CN115072937A

CN115072937A - Pretreatment process for solving biological pollution of water treatment membrane

Info

Publication number: CN115072937A
Application number: CN202210832109.6A
Authority: CN
Inventors: 曾晶; 徐岩松; 郭建; 王爱菊
Original assignee: Shandong Chenguang Environmental Protection Equipment Co ltd
Current assignee: Shandong Chenguang Environmental Protection Equipment Co ltd
Priority date: 2022-07-15
Filing date: 2022-07-15
Publication date: 2022-09-20

Abstract

The invention discloses a pretreatment process for solving biological pollution of a water treatment membrane, which comprises the following steps: a biological reaction treatment step and a biological inhibition environment conditioning step. The pretreatment process for solving the biological pollution of the water treatment membrane is suitable for pretreatment of various membrane treatment systems of any raw water, including heavily polluted surface water. Seawater and reclaimed water can also be treated. By selecting different membrane filtration systems, water of any purity can be produced, including normal/potable/pure/ultrapure water as required by the pharmaceutical industry. The invention can reduce the membrane biological pollution of the subsequent membrane treatment process, reduce the cleaning times of the membrane and prolong the service life of the membrane.

Description

Pretreatment process for solving biological pollution of water treatment membrane

Technical Field

The invention relates to a pretreatment process for solving biological pollution of a water treatment membrane, belonging to the field of application of water treatment technology.

Background

The production water (reclaimed water/drinking water/pure water/ultrapure water) enters a production area, firstly enters a water storage system (production water tank), is sent into a desalted water raw water tank through a water pump, is pressurized through the water pump, is pretreated through a multi-media filter and ultrafiltration, and enters an ultrafiltration production water tank. And then the desalted water is produced by a water pump through a cartridge filter and a reverse osmosis membrane.

In order to ensure the effective control of reverse osmosis membrane influent microorganisms, the influent is sterilized by stages and in the whole process according to seasonal water temperature changes, meanwhile, the drug resistance and drug resistance of the microorganisms are prevented, the oxidizing bactericide is used as the main part, two non-oxidizing bactericides are used as the auxiliary part for alternate sterilization, the growth and breeding outbreak of the microorganisms are prevented, the preventive sterilization is emphasized, and the long-period normal operation of production is ensured.

In the technical process of producing boiler feed water and industrial desalted water by using a reverse osmosis technology, microbial contamination on a reverse osmosis membrane frequently occurs and normal operation of a device is influenced. The biologically contaminated reverse osmosis membranes can suffer from the following problems: 1) the biological pollution of the reverse osmosis membrane element seriously affects the performance of a reverse osmosis device, and the rapid increase of the pressure difference between inlet water and concentrated water occurs, so that the mechanical damage of the membrane element and the reduction of water yield are caused. 2) The water producing side of the membrane element is also subject to biological contamination, resulting in contaminated product water. Once a biofilm is produced, cleaning is very difficult. 3) Since the biofilm protects the microorganisms from the hydraulic shear forces and from the disinfection action of the chemicals, moreover, a biofilm that has not been thoroughly removed will cause a further rapid growth of microorganisms.

Chinese patent CN 104014247A discloses a sterilization method for preventing microorganisms from polluting a reverse osmosis membrane, which mainly comprises the steps of continuously adding an oxidizing bactericide NaClO5% solution into a raw water tank, continuously adding a reducing agent NaHSO35% W/V solution after ultrafiltration to thoroughly remove residual chlorine, controlling the pH value of inlet water at a reverse osmosis inlet to be 7.1-7.4, and monitoring and controlling the ORP (oxidation-reduction potential) before a security filter to be 200-300 mv. The invention adopts the oxidizing bactericide as the main component and two non-oxidizing bactericides to alternately perform preventive sterilization. The disadvantage is that the bactericide cannot completely kill the microorganisms because the microorganisms have drug resistance and drug resistance, and the killed microbial residues become nutrient substances for other microorganisms, which aggravates membrane bio-contamination.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: provides a pretreatment process for solving the problem of biological pollution of a water treatment membrane.

