Case Study and Solution Analysis of Xi'an Municipal Government Procurement of National VI Dongfeng 3308 Wheelbase Sewage Treatment Vehicles. In Northwest China—particularly in Xi'an, a city combining historical-cultural significance with industrial development needs—the procurement of sewage treatment vehicles presents unique challenges. In early 2026, a municipal sanitation department in Xi'an (hereinafter referred to as the 'Client Unit') urgently required a batch of sewage treatment vehicles adapted to local sandstorm conditions due to aging pipeline renovation in old residential communities and seasonal sewage accumulation. The department head specified clear requirements: 'The vehicle must be highly mobile, effectively filter contaminants, resist sand and dust intrusion, and feature extended maintenance intervals.' This requirement reflects a rigorous assessment of conventional vehicle reliability under operational conditions at the edge of desertification zones. After internal deliberation and on-site inspections, the Client Unit ultimately selected the National VI Dongfeng 3308 wheelbase sewage treatment vehicle manufactured by Chengli Special Purpose Vehicle Co., Ltd. (hereinafter referred to as 'Chengli'). This article analyzes key aspects of the case—from model selection and field inspection to contract signing and final delivery—and provides practical references for dust-proof sealing design and filter system maintenance intervals tailored to desertification-prone regions. I. Department Head’s Requirements: Specific Pain Points in Desertification-Zone Operations The Client Unit is located in the suburban northwest area of Xi'an, where sandstorm weather occurs frequently throughout the year. During the project launch meeting, the department head emphasized: 'Our sewage treatment vehicles must do more than simply pump and discharge wastewater. With heavy sand and dust, inadequate sealing leads to rapid clogging of filters—increasing maintenance costs and reducing operational efficiency.' Specific requirements included: - Dustproof Sealing Performance: Critical components—including tank interface joints and engine air intake systems—must incorporate high-grade dustproof design to prevent sand/dust ingress and subsequent failures. - Filter System Maintenance Interval: While conventional models require filter replacement every 3–6 months under standard operating conditions, local requirements mandate extension to 6–9 months—or adoption of an easily maintainable modular structure. - Chassis Adaptability: The Dongfeng 3308 wheelbase chassis was selected due to its dense service network across Northwest China and compliance with National VI emission standards. - Budget Control: Consistent with local procurement practices, the unit budget was capped at approximately RMB 339,000 per vehicle; publicly available tender data indicated market prices for 4-cubic-meter sewage treatment vehicles ranged between RMB 280,000–350,000. II. Internal Model Selection Process: Chengli Selected After Comparative Evaluation Initially, the Client Unit’s procurement team evaluated multiple specialized vehicle manufacturers—including local modification workshops and leading national brands—focusing on chassis configuration, upper-body construction quality, after-sales service coverage, and real-world application cases. According to internal meeting records, Chengli emerged as the top choice based on the following strengths: - Complete Regulatory Compliance: Chengli’s CLW5070GSSD6 model (built on the Dongfeng 3308 wheelbase) meets National VI emission standards, carries full official product announcements, and is eligible for nationwide registration and annual inspection. - Dustproof Design: Chengli employs dual-layer rubber gaskets plus stainless-steel clamps at tank sealing points and equips the engine air intake system with standard desert-rated air filters—effectively blocking airborne sand and dust. - Filter System Maintainab