A method for repairing sludge from tail water containing nitrate in a sewage plant and a tail water delivery device

Abstract

The present invention discloses a method for repairing the bottom mud of tail water containing nitrate from a sewage treatment plant and a tail water delivery device, comprising a water delivery pipeline, a box and a water distribution plate, wherein the water inlet end of the water delivery pipeline is connected to the tail water delivery facility of the sewage treatment plant, and the water discharge end of the water delivery pipeline is connected to the box; the box is fitted on the bottom mud at the bottom of the water body, and the water distribution plate fitted on the surface of the bottom mud is fixed at the drainage end of the box, and a deceleration chamber with multiple levels of communication and increasing volume is provided in the box along the flow direction of the fluid; the water inlet end of the deceleration chamber is provided with a deceleration zone, and the drainage end of the deceleration chamber is provided with an arc-shaped deceleration baffle, and the deceleration baffles in two adjacent deceleration chambers are staggered. The design method of the delivery device can deliver the tail water of the sewage treatment plant to the bottom of the water body, so that the nitrate in the tail water directly acts on the polluted bottom mud, and the delivery device has the function of energy dissipation and deceleration, and can use the tail water of the sewage treatment plant as a long-term water replenishment source for the water body, improve the flow rate and self-purification capacity of the water body, and improve the hydrodynamics and habitat conditions.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a method for repairing bottom mud of tail water containing nitrate from a sewage plant and a tail water delivery device. Background Art

[0002] In recent years, my country has attached great importance to water treatment. Through a five-year battle to treat black and odorous urban water bodies, the country has eliminated the black and odorous urban water bodies, completed the dredging of historical sediments, and alleviated the problem of endogenous pollution. However, in the subsequent water quality maintenance stage, new polluted sludge will continue to be generated due to inevitable problems such as pipeline sediments being washed into the river, dry and wet sedimentation, rainfall runoff pollution, and aquatic plant residues. If effective treatment measures are not taken on the sediments on a regular basis, the effectiveness of water treatment cannot be maintained, resulting in eutrophication of the water body and even blackening and odor. The main measures for the treatment of polluted sediments in water bodies include dredging of sediments, addition of chemical agents, and addition of microbial preparations.

[0003] Sediment dredging measures can fundamentally remove polluted sediments, but they have a long construction period and high costs, and most projects require the river to be emptied before implementation, which not only affects the water body function and landscape effect, but also poses a hidden danger to urban drainage and flood control; the method of adding microbial preparations, by inoculating dominant strains, replaces anaerobic microorganisms that are prone to produce reducing substances, and improves the microbial environment of the water body, but in order to maintain the effect, continuous monitoring and replenishment of microbial preparations are required, and the introduction of exogenous species poses an ecological safety hazard; the chemical agents used to treat polluted sediments mainly include calcium hydroxide, calcium nitrate, calcium peroxide, etc., which react with inorganic salts and phosphates released from anaerobic sediments to generate stable calcium and phosphorus, preventing phosphates from entering the water body and causing eutrophication. Because nitrates are oxidizing, they can act as electron acceptors, oxidize sulfides, and inhibit the release of odorous gases, so calcium nitrate has a better treatment effect. However, most of the added chemical agents are highly alkaline, and the one-time use amount is large, which often leads to ecological damage to the water body.

[0004] When using the method of adding chemical agents such as calcium nitrate to treat water sediments, since the chemical agents are not added continuously, there will be a certain time interval between two additions. In order to prolong the treatment effect, excessive chemical agents are often added at one time. The large-scale use of chemical agents causes great damage to the ecological environment of the water body. When the effective ingredients (nitrates and calcium ions) in the agents are consumed, the sediment will return to an anaerobic environment, and phosphates and odorous gases will be released again under the action of anaerobic microorganisms, and the pollution problem will recur. Although the addition of chemical agents such as calcium nitrate can quickly improve the sediment pollution problem in a short period of time, the treatment effect is difficult to maintain. It is necessary to frequently detect changes in the water body and sediment environment, and add a large amount of chemical agents from time to time according to actual needs. At the same time, commercial calcium nitrate is often mixed with a certain amount of calcium hydroxide, which has a certain alkalinity and affects the environment.

[0005] my country's water body management has begun to show results, and various regions have carried out water ecological construction and restoration work. It is of great significance to establish scientific, ecologically safe and environmentally friendly new polluted sediment management technology. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for repairing the sludge of nitrate-containing tail water from a sewage plant and a tail water delivery device, which can transport the tail water from the sewage plant to the bottom of the water body so that the nitrate in the tail water directly acts on the polluted sludge. The delivery device has the function of energy dissipation and deceleration, and can use the tail water from the sewage plant as a long-term water replenishment source for the water body, thereby increasing the flow rate and self-purification capacity of the water body and improving the hydrodynamics and habitat conditions.

