CN112250155B

CN112250155B - Heavy medium quick-settling water treatment method

Info

Publication number: CN112250155B
Application number: CN201911408156.2A
Authority: CN
Inventors: 李明光; 王志慧; 邸卫猛; 王平; 王雨晨; 刘军明
Original assignee: China Coal Beijing Environmental Engineering Co ltd
Current assignee: Zhongmei (Beijing) Environmental Protection Engineering Co.,Ltd.
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2023-03-17
Anticipated expiration: 2039-12-31
Also published as: CN112250155A

Abstract

The invention relates to a heavy medium rapid sedimentation water treatment system, which comprises a coagulation device, a sedimentation device and a sedimentation device, wherein the coagulation device is used for treating water to be treated added with a coagulant; the flocculation device is used for treating the water to be treated added with the flocculating agent and the micro-sand; a settling device for separating the water after coagulation and flocculation and the sediment produced after coagulation and flocculation; the sand-water separation device is used for recovering the micro sand in the precipitate; the coagulation device is connected to the flocculation device, and the coagulated water is discharged into the flocculation device; the flocculation device is connected to the sedimentation device, and the flocculated water is discharged into the sedimentation device. Compared with the prior art, the heavy medium quick-settling water treatment system and the heavy medium quick-settling water treatment method can effectively remove algae, chroma, metal, TOC, phosphorus and COD; the efficiency is high, the ascending flow speed (surface load) is 60-80m/h, and the efficiency is more than 6 times of that of the conventional sedimentation tank.

Description

Heavy medium quick-settling water treatment method

Technical Field

The invention relates to the field of water treatment, in particular to a heavy medium quick-settling water treatment method and a heavy medium quick-settling water treatment system.

Background

Coal mining wastewater is generated in a coal mine in an underground coal mining process, and main pollutants in the wastewater are suspended particulate matters and oils. The conventional process for treating coal mining wastewater at present is to lift mine water concentrated in a underground water sump to the ground, carry out concentrated treatment on the mine water in a ground construction water treatment plant, mainly comprises a coagulating sedimentation process and an advanced treatment, and precipitate suspended matters after forming alum flocs by adding a flocculating agent and a coagulating agent, but the alum flocs formed by the method are loose and have a slow sedimentation speed, and the water outlet requirement can be met by requiring enough floor space, so a new technology is required to be provided for quickly and efficiently treating the mine water.

The loading flocculation technology is a high-efficiency flocculation precipitation technology, the treatment method is simple, feasible, economical and effective, and can realize quick separation and quick sedimentation. Compared with the traditional flocculation technology, the method has obvious advantages in the aspects of land occupation, energy consumption, operation, sludge water content, dehydration performance and the like.

However, in the current loading flocculation technology, a series of problems still exist, such as low flocculation precipitation efficiency, large occupied area for mine water treatment, backward development of underground treatment technology and equipment, and the like.

Disclosure of Invention

The invention aims to provide a heavy medium quick-settling water treatment system and a heavy medium quick-settling water treatment method, which can improve the water treatment efficiency, greatly reduce the area of a settling tank and the settling time and obtain a good water outlet effect.

According to a first aspect of the present invention, there is provided a heavy medium rapid sedimentation water treatment system comprising,

the coagulation device is used for treating the water to be treated added with the coagulant;

the flocculation device is used for treating the water to be treated added with the flocculating agent and the micro-sand;

a sedimentation device for separating a sediment generated after coagulation and flocculation and treated water;

the sand-water separation device is used for recovering the micro sand in the precipitate;

the coagulation device is connected to the flocculation device, and the coagulated water is discharged into the flocculation device;

the flocculation device is connected to the sedimentation device, and the flocculated water is discharged into the sedimentation device;

the sediment device is connected with the sand-water separation device through a reflux pump, and the sediment is discharged into the sand-water separation device through the reflux pump.

In some embodiments of the heavy medium fast settling water treatment system provided by the present invention, the sand-water separation device is a hydrocyclone.

In some embodiments of the heavy medium fast settling water treatment system provided by the present invention, the flocculation device comprises an injection tank for adding the flocculant and the micro-sand; and the curing tank is used for carrying out flocculation precipitation reaction.

In some embodiments of the heavy medium fast settling water treatment system provided by the invention, the aging tank is provided with an oil removal pipe.

In some embodiments of the heavy medium fast settling water treatment system provided by the present invention, the settling device comprises an inclined plate and/or an inclined tube device.

In some embodiments of the heavy medium fast settling water treatment system provided by the present invention, the diameter of the micro-sand is 60-140 μm, preferably 50-150 μm.

In some embodiments of the heavy medium fast settling water treatment system provided by the present invention, the coagulant is PAC and the flocculant is PAM.

In some embodiments of the heavy medium fast settling water treatment system provided by the present invention, the micro-sand is fly ash.

