CN114477397A

CN114477397A - Coagulant and preparation method and application thereof

Info

Publication number: CN114477397A
Application number: CN202210033283.4A
Authority: CN
Inventors: 张健; 易境; 侯丹; 史文燕; 万丽
Original assignee: Hunan Youqing Intelligent Equipment Co ltd
Current assignee: Hunan Youqing Intelligent Equipment Co ltd
Priority date: 2022-01-12
Filing date: 2022-01-12
Publication date: 2022-05-13

Abstract

The invention discloses a coagulant, a preparation method and application thereof. The coagulant comprises the following components in parts by weight: polymeric ferric sulfate: 5-90 parts by weight; powder sand: 1-50 parts by weight; the particle size of the silt is 20-60 mu m. The coagulant forms a flocculation core by using PS (polystyrene), promotes the rapid sedimentation and efficient concentration of the discharged muddy water, improves the concentration effect of the discharged muddy water by 22 percent, and increases the solid flux to 6.0 kg/(m)²h) Meanwhile, the concentration load of the discharged muddy water with the concentration of 4000mg/L can be coped with, PAM adding is abandoned, and the quality safety of the reuse water is improved.

Description

Coagulant and preparation method and application thereof

Technical Field

The invention belongs to the technical field of sewage treatment, and particularly relates to a coagulant, and a preparation method and application thereof.

Background

The production wastewater of the water purification plant accounts for about 6-10% of the total water yield of the water purification plant, and contains a large amount of suspended matters, organic matters, heavy metals and microorganisms intercepted from raw water. If the part of wastewater is directly discharged into a natural water body, a certain harm is caused to the ecological environment, and if the part of wastewater is discharged into a sewage pipe network, the problem of low carbon-nitrogen ratio in sewage treatment is caused, and meanwhile, water resources are wasted. Therefore, the effective recycling of the production wastewater is an indispensable part in the future water purification treatment.

At present, most of processes for treating sludge water in waterworks have the problems of adjustment, concentration, pretreatment (balance) and dehydration treatment, but the treatment has the problems of high coagulant adding amount, potential water quality safety hazard and the like. For example, some waterworks treated the sludge water with PAM (polyacrylamide), and some waterworks treated the sludge water with PAC and PAM, and the average dosage was 40mg/L and 7 mg/L. However, excessive accumulation of Al in the human body may cause alzheimer's disease, resulting in mutation of somatic and germ cells. Monomer Acrylamide (AM) generated by decomposition of PAM is also highly toxic, is a two-class carcinogen, can cause gene mutation, and can cause cell DNA damage after long-term contact. Therefore, in order to ensure the safety of the quality of drinking water, a method for safely, efficiently and economically treating the muddy water is further sought.

Disclosure of Invention

The first technical problem to be solved by the invention is as follows:

provided is a coagulant. The coagulant forms a flocculation core by using PS, and aims to reduce the addition of the coagulant and save the running cost while improving the concentration effect of discharged muddy water and the safety of water quality.

The second technical problem to be solved by the invention is:

provides a preparation method of the coagulant.

The third technical problem to be solved by the invention is:

the application of the coagulant is provided.

In order to solve the first technical problem, the invention adopts the technical scheme that:

the coagulant consists of the following components in parts by weight:

5-90 parts of polymeric ferric sulfate;

1-50 parts of silt.

According to one embodiment of the invention, the silt particle size is 20-60 μm.

The silt has the particle size of 20-60 mu m, and has high density and high adsorbability, so that the silt is easily adsorbed with flocs, and a high-efficiency concentration effect is generated.

The coagulant can enable a sewage treatment processThe surface load in the concentration tank is increased by at least 2 times, and the internal surface load of the concentration tank added with the coagulant can reach at least 2.3 (m)³/m²·h)。

The silt comes from harmless river sand, and has large reserve and low cost.

The coagulant is not added with PAM, so that the water quality safety of the reuse water is improved.

