Crayfish have been “working” in Vodokanal since December 2005.

Biomonitoring quality control systems are introduced at all WTPs in the city and the nearest suburbs. Their main assignment is to monitor the toxic level of St. Petersburg drinking water source - the Neva water. Several representatives of the indigenous narrow-clawed crayfish, inhabiting in the Neva and the Neva Bay, live in the aquariums at every water intake of Vodokanal of St. Petersburg.

Why do we need crayfish?

Besides laboratories such “employees” control water from the Neva before it goes to the WTPs and becomes tap water. Process specialists need to know whether the water coming to WTPs is polluted with toxic substances and with such concentration which can not ne removed from water by the existing technologies and equipment. For the economical reasons the existing physical-chemical analysis methods may provide control only for the limited list of water pollutants and take much time, but the process specialists need to get the signal that such kind of water came to the water intake as soon as possible. Only living water organisms, in particular crayfish which are very sensitive to environment pollution, can “notify” of danger promptly and in real time mode.

How do they work?

A fiber-optic sensor is attached to the crust of the crayfish in aquarium, it gives opportunity to register the crayfish’s heart beating imperceptibly for an animal during the long period of time. The treated results of the crayfish heart rate and stress-index (as a “traffic lights” system: red, yellow and green light signals) are continuously displayed on the computer. A standard heart rate of the unworried crayfish (green light) varies from 30 till 60 times a minute depending on the temperature and the stress index is close to zero. In case of a danger the heart beat frequency is increased by not less than 50% and the stress index is raising up to several thousand. Crayfish react on toxic substances coming into water within 1.5-2 minutes (together with data treatment time). Their heart rate becomes more rapid, instruments send an alarm signal (red signal on the monitor of the shift operator) and water samples are taken automatically for further detailed laboratory analysis with chemical and biological methods, then all WTP divisions are notified.

Fortunately, no such situations have occurred since crayfish started working and the specialists of St. Petersburg Environmental Safety Research Center of the Russian Academy of Sciences, who developed this water quality monitoring method, have such “high stress indicators” only during daily preventive test examinations of crayfish.

Special requirements

In addition to the biomonitoring station, there is a farm at the Main WTP which principal task is to breed own crayfish adopted to production noise and to people. The animals used to be with people, get accustomed to fluctuation of the Neva water quality, to the pumping station noise. Crayfish can react to irritants not related to water pollution, for example, to noise of the equipment. In order to prevent false system actuation (false in terms of toxicological hazard of water) the scientists created special analytical station which measures a range of water parameters – alkalinity, temperature, turbidity as well as is equipped with noise and vibration sensors. If equipment records vibration, the control room will not get an alarm signal because sensors records a moment when intensification of a heart beat coincides with a noise effect and cut it off as not related to the toxic hazard.

Absolutely ordinary crayfish serve in Vodokanal. These animals are well studied in terms of physiology and toxicology. However, to be employed in Vodokanal crayfish pass through proper biochemical and physiological examination. Only males at the age of 3-5 work, two crayfish per a “shift” (for more accurate readings), three working days and six days off. A service period is one year. The thing is that for the reason of their physiology crayfish have to winter and go into hibernation. Crayfish is getting weak without this natural sleeping. And only healthy individuals in good condition are permitted to be on duty.

Additional control

In order to have accurate reaction to water quality changing fish work together with crayfish. A video camera constantly fixes their movement. If fish feel bad, they will stop moving and will go belly up or go down to the bottom. If crayfish begin to worry, the specialists will start taking measures. This duplication is for the good of humans. The scientists say that it would be good to equip the existing biomonotoring stations with the “mussel-monitor” system. River mussels are also good indicators for the quality of water they live. In addition to heart rate increasing they close their shells in unfavorable conditions.