Abstract:
A water treatment facility and method for treating effluents incorporating an input filter for removing bacterial contamination. The filter utilizes pipe and tube systems for distribution and drainage, which extend from both the inlet and outlets, which face each other at a spaced distance, and contain lengthwise perforations with filtration equipment therebetween. The water treatment apparatus utilizes a septic tank which includes a barrier, a waste water delivery pipe, an evacuation pipe for clean water, equipment for decantation of the heaviest matter at the bottom of the barrier and the surface accumulation of grease and light particles, anaerobic fermentation of the entrapped material, and protective equipment arranged to prevent plugging.

Description:
The present invention deals with a filter for removing bacterial contamination, and, a facility and treatment method for liquid waste filtration. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The standard P16-603 reference DTU 64.1 dated December 1992, published and distributed by the French Standardization Association (AFNOR), entitled “Implementation of private sewage disposal equipment”, describes the implementation rules relating to private sewage disposal equipment such as domestic wastewater treatment from dwellings of one to ten principal rooms. The clauses of this standard, concern the treatment systems composed of an anaerobic pretreatment septic tank and a reconstituted in-place ground spreading system or a sand filtration system. 
     This standard particularly specifies that sand filters must contain washed siliceous sand which is stable in water, having a size-distribution curve which conforms to a certain grading range represented in FIG.  9 . 
     This standard also specifies that sand filters size must not be under 5 m 2  /equivalent inhabitant. 
     Dimensions of such sand filters remain large, which causes numerous drawbacks or constraints: large required ground surface, elevated cost, etc. 
     SUMMARY OF THE INVENTION 
     A filter is proposed for wastewater treatment, of a type which includes: 
     an inlet for the water to be treated; 
     an outlet for the treated water; 
     filtration equipment between the inlet and the outlet, characterized by the fact that the filtration equipment includes: 
     two pipe and tube systems, respectively for distribution and drainage, each located at the inlet and the outlet, placed mutually facing and spaced apart from each other, and containing perforations distributed lengthwise along their transverse walls; 
     filtration equipment between the two systems; distribution equipment connected with the network of distribution pipes, meant to ensure the diffusion of water to be treated toward the filtration equipment. 
     A water tratment septic tank is proposed which includes a barrier, a delivery pipe for wastewater, an evacuation pipe for clean water towards a spreading system, equipment for decantation of the heaviest matter at the bottom of the barrier, and of surface accumulation of grease and light particles, and of at least partial liquefaction of these materials by anaerobic fermentation, protective equipment for the spreading system to prevent plugging, integrated in the barrier, characterized by the fact that the equipment of settling, liquefaction, and protection are placed in a single compartment of the barrier; the delivery pipe forms an elbow the downward-sloping section of which leads towards an inlet end wall of the barrier and the outlet of which is opened towards the top; it includes a first deflector placed in the barrier transversely, at least approximately at outlet level, vertically inclined; a vertical partition, situated partly above and partly below the free surface S, at least approximately at the base of the lower edge of a second deflector containing an inclined lower section, is associated with an evacuation pipe; the vertical partition, the second deflector and the lateral partitions define a passage for clear water, containing an inlet which is approximately vertical, an elbow, and an outlet cover connected to the evacuation pipe. 
     According to the first aspect, the invention concerns a filter for removing bacterial contamination of effluents, the filtration equipment of which contains: 
     two systems of pipes, for distribution and drainage respectively, each one placed at the filter inlet and outlet, placed approximately facing and distanced from each other, and containing perforations distributed lengthwise in their transverse walls, 
     filtration equipment placed between the two systems, in the form of at least one layer of sand the size distribution curve of which is in compliance with the range defined in AFNOR DTU no. 64-1, Ref. P 16-603, able to ensure the removal of a substantial part of the bacterial contamination of the effluent passing through the filter, and 
     distribution equipment connected to the distribution pipes system, in order to ensure delivery of the water to be treated towards the filtration equipment. 
     According to other characteristics of the filter, it is between 0.2 and 0.9 m 2 /equivalent inhabitant in dimension. 
