Shanxi Xinzhou Sewage Treatment Plant Energy-Saving Retrofit Project
At the foot of Mount Wutai, upstream of the Hutuo River, a "quiet energy revolution" is taking place at the Wutai County Sewage Treatment Plant. This county-level plant, which treats 25,000 tons of domestic sewage and tourism wastewater per day, was once trapped in the dilemma of balancing "compliance" and "cost reduction." In July 2020, four Krupp permanent magnet variable frequency oil-free screw blowers replaced the roaring traditional Roots blowers. Not only did they achieve a comprehensive energy saving rate of over 25%, setting a new industry benchmark, but they also delivered the compelling economic case of "recovering the incremental investment within two years," providing a replicable "Wutai model" for energy-saving renovations in northern county-level sewage treatment plants.
The "Energy Anxiety" of County-Level Sewage Plants: When Environmental Pressure Meets Operating Costs
As a typical northern county-level sewage treatment plant, the Wutai plant faces unique challenges. Winter water temperatures drop below 8°C, resulting in low nitrification efficiency and demanding extremely high sensitivity from the aeration system adjustment. The inefficient operation of Roots blowers (full load efficiency ≤65%) makes them "electricity hogs." At the same time, county-level finances harbor doubts about "high-investment, slow-return" energy-saving technologies, making the investment payback period a key decision factor.
The original Roots blowers operate with "extensive" aeration, relying only on start/stop or bypass valve adjustment, resulting in poor dissolved oxygen (DO) control accuracy (fluctuations often exceeding ±1.5 mg/L). The biochemical tank frequently experiences "over-aeration" or "expansion of anoxic zones," wasting energy and affecting nitrogen and phosphorus removal efficiency. Even during low-load periods, the motor still operates near full load, causing huge idle losses. Gear and impeller wear lead to performance degradation year by year, with air volume衰减 (decline) often exceeding 15% after three years. Additionally, excessive noise affects work and production.
The precise breakthrough of Krupp permanent magnet variable frequency oil-free screw blower
In July 2020, four Krupp permanent magnet variable frequency oil-free screw blowers were installed beside the biochemical tank, with their technical advantages directly addressing the operational pain points of the county-level sewage treatment plant.
1. Permanent magnet variable frequency: making every kilowatt-hour "precisely delivered"
Adopting a permanent magnet synchronous motor (IE5 energy efficiency class) with rated efficiency of 96%, an 8%-10% improvement over traditional asynchronous motors. The intelligent variable frequency drive (PID control) adjusts speed in real time based on online DO meter data (set value 2.0 mg/L), controlling DO fluctuation within ±0.3 mg/L. During low-load nighttime periods, the blower automatically operates at 30% rated power, avoiding "overkill" waste.
2. Oil-free design: adding "double insurance" for stable operation
100% oil-free compression completely eliminates the risk of lubricating oil emulsification and coking, especially adaptable to low-temperature winter conditions in northern regions. The screw host has a designed lifespan exceeding 100,000 hours, with core bearings (mean time between failures) reaching 100,000 hours, a 3x improvement over Roots blowers. The fully enclosed structure reduces noise from 105 dB(A) to 75 dB(A), solving the "neighboring opposition effect."
3. Intelligent control: making four blowers "work in perfect coordination"
The cloud platform-based intelligent control system automatically optimizes blower start/stop combinations and load distribution based on water volume prediction models, enabling remote interlocking control to ensure that any single equipment failure does not affect process operation.
25% energy saving effect, a visible "green ledger"
Based on electricity price calculation, annual electricity cost savings are 480,000 yuan; annual maintenance cost savings are 58,000 yuan; comprehensive annual benefits are 538,000 yuan, with a payback period of approximately 2 years. At the same time, environmental benefits are also evident, with annual carbon dioxide emission reduction of about 589 tons.
The successful renovation of Wutai County Sewage Treatment Plant demonstrates that green technology itself is productivity. When the permanent magnet variable frequency oil-free screw blower offers the definite benefit of "two-year payback," alleviating the concerns of county-level finances regarding environmental protection investment, technology is no longer an expensive ornament but a meticulously calculated "energy-saving partner."
