Applications of Blowers in Niche Markets: Urban and Rural Wastewater Treatment and Upgrading Projects

Introduction

Against the backdrop of China’s ongoing efforts to advance ecological civilization and its dual-carbon strategy, urban and rural wastewater treatment is undergoing a profound transformation—from “scale expansion” to “quality improvement and efficiency enhancement.” Aeration blower As the “heart” of a wastewater treatment plant, blowers account for 50% to 80% of the facility’s total energy consumption, directly determining both effluent quality compliance and operational cost efficiency. This paper systematically examines the core value and evolving trends of blowers in urban and rural wastewater treatment and upgrade projects, analyzing them across five dimensions: industry policies, technical principles, equipment selection criteria, energy conservation and carbon reduction, and market prospects.

I. Policy-Driven: Urban and Rural Wastewater Treatment Enters the Deep Waters of Upgrading and Retrofitting

1.1 Top-level design continues to be strengthened

In recent years, the national government has introduced a series of policies to chart a clear roadmap for upgrading the wastewater treatment sector. The “Guiding Opinions on Promoting the Resourceful Utilization of Wastewater,” jointly issued by the National Development and Reform Commission and nine other departments, explicitly sets out that by 2025, wastewater treatment in environmentally sensitive areas will largely have been upgraded to meet higher standards, and that the reuse rate of reclaimed water in prefecture-level and above water-scarce cities nationwide will reach at least 25%. Meanwhile, the Ministry of Housing and Urban–Rural Development and the Ministry of Ecology and Environment have continued to advance the “14th Five-Year Plan” for urban wastewater treatment and resource utilization. In 2024, five ministries jointly issued the “Notice on Strengthening the Construction, Operation, and Maintenance of Urban Domestic Wastewater Pipeline Networks,” calling for a comprehensive enhancement of the performance of existing infrastructure.

As the 15th Five-Year Plan enters its initial phase, the Ministry of Ecology and Environment has issued the Action Plan for the Protection and Construction of Beautiful Rivers and Lakes (2025–2027), further elevating the improvement of domestic wastewater collection and treatment infrastructure as a core task. Policy priorities have shifted from “whether or not” to “how well,” with discharge standards progressively tightened—from Class I‑B to Class I‑A, and even to Surface Water Quality Grade IV or quasi‑Grade III—thereby compelling existing facilities to accelerate upgrades and compliance with higher standards.

1.2 Market Size: A Trillion-Yuan-Scale Industry is Accelerating Its Growth

Industry data indicate that in 2024, the Chinese urban wastewater treatment market reached RMB 152.8 billion, up 8.6% year on year; the urban domestic wastewater treatment market totaled RMB 175.6 billion, while the market for complete sets of wastewater treatment equipment is projected to grow to RMB 175.84 billion by 2025. Even more significant is the sub‑segment of upgrading and retrofitting projects: according to industry research firms, the nationwide market for such upgrades could exceed RMB 100 billion by 2025, with total investment in these projects expected to range from RMB 280 billion to RMB 350 billion between 2025 and 2030, at an annual compound growth rate of approximately 6.8%.

From a regional perspective, East China, North China, and the Yangtze River Economic Belt—characterized by high population density, concentrated industrial activity, and increasingly stringent regulatory oversight—account for more than 55% of the total. The developed eastern regions have taken the lead, with cities such as Shanghai explicitly setting targets to upgrade a number of wastewater treatment plants to quasi‑Class IV standards by 2025. Meanwhile, sewage treatment coverage in established towns continues to expand, with nearly universal collection and treatment capacity expected to be in place across built-up areas of such towns by 2035, making rural wastewater management a new growth driver.

II. The Heart of the Process: The Core Role of Blowers in Wastewater Treatment

2.1 Aeration: The Energy Input for Biochemical Treatment

The core process unit in wastewater treatment is the biochemical reaction tank—such as AAO, A²O, oxidation ditch, SBR, MBR, and others. In the aerobic zone, microorganisms degrade organic pollutants and carry out nitrification for nitrogen removal, a process that relies on an adequate supply of dissolved oxygen (DO). The blower’s function is to pressurize air and inject it into the water body in the form of fine bubbles via aerators—such as microporous diffusers or aeration hoses—thereby facilitating oxygen mass transfer.

