Research on Enhanced Organic Matter Treatment Technology in Drinking Water Plants Based on Micro-nano Bubble Ozone Aeration

Research on Enhanced Organic Matter Treatment Technology in Drinking Water Plants Based on Micro-nano Bubble Ozone Aeration

In the field of drinking water treatment, enhancing the removal rate of organic matter is crucial for ensuring water quality safety. The research on the enhanced treatment of organic matter in drinking water plants based on micro-nano bubble ozone aeration has emerged. This study explores effective ways to improve the removal effect of organic matter in the processes of raw water coagulation and ozone treatment in drinking water plants by comparing different aeration methods, providing new ideas and approaches for drinking water treatment.

With the continuous improvement of people's requirements for drinking water quality, the treatment processes of drinking water plants are facing higher challenges. The removal rate of organic matter in important process sections such as raw water coagulation and pre-/post-ozone treatment directly affects the quality of drinking water. Traditional aeration methods have certain limitations in terms of ozone mass transfer efficiency and organic matter removal effect. Therefore, conducting research on micro-nano bubble ozone aeration has significant practical significance.

During the process of drinking water treatment, the presence of organic matter not only affects the taste and odor of water but also poses potential threats to human health. Therefore, enhancing the removal rate of organic matter is one of the important tasks for drinking water plants. Micro-nano bubbles possess unique physical and chemical properties, such as a large specific surface area and a long residence time, which give them potential advantages in ozone mass transfer and organic matter removal.

The micro-nanobubbles generated by the micro-nanobubble generator possess unique characteristics. In the research, the microbubble generator produced 1.2×108 nanobubbles/mL, with a median particle size significantly below 100 μm. These small-sized nanobubbles facilitate the prolonged retention of MNBs ozone (MNBs - O3) in water. Due to their large specific surface area, micro-nanobubbles can increase the contact area between ozone and water, thereby enhancing the mass transfer efficiency of ozone. In water, micro-nanobubbles can also adsorb hydrophobic organic substances and generate hydroxyl radicals, which play a crucial role in improving the removal effect of organic substances.

The characteristics of micro-nano bubbles make them have broad application prospects in drinking water treatment. Compared with the bubbles produced by ordinary aeration discs, micro-nano bubbles can more effectively transfer ozone into water, increasing the solubility and utilization rate of ozone in water. Meanwhile, the adsorption and oxidation effects of micro-nano bubbles can directly act on organic matter, causing it to decompose and be removed. In practical applications, the performance of the micro-nano bubble generator and the characteristics of the produced bubbles are crucial to the treatment effect. Therefore, in-depth research on the characteristics and generation mechanism of micro-nano bubbles is of great significance for optimizing the micro-nano bubble ozone aeration technology.

To study the effect of micro-nano bubbles (MNBs) on the coagulation of raw water in water plants, a small-scale experiment was conducted. The results showed that when 12.5% (by volume) of MNBs water was added to the raw water of the water plant, the characteristics of MNBs in adsorbing hydrophobic organic matter and generating hydroxyl radicals could significantly improve the coagulation and sedimentation effect. Coagulation and sedimentation is an important process in drinking water treatment, and its effect directly affects the operation of subsequent treatment processes and water quality. The addition of micro-nano bubbles can make organic matter in water better coagulate and sediment, thereby increasing the removal rate of organic matter. In the experiment, the decrease in UV254 reached 15%, indicating that the addition of micro-nano bubbles has a significant promoting effect on the removal of organic matter.

The influence of micro-nano bubbles on the coagulation effect is mainly reflected in two aspects. On the one hand, micro-nano bubbles can adsorb hydrophobic organic matter, making it easier to combine with coagulants and form larger flocs, thereby improving the sedimentation effect. On the other hand, the hydroxyl radicals produced by micro-nano bubbles have strong oxidizing properties, which can decompose organic matter, reduce the molecular weight of organic matter, and make it easier to be removed. In practical applications, the coagulation effect can be further optimized and the quality of drinking water can be improved by adjusting the addition amount of micro-nano bubbles and coagulants.

During the pre-ozone treatment process, after the raw water was treated by MNBs - O3, the composition of organic matter in the effluent changed significantly. The peak at 110 kDa disappeared and a new peak appeared in the fraction less than 1 Da, indicating that MNBs - O3 treatment could alter the molecular weight distribution of organic matter. The removal rate of five-day biochemical oxygen demand (BOD5) was approximately 15%, which was much lower than the 50% achieved by the conventional diffuser. Meanwhile, total organic carbon and UV254 did not change significantly. This might be due to the different mechanisms of action between MNBs - O3 and the conventional diffuser. MNBs - O3 mainly treats organic matter through oxidation and adsorption, rather than through biological degradation as the conventional diffuser does.

Pre-ozone treatment is an important step in drinking water treatment, with the main purpose of removing some organic matter and algae from the water, as well as improving the taste and odor of the water. The application effect of micro-nano bubble ozone aeration technology in pre-ozone treatment shows that it can affect the structure and properties of organic matter, but it may not be as effective as the conventional diffuser in removing BOD5. However, the advantages of micro-nano bubble ozone aeration technology in other aspects, such as improving ozone mass transfer efficiency and adsorbing hydrophobic organic matter, make it still have significant application value in drinking water treatment. In practical applications, the aeration method can be reasonably selected based on the characteristics of the raw water and treatment requirements to achieve the best treatment effect.

In the post-ozone treatment process, the BOD5 increased by 40% after MNBs - O3 treatment. This result is different from that in the pre-ozone treatment process. In the post-ozone treatment stage, the micro-nano bubble ozone aeration may further promote the decomposition and transformation of organic matter in water, making it more biodegradable and thus leading to an increase in BOD5. The main purpose of post-ozone treatment is to further remove organic matter and disinfect water. The application of micro-nano bubble ozone aeration technology can enhance the oxidation capacity of ozone and improve the removal effect of organic matter. Although BOD5 increases, this does not mean that water quality deteriorates; rather, it indicates that the structure of organic matter in water has changed, making it more conducive to subsequent biological treatment.

Post-ozone treatment is the last line of defense in drinking water treatment, and its treatment effect directly affects the final quality of drinking water. The application of micro-nano bubble ozone aeration technology in post-ozone treatment not only increases the removal rate of organic matter but also reduces the amount of disinfectant used and lowers the generation of disinfection by-products. By reasonably adjusting the parameters of micro-nano bubble ozone aeration, such as ozone dosage and aeration time, the post-ozone treatment effect can be further optimized to ensure the safety and hygiene of drinking water. In practical applications, it is also necessary to combine other treatment processes, such as biological treatment and filtration, to achieve comprehensive purification of drinking water.

Through this research, we have drawn a series of important conclusions. Micro-nano bubbles possess unique characteristics that can enhance the mass transfer efficiency of ozone and the removal effect of organic matter. During the coagulation process, micro-nano bubbles can significantly improve the coagulation sedimentation effect and reduce UV254. In the pre-ozone treatment, MNBs - O3 treatment can change the molecular weight distribution of organic matter, but the BOD5 removal rate is relatively low. In the post-ozone treatment, MNBs - O3 treatment can promote the decomposition and transformation of organic matter, causing BOD5 to rise. These conclusions provide important reference basis for the application of micro-nano bubble ozone aeration technology in drinking water treatment.