     The distribution pipes system is adjacent to the first surface of the granular filtration layer, notably located on the outside. 
     The drainage pipe network is next to a second surface of the granular filtration layer, notably located in a drainage layer situated below the granular filtration layer, the filtration layer and the drainage layer being separated by a synthetic drainage mat weighing around 100 g/m 2 . 
     The filter also contains a protection layer, in which is located the network of distribution pipes, and which is adjacent to the granular filtration layer. 
     The distribution pipes system contains at least one layer of several pipes spaced apart from each other transversely, and connected to each other especially near the inlet. The perforations in the distribution pipes system are distributed approximately perpendicular to the depth of the granular filtration layer. 
     The distribution pipes contain overflow openings distributed lengthwise, opposite the first surface of the granular filtration layer. 
     The distribution pipes are respectively covered with protective equipment—such as an overturned gutter—meant to avoid any clogging of perforations and/or overflow openings without preventing the distribution of effluents. 
     One of the means of distribution is in the form of a layer for the absorption and diffusion of effluents, placed between the distribution pipes system and the filtration equipment. 
     One of the means of distribution is in the form of bands for the absorption and diffusion of water, placed between the distribution pipes system and the filtration equipment. These bands appear in the form of a drainage layer and a fine filtration layer, successively, in the direction of flow. The distribution pipes are placed in the median part of these bands. 
     The drainage system contains at least one layer of several pipes, transversely spaced in relation to each other, and connected with each other especially near the filter outlet. 
     The filter also contains an outer casing which houses the two systems of distribution and drainage pipes respectively, the filtration equipment between the two systems, and the distribution equipment connected to the distribution network. This casing contains an inlet and an outlet. The casing is in the shape of a U the opening of which is notably closed. Such a filter may also contain a sequential effluent injection device, such as an electric pump, a rocking bucket or a siphon primed by a pressure cover. 
     According to the second aspect, the invention concerns a treatment facility for domestic wastewater containing from upstream to downstream: 
     a septic tank for all kinds of water; 
     a pre-filter covered with pozzolano or an equivalent material; 
     the first filter containing a filtration equipment of a minimum one granular filtration layer with a porosity between around 0.2 and 5 mm, ensuring the removal of a substantial part of organic matter from the effluents; and 
     the second filter identical to the one described above. 
     According to other characteristics of the facility, the first and second filters present a similar or analogous general structure. 
     The first filter is between 0.2 and 0.9 m 2 /equivalent inhabitant in dimension. The septic tank for all waters is between 0.2 and 1 m 3 /equivalent per inhabitant in dimension. 
     The septic tank includes a barrier, a delivery pipe for liquid waste, an evacuation pipe for clear water towards the first filter, and equipment of decantation by deposit of the heaviest materials on the bottom of the barrier, and by surface accumulation of grease and light particles, and of at least partial liquefaction of these materials by anaerobic fermentation, and equipment of protection for the first and second filters, integrated in the barrier itself, to prevent their clogging. 
     The decantation, liquefaction, and protective equipment are located in a single compartment of the barrier. The delivery pipe forms an elbow the downhill section of which leads to the inlet edge wall of the barrier, and its outlet is opened towards the top. The septic tank contains a first deflector transversely placed in the barrier, approximately at the level of the outlet, extending over all, or most of the width of the barrier, vertically inclined at 35 to 45 degrees from the bottom to the cover, and from the inlet edge walls towards the outlet edge walls, the first deflector&#39;s function being to improve decantation and to limit the progress of turbulence to the bottom of the barrier. To the evacuation pipe is connected a vertical partition, located partly above, partly below the free surface, approximately in line with the lower edge of the second deflector. The latter contains a lower section inclined from the bottom to the cover, and from the inlet edge walls to the outlet edge walls. The vertical partition, the second deflector, and the lateral partitions create a passage for clear water, containing an approximately vertical inlet opening, an elbow, and an outlet opening connected with the evacuation pipe. 
     The upper section of the septic tank&#39;s delivery pipe is located at a higher level than the one of the evacuation pipe. 