It can be said that the blower is the “lung” of the entire biochemical treatment system: airflow volume determines oxygen‑supply capacity, air pressure dictates the ability to overcome water depth and pipeline resistance, and control accuracy ensures stable dissolved‑oxygen regulation. A blower that is improperly selected or operates with low energy efficiency not only leads to effluent COD, ammonia nitrogen, and total nitrogen levels exceeding regulatory limits, but also results in substantial electricity‑cost waste.

2.2 The “Absolute Heavyweight” in the Energy Consumption Structure

Industry consensus data indicate that aeration systems typically account for 50% to 70% of the total electricity consumption in wastewater treatment plants, with some processes even reaching as high as 80%. Taking a 100,000 m³/day A²O‑process plant as an example, the aeration stage can consume several million kWh annually, and electricity costs represent more than 30% of operating expenses. Consequently, the selection of appropriate blower technology and its operational optimization constitute the primary lever for reducing costs, improving efficiency, and achieving carbon emission reductions in wastewater treatment facilities.

III. Four Major Technological Approaches: Principles, Performance, and Selection Logic

The mainstream technologies currently used for aeration blowers in wastewater treatment include Roots blowers, multi‑stage centrifugal blowers, single‑stage high‑speed centrifugal blowers, and magnetic‑levitation or air‑bearing centrifugal blowers. These four types of equipment differ significantly in their operating principles, energy efficiency, and application scenarios.

3.1 Roots Blower: A Classic Positive-Displacement Design

Roots blowers are positive-displacement rotary machines that rely on the meshing and rotation of two three-lobe impellers within an “8”-shaped casing to deliver gas by means of volumetric changes. Their defining characteristic is… Constant current output — Within the design pressure range, flow fluctuations are minimal even when pipeline network resistance varies, making it well suited for aeration tanks with large liquid-level fluctuations and frequent changes in resistance.

• Advantage : Simple structure, low cost, and strong resistance to clogging (impeller‑free design allows handling gases containing trace impurities), with a wide pressure‑adaptation range.
• Disadvantage : Energy efficiency is relatively low, with overall unit efficiency typically ranging from 60% to 75%, and specific energy consumption exceeding 0.85 kWh/kNm³; noise levels can reach 85–105 dB(A), necessitating dedicated silencing rooms and vibration‑isolating facilities; mechanical friction components such as gears and bearings require regular lubrication and maintenance.
• Applicable Scenarios : Small and medium-sized wastewater treatment plants (with a daily treatment capacity of ≤20,000 tons), scenarios involving highly variable industrial wastewater quality, and township-level wastewater treatment stations with limited initial investment budgets.

3.2 Multistage Centrifugal Blowers: Turbine-Based Transition Scheme

Multistage centrifugal fans achieve stepwise pressure increase by connecting multiple impellers in series and are classified as turbomachinery fans. Compared with Roots blowers, they offer an efficiency improvement of 70%–80%, reduce noise levels to 80–90 dB(A), and provide a degree of flow‑rate regulation via inlet guide vanes or outlet valves.

• Advantage : Superior efficiency compared to Roots blowers, smoother operation, and excellent cost-effectiveness in high-flow applications.
• Disadvantage : Mechanical losses in the gearbox and bearings still persist, with a pronounced efficiency drop under partial-load conditions and a limited modulation range.
• Applicable Scenarios : A medium-sized municipal wastewater treatment plant (20,000–100,000 m³/day) employing the oxidation ditch process, which operates under relatively stable loading conditions.

3.3 Single-Stage High-Speed Centrifugal Blower: A High-Efficiency Solution for Large Airflows

A single-stage high-speed centrifugal fan drives a single impeller to rotate at high speed—typically 10,000–20,000 rpm—via a speed-increasing gearbox. Coupled with a three-dimensional flow‑optimized impeller design, the fan achieves an overall efficiency of 78%–83%. It offers a wide flow‑rate regulation range (40%–100%), making it well suited to the variable‑load requirements of large municipal wastewater treatment plants.

