[Mainland China] Shaanxi Reclaimed Water Plants Break New Ground with "Two Pathways": Xixian New Area's 20,000 t/d Prefabricated Construction, Yan'an New Area's 25,000 t/d Underground Plant Achieves Class III Surface Water Standards

Key Highlights: The 10th Reclaimed Water Plant of Xixian New Area treats 2万 tons of domestic and production wastewater per day, adopts prefabricated construction and uses aeration equipment exhaust gas to replace traditional mixing and plug-flow equipment, greatly simplifying equipment and reducing operation and maintenance energy consumption; a wastewater treatment plant with a daily treatment capacity of 2.5万 tons in Yan'an New Area is built entirely 16 meters underground in Luyi Ecological Park, and its effluent is upgraded from quasi-Class IV to Class III surface water through natural purification by aquatic plants and microorganisms, then transported through a 74.98-kilometer smart pipeline network for greening, municipal use, and ecological water replenishment.

I. Prefabricated Construction: First Solve "How to Build"

Traditional wastewater treatment plants have long construction cycles, extensive on-site wet operations, and large quality fluctuations, and they are often disconnected from surrounding urban functions by the time they are completed. Prefabricated construction offers an answer: break structures into standardized components, prefabricate them in factories, and assemble them on site.

The 10th Reclaimed Water Plant of Xixian New Area is a sample of this path. The plant can "devour" 2万 tons of domestic and production wastewater every day. After several production stages, it is "transformed" and regenerated into clear reclaimed water for uses such as greening and heating.

More noteworthy is its energy-saving design: the reclaimed water plant relies on aeration equipment exhaust gas to replace traditional mixing and plug-flow equipment, greatly reducing the number of equipment units and operation and maintenance costs, with overall operating energy consumption substantially lower than that of traditional wastewater treatment plants. Recovering the exhaust gas discharged from the aeration system for plug-flow mixing is essentially a secondary internal use of energy that would otherwise be wasted—fewer equipment units, fewer failure points, and lower power consumption and labor requirements.

The value of prefabricated construction goes beyond the construction period. For cities, it means a shorter window of construction disturbance, more controllable project quality, and lower retrofit costs for future capacity expansion—standardized components can be added as needed without starting over.

II. Fully Underground: Then Solve "Where to Build"

If prefabricated construction solves "how to build," Yan'an's practice answers "where to build and how to integrate into the city."

Yan'an is located on the Loess Plateau, where water resources are scarce and the contradiction between supply and demand is prominent. How to recycle limited water resources is a common challenge faced by water-scarce cities in the north.

In Luyi Ecological Park in Yan'an New Area, beneath your feet is smooth lawn, citizens stroll with children in the distance, and the wind over the lake carries moisture. The source of this lake water is the underground wastewater treatment plant 16 meters deep beneath your feet. The plant was built and operated by Shaanxi Construction Engineering Co., Ltd., treats 2.5万 tons of domestic sewage per day, and reuses reclaimed water for the city's greening, municipal use, and landscape water replenishment.

"When we first heard that a wastewater treatment plant was going to be built, we were a little worried," said a nearby resident. "Now the wastewater treatment plant is built underground, and above ground is a park. It has no impact at all on residents' lives."

This statement reveals the core value of the fully underground layout: it simultaneously solves the two problems of land constraints and the NIMBY effect. In urban new areas where land resources are tight, "sinking" the wastewater treatment plant underground allows the surface space to be given over to public functions such as parks, transit hubs, and parking lots, and the comprehensive return on land is far higher than that of a single municipal facility.

III. Water Quality Leap: From Quasi-Class IV to Class III Surface Water

The third step of the Yan'an project is to push reclaimed water quality up another level.

The operation team of Yan'an Xintou Environmental Protection Co., Ltd., a subsidiary of Shaanxi Construction Engineering Co., Ltd., introduces treated quasi-Class IV reclaimed water that meets standards into the park water system, uses aquatic plant roots and microorganisms for natural purification, and supplements this with a 24小时 online intelligent monitoring system, further upgrading water quality to the Class III surface water standard.

Fish swim in the lake water, and aquatic plants flourish along the banks—this is the most intuitive acceptance report for the combined process of "artificial treatment + natural purification."

The significance of this path lies in the fact that it partially transfers the marginal cost of advanced treatment to the ecosystem itself. Artificial processes are responsible for reducing pollutants to a level that the ecology can accept, while subsequent stabilization and quality improvement are completed by aquatic plants, microorganisms, and the lake body's self-purification capacity, thereby obtaining higher-quality effluent without endlessly adding energy consumption and chemicals.

IV. Smart Pipeline Network: 74.98 Kilometers, Fully Traceable and Dispatchable

After reclaimed water "can be produced," the key lies in "being delivered."

The treated reclaimed water from the Yan'an project is transported through a 74.98-kilometer smart pipeline network and applied to scenarios such as Yan'an urban greening irrigation, municipal miscellaneous use, and ecological water replenishment, realizing water resource recycling.

More critically, leveraging cutting-edge technologies such as Digital Twin and intelligent monitoring, the project achieves full traceability, controllability, and dispatchability of Reclaimed Water quality, quantity, and flow destination throughout the entire process. The operations team can monitor the system's operating status in real time from the central control room—whether water quality meets standards, how water volume is allocated, and where the water goes are all real-time data that can be queried, traced, and dispatched.

This point is crucial for the large-scale promotion of Reclaimed Water. The long-standing pain point in the industry is precisely "water can be produced but not delivered" and "there is Reclaimed Water but no users, there are users but no Reclaimed Water"—mismatched pipeline networks and opaque dispatch lead to a mismatch between capacity and demand. Intelligent pipeline networks combined with a Digital Twin platform essentially install "eyes" and a "brain" on the Reclaimed Water system, transforming supply-demand matching from empirical judgment to data-driven decision-making.

V. Three Insights for the Industry

First, the construction method itself is becoming a competitive advantage. Prefabrication pushes wastewater treatment plants from "engineering projects" toward "industrial products," redefining construction timelines, quality, and full life-cycle costs. For owners who need to quickly address shortcomings in urban built-up areas or new districts, this is a factor considered earlier than process parameters.

Second, "building plants underground + creating parks above ground" has become the standard answer to overcoming NIMBY opposition. From Yan'an to Chengdu Eastern New Area, Beijing Huai Fang and Bishui, and other large-scale fully underground Reclaimed Water plants, this model is being repeatedly validated. What it changes is not the treatment process, but the spatial relationship between wastewater treatment plants and the city.

Third, the level of digitalization on the operations side determines the actual utilization rate of Reclaimed Water. Meeting treatment standards is only the starting point. Only by digitizing all data on water quality, quantity, and destination can refined allocation for multiple users and multiple scenarios be truly supported—this is also the inevitable path for Reclaimed Water to move from "can be reused" to "reused economically."

For water-scarce cities in northern China, the two paths of Yan'an and Xixian offer a clear conclusion: the bottleneck of Reclaimed Water plants has long ceased to be the technology itself, but rather whether they can be built quickly, whether they can fit, and whether the water can be delivered. Once these three points are resolved, limited water resources can truly be circulated.

About TIANYI TECH

Hong Kong TIANYI Technology Limited (TIANYI LIMITED) focuses on Industrial Wastewater treatment and water resource reuse, centered on three core products: Industrial Wastewater Treatment AI Agent, Industrial Water Reuse Optimization System, and Industrial Water System Digital Twin, providing enterprises with full-chain services from water quality diagnosis and process optimization to intelligent operations, helping customers improve water reuse rates and reduce operating costs.

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