A method and system for rural sewage treatment and the utilization of sludge and phosphorus resources

Abstract

This invention discloses a method and system for rural sewage treatment and the utilization of sludge and phosphorus resources, relating to the field of rural sewage treatment technology. It addresses the problem of ineffective in-situ utilization of sludge in existing indirect rural sewage resource utilization systems, where sludge thickening tanks are not effectively utilized and phosphorus resources are wasted. This invention pre-treats rural domestic sewage by filtering out large particles, then treats it in an equalization tank before sending it to a biological treatment unit. The effluent from the biological treatment unit is introduced into an constructed wetland for further treatment and reuse as greywater. The remaining sludge discharged from the biological treatment unit is discharged into a phosphorus adsorption tank. The phosphorus-removed sludge is then concentrated in a sludge thickening tank. The concentrated sludge is made into ceramsite, which replaces the ceramsite packing material in the constructed wetland and phosphorus adsorption tank. The displaced phosphorus-containing ceramsite is used as fertilizer for returning to the fields. This invention features simple and reasonable process steps, low cost, proper sewage treatment, and the ceramsite made from sludge adsorbing phosphorus can be used as farmland fertilizer, effectively utilizing sludge and phosphorus in situ.

Description

Technical Field

[0001] This invention relates to the field of rural sewage treatment technology, specifically to a method and system for rural sewage treatment and the utilization of sludge and phosphorus resources. Background Technology

[0002] Rural domestic sewage refers to the wastewater discharged by rural residents during their activities, including washing, bathing, and kitchen use. In my country, the resource utilization of rural domestic sewage is mainly divided into direct resource utilization before treatment and indirect resource utilization after treatment. Direct resource utilization primarily involves biogas utilization after anaerobic digestion and organic fertilizer utilization after biomass composting. Indirect resource utilization mainly includes the following: reuse of treated effluent for farmland irrigation, fisheries, landscaping, or toilet flushing. To meet reuse standards, effluent typically requires deep denitrification and phosphorus removal. When rural sewage undergoes AAO (anaerobic digestion and oxidation) processes for denitrification and phosphorus removal, phosphorus removal mainly relies on the removal of excess sludge. However, in most rural sewage treatment plants, the concentrated sludge at the bottom of the sludge thickening tank needs to be removed every few months. Due to the anaerobic phosphorus release by phosphorus-releasing bacteria, the phosphorus adsorbed by the sludge is released into the supernatant. This phosphorus-containing supernatant overflows from the sludge thickening tank to the equalization tank and returns to the system. This means that phosphorus in rural sewage cannot be removed biologically. If chemical phosphorus removal is used as an adjunct, it increases operating costs, complicates management, and wastes phosphorus resources. Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for rural sewage treatment and the utilization of sludge and phosphorus resources, so as to solve the problems that the sludge in the sludge thickening tank of the existing rural sewage indirect resource utilization system is not effectively utilized in situ, and the phosphorus resources are also wasted.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for rural sewage treatment and the utilization of sludge and phosphorus resources, comprising the following specific contents:

[0005] Rural domestic sewage is classified and black water is pretreated in septic tanks, mixed with grey water and filtered to remove large particles. After being treated in equalization tanks, it is sent to a biological treatment unit to remove phosphorus by removing excess sludge. The effluent from the biological treatment unit is introduced into an artificial wetland for further treatment. The artificial wetland is equipped with ceramsite packing for phosphorus removal, and the effluent from the artificial wetland is reused as greywater.

[0006] The excess sludge discharged from the biological treatment unit is discharged into the phosphorus adsorption tank, which is equipped with ceramsite packing material to fully contact the sludge and adsorb phosphorus. The phosphorus-removed sludge enters the sludge thickening tank for concentration, and the supernatant overflows back to the equalization tank. The concentrated sludge is made into ceramsite using a non-sintering process. After the ceramsite packing material in the artificial wetland and phosphorus adsorption tank has adsorbed enough phosphorus or is saturated, the prepared ceramsite is replaced with it. The phosphorus-containing ceramsite is returned to the field as fertilizer.

[0007] Preferably, the non-sintering process includes mixing concentrated sludge with clay and fly ash and feeding it into a mixing device. A foaming agent is added during mixing. After full foaming, the mixture is shaped using a mold and cured to obtain the finished ceramsite product.

[0008] Preferably, the ratio of sludge, fly ash, and clay is 3:3:1, and carbon dioxide is used as the foaming agent.