When the particle size of the particles suspended in water is small to a certain extent, the energy of brownian motion of the particles is sufficient to prevent the action of gravity, so that the particles do not settle. Such suspensions can be maintained in a stable state for a long period of time. Furthermore, the surface of the suspended particles tends to be charged (often negatively), and the repulsion of like charges between the particles makes the particles less likely to coalesce and grow larger, thereby increasing the stability of the suspension. The coagulation process is to add a positively charged coagulant to neutralize the negative electricity on the particle surface and destabilize the particles. Then, the particles are bonded to each other by the action of collision, surface adsorption, attraction, or the like, and are separated from the water.

In the coagulant, on one hand, PAM addition is abandoned, on the other hand, polyferric sulfate (PFS) is added into the discharged muddy water, Powder Sand (Powder Sand, PS) with different proportions is compounded to form a flocculation core by utilizing PS, the rapid sedimentation and efficient concentration of the discharged muddy water are promoted, the feeding amount of the coagulant is reduced while the concentration effect and the water quality safety of the discharged muddy water are improved, the operation cost is saved, and the turbidity of the supernatant and organic matters (TOC and UV) after the discharged muddy water is concentrated are researched₂₅₄) And the content of metals (Al, Fe, Mn and the like) to evaluate the recycling safety of the sludge discharge water.

The coagulant can improve the concentration effect of the discharged muddy water by 22 percent and increase the solid flux to 6.0 kg/(m)²h) Meanwhile, the concentration load of the discharged muddy water with the concentration of 4000mg/L can be handled.

According to one embodiment of the invention, the ratio of the polymeric ferric sulfate to the powder sand is 5-9 parts by weight: 1-5.

According to one embodiment of the invention, the ratio of the polyferric sulfate to the silt by weight is 8: 2.

aiming at the sludge discharge water with different SS contents (solid suspension concentration), the weight part ratio of the polymeric ferric sulfate to the powder sand is 5-9: 1-5, the turbidity of the discharged water can be effectively reduced, but when the weight part ratio of the polymeric ferric sulfate to the powder sand is 8:2, the turbidity of the discharged water can reach at least 3 NTU.

According to one embodiment of the invention, the iron element content of the polyferric sulfate is 18-28% by mass.

According to one embodiment of the invention, the iron element in the polyferric sulfate accounts for 22% by mass.

In order to solve the second technical problem, the invention adopts the technical scheme that:

a method of preparing said coagulant comprising the steps of:

and mixing the polymeric ferric sulfate and the silt to obtain the coagulant.

In another aspect of the invention, the method for treating the sludge discharge water comprises the steps of putting the coagulant into the sludge discharge water, separating the sludge discharge water, recovering supernatant and dehydrating lower concentrated solution.

According to one embodiment of the invention, when the concentration of the discharged muddy water is less than or equal to 2500mg/L, the mass percent of the added coagulant powder is 40-50%; when the concentration of the discharged muddy water is more than 2500mg/L, the mass percentage of the added coagulant powder is 25-35%.

Under the condition of different sludge water concentrations, when the coagulants are added in different proportions, the sludge water concentration effect is influenced.

In a further aspect of the invention, there is also provided the use of a coagulant in the treatment of wastewater.

According to one embodiment of the invention, the step of treating the wastewater with the coagulant comprises:

(1) and mechanically stirring and coagulating the coagulant and the sludge discharge water, and feeding the mixture into a concentration tank after stirring.

(2) After the sludge water is concentrated, the supernatant is fed back to the head end of tap water treatment for reuse, and the concentrated water is conveyed to a dehydration room for dehydration.

One of the technical solutions has at least one of the following advantages or beneficial effects:

1. the coagulant forms a flocculation core by using PS (polystyrene), promotes the rapid sedimentation and efficient concentration of the discharged muddy water, improves the concentration effect of the discharged muddy water by 22 percent, and increases the solid flux to 6.0 kg/(m)²h) Meanwhile, the concentration load of the discharged muddy water with the concentration of 4000mg/L can be coped with;

2. harmless river sand is selected and is ground to prepare PS with the particle size of 20-60 mu m, and the PS has high density and high adsorbability, so that the PS is easily adsorbed with floc, the coagulant can generate an efficient concentration effect, and the water quality safety of reuse water is ensured;

3. the coagulant has simple configuration and low cost, and can be used for large-scale production.

4. The coagulant abandons PAM feeding and improves the water quality safety of reuse water.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a particle size distribution diagram of silt particles of examples 1 to 45.

