Government procurement case and bid-winning solution interpretation for the CN6 Dongfeng 3308 mm wheelbase sewage treatment vehicle in Qiqihar. In northern frigid regions—especially high-latitude cities like Qiqihar—winter sewage treatment and sanitation operations face severe challenges. Low temperatures cause hydraulic system stagnation and difficult engine starts, directly affecting equipment availability. A municipal sanitation department recently conducted a public tender for the 'CN6 Dongfeng 3308 mm wheelbase sewage treatment vehicle', with a budget controlled within approximately RMB 278,000–390,000 (based on local procurement conventions). Chengli Special Purpose Vehicle ultimately won the bid, delivering the units based on its heavy-duty operational design and proven low-temperature adaptation solutions. This article analyzes, using this real-world case as a foundation, the vehicle selection logic, technical highlights, and procurement considerations under high-frequency operational conditions. I. Project Background and Customer Requirements Qiqihar is located in western Heilongjiang Province, where winter minimum temperatures can reach -35°C to -40°C, and ice-covered periods last up to five months. The municipal sanitation department routinely handles urban pipeline unclogging, septic tank cleaning, and emergency operations at wastewater treatment plants, requiring equipment to operate intensively for 8–10 hours daily. Key requirements specified in the procurement tender included: 1. CN6 emission compliance, aligned with current environmental regulations; 2. Chassis: Dongfeng 3308 mm wheelbase, suitable for maneuvering through narrow urban streets; 3. Freeze-resistant starting capability and hydraulic system stability under low temperatures; 4. Comprehensive winter maintenance plan; 5. Fully integrated upper-body assembly and chassis design, with complete official type-approval documentation ensuring nationwide registration and annual inspection eligibility. According to publicly available tender information, Chengli Special Purpose Vehicle secured the contract, delivering the Chengli CLW5090GXWD6 sewage treatment vehicle, built on the Dongfeng DOLICA chassis and equipped with a full-power PTO and independent hydraulic system. II. Technical Interpretation of Chengli’s Bid-Winning Solution To address Qiqihar’s extreme cold operating conditions, Chengli implemented targeted optimizations to the sewage treatment vehicle, focusing on three key areas: 1. Freeze-Resistant Starting Performance The chassis is fitted with a fuel-fired heater and low-temperature starting assist device, enabling reliable engine start-up even at -35°C. Additionally, the water tank and piping incorporate electric heat-tracing insulation layers to prevent sewage freezing inside the tank. Per the official CLW5090GXWD6 type-approval specifications, the tank offers an effective capacity of approximately 5 m³, constructed from Q235 carbon steel with an interior anti-corrosion coating and pre-installed heating-circulation interfaces for convenient integration with external heat sources during winter. 2. Low-Temperature Hydraulic System Stability The hydraulic system constitutes the core of the sewage treatment vehicle. Chengli selected low-temperature hydraulic oil (grade HV-46) and installed a hydraulic oil cooler along with a temperature-control regulating valve, ensuring stable oil viscosity across a wide operating temperature range (-30°C to +40°C) and preventing pump cavitation or sluggish actuator response caused by low temperatures. This design has undergone field validation over three consecutive winters with Qiqihar’s local sanitation authority, with user feedback indicating 'a significant reduction in winter operational failures'. 3. Winter Maintenance Plan Chengli provides a dedicated winter maintenance manual with the vehicle, including the following guidelines: - Weekly inspection of electric heat-tracing tapes and insulation integrity;