WO2016206417A1 - Comprehensive sludge treatment method - Google Patents

Abstract

A comprehensive sludge treatment method. The method comprises the following steps: multistage sedimentation; biochemical treatment; aeration catalysis; and sludge recycling treatment. In the treatment method, photocatalyst with relatively high selectivity to urban domestic sewage is adopted in the aeration catalysis step, so that the photocatalytic degradation efficiency is high; in addition, the sludge is modified and made into ceramsite, thereby improving the recycling utilization of the domestic sewage, and improving the additional value of sludge products.

Description

Sludge comprehensive treatment method Technical field

The invention relates to a comprehensive sludge treatment method, in particular to a comprehensive treatment method for sludge from domestic sewage.

Background technique

Sludge is the main component of sewage generated from domestic garbage pollution. Sewage is domestic sewage generated from the normal use of kitchens, bathrooms or bathrooms in households, restaurants, hotels, institutions, schools, factories and other living facilities. Domestic sewage mainly contains sediment, oil, soap, core, paper scraps and crumbs, germs, debris and fecal excretion. According to the chemical nature of the substance, these sewage components can be mainly divided into organic and inorganic substances. Usually, the proportion of organic matter is relatively large, about 60%, and the rest is inorganic. Classified according to physical properties, can be divided into colloidal substances, soluble substances and insoluble substances. The water quality is generally relatively stable compared to industrially discharged wastewater, and the treatment effect is remarkable when bio/chemical methods are used.

CN104649503A discloses a domestic sewage treatment system, which comprises: a grille, a regulating tank, an anoxic tank, an aerobic tank, a sedimentation tank, a disinfection tank, and an input end of the grille is connected with an input end of the regulating tank, and the regulating pool is The output end is connected to the input end of the anoxic tank, the output end of the anoxic tank is also connected to the input end of the aerobic tank, the output end of the aerobic tank is connected to the input end of the sedimentation tank, and the output end of the sedimentation tank and the disinfection tank are The input is connected.

CN104261635A discloses an environmental purification method for domestic sewage, which comprises the steps of: temporarily storing domestic sewage in a collecting pool, using a coarse grid to salvage a large volume of dross, and then using a sewage pump to raise the height of the sewage, Reuse the fine grid to salvage the small amount of dregs; discharge the sewage in the collecting tank into the grease trap, and remove the oil in the sewage by air floatation; The water is discharged into the grit chamber to separate the inorganic particles in the sewage; the sewage in the grit chamber is discharged into the regulating tank to homogenize the water; the sewage pump is used to enter the anoxic tank, and the degradation ability of the anoxic microorganism is utilized. Decompose organic polymer contaminants in sewage into organic low molecular pollutants; discharge the sewage in the anoxic tank into the biochemical pool, and treat the sewage by biofilm method; in the influent area, treatment area, and effluent area of the constructed wetland An anti-seepage film is placed inside.

CN103508576A discloses a method for treating urban domestic sewage. When constructing a new city, the drainage pipes of urban domestic water and the drainage pipes for production water are separately arranged, and at the same time, agricultural development is carried out around the city, and urban domestic sewage is treated. Introduce farmland or water network instead of directly discharging it into rivers. As a fertilizer for planting crops, collect domestic sewage in urban areas through separate pipelines and collect them in domestic sewage treatment stations, and establish multiple sediments (feces) in the suburbs. The pool and the purification pool use pipelines to transport urban domestic sewage from the domestic sewage treatment station to these sedimentation tanks and purification ponds, and after multiple stages of sedimentation and purification of water, separate treatment, sedimentation of feces, etc., can be used as fertilizer Agricultural planting.

CN103265152A discloses a domestic sewage treatment method, belonging to the field of sewage treatment, and the process flow thereof is domestic sewage collection-grid coarse filtration-mud sedimentation and sand water separation-oil separation sedimentation-biological treatment-fine filtration-backwashing, and its characteristics. The grid is coarsely filtered, including coarse grid filtration and fine grid filtration. The grid spacing of the coarse grid is 20 mm; the grid spacing of the fine grid is 5 mm.

CN102020396A discloses a domestic sewage treatment method, which firstly performs solid-liquid separation of domestic sewage, and then performs two-stage biochemical treatment on the separated sewage, and the clean water obtained after the treatment is recycled.

CN101108752A discloses a domestic sewage treatment method, which is characterized in that the domestic sewage is thoroughly mixed with the alkali-containing wastewater of the alumina plant, and then enters the alumina plant sewage treatment system for conventional treatment, which is characterized in that: 10-25 by volume of domestic sewage. %, alumina plant contains 50-90% of alkali wastewater.

