FR2862632A1 - Pre-treatment tank for domestic waste water comprises pre-filtration unit, ventilation and inspection port and slitted lower wall with decantation element - Google Patents

Abstract

A pre-treatment tank (1) with an inlet (2) and outlet (3), a manhole and a pre-filtration unit (4), made in the form of a cylindrical pot with outlet holes (8) in its side wall, an upper front wall (6) with a ventilation and inspection port (9), and a slit lower front wall (7) extended on the other side of its slit (12) by a decantation element (13), is new. A pre-treatment tank (1) with an inlet (2) and outlet (3), a manhole and a pre-filtration unit (4), made in the form of a cylindrical pot with outlet holes (8) in its side wall, an upper front wall (6) with a ventilation and inspection port (9), and a slit lower front wall (7) extended on the other side of its slit (12) by a decantation element (13). The decantation element projects obliquely downwards beyond the pre-filtration unit towards the middle of the tank without contact with the cap or digestion zones; it is made from a series of channels or parallel tubes designed to increase the area of the decantation surface for sludge and suspended materials.

Description

The present invention relates to a pre-treatment tank for wastewater

  domestic collected at the exit of an individual dwelling or a small community equipped with a prefiltration device.

  Wastewater discharged by individuals or communities of less than 50 population equivalents typically contains a significant amount of grease and sludge and various solids that must be removed before reuse.

  For this purpose, the regulations in force require downstream individual dwellings or grouped channels consisting of a pretreatment and a treatment device.

  The pretreatment is most often provided by so-called "all-water pits" which make it possible to obtain a simple and inexpensive preliminary purification of the discharged water.

  These are tanks whose capacity is a function of the quantity of water discharged and is at least 3 m3 for a dwelling of 5 main rooms.

  These tanks are conventionally equipped at their upper part with an inlet pipe for the water to be treated, a drain pipe for purified water and a manhole for monitoring and cleaning the tank, which must intervene at least every four years.

  Due to its volume and shape, in such a tank there appears a stable stratification comprising vertically a median tranquilization zone containing clarified waters, on the one hand surmounted by a hat zone in which fats and floating elements collect, and on the other hand, overcoming a bottom digestion zone of the tank in which sludge and various suspended solids separated from these waters are collected by gravity settling.

  For such a tank to operate satisfactorily, it is of course necessary that the orifice of the discharge pipe is located in the central zone of the tank, so as to avoid as much as possible the evacuation towards the tank. outside of water contaminated with grease or sludge.

  To improve the performance of such purification tanks, it has already been proposed to equip them with prefiltration devices placed at the level of the manhole and provided with at least one outlet orifice fitted to the tubing. evacuation so that the wastewater introduced into the tank must pass into this pre-filtration device, before their evacuation to the network downstream.

  Such devices are generally constituted by housings or baskets with a capacity of 50 liters loaded with filamentary elements, for example pozzolan.

  These pre-filtration devices have a range of disadvantages related primarily to the presence of the filter element which is subject to rapid clogging, related to a delicate maintenance due to the staining generated and the consequent weight of this load that it should be replaced periodically.

  It has also already been proposed to mount sewage treatment tanks out of prefiltration devices equipped with removable lamellar or tubular filter elements.

  These are easier maintenance devices but still requiring the handling of a material soiled with faeces, fats, etc.

  The object of the invention is to remedy these inconve-nients.

  For this purpose, the invention relates to a domestic wastewater pre-treatment tank of the aforementioned type equipped with a prefiltration device fixed on the neck of the manhole thereof and provided with at least one outlet orifice. fitted to the sewage pipe.

  Such a tank is characterized in that the prefiltration device is formed by a preferably one-piece element consisting of a pre-filter body in the form of a pot, in particular a substantially cylindrical container comprising: a side wall in which the outlet orifice is pierced; an upper end wall pierced with a ventilation and observation opening; and a slotted bottom wall extending to the right of the slot by a settling member extending obliquely downward outside the prefilter body, into the middle zone of the tank, without contact with the cap area nor with the digestion zone of the bottom of the tank.

  The prefiltration device equipping the tank according to the invention does not contain a filter element. It allows a direct visual observation of the level of floating materials contained in the hat area, as well as the degree of clogging (and thus the increase in load) of the tank, thanks to the presence of the ventilation opening and 'observation.

  In addition, this opening ensures a free flow of air to the inner part of the tank. This configuration allows a water jet cleaning without the need to disassemble the prefiltration device.

  According to a preferred feature of the invention, the settling element is constituted by a lamellar element equipped with a series of channels or parallel tubes for increasing the settling surface of the sludge and suspended solids contained in the waters to be separated. treat.

  This lamellar settling element is therefore a kind of suspended matter trap to limit the risk of clogging in the network located downstream of the tank.

  According to the invention, it is essential to choose the inclination, the geometry and the dimensions of the lamellar settling element so as to ensure the maintenance of a laminar flow, that is to say the respect of a Reynolds number less than 2400, regardless of the flow of water entering the pit.

  Maintaining such a regime makes it possible to control the flow of water through the tank and thus to ensure optimum operation of it.

  The dimensions of the settling element also depend on parameters related to the installation, in particular the peak flow rate thereof, the maximum size of the elements to be decanted, and in addition the need to maintain the speed of the settling element. decantation below a certain limit which is generally 8 m per hour.

  According to another characteristic of the invention, the upper front wall of the prefilter body is surrounded by a collar for fixing it to the neck of the manhole of the tank.

