CN106809939B

CN106809939B - Method for keeping activity of removing ammonia nitrogen in surface water by catalytic oxidation of iron-manganese oxide

Info

Publication number: CN106809939B
Application number: CN201710028741.4A
Authority: CN
Inventors: 黄廷林; 张瑞峰; 章武首; 文刚; 彭林贤; 郭敏; 陈永攀; 张蓓蓓
Original assignee: Xian University of Architecture and Technology
Current assignee: Xian University of Architecture and Technology
Priority date: 2017-01-16
Filing date: 2017-01-16
Publication date: 2020-06-09
Anticipated expiration: 2037-01-16
Also published as: CN106809939A

Abstract

The invention provides a method for keeping the activity of removing ammonia nitrogen in surface water by catalytic oxidation of iron-manganese oxide, which is characterized in that in the process of removing ammonia nitrogen in water by using an active filter material catalytic oxidation method based on an iron-manganese oxide active filter membrane, phosphoric acid or phosphate is added into a water body before a high ammonia nitrogen surface water source is subjected to coagulating sedimentation or coagulating floatation treatment. The invention successfully realizes the application of the catalytic oxidation active filter material in the surface water condition. By adding phosphate, the ammonia nitrogen removal activity of the catalytic oxidation active filter material is well maintained. The continuous operation is carried out for 160 days (the water temperature is about 8 ℃), the average ammonia nitrogen concentration of the filter outlet water is always less than 0.1mg/L, and the ammonia nitrogen removal rate of the filter reaches more than 95%; after 160 days (the water temperature is between 6 and 8 ℃), the average ammonia nitrogen concentration of the effluent is 0.19mg/L and still below 0.5 mg/L. Then, the water temperature rises along with the seasonal change, and the ammonia nitrogen concentration of the effluent is gradually reduced.

Description

Method for keeping activity of removing ammonia nitrogen in surface water by catalytic oxidation of iron-manganese oxide

Technical Field

The invention belongs to the field of drinking water treatment, relates to a method for removing ammonia nitrogen in surface water, and particularly relates to a method for maintaining the activity of removing ammonia nitrogen in surface water by catalytic oxidation of iron-manganese oxide.

Background

Ammonia nitrogen is one of the main pollutants in surface water drinking water sources. The ammonia nitrogen concentration of a plurality of drinking water surface water sources exceeds the national water quality standard, and the ammonia nitrogen problem is an important problem in the water treatment industry. At present, the treatment technology of ammonia nitrogen in water mainly comprises the following steps: biological, chemical, physicochemical methods. The breakpoint chlorination is a common chemical method, and although ammonia nitrogen in water can be effectively removed, the breakpoint chlorination increases the dosage of chlorine, which leads to the rise of chlorination disinfection byproducts and has higher cost. The physical chemical adsorption method represented by activated carbon and zeolite requires periodic regeneration of the filter material, has high cost, and is only suitable for small-sized water plants. The biological method has good capability of removing ammonia nitrogen in water, so the biological method is always highly valued by people and is widely applied. But the ammonia nitrogen removal efficiency is low under the low-temperature condition in winter, which is a problem difficult to overcome by a biological method. The catalytic oxidation method based on the novel active filter material, which is newly developed in recent years by the subject group, has the advantages of high ammonia nitrogen removal efficiency, no secondary pollution, low maintenance cost, relatively small influence of temperature and the like compared with the traditional process. Therefore, the method has great application potential and obtains good production effect in the practice of treating ammonia nitrogen in underground water.

However, in the process of applying the active filter material to the removal of ammonia nitrogen in surface water, the removal capability of the active filter material to ammonia nitrogen in water begins to gradually decline after about two months of operation. This creates a serious obstacle to the popularization and use of the novel filter material.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a method for maintaining the activity of removing ammonia nitrogen in surface water by catalytic oxidation of iron-manganese oxide, and solves the problem that in the prior art, the ammonia nitrogen treatment capacity of a filter material is gradually reduced along with the lapse of operation time in the process of removing ammonia nitrogen in surface water by catalytic oxidation of an iron-manganese oxide modified active quartz sand filter material.

In order to solve the technical problems, the invention adopts the following technical scheme:

in the process of removing ammonia nitrogen in water by using an active filter material catalytic oxidation method based on a ferro-manganese oxide active filter membrane, for a high ammonia nitrogen surface water source after coagulating sedimentation or coagulating floatation treatment, phosphoric acid or phosphate is added into a water body before the high ammonia nitrogen surface water source enters normal filtration.

The invention also has the following distinguishing technical characteristics:

the ammonia nitrogen concentration of the high ammonia nitrogen surface water source is 0.5-2.8 mg/L.