CN104291520A discloses a method for treating and recycling domestic sewage, which is characterized in that domestic sewage is classified and discharged, and is classified into high-concentration black water and low-concentration gray water according to the nature and source of the sewage, and the black water is discharged. , through anaerobic treatment tank, aeration contact oxidation tank, high aeration The pollution-resistant ecological pool, the aerated low-resistance ecological pool and the ecological sedimentation treatment tank, the treated black water and the gray water are combined and enter the regulation tank, which is adjusted by the adjustment tank and sent to the underground infiltration device for treatment. The underground percolation device The treated water is sterilized and used for flushing or reaching the standard.

CN103113007A discloses a domestic sewage treatment process, which adopts a biofilm method as a core, a first stage adopts a folded plate anaerobic hydrolysis tank, and a second stage adopts an aerated biological filter tank, wherein the folded plate anaerobic hydrolysis tank is internally provided with Folding plate, the folded plate anaerobic hydrolysis tank can absorb phosphorus under anaerobic conditions.

CN103058312A discloses a method for treating domestic sewage, which belongs to the field of environmental protection. The invention adds calcium silicate to the domestic sewage from the biochemical treatment process, and adds 0.1-1.0g/100mL domestic sewage, and adjusts the pH to 2-12, so that the calcium silicate is uniformly dispersed in water, and maintains 15-90 Minutes; filtered to collect treated water.

US 2013213796 A1 discloses a sewage treatment method, which relates to a method for modifying the structure of an organic sludge to be subjected to dehydration and/or drying, comprising the step of exposing the organic sludge to an electric field therein, wherein The electric field is generated by direct current, and the organic sludge is in the form of a wet solid having a dry matter content of 10% by weight above the total weight of the sludge.

"China's urban sewage treatment problems and solutions", Environmental Protection and Circular Economy, 2011, 04, reviewed the problems faced by China's urban sewage treatment development, pointing out that sewage treatment technology backward urban sewage treatment technology is urban sewage treatment facilities The key to efficient operation, for a long time, China's sewage treatment technology has followed the route and processing technology of European and American countries for nearly one hundred years. It has also formed its own technology while absorbing and digesting foreign technology, and urban sewage treatment technology has Great development, but the sewage treatment technology adopted in China at present is still very backward compared with the foreign technical level in the same period. There are always shortcomings such as low efficiency, high energy consumption, high maintenance rate and low automation.

In the prior art including the above documents, the sludge is usually piled up and discarded, and is not well utilized, and the catalyst used in the aeration catalytic process is not targeted to the urban biological sewage, resulting in low aeration catalytic efficiency. .

Summary of the invention

In order to solve the above problems, the inventors have made intensive research and a large number of experiments, and proposed the following technical solutions.

In one aspect, a method of treating domestic sewage is provided, the method comprising the steps of: (1) multistage precipitation; (2) biochemical treatment; (3) aeration catalysis; and (4) sludge resources. Processing,

The sludge resource treatment comprises: (a) collecting the activated sludge produced during the multi-stage precipitation, biochemical treatment, and aeration catalytic treatment; (b) air drying the sludge to a moisture content of less than 15% by weight, Then adding fly ash and quartz sand to the sludge, the amount of fly ash and quartz sand being 1-5 wt% and 1-3 wt%, respectively, based on the weight of the sludge, stirring for 5-20 hours; c) then adding 0.01-0.08% by weight of polyacrylamide and 0.02-0.08% by weight of hydroxypropylmethylcellulose based on the weight of the sludge, stirring for 1-8 hours; (d) step ( 2) The material is air-dried under ambient conditions to a water content of less than 8% by weight, and then crushed to a particle size of 5 mm or less; (e) The crushed sludge is produced into ceramsite.

The sludge from domestic sewage is loose under water for a long time, the structure is loose, and the void ratio is very large. The water content is very high, reaching 120%-180%, which is much larger than the liquid limit of the sludge, and the natural strength of the sludge is very low. Therefore, sludge is often in the state of fluid flow and flow, so if it is to be used in road paving, it should be modified. After the sludge is treated by the method of the invention, the water content is greatly reduced, the void ratio is decreased, the saturation is correspondingly reduced, the liquidity index and the compression coefficient are significantly lowered, and the sludge soil is changed from fluid plastic to plastic or hard state, and compressed. The property is greatly reduced, the cohesive force is enhanced, the internal friction angle is increased, so that the shear strength is improved, and the arrangement pattern of the soil particles is changed, the sludge structure is reorganized, and the solidified soil has high strength. The low compressibility characteristics satisfy the functional requirements of the roadbed material, for example, the soil strength can be increased by about 22%.

