Method for intensively removing new pollutants and converted products thereof by functional partition of biological activated carbon

Abstract

The invention relates to a method for intensively removing new pollutants and converted products thereof by functional division of biological activated carbon, belonging to the field of water treatment. Aiming at the problems that an existing ozone-biological activated carbon process is low in ozone utilization rate and poor in removal effect of refractory pollutants, efficient catalytic activated carbon and common biological activated carbon are filled in a partitioned mode, and functional partitioning of catalytic oxidation, adsorption and biodegradation is achieved. The residual ozone is converted into hydroxyl free radicals in an efficient catalysis area through heterogeneous catalysis, and oxidative degradation of pesticide and other refractory new pollutants is achieved; and deeply removing pollutants and converted products thereof in the enhanced removal area by utilizing the synergistic effect of adsorption and microbial degradation. Under the preferable conditions that the proportion of the efficient catalytic zone is 5%-30% and the like, the removal efficiency of refractory pollutants is remarkably improved, and the removal rate can reach 90%-100%. The method provided by the invention is suitable for the transformation and upgrading of the existing ozone-biological activated carbon process of the water plant, and can also be used for the enhanced removal of new pollutants in sewage treatment.

Description

A method for enhancing the removal of new pollutants and their transformation products by functional zoning of bio-activated carbon Technical Field

[0001] (I) Technical Field

[0002] This invention relates to a method for removing recalcitrant new pollutants using a bio-activated carbon functional zoning enhancement ozone-bio-activated carbon process, belonging to the field of water treatment. Background Technology

[0003] (II) Background Technology

[0004] In recent years, new pollutants such as pesticides, antibiotics, endocrine disruptors, pharmaceuticals, and personal care products have been widely detected in environmental water bodies, threatening water quality safety. These new pollutants typically exhibit environmental persistence, endocrine disruption effects, and cellular and genotoxicity; even trace levels can pose risks to ecological and environmental safety and human health with long-term exposure. Therefore, efficient removal of new pollutants from water is a key requirement for improving water quality safety and protecting the environment and public health. Existing conventional drinking water treatment processes such as coagulation-sedimentation have limited removal capabilities for new pollutants. While the ozone-biological activated carbon process, as the most widely used advanced treatment technology, can improve removal efficiency through the synergistic effect of ozone oxidation and the adsorption and degradation by biological activated carbon, it still faces significant technical bottlenecks: First, ozone oxidation is selective, exhibiting low removal efficiency for structurally stable and recalcitrant pollutants such as pesticides, and these new pollutants have poor biodegradability. Second, under conventional water treatment conditions, the rate and yield of hydroxyl radicals generated by ozone self-decomposition are slow, making it difficult to achieve deep oxidative decomposition of recalcitrant new pollutants.

[0005] Of particular note is that, in actual water plant operation, the ozone dosage is typically 0.4–0.6 mg / L, of which 30%–50% is not effectively utilized and enters the biological activated carbon filter as residual ozone. This not only wastes ozone but also inhibits the activity of microorganisms on the activated carbon surface, leading to a dual technical contradiction of "inefficient use of ozone oxidant" and "inhibited biodegradation," further weakening the overall efficiency of the ozone-biological activated carbon process. Currently, the drinking water treatment industry lacks an integrated solution that can simultaneously achieve efficient conversion of residual ozone and enhanced removal of recalcitrant pollutants. Therefore, developing an innovative strategy that can achieve catalytic conversion of residual ozone in the biological activated carbon unit while simultaneously enhancing the removal of new recalcitrant pollutants has become an urgent need to overcome existing process bottlenecks and improve the efficiency of new pollutant removal. Summary of the Invention

[0006] (III) Summary of the Invention

[0007] To address the shortcomings of existing ozone-bioactivated carbon processes, such as low ozone utilization efficiency and insufficient removal effectiveness for recalcitrant new pollutants, this invention provides a synergistic method for ozone-bioactivated carbon based on functional partitioning. This method, through the preparation of highly efficient catalytic activated carbon and its functional partitioning, can achieve enhanced removal of recalcitrant new pollutants such as acetochlor, isoprothiolane, and atrazine.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] 1. Preparation of Highly Efficient Catalytic Activated Carbon

[0010] This invention uses commercially available activated carbon as a carrier and employs a co-precipitation method to load iron-based active components. Specifically, a certain mass of activated carbon is placed in an ammonium bicarbonate solution and fully impregnated. Then, under continuous stirring, a ferric nitrate nonahydrate solution is slowly added dropwise. During the addition process, the pH of the mixture is maintained at 7.0 ± 0.2. After the addition is complete, the mixture is shaken and reacted at room temperature for 2 hours. Subsequently, solid-liquid separation is performed, and the resulting solid is dried in an oven, then gently washed with deionized water to remove impurities, and finally dried again to obtain the highly efficient catalytic activated carbon.