[0009] Preferably, if the constructed wetland adopts a horizontal subsurface flow type, the particle size of the finished ceramsite is controlled to be 10-80mm; if the constructed wetland adopts a vertical subsurface flow type, the particle size of the finished ceramsite is controlled to be 5-30mm.

[0010] Preferably, natural curing and / or steam curing are used, with a curing time of 7 to 15 days.

[0011] Preferably, the equalization tank treatment is a homogenization and equalization process.

[0012] Preferably, the biological treatment unit adopts the AAO process, AO process, or MBR process.

[0013] Preferably, the biological treatment unit is filled with MBBR packing material, and the biomass is increased by using the mud film method.

[0014] Preferably, the phosphorus-containing ceramic particles that have been replaced are first crushed by a pulverizer before being returned to the field as fertilizer.

[0015] Another technical solution provided by the present invention: a system for implementing the above method, comprising a septic tank, a basket screen, an equalization tank, an integrated biological treatment device, and an artificial wetland connected in sequence according to the sewage flow direction, and further comprising a phosphorus adsorption tank, a sludge thickening tank, a mixing device, a ceramsite mold, and a curing device arranged in sequence according to the direction of sludge material, wherein the excess sludge discharged from the integrated biological treatment device is directed to the phosphorus adsorption tank, the supernatant of the sludge thickening tank overflows to the equalization tank, and the phosphorus adsorption tank and the artificial wetland are respectively provided with a packing layer using ceramsite produced by the curing device as packing material.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] This method and system for rural sewage treatment and the utilization of sludge and phosphorus resources features simple and reasonable process steps, low cost, and proper sewage treatment. The treated water can be used for farmland irrigation or toilet flushing, and the sludge can be made into ceramsite for use as filler in phosphorus adsorption ponds and constructed wetlands. The ceramsite after phosphorus adsorption can be used as fertilizer for farmland, effectively utilizing sludge and phosphorus in situ and realizing low-cost treatment and resource recycling of rural sewage. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process flow of the method of the present invention. Detailed Implementation

[0019] See Figure 1 A method for rural sewage treatment and the utilization of sludge and phosphorus resources includes the following specific contents:

[0020] Rural domestic sewage is classified and pretreated in septic tanks. Black water is mixed with grey water and large particles are filtered out. After treatment in equalization tanks, it is sent to a biological treatment unit to remove phosphorus by removing excess sludge. The biological treatment unit can use AAO, AO, or MBR processes. Furthermore, MBBR packing can be filled into the biological treatment unit, and the biomass is generally increased by using the mud film method. The effluent from the biological treatment unit is introduced into an constructed wetland for further treatment. The constructed wetland is equipped with ceramsite packing for phosphorus removal. The effluent from the constructed wetland is reused as greywater, for example, for farmland irrigation or toilet flushing.

[0021] The residual sludge discharged from the biological treatment unit is discharged into the phosphorus adsorption tank, which is equipped with ceramsite packing material to fully contact the sludge and adsorb phosphorus. The phosphorus-removed sludge enters the sludge thickening tank for concentration, and the supernatant overflows back to the equalization tank. The concentrated sludge is made into ceramsite using a non-sintering process. After the ceramsite packing material in the constructed wetland and the phosphorus adsorption tank has adsorbed enough phosphorus or is saturated, the prepared ceramsite is replaced with it. The phosphorus-containing ceramsite removed is returned to the field as fertilizer. Preferably, the phosphorus-containing ceramsite removed is first crushed by a crusher before being returned to the field as fertilizer.

[0022] For reference, the above-mentioned non-sintering process for ceramsite includes: mixing concentrated sludge with clay and fly ash and feeding it into a mixing device; adding a foaming agent during mixing; after full foaming, shaping it with a mold; and curing it to obtain the finished ceramsite product. Generally, natural curing and / or steam curing are used, and the curing time can be 7 to 15 days. Preferably, the ratio of sludge, fly ash, and clay in the mixture is 3:3:1, and carbon dioxide is used as the foaming agent. Other existing non-sintering processes on the market can also be used. Non-sintering is mainly for energy saving and convenient implementation in rural areas.

[0023] In the above-mentioned non-sintering process, if the constructed wetland adopts a horizontal subsurface flow type, the particle size of the finished ceramsite should be controlled to be 10-80mm; if the constructed wetland adopts a vertical subsurface flow type, the particle size of the finished ceramsite should be controlled to be 5-30mm. The specific control method can be through the selection of molds.

[0024] In a preferred embodiment, the equalization tank should be a homogenization equalization tank, i.e., a homogenization equalization treatment is performed.