The ceramsite manufacturing method may include the following steps:

(1) Transfer the pulverized particles of construction waste with a particle size of less than 5 mm to a heating furnace at a temperature of 200-300 ° C for 30-60 minutes, transfer the dried raw materials to a ball mill, and ball mill for 10-60. Minutes, ball mill speed 200-300 rev / min;

(2) Add 2-4% by weight of pore-forming agent to the ball mill, continue ball milling and dry-mix for 5-10 minutes, then transfer the mixed raw materials to the batching tank, add water and stir the water, granulate, and the particle size is 5-9mm. Within the range, then dry naturally;

(3) Transfer the dried granules to a heating furnace, heat at a temperature of 300 ° C to 500 ° C for 20-60 minutes, and naturally cool to room temperature to obtain a finished ceramsite.

The granulation step can be carried out using a molding machine or by a granulation method.

The pore former is preferably an amide species having the chemical formula RCNHCH ₂ OH.

The manufacture of the ceramsite can make the sludge product have a higher added value, for example, calculated by the current market conditions, and the modified sludge is made into ceramsite (ie, high-intensity light-weight ceramsite), and the sludge can be made. The added value is further increased by 20-30%.

Preferably, the multistage precipitation step comprises a primary advection precipitation, a secondary advection precipitation, a flocculation reaction, and a flocculation precipitation, the sewage flow direction of the advection sediment being perpendicular to the sedimentation direction of the contaminant particles.

The first-stage advection sedimentation can be carried out in a first-stage advection sedimentation tank, and the secondary advection precipitation can be carried out in a secondary advection sedimentation tank. The flocculation reaction can be carried out in a flocculation reaction tank, and the flocculation precipitation can be carried out in a flocculation sedimentation tank.

Preferably, in the biochemical treatment step, aerobic treatment and anaerobic treatment are included; wherein the aerobic treatment mainly performs nitrification and removal of organic matter, and the aerobic treatment zone has an aeration sand tube at the bottom for aeration charging. The oxygen acts as a stirring at the same time, and a three-phase separator can be arranged in the upper part of the aerobic zone; the anaerobic zone mainly performs denitrification and sludge storage.

Preferably, in the biochemical treatment step, the precipitated sewage uniformly passes through a preset aerobic filter with aerobic species and an anaerobic filter with an anaerobic species. During the treatment process, the suspended micro-pollutants in the sewage can be adsorbed by the treated strains, and the filter materials are intercepted. The organic pollutants are treated by anoxic and anaerobic biochemical treatment, and the biochemical treated sewage is separated by gas and water, and the biogas is removed. Discharge and use.

In the aeration catalytic step, the water body to which the catalyst is added may be bubbled and subjected to aeration catalytic treatment to precipitate ammonia and nitrogen in the sewage. The aeration can be carried out under natural light. Catalyst dosage It may be from 0.01 to 0.2 g/L (sewage), preferably from 0.05 to 0.1 g/L (sewage).

In a preferred embodiment of the present invention, the aeration catalytic step using a catalytic aeration based on TiO ₂ photocatalyst.

The TiO ₂ -based photocatalyst is preferably a bismuth vanadate and Fe ³⁺ co-doped TiO ₂ catalyst, which may be labeled BiVO ₄ -Fe ³⁺ /TiO ₂ . The content of BiVO ₄ may be 5-15% by weight based on the total weight of the catalyst, and the content of Fe ³⁺ may be 1-5% by weight.

The catalyst can be obtained by the following method: (1) 10-20 mL of butyl titanate is slowly added to 20-60 mL of absolute ethanol under stirring, and then 5-10 mL of glacial acetic acid is added, and the ratio of doping is prescribed. A certain amount of BiVO ₄ and Fe ₂ (SO ₄ ) ₃ were separately added to 20-60 mL of absolute ethanol, and then the two solutions were mixed, and the mixture was further stirred until it was in a gel state, and then placed in a constant temperature drying oven to 60- After drying at a constant temperature of 100 ° C for 5-10 h, the sample was ground into a powder; (2) BiVO ₄ , Fe ³⁺ co-doped TiO ₂ xerogel powder was added to distilled water and uniformly dispersed by ultrasonic vibration, followed by repeated pumping. Filtration, remove the Fe ³⁺ in the free state of the sample and then dry it at a constant temperature; (3) put the dried product into a muffle furnace and heat-treat at a temperature of 300-500 ° C for 1-5 h, and then grind. A BiVO ₄ -Fe ³⁺ /TiO ₂ catalyst was obtained.

