Background: Joint procurement across multiple districts/counties to address high-load sewage treatment demands during the rainy season. In summer 2025, several districts and counties in Chongqing experienced prolonged heavy rainfall, placing unprecedented pressure on municipal sewage treatment systems. Aging pipelines suffered blockages and overflows, urgently requiring highly efficient and highly mobile sewage treatment equipment for emergency support. To standardize procurement specifications and reduce per-tender costs, a municipal sanitation and environmental management department in Chongqing led a joint tender involving urban management bureaus from five districts/counties—including Yuzhong, Jiangbei, and Nan'an—for CN6 Dongfeng 3308-mm wheelbase sewage treatment vehicles. The core procurement requirements focused on three key aspects: (1) vehicles must comply with China VI emission standards to meet local environmental regulations; (2) chassis must be Dongfeng models with a 3308-mm wheelbase, balancing maneuverability and payload capacity; and (3) the superstructure must be specially optimized for Chongqing’s hot-humid climate—particularly regarding anti-corrosion coating and sealant durability—to withstand high-frequency operation during the rainy season, which accelerates corrosion and wear. Technical Specification Development: Precise Matching from Climate to Operational Conditions. During technical solution development, the joint procurement team referenced official announcement parameters of Chengli Special Purpose Vehicle Co., Ltd. (hereinafter referred to as 'Chengli'), including models such as CLW5070GSSD6, and refined them based on actual local operating conditions in Chongqing. Anti-Corrosion Coating Requirements: Chongqing’s air humidity remains consistently high, reaching over 85% relative humidity during the rainy season. The procuring party explicitly required dual-layer anti-corrosion coating—epoxy resin primer plus polyurethane topcoat—on tanks and piping systems, with a minimum thickness of 200 microns, ensuring no visible rust for at least five years. Sealant Durability: To address premature aging and failure of rubber seals under hot-humid conditions, all sealing components—including manhole covers and suction/discharge valves—must use oil- and weather-resistant fluorocarbon rubber, accompanied by test reports verifying performance across a temperature range of -20°C to 120°C. Operational Frequency Adaptability: Considering potential continuous operation during the rainy season (averaging 6–8 hours per day), the hydraulic system must incorporate forced cooling to prevent excessive oil temperature, which could otherwise reduce efficiency or cause failures. Announcement Compliance and Registration: All tendered vehicles must possess complete official announcements and be eligible for normal registration, annual inspection, and commercial operation licensing at Chongqing’s Vehicle Administration Office. Chengli’s offered models have passed MIIT announcement certification and are qualified for nationwide registration. Centralized Tendering and Chengli’s Batch Supply Advantages: This procurement involved eight units of CN6 Dongfeng 3308-mm wheelbase sewage treatment vehicles, with a total budget capped at approximately RMB 3 million (based on publicly available tender information, unit price ~RMB 350,000–400,000). Following open tendering and expert evaluation, Chengli Special Purpose Vehicle was selected as one of the winning suppliers, owing to the following advantages: Factory-direct sales with no intermediaries: Compared to 4S-channel procurement, this eliminates an estimated price premium of RMB 8,000–15,000 per unit at identical configurations, directly lowering procurement costs. Localized production and rapid delivery: Chengli is headquartered in Suizhou, Hubei—approximately 600 km from Chongqing—with convenient logistics access. Standard models can be delivered within 7–15 days; for this project,