[0007] A method for repairing sludge from tail water containing nitrates in a sewage treatment plant comprises the following steps:

[0008] Step 1: According to the water intake method of the tailwater conveying facilities and the reuse delivery device of the sewage treatment plant, determine the height difference h between the tailwater intake point and the water surface and the vertical initial flow velocity Vc of the water delivery pipeline through on-site investigation and measurement; determine the length L1 and diameter d of the water delivery pipeline, unit m; determine the friction coefficient along the water delivery pipeline and the acceleration zone and the local head loss coefficient of the pipeline elbow by selecting the material of the delivery device; determine the local head loss coefficients at the connection between the water delivery pipeline and the deceleration cavity in the box, the connection between the deceleration cavity and the water distribution plate section, and between the deceleration cavities at all levels in the box through the cross-sectional changes of the side wall of the drainage end of the box; determine the local head loss coefficients of the deceleration baffles at all levels through the angle and shape of the deceleration baffles; determine the allowable non-flushing flow velocity Vs=0.1~0.3, unit m / s through the bottom mud conditions and water depth;

[0009] Step 2: Based on the height difference h between the tailwater intake point and the water surface and the vertical initial flow velocity V of the water pipeline determined in step 1 c , calculate the initial water head H0 of the delivery device and the theoretical initial flow velocity v0 of the delivery device by the following formula;

[0010] V0=(2g×H0) 1 / 2 =(2g×(V c 2 / 2g+h)) 1 / 2 =V c +(2gh) 1 / 2

[0011] H0, initial water head of the launching device, m;

[0012] V c , the vertical initial velocity of the tailwater conveying pipeline can be obtained through on-site measurement, m / s;

[0013] h, the height difference between the tailwater intake point and the water surface, that is, the vertical height of the water pipeline before it enters the water body, m;

[0014] Step 3: According to V0 calculated in step 2 and the length L1 and diameter d of the water pipeline, the head loss Hf1 and the residual flow velocity V1 along the water pipeline are calculated by using the Darcy-Weisbach formula;

[0015] Hf1=λL1 / d×V0 2 / 2g

[0016] V1=(2g×H w1 ) 1 / 2 =(2g×(H0-Hf1)) 1 / 2 =(2g×(H0-λL1 / d×V0 2 / 2g)) 1 / 2

[0017] H w1 , residual head, m;

[0018] H f1 , head loss along the water pipeline, m;

[0019] λ, friction coefficient along the water pipeline, λ = 0.014 for reinforced concrete water pipeline;

[0020] Step 4: Calculate the remaining flow velocity V2 by the following formula based on V1 calculated in step 3, the local head loss coefficient ζ1 of the water pipe elbow, and the local head loss coefficient ζ2 of the deceleration cavity entering the box body;

[0021] V2=(2g×H w2 ) 1 / 2 =(2g×(H w1 -H j1 -H j2 )) 1 / 2 =(2g×(H w1 -ζ1×V1 2 / 2g-ζ2×V2 2 / 2g)) 1 / 2

[0022] H w2 , residual head, m;

[0023] H j1 , local head loss at the elbow of the water pipeline, m;

[0024] H j2 , local head loss at the connection between the water delivery pipeline and the deceleration cavity in the box, m;

[0025] ζ1, local head loss coefficient at the elbow of the water pipeline;

[0026] ζ2, local head loss coefficient at the connection between the water delivery pipeline and the deceleration cavity in the box;

[0027] Step 5: Calculate the remaining flow velocity V3 using the following formula based on V2 calculated in step 4, the head loss coefficient λ along the deceleration chamber in the box, the local head loss coefficient ζ3 of the deceleration baffle, and the local head loss coefficient ζ4 at each level of the cross section;

[0028] V2=(2g×H w3 ) 1 / 2 =(2g×(H w2 -H f2 -H j3 -H j4 )) 1 / 2 =(2g×(H w2 -λL2 / d2×V2 2 / 2g-ζ3×V2 2 / 2g-ζ4×V3 2 / 2g)) 1 / 2

[0029] H w3 , residual head, m;

[0030] H f2 , deceleration chamber in single-stage box, head loss along the way, m;

[0031] H j3 , local head loss of the deceleration baffle in the deceleration chamber of the box, m;

[0032] H j4 , local head loss at each section of the deceleration cavity in the box, m;

[0033] ζ3, local head loss coefficient of the deceleration baffle in the deceleration cavity of the box;

[0034] ζ4, ​​local head loss coefficient at each section of the deceleration cavity in the box;

[0035] Step 6: According to the formula and calculation method of step 5, as well as the local head loss coefficient at the outlet of the deceleration cavity in the box, calculate the head loss and residual flow rate V of each level of the deceleration cavity in the box step by step. d , and calculate the final water outlet flow rate V of the delivery device through the residual flow rate S ;