According to a second aspect of the present invention, there is provided a heavy medium rapid sedimentation water treatment method, comprising,

a coagulation step: adding a coagulant into the water to be treated in the coagulation device, and discharging the water into the flocculation device after coagulation treatment;

flocculation step: adding a flocculating agent and micro-sand into water to be treated in a flocculating device, and discharging the water into a settling device after flocculation treatment;

a precipitation step: separating the precipitate generated after coagulation and flocculation from the treated water, and discharging the precipitate into a sand-water separation device through a reflux pump;

sand-water separation: and recovering the micro sand in the precipitate.

In some embodiments of the heavy medium fast settling water treatment method provided by the invention, a hydrocyclone is used in the sand-water separation step to separate the micro sand from the sediment.

In some embodiments of the heavy medium velocity settling water treatment method provided by the invention, the diameter of the micro-sand used in the flocculation step is 60-140 μm.

In some embodiments of the heavy medium fast settling water treatment method provided by the present invention, the coagulant is PAC and the flocculant is PAM.

In some embodiments of the heavy medium rapid settling water treatment method provided by the invention, the PAC adding concentration is 40-60mg/L, the PAM adding concentration is 1.0mg/L, and the micro-sand adding concentration is 3g/L.

In some embodiments of the heavy medium rapid settling water treatment method provided by the invention, the PAC adding concentration is 60mg/L, the PAM adding concentration is 0.8-1.0mg/L, and the micro-sand adding concentration is 3g/L.

In some embodiments of the heavy medium rapid settling water treatment method provided by the invention, the PAC adding concentration is 15-30mg/L, the PAM adding concentration is 0.2mg/L, and the micro-sand adding concentration is 2g/L.

In some embodiments of the heavy medium rapid settling water treatment method provided by the invention, the PAC adding concentration is 20mg/L, the PAM adding concentration is 0.3-0.5mg/L, and the micro-sand adding concentration is 2g/L.

In some embodiments of the heavy medium fast settling water treatment method provided by the present invention, the micro-sand used in the flocculation step is fly ash.

In some embodiments of the heavy medium fast settling water treatment method provided by the present invention, in the flocculation step, a flocculant is added first, and then the micro-sand is added.

Compared with the prior art, the heavy medium quick-settling water treatment system and the method provided by the invention have the following advantages: the application range is wide, and the method is suitable for various high-difficulty water sources, including low-temperature and low-turbidity water. Algae, chromaticity, metals, TOC, phosphorus and COD can be effectively removed; the efficiency is high, the ascending flow speed (surface load) is 60-80m/h, and the efficiency is more than 6 times of that of a conventional sedimentation tank; the occupied area is small, is far smaller than that of a conventional sedimentation tank, is about one fourth of 1/4 of that of the conventional process, and is particularly suitable for land shortage or reconstruction projects; the economy is good, the investment of civil engineering and equipment is small, the medicament cost is saved, and the operating cost can be effectively reduced by more than 1/3; the operation is stable, and when the flow, turbidity and temperature of raw water fluctuate greatly, the quality of the outlet water can be still ensured stably and reliably by the dense medium equipment; the operation and management are easy, the stable operation state (usually less than 10 minutes) can be entered in a very short time, the full-automatic control can be realized, and the monitoring and the management are easy; the application field is wide, and the heavy medium rapid settling water treatment equipment can be widely applied to occasions of municipal and industrial water supply, sewage and wastewater, recycled water treatment and the like.

Drawings

FIG. 1 is a functional block diagram according to an embodiment of the present invention;

fig. 2 is a functional block diagram of a system according to an embodiment of the present invention.

FIG. 3 is a graph showing turbidity changes of mine water at different PAC dosing concentrations according to an embodiment of the present invention.

FIG. 4 is a graph showing the turbidity change of mine water at different PAM adding concentrations according to the embodiment of the present invention.

FIG. 5 is a graph showing the turbidity change of wastewater at different PAC dosing concentrations according to an example of the present invention.

FIG. 6 is a graph showing the turbidity change of sewage water at different PAM addition concentrations according to the embodiment of the present invention.

FIG. 7 is a graph showing the results of a fly ash particle size screening experiment according to an embodiment of the present invention.

FIG. 8 is a graph showing the results of an experiment of fly ash addition according to an embodiment of the present invention.

FIG. 9 is a graph showing the results of a drug dosing sequence test according to an embodiment of the present invention

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings and embodiments.

It is to be understood that the embodiments described herein are merely exemplary of some, and not all, embodiments of the invention. 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, shall fall within the scope of protection of the present invention.

As shown in fig. 1 and 2, the present invention provides a heavy medium rapid sedimentation water treatment system, including: the coagulation device is a first functional module for treating sewage, and a coagulant is added by a user to destabilize suspended matters and colloids; the flocculation device is used for treating sewage subjected to coagulation treatment, a flocculating agent is added to the sewage, and the flocculating agent is used for rapidly generating high-density alum floc by taking a carrier as a floc core through bridging adsorption and destabilized suspended matters and colloid particles so as to improve settleability and accelerate floc settlement and water to be treated of the micro sand; the sedimentation device is used for separating sediments generated after coagulation and flocculation and treated water, recycling clear water for further utilization, and conveying the sediments to the sand-water separation device through a reflux pump; the sand-water separation device is used for recovering the micro sand in the precipitate, and can be put into use again, so that the cost is reduced, the benefit is improved, and the environment is protected.