The phosphoric acid is concentrated phosphoric acid with the mass concentration of 85%.

The phosphate is phosphate containing phosphate radical, hydrogen phosphate radical or dihydrogen phosphate radical.

Preferably, the phosphate is sodium dihydrogen phosphate, sodium hydrogen phosphate, sodium phosphate, potassium hydrogen phosphate or potassium dihydrogen phosphate.

The phosphoric acid or the phosphate is intermittently added under the condition that the environmental temperature is more than or equal to 13 ℃, the adding time is 7 days each time, the intermittent time is 30 days, and the adding amount is 5 mu g/L each time; continuously adding the mixture at the temperature of less than 13 ℃ with the adding amount of 30 mug/L.

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

the invention successfully realizes the application of the catalytic oxidation active filter material in the surface water condition. The catalytic oxidation active filter material is directly applied to the treatment of ammonia nitrogen in surface water (without adding phosphate), and the effect of the filter material gradually decreases along with the lapse of the operation time and the reduction of the water temperature (figure 8). Continuously operating for about 60 days (at the moment, the temperature is 17 ℃), and the ammonia nitrogen effluent of the filter tank reaches about 0.5 mg/L; the continuous operation is carried out for about 170 days (the water temperature is 6 ℃) and the concentration of the ammonia nitrogen in the effluent reaches about 1.5 mg/L.

By adding phosphate, the ammonia nitrogen removal activity of the catalytic oxidation active filter material is well maintained. The continuous operation is carried out for 160 days (the water temperature is about 8 ℃), the average ammonia nitrogen concentration of the filter outlet water is always less than 0.1mg/L, and the ammonia nitrogen removal rate of the filter reaches more than 95%; after 160 days (the water temperature is between 6 and 8 ℃), the average ammonia nitrogen concentration of the effluent is 0.19mg/L and still below 0.5 mg/L. Then, the water temperature rises along with the seasonal change, and the ammonia nitrogen concentration of the effluent is gradually reduced.

Meanwhile, the catalytic oxidation ammonia nitrogen removal effect realized by the method has obvious advantages compared with the mainstream biological method. The effect of the filter tank formed by the catalytic oxidation active filter material of 40cm and the common quartz sand filter material on treating ammonia nitrogen under the low-temperature condition in winter is shown in figure 11, and the filter tank has good treatment effect on ammonia nitrogen at different filter speeds. For the common biological activity filter, the ammonia nitrogen removal effect under the same experimental conditions is shown in figure 12, the ammonia nitrogen concentration of the outlet water of the filter is greatly influenced by the filtration rate, and the outlet water of the filter cannot reach the standard for a long time at the filtration rate of 8 m/h. Besides, the treatment effect of the common biological filter is interfered by back flushing in winter, and the interference of the catalytic oxidation filter is small.

Drawings

FIG. 1 is a block diagram of a process system.

FIG. 2 is a schematic process flow diagram.

Fig. 3 is an SEM image of the original filter material x 5000 in comparative example 1.

Fig. 4 is an SEM image of filter media x 5000 after several months for treating ammonia nitrogen in surface water in comparative example 1.

FIG. 5 is the EDS energy spectrum of the surface element of the original filter material in comparative example 1.

FIG. 6 is an EDS energy spectrum of surface elements of the filter material in comparative example 1 after several months of treatment of ammonia nitrogen in surface water.

FIG. 7 shows the effect of the filter material on ammonia nitrogen removal after phosphate addition in example 1.

FIG. 8 shows the effect of the filter material without phosphate on removing ammonia nitrogen in example 1.

FIG. 9 is the EDS energy spectrum of the surface element of the filter material after phosphate is added in example 1.

FIG. 10 is the EDS spectrum of the surface element of the filter in example 1 without addition of phosphate.

FIG. 11 shows the effect of ammonia nitrogen treatment in winter using a filter composed of 40cm of catalytic oxidation active filter material plus 80 cm of ordinary quartz sand filter material.

FIG. 12 shows the ammonia nitrogen removal effect of the common biological activated filter under the same experimental conditions as those of FIG. 11.

The meaning of the individual reference symbols in the figures is: a-high ammonia nitrogen raw water after coagulating sedimentation or coagulating air flotation treatment, B-medicament adding system, C-medicament mixing and aerating system, D-filtering system and E-treated water body reaching the standard;

1-a water inlet pipeline or a water inlet channel, 2-a metering pump, 3-a medicament storage and preparation system (respectively used for adding iron, manganese, potassium permanganate, phosphoric acid or phosphate), 4-a tubular mixer, 5-an air compressor, 6-an aeration mixing reaction tank, 7-an active filter material and 8-a filter tank.

