Septic tank

Abstract

The septic tank (300) comprises: - a tank (305) for retention and digestion of organic matter contained in effluents, - a longitudinal distribution point (309) for effluents, and - a lateral collection point (316) for effluents.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: SEPTIC TANK

[0003] TECHNICAL FIELD OF THE INVENTION

[0004] The present invention relates to a septic tank. It is applicable, in particular, to the field of domestic wastewater treatment.

[0005] STATE OF THE ART

[0006] The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise stated, it should not be assumed that any of the approaches described in this section constitutes prior art simply because of its inclusion in this section.

[0007] Septic tanks have the dual function of retaining solid matter contained in domestic effluents, by settling and flotation, and of liquefying this matter by anaerobic digestion.

[0008] A septic tank consists of a closed reservoir, an inlet, and an outlet. Typically, the outlet for liquid waste is positioned opposite the inlet for effluent, and this is for several reasons:

[0009] - The performance of settling in a septic tank is linked to the settling surface area - this surface area must be as large as possible in order to decrease the upward velocity of the materials and therefore retain as much material as possible; thus, by maximizing the distance between the inlet and outlet, the largest possible settling surface area is obtained.

[0010] - Hydraulic short circuits, which reduce effluent retention time, are minimized a priori when the inlet is as far from the outlet as possible, and

[0011] - Sludge theoretically accumulates more towards the inlet of the septic tank and the risk of sludge leaving the outlet is a priori minimized when the outlet is as far away from the inlet as possible.

[0012] Such a configuration A is shown in Figure 1, in which the following are represented:

[0013] - an inlet 101 for effluents,

[0014] - a reservoir 102 and - an outlet 103 for effluents positioned at the opposite end of the reservoir 102 relative to the inlet 101.

[0015] For various reasons, some septic tank configurations require the outlet to be located outside the septic tank, rather than at the point furthest from the effluent inlet. In such configurations, although the outlet is relocated, the point of collection for liquid effluent inside the tank remains furthest from the effluent inlet, and a system of internal piping is used to transport the effluent from the collection point to the outlet.

[0016] Such a configuration B is shown in Figure 1, in which the following are represented:

[0017] - an inlet 101 for effluents,

[0018] - a 102 tank,

[0019] - a collection point 104 for effluents positioned at the opposite end of the tank 102 from the inlet 101, and

[0020] - an outlet 103 for effluents connected to the collection point 104 by a pipe 105.

[0021] Such configurations are therefore limited to adding an internal hydraulic circuit to benefit from the advantages mentioned above while also benefiting from the flexibility of outlet positioning.

[0022] However, adding internal tubing to the pit presents a double disadvantage: it complicates the assembly, and above all, there is an increased risk of accumulation of materials and biomass in the tubing and therefore an increased risk of clogging of this tubing.

[0023] Existing systems often have a complex configuration with additional components, limiting installation flexibility. These systems offer standard, suboptimal performance, contrary to the widely accepted theory of optimizing septic tank treatment.

[0024] SUMMARY OF THE INVENTION

[0025] The present invention aims to remedy all or part of these drawbacks.

[0026] The inventors have surprisingly discovered that, contrary to widely held beliefs in septic tank design, positioning a collection point for liquid effluent laterally to the general flow of effluent into the tank improves septic tank performance. In other words, this discovery is counterintuitive given the creation of a hydraulic short circuit and the apparent minimization of the settling surface area.

[0027] To this end, the present invention relates to a septic tank, which comprises:

[0028] - a reservoir for the retention and digestion of organic matter contained in effluents,

[0029] - a longitudinal distribution point for effluents in the reservoir and

[0030] - a lateral collection point for liquid effluents positioned laterally in the tank.

[0031] As can be understood, the distribution point is associated with an effluent inlet positioned at the interface between the inside and outside of the tank. The inlet and the distribution point may be the same or close together, or the distribution point may be located away from the inlet.

[0032] As can be understood, the collection point is associated with an effluent outlet positioned at the interface between the inside and outside of the tank. The outlet and the collection point may be the same or close together, or the collection point may be located away from the outlet.