FIG. 2 is a test of the mixture ratio of polyferric sulfate to silt in the coagulant prepared in examples 1 to 45.

FIG. 3 is a test of the adding amount of polymeric ferric sulfate and silt in the coagulant prepared in examples 1-45.

FIG. 4 is a Box-Benhnken model of examples 1-45 with factors of suspended solids and dosing.

FIG. 5 is a Box-Benhnken model of examples 1-45 with the influence factor of suspended solids and mixture ratio.

FIG. 6 is a Box-Benhnken model of examples 1 to 45 in which the influence factors are the addition amount and the mixture ratio.

Fig. 7 is a treatment test chart of the total organic carbon content in the coagulant-treated sample prepared in example 14.

Fig. 8 is a graph of absorbance measurements in a sample treated with the coagulant prepared in example 14.

Fig. 9 is a settling property test chart of the coagulant-treated sludge water prepared in example 14.

Fig. 10 is a solid flux test chart of the sludge water treated with the coagulant prepared in example 14.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the scope of the present invention.

In the examples, the polyferric sulfate (PFS) was food grade (solid powder), and the mass percentage of iron element in the polyferric sulfate (PFS) was 22.02%.

The coagulant is prepared in the following examples 1 to 45 by the following method, and the components are weighed according to table 1, and the method specifically comprises the following steps:

and mixing the polymeric ferric sulfate and the silt to obtain the coagulant.

TABLE 1

In the examples, the silt particle size is 20 to 60 μm, D₅₀21 μm, and the particle size distribution thereof is shown in FIG. 1.

In examples 1 to 9, the ratio of the amount of PFS to the amount of PS added was 9:1, and the total amount added was 5 to 80 mg/L.

In examples 10 to 18, the ratio of the amount of PFS to the amount of PS added was PFS: PS 8:2, and the total amount added was 5 to 80 mg/L.

In examples 19 to 27, the ratio of the amount of PFS to the amount of PS added was PFS: PS: 7:3, and the total amount added was 5 to 80 mg/L.

In examples 28 to 36, the ratio of the amount of PFS to the amount of PS added was 6:4, and the total amount added was 5 to 80 mg/L.

In examples 37 to 45, the ratio of the amount of PFS to the amount of PS added was 5:5, and the total amount added was 5 to 80 mg/L.

And (3) performance testing:

for the raw materials for preparing the coagulant in examples 1 to 45: PFS and PS were subjected to composition analysis, and the results are shown in Table 2.

TABLE 2

In order to test the influence of the mixture ratio of different polymeric ferric sulfate and silt in the coagulant on the technical effect, the mixture ratio of the polymeric ferric sulfate and the silt is tested, and the result is shown in fig. 2. As can be seen from FIG. 2, the turbidity of the supernatant gradually decreased with the increase of the amount of PS-PFS, and the decrease trend began to become gentle with the amount of PS-PFS >40mg/L, and the turbidity was below 3 NTU.

For further testing, in the coagulant, the adding amount test of the polymeric ferric sulfate and the silt is carried out on the influence of different proportions of the polymeric ferric sulfate and the silt on the technical effect, and the result is shown in fig. 3.

As can be seen from FIG. 3, the concentration effect of the discharged muddy water can be further improved by using the PS-PFS composite flocculant. When the PS ratio is 10%, the concentration effect of the coagulant on SV30 is weak, and the delta SV30 is not improved to a large extent along with the increase of the addition amount. When the iron sand proportion is 20% and 30%, the concentration effect is obviously improved, and the delta SV30 is increased along with the increase of the adding amount, and can reach 17% at most; when the PS ratio is increased to 40%, the value of delta SV30 is high, the influence of the coagulant addition on the concentration effect of the discharged muddy water is weak, and the value of delta SV30 fluctuates between 13.5% and 14.5%. When the proportion reaches 50%, the concentration effect is obviously reduced, and even if the adding amount reaches 80mg/L, the delta SV30 is only 8%.

For further testing, the Box-Benhnken model is designed for the influence of the mixture ratio of different polymeric ferric sulfate and silt in the coagulant on the technical effect, and the results are shown in FIGS. 4-6.