• Advantage : High efficiency, large flow rate, and excellent control performance.
• Disadvantage : Mechanical losses and maintenance costs of gearboxes remain, noise levels are relatively high, and they impose stringent requirements on the installation foundation.
• Applicable Scenarios : Large municipal wastewater treatment plant (≥100,000 m³/day), main aeration zone of the AAO process.

3.4 Magnetic‑Levitation and Air‑Levitation Centrifugal Blowers: A New Generation, Frictionless Solution

Magnetic‑levitation and air‑bearing blowers represent the current state of the art in aeration blowers, with both achieving contactless operation between the rotor and stator. Non-contact, frictionless operation , fundamentally eliminating mechanical losses.

Magnetic levitation blower By employing an active magnetic bearing system, the rotor is levitated in mid-air via electromagnetic forces. Coupled with a high-speed permanent‑magnet synchronous motor capable of speeds up to 20,000–40,000 rpm, the overall system efficiency reaches 82%–86%. Dissolved oxygen control accuracy achieves DO fluctuations of ≤±0.1 mg/L, noise levels are as low as 70–75 dB(A), and the service life spans 15–20 years.

Air-suspension blower It employs hydrodynamic air bearing (foil‑bearing) technology, whereby a high‑pressure gas film forms on the bearing surface during high‑speed rotor rotation, lifting the rotor. Its efficiency is approximately 2–3 percentage points lower than that of magnetic levitation, but it features a simpler structure, lower cost, and eliminates the need for complex magnetic bearing control systems and backup bearings.

Common advantages of the two types of floating wind turbines:

• Significant energy savings : 30%–40% more energy-efficient than conventional Roots blowers, and 10%–20% more energy-efficient than multi-stage centrifugal blowers;
• Intelligent adjustment : Supports inverter‑based stepless speed control, enabling precise airflow matching based on real-time DO feedback;
• Maintenance-free : No gearbox, no lubricating oil, and no mechanical wear; daily maintenance requires only replacing the air filter cotton.
• Low-noise and environmentally friendly : Operating noise is 20–30 dB lower than that of a Roots blower, eliminating the need to construct a separate silencer room.

Taking a 75 kW unit as an example, a magnetic‑levitation blower can save approximately 150,000 to 200,000 kWh of electricity annually compared with a Roots blower of the same capacity. At an industrial electricity rate of RMB 0.7 per kWh, this translates into annual electricity cost savings of RMB 100,000 to 140,000, with a typical payback period of 2 to 3 years.

IV. Upgrade Pathways for Blowers in Capacity-Enhancement Projects

4.1 The Core Conflict of Upgrading and Retrofitting

Upgrading and retrofitting a wastewater treatment plant—such as upgrading from Class I B to Class I A, or from Class I A to quasi‑Class IV—typically entails:

1. Nitrogen and phosphorus removal requirements are being raised. — Requires longer aerobic aeration times and more precise DO control;
2. The volume of water to be treated may increase. — The existing fan has insufficient airflow margin;
3. Energy consumption assessments are becoming stricter. — Water‑to‑electricity consumption has been incorporated into operational performance evaluations.

After standards are raised, conventional Roots blowers often face a triple dilemma: insufficient air volume, inadequate precision, and excessive energy consumption. Upgrading the blower has thus become one of the most cost‑effective yet investment‑lightest components in standard‑upgrade projects.

4.2 Three Typical Upgrade Modes

Mode 1: Stock Replacement — “Roots to Suspension”  
Replace the existing roots blowers directly with magnetic‑levitation or air‑bearing blowers, while retaining the original aeration piping and diffusers. This is the most common and quickest‑to‑implement retrofit approach, typically reducing aeration energy consumption by 25%–35% and significantly lowering plant‑site noise levels. The installation period is short—replacing a single unit takes just 1–2 days—and work can be carried out on a unit‑by‑unit basis without shutting down production.

