Government procurement case of yellow-plate sewage treatment vehicles in Tianjin: In-depth analysis of volume selection and winning-bid solutions. In northern cities—especially coastal ones like Tianjin—municipal sanitation departments face increasingly refined requirements for specialized vehicles used in sewage, sludge, and septic tank cleaning operations. Yellow-plate sewage treatment vehicles are commonly selected for government procurement due to their high load capacity and large operational volume. However, procurement entities often struggle with volume selection among options such as 3 m³, 5 m³, 8 m³, and 12 m³ models: too small a volume compromises efficiency, while too large a volume may lead to underutilization and waste. This article draws upon a real government procurement case by a municipal sanitation department in Tianjin, integrating product features and bid-winning data from Chengli Special Purpose Vehicle Co., Ltd. (hereinafter referred to as "Chengli Automobile") to present a scientific volume-selection methodology and bid analysis—with special emphasis on cold-weather engine start-up reliability, hydraulic system stability, and maintenance strategies under northern winter conditions (e.g., temperatures down to −15°C). Case Background: Sewage Treatment Vehicle Procurement Requirements of a Tianjin District Urban Management Bureau In Q4 2025, an urban management bureau in a district of Tianjin planned to procure a batch of yellow-plate sewage treatment vehicles for residential septic tank cleaning, municipal pipeline unclogging, and emergency sewage extraction within its jurisdiction. According to publicly released tender information, the budget was set between approximately RMB 331,000 and RMB 500,000 per unit, with mandatory compliance to China VI emission standards, full official vehicle type approval (Announcement), and eligibility for normal registration and annual inspection. Given that winter temperatures in Tianjin can drop to around −15°C, the procuring entity explicitly required reliable cold-weather engine starting performance and stable hydraulic operation at low temperatures. After multiple rounds of tendering and evaluation, Chengli Automobile secured the contract and successfully delivered multiple units of yellow-plate sewage treatment vehicles, leveraging advantages including nationwide warranty support for Dongfeng chassis, lifetime after-sales service for superstructures, and zero-inventory local production and rapid delivery from Suizhou. The primary models supplied included 5 m³, 8 m³, and 12 m³ variants. This article analyzes volume selection logic based on actual operational scenarios. Core Logic of Volume Selection: Starting from Daily Operational Volume In government procurement, volume selection is not arbitrary—it is grounded in actual workload and operational frequency. Below are the daily volume calculation formula and matching reference table tailored to typical Tianjin municipal sanitation scenarios. Daily Volume Calculation Formula Assuming an 8-hour workday, with each round-trip cycle (including loading, transportation, and unloading) taking T minutes, and effective single-load volume being V cubic meters, the maximum daily processing volume Q is calculated as: Q = V × (480 ÷ T) where 480 represents the total number of minutes in 8 hours. For example, if each round-trip requires 60 minutes, the vehicle can complete up to eight cycles per day. Workload Matching Table The table below matches common Chengli yellow-plate sewage treatment vehicle models (e.g., CLW5070GSSD6, referencing official Announcement parameters) to typical municipal sanitation applications in Tianjin: Volume (m³) | Chassis Type | Daily Volume (assuming 60-min round-trip) | Typical Application Scenarios | Reference Unit Price (incl. tax, landed price, in ten-thousand RMB) 3 | Dongfeng Light-Duty Yellow-Plate | 24 m³/day (8 × 3 m³) | Septic tank cleaning in residential communities; narrow-street operat