NOVEL FACILITY FOR TREATING WASTE WATER

Abstract

Disclosed is a facility for treating waste water of municipal or industrial origin, in particular a facility for primary treatment of the water, including a biological contact tank equipped with biological rotating discs, which is connected upstream of a ballasted-floc physiochemical decanter, the decanter being at least made up of a coagulation zone, a flocculation zone, a lamellar decanting zone and a thickening zone and an external circuit allowing the recirculation of the sludge thickened in the thickening zone to the flocculation zone and the biological contact tank.

Claims

1. A facility for treating waste water of municipal or industrial origin, in particular a facility for primary treatment of said water, comprising a biological contact tank (1) equipped with biological rotating discs (8), which is connected upstream of a ballasted-floc physiochemical decanter (2), said decanter comprising at least a coagulation zone (3), a flocculation zone (4), a lamellar decanting zone (5), a thickening zone (6) and an external circuit (7) allowing the recirculation of the sludge thickened in the thickening zone (6) to the flocculation zone (4) and said biological contact tank (1).

2. The facility as claimed in claim 1, wherein the biological contact tank (1) has a volume allowing a contact time of the untreated water in said contact tank to be less than 20 minutes, advantageously between 10 and 20 minutes.

3. The facility as claimed in claim 1, wherein the number and size of the biological rotating discs (8) in the biological contact tank (1) are a function of the load of dissolved carbonated pollution.

4. The facility as claimed in claim 1, wherein said biological contact tank (1) comprises a means for measuring the concentration of dissolved oxygen in the biological contact tank (1), in particular a sensor immersed in said tank.

5. The facility as claimed in claim 1, wherein said biological contact tank (1) comprises a means for measuring the concentration of solid matter in said tank.

6. The facility as claimed in claim 1, wherein said decanter (2) comprises a means for measuring the recirculation flow of the thickened sludge.

7. The facility as claimed in claim 1, wherein said biological contact tank (1) is confined.

8. A method for treating waste water of municipal or industrial origin, in particular a method for primary treatment of water by a facility as defined in claim 1, comprising the following steps: injecting untreated water into the biological contact tank (1) equipped with biological rotating discs (8) of said facility, holding the untreated water in said tank (1) for a contact time of less than 20 minutes in order to eliminate the dissolved pollution, injecting the water from the biological contact tank (1) into the decanter (2) of said facility and holding it there in order to eliminate the particulate and colloidal pollution, extracting the treated water from the lamellar decanting zone (5) of said facility and the thickened sludge from the thickening zone (6), where applicable, recirculating part of the thickened sludge to the flocculation zone (4) and said contact tank (1).

9. The method as claimed in claim 8, wherein the concentration of solid matter in the biological contact tank (1) is held at 1 g/L to 2 g/L.

10. The method as claimed in claim 8, wherein the recirculation flow to the biological contact tank (1) is between 3% and 10% of the flow of untreated water.

11. The method as claimed in claim 8, wherein the rotation speed of the discs (8) is a function of the concentration of dissolved oxygen in the biological contact tank (1) and of the quantity of biomass fixed to the discs.

12. The facility as claimed in claim 2, wherein the number and size of the biological rotating discs (8) in the biological contact tank (1) are a function of the load of dissolved carbonated pollution.

13. The facility as claimed in claim 2, wherein said biological contact tank (1) comprises a means for measuring the concentration of dissolved oxygen in the biological contact tank (1), in particular a sensor immersed in said tank.

14. The facility as claimed in claim 3, wherein said biological contact tank (1) comprises a means for measuring the concentration of dissolved oxygen in the biological contact tank (1), in particular a sensor immersed in said tank.

15. The facility as claimed in claim 2, wherein said biological contact tank (1) comprises a means for measuring the concentration of solid matter in said tank.

16. The facility as claimed in claim 3, wherein said biological contact tank (1) comprises a means for measuring the concentration of solid matter in said tank.

17. The facility as claimed in claim 4, wherein said biological contact tank (1) comprises a means for measuring the concentration of solid matter in said tank.

