Applications of Blowers in Aquaculture and Recirculating Aquaculture Systems

Introduction

In the aquaculture industry, dissolved oxygen levels are one of the key indicators determining the success or failure of farming operations. Whether in traditional pond-based systems or in modern recirculating aquaculture systems (RAS), adequate dissolved oxygen is essential for the healthy growth and survival of aquatic organisms. And… Blower It is precisely the core equipment for achieving efficient oxygenation and water circulation.

This article provides a systematic overview of the technical principles, application scenarios, equipment selection, and development trends of blowers in aquaculture and recirculating aquaculture systems, helping industry professionals gain a deeper understanding of this critical piece of technological equipment.

I. Why can’t aquaculture do without blowers?

In aquaculture systems, dissolved oxygen in the water primarily originates from three sources: atmospheric reaeration, photosynthetic oxygenation, and mechanical aeration. Under high-density farming conditions, natural reaeration and photosynthesis are far from sufficient to meet the oxygen demands of the cultured organisms; therefore, mechanical aeration equipment is essential to maintain adequate dissolved oxygen levels in the water.

The basic principle of aeration using an air blower is as follows: the blower forces air into an air‑distribution pipeline, which then delivers it through micro‑porous diffusers or diffuser plates installed along the pond bottom, releasing it into the water in the form of tiny bubbles. As these bubbles rise from the pond floor, oxygen dissolves thoroughly into the water; at the same time, their upward movement induces water circulation and promotes vertical mixing between surface and bottom layers.

The theoretical basis of this process is the two-film theory: at the gas–water interface, a gas film and a liquid film exist, and oxygen molecules must diffuse through these two films from the gas phase into the liquid phase. Meanwhile, the numerous tiny bubbles generated by microporous aeration significantly increase the gas–liquid interfacial area, effectively overcoming the mass-transfer resistance imposed by the liquid film and thereby substantially enhancing oxygen transfer efficiency.

In practical applications, blower-based aeration technology offers the following key advantages:

High oxygenation efficiency The fine bubbles (0.5–3 mm in diameter) produced by microporous aeration tubes can increase oxygen solubility to over 70%, far surpassing that of conventional impeller-type aerators (30%–50%).

Deep aeration The blower can meet the dissolved oxygen requirements in water depths of 2 to 4 meters (at a pressure of 0.05 to 0.08 MPa), effectively addressing the longstanding issue of oxygen deficiency at the pond bottom.

Water body convection The upward motion of bubbles promotes vertical convection in the water column, transporting oxygen-rich surface water to the bottom while bringing harmful substances from the bottom to the surface for oxidative decomposition.

II. Types of Blowers and Their Application Scenarios

The blowers commonly used in aquaculture fall into the following main types, each suited to specific applications.

1. Roots blowers — the mainstream choice

Roots blowers are currently the most widely used aeration equipment in the aquaculture industry. They are positive-displacement blowers, with airflow rate proportional to rotor speed. A three-lobe Roots blower completes three suction and discharge cycles per rotor revolution, offering advantages over two-lobe models, including reduced gas pulsation, lower load fluctuations, higher mechanical strength, lower noise levels, and reduced vibration.

Roots blowers feature constant air flow, adaptive pressure, oil-free operation, a compact design, and stable performance. The discharged air is clean, free of oil and dust. In terms of power range, motor ratings span from 0.75 kW to 280 kW, with airflow rates from 0.6 m³/min to 182 m³/min and pressure levels between 9.8 and 98 kPa, enabling flexible adaptation to applications ranging from small-scale hatcheries to large commercial fish farms.

In terms of model selection, for conventional fish ponds (water depth 1–2 meters), a power rating of 3–7.5 kW and an air flow rate of 1.5–3.5 m³/min are recommended, covering an area of 3–8 mu; for high-density prawn farming, 7.5–15 kW is advised; and for deep-water sea cucumber farming (water depth 3–4 meters), 15–30 kW is required.

2. Magnetic Levitation and Air-Levitation Blowers—A New Trend in Energy Efficiency

In recent years, magnetic‑levitation and air‑bearing blowers, as next‑generation, high‑efficiency, energy‑saving equipment, have been rapidly gaining traction in the aquaculture sector.

Magnetic‑levitation blowers employ magnetic‑bearing technology to achieve contactless rotor suspension via electromagnetic forces, thereby eliminating mechanical friction losses. Compared with conventional Roots blowers, they can reduce energy consumption by approximately 40%; moreover, they require no lubrication system, thus avoiding the risk of oil contamination—making them particularly well suited for recirculating aquaculture systems with stringent water‑quality requirements.

Air‑suspension oxygenators also offer significant advantages: they consume more than 30% less energy than conventional Roots blowers, reduce noise to below 80 dB, require no maintenance, and deliver 100% oil‑free, clean air. At 55 kW, they can deliver an air flow rate of 52 m³/min with a pressure of up to 60 kPa, meeting the aeration needs of large‑scale aquaculture ponds.

Although these systems entail a relatively high initial investment, they can substantially reduce energy and maintenance costs over the long term, making them one of the core pieces of equipment in recirculating aquaculture systems.

III. Applications of Blowers in Recirculating Aquaculture Systems

Recirculating aquaculture systems (RAS) represent a key direction in the development of modern aquaculture. By treating and reusing the effluent from culture ponds, RAS offers advantages such as water conservation, environmental sustainability, and high productivity. In this system, blowers serve multiple functions.

1. Oxygenation of aquaculture ponds

In recirculating aquaculture systems, blowers supply oxygen to the rearing tanks via nano‑bubble diffusers. These diffusers are typically arranged in a circular pattern within the tank, encircling the entire perimeter to maximize the aeration surface area. An external air source, driven by a Roots blower, delivers compressed air to the nano‑bubble diffusers, generating fine bubbles that thoroughly dissolve atmospheric oxygen into the water, thereby maintaining high dissolved‑oxygen levels.