[0036] V S =(2g×H ws ) 1 / 2 =(2g×(H ws’ -H js )) 1 / 2 =2g×(H ws’ -ζs ×V d 2 / 2g)) 1 / 2

[0037] H ws Final residual water head at the outlet of the launching device, m;

[0038] H ws’ , the residual water head at the end of the deceleration chamber in the box and the front end of the water distribution port, m;

[0039] H js , local head loss at the connection between the deceleration chamber in the box and the water distribution port, m;

[0040] ζ s , the local head loss coefficient at the connection between the deceleration chamber in the box and the water distribution port;

[0041] V d， , the residual flow velocity at the end of the deceleration chamber in the box and the front end of the water distribution port, m / s;

[0042] Step 7: According to the calculated data in step 6, when V s =0.1~0.3m / s, the calculation is completed, and the delivery device is designed according to the selected number of deceleration chambers in the box. If V s >0.3m / s, increase the number of deceleration chambers and repeat steps 5 and 6 until V s =0.1~0.3m / s. At this time, the design scheme of the number of deceleration chambers in the box can be determined according to the number of calculations.

[0043] A tailwater delivery device used in a method for repairing nitrate-containing tailwater from a sewage treatment plant, the delivery device comprising a water delivery pipeline, a box and a water distribution plate, wherein the water inlet end of the water delivery pipeline is connected to the tailwater delivery facility of the sewage treatment plant, and the water discharge end of the water delivery pipeline is connected to the box; the box is fitted on the bottom mud at the bottom of the water body, the water distribution plate fitted on the surface of the bottom mud is fixed at the drainage end of the box, and multi-level connected deceleration chambers with successively increasing volumes are provided in the box along the flow direction of the fluid; the water inlet end of the deceleration chamber is provided with a deceleration zone, the drainage end of the deceleration chamber is provided with an arc-shaped deceleration baffle, and the deceleration baffles in two adjacent deceleration chambers are staggered.

[0044] Moreover, a water distribution port is opened on the side wall of the drainage end of the box, and a water distribution plate is fixedly arranged at the bottom of the side wall of the drainage end of the box in the horizontal direction; the water distribution port is located 20cm to 30cm above the mud-water interface; a high vertical plate extending upward is fixedly arranged on the outer periphery of the water distribution plate, and a plurality of vertically penetrating water distribution holes are made on the water distribution plate.

[0045] The advantages and technical effects of the present invention are:

[0046] The present invention provides a method for repairing the sediment of a sewage treatment plant's tail water containing nitrates and a tail water delivery device, which effectively avoids the problems of chemical pollution and water ecological damage caused by excessive addition of chemicals when directly adding chemicals to the water body to treat sediment pollution, as well as repeated water pollution after the chemicals are consumed. The present invention utilizes sewage resources to introduce sewage treatment plant tail water with stable nitrate content into the sediment area of ​​the water body, continuously providing a stable and safe concentration of nitrate for the polluted sediment, sustainably improving and maintaining the non-anaerobic environment of the sediment, and avoiding the generation of black and smelly substances; at the same time, unlike the common practice of discharging sewage treatment plant tail water from the surface of the water body, the delivery device introduces sewage treatment plant tail water into the sediment area, thereby avoiding the problem that the nitrate in the tail water is too low in the lower part due to the conversion of nitrate in the upper layer of the water body or dilution of the water body, and cannot act on the sediment; the delivery device has an energy dissipation and deceleration function, which enables the sewage treatment plant to have The tailwater velocity of gravity flow or pressure flow with a certain impact speed is reduced to below 0.1-0.3m / s, which ensures that the bottom mud is not disturbed by a large amount of stirring to cause turbidity in the water body, and prolongs the contact time of mud and water mixing, so that nitrate and surface bottom mud can fully contact and act, providing sufficient contact time for nitrate to improve the anaerobic environment of the bottom mud; the deceleration chamber adopted in the delivery device adopts the form of step-by-step amplification and deceleration baffle combined with deceleration, which can realize energy dissipation and deceleration in a small space. The delivery device occupies a small area and has a simple structure. At the same time, the orifice-type water distribution plate can effectively expand the contact area between the tailwater and the bottom mud, and improve the scope and effect of treatment.

[0047] The method for repairing nitrate-containing tail water from a sewage treatment plant and the tail water delivery device of the present invention have the following advantages over the prior art:

[0048] (1) The present invention utilizes the oxidizing property of nitrate in the tail water of the sewage treatment plant to oxidize the reducing substances in the sediment, thereby improving the anaerobic environment of the polluted sediment in the water body, preventing the release of pollutants such as phosphates into the water body, and the release of odors such as hydrogen sulfide, thereby preventing the water quality from deteriorating or even becoming black and smelly.

[0049] (2) The nitrate content of the sewage plant tail water of the present invention is low, and while treating the bottom mud, it will not cause damage to the ecological environment.