  For this purpose this collar can advantageously be equipped on its outer surface with beads for locking the prefiltration body on the manhole of the tank.

  It should be noted that this collar can be cut if necessary to allow its adjustment to different neck diameters.

  The invention also relates to a prefiltration device for a tank of the aforementioned type.

  Such a prefiltration device is characterized in that it is formed by a preferably one-piece element consisting of a prefilter body in the form of a substantially cylindrical pot including: a side wall in which is pierced at least one water outlet orifice; clean; an upper front wall pierced with a ventilation opening and observation; and a slotted bottom wall extending to the right of the slot 10 by a settling member extending obliquely outside the prefilter body.

  The characteristics of the pretreatment vessel as well as the prefiltration device which are the subject of the invention will be described in more detail with reference to the appended drawings, in which: FIG. 1 is a partial cutaway view of a pre-treatment tank equipped with a prefiltration device; Figure 2 is a perspective view of the prefiltration device; Figure 3 is a detailed view of Figure 1 at the prefiltration device on which are schematically the paths of water and suspended solids.

  According to FIG. 1, the pretreatment tank 1 is equipped at its upper part with an inlet pipe 2 for the water to be treated and a drain pipe 3 for purified water as well as a manhole on the collar of which is fixed a prefiltration device 4.

  According to FIGS. 2 and 3, the prefiltration device 4 is formed by a one-piece element constituted by a substantially cylindrical pre-filter body comprising a side wall 5, an upper end wall 6 and a bottom end wall 7.

  The side wall 5 is pierced by a series of outlet orifices 8 which are fitted to the outlet pipe 3 of the vessel 1 so that the wastewater introduced into the latter through the inlet pipe 2 necessarily passes to the internal part of the cylindrical body 4 before their evacuation towards the outside by the tubing 3.

  The upper end wall 6 of the cylindrical body 4 is pierced by a ventilation and observation opening 9 and is surrounded by a flange 10 provided on its outer face with beads 11 allowing the locking of the cylindrical body 4 on the hole of man of the tank 1.

  According to FIGS. 1 and 2, the lower end wall 7 is pierced with a slot 12 allowing the introduction, according to the arrows A, of the water contained in the tank 1 at the internal part of the cylindrical body 4 and their evacuation towards the outside by the outlet orifices 8 and the evacuation pipe 3.

  The lower end wall 7 is also extended to the right of the slot 12 by a lamellar settling element 13 equipped with a series of parallel channels 14.

  According to FIGS. 1 and 3, the lamellar settling element 13 extends obliquely downward outside the cylindrical body 4 into the central zone of the vessel 1, ie in the zone of tranquilization clarified water located between a hatch zone in which the greases and floating elements collect, contained in the wastewater to be purified and a bottom digestion zone of the tank in which sludge and various suspended solids separated from these waters by settling.

  The inclination, the geometry and the dimensions of the lamellar settling element 13 are chosen so as to ensure the maintenance of a laminar flow within the vessel 1.

  The lamellar settling element 13 therefore constitutes a suspended matter trap which separates and migrates downwards into the digestion zone of the bottom of the tank according to arrows B.

Claims (6)

  1) Tank for pretreatment of domestic sewage collected at the exit of a single dwelling or group of such dwellings and equipped with an inlet pipe for the water to be treated, a drain pipe for the purified water , as well as a manhole on the collar of which is fixed a prefiltration device provided with at least one outlet port fitted to the discharge pipe so that the wastewater introduced into the tank must pass into the pre-filtration device before their evacuation to the outside, this tank being subdivided at its inner part in a median zone of clarified waters on the one hand surmounted by a hat area in which the greases and floating elements contained in the waters collect. used to purify, and on the other hand surmounting a bottom digestion zone of the tank in which the sludge and various suspended solids separated from these waters are separated by decantation, characterized in that the prefiltration device is formed by a preferably single-block element consisting of a substantially cylindrical pre-filter body (4) comprising: a side wall (5) in which the output (8); an upper end wall (6) pierced with a ventilation and observation opening (9); and a slotted lower end wall (7) extending in line with the slot (12) by a settling member (13) extending obliquely downwardly out of the prefilter body (4) into the middle zone of the tank (1), without contact with the hat area or with the digestion zone of the bottom of the tank.   2) tank according to claim 1, characterized in that the settling element (13) is constituted by a lamellar element equipped with a series of parallel channels or tubes (14) for increasing the sludge settling surface and suspended solids contained in the waters to be treated.   3) Tank according to claim 2, characterized in that the inclination, the geometry and the dimensions of the lamellar settling element (13) are chosen so as to ensure the maintenance of a laminar flow.   4) Tank according to any one of claims 1 to 3, characterized in that the upper end wall (6) of the prefilter body (4) is surrounded by a flange (10) for fixing it to the collar of the hole d man of the tank (1). 5) A tank according to claim 4, characterized in that the flange (10) is equipped on its outer surface with beads (11) permitting the locking of the prefilter body (4) on the manhole of the tank (1). 6) prefiltration device for a tank according to any one of claims 1 to 5, characterized in that it is formed by a preferably monobloc element consisting of a pot-shaped pre-filter body (4), in particular essentially cylinder comprising: a side wall (5) in which is pierced at least one outlet (8) purified water; an upper end wall (6) pierced with a ventilation and observation opening (9); and a slotted bottom end wall (7) extending in line with the slot (12) by a settling member (13) extending obliquely outside the prefilter body (4).