     The barrier of the septic tank includes two identical or approximately similar parts: a lower shell and an upper shell, each having a trapezoidal shape in right transverse and longitudinal section, the two shells being connected to each other by their large common base. 
     The delivery pipe, the evacuation pipe, as well as the vertical partition and the second deflector are entirely located in the upper shell, which contains in its cover two inspection holes, while the first deflector is located at least partially in the upper shell and near the base. 
     The sizes of the first deflector, the second deflector and the vertical partition allows their passage through an inspection port. 
     The lower edge of the first deflector determines the upper acceptable level of accumulated sludge at the bottom of the barrier. 
     The exchange surface between the accumulated sludge at the bottom of the barrier and the floating liquid is approximately equal to all the surface of the barrier&#39;s horizontal section at the level of the lower edge of the first deflector or of the upper surface of sludge. 
     In the septic tank there is a continuous and permanent free communication between the evacuation pipe and the delivery pipe for the passage of air, due to openings designated in the upper portion of the evacuation and delivery pipes. 
     The first deflector, the second deflector, and the vertical partition are, besides the delivery and evacuation pipes, the only parts placed on the inside of the septic tank&#39;s barrier. 
     The barrier forms a single compartment, not separated in two distinct compartments by a transverse partition. 
     According to a third aspect, the invention concerns a domestic wastewater treatment , in which, successively: 
     the liquid waste to be treated is sent into an all-water septic tank; 
     then into a first filter which ensures removal of a substantial part of the organic matter; 
     then, finally, into a second filter which ensures retention of a substantial part of the bacterial contamination. 
     According to other characteristics, the waters leaving the second filter have: 
     a chemical oxygen demand less than 30 mg O 2 /l; 
     a quantity of suspended solids less than 6 mg/l; 
     a total quantity of KJELDAHL nitrogen less than 2 mg of nitrogen per liter; 
     nitrite quantities equal or close to 0; 
     nitrate quantities less than 60 mg of nitrogen per liter; 
     a quantity less than 1/ml for fecal coliforms; 
     a quantity less than 1/ml for fecal streptococcus. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The invention will be well understood through the description which follows, in the form of a possible realization and referring to the annexed drawings, in which: 
     FIG. 1 is a schematic view which illustrates both the elements making up a facility and the required steps for a treatment method for domestic liquid waste according to the invention; 
     FIG. 2 is a schematic view in vertical and longitudinal section of a septic tank according to the invention&#39;s facility and method; 
     FIG. 3 is a schematic view in transverse and vertical section according to line  33  of FIG. 2; 
     FIG. 4 is a top view of a filter for the removal of bacterial contamination of effluents according to the invention or for the removal of effluents&#39; organic matter; this or these filters are part of the facility in FIG. 1 or are implemented in the corresponding method; 
     FIG. 5 is a bottom view of the filter shown in FIG. 4; 
     FIG. 6 is a sectional view of the filter following line A-A 1  of FIGS. 4 and 5; 
     FIG. 7 is a perspective view of a distribution pipe in the distribution pipes system of a filter according to the invention; 
     FIG. 8 is a partial sectional view of a distribution pipe covered with a protective equipment, attached to the distribution equipment; 
     FIG. 9 is a representation of the grading range of the filter sand to be used into the sand filters, according to the standard P16-603 references DTU 64.1 of December 1992, edited and distributed by the French Standardization Association (AFNOR). 
     [FIG.  9 —callouts] 
     A. Slate 
     B. Lime 
     C. Sand 
     D. Fine 
     E. Medium 
     F. Large 
     G. Gravel 
     H. Fine 
     I. Large 
     J. % passing 
     K. % retained 
     L. Particle dimensions (mm) 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A facility for domestic wastewater treatment according to the invention includes, from upstream to downstream: 
     an all-water septic tank  1 ; 
     a pre-filter  2  covered with pouzzolano or equivalent material; 
     a first filter  3  containing filtration equipment in the form of at least one granular filtration layer of a porosity between about 0.2 and 5 mm, ensuring removal of a substantial part of the effluents&#39; organic matter; and 
     a second filter  4  for removal of the effluents&#39; bacterial contamination. 