In the heavy medium quick settling water treatment system provided by the invention, the hydrocyclone can be used as a sand-water separation device, fine sand is recycled through effective separation of the hydrocyclone, and the supply amount of the fine sand is small.

The flocculation device of the heavy medium quick-settling water treatment system provided by the invention can be divided into an injection tank and a curing tank, wherein the injection tank is used for adding the flocculating agent and the micro-sand, and the curing tank is used for carrying out flocculation precipitation reaction. The stirring speed in the injection pool is higher, and the stirring speed in the curing pool is lower. Different stirring speeds are respectively adopted in the injection tank and the curing tank so as to achieve better flocculation and precipitation effects.

The aging tank of the heavy medium rapid settling water treatment system provided by the invention can be provided with an oil removal pipe, and the demulsified floating oil is discharged out of the system through the oil removal pipe.

The sedimentation device of the heavy medium rapid sedimentation water treatment system provided by the invention can comprise an inclined plate or an inclined tube device, can greatly reduce the area and sedimentation time of a sedimentation tank, and can obtain good water outlet effect.

The micro sand used in the heavy medium quick-settling water treatment system provided by the invention can be of various components and sizes. Through repeated optimization experiments, the diameter of the micro-sand used in the heavy medium rapid settling water treatment system provided by the invention is 60-140 μm, and preferably 50-150 μm.

The coagulant used in the heavy medium quick-settling water treatment system provided by the invention is used for destabilizing suspended matters and colloids in sewage, and the flocculant is used for quickly generating a large amount of alum flocs so as to settle sewage. Products which can achieve this effect can be used. Through repeated optimization experiments, the coagulant used in the invention is PAC, and the flocculant is PAM.

The micro sand used in the heavy medium rapid settling water treatment system provided by the invention can be fly ash.

The invention also provides a heavy medium rapid-settling water treatment method, which comprises the following steps,

sand-water separation: and recovering the micro sand in the precipitate.

For sewage with different concentrations, the amounts of the added medicament and the micro-sand are different. Through repeated optimization experiments, aiming at high-concentration mine water generated by mines, the invention provides two optimal schemes:

according to the first scheme, the adding concentration of a coagulant, namely PAC (polyaluminium chloride), is 40-60mg/L, the adding concentration of a flocculant, namely PAM (polyacrylamide) is 1.0mg/L, and the adding concentration of micro-sand is 3g/L;

and in the second scheme, the adding concentration of the coagulant, namely PAC, is 60mg/L, the adding concentration of the flocculant, namely PAM, is 0.8-1.0mg/L, and the adding concentration of the micro-sand is 3g/L.

Aiming at low-turbidity sewage, the invention provides two preferable schemes:

according to the first scheme, the adding concentration of a coagulant, namely PAC (polyaluminium chloride), is 15-30mg/L, the adding concentration of a flocculant, namely PAM (polyacrylamide), is 0.2mg/L, and the adding concentration of micro-sand is 2g/L.

And in the second scheme, the adding concentration of the coagulant, namely PAC, is 20mg/L, the adding concentration of the flocculant, namely PAM, is 0.3-0.5mg/L, and the adding concentration of the micro-sand is 2g/L.

In the heavy medium rapid settling water treatment method provided by the invention, the micro sand used in the flocculation step can be fly ash.

In the heavy medium quick-settling water treatment method provided by the invention, the flocculating agent and the micro-sand can be added sequentially and respectively or simultaneously, the effects produced by different adding orders in the flocculation step are different, and through repeated optimization experiments, the preferable adding mode adopted by the method is to add the flocculating agent and then add the micro-sand.

Specific example 1: high turbid mine water of certain mine

And (3) carrying out turbidity measurement on the settled water under different PAC (polyaluminium chloride) adding concentrations of PAM (polyacrylamide) and micro-sand of 3g/L on the condition that the PAM adding concentration is 1.0mg/L and the micro-sand adding amount is 3g/L, wherein the experimental data are shown in figure 3. The experiment result shows that the influence of the concentration of PAC on the turbidity of the mine water is obvious. When the concentration of PAC is less than 70mg/L, the removal efficiency of the turbidity of the mine water is higher along with the increase of the concentration of PAC. When the PAC concentration is higher than 70mg/L, the PAC mass concentration is lower along with the increase of the PAC concentration and the mine water turbidity removal efficiency is reduced, because flocs are difficult to form or are small and are difficult to settle because the density is close to water, the suspended matter removal effect is poor, and the turbidity removal efficiency is lower. Along with the increase of the adding amount, aluminum ions (Al 3 +) generated by the hydrolysis of PAC break the colloid charge balance state, the aluminum flakes are accelerated to become larger and heavier, and the removal rate is gradually improved. When the mass concentration of PAC exceeds a certain value, redundant flocculating agents can be adsorbed on the surface of destabilized particles to generate a colloid protection effect, so that the particles are re-stabilized, and the pollutant removal rate is reduced. Therefore, when the PAC mass concentration is 40-60mg/L, the flocculation effect is best, and the turbidity removal rate can reach 99.91 percent to the maximum.

