Classifications

• • 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
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/28—Anaerobic digestion processes
  • C02F3/286—Anaerobic digestion processes including two or more steps
• • 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
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W10/00—Technologies for wastewater treatment
  • Y02W10/20—Sludge processing
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S435/00—Chemistry: molecular biology and microbiology
  • Y10S435/819—Fermentation vessels in series

Definitions

• the invention relates to a method and a device for digestion of sludge according to claim 1.
• DE-A1-3 230 010 disclosed a device for digestion of sludge.
• a tank divided into four chambers is used for the digestion.
• the tank can be tipped between two positions.
• the digestion process takes part in a bottom layer and some sludge will float up to the surface where it is digested only slowly or not digested at all.
• Biogas which is formed during the process presses Iiquid from one chamber into the second, and the tank is tipped from slightly tipping in one direction to slightly tipping in another direction. Valves within the tank are used for the passage of gas in an appropriate way.
• Valves within the tank are used for the passage of gas in an appropriate way.
• An object of the present invention is to essentially solve the problems discussed above such as large volumes, odour, low quality of sludge and specially made material. Another object is to accomplish a reliable device.
• the invention relates to a device for digestion of sludge in sewing systems comprising a dewatering chamber, a separate predigestor con ⁇ nected to a separate post digestor through a connecting line having an automatically controlled valve, said post digestor in turn being connected to a sludge receiver which is fed by sludge as well as mulch.
• the digested sludge material is automatically laid out in heaps for a maturing stage and can be mixed with garden waste to form a final product to be reused as a fertiliser.
• the process is anaerobic and gas is formed, which can be used for the heating of the sludge to increase the digestion efficiency and to decrease the digestion period.
• the sewing water comprises inter alia in solution the fertilis- ing compounds phosphorous and nitrogen and sometimes also added grinded sludge material from kitchen mills.
• Garden waste can also be added to the sludge to increase the amount of gas.
• Particles and sludge are sepa ⁇ rated at an early stage close to the source in a special separator and are transported by a pressure or vacuum system in thin tubes to a sludge treat- ment plant without generating any odour as a sanitary nuisance.
• the separated sludge first enters a second closed dewatering chamber, an inlet thereof being provided at a high position to accomplish a sedimentation and further thickening of the sludge.
• Excess water is led to a filtration tank to be treated.
• the thickened sludge is led automatically without any supply of air to a first separate digestor which suitably is circular and has a volume which is adapted to the expected load.
• a first separate digestor which suitably is circular and has a volume which is adapted to the expected load.
• Inside said digestor is provided with a device which facilitates homogenisa- tion of the sludge during fast tipping movements of the digestor.
• the tipping takes place within certain time intervals and at an appropriate speed.
• the control of the tipping movement can be automatized.
• the digestor is exter ⁇ nally provided with a heating device connected to a digestor gas combus- tion/biogas plant. A temperature increase of the sludge will accelerate the digestion
• the sludge is transferred automatically from a step one digestor to a step two digestor for a corre ⁇ sponding digestion period. Both digestors are similar and form together a module unit for digestion. If there are larger amounts of sludge further mod ⁇ ules can be connected in parallel to form a closed plant.
• the anaerobic microbial population is larger in the step two digestor, because this digestor is not exposed to oxygen containing water.
• the digestion time in one module is approximately 14 days, whereafter the sludge can be discharged into a screw milling the sludge together with mulch to a thick consistency adapted to be put out automatically in heaps on a sludge drying bed. After maturing of the sludge the material is suitable to be spread out on the fields or the soil.
• FIG. 1 shows a device according to the invention
• Fig. 2 is a basic drawing showing a device according to the invention for use within one field of application
• Fig. 3 shows an alternative embodiment of a device according to the invention
• Fig. 4 is a side elevational view of a part of the device according to Fig. 2.
• Fig. 1 shows that the device according to the invention comprises a closed free-standing dewatering chamber 29 and two separate digestors or containers 10A and 10B in series.
• Said dewatering chamber 29 is provided with an inlet 27, a valve28 and an outlet valve26 having an outlet. Through a coupling 12 said dewatering chamber is connected to said digestor 10A.
• the function of a presedimentation chamber is to pre-treat the sludge to obtain an appropriate water content. If the sludge is not thickened enough the di ⁇ reading will be less efficient.
