I. Case Background and Requirement Analysis In early 2025, a municipal sanitation department in Baotou City, Inner Mongolia, launched a public tender for specialized wastewater treatment vehicles as part of its urban wastewater treatment capacity enhancement project. The project required vehicles capable of operating reliably in northern China’s severe winter conditions, featuring high-efficiency wastewater suction, solid-liquid separation, and temporary storage capabilities, while complying with China VI emission standards. According to the tender documents, the total budget was capped at approximately RMB 1.693 million, with plans to procure two Dongfeng wing-opening wastewater treatment vehicles. Preliminary research conducted by the procuring entity indicated that local winter temperatures can drop to -25°C to -30°C. Conventional box-type vehicles often suffer from frozen pipelines and difficult pump startup under such low-temperature conditions. Therefore, the tender specifications explicitly emphasized vehicle cold-weather adaptability, anti-freezing measures, and after-sales service support. II. Winning Solution and Technical Features Chengli Special Purpose Vehicle Co., Ltd., leveraging its extensive expertise in special-purpose vehicle development, successfully delivered two Dongfeng wing-opening wastewater treatment vehicles. Based on Dongfeng chassis, these vehicles feature an integrated wastewater treatment system independently developed by Chengli. Key technical specifications include: Chassis Model: Dongfeng DOLICA series (e.g., official announcement model CLW5070GSSD6), equipped with a China VI-compliant diesel engine delivering approximately 110 kW output—sufficient for demanding northern road conditions. Wastewater Tank Capacity: Approximately 5 m³, constructed from low-temperature-resistant stainless steel; the tank exterior is insulated to prevent freezing during winter. Suction System: Fitted with a high-capacity vacuum pump, achieving a maximum suction depth of 7 meters and a suction rate of ~40 m³/hour—capable of handling high-sediment wastewater. Solid-Liquid Separation Unit: Integrated filtration system enabling separation of solids for off-site disposal, while treated liquid meets discharge or reuse standards. Wing-Opening Body: Hydraulically actuated wing-opening design for convenient daily maintenance and inspection. Per local procurement practice, the unit price for this batch was approximately RMB 750,000 per vehicle, inclusive of chassis, superstructure, transportation, and one year of complimentary maintenance service. Chengli’s proposal included nationwide warranty coverage for the Dongfeng chassis (provided directly by Dongfeng’s authorized network) and lifelong after-sales support for the superstructure, with spare parts dispatched within 24 hours—significantly reducing customers’ long-term operation and maintenance costs. III. Winter Operation Guidelines: Maintenance and Operation in Harsh Northern Climates To address Baotou’s extreme winter conditions, Chengli’s technical team provided dedicated winter operation guidance upon delivery. Key recommendations are as follows: 1. Winter Maintenance Essentials Antifreeze Replacement: Use antifreeze rated for -35°C and regularly inspect fluid level and freeze point to prevent engine and cooling system freezing. Engine Oil Selection: Use low-viscosity oil (e.g., 5W-30 or 0W-30) during winter to ensure adequate lubrication at startup and minimize engine wear. Battery Maintenance: Battery capacity declines significantly in cold weather. Check electrolyte density and terminal cleanliness weekly; consider using battery insulation sleeves when necessary. Piping Insulation: Wastewater tanks and connecting pipelines are externally insulated; however, inspect insulation integrity regularly to prevent pipe rupture caused by ice accumulation. 2. Cold-Weather Starting Recommendations Preheating Procedure: Activate the engine preheating system (e.g.,