[0011] 2. Construction of Functional Zoning Reactors

[0012] The highly efficient catalytic activated carbon obtained in step one and the unmodified ordinary biological activated carbon are packed in separate zones to construct a biological activated carbon functional zone treatment unit. The specific packing method is as follows: starting from the top of the support layer, the highly efficient catalytic activated carbon layer and the ordinary biological activated carbon layer are packed sequentially from bottom to top (or from top to bottom, depending on the operating mode of the biological activated carbon) to form a highly efficient catalytic zone and an enhanced removal zone, respectively.

[0013] 3. Coordinated operation with ozone units

[0014] The effluent from the ozone contact unit is introduced into the functional zone treatment unit, flowing sequentially through the high-efficiency catalytic zone and the enhanced removal zone. In the high-efficiency catalytic zone, residual ozone is catalytically decomposed by iron-based activated carbon, generating hydroxyl radicals in situ, achieving efficient oxidation of recalcitrant pollutants. In the enhanced removal zone, new pollutants and their transformation products are further removed through the adsorption of activated carbon and the biodegradation by attached microorganisms, thereby achieving targeted and enhanced removal of target recalcitrant new pollutants.

[0015] The principle of this invention lies in the functional zoning design of the activated carbon filter, constructing a high-efficiency catalytic zone and an enhanced removal zone to achieve deep utilization of residual ozone and enhanced removal of pollutants. First, in the high-efficiency catalytic zone, the catalytic components loaded on the activated carbon and residual ozone form a heterogeneous catalytic ozone oxidation system, promoting its conversion into highly reactive oxides such as hydroxyl radicals, significantly improving ozone utilization efficiency, thereby achieving efficient oxidative decomposition of recalcitrant pollutants such as acetochlor and atrazine. Subsequently, in the enhanced removal zone, smaller molecule intermediates with higher biodegradability generated through advanced oxidation, as well as other residual pollutants in the water, are further synergistically removed through adsorption by activated carbon and microbial degradation by the surface biofilm.

[0016] During the experiments, the inventors discovered that, under a certain residual ozone concentration, there exists an optimal volume ratio between the high-efficiency catalytic zone and the enhanced removal zone. Within this range, the two zones function synergistically, resulting in the highest overall removal efficiency for new pollutants. If the proportion of the high-efficiency catalytic zone is too high, its catalytic conversion efficiency for ozone does not significantly improve; instead, the reduced volume of the enhanced removal zone leads to insufficient biodegradation capacity, causing a decrease in overall removal efficiency. Therefore, the volume ratio of the high-efficiency catalytic zone is a key parameter affecting the overall system efficiency.

[0017] According to the present invention, the preferred embodiments are as follows:

[0018] 1. The high-efficiency catalytic zone accounts for 5%–30% of the volume of the bio-activated carbon functional unit.

[0019] 2. The empty bed contact time of the bio-activated carbon functional zone unit is 5–30 minutes.

[0020] 3. The residual ozone concentration in the influent entering the biological activated carbon functional zone unit is 0.05–0.70 mg / L.

[0021] 4. The target recalcitrant new pollutants include, but are not limited to, acetochlor, isoprothiolane, and atrazine.

[0022] 5. The activated carbon used to prepare high-efficiency catalytic activated carbon is a commercially available product, preferably with a specification of 8×30 mesh.

[0023] The technical advantages of this invention are as follows: The provided bio-activated carbon functional zoning method, through the synergistic enhancement of "catalytic oxidation + biodegradation," achieves efficient utilization of residual ozone and targeted removal of recalcitrant pollutants, ultimately significantly improving the overall removal efficiency of the ozone-bio-activated carbon process for recalcitrant new pollutants. This method is simple to operate and is not only applicable to the high-efficiency catalytic activated carbon described in this invention, but can also be combined with other types of catalytically modified activated carbon, demonstrating strong versatility.

[0024] By applying the method of this invention, the ozone dosage can be reduced by about 50% while ensuring the same pollutant removal effect. This effectively solves the technical bottleneck of low ozone utilization and high operating cost in the existing ozone-biological activated carbon process, and realizes cost reduction and efficiency improvement of the process. It has important engineering application prospects and environmental significance. Attached Figure Description

[0025] (iv) Description of the attached drawings

[0026] Figure 1. Enhanced removal effect of ozone-functional zoned bio-activated carbon on acetochlor (500 ng / L).

[0027] Figure 2. Enhanced removal effect of ozone-functional zoned bio-activated carbon on isoprothiolane (500 ng / L).

[0028] Figure 3. Enhanced removal effect of ozone-functional zoned bio-activated carbon on atrazine (500 ng / L).