On the basis of a single-factor experiment, according to the Design of a Box-Benhnken model, a Design-Expert8.0 software is used for carrying out multiple regression fitting analysis, and three influence factors of drainage water SS (A), compound flocculant adding amount (B) and PS ratio (C) are respectively selected by taking delta SV30(Y) as an evaluation index to determine the optimal compound flocculant adding working condition. The levels of the design factors for the Box-Behnken experiment are shown in Table 3. The experimental results are subjected to regression analysis and plotting by Design-expert.V8.0.6 software to obtain three-dimensional response curves between delta SV30 and respective variables, which are shown in FIGS. 4, 5 and 6.

As can be seen from the graphs of FIG. 4, FIG. 5 and FIG. 6, under the condition of different concentrations of the discharged muddy water, when PS-PFS is added, the optimal parameter solution of the adding amount and the powder-sand ratio exists. According to the change of the concentration of the original sludge water, 2500mg/L is used as a dividing point, the sludge water is divided into a conventional concentration and a higher concentration, and the optimal PS ratio and the composite flocculant are added into a table 4 under different concentrations.

TABLE 3 Box-Behnken Experimental factors and levels

TABLE 4 dosage of the best compound flocculant (silt particle size: 20 to 60 μm)

And carrying out organic matter content treatment test on the coagulant. The coagulant used was the coagulant prepared in example 1.

Organic matter detection was performed on the raw water, raw sludge water, concentrated supernatant, and bottom sludge dewatering filtrate, and the detection results are shown in fig. 7 and 8.

As can be seen from FIG. 7, the TOC content of the raw water was the lowest, with an average of 2.4 mg/L. The organic matter content in the sludge water can be effectively reduced by adding chemicals and concentrating, the TOC of the original sludge water is reduced to 2.8mg/L from 4.0mg/L, which is lower than the limit value of 5mg/L specified in GB5749-2006, and the standard requirement is met. The TOC content of the bottom sludge dehydration filtrate is 5.6mg/L, which is higher than that of raw water and is also higher than the drinking water standard.

UV₂₅₄Reflecting the humic organic matters with double bonds, benzene rings and other unsaturated bonds, and the organic matters have obvious correlation with disinfection by-product precursor (THMFP) with 'three-cause' effect. As can be seen from FIG. 8, the muddy water UV is discharged₂₅₄The response value is 0.078cm^-1Lower than 0.085cm of raw water^-1Adding medicine and concentrating to obtain supernatant UV₂₅₄The response value is lower than that of the sludge water and is 0.061cm^-1. This is because UV₂₅₄The flocculant is unsaturated hydrocarbon organic matter containing polar groups such as carboxylic acid and hydroxyl, and the hydrolysate of the flocculant has positive charges to promote partial UV₂₅₄Is removed by means of potential binding with the flocculant hydrolysate. Bottom sludge dewatering filtrate UV₂₅₄The response value was 0.113cm^-1The recycling of the sediment dehydration filtrate is obviously higher than that of the raw water, the increased risk of THMFP can be increased, and the sediment dehydration filtrate is not recommended to be recycled for ensuring the water quality safety of drinking water.

The river basin industry develops rapidly, and poisonous and harmful heavy metal often appears standard exceeding phenomenon in some river reach, in addition, can make some metal ion concentration rise when throwing the coagulating agent in the muddy water treatment process, consequently must detect the metal ion content in the retrieval and utilization water.

The metallic ion content test was performed on the sewage treated with the coagulant prepared in example 1, and the results are shown in table 5.

TABLE 5 Metal ion content and Limit (. mu.g/L)

The content of each metal ion of different water samples and the limit value in the GB5749-2006 standard are shown in Table 5. It can be seen that the contents of Al and Fe ions in the supernatant are both far lower than the national standard limit. The concentration of Mn ions in the discharged sludge water can reach 89.4 mu g/L to the maximum and is far higher than that of raw water by 1.02 mu g/L, which indicates that Mn is enriched in the discharged sludge water. After precipitation with PS-polyferric sulfate (PFS), the Mn content decreases, averaging 31.78. mu.g/L, which is less than the 100. mu.g/L limit. In addition, the contents of other heavy metals are all below the standard limits. Therefore, the clear liquid on the sludge discharge water can be recycled.