     The facility also includes: 
     a delivery pipe  5  for liquid waste in the septic tank  1 ; 
     a pipe  6  between the outlet of the septic tank  1  and the inlet of the pre-filter  2 ; 
     a pipe  7  between the pre-filter  2  outlet and the first filter  3  inlet; 
     a pipe  8  between the first filter  3  outlet and the second filter  4  inlet; 
     and finally, an evacuation pipe  9  at the outlet of the second filter  4 . 
     The second filter  4  will now be more specifically described. 
     This filter is meant to be incorporated either in a facility as above described, or in any other facility, for which this filter  4  would be adapted. 
     The filter  4  contains an inlet  10  for water to be treated connected to the pipe  8 , an outlet  11  of treated water connected to the pipe  9 , and a filtration equipment between the inlet  10  and the outlet  11 . 
     The filter  4  is fed with the water to be treated, through its inlet  10 , through (in the represented realization) a siphon  12  which can be primed by a pressure cover located in a supply tub  12   a . The siphon  12  receives the water to be treated from the first filter  3 . 
     In the realization example considered in FIG. 4, the primable siphon  12  is located in the supply tub  12   a  and contained in the filter  4 . The filter  4  can be separated from the siphon  12 , however. The inlet of the filter thus corresponds here to the inlet  10   a  of the siphon  12  located in the supply tub  12   a . This siphon  12  thus feeds the inlet  10  of the filter  4 . 
     This primable siphon  12  causes the filter  4  to be supplied with water quantities to be treated. The supply no longer being continuous, the priming regulation of the siphon  12  can be done in such a way that the filter  4  only receives a quantity of water to be treated when the preceding amount has already been treated. This allows to obtain a better distribution of waters in the filter as well as a better purification. 
     According to other realization possibilities, the replacement of the siphon  12  with a rocking trough or an electric pump with a detector of high and low levels may be envisioned—or more generally with an injection device of the effluent, sequential or not. 
     In the treatment system under consideration, the filter  4  is placed approximately horizontal and at ground level. It can however be partially or completely buried. 
     The filtration equipment of the filter  4  contains: 
     two systems of pipes  13 ,  14  respectively for distribution and drainage, connected to the inlet  10  and the outlet  11  respectively, placed approximately facing and apart from one another, and containing perforations  15  distributed lengthwise in their transverse walls, 
     a filtration equipment  16  placed between the two systems  13  and  14 , and 
     an equipment of distribution  17  connected to the distribution pipes system  13  and meant to ensure delivery of the water to be treated to the filtration equipment  16 . 
     The filtration equipment  16  is in the form of a granular filtration layer. This granular filtration layer  16  is composed at least of one layer of siliceous washed sand, stable in water. 
     This sand has a size-distribution curve in accordance with the range represented in FIG. 9, to which one should refer specifically for this purpose. 
     The depth of the layer is between 0.5 and 1 m. It should be preferably equal to or around 60 cm. 
     The distribution pipes system  13  is adjacent to a first surface  16   a  of the granular filtration layer  16 . It can be located outside or inside of this granular filtration layer  16 . 
     Into the example of the considered realization represented in FIG. 6, the distribution pipes system  13  is positioned outside of the granular filtration layer  16 . 
     In another hand, this distribution pipes system  13  contains vents which allow aeration. 
     Also, the drainage pipes system  14  is adjacent to a second surface  16   b  of the granular filtration layer  16 . It can also be located either outside or inside the granular filtration layer  16 . In the realization example considered in FIG. 6, the drainage pipes system  14  is placed in a drainage layer  17   b  located under the granular filtration layer  16 , and the filtration layer and the drainage layer are separated by a synthetic drainage mat weighing about 100 g/m 2 . 
     The distribution pipes system  13  contains at least one layer of several distribution pipes  13   a  spaced transversely in relation and connected to each other, specifically near the inlet  10  of the filter  4 . 