Particularly preferably, the TiO ₂ is a titanium dioxide nanotube. The titanium dioxide nanotube has a tube pore diameter of preferably 50 to 70 nm and a BET specific surface area of preferably 5 to 7 m ² /g. It has been found that such a pore size and specific surface area of titanium dioxide nanotubes are more likely to adsorb organic matter in solution. Since the photocatalytic reaction is carried out on the surface of the catalyst, the photocatalytic process of the TiO ₂ nanotubes can be obtained more. Illumination radiation, higher photon efficiency, will result in higher photocatalytic activity than TiO ₂ powder or film. The titanium dioxide nanotubes can be produced by a templating method or an anodizing method.

In a more preferred embodiment, the catalyst further comprises phosphorus (P) in an amount of from 0.1 to 1% by weight based on the total weight of the catalyst. It is found that P-doping can increase the specific surface area of TiO ₂ nanotubes, reduce the grain size, inhibit the transformation of anatase TiO ₂ into rutile phase, and have an absorption tail in the visible region, thus effectively increasing TiO ₂ . Visible light catalytic performance. In a more preferred embodiment, the precursor of P is NaH ₂ PO ₄ , and it has been found that obtaining P doping through the precursor allows for better embedding of P into the titanium dioxide nanotubes.

Preferably, in the aeration catalytic step, the water treated in the step (2) is filtered through diatomaceous earth, and then subjected to aeration catalysis.

The sludge recycling treatment step may further include subjecting the sludge to an anaerobic fermentation treatment.

In aeration catalysis, the water body to which the catalyst is added is bubbled and subjected to aeration catalytic treatment, which can precipitate ammonia and nitrogen in the sewage, and then collect and remove floating impurities through floating impurities, so that the sewage is deeply purified into clear water. . Then, the purified water is filtered through a hydrophilic composite sand filter to reduce the surface tension of the water molecules, and the purified water storage reservoir is further purified for reuse.

In the sludge resource treatment, the activated sludge generated during the precipitation, biochemical treatment, and aeration catalytic treatment is collected, for example, can be collected into the sedimentation zone through the gravity channel of the sludge.

detailed description

The technical solutions of the present invention will be further described below in conjunction with the embodiments and comparative examples.

Example 1

The experimental scheme of photocatalytic degradation of rhodamine B was carried out to simulate and investigate the aeration catalytic ability of domestic sewage of the present invention. The photocatalyst 40 mg of BiVO ₄ -Fe ³⁺ /TiO ₂ (10% by weight of BiVO _{4 and 2} % by weight of Fe ³⁺ ) prepared in the above manner was placed in a beaker, and the prepared 200 mL of Rodin was prepared. The Ming B solution (30mg/L) was added to the beaker, and the catalyst powder was completely dispersed in the Rhodamine B solution (concentration: 0.01g/L) by ultrasonic dispersion, and then kept at a constant temperature of 30 °C through a thermostat jacket. Stir at equilibrium to achieve adsorption equilibrium, then take a certain amount of sample in a 10 mL centrifuge tube. The thermostat jacket is filled with a filter (≥420nm), magnetic stirring is placed under a 500W xenon lamp for 4 hours, the liquid of the sample taken in the centrifuge tube is centrifuged, and the supernatant liquid is taken, and the wavelength is measured by an ultraviolet-visible spectrophotometer. Absorbance. The concentration of rhodamine B in the solution is linear with its absorbance. Therefore, the concentration of the rhodamine B can be calculated according to the measured absorbance. Based on this, the degradation rate of rhodamine B of the catalyst is calculated, and the degradation rate is used to evaluate the catalyst. Photocatalytic activity. The degradation rate of rhodamine B at 4 h was determined to be about 81%.

Example 2

The sludge of Example 1 was treated as follows: (a) the sludge was air-dried to a moisture content of less than 15% by weight, and then fly ash and quartz sand were added to the sludge, and the amount of fly ash and quartz sand was based on The weight of the sludge was 3% by weight and 3% by weight, respectively, and stirred for 6 hours; (b) Then, 0.05% by weight of polyacrylamide and 0.05% by weight of hydroxypropyl group based on the weight of the sludge were added thereto. Methylcellulose, stirred for 4 hours; and (c) the material of step (2) was air dried under ambient conditions to a water content of less than 8% by weight and then broken up to a particle size of 12 mm. Through the treatment, the sludge can replace the landfill requirements used in the higher grade roadbed. This can reduce the overall sewage treatment cost by about 12%.

Comparative example 1

The same procedure as in Example 1 was employed, which differed from Example 1 only in that the catalyst was Fe ³⁺ /TiO ₂ (Fe ³⁺ content was 2% by weight), that is, a conventional transition metal doped titania catalyst. The degradation rate of rhodamine B at 4 h was determined to be about 45%.

