CN107162344B

CN107162344B - Sewage treatment method

Info

Publication number: CN107162344B
Application number: CN201710532294.6A
Authority: CN
Inventors: 刘大为
Original assignee: Suzhou Huashang New Energy Co ltd
Current assignee: Suzhou Huashang New Energy Co ltd
Priority date: 2017-07-03
Filing date: 2017-07-03
Publication date: 2020-10-02
Anticipated expiration: 2037-07-03
Also published as: CN107162344A

Abstract

The invention relates to a sewage treatment method, the method adopts the sedimentation evaporation method to treat the sewage, the process flow is simple, the equipment investment is small, the sewage is converted into ice for fresh ice, and the organic matter in the sewage is converted into methane, thereby really realizing the change of waste into valuable, improving the economic benefit and reducing the cost of sewage treatment; through heat exchange in the system and the utilization of the self-produced methane for power generation, the energy consumption is reduced, the energy utilization efficiency is improved, and the system has great economic benefits.

Description

Sewage treatment method

Technical Field

The invention relates to sewage treatment, in particular to a sewage treatment method.

Background

The sewage treatment in China faces the situations of serious water pollution, late start of sewage treatment, poor foundation and high requirement. In recent years, the construction of urban sewage treatment has been greatly developed, and as far as the end of 6 months in 2005, 708 sewage treatment plants are built in 661 cities across the country, the treatment capacity is 4912 ten thousand cubic meters per day, which is more than twice of 2000; the annual urban sewage treatment capacity is 162.8 billion cubic meters, which is increased by 43 percent compared with 2000 years, and the urban sewage treatment rate reaches 45.7 percent. But the sewage treatment capacity of most cities cannot meet the actual requirement, and 297 cities in China are not built into sewage treatment plants, wherein 63 cities above grade are provided, and 8 major cities with more than 50 ten thousand of population are provided; 54 cities located within the planning scope of the key basin, region fifteen. In the country, more than 5 million towns, more than 370 million villages and 9 hundred million people residential areas have no sewage treatment facilities.

The sewage is mainly various detergents, sewage, garbage, excrement and the like used in urban life, is mostly nontoxic inorganic salts, contains more nitrogen, phosphorus and sulfur and has more pathogenic bacteria. The sewage is also a low-temperature heat source and a methane generating source, and is a prospective fossil oil and gas field. The sewage contains a large amount of organic matters such as cellulose, starch, saccharides, fat protein and the like; also frequently contain pathogenic bacteria, viruses and parasite eggs; chlorides, sulfates, phosphates, bicarbonates, and sodium, potassium, calcium, magnesium, and the like, of inorganic salts. The amount of sewage is 150-400L, and the amount of sewage is closely related to the living standard. The hazards of high hardness water, especially permanent hardness and high water, are manifested in many ways: difficult to drink; can cause digestive tract dysfunction, diarrhea, and abortion of pregnant animals; is inconvenient for people to use; the energy consumption is high; the service life of the kettle and the boiler is influenced; the water for the boiler is scaled, so that the explosion is easily caused; softening and purifying treatment are needed, and the hardness of underground water is increased due to the loss of acid, alkali and salt into the environment, so that a vicious circle is formed.

For a long time, municipal sewage treatment facilities in China adopt a free use policy, so that not only is the reproduction expanded and the financial investment, but also the simple reproduction can be completed by financial fund allocation, and the financial fund allocation is the only source of the investment for the maintenance and construction of the sewage treatment facilities, so that the sewage treatment is limited by the fund. However, in the prior art, the investment on the treatment equipment of the municipal sewage is large, and the operation cost is too high, so a novel sewage treatment system needs to be designed, and the defects of the sewage treatment system in the prior art can be comprehensively overcome.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a sewage treatment method, has the characteristics of low equipment investment and high economic benefit, and has wide market prospect in application and popularization.

The invention provides a sewage treatment method, which comprises the following steps:

1) introducing sewage to be treated into an evaporation and sedimentation tank, adding a flocculating agent through a flocculating agent feeding device, fully stirring and naturally evaporating, entering a sedimentation and evaporation stage after the feeding is finished, detecting the sewage by using a detector, entering a forced evaporation stage when a measured value reaches a set value, and arranging a steam condensation and collection device on the upper part of the evaporation and sedimentation tank for collecting water vapor in the natural evaporation, sedimentation and evaporation and forced evaporation stages;

2) guiding collected steam water into a first ice maker after being filtered by a permeable membrane, and collecting ice powder which can be used as a fresh ice commodity;

3) and introducing the evaporated residual liquid into a methane tank for anaerobic fermentation, collecting the generated methane, performing solid-liquid separation on the fermented residual liquid after fermentation to obtain a bottom solid phase and an upper water phase, discharging the solid phase as waste, introducing the water phase into a second ice maker, discharging waste water from the lower part of ice powder collected from the upper part of the second ice maker, wherein the ice powder can be used as ice fresh ice commodities, and the waste water is subjected to heat exchange by a steam condenser and then is circulated to an evaporation settling tank for treatment.