[0033] Thanks to these provisions, the septic tank that is the subject of the present invention allows for many operating configurations due to the more flexible positioning of an outlet connected to the collection point compared to a strict longitudinal inlet-outlet configuration as known in the prior art.

[0034] Beyond this flexibility in positioning, the septic tank described in the present invention offers better treatment performance than septic tanks with longitudinal inlet and outlet. Such performance improvements are illustrated in Figure 2. In particular, the hydraulic retention time is increased.

[0035] In particular embodiments, the retention tank has an elongated shape, with the longitudinal distribution point positioned near a short part of the tank and the lateral collection point positioned near a long part of the tank.

[0036] In certain embodiments, the retention tank has a parallelepiped shape, with the longitudinal distribution point positioned near a short face of the tank and the lateral collection point positioned near a long face of the tank. In other embodiments, the retention tank has a rectangular parallelepiped shape.

[0037] In particular embodiments, the lateral collection point is positioned at a distance from the longitudinal distribution point corresponding to at most 90% of the total length of the tank, at most 70% of the total length of the tank, at most 50% of the total length of the tank, at most 30% of the total length of the tank or at most 10% of the total length of the tank.

[0038] In particular embodiments, the lateral collection point is positioned at a distance from the longitudinal distribution point corresponding to between 45% and 55% of the total length of the tank.

[0039] In particular embodiments, the septic tank that is the subject of the present invention includes an inlet, connected to the distribution point, positioned in the upper part of the tank.

[0040] In particular embodiments, the septic tank of the present invention comprises an outlet, connected to the lateral collection point, positioned in the upper part of the tank at a height lower than the height of the inlet.

[0041] In particular embodiments, the septic tank of the present invention comprises an effluent treatment element positioned immediately downstream of the lateral collection point.

[0042] These designs prevent backflow into homes when the septic tank is being filled. They also limit the release of solid matter from the tank.

[0043] BRIEF DESCRIPTION OF THE FIGURES

[0044] Other advantages, purposes and special features of the invention will become apparent from the following non-limiting description of at least one particular embodiment of the septic tank that is the subject of the present invention, with reference to the accompanying drawings, in which:

[0045] Figure 1 schematically represents two particular embodiments of septic tanks as provided for in the prior art,

[0046] Figure 2 schematically represents three diagrams illustrating the performance of the septic tank that is the subject of the present invention,

[0047] Figure 3 schematically represents a first view of a particular embodiment of the septic tank that is the subject of the present invention. Figure 4 schematically represents a second view of a particular embodiment of the septic tank that is the subject of the present invention.

[0048] Figure 5 schematically represents a third view of a particular embodiment of the septic tank that is the subject of the present invention,

[0049] Figure 6 schematically represents two diagrams illustrating the performance of the septic tank that is the subject of the present invention and

[0050] Figure 7 schematically represents two diagrams illustrating the performance of the septic tank that is the subject of the present invention.

[0051] DESCRIPTION OF IMPLEMENTATION METHODS

[0052] The present description is given by way of non-limiting attribution, each feature of an embodiment being able to be advantageously combined with any other feature of any other embodiment.

[0053] It should be noted from the outset that the figures are not to scale.

[0054] As can be understood from this description, various inventive concepts can be implemented by one or more of the methods or devices described below, several examples of which are provided herein. The actions or steps performed in the implementation of the method or device can be ordered in any appropriate manner. Consequently, it is possible to construct embodiments in which the actions or steps are performed in a different order than that illustrated, which may include performing certain acts simultaneously, even if they are presented as sequential acts in the illustrated embodiments.

[0055] The expression "and / or," as used in this document, should be understood as meaning "one or the other or both" of the elements thus joined, that is, elements that are present conjunctively in some cases and disjunctively in others. Multiple elements listed with "and / or" should be interpreted in the same way, that is, "one or more" of the elements thus joined. Other elements may also be present, other than those specifically identified by the "and / or" clause, whether or not they are related to those specifically identified elements.Thus, by way of non-limiting example, a reference to "A and / or B", when used in conjunction with an open language such as "including", may refer, in one embodiment, to A only (possibly including elements other than B); in another embodiment, to B only (possibly including elements other than A); in yet another embodiment, to A and B (possibly including other elements).