Comparative example 2

The same procedure as in Example 1 was carried out, except that the catalyst carrier was only a conventional rutile phase TiO ₂ powder (available from Alfa Aesar Co.). The degradation rate of rhodamine B at 4 h was determined to be about 67%.

It is clear from the comparison of the above results that the catalyst of the present invention has an optimum catalytic effect. Such effects are not expected by those skilled in the art. Further research found that the reason is that the conduction band of BiVO ₄ is lower than that of TiO ₂ , so the former acts as a trap for electrons, accumulates a large number of photogenerated electrons and effectively transfers electrons because the direction of movement of photogenerated holes is just right. Contrary to electrons, the electrons generated by TiO ₂ excitation by illumination light migrate directly from its higher conduction band to the lower conduction band of BiVO ₄ , while the photogenerated holes migrate from the lower BiVO ₄ valence band. The higher TiO ₂ valence band enables efficient separation of electrons and holes and increases the reaction rate. BiVO ₄ and TiO ₂ play a good match and system role. In addition, Fe ³⁺ generates defects on the surface of TiO ₂ and becomes a shallow trap of photogenerated electron-hole pairs, which causes the pn photo-electric response to occur simultaneously in the TiO ₂ nano-crystal electrode, thereby effectively prolonging the photo-generated charge recombination time. The probability of recombination is lowered and the photocatalytic activity of TiO ₂ is improved.

The written description uses examples to disclose the invention, including the best mode, The patentable scope of the invention is defined by the claims, and may include other examples that are apparent to those skilled in the art. If such other examples have structural elements that are no different from the literal language of the claims, or if such other examples include equivalent structural elements that are not substantially different from the literal language of the claims, It is within the scope of the claims. To the extent that no inconsistency is caused, all references cited herein are incorporated herein by reference.

Claims (8)

1. A comprehensive sludge treatment method, characterized in that the method comprises the following steps:

   (1) multistage precipitation; (2) biochemical treatment; (3) aeration catalysis; and (4) sludge resource treatment,

   The sludge resource treatment comprises: (a) collecting the activated sludge produced during the multi-stage precipitation, biochemical treatment, and aeration catalytic treatment; (b) air drying the sludge to a moisture content of less than 15% by weight, Then adding fly ash and quartz sand to the sludge, the amount of fly ash and quartz sand being 1-5 wt% and 1-3 wt%, respectively, based on the weight of the sludge, stirring for 5-20 hours; c) then adding 0.01-0.08% by weight of polyacrylamide and 0.02-0.08% by weight of hydroxypropylmethylcellulose based on the weight of the sludge, stirring for 1-8 hours; (d) step ( 2) The material is air-dried under ambient conditions to a water content of less than 8% by weight, and then crushed to a particle size of 5 mm or less; (e) The crushed sludge is produced into ceramsite.
2. The method of claim 1 wherein said multistage precipitation step comprises a primary advection precipitation, a secondary advection precipitation, a flocculation reaction, and a flocculation precipitation, said confluently deposited sewage flow direction being perpendicular to the direction in which the contaminant particles settle.
3. The method according to claim 1 or 2, wherein the first-stage advection sedimentation is carried out in a primary advection sedimentation tank, the secondary advection precipitation is carried out in a secondary advection sedimentation tank, the flocculation reaction is carried out in a flocculation reaction tank, and the flocculation precipitation is in flocculation sedimentation. In the pool.
4. A method according to any one of the preceding claims, wherein in the biochemical treatment step, aerobic treatment and anaerobic treatment are included; aerobic treatment mainly performs nitrification and removal of organic matter, and aeration sand is provided at the bottom of the aerobic treatment zone The tube is stirred at the same time as aeration and oxygenation, and a three-phase separator is arranged in the upper part of the aerobic treatment zone; the anaerobic treatment zone mainly performs denitrification and sludge storage.
5. A method according to any one of the preceding claims, wherein in the biochemical treatment step, the precipitated sewage is uniformly passed through a preset aerobic filter with aerobic species and an anaerobic species Anaerobic filter material.
6. The method according to any one of the preceding claims, wherein in the aeration catalytic step, the water body to which the catalyst is added is bubbled and subjected to aeration catalytic treatment.
7. The method according to claim 6, wherein in the aeration catalytic step, aeration catalysis is performed using a TiO ₂ -based photocatalyst.
8. The method according to claim 6 or 7, wherein in the aeration catalytic step, the water subjected to the step (2) biochemical treatment is subjected to filtration treatment with diatomaceous earth, followed by aeration catalysis.