Government procurement case of a yellow-plate 3308 sewage treatment vehicle by a municipal sanitation department in Changsha: An analysis of procurement iteration—from the first batch to the upgraded version. In municipal sewage treatment—particularly for urban pipeline networks, pumping stations, and temporary emergency response scenarios—the yellow-plate 3308 sewage treatment vehicle has become a preferred choice for many sanitation units due to its moderate payload capacity and flexible superstructure configuration. This article traces the procurement experience of a municipal sanitation department in Changsha (hereinafter referred to as 'the unit') to present a real-world 'demand-driven iteration' case. Within two years, the unit conducted two procurement rounds: the first batch revealed design shortcomings; subsequently, requirements were enhanced, leading to the selection of Chengli Special Purpose Vehicle’s upgraded model. By comparing performance outcomes and costs, this case provides replicable equipment-selection references for other procurement entities. I. First-Batch Procurement: Trial of a Basic Yellow-Plate 3308 Sewage Treatment Vehicle In early 2024, the unit planned to procure four yellow-plate 3308 sewage treatment vehicles for cleaning septic tanks in old urban residential communities and for emergency handling of sewage pipeline networks. The total budget was capped at approximately RMB 2.033 million (about RMB 450,000 per unit). Following a tender process, four standard-configured vehicles based on the 3308 chassis were delivered. The chassis selected was from the Dongfeng series (compatible with models such as Chengli CLW5070GSSD6), and the superstructure consisted of a conventional sewage tank coupled with a vacuum pump. Key specifications of the first batch (based on publicly available tender information): Chassis: Dongfeng 3308, China VI emission standard Tank capacity: Approximately 8–10 m³ Suction pump: Conventional water-ring vacuum pump (maximum suction depth ~6 meters) Treatment method: Suction and discharge only—no solid-liquid separation or pre-treatment capability The vehicles operated normally during the first three months post-delivery. However, practical usage exposed three critical issues: Low treatment efficiency: Vacuum pumps frequently clogged when handling sewage containing large particulates, requiring manual cleaning 2–3 times per operation cycle—disrupting workflow continuity. No pre-treatment capability: Extracted sewage could not be solid-liquid separated on-site; thus, it had to be transported directly to wastewater treatment plants—increasing transport costs and risking secondary pollution. High maintenance frequency: Conventional vacuum pumps exhibited rapid seal wear after eight consecutive hours of operation, necessitating repairs every three months. In its quarterly review meeting, the unit reported: 'These four vehicles can only perform basic suction and discharge tasks—falling significantly short of our intended goal of “on-site treatment and volume-reduced transportation.”' This phase-specific pain point directly triggered the upgrade of requirements for the second procurement round. II. Identifying Shortcomings: Demand Evolution—from 'Capable of Suction' to 'Capable of Treatment' Based on operational data from the first batch, the unit redefined its procurement requirements by the end of 2024, issuing an updated technical tender document. Key enhancements included: Requiring the superstructure to incorporate solid-liquid separation and recirculating wastewater treatment functions, achieving sludge volume reduction (≥40%). Requiring the vacuum pump system to feature anti-clogging design, capable of handling soft debris up to ≤5 cm in diameter. Requiring full-vehicle intelligent operation—including liquid-level display, fault alarm, and remote monitoring interface. The budget was correspondingly adjusted to approximately RMB 621,000–678,000 per unit (aligned with local