Mode 2: System Optimization — “Equipment + Precise Aeration Control”  
Building on the replacement of high-efficiency blowers, a precise aeration control system—featuring closed-loop intelligent regulation based on online sensors for DO, ORP, ammonia nitrogen, and other parameters—is implemented. According to U.S. EPA data, a well‑designed precise aeration control system can further reduce aeration energy consumption by 25% to 40%. At a domestic wastewater treatment plant employing an A²/O process with a capacity of 100,000 m³/day, after implementing precise aeration optimization, aeration energy use was reduced by 25.7%, resulting in annual electricity cost savings exceeding RMB 3 million.

Mode 3: End-to-End Reengineering — “Process + Equipment + Intelligent Operations”  
For deep‑level effluent quality upgrade projects (meeting Class IV standards or higher), the aeration system is redesigned in conjunction with process‑route adjustments—such as adding MBR membrane tanks and denitrification deep‑bed filters—and equipped with suspended‑type blowers, precision aeration, and an intelligent water‑management platform to achieve full‑process energy optimization. Following the implementation of end‑to‑end automated control at a wastewater treatment plant in Linyi, aeration energy consumption per ton of water decreased by 4.6%, total energy consumption fell by 9.7%, and carbon emission intensity dropped by 18.6% year over year.

4.3 Special Considerations for Rural and Township Wastewater

Township and rural wastewater treatment facilities are characterized by small scale (50–5,000 tons/day), dispersed locations, limited operational and maintenance capacity, and significant fluctuations in influent loads. Such scenarios are best suited to:

• Compact, integrated air‑suspension blowers (power range 5.5–30 kW) feature maintenance‑free operation, reducing operational and maintenance burdens.
• Multiple small units are configured in parallel to accommodate load fluctuations.
• Remote monitoring and unattended operation mode.

V. Energy Conservation and Carbon Reduction: “Dual Carbon” Initiatives from the Perspective of Blowers

5.1 Composition of Carbon Emissions in the Wastewater Treatment Industry

The carbon emissions of wastewater treatment plants primarily encompass three categories:

• Direct Emissions (Scope 1) : During biochemical treatment, greenhouse gases such as N₂O and CH₄ are emitted;
• Indirect Emissions (Scope 2) : Carbon emissions from the thermal power generation side corresponding to purchased electricity — this is currently the largest source of carbon emissions for wastewater treatment plants, with aeration accounting for more than 50% of that share.
• Other Indirect Emissions (Scope 3) : Pharmaceutical production, equipment manufacturing, sludge treatment, and more.

Therefore, reducing aeration energy consumption is the most direct and quantifiable pathway for wastewater treatment plants to achieve carbon emission reductions.

5.2 Quantification of Carbon Emissions Reduction from Energy Efficiency Improvements

Taking a 100,000 m³/day wastewater treatment plant as an example, if the existing roots blowers are replaced with magnetic‑levitation blowers, and a 30% reduction in aeration energy consumption is assumed:

• Assuming the original aeration energy consumption is 0.25 kWh/m³, with an annual treatment volume of 36.5 million m³;
• Annual electricity savings = 36.5 million × 0.25 × 30% ≈ 2.74 million kWh;
• Based on the national grid’s average carbon emission factor of 0.5703 kgCO₂/kWh, annual CO₂ emissions are reduced by approximately 1,560 tonnes, equivalent to planting about 85,000 trees.

When combined with a precision aeration control system and photovoltaic green electricity, the overall carbon reduction rate can exceed 40%.

5.3 From “Equipment-Level Energy Efficiency” to “System-Level Energy Efficiency”

It is worth emphasizing that the blower’s energy efficiency alone is only the starting point. True energy savings and carbon reduction require systems thinking:

1. Gas supply end : High-efficiency suspended blowers replace conventional models;
2. Transmission and distribution end Optimize piping design to minimize valve throttling losses, and conduct regular inspections to detect and address pipeline leaks.
3. Release end : Use high-efficiency microporous diffusers (oxygen utilization rate ≥ 30%) and clean them regularly to prevent membrane pore blockage;
4. Control terminal : A feedforward-plus-DO feedback composite control strategy based on influent load prediction enables “on-demand aeration”;
5. Energy side : Rooftop photovoltaic systems combined with anaerobic digestion of sludge to produce biogas for power generation, creating an “energy‑self‑sufficient” wastewater treatment plant.

