By Xinyi Li, EDITOR

On April 2, Chongqing Three Gorges Water Co., Ltd. held Green Open Day. In recent years, Chongqing has successively upgraded and modified its urban sewage treatment plants, and the effluent quality of sewage treatment plants in the main urban areas, districts, and counties of Chongqing has reached Standard A, and Level I from Standard B.  Level I is based on the national emission standard.

The water sample of the sewage treatment plant of Jiuqu River

The differences between Standard A, Level I and Standard B, Level I?

On-site at Green Open Day, representatives of the public carefully observed the water samples in all links of sewage treatment. Distinguished only with the naked eye, there are still some fine suspended matter and impurities in the water sample of Standard B, Level I, but the water sample of Standard A, Level I is clear and transparent with no impurities, and even without any significant differences with the tap water.

According to the staff of the Technical Section of Chongqing Three Gorges Water Co., Ltd., in terms of organic pollutants, suspended matter, nitrogen and phosphorus, Escherichia Coli and other related indicators in sewage treatment, the effluent quality requirements of Standard A, Level I are obviously stricter than Standard B, Level I. According to the classification requirements and the pollutant receiving capacity of natural water, some sewage treatment plants with effluent discharged into major river basins are required to reach Standard A, Level I, which is the standard for regions with strict control of water environment. However, sewage treatment plants in main urban areas, districts, and counties of Chongqing have reached this standard.

What have they done for meeting these standard requirements?

In the sewage treatment plant of Jiuqu River, there are newly added V-type filters under the upgrading and modification project, and the sewage will finally enter the V-type filter through processes such as the grille, the primary sedimentation, the biochemical reaction pool, and the secondary sedimentation. At the bottom of the V-type filter, the over-one-meter-thick filter materials including the quartz sand will filter the sewage layer by layer from the top to the bottom to remove most of the suspended impurities and some colloidal substances visible to the naked eyes, so as to further improve the purification effect.

All the sewage treatment plants of the Chongqing Three Gorges Water Co., Ltd. and its parent company Chongqing Water Group have now adopted technologies and facilities to upgrade emission standards. In addition to V-type filters, they have also built cloth filters and high-density sedimentation tanks. After the improvement of water quality, the effluent can serve as the recycling water of sewage treatment plants, and services for municipal greening and road cleaning. Moreover, the dehydrated sludge can play the roles of garden nutrient soil and building materials, realizing the reuse of resources.