And (3) carrying out turbidity measurement on the settled water under different PAM (polyacrylamide) adding concentrations of the extracted high-turbidity water sample under the conditions that the PAC adding concentration is 60mg/L and the micro-sand adding amount is 3g/L, wherein the experimental data are shown in figure 4. As can be seen from the graph, at a constant mass concentration, the turbidity removal rate of the wastewater increases as the mass concentration of PAM increases. When the quantitative range is exceeded, the contaminant removal rate decreases as the mass concentration of PAM increases. The flocculation of PAM mainly depends on the winding and adsorption bridging of macromolecular chains in sewage, destabilizes and settles macromolecular particles, thereby removing pollutants in sewage. When the relative molecular mass of the polymer is larger, the winding and bridging functions among molecular chains are stronger, and the flocculation effect is better. However, when the mass concentration of PAM exceeds a certain value, polymer molecules are intertwined with each other to re-disperse flocs in the solution, so that the flocculation effect of sewage is deteriorated, and the pollutant removal rate is reduced. Therefore, when the mass concentration of the PAM is 0.9mg/L, the removal efficiency of the pollutants is the highest, and the best treatment effect is achieved.

Specific example 2: low turbidity waste water

Under the conditions that PAM adding concentration is 0.2mg/L and micro-sand adding amount is 2g/L, the loading flocculation treatment is carried out on the water sample of the water from south-to-north water diversion, and the turbidity measurement is carried out on the settled water under different PAC adding concentrations, and the experimental result is shown in figure 5. Overall, the tendency of the effect on low turbidity wastewater contamination at different PAC concentrations is consistent with that of high turbidity wastewater. Within a certain range, the higher the PAC concentration, the higher the contaminant removal efficiency. When the PAC dosage is less, the PAC and the wastewater form larger particles, and the removal effect is poor. Along with the increase of the adding amount, aluminum ions (Al 3 +) generated by the hydrolysis of PAC break the colloid charge balance state, the aluminum flakes are accelerated to become larger and heavier, and the removal rate is gradually improved. When the concentration exceeds a certain level, the efficiency of removing contaminants is lowered. It is clear that the contamination removal efficiency is highest at a PAC mass concentration of 30 mg/L.

Under the conditions that PAC adding concentration is 20mg/L and micro sand adding amount is 2g/L, loading flocculation treatment is carried out on the water sample of the south-to-north water diversion water, turbidity measurement is carried out on the settled water under different PAM adding concentrations, and the experimental result is shown in figure 6. Analysis shows that the addition of the flocculating agent PAM has an obvious promotion effect on rapid aggregation and sedimentation of particles generated by PAC coagulation, suspended substances and organic matters are destabilized and aggregated by the PAM through bridging adsorption and electric neutralization, so that the settlement rate of alum flocs is accelerated, the settling time is reduced, and the treatment period is obviously shortened. When the amount of PAM added is too large, the formation of particulate matter is rather disturbed, resulting in a decrease in the pollutant removal effect. Therefore, the optimum amount of PAM is 0.4mg/L.

Example 3: influence of fly ash and fly ash particle size on treatment effect

The loading flocculation process has strict requirements on the particle size of a loading medium, and the diameter of the micro-sand is 60-140 mu m in micro-sand loading flocculation. The particle size range of the fly ash is large and is between 0.5 and 300 mu m, so that the proper particle size of the fly ash needs to be screened.

Sieving the fly ash used in the experiment, wherein the sieve mesh number is respectively 100, 150, 200 and 325, and the particle size of the fly ash is respectively 0-45, 45-75, 75-106, 106-120, 120-150 and more than 150 mu m. Taking 6 beaker water samples, adjusting the pH value to 8, adding 20mg/L PAC and 1g/L fly ash with different particle sizes (the fly ash can promote flocculation and plays a role of a flocculating agent, so that the fly ash and the PAC are added together), and then adding 0.5mg/L PAM under the condition of slow stirring. After standing for precipitation for 30min, the turbidity and COD of the supernatant were measured. The test results are shown in FIG. 7, where the COD removal rate is shown on the left column and the turbidity removal rate is shown on the right column of each group.

From the results of FIG. 7, it can be seen that the particle size of the fly ash has a very important influence on the turbidity and COD removal effect. When the particle size of the fly ash is less than 75 mu m, the effluent turbidity of the mine water is higher, and the removal rate of COD is lower; when the particle size is 106-120 mu m, the removal rate of COD reaches the peak value, and the removal rate of turbidity is higher; while the turbidity removal rate tends to be stable with further increase in particle size, the removal rate of COD gradually decreases.