[0050] (3) The sewage plant tail water of the present invention continuously replenishes water to the water body, which can not only maintain the treatment effect of polluted sludge for a long time and avoid the repeated pollution caused by irregular addition of chemical agents, but also effectively increase the flow rate of the water body and improve the self-purification ability.

[0051] (4) The present invention not only realizes the resource utilization of sewage through the ecological reuse of sewage plant tail water and water bodies, but also avoids the damage to the water environment caused by the large-scale addition of chemical agents, and at the same time has good environmental and social benefits.

[0052] (5) The sewage treatment plant tail water recycling delivery device of the present invention transports the tail water to the mud-water interface at the bottom of the water body, thereby achieving full contact between nitrate and bottom mud, and avoiding the problem that nitrate caused by surface water replenishment is utilized by algae and aquatic plants but cannot act on the bottom mud.

[0053] (6) The sewage treatment plant tail water reuse delivery device of the present invention comprises a multi-stage deceleration chamber and a water distribution plate arranged in a box body, thereby forming an energy dissipation zone and a water distribution zone for the water flow, thereby achieving water pressure and flow rate reduction, avoiding excessive disturbance of the bottom mud to cause water turbidity, and prolonging the contact time between nitrate and the bottom mud. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a front view of the delivery device of the present invention (section view inside the box);

[0055] Figure 2 It is a top view of the delivery device of the present invention (sectional view inside the box);

[0056] In the figure: 1- water delivery pipeline; 2- box body; 3- deceleration chamber; 4- deceleration baffle; 5- water distribution port; 6- high stand; 7- water distribution plate; 8- bottom mud; 9- deceleration area; 10- water distribution hole. DETAILED DESCRIPTION

[0057] In order to further understand the content, features and effects of the present invention, the following embodiments are given as examples and described in detail with reference to the accompanying drawings. It should be noted that the embodiments are illustrative, not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0058] A method for repairing sludge from tail water containing nitrates in a sewage treatment plant comprises the following steps:

[0059] Step 1: According to the water intake method of the tailwater conveying facilities and the reuse delivery device of the sewage treatment plant, determine the height difference h between the tailwater intake point and the water surface and the vertical initial flow velocity Vc of the water delivery pipeline through on-site investigation and measurement; determine the length L1 and diameter d of the water delivery pipeline, unit m; determine the friction coefficient along the water delivery pipeline and the acceleration zone and the local head loss coefficient of the pipeline elbow by selecting the material of the delivery device; determine the local head loss coefficients at the connection between the water delivery pipeline and the deceleration cavity in the box, the connection between the deceleration cavity and the water distribution plate section, and between the deceleration cavities at all levels in the box through the cross-sectional changes of the side wall of the drainage end of the box; determine the local head loss coefficients of the deceleration baffles at all levels through the angle and shape of the deceleration baffles; determine the allowable non-flushing flow velocity Vs=0.1~0.3, unit m / s through the bottom mud conditions and water depth;

[0060] Step 2: Based on the height difference h between the tailwater intake point and the water surface and the vertical initial flow velocity V of the water pipeline determined in step 1 c, calculate the initial water head H0 of the delivery device and the theoretical initial flow velocity v0 of the delivery device by the following formula;

[0061] V0=(2g×H0) 1 / 2 =(2g×(V c 2 / 2g+h)) 1 / 2 =V c +(2gh) 1 / 2

[0062] H0, initial water head of the launching device, m;

[0063] V c , the vertical initial velocity of the tailwater conveying pipeline can be obtained through on-site measurement, m / s;

[0064] h, the height difference between the tailwater intake point and the water surface, that is, the vertical height of the water pipeline before it enters the water body, m;

[0065] Step 3: According to V0 calculated in step 2 and the length L1 and diameter d of the water pipeline, the head loss Hf1 and the residual flow velocity V1 along the water pipeline are calculated by using the Darcy-Weisbach formula;

[0066] Hf1=λL1 / d×V0 2 / 2g

[0067] V1=(2g×H w1 ) 1 / 2 =(2g×(H0-Hf1)) 1 / 2 =(2g×(H0-λL1 / d×V0 2 / 2g)) 1 / 2

[0068] H w1 , residual head, m;

[0069] H f1 , head loss along the water pipeline, m;

[0070] λ, friction coefficient along the water pipeline, λ = 0.014 for reinforced concrete water pipeline;

[0071] Step 4: Calculate the remaining flow velocity V2 by the following formula based on V1 calculated in step 3, the local head loss coefficient ζ1 of the water pipe elbow, and the local head loss coefficient ζ2 of the deceleration cavity entering the box body;

[0072] V2=(2g×H w2 ) 1 / 2 =(2g×(H w1 -H j1 -H j2 )) 1 / 2 =(2g×(Hw1 -ζ1×V1 2 / 2g-ζ2×V2 2 / 2g)) 1 / 2

