Innovation in Progress: CCTV reveals the "water cube" of underground pollution control

On November 20 and 21, 2023, CCTV10's program Innovation in Progressaired a two-episode series titled Water Cube of Underground Pollution Control, providing an in-depth look at the green technological capabilities of the China Water Environment Group's distributed sinking reclaimed water ecological system.

The technology and model of the distributed sinking reclaimed water ecological system originated and were developed during the governance process of the Nanming River in Guiyang. The Nanming River had suffered severe pollution for decades, falling into a repeated cycle of treatment and pollution. Innovatively, the China Water Environment Group developed the distributed sinking reclaimed water ecological system, situating water plants underground to process sewage near its source. This green and sustainable approach conserves the land area occupied by water plants, significantly improves water purification efficiency, and achieves 100% reuse of reclaimed water. It provides an efficient solution for the ecological governance of rivers in China.

  Lei Yueqin, an 86-year-old environmental volunteer in Guiyang, has spent the past 39 years documenting the changes along the Nanming River through photographs. A decade ago, the water of the Nanming River had become turbid, with decomposed and putrefied garbage accumulating like mountains on the water surface, providing a breeding ground for pests. Using hand-drawn maps, Lei Yueqin marked key pollution sources along the Nanming River.

"I use symbols and signs to represent severe pollution areas along the Nanming River, indicating large factories causing this pollution and many small workshops on both sides of the river. By looking at it, you can tell where the pollution is severe. In the 1990s, the water discharged by factories was black, with the presence of substances like oil."

Starting from the 1970s, industrial enterprises and shantytowns on both sides of the river continuously discharged industrial wastewater and domestic sewage into the Nanming River. By the 1990s, the cumulative pollution exceeded the carrying capacity of the Nanming River. This not only caused damage to the water body but also led to a massive death of aquatic life in the Nanming River. In severely polluted sections, the variety of fish species was reduced by nearly 80%, seriously disrupting the natural aquatic ecosystem.

The pressing issue at hand is how to rescue the "mother river". Governing the Nanming River poses an exceedingly complex technical challenge for Guiyang. Guiyang is located on the Yunnan-Guizhou Plateau, characterized by typical karst topography with loose geological formations. Surface water easily permeates into the ground. This further complicates the already scarce land resources for Guiyang, making it challenging to select suitable locations for building sewage treatment plants. Long-distance sewage transport entails risks of leakage and pollution.

Through meticulous research conducted by the government, the group, and experts, an innovative solution emerged: embedding distributed sewage treatment plants into the city, treating sewage on-site, and reusing it nearby. Reclaimed water is then utilized as ecological replenishment for the Nanming River.

  Throughout the practical implementation of the distributed sinking reclaimed water ecological system, the China Water Environment Group continuously innovated in both concepts and technologies, enhancing processing efficiency, achieving faster results, and reducing investments. The Nanming River project is the group's pioneering initiative in China to tackle key technical challenges related to sinking urban reclaimed water plants, resulting in multiple core technological achievements.

The research and development team, after overcoming numerous challenges over thousands of hours, designed a novel sludge biofilm capable of aggregating a large number of nitrifying bacteria. This film allows for the growth of more microorganisms, efficiently consuming pollutants in the wastewater and improving water quality.

"By using the technology of the biofilm to enhance the efficiency of the entire system, strengthening high-efficiency and land-saving biochemical technology, we've reduced the land footprint by more than 40% compared to traditional processes," explained Dr. Cao Xiaoxin, General Manager of the Technology Innovation Department at the Engineering Technology Center.

Simultaneously, the distributed sinking reclaimed water ecological system achieves comprehensive utilization of green energy. Through water source heat pumps, it harnesses the energy from underground wastewater to provide heating and cooling for the water plant's office area, science and education centers, and surrounding communities, serving an area exceeding 500,000 square meters.

  After systematic management, the once foul-smelling and murky river water has transformed into clear, bottom-visible water teeming with fish and shrimp. At present, distributed sinking reclaimed water plants are present in 22 provinces and cities, including Beijing and Shanghai, contributing to the ecological civilization construction of urban water resources and water environments. Looking ahead, Chinese technological innovations represented by the distributed sinking reclaimed water ecological system will continually enhance the living environment, meet the growing aspirations for a better life, and realize the sustainable development of resources and the environment.