18. The facility as claimed in claim 2, wherein said decanter (2) comprises a means for measuring the recirculation flow of the thickened sludge.

19. The facility as claimed in claim 3, wherein said decanter (2) comprises a means for measuring the recirculation flow of the thickened sludge.

20. The facility as claimed in claim 4, wherein said decanter (2) comprises a means for measuring the recirculation flow of the thickened sludge.

Description

[0064] The invention is further illustrated by FIG. 1 and the examples below.

[0065] FIG. 1 shows a facility of the invention which consists of a biological contact tank (1) equipped with biological rotating discs (8), connected upstream of a ballasted-floc physicochemical decanter (2), said decanter comprising at least a coagulation zone (3), a flocculation zone (4), a lamellar decanting zone (5), a thickening zone (6) and an external circuit (7) allowing recirculation of the sludge thickened in the thickening zone (6) towards the flocculation zone (4) and/or said biological contact tank (1).

EXAMPLES

1. Exemplary Embodiment

[0066] A facility of the invention is implemented for the treatment of a municipal waste water corresponding to 50,000 eh.

[0067] The untreated water flow to be treated is 10,000 m3/d. The peak coefficient is 2.

[0068] The pollutant load of this untreated water is specified in table 1 below.

TABLE-US-00001 TABLE 1 Load DCO kg/d 6000 DBO kg/d 3000 MES kg/d 3100 NTK kg/d 500 PT kg/d 100

[0069] The totality of oxidizable pollutants present in the untreated water is represented by DCO (chemical oxygen demand). The biodegradable carbonated organic pollution in the untreated water is represented by DBO (biochemical oxygen demand). The MES value (suspended matter) corresponds to the quantity of elements in suspension in the untreated water. The NTK value corresponds to the quantity of nitrogen in organic or ammoniacal form in the untreated water (total Kjeldahl nitrogen). The PT value corresponds to the quantity of total phosphorus, comprising particulate phosphorus and dissolved phosphorus.

[0070] The treatment using a facility of the invention is compared with treatment by a “Densadeg” type physicochemical decanter alone.

[0071] The main characteristics of the two treatment methods are shown in table 2 below:

TABLE-US-00002 TABLE 2 Method by the facility of the Method by invention “Densadeg” ® Volume Decanter 391 m.sup.3 391 m.sup.3 Biological contact  80 m.sup.3 tank Total ground area  99 m.sup.2  79 m.sup.2 MES discharge (mg/L) 30.0 50.3 DBO discharge (mg/L) 75.6 146.0 Reduction of Reduction of 75% 48% DCO discharge (mg/L) 159 249 Nitrogen discharge (mg/L) 42.7 42.1 N—NH.sub.4 40.2 95.3 N—NO.sub.3 0.0 0.0 Phosphorus discharge (mg/L) 4.9 6.3 P-PO.sub.4 (mg/L) 4.4 5.6

[0072] In comparison with the ballasted-floc physicochemical decanter, the facility of the invention offers a significant improvement for the elimination of suspended matter (MES), of oxidizable organic pollution and of biodegradable carbonated organic pollution.

2. Mass Balance of the Facility of the Invention

[0073] FIG. 2 and table 3 below illustrate a mass balance of the facility of the invention. The balance is produced for a conventional European untreated water for which the MES value is 310 mg/L and the DBO.sub.5 value is 300 mg/L. The flow of untreated water entering a biological contact tank, the flow leaving said tank and entering a decanter, the recirculation flow leaving said decanter and entering the contact tank, the flow of treated water leaving said decanter, and the flow of sludge leaving said decanter, are numbered respectively as flows 1, 2, 3, 4 and 5.

TABLE-US-00003 TABLE 3 MES concentration DBO concentration Flow Flow rate g/L Mg/L 1 Q 0.3 300 2 107.5% XQ 2 195 3  7.5% XQ 25 4   99% XQ 0.02 30 5    1% XQ 25

[0074] The facility of the invention allows elimination of 90% of particulate pollution and biodegradable carbonated organic pollution.