[0025] Based on the above method, the following system can be designed: including a septic tank, a basket screen, an equalization tank, an integrated biological treatment equipment, and an artificial wetland connected in sequence according to the sewage flow direction; and also including a phosphorus adsorption tank, a sludge thickening tank, a mixing device, a ceramsite mold, and a curing equipment arranged in sequence according to the direction of sludge material. The excess sludge discharged from the integrated biological treatment equipment is directed to the phosphorus adsorption tank, and the supernatant from the sludge thickening tank overflows into the equalization tank. The phosphorus adsorption tank and the artificial wetland are respectively equipped with a packing layer using ceramsite produced by the curing equipment as packing material.

[0026] Among the aforementioned curing equipment, steam curing can be carried out using steam-cured silos, while natural curing can be carried out using stockpiles.

[0027] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

[0028] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A method for rural sewage treatment and the utilization of sludge and phosphorus resources, characterized in that, Includes the following specific content: The black water from rural domestic sewage is pretreated in a septic tank, mixed with ash water and filtered to remove large particles. After being treated in an equalization tank, it is sent to a biological treatment unit to remove phosphorus by removing excess sludge. The effluent from the biological treatment unit is introduced into an artificial wetland for further treatment. The artificial wetland is equipped with ceramsite packing for phosphorus removal, and the effluent from the artificial wetland is reused as greywater. The excess sludge discharged from the biological treatment unit is sent to the phosphorus adsorption tank. The phosphorus adsorption tank is equipped with ceramsite packing material to fully contact the sludge and adsorb phosphorus. The phosphorus-removed sludge enters the sludge thickening tank for concentration. The supernatant overflows back to the equalization tank. The concentrated sludge is made into ceramsite using a non-sintering process. Once the ceramsite packing material in the artificial wetland and the phosphorus adsorption tank is saturated, the prepared ceramsite is replaced with it. The phosphorus-containing ceramsite is then returned to the field as fertilizer.

2. The method for rural sewage treatment and sludge and phosphorus resource utilization according to claim 1, characterized in that, The non-sintering process includes: mixing concentrated sludge with clay and fly ash and feeding it into a mixing device; adding a foaming agent while mixing; after full foaming, molding with a mold; and curing after molding to obtain the finished ceramsite product.

3. The method for rural sewage treatment and sludge and phosphorus resource utilization according to claim 2, characterized in that: The ratio of sludge, fly ash, and clay is 3:3:1, and carbon dioxide is used as the foaming agent.

4. The method for rural sewage treatment and sludge and phosphorus resource utilization according to claim 2, characterized in that: If the constructed wetland adopts a horizontal subsurface flow type, the particle size of the finished ceramsite product is controlled to be 10-80mm; if the constructed wetland adopts a vertical subsurface flow type, the particle size of the finished ceramsite product is controlled to be 5-30mm.

5. The method for rural sewage treatment and sludge and phosphorus resource utilization according to claim 2, characterized in that: The curing process employs natural curing and / or steam curing, with a curing time of 7 to 15 days.

6. The method for rural sewage treatment and sludge and phosphorus resource utilization according to claim 1, characterized in that: The equalization tank treatment is a homogenization and equalization process.

7. The method for rural sewage treatment and sludge and phosphorus resource utilization according to claim 1, characterized in that: The biological treatment unit employs AAO, AO, or MBR processes.

8. A method for rural sewage treatment and sludge and phosphorus resource utilization according to claim 7, characterized in that: The biological treatment unit is filled with MBBR packing material, and the biomass is increased using the mud film method.

9. A method for rural sewage treatment and sludge and phosphorus resource utilization according to claim 1, characterized in that: The phosphorus-containing ceramic particles that are replaced are first crushed by a pulverizer and then returned to the field as fertilizer.

10. A system for implementing the method according to any one of claims 1 to 9, characterized in that: The system includes a septic tank, a basket screen, a regulating tank, an integrated biological treatment device, and an artificial wetland, connected in sequence according to the sewage flow direction. It also includes a phosphorus adsorption tank, a sludge thickening tank, a mixing device, a ceramsite mold, and a curing device, arranged in sequence according to the direction of sludge material. The excess sludge discharged from the integrated biological treatment device is directed to the phosphorus adsorption tank, and the supernatant from the sludge thickening tank overflows into the regulating tank. The phosphorus adsorption tank and the artificial wetland are respectively equipped with a packing layer using ceramsite produced by the curing device as the packing material.

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