The forced evaporation stage is that evaporation equipment arranged below the sewage liquid level of the sedimentation evaporation tank is used for manual heating evaporation; the source of heat for evaporation preferably comprises heat from a heat source generated by an ice machine exchanger: the exchanger radiator can be directly arranged in the evaporation settling tank to be used as a part of evaporation equipment, and the exchanger radiator and the evaporation equipment can also be connected through a heat exchange device.

The source of the evaporation plant may also be the combustion of the self-produced biogas.

In the case of domestic sewage containing many pathogenic bacteria, there are some cases where the pathogenic bacteria are present in the steam obtained by the operations of sedimentation and evaporation alone, and therefore an ultraviolet germicidal lamp is further provided in the evaporation and sedimentation tank for steam sterilization.

The refrigerant of the steam condensation and collection device preferably uses low-temperature waste water discharged from the lower part of the second ice maker.

In another embodiment of the present invention, the method further comprises the following steps: and (3) introducing the methane collected in the step 3) into a methane generator, wherein the methane generator provides electric energy for an ice machine, and the generated superheated wastewater is used for evaporation equipment.

The flocculant of the present invention is not particularly limited, and may be an inorganic flocculant or an organic flocculant. The inorganic flocculant comprises aluminum sulfate, aluminum chloride, ferric sulfate, ferric chloride and the like, and the organic flocculant comprises anionic polyacrylamide, cationic polyacrylamide, nonionic polyacrylamide, chitosan and the like.

According to the treatment process, if the organic macromolecular flocculant capable of being degraded by microorganisms is used, the organic macromolecular flocculant can be directly degraded and fermented in the microbial treatment stage of anaerobic fermentation, so that the characteristic of secondary pollution is avoided, the methane content is increased, and the waste is really changed into valuable.

Chitosan (chitosan) is also called as deacetylated chitin, wherein chitosan molecules contain acylamino, amino and hydroxyl, and show the action of cationic polyelectrolyte along with protonation of amino, so that the chitosan has chelation effect on heavy metals, can effectively flocculate and adsorb fine particles with negative charges in water, and has strong flocculation effect on organic matters such as protein, starch and the like. One of the notable properties of chitosan is its adsorptive capacity. Many low molecular weight materials, such as metal ions, cholesterol, triglycerides, bile acids, and organic mercury, etc., can be adsorbed by chitosan. In particular, the chitosan can adsorb not only magnesium and potassium, but also zinc, calcium, mercury and uranium. The adsorption activity of chitosan can selectively play a role. Chitosan has proven to be a highly effective chelate medium. However, the chitosan is difficult to separate due to the swelling in the solution, aluminum sulfate, polyaluminium chloride and the like are required to be added, and the final flocculation and sedimentation processes are difficult to control.

Aiming at the characteristics of the treatment process and the characteristics of chitosan, the flocculant of the method adopts a modified chitosan flocculant. The fly ash is used as a carrier, and the chitosan is loaded on the surface of the fly ash, so that the adsorbent can save the addition of the chitosan, and the separation operation is simple and easy to implement, and has the advantages of high adsorption rate, large adsorption capacity, no pollution and the like.

The specific preparation method of the chitosan flocculant comprises the following steps: mixing limestone and fly ash according to a certain mass ratio, and then carrying out high-temperature activation in a muffle furnace to obtain the alkali modified fly ash. Gradually adding alkali modified fly ash into a certain amount of chitosan solution according to a certain mass ratio, stirring vigorously, adjusting the pH value to 9 to obtain a coagulated state, then stirring slowly, washing to be neutral, performing suction filtration, drying in a constant-temperature drying oven, grinding and sieving to obtain the fly ash modified chitosan.

Compared with the prior art, the invention has the following beneficial effects:

1) the invention adopts sedimentation evaporation to treat the sewage, has simple process flow and less equipment investment, converts the sewage into ice for fresh ice, and converts organic matters in the sewage into methane, thereby really realizing changing waste into valuable, improving economic benefit and reducing the cost of sewage treatment.

2) The invention also reduces energy consumption and improves energy utilization efficiency through heat exchange in the system and power generation and heating of self-produced biogas, thereby having great economic benefit.

3) According to the characteristics of the treatment process, the organic macromolecular compound which is easy to degrade and is chitosan is used as a flocculating agent, so that the organic macromolecular compound is non-toxic and harmless, can be directly degraded and fermented in the microbial treatment stage of anaerobic fermentation, does not bring secondary pollution, increases the content of methane, and reduces the discharge of waste.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

[ example 1 ]

1. Synthesis of modified chitosan flocculant

300Kg of limestone and 500Kg of fly ash are uniformly mixed on a solid mixer, then are put into a muffle furnace and are activated for 3 hours at 350 ℃, and 780Kg of alkali modified fly ash is prepared. Preparing 200kg of chitosan into an aqueous solution with the mass concentration of 20%, then gradually adding 700kg of the alkali modified fly ash, violently stirring, adjusting the pH to 9 with quick lime, continuously stirring until the mixture becomes a coagulated state, filtering with a plate frame, washing with water to be neutral, performing suction filtration, putting the mixture into a constant-temperature drying oven, drying at 120 ℃, and then grinding and sieving with a 200-mesh sieve to obtain 78kg of fly ash modified chitosan.