In order to achieve the aim, the pretreatment process provided by the invention consists of two parts: a biological reaction treatment step and a non-oxidative biostatic environmental conditioning step.

In practical production application, raw water can enter a membrane treatment system (a preferred membrane filtration system is generally adopted after the raw water is treated by the process, particularly a reverse osmosis membrane) for subsequent further treatment after being pretreated by the process equipment.

For example, producing drinking water. The raw water firstly enters the first part of the process, namely a biological reaction treatment step. A positive active biological community is established in a bioreactor, namely a good microbial growth environment is created, various microbial communities are bred, and 80 to 90 percent of biodegradable total organic carbon TOC in raw water can be removed by the method, so that the content of the remaining total organic carbon TOC meets the index of drinking water.

The effluent after most of organic substrate is removed enters a second part of the process, namely a biological inhibition environment conditioning step, and a non-oxidative biological inhibitor is added to further prevent the metabolism of microbial substances. The invention abandons the traditional method of adding chlorine for sterilization, adopts the method of adding biological inhibitor (namely, the growth and the reproduction of microorganisms are reduced to the maximum extent by a system) to prepare reclaimed water/drinking water/pure water/ultrapure water, and the water preparation is more economical.

The invention relates to a method for inhibiting the growth of bacteria by the following two measures in process technology, wherein a small amount of microorganisms still remain in effluent through a bioreactor:

1. absence of organic matrix, i.e., absence of biodegradable total organic carbon;

2. adding a biotoxicity inhibitor to effectively inhibit substance metabolism through strong biotoxicity.

Therefore, after the two processes, the membrane biological pollution of the subsequent membrane treatment process is reduced. If no biostatic agent is added after the bioreactor, the microorganisms may utilize the remaining degradable total organic carbon TOC within certain range of conditions to form biofilm contamination.

The pretreatment process device connects two reaction stages (namely a biological reaction treatment step and a biological inhibition conditioning step) in series, and can remove the total organic carbon TOC of the biodegradable carbon by 80 to 90 percent under the synergistic action of the consumption of raw water organic matrix and the biological inhibition, thereby decisively reducing the possibility of forming biological pollution (membrane biological pollution) of a membrane treatment system.

The traditional pretreatment process for preparing high-purity reclaimed water/drinking water/pure water/ultrapure water generally adopts physical filtration treatment facilities such as a multi-media filter and the like, and adds a chlorine-containing disinfectant for sterilization. Practice proves that the effect of adding the chlorine-containing disinfectant for sterilization cannot achieve the effect of adding the biological inhibitor at all. Since the subsequent membrane treatment stage is sensitive to chlorine in the feed water, the excess chlorine in the water must be dechlorinated.

The invention discovers that: if the influent water is dechlorinated, then sterilization leaks can develop in subsequent treatment stages, which can lead to significant microbial growth in the final treatment stage. Since chlorine acts as an oxidizing disinfectant to lyse the cellular structure of microorganisms by chemical oxidation, the oxidatively lysed biomass will become an organic matrix for the biological metabolic processes in the subsequent bactericidal leak.

In membrane filtration, the permeability of the membrane determines the purity of the effluent after removal of impurities. Especially total organic carbon TOC in the form of dissolved or colloid is intercepted on the inlet side of the membrane surface, and if the organic matter is easily degraded or the organic matter which is difficult to degrade is cracked by chlorine oxidation, the organic matter is more easily absorbed and utilized by microorganisms, namely, the material conditions required by the metabolism of the microorganism are formed. Thus, the surface of the membrane is easy to form a biological membrane.

The present invention is to find out this risk in practice and to circumvent this risk by eliminating the addition of chlorine-containing disinfectants and the toxic effect of the use of biological inhibitors on the microorganisms. The membrane filtration system cleaning cycle time interval is much longer due to the reduced biofilm formation. This means that expensive chemicals used in production and shut-down are saved, so the process improves the economics of the process.

The invention is applicable to the pretreatment of various membrane treatment systems for any raw water, including heavily polluted surface water. Seawater and reclaimed water can also be treated. By selecting different membrane filtration systems, water of any purity can be produced, including normal/potable/pure/ultrapure water as required by the pharmaceutical industry.

