Introduction
With the deepening reform of socio-economic structure, the aquaculture industry has been developing rapidly. However, during this process, the issue of wastewater pollution from aquaculture has attracted widespread attention from all sectors of society. Therefore, the harm of aquaculture wastewater to aquatic products and the environment, as well as the relevant treatment technologies, are of great significance.
Currently, pond-based high-density aquaculture is the most common method. This model produces a large amount of excreta and leftover feed, leading to serious pollution of the aquaculture water. This issue has become one of the main contradictions between socio-economic development and ecological environmental protection.
If the polluted water cannot be treated promptly, it will directly impact production output and the quality of aquatic products, and will also severely damage the aquaculture environment. Therefore, the hazards of aquaculture wastewater pollution and the corresponding treatment technologies require our high attention. It is essential to improve the technical level of wastewater treatment, enhance the quality of aquatic products, and reduce the impact on the external environment, thereby providing reliable support for the coordinated development of China's economy and ecology.
Hazards of Aquaculture Wastewater Pollution
1.Harm to Aquatic Products
Backward aquaculture techniques are currently a prominent problem in China's aquaculture industry. Some farmers, in pursuit of maximum economic benefits, neglect wastewater treatment during the production process. Over time, this results in the accumulation of a large amount of pollutants, severely damaging the aquaculture environment. This not only destroys the local ecosystem but also threatens human health.
In order to reduce costs, many farmers blindly feed large quantities of low-quality feed and abuse various additives such as stabilizers, disinfectants, and antibiotics. These practices seriously harm the living conditions of aquatic organisms. Moreover, a large number of harmful substances dissolve into the water, causing severe water pollution.
Additionally, some farmers use highly toxic drugs for the convenience of daily management. These drugs often contain heavy metals. Once these heavy metals are absorbed by aquatic organisms and then consumed by humans, they gradually accumulate in the human body, potentially causing chronic damage-or even acute heavy metal poisoning in severe cases.
According to studies by experts, common heavy metals that accumulate in aquatic organisms include lead and mercury. Once these elements enter the human body, they can cause unexpected consequences, which is a serious issue that deserves close attention.
2.Harm to the Environment
In aquaculture, intensive farming is most common. High-density farming leads to a significant accumulation of metabolic waste in the water, increasing the levels of nitrogen and phosphorus. This promotes the growth of organic matter in the water and raises the concentration of organic pollutants.
Such pollution needs to be thoroughly treated; otherwise, the excess organic matter will consume the dissolved oxygen in the water. Additionally, the increase of ammonia nitrogen and nitrite supports the growth of harmful bacteria and plankton, leading to eutrophication and water quality degradation.
When such polluted water is discharged into the surrounding natural environment, it causes serious ecological damage.
Aquaculture Wastewater Treatment Technologies
1.Physical Treatment Technology
In aquaculture wastewater treatment, physical technologies aim to remove suspended solids from the wastewater, thereby reducing the biochemical oxygen demand (BOD) as much as possible. Common physical treatment methods include filtration and foam separation. The most notable advantages of these methods are their low cost and ease of operation. However, physical methods are generally ineffective in removing ammonia nitrogen from the water.
Foam separation involves the formation of tiny air bubbles in water through aeration. Surface-active substances in the water adhere to these bubbles and rise to the surface, forming a foam layer. Simply removing this foam can achieve a certain degree of water purification. Experts have developed an improved foam separation column, which features a cross-structured design that facilitates foam rise while preventing foam retention. The bubble size can be adjusted as needed to optimize the separation effect.
Filtration involves passing wastewater through a filter to remove suspended particles. This method is effective in eliminating dissolved heavy metal pollutants, depending on the filter material used.
Chemical Treatment Technology
Chemical treatment methods for aquaculture wastewater primarily include oxidation and electrochemical processes. These methods can achieve high levels of pollutant removal. However, proper control over the type and dosage of chemicals is critical to avoid secondary pollution.
- Oxidation uses oxidizing agents like ozone or hydrogen peroxide to break down organic pollutants in the water. These oxidizers have strong oxidative properties, making them highly effective in purifying contaminated water.
- Electrochemical treatment involves applying an electric current to the wastewater, which can decompose pollutants such as ammonia nitrogen and nitrite, thus achieving effective purification.
Biological Treatment Technology
1.Activated Sludge Process
The activated sludge method involves aerating the wastewater to promote the survival and proliferation of aerobic microorganisms in the polluted water. These microorganisms grow and form sludge-like flocs that possess strong oxidative and adsorptive capacities, enabling efficient removal of pollutants.
Studies by experts have shown that adding sulfate and zero-valent iron (ZVI) can significantly improve the dewatering performance of the activated sludge. The effective dosage range is 0–30 g/L for ZVI and 0–6 g/L for ammonium persulfate. When these substances are mixed and adjusted to a neutral pH, the performance of the activated sludge process can be maximized.
2.Biofilm Technology
Biofilm technology involves placing bio-carriers (fillers) into a biological filter. Microorganisms adhere to the surface of these carriers and form biofilms. These biofilms are responsible for degrading organic pollutants in the wastewater.
Research shows that placing the biofilm reactor in water for just 47 minutes can result in the removal of up to 90% of pollutants, including ammonia nitrogen. After use, the carriers can be recovered and reused, making biofilm technology a sustainable and environmentally friendly solution.
3.Ecological Treatment Method
The ecological treatment method involves the rational configuration of artificial wetlands and ecological floating beds. Plants in these systems absorb organic pollutants from the water.
Experts have also conducted studies on this method. For instance, during a barley seed germination experiment, it was found that disinfectants such as ethanol and bleach significantly reduced the germination rate of the seeds. However, the use of barley plants to treat aquaculture wastewater has shown good purification results, indicating the potential of ecological methods in wastewater treatment.
In today's era of rapid socioeconomic development, people's quality of life has significantly improved. The aquaculture industry not only contributes to the continuous growth of the economy but also better meets the increasingly diverse needs of the population. As such, the development outlook for aquaculture is promising.
Conclusion
However, we must pay close attention to the water pollution risks currently present in aquaculture. Traditional aquaculture methods have caused considerable pollution to the water bodies used for farming, which runs counter to China's long-standing goal of building an environmentally friendly and resource-saving society.
Therefore, it is crucial to take the issue of water pollution in aquaculture seriously and continuously enhance water treatment technologies. By introducing and applying more advanced and innovative treatment methods, we can promote the sustainable and eco-friendly development of the aquaculture industry in China and ultimately maximize its socioeconomic benefits.