This is due to the different structures of fly ash of different particle sizes. The fly ash with the grain size less than 45 is fine particles, and has larger specific surface area and adsorption capacity; the fly ash with the grain diameter of 45-120 is a micro-bead which has compact structure, small specific surface area, larger active site on the surface, higher surface charge and stronger functions in the aspects of compressing double electric layers and adsorbing and bridging; when the particle size of the fly ash is more than 120, the fly ash is called as an amorphous substance, the amorphous substance also has a larger specific surface area, but the amount of electric charge carried on the surface is reduced, the electromotive potential is lower, and the flocculation promotion effect is not obvious.

The optimal particle size of the fly ash obtained by the test is in a microbead stage, the fly ash in the stage has stronger adsorbability and chargeability, the structure is more compact, the density is higher, and the fly ash is suitable for serving as a medium particle for loading flocculation. When the particle size is 106-120 mu m, the pollutant removal rate is highest, so that the fly ash in the particle size range is selected as an experimental material in the experiment.

The influence of the added amount of the fly ash on the treatment effect is as follows: the adding amount of the fly ash can have important influence on the treatment result of the loading flocculation, and in the test, different amounts of fly ash are respectively added to screen out proper adding amount of the fly ash.

Taking 10 beaker water samples, adjusting the pH value to be 8, adding 20mg/L PAC and fly ash with different masses under the condition of rapid stirring, adding 0.5mg/L PAM under the condition of slow stirring, standing and precipitating for 30min, taking supernatant, and measuring the effluent turbidity and COD of the supernatant, wherein the adding amount of the fly ash is 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10g/L respectively. The results are shown in FIG. 8, where the COD removal rate is shown for the left column and the turbidity removal rate is shown for the right column.

As can be seen from fig. 8, when the amount of added fly ash was 2g/L, the removal rate of COD reached a peak, but in general, the change of the removal rate was small, the difference in removal rate was within 10%, and the removal rate of COD slightly decreased with the increase of fly ash. The reason is that when the fly ash is added into mine water, substances on the surface of the fly ash are hydrolyzed, generated cations enter the water, and simultaneously, because of the higher electric potential of the fly ash, the fly ash plays a role in compressing a double electric layer for colloids existing in the water, so that the flocculation effect is promoted. Like the flocculating agent PAC, when the fly ash is excessively added, the electric property of colloid in water can be reversed, and the flocculation is not facilitated. Meanwhile, the fly ash is alkaline due to the fact that the fly ash contains a large proportion of CaO, the pH of the mine water rises along with the increase of the adding amount, and when the pH rises to a certain value, the effect of the flocculating agent is inhibited. However, the COD removing effect of the fly ash is manifold, and the active sites on the surface of the fly ash can adsorb pollutants in water and remove the pollutants along with the sedimentation of the fly ash, so that the more the fly ash is added, the more the adsorption effect is obvious. Therefore, the tendency of the COD removal rate to vary with the amount of fly ash added is not great due to the interaction of multiple mechanisms at different amounts of addition.

Meanwhile, the turbidity changes more smoothly with the addition of the fly ash, and the total turbidity tends to increase. This is because the fly ash captures suspended matter in water and precipitates together by catching and coprecipitation during the sedimentation process. Therefore, the fly ash can effectively remove suspended matters in water, and can achieve high turbidity removal rate with less addition.

The adding amount of the fly ash is of great importance to the influence of the loading flocculation, the effluent quality is poor when the adding amount is small, and the excessive adding amount can not obtain the higher effluent quality, but can increase the generation amount of the treated sludge, thereby causing unnecessary burden for the subsequent treatment. Therefore, the addition amount of the fly ash should be about 2g/L.

Fly ash loading flocculation composite test:

the coal ash loading flocculation treatment of mine water is influenced by various factors, and the most important factors comprise the addition amount of PAC, the addition amount of PAM, the addition amount of coal ash and pH. And screening out the optimal treatment condition for loading and flocculating the fly ash through an orthogonal experiment. Taking 9 beaker water samples, respectively adjusting to corresponding pH values, adding PAC under the condition of rapid stirring, then adding PAM under the condition of slow stirring, standing and precipitating for 30min, and then measuring the turbidity and COD of supernatant liquid. The adding amount of the flocculating agent PAC is respectively 15, 20 and 25mg/L, the adding amount of the coagulant aid PAM is respectively 0.5, 1.0 and 1.5mg/L, the adding amount of the fly ash is respectively 1, 2 and 3g/L, and the pH level is respectively 7, 8 and 9. The COD removal rate of the mine water is used as an index, the effect of the loading flocculation is analyzed, and the analysis result is shown in table 1.