In a further development of the invention, it is proposed to use, during the stage of the inhibition conditioning step, heavy metal inorganic compounds, preferably copper sulfate or copper chloride, which are toxic to microorganisms. It has been found that by dosing a salt solution containing heavy metals, the growth of microorganisms can be prevented even in water containing degradable total organic carbon TOC.

The process records the degree of bacterial contamination, i.e. the metabolism of microbiological materials between the biostatic regulator and the subsequent membrane treatment stages of the process, and adjusts the biostatic regulation stage accordingly. In this way, on the one hand, too small a dosage of the biostatic agent can be prevented and, on the other hand, an overdosing of the biostatic agent can be prevented.

The detection of the degree of bacterial contamination according to the present invention can be carried out in two ways. The energy storage of adrenaline triphosphate in living cells can be measured by ATP measurement (using 60 fireflies as reagents). A biofilm monitor with transparent or opaque elements can also be used to record the growth of biomass. The specific configuration of the detection mode can be selected according to actual requirements.

The biological reaction treatment step adopts a biological filtration system, and removes 80 to 90 percent of biodegradable total organic carbon TOC in raw water through the reaction of microorganisms, and can physically remove solid fine particulate matters.

If the quality of the incoming water is poor, the incoming water can be subjected to flocculation precipitation treatment before the biological reaction treatment step, and the backwashing wastewater in the biological reaction step can be introduced into the flocculation precipitation treatment step.

Basically, the membrane filtration system of the final treatment stage can be set to achieve the desired purity of the effluent, while all non-permeable material is retained at the inlet surface of the membrane. The separated material consists of inorganic and organic substances. The toxic effects of biological inhibitors prevent the metabolic formation of mucosal membranes by partially Absorbable Organic Substances (AOCs). Thus, the risk of membrane clogging due to biofilm (biofilm contamination) is reduced to a large extent.

It is better to add an adsorption stage after the bioreaction treatment step.

The design innovation points of the invention are as follows:

the invention adopts non-aeration aerobic biological treatment to remove nutrient elements in the sewage entering the membrane treatment system from the source, and then adopts low-cost biological inhibitor to inhibit the growth of microorganisms, so that the microorganisms can not generate biological polluted mucus during dormancy, thereby comprehensively and effectively solving the membrane biological pollution. The invention cancels the conventional oxidizing bactericide, adopts a special non-aeration aerobic biofilter to replace the conventional filter, creates an ideal environment suitable for the life of bacteria in the non-aeration aerobic biofilter, and removes biodegradable organic matters and entraps suspended matters to the maximum extent through microorganisms.

By optimizing the technological parameters, the microorganisms are mainly retained in the non-aeration aerobic biological filter, and only a small amount of microorganisms enter the subsequent treatment unit.

The invention changes the general technical idea of killing bacteria at present, does not need to kill the bacteria, does not resist the bacteria, is natural, and only does not allow the bacteria to grow in a membrane treatment system. Thereby really solving the membrane biological pollution. Meanwhile, the consumption of the biological inhibitor is small, the biological inhibitor is not used in the whole production period, and the economic benefit is obvious.

The invention adds a small amount of more economic biological inhibitor to replace DBNPA bactericide before reverse osmosis, mainly has the function of inhibiting the growth of a small amount of microorganisms to enable the microorganisms to enter a dormant state instead of sterilization, and solves the problem of membrane biological pollution caused by drug resistance and drug resistance of the microorganisms

"membrane fouling" is a major obstacle that prevents the widespread use of reverse osmosis technology. The object of the present invention is based on the above idea, namely to reduce the biological pollution of membrane treatment equipment and to achieve economical and efficient preparation of high purity reclaimed water/drinking water/pure water/ultrapure water.

The invention has the beneficial effects that:

the pretreatment process and the pretreatment system for solving the biological pollution of the water treatment membrane are suitable for pretreatment of various membrane treatment systems of any raw water, including heavily polluted surface water. Seawater and reclaimed water can also be treated. By selecting different membrane filtration systems, water of any purity can be produced, including normal/potable/pure/ultrapure water as required by the pharmaceutical industry. The invention can reduce the membrane biological pollution of the subsequent membrane treatment process, reduce the cleaning times of the membrane and prolong the service life of the membrane.