[0073] H w2 , residual head, m;

[0074] H j1 , local head loss at the elbow of the water pipeline, m;

[0075] H j2 , local head loss at the connection between the water delivery pipeline and the deceleration cavity in the box, m;

[0076] ζ1, local head loss coefficient at the elbow of the water pipeline;

[0077] ζ2, local head loss coefficient at the connection between the water delivery pipeline and the deceleration cavity in the box;

[0078] Step 5: Calculate the remaining flow velocity V3 using the following formula based on V2 calculated in step 4, the head loss coefficient λ along the deceleration chamber in the box, the local head loss coefficient ζ3 of the deceleration baffle, and the local head loss coefficient ζ4 at each level of the cross section;

[0079] V2=(2g×H w3 ) 1 / 2 =(2g×(H w2 -H f2 -H j3 -H j4 )) 1 / 2 =(2g×(H w2 -λL2 / d2×V2 2 / 2g-ζ3×V2 2 / 2g-ζ4×V3 2 / 2g)) 1 / 2

[0080] H w3 , residual head, m;

[0081] H f2 , deceleration chamber in single-stage box, head loss along the way, m;

[0082] H j3 , local head loss of the deceleration baffle in the deceleration chamber of the box, m;

[0083] H j4 , local head loss at each section of the deceleration cavity in the box, m;

[0084] ζ3, local head loss coefficient of the deceleration baffle in the deceleration cavity of the box;

[0085] ζ4, ​​local head loss coefficient at each section of the deceleration cavity in the box;

[0086] Step 6: According to the formula and calculation method of step 5, as well as the local head loss coefficient at the outlet of the deceleration cavity in the box, calculate the head loss and residual flow rate V of each level of the deceleration cavity in the box step by step. d , and calculate the final water outlet flow rate V of the delivery device through the residual flow rate S ;

[0087] V S =(2g×H ws ) 1 / 2 =(2g×(H ws’ -H js )) 1 / 2 =2g×(H ws’ -ζ s ×V d 2 / 2g)) 1 / 2

[0088] H ws Final residual water head at the outlet of the launching device, m;

[0089] H ws’ , the residual water head at the end of the deceleration chamber in the box and the front end of the water distribution port, m;

[0090] H js , local head loss at the connection between the deceleration chamber in the box and the water distribution port, m;

[0091] ζ s , the local head loss coefficient at the connection between the deceleration chamber in the box and the water distribution port;

[0092] V d， , the residual flow velocity at the end of the deceleration chamber in the box and the front end of the water distribution port, m / s;

[0093] Step 7. According to the calculated data in step 6, when Vs=0.1~0.3m / s, the calculation is completed, and the delivery device is designed according to the selected number of deceleration chambers in the casing. If Vs>0.3m / s, the number of deceleration chambers is increased, and steps 5 and 6 are repeated until Vs=0.1~0.3m / s. At this time, the design scheme of the number of deceleration chambers in the casing can be determined according to the number of calculations.

[0094] A tailwater delivery device used in a method for repairing nitrate-containing tailwater from a sewage treatment plant, the delivery device comprising a water delivery pipeline 1, a box 2 and a water distribution plate 7, wherein the water inlet end of the water delivery pipeline is connected to the tailwater delivery facility of the sewage treatment plant, and the water discharge end of the water delivery pipeline is connected to the box; the box is fitted on the bottom mud 8 at the bottom of the water body, the water distribution plate fitted on the surface of the bottom mud is fixed at the drainage end of the box, and a multi-stage connected deceleration chamber 3 with increasing volume is provided in the box along the flow direction of the fluid; the water inlet end of the deceleration chamber is provided with a deceleration zone 9, the drainage end of the deceleration chamber is provided with an arc-shaped deceleration baffle 4, and the deceleration baffles in two adjacent deceleration chambers are staggered.

[0095] Moreover, a water distribution port 5 is opened on the side wall of the drainage end of the box, and a water distribution plate is fixedly arranged at the bottom of the side wall of the drainage end of the box in the horizontal direction; the water distribution port is located 20cm to 30cm above the mud-water interface; a high vertical plate 6 extending upward is fixedly arranged on the outer periphery of the water distribution plate, and a plurality of vertically penetrating water distribution holes 10 are made on the water distribution plate.

[0096] The key to the design method of the deceleration chamber in the box of the delivery device for repairing the bottom sludge by using the self-contained nitrate in the tail water of the sewage treatment plant proposed in the present invention is to determine the number of deceleration stages. The number of deceleration stages is to calculate the residual flow velocity of each section by the Darcy-Weisbach formula and the local head loss formula, and calculate the final residual flow velocity of the water discharged from the delivery device in combination with the local head loss at the water distribution port connection. When the residual flow velocity is higher than the allowable non-impact flow velocity of the bottom sludge, the number of deceleration chambers should be increased; when the residual flow velocity is lower than 0.1m / s, the number of deceleration chambers should be reduced; after adjustment, the above hydraulic calculation is repeated until the residual flow velocity is no higher than the allowable non-impact flow velocity of the bottom sludge of the water body, so as to achieve the purpose of effective tail water reuse and bottom sludge treatment.