[0056] As used in this description, the expression "at least one," when referring to a list of one or more items, should be understood as meaning at least one item chosen from one or more items in the list of items, but not necessarily including at least one of each item specifically listed in the list of items and not excluding any combination of items in the list of items. This definition also allows for the optional presence of items other than those specifically identified in the list of items to which the expression "at least one" refers, whether or not they are related to those specifically identified items.Thus, by way of non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B", or, equivalently, "at least one of A and / or B") may refer, in one embodiment, to at least one, possibly including more than one, A, without B present (and possibly including elements other than B); in another embodiment, to at least one, possibly including more than one, B, without A present (and possibly including elements other than A); in yet another embodiment, to at least one, possibly including more than one, A, and at least one, possibly including more than one, B (and possibly including other elements).

[0057] In the description below, all transitive expressions such as "comprising", "including", "carrying", "having", "containing", "implying", "holding", "composed of", and others, should be understood as open, that is, as meaning including but not limited to. Only the transitive expressions "consisting of" and "consisting essentially of" should be understood as closed or semi-closed transitive expressions, respectively.

[0058] Figures 3, 4, and 5 show a schematic view of one embodiment of the septic tank 300, which is the subject of the present invention. In particular:

[0059] - Figure 3 shows, side by side, a front and side view of a particular embodiment of the septic tank 300, the subject of the present invention, illustrating two cross-sectional planes, corresponding to a vertical cross-sectional plane 301 and a horizontal cross-sectional plane 302; - Figure 4 shows a cross-sectional view, along the vertical cross-sectional plane 301, of the septic tank 300, the subject of the present invention; and

[0060] - Figure 5 represents a cross-sectional view, along the horizontal cutting plane 302, of the septic tank 300 which is the subject of the present invention.

[0061] This 300 septic tank includes:

[0062] - a 305 tank for the retention of solid matter and the digestion of organic matter contained in effluents,

[0063] - a longitudinal 310 distribution point for effluents into the reservoir and

[0064] - a lateral collection point 315 for effluents positioned laterally in the tank.

[0065] Tank 305 refers to any closed receptacle suitable for retaining domestic wastewater. This tank 305 can have any shape. To maximize settling efficiency, it is common to use an elongated tank 305. Such a tank 305 might, for example, be rectangular in shape. In a variant such as the one shown in Figure 1, the tank 102 has an oblong internal horizontal cross-section.

[0066] The configuration of the particular shape of the 305 tank depends on the use case for which the 305 tank is configured, and this configuration is therefore not limiting.

[0067] The longitudinal distribution point 310 corresponds, for example, inside the tank 305, to the outlet of a pipe whose inlet is located outside the tank 305. In very simple variants, the longitudinal distribution point 310 corresponds to an opening in a wall of the tank 305.

[0068] Such a distribution point 310 can be adjacent to or remote from an effluent inlet in the tank, positioned at the interface between the inside and outside of the tank 305.

[0069] The distribution point 310 is said to be longitudinal because this distribution point fixes a longitudinal axis of general movement of the effluents in the reservoir 305. This longitudinal axis is represented by the reference 106 in Figure 1.

[0070] This longitudinal axis of effluent movement is preferentially aligned with an axis of symmetry of the tank 305, which corresponds to a centering of the distribution point 310. When the tank 305 is longer than it is wide, this longitudinal axis of effluent movement is preferentially oriented in the general direction of the length of the tank 305, which corresponds for example to a positioning of the distribution point 310 on a short side of the tank 305.

[0071] The lateral collection point 315 corresponds to a liquid effluent collection site located inside the tank 305. This collection site corresponds, for example, to the inlet of a pipe whose outlet is located outside the tank 305. In very simple variants, the lateral collection point 315 corresponds to an opening in a wall of the tank 305.

[0072] The collection point 315 is said to be lateral because this collection point 315 is positioned transversely to the general direction of flow of the effluents in the reservoir 305 at the distribution point 310 in particular.

[0073] Put another way, the collection point 315 is positioned to the side relative to the general direction of flow of effluents in the reservoir 305 at the distribution point 310 in particular.