Drawings

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

FIG. 1 is a process flow diagram of the present invention.

FIG. 2 flow sheet of comparative example 2 (prior art)

Fig. 3 is a graph showing the effect of comparing the embodiment of the present invention with the prior art.

In the figure, a box 1 represents a flocculation precipitation treatment step, a box 2 represents a pre-oxygenation treatment step, a box 3 represents a biological inhibition environment conditioning step, a box 4 represents an activated carbon adsorption treatment step, a box 5 represents a biological inhibition environment conditioning step, a box 6 represents a biofilm detection step, a box 7 represents a chlorination bactericide adding step, a box 8 represents a multi-medium filtration treatment step, and a box 9 represents a SMBS chlorine bactericide adding and removing step.

Detailed Description

Example 1

As shown in fig. 1, the present embodiment provides a pretreatment process capable of solving biological contamination of a water treatment membrane, thereby comprising the following steps: flocculation precipitation treatment, pre-oxygenation treatment, biological inhibition environment conditioning, activated carbon adsorption treatment, biological inhibition environment conditioning and biomembrane detection.

In this embodiment, the flocculation precipitation treatment step and the activated carbon adsorption treatment step may be added or cancelled according to the requirements of the inlet water quality and the outlet water quality.

The core processing steps of the embodiment are a biological reaction processing step and a biological inhibition environment conditioning step.

The biological reaction treatment step is to establish a positive active biological community in the bioreactor. Temperature of the reactor: the temperature is more than or equal to 8 ℃, and the pH value of the reactor is as follows: 6-9, the population of microorganisms comprising: bacteria, fungi, protozoa, metazoans, mainly bacteria.

Function of the biological reaction treatment step: the proper pH value and temperature can create an environment suitable for the growth of bacteria in the bioreactor, establish a positive active biological community and breed various microbial communities, and by the method, 80 to 90 percent of biodegradable total organic carbon TOC in raw water can be removed, so that the content of the residual total organic carbon TOC meets the index of drinking water. For bacteria, the bacteria grow comfortably, so that the bacteria are not willing to grow in a membrane removing system (the living environment of a membrane system is severe).

And a step of conditioning the biological inhibition environment, which is to add a non-oxidative biological inhibitor into the pretreated water. Non-oxidative biostatic agents are heavy metal inorganic compounds that are toxic to microorganisms. The heavy metal inorganic compound selected in this example was copper sulfate. The addition amount of the copper sulfate is as follows: 0.02 mg/L.

The biological reaction treatment step also comprises a pre-oxygenation step before. The pre-oxygenation has the functions of: sufficient oxygen is beneficial to create an environment in the bioreactor suitable for bacterial growth, and to establish an active biocenosis which allows bacteria to grow comfortably and makes them unwilling to grow in a membrane removal system (the living environment of the membrane system is harsh).

The biological reaction treatment step adopts a biological filtration system to physically remove solid fine particulate matters. Meanwhile, the method comprises the step of performing flocculation precipitation treatment on the incoming water before the biological reaction treatment step, wherein the backwashing wastewater of the biological reaction treatment step can be introduced into the flocculation precipitation treatment stage.

The method is characterized in that an active carbon adsorption treatment step is further included before the biological inhibition environment conditioning step, the active carbon adsorption is an optional device, the actual relationship with the prevention of the biological membrane is not large, the requirement of water indexes is mainly considered, and the active carbon can remove substances and organic matters which generate odor in water, such as phenol, benzene, chlorine, pesticides, detergents, trihalomethane and the like. In addition, the material also has adsorption capacity to ions such as silver, cadmium, chromate, cyanogen, antimony, arsenic, bismuth, tin, mercury, lead, nickel and the like.