[0097] The principle of the method of the present invention is as follows: my country's Class A and above sewage treatment discharge standards have set clear limits on the N in the effluent of sewage treatment plants. At present, relevant domestic sewage plants all use a treatment process including a biological treatment unit for denitrification. Most of the ammonia nitrogen in the influent is removed, and the remaining part is basically discharged in the form of nitrate nitrogen. Because nitrate has a certain oxidizing property, it can improve the anaerobic environment of the sediment and effectively improve the ORP level of the surrounding environment. Nitrate can promote the growth and reproduction of denitrifying autotrophic microorganisms, and is in a dominant position in the competition. At the same time, the denitrification process can consume organic matter in the water body and sediment. Organic matter, as a source of nutrition for anaerobic microorganisms, can effectively inhibit the release of phosphorus and the growth of anaerobic microorganisms. At the same time, nitrate has a certain oxidizing property, which can oxidize ferrous ions to trivalent and sulfur elements to stable positive divalent, avoiding the release of odorous gases such as hydrogen sulfide, and avoiding the deposition of unstable chemical pollutants such as ferrous sulfide.

[0098] The ecological reuse process of sewage plant effluent can continuously provide low-concentration nitrates to the bottom sediment of the water body, avoiding the impact and damage of high-concentration chemical substances on the water environment, while ensuring the improvement of the anaerobic environment of the bottom sediment.

[0099] The scope of application of this application includes: utilizing tail water from sewage treatment plants and sewage treatment facilities that meet Class A and above discharge standards, as well as recycled water, and treating and repairing nitrates contained in tail water or recycled water and sediment.

[0100] In order to more clearly illustrate the specific implementation mode of the present invention, an embodiment is provided below:

[0101] Embodiment 1:

[0102] See Figure 1 , Figure 2 As shown. A water body is located in Xiqing District, Tianjin. After the sediment dredging, sewage interception and other source control and pollution interception measures, the external and internal pollution in the water body has been effectively controlled. However, after the water body treatment, there are still problems such as rainfall runoff pollution and dry and wet sedimentation pollution. Pollutants settle after entering the water body and are enriched in the sediment, causing the dissolved oxygen in the sediment and water body to be consumed. The sediment of the water body is in an anaerobic environment for a long time, which will release phosphates and sulfides. Not only will the previous treatment effect be unable to be maintained, but the water body will also be at risk of eutrophication and even repeated black and smelly.

[0103] In order to avoid the problem of pollutants being released into the water body under anaerobic conditions caused by sediment pollution, it is planned to set up a sewage treatment plant tail water reuse sediment treatment device in the water body. The device will transport the sewage treatment plant tail water containing nitrates to the top of the sediment at the bottom of the water body, including a water delivery pipeline, a trumpet-type deceleration area composed of multi-stage deceleration chambers in the box, and a water distribution area composed of a water distribution plate and the area above it. The water supply pipeline is a circular concrete pipe, and the rear end is connected to the first-stage deceleration chamber in the box body; the box body is a closed concrete box structure with a step-by-step expansion of the cross-section. Multiple deceleration stages can be set according to actual conditions. Each deceleration chamber is provided with a 45° diversion deceleration baffle along the water flow direction. The deceleration baffles in the two adjacent deceleration chambers are staggered. An outlet with a height of 10 cm and a width consistent with the box body is set in the middle of the side wall at the drainage end of the box body, and is connected to the area above the water distribution plate; the water distribution plate is an open stainless steel plate at the top, and 5 cm high high vertical plates are set on the three side walls of the water distribution plate that are not connected to the box body, and a number of water distribution holes are evenly distributed on the water distribution plate; the water distribution holes can evenly distribute the tail water above the bottom mud, and are located 30 cm above the mud-water interface. The design method and steps of the delivery device are as follows:

[0104] Step 1. Through on-site measurements, the surface of the bottom mud of the water body is 1.3m away from the water surface, that is, the water depth is 1.3m; the outlet of the tailwater delivery pipe of the sewage treatment plant is located 0.5m above the surface of the water body, and the vertical initial velocity is 0; the water delivery pipe and the box of the delivery device adopt concrete structure, the friction coefficient along the way is 0.014, and the local head loss coefficient at the elbow is 0.52; through the cross-sectional change form, the local head loss coefficients of the connection between the water delivery pipe and the deceleration chamber, the connection between the box and the water distribution plate section, and the deceleration chambers at all levels in the box are respectively; through the angle and shape of the deceleration baffle, the local head loss coefficient of each level of deceleration baffle is determined; through on-site investigation, according to the characteristics of the bottom mud and the water depth, the allowable non-flushing flow rate is determined to be 0.2m / s.