[0074] In other words, the collection point 315 is said to be lateral because it is positioned elsewhere than on the longitudinal axis of effluent flow in the previously defined tank 305. The collection point 315 is preferably offset from the axis of symmetry of the tank 305 in order to be closer to the lateral wall of the tank 305. When the tank 305 is longer than it is wide, the collection point 315 is preferably located in the general direction of the width of the tank 305, which corresponds, for example, to positioning the collection point 315 on one of the longer sides of the tank 305.

[0075] In other words, collection point 315 is said to be "intermediate" because it is located at an intermediate distance between distribution point 310 and one end of reservoir 305.

[0076] Thus, as can be understood, in particular embodiments, the retention tank 305 has an elongated shape, the longitudinal distribution point 310 being positioned on a short part of the tank and the lateral collection point 315 being positioned on a long part of the tank.

[0077] Such a collection point 315 may be adjacent to or remote from an effluent outlet in the tank, positioned at the interface between the inside and outside of the tank 305.

[0078] In particular embodiments, the retention tank 305 has a parallelepiped shape, the longitudinal distribution point 310 being positioned on a small face of the tank and the lateral collection point 315 being positioned on a large face of the tank.

[0079] In particular embodiments, the retention tank 305 has a rectangular parallelepiped shape.

[0080] In particular embodiments, the lateral collection point 315 is positioned at a distance from the longitudinal distribution point 310 corresponding to at most 90% of the total length of the reservoir 305.

[0081] In particular embodiments, the lateral collection point 315 is positioned at a distance from the longitudinal distribution point 310 corresponding to at most 70% of the total length of the reservoir 305.

[0082] In particular embodiments, the lateral collection point 315 is positioned at a distance from the longitudinal distribution point 310 corresponding to at most 50% of the total length of the reservoir 305.

[0083] In particular embodiments, the lateral collection point 315 is positioned at a distance from the longitudinal distribution point 310 corresponding to at most 30% of the total length of the reservoir 305.

[0084] In particular embodiments, the lateral collection point 315 is positioned at a distance from the longitudinal distribution point 310 corresponding to at most 10% of the total length of the reservoir 305.

[0085] In particular embodiments, the lateral collection point 315 is positioned at a distance from the longitudinal distribution point 310 corresponding to between 45% and 55% of the total length of the reservoir 305.

[0086] This distance 303 is shown in Figure 3 and extends from the projection of the position of the distribution point 310 onto the side of the reservoir 305 on which the collection point 315 is positioned to the center of gravity of the collection point 315.

[0087] In particular embodiments, the septic tank 300 of the present invention includes an inlet 309, connected to the distribution point 310, positioned in the upper part of the tank 305.

[0088] In particular embodiments, the septic tank 300 of the present invention includes an outlet 316, connected to the lateral collection point 315, positioned in the upper part of the tank 305 at a height lower than the height of the inlet 309. In particular embodiments, the septic tank 300 of the present invention includes an effluent treatment element 320 positioned in the tank 305 and downstream of the lateral collection point 315.

[0089] This component 320 is associated with the performance of an effluent filtration function. The type of component 320 depends on the use case implemented for the septic tank 300. It should be noted that component 320 can be a pre-filter, an effluent filter, or any other type of device positioned immediately downstream of the collection point 315.

[0090] The performance of the 300 septic tank as shown in figures 3, 4 and 5 is illustrated in figure 2.

[0091] Figure 2 shows three diagrams, referenced A, B and C, representing the comparison of different performance indicators between the 300 septic tank of the present invention and other known septic tanks.

[0092] Diagram A shows a curve graph of the values ​​of the quantity of suspended solids and the efficiency on suspended solids for the septic tank that is the subject of the present invention:

[0093] - curve 201 of the suspended solids yield calculated between the inlet and outlet of the pit,

[0094] - curve 202 of the concentration of suspended solids measured in the inlet effluent of the pit, and

[0095] - curve 203 of the concentration of suspended matter measured in the effluent from the pit.

[0096] We observe that the average yield of 213 is 73%, with some values ​​reaching 90%. We also observe that the 212 outlet concentrations average 77 mg / L, with a maximum of 120 mg / L and a minimum of 35 mg / L. These values ​​are at least similar to, if not better than, those observed in a typical pit.