     According to the form of realization represented in FIG. 4, the distribution pipes  13   a  are connected to each other by communication pipes  13   b  placed transversely in relation to the longitudinal axis  13   c  of the distribution pipes  13   a  at their ends  13   d ,  13   e . The distribution pipes  13   a  are preferably made of PVC and have a diameter of about 40 mm. 
     The distance d between the longitudinal axes  13   c  of the distribution pipes  13   a  is preferably about 1 m. 
     The drainage pipes system  14  contains at least one layer of several drainage pipes  14   a  transversely spaced in relation and connected to each other near the outlet  11  of the filter  4 . 
     In the realization example shown in FIG. 5, the network of drainage pipes  14  has the same configuration as the distribution pipes system  13 . The drainage pipes  14   a  are therefore connected to each other by communication pipes  14   b  at the ends  14   d ,  14   e  of the drainage pipes  14   a  transversely in relation to the longitudinal axis  14   c  of the drainage pipes  14   a . The communication pipes  14   b  located at the end  14   e  of the drainage pipes  14   a  are connected to the outlet  11  of the filter  4 . 
     The drainage pipes  14   a  are also preferably made of PVC and have a diameter of about 100 mm. 
     The distance d separating the axes  14   b  of the drainage pipes  14   a  is here the same as in the case of the distribution pipes system  13 . 
     The distribution equipment  17  associated with the distribution pipes system  13  is in the form of a layer of water absorption and diffusion between the distribution pipes system  13  and the filtration equipment  16 , meaning the granular filtration layer  16 . 
     In one form of the invention&#39;s realization, the distribution equipment  17  is in the form of water absorption and diffusion bands  17   a , preferably around 50 cm wide, these bands  17   a  being situated between the distribution pipes system  13  and the filtration equipment  16 . 
     This layer or these bands  17   a  of absorption and diffusion include a synthetic drainage mat weighing about 750 g/m 2  and can be in the form of a drainage layer  17   b  and a thin filtration layer  17   c  preferably made of polypropylene, in the direction of water diffusion. 
     In the realization example being considered, the distribution pipes  13   a  are placed in the median portion of the absorption and diffusion bands  17   a.    
     The distribution pipes  13   a  contain perforations  15  distributed lengthwise in their transverse walls and arranged approximately perpendicular to the depth  16   c  of the granular filtration layer  16 . 
     According to FIG. 7, the perforations  15  are cylindrical with a diameter of at least 3 mm in order not to risk becoming plugged. 
     These perforations  15  are distributed lengthwise at intervals of about 30 cm, which allows a good distribution of water by using all of the perforations  15  present in the distribution pipes  13   a.    
     To maintain a good distribution of water in case of a heavy flow rate, the distribution pipes  13   a  also contain overflow openings  18 , also spaced lengthwise, but opposite to the first surface  16   a  of the granular filtration layer  16 . These overflow openings  18  preferably have a diameter of around 10 mm and are placed in alternation with the perforations  15 . 
     In case of heavy inlet flow rate, passage of excess water is thus made through these overflow openings  18 . The entire surface of the filter  4  is thus used, no matter what the inlet flow rate. 
     According to one form of realization of the filter  4  according to the invention, represented in FIG. 8, the distribution pipes  13   a  are respectively covered with a equipment of protection  19  meant to avoid obstruction of the perforations  15  or the overflow openings  18 . This equipment of protection  19  is in the form of an overturned gutter of a diameter greater than the distribution pipe  13   a , thus not hampering the proper functioning of the perforations  15  and the overflow openings  18 . 
     In the realization form shown in FIG. 8, the overturned gutters  19  have a diameter of around 100 mm. 
     To protect the granular filtration layer  16 , it is possible to preview a protective layer  20  in which the distribution pipes system  13  is found. This protective layer  20  is adjacent to the granular filtration layer  16  at its first surface  16   a  and is preferably a layer of washed gravel, about 5 to 10 cm thick. 
     Finally, the filter  4  includes an exterior casing  21  in which the two systems of distribution  13  and drainage  14  pipes respectively are housed, as well as the filtration equipment  16  between the two systems  13  and  14  and the equipment of distribution  17  associated with the distribution pipes system  13 . This casing includes the inlet  10  and the outlet  11 . 