TABLE 1 fly ash Loading flocculation Compound test analysis

As can be seen from table 1, the influence of pH is still greatest in the fly ash loaded flocculation test. The pH value affects the hydrolysis of PAC and the surface charge of PAM, and the surface hydrolysis of fly ash is also affected by pH. It can be seen that the removal effect of COD was the best at an initial pH of 7 in the fly ash loading flocculation test, while the removal effect was better at a pH of 8 in the coagulation test. The reason is that the fly ash contains a certain amount of CaO, and after the fly ash is mixed with water, the CaO in the fly ash is dissolved in the water, so that the pH value of the mine water is increased. When the initial pH of the mine water is high, hydrolysis of PAC is not favored, resulting in a decrease in flocculation effect. Meanwhile, it can be seen that the fly ash loading flocculation also has certain advantages in the acidic mine water treatment.

Along with the addition of the fly ash, the higher COD removal rate can be achieved when the addition amount of PAC is 15 mg/L. The reason is that the fly ash has higher electromotive potential and can be hydrolyzed to generate a large amount of metal cations, so that the fly ash plays a role in compressing a double electric layer for colloids in water, flocculation is promoted, and a flocculating agent required in a flocculation process is reduced.

The effect of PAM on the treatment effect is minimal, and the COD removal rate is gradually reduced along with the increase of the adding amount. The PAM has the same effect as that in a coagulation test, and has the main effect of performing a bridging effect among tiny flocs to promote the growth and enlargement of the flocs. The surface of the fly ash has a plurality of active sites, which can absorb colloid and suspended matters in water and has a certain bridging function. Thus, the action of PAM is impaired in loaded flocculation.

The fly ash is used as medium particles for a loading flocculation test and is an important influencing factor for loading flocculation. The pH value of the mine water can be changed by adding the fly ash, the flocculation effect can be promoted, and the adding amount of the fly ash is related to the treatment effect of the loading flocculation. Experiments show that when the adding amount of the fly ash is 2g/L, the COD removing effect is better.

Therefore, the optimal experimental conditions for the fly ash loading flocculation test are as follows: the PAC dosage is 15mg/L, the PAM dosage is 0.5mg/L, the fly ash dosage is 2g/L, and the initial pH is 7.

Influence of the addition sequence on the treatment effect:

the addition sequence of the agents also has an influence on the treatment effect. In the micro-sand loading flocculation, firstly adding a flocculating agent into raw water, then entering a mixing tank, rapidly stirring and mixing, then entering a filling tank, then adding a high-molecular polymer coagulant aid and a fine sand carrier to further promote the formation of flocs, then entering a floc curing tank, continuously condensing fine sand floc nuclei to generate larger flocs under slow stirring, finally flowing into an inclined tube sedimentation tank, and rapidly settling and separating floc particles in water under the action of gravity sedimentation and rapid sedimentation of an inclined tube. The different dosing sequences are caused by different functions of the loaded particles in different loading flocculation processes. In the micro-sand loading flocculation, the micro-sand has the functions of improving the sedimentation performance of the flocs and accelerating the sedimentation of the flocs.

In the fly ash loading flocculation, the function of the fly ash is also multifaceted, and the dosing sequence in the traditional loading flocculation process is not necessarily suitable for the fly ash loading flocculation, so that four sets of reagent dosing schemes are designed in the experiment, and the optimal reagent dosing sequence for the fly ash loading flocculation is screened on the basis of the experiment.

Taking water samples of 3 beakers, respectively adjusting the pH value to 7, and then adding a flocculating agent, a coagulant aid and fly ash according to different sequences, wherein the adding sequences are as follows: PAC is added under the condition of rapid stirring, and PAM and fly ash are simultaneously added under the condition of slow stirring; PAC is added under the condition of rapid stirring, PAM is added under the condition of slow stirring, and fly ash is added after 3 min; PAC and fly ash are simultaneously added under the condition of rapid stirring, and PAM is added under the condition of slow stirring; PAC is added under the condition of rapid stirring, fly ash is added after 1min, and PAM is added under the condition of slow stirring. Wherein the dosage of PAC is 15mg/L, the dosage of PAM is 0.5mg/L, and the dosage of fly ash is 2.0g/L. After standing and precipitating, taking the supernatant to measure COD and turbidity. The results are shown in FIG. 9, where the COD removal rate is shown for the left column and the turbidity removal rate is shown for the right column.

As can be seen from FIG. 9, the best treatment effect can be obtained by the adding method, and the earlier the fly ash is added, the better the removal effect is. This is because, during the flocculation process of the fly ash loading, the fly ash can promote the formation of flocs and enhance flocculation. In the method, after raw water and PAC are fully mixed, colloid in the water already forms tiny floc, and then the coal ash is added, so that the effect of a compression double electric layer of the coal ash is greatly reduced, and the removal effect of COD is reduced. The method is characterized in that fly ash is added at last, colloid and fine particles in water form larger flocs under the action of PAC and PAM, the fly ash can only promote the sedimentation of the flocs, and the influence on the flocculation effect is very weak. The method is characterized in that the fly ash is added after PAC is added for a period of time, at the moment, the colloid and the fine particles in the raw water are mixed with the PAC, micro flocs are not formed completely, the fly ash can also exert the effect of compressing double electric layers and strengthen the flocculation effect, and therefore, the treatment effect of the method is higher than that of the method. The method is that PAC and fly ash are added into water at the same time, so that the PAC and fly ash are fully mixed with colloid and fine particles in raw water, and the flocculation effect of the fly ash is played locally, so that the flocculation effect is optimal.