VI. Market Prospects and Technological Evolution Trends

6.1 The penetration rate of suspended fans is accelerating.

As upgrades to meet higher performance standards enter a period of rapid expansion, and as operators deepen their understanding of life-cycle costs (LCC), magnetic‑levitation and air‑bearing blowers are transitioning from “premium optional equipment” to “standard equipment for compliance.” Industry research indicates that by 2026, the penetration rate of suspended‑type blowers in new and retrofitted wastewater treatment plants will exceed 40%, with rates surpassing 60% in economically advanced regions such as East and South China. By 2030, suspended‑type blowers are expected to command roughly half of the wastewater‑treatment aeration market.

6.2 Directions for Technological Evolution

Parallel trends of large-scale and miniaturization On the one hand, high‑power magnetic‑levitation blowers with individual capacities of 300–500 kW are steadily maturing, making them well suited for large wastewater treatment plants handling more than 100,000 tons per day. On the other hand, miniature air‑bearing blower units ranging from 5.5 to 15 kW are rapidly gaining traction, serving the decentralized wastewater‑treatment market in towns and rural areas.

Deep Integration of Intelligence The fan features a built-in PLC and IoT module, enabling remote diagnostics, predictive maintenance, and online energy‑efficiency analysis, while seamlessly integrating with plant‑level SCADA systems and smart water‑management platforms—evolving from “standalone energy saving” to “intelligent cluster control.”

Domestic substitution is accelerating. The localization rate of core components—high-speed permanent‑magnet motors, magnetic bearing controllers, foil bearings, and three‑dimensional impellers—continues to rise. As a result, the overall system price has dropped by 30%–50% compared with imported brands, and the payback period has been shortened to 1.5–2.5 years, further unlocking market demand.

Green Power Coupling : The fan variable-frequency system, in synergy with photovoltaic generation and energy storage, leverages the price differential between peak and off-peak periods to optimize operational strategies, achieving dual optimization of “economic operation” and “low-carbon operation.”

6.3 Outlook for the 15th Five-Year Plan Period

Looking ahead to the 15th Five-Year Plan period, urban and rural wastewater treatment will exhibit three major trends: first, discharge standards will continue to tighten, with quasi‑Class IV and quasi‑Class III becoming the new baseline in sensitive areas; second, the operational model will shift from “construction‑driven” to “operation‑driven,” with energy‑efficiency metrics emerging as a core performance indicator; and third, wastewater treatment plants will transition from “treatment facilities” to “resource‑and‑energy hubs,” with energy self‑sufficiency, phosphorus recovery, and reclaimed water utilization becoming standard features.

In this process, blowers, as the dual core of energy consumption and process technology, will continue to unlock substantial market opportunities and carbon‑reduction potential through technological upgrades and system optimization.

Conclusion

Urban and rural wastewater treatment, along with upgrades to meet stricter standards, is not merely a tough battle to achieve environmental compliance; it is also an operational‑efficiency revolution centered on energy conservation and carbon reduction. Although blowers are just one component among the many pieces of equipment in a wastewater treatment plant, they account for more than 50% of the plant’s total energy consumption and play a critical role in ensuring stable effluent quality. From Roots‑type to centrifugal designs, from friction‑based to suspended‑bearing systems, and from fixed‑speed, mains‑frequency operation to intelligent variable‑frequency drives, each technological advancement in blower technology propels the wastewater treatment industry toward lower energy use, reduced emissions, and greater levels of intelligence.

For equipment manufacturers and system integrators, whoever masters the core technologies of efficient suspended‑solid treatment and delivers an integrated “equipment + control + operations & maintenance” solution will gain a competitive edge in this wave of trillion‑yuan‑scale upgrades to meet higher standards. For wastewater operators, rationally selecting blower solutions that align with the target process—guided by life‑cycle cost considerations—is key to achieving both compliance with effluent quality standards and cost reduction while cutting carbon emissions.