​China Environment News | Solving the Difficulty of "Large Concentration and Large Cut off" in Water Control in Large Cities, Starting from Underground Parks

"Look! After being treated by the water plant, the water flows back into the Nanming River from here." Standing on the boardwalk in the park, Hao Wenlei, Deputy Director of Qingshan Regenerated Water Plant in Guiyang City, Guizhou Province, pointed to the front outlet and explained. On the banks of the Nanming River, this scenic park adjacent to the river has a pleasant scenery. In the park, the pavilion is quiet, the benches are comfortable, table tennis enthusiasts are engaged in fierce battles, and the basketball court is also bustling. This place has complete facilities and is an ideal place for nearby residents to relax, take walks, and exercise.

The ecological replenishment water outlet of Qingshan Reclaimed Water Plant. Photo by Wang Yuning.

So, what is the connection between the park and the recycled water plant? The mystery lies underground in this park - a fully sunken Qingshan recycled water plant quietly sits, designed, constructed, and operated by China Water Environment Group. Why build a recycled water plant underground? What are the advantages of an underground recycled water plant? A reporter from China Environment News visited the Qingshan Reclaimed Water Plant.

From "turning black and smelling" to "almost identical to pure water"

"Since the 1990s, with economic development and population growth, problems such as garbage accumulation, domestic sewage, and corporate pollution have become increasingly prominent, continuously breaking through the ecological environment capacity of the Nanming River, causing water quality deterioration, severe black and odorous conditions, ecological extinction, and becoming a 'lifeless river'." Hao Wenlei pointed to a comparative diagram of Nanming River governance as an explanation. The picture shows footage of some key sections of the Nanming River captured in 2013 and 2022. Before the treatment, the Nanming River turned black and there were many floating debris on the river, which was extremely polluted.

Comparison chart of Nanming River governance. Photo by Wang Yuning

As the mother river of Guiyang and an important tributary of the Wujiang River, the health status of Nanming River is directly related to the ecological balance and sustainable development of the entire Guiyang city and even the Wujiang River basin. Solving the pollution problem of Nanming River is urgent.

In November 2012, Guiyang City launched a systematic and new management of the water environment in the Nanming River Basin. "The governance of Nanming River is divided into three stages: the first stage is' emergency ', the second stage is' root cause', and the third stage is' system improvement '. The Qingshan Reclaimed Water Plant is a sewage treatment facility built to improve water quality during the' root cause 'period." Hao Wenlei said.

In 2014, the Qingshan Reclaimed Water Plant was completed and put into operation, with a sewage treatment capacity of 50000 tons/day, a service area of approximately 10.86 square kilometers, and a total population of approximately 267000 people.

Building a recycled water plant underground has multiple advantages. "If we choose to build on the ground, it will take up 76 acres, while the sunken Qingshan Reclaimed Water Plant only takes up 32 acres," said Hao Wenlei. "Not only that, underground construction has achieved a 'zero distance' between the water plant and residential areas, but also saved an additional 500-900 acres of land for health protection distance."

As for whether residents will be troubled by odor and noise from the water plant, Hao Wenlei further explained: "Our water plant adopts a fully enclosed design for each treatment unit and uses advanced biological composite deodorization technology to ensure that the odor emissions in the factory area meet the first level standard. At the same time, since all equipment is located underground, mechanical noise and vibration are greatly reduced, which has almost no impact on ground buildings and residents' lives. In fact, since the completion of the water plant, the surrounding commercial districts have gradually emerged, which has also driven the rise of surrounding housing prices and injected new vitality into economic development."

The outlet of the water plant caught the attention of the reporter, and a cup of earthy yellow liquid was placed on the table by the pool. "Director Hao, what is this cup of water?" "This is a sample of wastewater from the factory today." Then, Hao Wenlei twisted open a new bottle of pure water and poured it into another cup. At the same time, the staff of the water plant brought up a cup of freshly treated water from the outlet and placed it side by side with the first two cups. The reporter found that the treated water showed significant changes compared to the untreated sewage, and had almost no difference in sensory perception compared to pure water. "The main indicators of the effluent from Qingshan Water Plant have consistently reached surface level IV, making it the first fully submerged recycled water plant in China to achieve such high-quality effluent without using membrane technology," said Hao Wenlei proudly.

Comparison chart of influent, purified water, and effluent of Qingshan Reclaimed Water Plant. Photo by Wang Yuning

From underground to above ground, from Building 1 to Building 16

Where did the treated water go? The reporter learned that the recycling rate of the tail water from the Qingshan Reclaimed Water Plant has reached 100%, mainly used for the ecological landscape of the Nanming River, the surface active water landscape park, the construction of surrounding communities, municipal road watering, green maintenance, and other aspects, especially as a green energy source to provide centralized heating and cooling services for the ground office building.

The above ground landscape park of Qingshan Reclaimed Water Plant. Respondents provide pictures

On the ground level of the Qingshan Reclaimed Water Plant, there is a Guiyang Water Environment Science Popularization Hall that is open to the public for free. The venue utilizes innovative, visual, and three-dimensional technological means to showcase Guiyang's water culture, water resource situation, and cutting-edge water resource management and protection concepts to visitors. Every year, a large number of primary and secondary school students come to study, and through practical experience, they deeply understand the importance of water conservation.

"The students really enjoy the experience activities of simulating the water ecological environment observation area. Through VR glasses, the scene of blue waves rippling and birds playing on the sand table is vividly seen," said Huang Qi, a lecturer at the Guiyang Water Environment Science Popularization Museum. "In fact, these VR devices were equipped when we built the museum in 2016. After years of management and protection, the river section outside the museum has become clear and green, and such beautiful scenery no longer needs to be presented through virtual technology."

The Qingshan Reclaimed Water Plant is the first fully submerged reclaimed water plant in Guizhou Province, and it is also a microcosm of the environmental management of the Nanming River. Starting from "Qingshan", the treatment of sewage in Guiyang city has shifted from traditional "large-scale concentration and interception" to organic combination of "distributed planning" and "sinking type recycled water system", forming a distributed sinking recycled water ecosystem.

In 2017, the 7th Central Environmental Protection Inspection Group pointed out that "approximately 400000 tons of domestic sewage are discharged directly into Guiyang City every day, causing pollution to the water quality of rivers such as the Nanming River.". With the continuous improvement of the local government, water plants have taken root on the banks of the Nanming River. As of now, there are 34 recycled water plants in the Nanming River Basin, including 16 sinking sewage treatment plants.

This ecosystem not only cleverly solves the problems of heavy odor, high noise, and insufficient protection distance in traditional ground plants, but also saves about 1.5 billion yuan in pipeline construction and land acquisition investment, and saves 163.5 acres of construction land. Every year, high-quality tail water can also provide ecological replenishment of 450 million tons for the Nanming River, effectively solving the problem of insufficient ecological base flow in the Nanming River.

The ground of the reclaimed water plant is planned and constructed according to the plot, including ecological parks, sports venues, BRT hub stations, commercial complexes, and public utility buildings, to achieve efficient land use and demonstrate the organic combination of environmental governance and resource utilization.

Underground water plants save money and land, and efficiently utilize above ground space. The sewage treatment of Nanming River has taken an innovative path to ensure the long-term flow of clean water.