     In the realization example shown in FIG. 5, the casing  21  has the shape of a U, but it can also have the shape of a U the opening of which is closed. 
     Furthermore, according to another realization, this casing  21  can be replaced with a concrete pit with waterproof walls, realized on the spot. 
     The second filter  4  described above is compact, meaning that its dimensions are smaller than those recommended in actual practice. 
     The second filter  4  has dimensions of between 0.2 and 0.9 m 2 /equivalent inhabitant, specifically around 0.6 m 2 /equivalent inhabitant. 
     The first filter  3  may have a similar or analogous structure to the second filter  4 . 
     According to the fact, it is also compact, its dimensions are between 0.2 and 0.9 and specifically around 0.6 m 2 /inhabitant. 
     Instead and in place of sand as component material of the filtration layer, such as described in the second filter  4 , the first filter  3  contains, in the realization considered here, granules of zeolite, giving a size-distribution between about 0.1 and 10 mm. 
     For example, this layer is made up, either entirely of granular material between 2 and 5 mm, or of two sub-layers, the upper one with 2 to 5 mm granules and the lower one with 0.2 to 2 mm granules. Due to the presence of inter-granular interstices, the zeolite granules allow excellent air circulation and thus good growth of purifying microorganisms. The zeolite fixes well the purifying biomass, and thus allows a good rate of elimination of the polluting carbonized load of effluents. 
     In addition, the zeolite is made up of microporous grains, allowing a gravitational flow of water between the grains in case of heavy flow rate, and a capillary flow from one grain to the next, in case of light flow rate. 
     Finally, the zeolite possesses valuable elimination properties for nitrogenous pollution. 
     Furthermore, because of the growth of purifying microorganisms in the first filter  3 , the bands&#39; synthetic drainage mat progressively loses part of its permeability and progressively diffuses the water to be treated to the granular filter bed  16 , improving the distribution of water at the surface. 
     We will now describe more specifically a particular form of realization of the septic tank  1 , the performance of which has been recorded, along with the pre-filter  2  and the two successive filters  3  and  4 . 
     The septic tank  1  includes a rigid barrier  22 ; a delivery pipe  5  for wastewater; and an evacuation pipe  6  to the pre-filter  2 . 
     The septic tank  1  also includes an equipment  23  of settling of the heaviest matter or sludge B by deposit at the bottom  24  of the barrier  22  and of accumulation of grease and light particles G at the free surface S; and of at least partial liquefaction of these materials B, G by anaerobic fermentation. 
     The septic tank  1  finally includes equipment of protection  19  of the part of the facility placed further down (pre-filter  2 , filters  3  and  4 ), integrated in the barrier  1 , in order to prevent blockage. 
     The equipment  23  of decantation and liquefaction, and the equipment  19  of protection are placed in a single area of the barrier  22 . 
     The barrier  22  includes two identical or approximately similar parts, made up of a lower shell  25   a  and an upper shell  25   b . Each shell  25   a  and  25   b  has, in its right longitudinal and right transverse section, a generally trapezoidal isosceles form. The two shells  25   a ,  25   b  are connected to each other at their large open common base  26 . 
     The lower shell  25   a  includes, besides the bottom  24  which makes a small base, two edge walls of intake  27   a  and outlet  28   a  and two lateral walls  29   a ,  30   a , all inclined at about a 30° angle from the vertical. 
     The upper shell  25   b  includes an upper cover  31  forming a small base which is flat and horizontal, two edge walls of intake  27   b  and outlet  28   b  and two lateral walls  29   b ,  30   b . The edge  27   b ,  28   b  and lateral  29   b ,  30   b  walls are inclined from the vertical in the same way as the edge  27   a ,  28   a  and lateral  29   a ,  30   a  walls. The walls  27   b ,  28   b ,  29   b ,  30   b  of the shell  25   b  are connected to the walls  27   a ,  28   a ,  29   a ,  30   a  and the shell  25   a  at the base  26 . The base  26  is thus located halfway between the bottom  24  and the cover  31 . 