When used in conjunction with a microporous aeration tube, an air‑levitation‑based oxygenator can uniformly release tiny bubbles from the bottom of the pond, achieving an oxygen transfer efficiency (OTE) of 25% to 35%—twice that of conventional paddlewheel aerators. At the same time, the unit’s noise level can be as low as 75 decibels, significantly reducing stress responses in cultured organisms.

2. Oxygen Supply for Biofilters

The core purification unit of a recirculating aquaculture system is the biofilter, in which nitrifying bacteria require an ample supply of oxygen to break down toxic substances such as ammonia and nitrite. A blower provides a continuous and stable oxygen supply to the biofilter, maintaining the activity of the nitrifying bacteria and ensuring the filter’s purification function operates effectively.

3. Water Body Flow and Circulation

In recirculating aquaculture systems, blowers can also serve as the power source for air‑lift‑type water‑circulation devices, using aeration to drive water flow and maintain a high‑dissolved‑oxygen, gently flowing environment for the cultured organisms. The airflow generated by the blower is directed into the culture pond via a flow‑inducing device, creating water movement through the thrust of the air stream; flow velocities can reach 0.1 to 1.0 m/s.

In new farming models such as land-based, cylindrical, elevated fish ponds, air‑blowers are used to create a gas‑driven water flow, maintaining a consistently high water velocity that enhances fish mobility and promotes growth.

4. Circulating Water Purification

A recirculating aquaculture purification system designed based on the air‑lift pump principle uses an air blower as the sole moving mechanism. While lifting water, it simultaneously provides aeration to oxygenate the water and remove carbon dioxide, while minimizing aeration‑induced disturbance to both the rearing and settling zones. This design features a simple structure and reliable operation, contributing to energy savings and improved water quality.

IV. System Composition and Installation Key Points

A complete blower aeration system typically comprises the following core components:

• Blower host unit : Preferably a three-blade low-noise model or a high-efficiency suspended-type model.
• Aeration device Nanotubes are suitable for deep-water aquaculture, while disc-type systems are ideal for shallow water; a spacing of 3–5 meters is recommended.
• Piping system : PVC main pipe (DN50–DN100) connected to micro-perforated branch pipes (Φ10–16 mm)

During the installation process, the following key points require attention:

1. The fan should be installed above the water surface. , to prevent backflow of water into the fan, a check valve and a pressure gauge must also be installed.
2. The aeration disc should be positioned 30–50 cm above the pool bottom. , distribute evenly (e.g., in a “well”‑shaped pattern) to ensure uniform oxygenation throughout the pond.
3. In recirculating aquaculture systems, by means of Pressure balance pipe (A circular ring pipe matching the diameter of the aquaculture pond) connects the aeration pipes, ensuring uniform pressure throughout and achieving even aeration across the system.
4. In factory‑style aquaculture environments—where humidity, salt spray, and corrosive gases coexist—equipment should be installed in a dry, well‑ventilated control room. If installation within the rearing shed is unavoidable, it is recommended to construct a separate enclosure and equip it with a dehumidifier.

V. Operation, Maintenance, and Energy Conservation & Efficiency Enhancement

Key Points for Daily Maintenance

The daily maintenance of blowers directly affects the equipment’s service life and operational stability, and primarily includes:

• Motor Temperature Monitoring : Should be kept below 80°C
• Lubricant Level Check : Top up with ISO VG 68–220 gear oil monthly.
• Aeration Uniformity Inspection : Regularly inspect the aeration pipes for blockages and perform acid cleaning as needed.

Common Faults and Troubleshooting:

• Airflow reduction → clogged filter element or air leaks in the ductwork → clean the filter cotton and seal the connections.
• Abnormal vibration → uneven foundation or bearing wear → reinforce the foundation, replace the bearings
• Insufficient dissolved oxygen → Scaling on aeration pipes or insufficient aeration capacity → Acid cleaning and soaking, or upgrading the blowers.

Energy-saving and efficiency-enhancing measures

1. Variable-frequency control : Automatically adjusts fan speed based on diurnal dissolved oxygen fluctuations, further reducing energy consumption by 20%–30%.
2. IoT Monitoring : Paired with a dissolved oxygen sensor and a mobile app, it enables real-time alerts for hypoxia risks.
3. Mixed aeration : Use a Roots blower as the primary oxygenation device, supplemented by an impeller-type aerator to promote water circulation, making it well-suited for handling emergency situations such as heavy rainfall.
4. Equipment Upgrade For long‑term operating livestock farms, consider upgrading conventional Roots blowers to magnetic‑levitation or air‑bearing blowers; although the initial capital outlay is higher, the long‑term energy‑saving benefits are substantial.

Conclusion

As the core power equipment in aquaculture and recirculating water systems, blowers have evolved from simple oxygenation devices into multifunctional units that integrate aeration, flow generation, circulation, and water purification. From traditional Roots blowers to next-generation magnetic‑levitation and air‑bearing blowers, technological advances are driving aquaculture toward greater efficiency, energy savings, and智能化 (smart operation).

For aquaculture practitioners, understanding the operating principles of blowers, making informed equipment selections, ensuring proper installation, and implementing sound maintenance practices are not only essential for safeguarding production safety but also critical to reducing operational costs and enhancing farming profitability. As the factory‑based recirculating aquaculture system continues to gain traction, the importance of blowers—often referred to as the “lungs of underwater life”—will only continue to grow.

(This article is intended solely as general informational guidance; for specific equipment selection and system design, please consult qualified technical professionals.)