• An appropriate concentration is at least 4-5 per cent dry matter of the sludge entering the digestors.
• each of the digestors 10A and 10B a Iiquid space 11A and 11 B, re ⁇ spectively, is enclosed.
• Said digestors 10A and 10B are mounted on a cradle 18, resting on a support 20 having a centred arrangement 33 which allow a varying slope against the horizontal plane.
• the fast tipping movements of the cradle is in the shown embodiment accomplished by a lifting device 34.
• the fast tipping movement makes the Iiquid within the digestors move heavily which results in good homogenisation of the sludge.
• said digestors 10A and 10B are circular cylindrical.
• Said digestor 10A is provided with a coupling 12 and an outlet 15 having an automatic valve 16 through which the sludge is passed on to the chamber 10B in step two for a second period of digestion.
• Said chambers 10A and 10B are internally provided with flow redirectors 22 facilitating a homogenisation of the sludge during the fast tipping movements.
• Said flow redirectors 22 are provided within said chambers 10A and 10B radially pro- jecting from a wall.
• said flow redirec ⁇ tors 22 comprise discs arranged centrally in axial direction in the chambers and radially projecting approximately one third of the diameter of the cham- bers from that side of the chambers forming the upper side when the cham ⁇ bers are in a horizontal position.
• said flow directors 22 are arranged to accomplish a similar redirection function in both directions of tippings. Therefore, said flow directors 22 are provided approximately in a central position in the axial di ⁇ rection of both chambers 10A and 10B.
• heating devices 14 are provided with heating devices 14.
• a heating device 14 is connected to a biogas com ⁇ bustion unit or a heating element 23.
• the digestor gas is taken care of according to the shown em ⁇ bodiment through a connecting line 13 on top of the tank.
• the gas line opens in a gas-holder 24.
• the excess Iiquid which has been formed in the chamber 11 is trans ⁇ ferred by means of gravity discharge to a Iiquid container 38 provided with a valve/connector 37, said container 38 being provided with a prefilter 35 made of turf and a postfilter 36 made of turf for the reduction of phosphorous and nitrogen and smaller solid particles accompanying the Iiquid.
• a prefilter 35 made of turf
• a postfilter 36 made of turf for the reduction of phosphorous and nitrogen and smaller solid particles accompanying the Iiquid.
• a lock in the outlet 15 and said valve 16 is opened and the sludge in the stage one chamber 10A is automatically transferred to step two chamber 10B in which the same process will take place as in 10A.
• the digestion in the chambers 10A, 10B is at least five days. Preferably the digestion period is at least seven days. During this time period the tipping movements are repeated at suitable intervals, preferably with a few hours repetition time. Sludge can be filled alternatively in module units 1 and 2.
• Fig. 2 shows what happens after the second digestion procedure in chamber 10B.
• the sludge is transferred through an outlet valve 17 to a screw device 30 where the digested sludge is mixed with mulch in a feeding device 19 and with inter alia garden waste in a second feeding unit and then put out in heaps 31 in a bed 32 arranged for this purpose. Then there is a maturing stage before the compost material is collected for manuring or to be put into bags.
• Fig. 3 shows an altemative embodiment of one of the main compo ⁇ nents of the invention.
• the cradle 18 with the containers 10A and 10B is pivotable within a more limited angle area limited by stops 40. Said stops are provided on the support 20.
• the inclination of the containers 10A and 10B allowed in this embodiment is sufficient to steer the sludge as desired and also to have a gravitational flow from the container 10A to the container 10B when the valve 16 is opened.
• Fig. 4 shows in an elevational view how biological material, such as mulch or garden waste from a feeding device 19, is mixed with digested sludge. The mixture is then transferred through a screw device 30 to heaps 31 in a bed 32.
• the highly compact embodiment of the device according to the inven ⁇ tion will considerably facilitate within the area of application described above, but also within other areas where a module extension is possible and an ad ⁇ aptation can be made to incoming volumes of sludge in relation to the cham ⁇ ber 10A, viz. to the population data.
• the almost odour-free method of diges- tion will allow a location of the plant close to built-up areas, however, under a roof.

Landscapes

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

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Citations (3)

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• 1995
  • 1995-08-10 SE SE9502798A patent/SE505749C2/sv not_active IP Right Cessation
• 1996
  • 1996-08-02 US US09/011,385 patent/US5906931A/en not_active Expired - Fee Related
  • 1996-08-02 AU AU67594/96A patent/AU6759496A/en not_active Abandoned
  • 1996-08-02 EP EP19960927968 patent/EP0846085A1/en not_active Withdrawn
  • 1996-08-02 WO PCT/SE1996/000983 patent/WO1997006110A1/en not_active Ceased
  • 1996-08-07 IN IN1419CA1996 patent/IN188705B/en unknown

Patent Citations (3)

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