The present invention will be explained in further detail with reference to examples.

Detailed Description

According to the technical scheme, as shown in fig. 1 and 2, the ferro-manganese modified active quartz sand filter material 7 is cultured under certain conditions to be mature, and then is filled in a filter 8 to serve as a filter material. Firstly, adding required medicament in a water inlet pipeline or channel 1 of a high ammonia nitrogen surface water source A subjected to coagulation air flotation or coagulation sedimentation treatment. The type, amount, condition and mode of adding the medicament are the core of the method. High-concentration stock solution of phosphoric acid/phosphate (sometimes appropriate amount of low-valence iron manganese and potassium permanganate are needed to be supplemented) is stored in a medicament storage device 3, is quantitatively added into a water inlet pipeline or channel 1 through a dosing pipeline by a metering pump 2, is mixed by a tubular mixer 4, then enters a mixed aeration reaction tank 6, and is blown by compressed air by an air compressor 5 to mix the water again and oxygenate. Then the water flows into a filter 8, is filtered by an active filter material 7, and the ammonia nitrogen in the water is efficiently removed through a series of chemical and biological reactions, so that the water quality of the outlet water reaches the national drinking water quality standard.

The active filtering material based on the ferro-manganese oxide active filtering membrane is hereinafter referred to as filtering material, and the ferro-manganese oxide active filtering membrane of the filtering material is coated on the quartz sand filtering material.

The present invention is not limited to the following embodiments, and all equivalent changes based on the technical solutions of the present invention fall within the protection scope of the present invention.

Comparative example 1:

the embodiment provides a method for removing ammonia nitrogen activity in surface water by catalytic oxidation, wherein a filter material adopted is an active filter material based on a ferro-manganese oxide active filter membrane, and the specific process is as follows.

In the initial stage of operation of the filter material under the surface water condition, the ammonia nitrogen in the outlet water of the filter is mainly limited by dissolved oxygen, and the concentration of the ammonia nitrogen in the outlet water of the filter is generally kept between 0.5 and 0.8mg/L under the condition of 2.5mg/L of the ammonia nitrogen in the inlet water. After the operation is about 30 days, the ammonia nitrogen concentration of the outlet water of the filter tank begins to rise, and the ammonia nitrogen concentration of the outlet water reaches about 1.5mg/L after 45 days, which shows that the ammonia nitrogen removal effect of the filter material is obviously reduced, and the filter material in the filter tank is taken for measurement, as shown in figures 3 to 6.

As can be seen from the scanning electron micrographs of fig. 3 and 4, the iron-manganese oxide piled in a granular form can be seen on the surface of the original filter material, and the surface of the original filter material is porous and spongy; after several months of operation under surface water conditions, the filter material surface is as shown in fig. 4, and the surface is obviously covered by other impurities in the water.

As can be seen from the energy spectrum diagrams of FIG. 5 and FIG. 6, after the filter material is applied to the treatment of ammonia nitrogen in surface water for months, Al elements on the surface of the filter material are accumulated in a large amount, and the types of other main elements are unchanged. According to measurement, a large amount of aluminum salt coagulant residues exist in the filter inlet water under the surface water condition. The Al is mainly from the residue of an aluminum salt coagulant in a coagulating sedimentation stage or a coagulating floatation stage. The coagulant residues are considered to be attached to the surface of the filter material and combined with the active sites on the surface of the filter material, so that the ammonia nitrogen removal activity of the filter material is reduced.

In order to solve the problem, the technical idea is as follows: and adding a certain amount of phosphate into the water body to be treated, and preventing the residue of the aluminum salt coagulant from being combined with the surface of the filter material through the strong combination of the phosphate and the aluminum salt so as to keep the catalytic oxidation activity of the filter material.

Example 1:

in the method, in the process of removing ammonia nitrogen in water by using an active filter material catalytic oxidation method based on a ferro-manganese oxide active filter membrane, phosphate is added into a water body before a high ammonia nitrogen surface water source is subjected to coagulating sedimentation or coagulating floatation treatment before the high ammonia nitrogen surface water source enters normal filtration.

The phosphate is a phosphate containing phosphate, hydrogen phosphate or dihydrogen phosphate.

In this embodiment, the phosphate is sodium dihydrogen phosphate, sodium hydrogen phosphate, sodium phosphate, potassium hydrogen phosphate, or potassium dihydrogen phosphate, and the phosphate may be replaced by concentrated phosphoric acid having a mass concentration of 85%. For convenience of experiment, sodium dihydrogen phosphate is used as a representative.