[0097] Such values ​​can be measured during a test carried out on a 3 cubic meter septic tank, supplied with domestic wastewater from a housing development of 14 single-family homes. The daily wastewater supply rate is that of standard EN 12566-3. The results correspond to 160 days of testing.

[0098] Diagram B represents, on the x-axis, the volume of recovered liquid effluent in liters, and on the y-axis, the time required to reach that volume. This diagram is derived from tests conducted in clear water on four pit configurations, two of which, 204 and 206, are the subject of the present invention (with and without a flow restrictor), and two, 205 and 207, are typical pits (also with and without a flow restrictor). A volume of 200 L was discharged into the inlet over a three-minute period, corresponding to draining a bathtub. The cumulative volume of water exiting the pits was determined by regularly measuring the volume collected at the outlet over time.

[0099] It is observed that it takes slightly longer to recover the water from the pits described in the present invention, with or without an outlet flow restrictor, suggesting an increased residence time within the pit. An increased residence time corresponds to improved performance for solids retention.

[0100] This value is measured:

[0101] - for the septic tank 204, which is the subject of the present invention, when a flow restrictor is implemented,

[0102] - for a 205 septic tank with longitudinal alignment of distribution and collection points, when a flow restrictor is implemented, and

[0103] - for the septic tank 206, which is the subject of the present invention, without a flow limiter,

[0104] - for a septic tank 207 with longitudinal alignment of distribution and collection points, without flow limiter.

[0105] Compared to a typical pit, a lateral collection point allows the recovery time of the entire injected volume to be extended by 15% and 30% respectively with and without a flow limiter.

[0106] Diagram C represents, on the x-axis, time, and on the y-axis, the sludge level, in centimeters, in the septic tank that is the subject of the present invention. This value is measured:

[0107] - for a measurement point 208 located opposite the distribution point of the septic tank,

[0108] - for a measurement point 209 located laterally to the flow through the tank and at the level of the lateral collection point, and

[0109] - for a measurement point 21 1 located at the longitudinal distribution point.

[0110] Curve 210 of diagram C shows the average of the measurements of curve points 208, 209 and 211. This diagram shows that the sludge heights in the pit subject to the present invention evolve as in a standard pit.

[0111] Diagrams A, B and C illustrate a performance superior or equal to that of the pit which is the subject of the present invention in comparison to existing septic tanks.

[0112] Below, another example of performance is presented.

[0113] Two prototypes of the pit that is the subject of the present invention were installed and put into operation under real-world conditions in order to evaluate the performance of the process in the primary treatment of domestic wastewater. The following results show that:

[0114] - the treatment results of the pit that is the subject of the present invention are very good, and even better than those of a standard pit and

[0115] - the accumulation of sludge in this pit is no different from that observed in a standard pit.

[0116] In this example, two pits of the present invention with a volume of 3 cubic meters, sized for 5 population equivalents (PE), are supplied with real domestic wastewater and are subject to analytical monitoring over time.

[0117] Effluent samples are taken upstream of the septic tank (i.e., the tank inlet) and downstream of the septic tank (i.e., the tank outlet). These are average samples taken over 24 hours.

[0118] The treatment performance is assessed by measuring the concentrations of suspended solids (SS in mg / L) in the effluent.

[0119] Sludge accumulation is assessed by measuring the heights of sludge accumulated in the pit (height in cm).

[0120] The following table summarizes the operating conditions of the tests in progress on the pits which are the subject of the present invention.

[0121] [Table 1]

[0122] A previous test was carried out under similar conditions on a CSTB (Scientific and Technical Center for Building) platform with a standard pit (with longitudinal outlet). Therefore, it is possible to compare the performance of the two types of pits: the standard pit (with longitudinal outlet) against the new pit that is the subject of the present invention. The following table summarizes the operating conditions of the previous test on the pit with longitudinal outlet: [Table 2]

[0123] The results are as follows:

[0124] The operating conditions were set to test the process under extreme operating conditions:

[0125] - Hydraulic overload at the pit inlet: 877 L / day measured compared to 750 L / day nominal, i.e. 117% of the nominal load and

[0126] - introduction of sludge at the start of the test: 35 cm of sludge height at the start compared to 0 cm under normal conditions.