     On the cover  31 , space will be allowed for two inspection windows  32  closed by covers  33 . The inspection windows  32  are placed at the two edges of the cover  31  near the edge walls  27   b ,  28   b.    
     The delivery pipe  5  forms a double bend folded on itself, including an upstream horizontal section  34 , an intermediate vertical section  35  and a downstream section  36 , also horizontal. 
     The upstram section  34  crosses the intake edge wall  27   b  near the cover  31 . The downstream section  36  leads overall toward the edge wall  27   a ,  27   b  of the barrier  22  in such a way that the effluents coming from the delivery pipe  5  are directed to this wall. 
     The outlet  37  of the downstream section  36  is cut in the form of a gutter so as to be open toward the top, so that the effluents are also directed toward the top in the direction of the arrows F 1  (FIG.  2 ). 
     The septic tank  1  also contains a first deflector  38  placed transversely in the barrier  22 , at least approximately at the level of the outlet  37 , and partially constituting the equipment  23 . The first deflector  38  stretches over all or at least a substantial part of the width of the barrier  22 , meaning between the lateral walls  29   a ,  29   b  on the one hand and  30   a ,  30   b  on the other. The function of the first deflector  38  is to improve decantation and to limit the progression of turbulence toward the bottom  24  of the barrier  22 . This process induces a water circulation according to the arrows F 2  (FIG.  2 ). In one form of realization, the first deflector  38  is especially inclined 35° to 55° from the vertical, and particularly around 45_, from the bottom  24  to the cover  31  and from the intake edge walls  27   a ,  27   b  to the outlet edge walls  28   a ,  28   b.    
     If H is representing the water depth in the barrier, this depth being defined by the position of the evacuation pipe  6 , as one will see later, the center of the first deflector  38  is located between 0.65 H and 0.75 H and particularly at around 0.70 H from the bottom  24 . 
     The lower edge  39  of the first deflector  38  is located between 0.5 H and 0.6 H and particularly at around 0.55 H from the bottom  24 . The upper edge  40  of the first deflector  38  is located between 0.75 H and 0.85 H and particularly around 0.80 H from the bottom  24 . 
     In the form of realization shown in FIG. 2, the first deflector  38  is located at about one-third of the length of the barrier  22  (i.e. between the edge walls  27   a ,  27   b  and  28   a ,  28   b ) starting from the intake edge walls  27   a ,  27   b . More generally, and taking into account a total possible volume of the upper septic tank, it is preferable the first deflector  38  is not positionned too far from the edge walls  27   a ,  27   b . For this reason, the first deflector  38  is usually located at a distance equal to or around 5.5 to 7.7 times and preferably around 6 to 7 times the diameter of the delivery pipe  5  from the junction of the two walls  27   a ,  27   b . Or, as a variant, this distance is equal to or around 0.6 H. 
     The first deflector  38  thus defined leaves a large lower passage  41  between its lower edge  39  and the bottom  24 , on the one hand, and a smaller upper passage  42  between its upper edge  40  and the free surface S, on the other. The lower passage  41  allows transit of heavy matter or sludge B, while the upper passage  42  allows passage of grease and light particles G. 
     The first deflector  38  can be fixed to the lateral walls  29   a ,  29   b ,  30   a ,  30   b  of the barrier  22  at its two lateral edges. 
     The evacuation pipe  6  placed horizontally defines the level of the free surface S. The horizontal upper section  34  of the delivery pipe  5  is located above the free surface S, in order to avoid any backflow of effluents through the delivery pipe  5 . 
     The free surface S is located at a distance H from the bottom  24  which is around 0.7 to 0.9 K and preferably equal to or about 0.8 K, K being the distance between the bottom  24  and the cover  31 . 
     A vertical partition  43  is associated with the evacuation pipe  6  and is located partly above and partly below the free surface S. For example, the lower edge  44  of the vertical partition  43  is located between 0.10 H and 0.20 H and particularly is equal to or near 0.15 H from the free surface S. The free surface S is itself located approximately at mid-height of the partition  43 . 