[0029] Figure 4. Enhanced removal efficiency of ozone-functional zoned bio-activated carbon pilot system for acetochlor, isoprothiolane, and atrazine (500 ng / L). Detailed Implementation

[0030] (V) Detailed Implementation Methods

[0031] Example

[0032] To verify the effectiveness of this invention, the following comparative experiment was conducted: Commercially available activated carbon (8×30 mesh) was used as a carrier, and high-efficiency catalytic activated carbon was prepared by co-precipitation of ammonium bicarbonate and ferric nitrate nonahydrate. This catalytic activated carbon and ordinary biological activated carbon with a carbon age of 2 years from a waterworks were packed in separate sections. The biological activated carbon operated in an upward flow mode, with the high-efficiency catalytic zone located at the bottom and accounting for 20% of the volume, and the upper part being the enhanced removal zone. Effluent from the waterworks sedimentation tank was used as the influent, and acetochlor, isoprothiolane, and atrazine were added at initial concentrations of 500 ng / L as target recalcitrant pollutants. The ozone unit was pre-treated at a dosage of 0.6 mg / L, resulting in a residual ozone concentration of approximately 0.2 mg / L in the effluent. The effluent then entered the functional zone biological activated carbon filter column, with an empty bed contact time of 5 minutes. A filter column filled only with ordinary biological activated carbon of the same carbon age was set up as a control, and the process was repeated for one month. The results showed that the functional zone biological filter column can effectively catalyze the conversion of residual ozone, achieving targeted and enhanced removal of recalcitrant new pollutants. The removal rates of acetochlor (Figure 1), isoprothiolane (Figure 2), and atrazine (Figure 3) were 92%, 95%, and 93%, respectively, which were significantly improved compared with the control group, confirming the effectiveness and superiority of the present invention.

[0033] Application Examples

[0034] To examine the applicability of this invention in practical applications, a 10 m³ / d pilot-scale test was conducted: High-efficiency catalytic activated carbon was prepared using the same method and compared with ordinary biological activated carbon from a waterworks with a carbon age of 13 years in separate compartments (the catalytic zone accounted for 20%). Using sand-filtered effluent from the waterworks as the influent, acetochlor, isoprothiolane, and atrazine were added at an initial concentration of 500 ng / L as target pollutants. The preceding ozone unit dosage was 0.3–0.5 mg / L, with a contact time of 15 minutes, resulting in a residual ozone concentration of 0.2–0.3 mg / L in the effluent. Subsequently, the effluent entered the functional zone biological activated carbon filter column, with an empty bed contact time of 15 minutes. The system operated continuously for two months, treating 10 m³ / d. The concentrations of the three pollutants in the influent and effluent were monitored, and their removal rates were calculated. The results showed that the functional zone biological activated carbon process could effectively improve the removal efficiency of acetochlor, isoprothiolane and atrazine (Figure 4). Compared with ozone effluent, the removal rate of the three recalcitrant pollutants was nearly 100%.

[0035] The present invention has been described in detail above with reference to specific embodiments and application examples. These descriptions are intended to enable those skilled in the art to better understand and implement the present invention, and are not intended to limit the present invention. Any simple improvements or modifications made by those skilled in the art based on the principles of the present invention are within the scope of protection of the present invention. Unless otherwise stated, the reagents, materials, methods, and equipment used in the present invention are all conventional commercially available products or standard technical means in the art.

Claims

1. A method for enhancing the removal of new pollutants using an ozone-biological activated carbon process based on functional zoning, characterized in that, The method includes the following steps: (1) Constructing a functional zone biological activated carbon treatment unit: including a high-efficiency catalytic zone and an enhanced removal zone; the high-efficiency catalytic zone is filled with high-efficiency catalytic activated carbon and is used for catalytic conversion of residual ozone; the enhanced removal zone is filled with ordinary biological activated carbon and is used for adsorption and biodegradation of pollutants and their conversion products. (2) Process coupling and operation: the effluent from the pre-treatment unit containing residual ozone is introduced into the functional zone treatment unit; the water flows sequentially through the high-efficiency catalytic zone and the enhanced removal zone to achieve efficient utilization of residual ozone and graded enhanced removal of new pollutants.

2. The method according to claim 1, characterized in that, The high-efficiency catalytic zone accounts for 5%–30% of the volume of the functional zone processing unit.

3. The method according to claim 1, characterized in that, The empty bed contact time of the functional partition processing unit is 5–30 minutes.

4. The method according to claim 1, characterized in that, The residual ozone concentration in the influent is 0.05–0.70 mg / L.

5. The method according to claim 1, characterized in that, The new pollutant is a recalcitrant pollutant, including but not limited to one or more of acetochlor, isoprothiolane, and atrazine.

6. The method according to claim 1, characterized in that, The highly efficient catalytic activated carbon is prepared by the following method: immersing the activated carbon carrier in an ammonium bicarbonate solution, slowly adding ferric nitrate nonahydrate solution under stirring conditions, and controlling the pH of the reaction system at 7.0 ± 0.2 to carry out a co-precipitation reaction; after the reaction is completed, the catalytic activated carbon is obtained by solid-liquid separation, drying and washing.

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