The biological inhibition environment conditioning step also comprises a biological membrane detection step which is used for detecting the pressure of the membrane and judging the biological pollution degree of the membrane through the membrane pressure. A biological inhibitor adding system is arranged before entering a membrane system as a safeguard measure, so even if a small amount of bacteria escaping from the bioreactor due to various reasons such as misoperation exist, the bacteria can be removed by the biological inhibitor and can not enter the membrane system. Thereby really solving the membrane biological pollution.

Comparative example 2

As shown in fig. 2, comparative example 2 is a pretreatment process of a membrane treatment process commonly used at home and abroad, and thus includes the following steps: flocculation precipitation treatment, adding of a chlorine bactericide, multi-medium filtration, activated carbon adsorption treatment and bactericide removal.

If the influent water is dechlorinated, then sterilization leaks can develop in subsequent treatment stages, which can lead to significant microbial growth in the final treatment stage. Since chlorine acts as an oxidizing disinfectant to lyse the cellular structure of the microorganisms by chemical oxidation, the oxidatively lysed biomass will become an organic matrix for the biological metabolic processes in the subsequent sterilization leak.

The invention finds the risk in practice and avoids the risk by no longer adding chlorine-containing disinfectants, newly arranging bioreactors and using biological inhibitors to have toxic effects on microorganisms. The invention creates the best living condition for the bacteria in the bioreactor, so that the bacteria can be precipitated in the bioreactor instead of reverse osmosis, and nutrients are removed in the bioreactor although the bacteria are not removed. The Biodegradable Organic Matter (BOM) of the reverse osmosis feed water is removed to the maximum extent to avoid bacterial growth and sedimentation on the reverse osmosis membrane. The membrane filtration system cleaning cycle time interval is much longer due to the reduced biofilm formation. This means that expensive chemicals used in production and shut-down are saved, so the process improves the economics of the process.

Fig. 3 is a comparative effect diagram of the embodiment of the invention and the prior art, and the diagram shows the difference change of the water replenishing/concentrated water pressure in the embodiment of the invention and the prior art. After the prior art is changed into the embodiment of the invention, no obvious pressure increase exists. The first wash was performed about 12 months after the inventive examples were performed. RO was washed 17 times a year using the prior art and 1 time a year after the operation of the inventive examples.

It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art should understand that they can make various changes, modifications, additions and substitutions within the spirit and scope of the present invention.

Claims

1. A pretreatment process for solving the biological pollution of a water treatment membrane is characterized by comprising the following steps: a biological reaction treatment step and a biological inhibition environment conditioning step.

2. A pretreatment process for addressing water treatment membrane biological contamination as recited in claim 1, wherein the biological reaction treatment step is to establish a population of actively living organisms in the bioreactor;

temperature of the reactor: the temperature is more than or equal to 8 ℃, and the pH value of the reactor is as follows: 6-9.

3. The pretreatment process for addressing biological contamination of water treatment membranes as recited in claim 1, wherein the biostatic environmental conditioning step comprises adding a non-oxidative biostatic agent to the pretreated water.

4. A pretreatment process for addressing bio-fouling of water treatment membranes as recited in claim 3, wherein the non-oxidative bio-inhibitor is a heavy metal inorganic compound toxic to microorganisms.

5. The pretreatment process for addressing biological contamination of water treatment membranes as recited in claim 4, wherein the heavy metal inorganic compound is copper sulfate or copper chloride.

6. A pretreatment process for addressing water treatment membrane biofouling according to claim 1, wherein said bioreaction treatment step further comprises a pre-oxygenation step.

7. A pretreatment process for addressing water treatment membrane biological contamination as recited in claim 1, wherein the bioreaction treatment step employs a biological filtration system.

8. A pretreatment process for addressing water treatment membrane biological contamination as recited in claim 1, further comprising subjecting the incoming water to flocculation and precipitation treatment before the biological reaction treatment step, wherein backwash wastewater of the biological reaction treatment step may be introduced into the flocculation and precipitation treatment stage.

9. A pretreatment process for addressing water treatment membrane biofouling according to claim 1, further comprising an activated carbon adsorption treatment step prior to the biostatic environmental conditioning step.

10. A pretreatment process for addressing water treatment membrane biofouling according to claim 1, further comprising a biofilm detection step after the biostatic environmental conditioning step.