     A second deflector  45  is also associated with the evacuation pipe  6 , containing a lower section  45   a  inclined from the bottom  24  to the cover  31  from the edge walls  27   a ,  27   b  to the edge walls  28   a ,  28   b.    
     The vertical partition  43  is located at least approximately at the base of the lower edge  46  of the second deflector  45 . The vertical partition  43  and the second deflector  45  define a passage  47  for clear water. This passage  47  includes, at least approximately vertical, an intake opening limited by the lower edges  44 ,  46  of the partition  43  and the second deflector  45 , then a bend bounded by the lower section  45   a  to deny the passage of floating matter, then an outlet opening in a vertical section connected to the evacuation pipe  6 . Lateral edge partitions  48  (FIG. 3) rigidly connect the vertical partition  43  and the second deflector  45 . These vertical lateral partitions  48  have a trapezoidal form, the small base of which corresponds with the upper section  45   b . Its large base is at a distance between the upper edge of the partition  43  and the lower edge  46  of the deflector  45 , and the width of which is the distance between the partition  43  and the upper section  45   c . The partitions  48  in combination with the partition  43  and the second deflector  45  form a sort of box in which water cannot enter except through the passage  47 . 
     A screen  49  is horizontally placed in the passage  47  near the outlet, under the free surface S. Its position is such that it is easily accessible from the inspection window  32  placed at the base. It is mounted to be removable. 
     Another vertical screen  50 , for extra protection, is placed in the passage  47  at the intake, lengthening the partition  43  toward the bottom to the edge  46 . The debris stopped by the screen  50  can settle or freely float as soon as the stream in the septic tank stops. 
     The vertical partition  43  and the second deflector  45  have an identical or similar width which can be limited to around 2.5 to 6 times and especially to around 4 times the diameter of the evacuation pipe  6  (FIG.  3 ). 
     The distance between the lower free edges  44 ,  46  of the partition  43  and the second deflector  45 , i.e., the height of the intake opening of the passage  47 , can be between 0.9 P and 1.1 P and particularly equal or near P, P being the submerged depth of the vertical partition  43 . This distance can also be between around 0.10 H and 0.20 H, and particularly be equal or near 0.15 H. 
     The lower free edge  44  of the partition  43  is located approximately at the same level as a barrier  45   b  separating the lower section  45   a  of the second deflector  45  from an upper section  45   c  which is at least approximately vertical and connected to the evacuation pipe  6  and even projecting above the latter, in a section  45   d.    
     The distance between the upper section  45   c  and the vertical partition  43  can be around the same size as the height of the intake opening of the passage  47 , especially between around 1 and 1.5 P or equal to or about 0.2 H. 
     The delivery pipe  5  and the evacuation pipe  6 , as well as the vertical partition  43  and the second deflector  45  are completely located in the upper shell  25   b  and the first deflector  38  is situated at least partially in the upper shell  25   b  and near the base  26 . 
     The first deflector  38 , the second deflector  45 , and the partition  43  are of a limited size allowing their passage through the observation port  32 . The lower edge  39  of the first deflector  38  determines the admissible upper level for the sludge accumulated on the bottom  24  of the barrier  22 . 
     The exchange surface between the sludge B accumulated on the bottom  24  of the barrier  22  and the floating liquid E is approximately equal to the total surface of the horizontal section of the barrier  22  at the level of the lower edge  39  of the first deflector  38  or at the level of the upper surface of sludge B. 
     An opening  51  drilled through the upper part of the delivery pipe  5  allows a free, continuous and permanent communication for the air passage necessary to the functioning of the all-water septic tank, from the evacuation pipe  6  which is not immersed into the liquid contained in the tank and the delivery pipe  5 . 
     The first deflector  38 , the second deflector  45  and the vertical partition  43  are, besides the delivery and evacuation pipes  5 ,  6 , the only mechanisms located inside the barrier  22 . The barrier  22  thus forms a sole compartment not separated into two totally distinct compartments by a vertical partition  43 .