the volume of sulfur present.
  • process control is carried out by the technique of Gas chromatography in line, which allows to know at the moment the composition of the biogas produced in anaerobic digestion.
  • the biogas composition is the essential parameter in the monitoring and control of the process, since the changes in the operation variables are immediately reflected, thus allowing to know the course of the process. Therefore, the biogas composition, such as the amount of 3 ⁇ 4S, allows the air flow to be adjusted to achieve the desired process using minimum amounts of air.
  • a chromatograph is installed in the output stream of the biogas produced, which continuously analyzes the process variables.
  • Figure 1 also shows a biogas recirculation pipe from the biogas chamber to the anaerobic digester, from which it passes again by bubbling to the biogas chamber.
  • agitation is provided within the anaerobic digester as well as a larger gas-liquid contact surface, further improving the results of the process according to the present invention.
  • the process of the present invention is preferably performed under mesophilic conditions at a temperature of approximately 35 ° C.
  • the temperature of the sedimented sludge is maintained at this preferred value of approximately 35 ° C by recirculation of the sludge and heating thereof by means of a heat exchanger.
  • Said heat exchanger is fed by hot water from the treatment station to allow the sludge to be maintained at the proper temperature.
  • the time of residence of sedimented sludge in the anaerobic digester is less than 20 days, producing adequate results in terms of the quality and quantity of biogas produced, as well as in the quality of the final sludge obtained.
  • This residence time of less than 20 days is a substantial improvement over the procedures known in the prior art, additionally providing a saving in the costs of the process and thus constituting an additional advantage of an embodiment of the present invention.
  • a series of examples of the process of the present invention were made under different process conditions. Analytical monitoring was performed by gas chromatography of the biogas composition obtained in each of the experiments. The temperature in all cases was maintained at 35 ° C in the anaerobic digester by recirculation of part of the sludge through a heat exchanger, as described above.
  • Table 1 presents a summary of the conditions used in each of the examples made of the process of the present invention, as well as a comparative example, and of the results obtained with each of them regarding the characteristics of the biogas obtained .
  • Figure 2A shows a comparison between comparative example 1 and example 2. It is observed that thanks to the conditions of example 2 according to the process of the present invention, the amount of 3 ⁇ 4S in the biogas produced is reduced from values close to 3000 ppm (v / v) (comparative example) up to average values of 165.7 ppm (v / v), which means an elimination of 3 ⁇ 4S of 95%, thereby increasing the oxygen concentration of biogas to average values of 3, 91%
  • Figure 2B shows a comparison between example 2 and example 3-4.
  • the value of the air flow used is increased, although air not enriched in oxygen is used.
  • the rest of the procedure conditions remain constant with respect to example 2.
  • the amount of 3 ⁇ 4S in the biogas obtained up to values close to 0 ppm.
  • FIG. 2C shows a comparison between Example 3-4 and Example 5.
  • Example 5 presents the same conditions as in Example 2 above, with the only difference that biogas recirculation does not occur in The anaerobic digester Therefore, agitation within the digester occurs only by the recirculation of the sludge.
  • Example 6 was carried out to look for the conditions that would allow minimizing the reagents used (in this case, oxygen) maintaining 3 ⁇ 4S levels in the biogas optimized and adequate, thus maximizing the production of methane in the biogas obtained. It was found that these conditions consisted of the recirculation of both biogas and sludge being treated, and the addition of enriched air in the biogas chamber with a flow of 0.125 1 / min.
  • the process of the present invention provides substantial improvements in terms of quality of biogas produced (decrease in the amount of 3 ⁇ 4S present in it), the amount of biogas produced as well as the quality of the final sludge obtained that can be used properly for agricultural purposes, for example, without affecting the environment in the It is used.
  • the process of the present invention described above thus implies a substantial improvement over the known prior art, since they reduce the overall cost of the process (the addition of additional reagents to precipitate sulfides is not required), improves the quantity and quality of the Biogas produced (so that the treatment plant will have a net energy production) as well as the quality of the final sludge obtained for later use, for example, for agricultural purposes.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Organic Chemistry (AREA)
  • Water Supply & Treatment (AREA)
  • Environmental & Geological Engineering (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Molecular Biology (AREA)
  • Health & Medical Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Microbiology (AREA)
  • Sustainable Development (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Treatment Of Sludge (AREA)

Abstract

L'invention concerne un procédé de traitement de boues résiduelles pour optimiser la production de biogaz et la qualité de celui-ci, ainsi que la qualité de la boue finale obtenue. Le procédé comprend les étapes consistant à réaliser une hydrolyse et une extraction des métaux antérieure à celle des boues résiduelles, à effectuer une centrifugation pour séparer de la boue déposée le liquide surnageant qui contient les métaux, et à soumettre la boue déposée à une digestion anaérobie dans des conditions microaérophiles dans une cuve de digestion anaérobie de mélange complet pour éliminer H2S.
PCT/ES2012/070355 2011-05-31 2012-05-18 Procédé de traitement de boues résiduelles Ceased WO2012164122A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ESP201130892 2011-05-31
ES201130892A ES2362852B2 (es) 2011-05-31 2011-05-31 Procedimiento de tratamiento de fangos residuales.

Publications (2)

Publication Number Publication Date
WO2012164122A2 true WO2012164122A2 (fr) 2012-12-06
WO2012164122A3 WO2012164122A3 (fr) 2013-03-14

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PCT/ES2012/070355 Ceased WO2012164122A2 (fr) 2011-05-31 2012-05-18 Procédé de traitement de boues résiduelles

Country Status (2)

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ES (1) ES2362852B2 (fr)
WO (1) WO2012164122A2 (fr)

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3335265A1 (de) * 1983-09-29 1985-05-02 Abwasserverband Raumschaft Lahr, 7630 Lahr Verfahren zur reduzierung des h(pfeil abwaerts)2(pfeil abwaerts)s-gehaltes bei anaeroben schlammfaulverfahren
DE3902867A1 (de) * 1989-02-01 1990-08-02 Reiflock Umwelttech Reichmann Verfahren und anlage zum anaeroben abbau von hochbelasteten prozessabwaessern
US5500123A (en) * 1993-12-28 1996-03-19 Institute Of Gas Technology Two-phase anaerobic digestion of carbonaceous organic materials
DE19725823B4 (de) * 1997-06-18 2004-07-08 Linde-Kca-Dresden Gmbh Verfahren zur Biogasgewinnung
DE102007013190A1 (de) * 2007-03-15 2008-09-18 Mt-Energie Gmbh & Co. Kg Verfahren und Vorrichtung zum Abbau schädlicher Stoffe mittels Zuführen von Sauerstoff
FR2948355B1 (fr) * 2009-07-21 2011-09-02 Ondeo Ind Solutions Procede de methanisation, a partir d'effluents industriels ou urbains, liquides ou solides

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Publication number Publication date
WO2012164122A3 (fr) 2013-03-14
ES2362852B2 (es) 2012-01-30
ES2362852A1 (es) 2011-07-14

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