Fish work as "water monitors" to safeguard Beijing's water quality

The water diverted from Hebei to Beijing was recently cleaned at the northern floodgate of Tuancheng Lake on Beijing-Miyun Water Diversion Channel near the Summer Palace. The giant filter was tangled with floating debris like leaves and branches. Crystal clear water slowly flowed out at a speed of 13 cubic meters per second, going on to enter tens of thousands of Beijing households via Beijing No. 9 Water Treatment Plant and others.

Small fish in laboratory water tanks protect  Beijing's water resources

Beijing-Miyun Water Diversion Channel

Next to the giant filter stood a small house that could easily be neglected by its appearance. Inside was a machine resembling an ATM, called a “biological early-warning system for water safety.” “This machine is far from ordinary. There are more than 20 lively small fish inside. They are ‘water quality monitors,’ on duty around the clock to safeguard Beijing’s water resources,” said Professor Wang Zijian, the man responsible for the national lab for environmental water quality in the Research Center for Eco-Environmental Sciences (RCEES) under the Chinese Academy of Sciences.

Warnings will be issued if water quality changes and the small fish behave abnormally

One day in early July, Professor Wang led his students to the northern floodgate of Tuancheng Lake on Beijing-Miyun Water Diversion Channel. They need to replace the small fish used for monitoring water quality every month.

The “biological early-warning system for water safety" resembles an ATM. On top is a display panel showing dynamic graphics, like an electrocardiogram, with different indicators showing “swimming,” “swaying,” “food intake” and “fin movement.” Eight test tubes are installed in the middle, with three to four small fish in each tube. These fish are just babies, about 2 to 3 centimeters long, and translucently steel-gray in color. Connected with the test tubes are two delicate instruments installed under the machine. There are also water pipes connected to the sources under detection.

While teaching students how to replace the fish, Wang explained that the fish are called Japanese medaka. As they are sensitive by nature, a change in water quality causes abnormal behavior, such as erratic swimming and changes in the speed of gill movement. If this happens the electric field in the test tubes cuts off automatically, triggering an alarm. The instrument is also equipped with a GPS transmission system. If the water quality is found to be unusual, the alarm is directly transmitted to a detection computer and the mobile phones of the staff, which is extremely convenient.