The effluent treated with the coagulant prepared in example 1 was subjected to sludge water settling characteristics, and the results are shown in fig. 9.

The effluent treated with the coagulant prepared in example 1 was subjected to a sludge water solid flux test, and the results are shown in fig. 10.

In order to deal with the sudden high-concentration sludge discharge water, 4000mg/L is taken as the designed concentration of the sludge discharge water, and the corresponding solid flux G is 6.0 kg/(m)³h) Higher than 0.5-1.0 kg/(m) in the design Standard for outdoor Water supply (GB50013-2018)³h) The value of (a). And calculating the surface load of the concentration tank according to the solid flux, wherein the calculation formula is as follows:

q＝G_L/C₀

in the formula: q is surface load, (m)³/m²·h)；G_LAs the solid flux, (kg/(m)³·h))；C₀The average concentration of influent and discharged sludge level is (kg/m)³) The highest concentration during the experiment was chosen to be 2596 mg/L.

Calculated to give a concentrate pool surface load of 2.3 (m)³/m²H) 1.0 (m) above a conventional concentration tank³/m²H) limit.

The advantage that concentration tank surface load is high lies in: the tank capacity of the concentration tank can be reduced, the size of the mud scraper is reduced, and the civil engineering and operating cost is reduced.

The coagulant of the invention is tested for operation cost.

1.2 ten thousand meters of sludge water of a long sand water plant³The/d process scale is taken as an example and the area of the concentration tank, the power of the mud scraper and the cost of the chemicals are calculated. The coagulant is added in an amount of 40mg/L, the powder sand proportion is 40%, PS does not need to be recovered, and the base sludge is dehydrated and then is externally used along with mud cakes. Two production lines are arranged in a water plant, two groups of concentration tanks are arranged in each production line, the areas of the concentration tanks and the power of the mud scrapers are shown in a table 6, and the medicament cost is calculated in a table 7 respectively.

TABLE 6 area of concentration tank and power of mud scraper

TABLE 7 cost of the agents

It can be seen that with the coagulant, at 1.2 km³In the sludge water concentration treatment of the/d, the diameter of a single-group concentration tank is 8m, the driving power of a single-group sludge scraper is 0.037kW, the cost of a medicament for per ton of water is 0.086 yuan, and the cost of an annual medicament is 37.84 ten thousand yuan, so that the annual medicament cost is reduced by 7.71 ten thousand yuan compared with the method of independently adding Polymeric Ferric Sulfate (PFS).

The above description is only an example of the present invention and is not intended to limit the scope of the present invention, and all equivalent modifications made by the present invention as described in the specification of the present invention or directly or indirectly applied to the related technical fields are included in the scope of the present invention.

Claims

1. A coagulant, which is characterized in that: the composition comprises the following components in parts by weight:

5-90 parts of polymeric ferric sulfate;

1-50 parts of silt.

2. A coagulant as claimed in claim 1 wherein: the particle size of the silt is 20-60 mu m.

3. A coagulant as claimed in claim 1 wherein: the weight part ratio of the polymeric ferric sulfate to the powder sand is 5-9: 1-5.

4. A coagulant as claimed in claim 1 wherein: the weight part ratio of the polyferric sulfate to the silt is 8: 2.

5. a coagulant as claimed in claim 4 wherein: the mass percentage of the iron element in the polymeric ferric sulfate is 18-28%, and the preferred mass percentage is 22%.

6. A process for the preparation of a coagulant according to any one of claims 1 to 5, characterized in that: the method comprises the following steps:

and mixing the polymeric ferric sulfate and the silt to obtain the coagulant.

7. A method for treating sludge water is characterized in that: a coagulant according to any one of claims 1 to 5 is put into the discharged muddy water, the discharged muddy water is separated into layers, the supernatant is recovered, and the lower concentrated solution is dehydrated.

8. The method of claim 7, wherein: when the concentration of the discharged muddy water is less than or equal to 2500mg/L, the mass percent of the silt in the added coagulant is 40-50%; when the concentration of the discharged muddy water is more than 2500mg/L, the mass percentage of the added coagulant powder is 25-35%.

9. Use of a coagulant according to any one of claims 1 to 5 in the treatment of wastewater.