Example 4: the development and application of a series of heavy medium rapid settling water treatment equipment.

And (3) process comparison: several flocculation apparatuses are compared in the aspects of process advancement, treatment capacity and equipment configuration, flocculation residence time (min), maximum surface load (m/h) plane size, floor area (m 2) and the like. From table 2, it can be concluded that the heavy medium rapid-settling water treatment equipment has the following characteristics:

first, the application range is wide. Is suitable for various high-difficulty water sources, including low-temperature and low-turbidity water. Can effectively remove algae, chroma, metal, TOC, phosphor and COD. Second, high efficiency. The ascending flow velocity (surface load) is 60 to 80m/h. The efficiency is more than 6 times of that of the conventional sedimentation tank. Thirdly, the floor space is small. The occupied area is far smaller than that of a conventional sedimentation tank, about one fourth of that of the conventional process, and the method is particularly suitable for land shortage or reconstruction engineering. Fourth, economy. The civil engineering and equipment investment is small, the medicament cost is saved, and the operating cost can be effectively reduced by more than 1/3. Fifthly, the operation is stable. When the flow, turbidity and temperature of raw water fluctuate greatly, the quality of the discharged water can still be ensured stably and reliably by the heavy medium equipment. Can stably treat the wastewater with the suspended matter concentration of less than 12000 mg/L. Sixth, easy operation and management. The ability to enter a stable operating state in a very short time (typically less than 10 minutes); and the system is fully automatically controlled and is easy to monitor and manage. Seventh, the application is wide. The heavy medium quick-settling water treatment equipment can be widely applied to municipal and industrial water supply, sewage and wastewater, recycled water treatment and other occasions, including coal mine, electric power, papermaking, chemical engineering, electronic and river purification. Meanwhile, the method is suitable for underground mine water treatment engineering and is suitable for underground construction of water treatment stations. The economic comparison of the different process technologies is shown in table 2.

Table 2: economic comparison of different process technologies

5.2 development and application of heavy medium rapid-settling water treatment equipment

The traditional mature process usually has large floor area and high construction investment cost; the treatment cost of generating the auxiliary waste water and waste residue is high; the treated mine water is less recycled; the operation cost is high; the operation cannot be stabilized; most mine water treatment facilities cannot adapt to the defects of coal mines and the like, so the research designs a process flow and a system for treating the mine water by using the heavy medium quick-settling water on the basis of experimental research according to a figure 1 and a figure 2, and obviously, the treatment effect of the micro-sand is slightly higher than that of the fly ash by comparing the treatment effects of two heavy medium materials of the fly ash and the micro-sand, so the heavy medium material of the subsequent process flow selects the micro-sand.

The system corresponding to the process comprises five parts, wherein the first part is a coagulation tank and has the function of destabilizing suspended matters and colloidal particles. The natural particles that cause turbidity in the raw water are negatively charged and repel each other, thereby forming a highly stable state. To remove them, the microparticles are first destabilized by the addition of a coagulant (aluminum or iron salt). The dynamic process of coagulation is very short, and the coagulant achieves rapid and complete diffusion in the coagulation tank through rapid mechanical stirring (1-2 min).

The second part is an injection pool, and high-density flocs are formed by the adsorption of a bridge frame. The microsize, having a particle size of about 100-150 μm, is fed into the secondary reaction zone and its reaction is accelerated by high speed stirring (1-2 min) while the microsize is continuously circulated to increase the probability of agglomeration, ensuring proper floc to increase their growth rate and weight.

The third part is a curing tank which has the function of forming mature flocs with micro sand as a core and discharging the demulsified floating oil out of the system through an oil removal pipe. The stirring of this part needs low speed stirring (4-6 min), and the time for using is longer than that of the first two parts. The function of the tertiary reaction zone is to form large flocs. Flocculation is a physical mechanical process that enhances the growth of the flocculent due to intermolecular forces and physical agitation. The addition of the anionic polymer electrolyte can improve the generation of flocculating constituents through the bridging action among adsorption, electric neutralization and particles. Due to the accelerated flocculation of the micro-sand, the velocity gradient is equivalent to more than 8 times of the traditional flocculation process under the condition of the same sedimentation performance. With limited agitation time and limited flocculation volume, high flocculation kinetics results in increased inter-particle collision probability. Gently agitate the water to prevent disruption of flocs. In this stage, it is sufficient to keep the flocs suspended, although the agitation intensity is less than in the previous coagulation stage.

The fourth part is a sedimentation tank which has the functions of separating mud from water and purifying water. The sedimentation tank adopts low-speed sludge scraping and is combined with an inclined pipe, so that the sedimentation area is increased to achieve the effect of high-speed sedimentation (40-60 m/h).