The dosage of phosphoric acid or phosphate is determined according to specific water quality conditions and running time.

In the embodiment, phosphoric acid or phosphate is intermittently added under the condition that the environmental temperature is more than or equal to 13 ℃ (summer), wherein the adding time is 7 days each time, the intermittent time is 30 days, and the adding amount is 5 mug/L each time; continuously adding the mixture under the condition that the environmental temperature is less than 13 ℃ (winter), wherein the adding amount is 30 mug/L.

In order to maintain the ammonia nitrogen removal activity of the active filter material and reduce the coverage of impurities in water on active sites on the surface of the filter material, the turbidity of the effluent after coagulating sedimentation is less than 2 NTU.

In order to keep the ammonia nitrogen removal activity of the filter material and simultaneously reduce the growth of microorganisms in a water treatment system, the adding point of phosphoric acid or phosphate is a pipeline and a channel which are close to a filter tank after coagulating sedimentation or coagulating air floatation treatment.

In addition, for the active filter material with reduced activity, the activity recovery method is characterized in that the temperature is above 14 ℃, the treatment capacity of the filter can be recovered to a higher level after 30 mu g/L phosphate is added for running for about 6 days, and when the temperature is lower than 6 ℃, the activity of the filter material is obviously improved by adding 30 mu g/L phosphate for running for 18 days.

The practical application effect of the method is tested by a pilot scale surface water plant (the water yield is 96 m)³The results are shown in FIGS. 7 and 8. The result shows that the removal rate of the iron-manganese composite oxide active filter material to the ammonia nitrogen in the surface water is kept above 90 percent (the filtration rate is 7m/h, and the average ammonia nitrogen concentration of the inlet water is about 2mg/L) even under the low-temperature condition in winter (the lowest water temperature is about 6 ℃) by adding phosphoric acid/phosphate into the surface water according to the method.

And the activity of a filtering system which does not adopt the method for adding the medicament is obviously reduced after about 40 days of operation, and the concentration of the ammonia nitrogen in the effluent water in winter is higher to 1.5 mg/L. Therefore, the method is proved to be efficient, practical and easy to popularize in the actual production process.

After the filter material is used for treating surface water for several months, the filter material is taken out from the phosphate adding filter tank and the phosphate non-adding filter tank respectively to carry out surface element content analysis on the active filter membrane, and the results are shown in figures 9 and 10. The mass ratio of aluminum elements on the surface of the filter material added into the phosphate filter is obviously lower than that of the filter material not added into the phosphate filter, and the addition of the phosphate is basically consistent with the initial technical hypothesis, so that the accumulation effect of Al on the surface of the filter material is weakened, and the catalytic oxidation activity of the active filter membrane is well maintained.

In order to further determine the content of the Al element on the surface of the filter material, XPS energy spectrum analysis is carried out on the surface element of the filter material, and the result shows that the mass percentage of the Al element on the surface of the filter material is 4.17% under the condition of adding phosphate and 8.07% under the condition of not adding phosphate. Consistent with the results of the EDS analysis.

Claims

1. A method for keeping the activity of removing ammonia nitrogen in surface water by catalytic oxidation of iron-manganese oxide is characterized in that in the process of removing ammonia nitrogen in water by using an active filter material catalytic oxidation method based on an iron-manganese oxide active filter membrane, phosphoric acid or phosphate is added into a water body before a high ammonia nitrogen surface water source subjected to coagulating sedimentation or coagulating floatation treatment enters normal filtration, so that the combination of aluminum salt residue of a coagulant and the surface of a filter material is prevented, and the catalytic oxidation activity of the filter material is further kept.

2. The method according to claim 1, wherein the ammonia nitrogen concentration of the high ammonia nitrogen surface water source is 0.5-2.8 mg/L.

3. The method of claim 1, wherein the phosphoric acid is concentrated phosphoric acid having a mass concentration of 85%.

4. The method of claim 1, wherein the phosphate salt is a phosphate salt comprising phosphate, hydrogen phosphate, or dihydrogen phosphate.

5. The method of claim 4, wherein the phosphate salt is monobasic sodium phosphate, dibasic sodium phosphate, potassium phosphate, dibasic potassium phosphate, or monobasic potassium phosphate.

6. The method according to claim 1, wherein the phosphoric acid or phosphate is intermittently added at an ambient temperature of 13 ℃ or higher for 7 days each time, for 30 days each time, and in an amount of 5 μ g/L each time; continuously adding the mixture at the temperature of less than 13 ℃ with the adding amount of 30 mug/L.