Sewage fish caught six points
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July 18 13:16:34, 2025
Every day, a significant volume of domestic wastewater flows into urban drainage systems. This wastewater is rich in organic matter and nutrients, making it a valuable resource if used properly. In suburban areas, fish ponds often utilize this wastewater for aquaculture. This practice not only reduces the need for fertilizers, feed, and labor but also helps in purifying the water and improving the local environment.
Ponds that are used for fish farming with sewage should generally be large, ideally around 6,670 square meters. The reason is that the purification capacity of the pond is limited, so maintaining good water quality can be challenging. The depth of the pond should be between 2 to 3 meters. It's best to design the pond in an east-west orientation, with the shorter sides slightly oval-shaped to prevent stagnant "dead corners." Elliptical bends are installed on both the inlet and outlet pipes, and the bottom of the pond has a slight slope—usually about 5%. This design makes it easier to remove debris and facilitates fishing. Two or three inlet and outlet pipes are recommended, placed at opposite ends to avoid "dead angles" and ensure smooth water flow, which enhances the overall purification effect. The inlet pipe should be positioned higher than the water surface, creating a stronger flow that improves oxygenation in the pond. Additionally, water intake pipes and gates should be installed before the main inlet to regulate the timing and volume of wastewater entering the pond.
The main species raised in these ponds are scalefish, accounting for approximately 80% to 90% of the stock. Other species such as tilapia, grass carp, and others make up the remaining 10% to 20%. Stocking density typically ranges from 1,000 to 1,500 fish per 667 square meters.
Managing wastewater aquaculture requires careful control of the amount of wastewater introduced, maintaining a balanced level of nutrients in the water, and preventing harmful substances from entering the pond. Here are some key practices:
1. Understand the source, characteristics, and discharge patterns of the wastewater. Avoid using industrial wastewater that may contain toxic substances.
2. Use long open channels for the wastewater to expose it to air, allowing dissolved oxygen to increase and solids to settle. Alternate the use of inlet and outlet pipes to improve water circulation.
3. Install a sedimentation tank before the wastewater enters the pond. This helps reduce toxicity. Some units can even create a small lake-like structure, acting as a secondary treatment area for better results.
4. Control the volume of wastewater added at one time. The amount injected should not exceed 3% of the total pond capacity, and water clarity should be maintained between 20 and 35 cm.
5. Place feeding areas away from the sewage outlet to avoid fish being poisoned by concentrated waste.
6. Use aerators to speed up the breakdown of organic matter, promote plankton growth, and support fish health while preventing floating fish.
By following these practices, fish farmers can effectively manage wastewater aquaculture, ensuring sustainable production and environmental protection.