[0127] Figure 6A shows that the performance of the pit described in the present invention ("PE3") for suspended solids (SS) concentration at the outlet and efficiency is very good, even when the pit is operating under hydraulic overload and with a significant sludge level. Indeed, a standard pit is expected to have SS performance below 120 mg / L for an efficiency of at least 60%, which is easily achieved here.

[0128] This is summarized in the table below.

[0129] [Table 3]

[0130] Graph 6B, representing the sludge heights measured in pit PE3, shows that the height tends to stabilize in the pit in a manner similar to what can be observed in a standard pit after a few months of operation.

[0131] The operating conditions are set to test the process under nominal operating conditions. Both pits (PE3 and PE2) were filled under the same conditions:

[0132] - Hydraulic load at the pit inlet: 690 L / day measured, compared to 750 L / day nominal, i.e., 92% of the nominal load and

[0133] - start of the test with a pit free of sludge.

[0134] In graph 7A and in the table presented below, we can see that the performance of the PE3 pit for TSS in outlet concentration and yield is very good.

[0135] [Table 4]

[0136] Figure 7B and the table below show that the performance of pit PE3 is better than that of pit PE2. Pit PE3 exhibits a lower outlet concentration and a higher yield. [Table 5]

[0137] Two prototype pits, the subject of the present invention (lateral exit), of 3 m 3 Tests are being conducted for 5 EH (equivalent inhabitants). The results obtained to date show that the pit described in the present invention fully performs its function of settling suspended solids. The PE3 pits function well, with TSS outlet concentrations of 73 mg / L and 66 mg / L and maximums of 110 mg / L. TSS removal efficiencies are also good (75% and 85%). It should be noted that, conventionally, the following performance is expected of a pit: a maximum TSS of 120 mg / L for an efficiency of at least 60%.

[0138] Moreover, when compared with a standard pit (PE2 with longitudinal outlet), the pit of the present invention shows better performance with a lower TSS rate at outlet (66 mg / L versus 86 mg / L) and a higher yield (85% versus 79%).

[0139] Furthermore, monitoring the evolution of the sludge height in the pit that is the subject of the present invention does not show any abnormal operation.

Claims

DEMANDS 1. Septic tank (300), characterized in that it comprises: - a reservoir (305) for the retention and digestion of organic matter contained in effluents, - a longitudinal distribution point (310) for effluents into the reservoir and - a lateral collection point (315) for effluents positioned laterally in the tank.

2. Septic tank (300) according to claim 1, wherein the retention tank (305) has an elongated shape, the longitudinal distribution point (310) being positioned near a short part of the tank and the lateral collection point (315) being positioned near a long part of the tank.

3. Septic tank (300) according to any one of claims 1 or 2, wherein the retention tank (305) has a parallelepiped shape, the longitudinal distribution point (310) being positioned near a small face of the tank and the lateral collection point (315) being positioned near a large face of the tank.

4. Septic tank (300) according to claim 3, wherein the retention tank (305) has a rectangular parallelepiped shape.

5. Septic tank (300) according to any one of claims 1 to 4, wherein the lateral collection point (315) is positioned at a distance from the longitudinal distribution point (310) corresponding to at most 90% of the total length of the tank, at most 70% of the total length of the tank, at most 50% of the total length of the tank, at most 30% of the total length of the tank or at most 10% of the total length of the tank (305).

6. Septic tank (300) according to claim 4, wherein the lateral collection point (315) is positioned at a distance from the longitudinal distribution point (310) corresponding to between 45% and 55% of the total length of the tank (305).

7. A septic tank (300) according to any one of claims 1 to 6, comprising an inlet (309) connected to the distribution point (310) positioned in the upper part of the tank (305).

8. A septic tank (300) according to claim 7, comprising an outlet (316) connected to the lateral collection point (315) positioned in the upper part of the tank (305) at a height lower than the height of the inlet (309).

9. Septic tank (300) according to any one of claims 1 to 8, comprising an effluent treatment element (320) positioned immediately downstream of the lateral collection point (315).

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