2. Treatment of sample wastewater

The quality of the sample domestic sewage is detected, the COD is 3000mg/L, and the total phosphorus is 2.93 mg/L; the ammonia nitrogen content is 20.39 mg/L.

1) Introducing 20t of sample sewage into an evaporation settling tank, adding 500kg of fly ash modified chitosan flocculant through a flocculant feeding device, fully stirring and naturally evaporating, then entering a settling evaporation stage, detecting the sewage through a detector, entering a forced evaporation stage when the COD value reaches a set value, and manually heating and evaporating by using evaporation equipment arranged below the sewage liquid level in the settling evaporation tank, wherein a steam condensation collecting device is arranged at the upper part of the evaporation settling tank and used for collecting evaporated steam;

2) and (3) introducing the collected steam water into an ice maker to make ice after membrane filtration, collecting the ice powder as ice fresh ice, and preparing 6t of ice powder, wherein the ice powder can be used as ice for ice fresh after detection of very low impurity content.

3) Introducing the evaporated residual liquid into a methane tank for anaerobic fermentation, and collecting the generated methane. And introducing the evaporated residual liquid into a methane tank for anaerobic fermentation, collecting the generated methane, and introducing water obtained after solid-liquid separation of the treatment liquid in the methane tank into a second ice maker to obtain 1500kg of solid serving as waste for discharge treatment. And 8t of ice powder is collected from the second ice maker, the ice powder can be used as ice for ice and fresh after the impurity content is detected to be very low, and the waste water at the lower part of the second ice maker is led into a steam condensing device for heat exchange and then is circulated to an evaporation settling tank.

The foregoing description has disclosed fully preferred embodiments of the present invention. It should be noted that those skilled in the art can make modifications to the embodiments of the present invention without departing from the scope of the appended claims. Accordingly, the scope of the appended claims is not to be limited to the specific embodiments described above.

Claims

1. A sewage treatment method comprises the following steps:

1) introducing sewage to be treated into an evaporation and sedimentation tank, adding a flocculating agent through a flocculating agent feeding device, fully stirring and naturally evaporating, entering a sedimentation and evaporation stage after the feeding is finished, detecting the sewage by using a detector, entering a forced evaporation stage when a measured value reaches a set value, and arranging a steam condensation and collection device on the upper part of the evaporation and sedimentation tank for collecting water vapor in the natural evaporation, sedimentation and evaporation and forced evaporation stages; the forced evaporation stage is to use evaporation equipment arranged below the sewage liquid level of the sedimentation evaporation tank to carry out manual heating evaporation;

2) the collected vapor water is filtered by a permeable membrane and then is led into a first ice maker, ice powder is collected and is used as a fresh ice commodity;

3) introducing the evaporated residual liquid into a methane tank for anaerobic fermentation, collecting the generated methane, performing solid-liquid separation on the fermented residual liquid after fermentation to obtain a bottom solid phase and an upper water phase, discharging the solid phase as waste, introducing the water phase into a second ice maker, collecting ice powder at the upper part of the second ice maker, discharging waste water at the lower part of the second ice maker, and circulating the waste water to an evaporation settling tank for treatment after heat exchange by a steam condensing device; the flocculant is a modified chitosan flocculant, the fly ash is used as a carrier, and chitosan is loaded on the surface of the fly ash;

the specific preparation method of the chitosan flocculant comprises the following steps: uniformly mixing 300kg of limestone and 500kg of fly ash on a solid mixer, putting the mixture into a muffle furnace, and activating the mixture for 3 hours at 350 ℃ to obtain 780kg of alkali modified fly ash; preparing 200kg of chitosan into an aqueous solution with the mass concentration of 20%, then gradually adding 700kg of alkali modified fly ash, violently stirring, adjusting the pH to 9 with quick lime, continuously stirring until the mixture becomes a coagulated state, filtering with a plate frame, washing with water to be neutral, performing suction filtration, putting the mixture into a constant-temperature drying oven, drying at 120 ℃, and then grinding and sieving with a 200-mesh sieve to obtain the fly ash modified chitosan;

the heat source of the evaporation equipment comprises heat generated by an exchanger of the ice machine or heat generated by combustion of self-generated methane;

an ultraviolet germicidal lamp is also arranged at the upper part of the evaporation settling tank;

the refrigerant of the steam condensation and collection device uses low-temperature waste water discharged from the lower part of the second ice maker;

and (3) introducing the methane collected in the step 3) into a methane generator, wherein the methane generator provides electric energy for the first ice maker and the second ice maker, and the generated hot high-temperature waste water is used for heating the evaporation equipment.