The fifth part is a micro-sand circulating system which has the functions of discharging sludge and recovering micro-sand. The part comprises two devices of a sludge reflux pump and a silt separator. The reflux amount of the sludge pump is 3-6% of the water inflow, the micro-sand recovery efficiency is about 9%, and the micro-sand supplement amount is about 1g/m < 3 >.

The heavy medium rapid settling water treatment equipment has absolute advantages in the coagulating sedimentation process compared with other equipment. The equipment occupies a small area, has low operation cost and convenient maintenance and management, and has remarkable advantages compared with other flocculation equipment.

The foregoing describes preferred embodiments of the present invention, but the spirit and scope of the present invention is not limited to the specific disclosure herein. Those skilled in the art can freely combine and expand the above-described embodiments according to the teachings of the present invention to make further embodiments and applications within the spirit and scope of the present invention. The spirit and scope of the present invention are not to be limited by the specific embodiments but by the appended claims.

The invention can be implemented based on the following examples:

1. a heavy medium rapid-settling water treatment system is characterized by comprising,

a settling device for separating the water after coagulation and flocculation and the sediment produced after coagulation and flocculation;

2. The heavy medium fast settling water treatment system of example 1, wherein the sand-water separation device is a hydrocyclone.

3. The heavy medium velocity sedimentation water treatment system according to example 1, wherein the flocculation apparatus comprises,

the injection pool is used for adding the flocculating agent and the micro-sand;

and the curing tank is used for performing flocculation precipitation reaction.

4. The heavy medium fast sinking water treatment system of example 3, wherein the maturation tank is provided with an oil removal pipe.

5. The heavy medium velocity heavy water treatment system of example 1, wherein the settling device comprises an inclined plate and/or an inclined tube device.

6. The heavy medium velocity settling water treatment system according to example 1, wherein the diameter of the micro sand is 60-140 μm, preferably 50-150 μm.

7. The heavy medium fast settling water treatment system according to example 1, wherein the coagulant is PAC and the flocculant is PAM.

8. The heavy medium fast settling water treatment system of example 1, wherein the micro-sand is fly ash.

9. A heavy medium rapid sedimentation water treatment method is characterized by comprising the following steps,

a step of coagulation: adding a coagulant into the water to be treated in the coagulation device, and discharging the water into the flocculation device after coagulation treatment;

sand-water separation: and recovering the micro sand in the precipitate.

10. The heavy medium fast settling water treatment method according to example 9, wherein the sand-water separation step is performed by separating fine sand from the sediment using a hydrocyclone.

11. The heavy medium velocity sedimentation water treatment method according to example 9, wherein the diameter of the fine sand used in the flocculation step is 60 to 140 μm, preferably 50 to 150 μm.

12. The method for treating heavy medium fast settling water according to example 9, wherein the coagulant is PAC and the flocculant is PAM.

13. The heavy medium rapid-settling water treatment method according to example 12, wherein the PAC dosage concentration is 40-60mg/L, the PAM dosage concentration is 1.0mg/L, and the micro-sand dosage concentration is 3g/L.

14. The heavy medium rapid-settling water treatment method according to example 12, wherein the PAC dosage concentration is 60mg/L, the PAM dosage concentration is 0.8-1.0mg/L, and the micro-sand dosage concentration is 3g/L.

15. The heavy medium rapid-settling water treatment method according to example 12, wherein the PAC dosage concentration is 15-30mg/L, the PAM dosage concentration is 0.2mg/L, and the micro-sand dosage concentration is 2g/L.

16. The heavy medium quick-settling water treatment method according to example 12, wherein the PAC dosing concentration is 20mg/L, the PAM dosing concentration is 0.3-0.5mg/L, and the micro-sand dosing concentration is 2g/L.

17. The heavy medium fast settling water treatment method according to example 9, characterized in that the micro-sand used in the flocculation step is fly ash.

18. The heavy medium rapid settling water treatment method according to example 9, characterized in that in the flocculation step, a flocculating agent is added first, and then the micro-sand is added.

Claims

1. A heavy medium rapid sedimentation water treatment method is characterized by comprising the following steps,

a coagulation step: simultaneously adding a coagulant and fly ash into water to be treated under the condition of rapid stirring, wherein the coagulant is PAC (poly-aluminum chloride), the dosage of the PAC is 15mg/L, and the dosage of the fly ash is 2.0g/L, and discharging the water into a flocculation device after coagulation treatment;

flocculation step: adding a flocculating agent into the water to be treated by the coagulation device under the condition of slow stirring, wherein the flocculating agent is PAM (polyacrylamide), the dosage of the PAM is 0.5mg/L, and discharging the water into a precipitation device after flocculation treatment;

sand-water separation: and recovering the fly ash in the precipitate.

2. The heavy medium fast settling water treatment method according to claim 1, wherein the sand-water separation step uses a hydrocyclone to separate fly ash from the sediment.

3. The heavy medium velocity settling water treatment method according to claim 1, wherein the fly ash used in the flocculation step has a diameter of 60 to 140 μm.