[0105] Step 2: According to the height difference between the tailwater intake point and the water surface and the vertical initial flow velocity of the water pipeline, the formula V0 = (2g × (V c 2 / 2g+h)) 1 / 2 =V c +(2g h) 1 / 2 , determine the theoretical initial flow velocity V0 of the delivery device to be 3.13m / s.

[0106] Step 3: Set the water pipeline to be 1m long and 0.3m in diameter. The water pipeline and the tank of the delivery device are made of concrete. The friction coefficient along the way is 0.014. According to the formula V1 = (2g × (H0-λL1 / d × V0 2 / 2g)) 1 / 2 , determine the residual velocity V1 at the front end of the right-angle bend of the water pipeline to be 3.02m / s

[0107] Step 4: According to the material selection of the delivery device, the local head loss coefficient at the elbow is determined to be 0.52; the width of the first-stage deceleration cavity in the box is set to 0.5m, and the local head loss coefficient at the connection between the water delivery pipeline and the first-stage deceleration cavity is determined to be 0.55. w1 -ζ1×V1 2 / 2g-ζ2×V2 2 / 2g)) 1 / 2 , determine the residual velocity of the tailwater entering the deceleration zone V2 = 1.64m / s

[0108] Step 5: Set the length × width of the first-stage deceleration chamber to 0.5m, the length × width of the first-stage deceleration chamber to 0.5m × 1m, the first-stage deceleration baffle is inclined at 45 degrees, the length × width = 0.4m × 0.5m, the head loss coefficient along the deceleration chamber is 0.014, and the local head loss coefficient of the deceleration baffle is 0.85. By the formula V2 = (2g × (H w2 -λL2 / d2×V2 2 / 2g-ζ3×V2 2 / 2g)) 1 / 2 , calculate the residual velocity at the end of the first stage deceleration zone V3 = 1.08m / s

[0109] Step 6: According to the second-stage deceleration chamber deceleration baffle being inclined at 45 degrees, length × width = 0.4m × 1m, the local head loss coefficient at the cross section of the two-stage deceleration chamber is 0.6, the head loss coefficient along the process is 0.014, and the local head loss coefficient of the deceleration baffle is 0.85, according to the formula and calculation method of step 5, calculate the residual flow velocity V4 at the end of the second-stage deceleration zone = 0.212m / s

[0110] Step 7: Based on the calculated data of V4 in step 6, the non-impact velocity is approximately 0.2 m / s. No deceleration chamber is required. Based on the local head loss coefficient of 0.48 at the outlet of the deceleration chamber, according to the formula V S =2g×(H ws’ -ζ s ×V d 2 / 2g)) 1 / 2 The final water outlet velocity of the delivery device is calculated to be 0.175 m / s.

[0111] Finally, all the parts not described in the present invention adopt mature products and mature technical means in the prior art.

[0112] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for remediating sludge from tail water containing nitrates in a sewage treatment plant, characterized in that: The following steps are involved: Step 1. According to the water intake method of the tailwater conveying facilities and the reuse device of the sewage treatment plant, determine the height difference h between the tailwater intake point and the water surface and the vertical initial flow velocity Vc of the water conveying pipeline through on-site investigation and measurement; determine the length L1 and diameter d of the water conveying pipeline, unit m; determine the friction coefficient along the water conveying pipeline and the acceleration zone and the local head loss coefficient of the pipe elbow by selecting the material of the device; determine the local head loss coefficient of the connection between the water conveying pipeline and the deceleration cavity in the box, the connection between the deceleration cavity and the water distribution plate section, and the deceleration cavities at all levels in the box through the cross-sectional changes of the side wall of the drainage end of the box; determine the local head loss coefficient of the deceleration baffles at all levels through the angle and shape of the deceleration baffles; determine the allowable non-flushing flow velocity Vs = 0.1 ~ 0.3, unit m / s through the bottom mud conditions and water depth; Step 2: Based on the height difference h between the tailwater intake point and the water surface and the vertical initial flow velocity V of the water pipeline determined in step 1 c , calculate the initial water head H0 of the device and the theoretical initial flow rate v0 of the device by the following formula; V0=(2g×H0) 1 / 2 =(2g×(V c 2 / 2g+h)) 1 / 2 =V c +(2gh) 1 / 2 H0, initial water head of the device, m; V c , the vertical initial velocity of the tailwater conveying pipeline can be obtained through on-site measurement, m / s; h, the height difference between the tailwater intake point and the water surface, that is, the vertical height of the water pipeline before it enters the water body, m; Step 3: According to V0 calculated in step 2 and the length L1 and diameter d of the water pipeline, the head loss Hf1 and the residual flow velocity V1 along the water pipeline are calculated by using the Darcy-Weisbach formula; Hf1=λL1 / d×V0 2 / 2g V1=(2g×H w1 ) 1 / 2 =(2g×(H0-Hf1)) 1 / 2 =(2g×(H0-λL1 / d×V0 2 / 2g)) 1 / 2 H w1 , residual head, m; H f1 , head loss along the water pipeline, m; λ, friction coefficient along the water pipeline, λ = 0.014 for reinforced concrete water pipeline; Step 4: Calculate the remaining flow velocity V2 by the following formula based on V1 calculated in step 3, the local head loss coefficient ζ1 of the water pipe elbow, and the local head loss coefficient ζ2 of the deceleration cavity entering the box body; V2=(2g×H w2 ) 1 / 2 =(2g×(H w1 -H j1 -H j2 )) 1 / 2 =(2g×(H w1 -ζ1×V1 2 / 2g-ζ2×V2 2 / 2g)) 1 / 2 H w2 , residual head, m; H j1 , local head loss at the elbow of the water pipeline, m; H j2 , local head loss at the connection between the water delivery pipeline and the deceleration cavity in the box, m; ζ1, local head loss coefficient at the elbow of the water pipeline; ζ2, local head loss coefficient at the connection between the water delivery pipeline and the deceleration cavity in the box; Step 5: Calculate the remaining flow velocity V3 using the following formula based on V2 calculated in step 4, the head loss coefficient λ along the deceleration chamber in the box, the local head loss coefficient ζ3 of the deceleration baffle, and the local head loss coefficient ζ4 at each level of the cross section; V2=(2g×H w3 ) 1 / 2 =(2g×(H w2 -H f2 -H j3 -H j4 )) 1 / 2 =(2g×(H w2 -λL2 / d2×V2 2 / 2g-ζ3×V2 2 / 2g-ζ4×V3 2 / 2g)) 1 / 2 H w3 , residual head, m; H f2 , deceleration chamber in single-stage box, head loss along the way, m; H j3 , local head loss of the deceleration baffle in the deceleration chamber of the box, m; H j4 , local head loss at each section of the deceleration cavity in the box, m; ζ3, local head loss coefficient of the deceleration baffle in the deceleration cavity of the box; ζ4, ​​local head loss coefficient at each section of the deceleration cavity in the box; Step 6: According to the formula and calculation method of step 5, as well as the local head loss coefficient at the outlet of the deceleration cavity in the box, calculate the head loss and residual flow rate V of each level of the deceleration cavity in the box step by step. d , and calculate the final water outlet flow rate V of the device through the remaining flow rate S ; V S =(2g×H ws ) 1 / 2 =(2g×(H ws’ -H js )) 1 / 2 =2g×(H ws ’-ζ s ×V d 2 / 2g)) 1 / 2 H ws Final residual head at the outlet of the device, m; H ws’ , the residual water head at the end of the deceleration chamber in the box and the front end of the water distribution port, m; H js , local head loss at the connection between the deceleration chamber in the box and the water distribution port, m; ζ s , the local head loss coefficient at the connection between the deceleration chamber in the box and the water distribution port; V d， , the residual flow velocity at the end of the deceleration chamber in the box and the front end of the water distribution port, m / s; Step 7: According to the calculated data in step 6, when V s =0.1~0.3m / s, the calculation is completed, and the device is designed according to the selected number of deceleration chambers in the box. If V s >0.3m / s, increase the number of deceleration chambers and repeat steps 5 and 6 until V s =0.1~0.3m / s, at this time, the design scheme of the number of deceleration chambers in the box can be determined according to the number of calculations; The tailwater delivery device used in the bottom mud repair method of the tailwater containing nitrate in a sewage treatment plant is described. The delivery device comprises a water delivery pipeline, a box and a water distribution plate, wherein the water inlet end of the water delivery pipeline is connected to the tailwater delivery facility of the sewage treatment plant, and the drainage end of the water delivery pipeline is connected to the box; the box is fitted on the bottom mud at the bottom of the water body, the drainage end of the box is fixed with a water distribution plate fitted on the surface of the bottom mud, and the box is provided with multi-level connected and successively increasing deceleration chambers along the flow direction of the fluid; the water inlet end of the deceleration chamber is provided with a deceleration zone, the drainage end of the deceleration chamber is provided with an arc-shaped deceleration baffle, and the deceleration baffles in two adjacent deceleration chambers are staggered; a water distribution port is provided on the side wall of the drainage end of the box, and a water distribution plate is fixedly provided at the bottom of the side wall of the drainage end of the box in the horizontal direction; the water distribution port is located 20 cm to 30 cm above the mud-water interface; the outer periphery of the water distribution plate is vertically fixed with a high vertical plate extending upward, and a plurality of vertically penetrating water distribution holes are formed on the water distribution plate.

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