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

Snails – new Vodokanal ‘employees’

Australian Red Claw Crayfish work at SWWTP

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.

Snails – new Vodokanal ‘employees’

Starting 2011, at South-West Wastewater Treatment Plant giant African snails (Ahatina gastropods) began to work. That is a new bioelectronic monitoring system implemented by Vodokanal.

Why snails?

The task of snails – to “monitor” the air condition in the area of Sludge Incineration Plant at South-West Wastewater Treatment Plant (SWTP). Snails breathe air mixed with smoke that goes out from the plant pipe. Fibre optic heartbeating and behavior (motion activity) sensors are fixed on their shells, thanks to which, using a special software, the system automatically appraises the functional status of animals, i.e. their “well-being”.

Smoke cleaning system at Sludge Incineration Plant (SIP) at South-West Wastewater Treatment Plant is the most modern. It fully meets the requirements of Russian regulatory documents and European Commission Directive, which regulates the combustion conditions and requirements for emissions of pollutants into the air from waste incineration units. A special analytical unit monitors the combustion products at SIP. A multiple protection system is provided, and in case of emergency the modern equipment must register a major emission.

However, compounds (combustion products) can be present in the air in slightest doses. It is unprofitable to install special sensors on each of them and the compound concentration is so low that not every device can register them. To control chronic air toxicity, scientists from Saint-Petersburg RAS Research Centre for Environmental Safety proposed to use shellfish. As a general indicator that reacts to all having universal toxicity towards animals, snails were invited “to work”, which have lungs and like people breathe air. They also have a shell, on which sensors can be fixed not affecting the process of their life. A big plus is that these animals are active enough.

During the first year of system operation specialists will monitor six snails – while three of them really get the air mixed with that one going out from the plant pipe, and three more breathe usual air. It is necessary to compare behavior and heartbreathing of snails from the two groups.

What is the difference from the biomonitoring system when river crayfish monitor the quality of water from the Neva-river?

Crayfish react to the sharp condition change in the environment, and the established snail-based system of continuous control of air pollution levels on the border of the sanitary protection zone at the plant can react not only to sudden and significant changes in the air. It can also control the accumulation of the possible negative impact on the health of the “indicator” shellfish group. Such accumulation is related to the chronic toxic impact of pollutants released with flue gases – even at relatively low concentrations of such substances. In other words, gradual accumulation of hazardous substances in the animals’ organism, as they breathe polluted air, will affect the snail well-being. The distinction of this control system is an ability to identify so called synergistic effects when the total negative impact of pollutants on the biological beings’ health can significantly exceed the total negative impact of separate pollutants. The system that controls only physical and chemical air characteristics is not able to register this impact.

How is the snail “work place” organized?

A snail sits on the ball that floats on the water surface. Sensors that record heartbeating and motion activity are fixed on the animal shell. A feedbox is set in front of the ball; food is given approximately once a week. The snails are fed with lettuce leaves, cucumbers; sometimes they get delicacies - water melon. All the snails are placed in an open container (box), where a mixture of air and treated smoke from SIP is supplied. It is important to note, that the snails don't live directly in the pipe and don’t breathe its “exhausts” – for them the smoke is diluted 1000 to 10000 times with clean air. Thus, approximately the same concentration is achieved as on the border of the sanitary protection zone of the plant.

The bioelectronic system developed by scientists from Saint-Petersburg RAS Research Centre for Environmental Safety (RAS RCES) automatically monitors the functional status of the snails, mainly the heartbeating rate and activity within the diurnal cycle. The heartbeating monitoring is made with using photoplethysmogram, i.e. dynamic of light scattering is optically observed – it varies in rhythm with the heartbeating. The activity monitoring means a study of the current activity and creation of special conditions. At a certain time of the day the moistening mode is turned off for one to three hours and air blowers are turned on, which blow dry air through the system. The animals don’t like the drying out at all – they hide in their shells. The system records the change in the heart rate (HR) to determine how an animal can change HR from maximum to minimum. During the “airing" period HR and mechanics of shell lowering and lifting are observed. If in course of time all the snails feel worse – it will be clear after measuring (other HR and motion activity values) – the system will automatically register it, and then specialists will start to find out the reasons.

Favorable working conditions

People from RAS RCES and OOO “SIC “ECOCONTUR” (Saint-Petersburg) had to work hard to create the most favorable conditions for the snails. Firstly, it was important to fix the sensor on the shell in such a way that the snail shouldn’t feel any pressure or discomfort. The constructed fastening mechanism reminds the mechanism of a door butt – a deviation to the left and right is rigidly fixed, and there are no vertical efforts that keep the shell. Secondly, thanks to a ball there is no rolling resistance and the snail can crawl. Another important condition of living the snail in the wild, which scientist had to ensure here - intensive moistening. Meanwhile the animals are moistened using drop bottle system – water drips on them from above.

Australian Red Claw Crayfish work at SWWTP

New “employees” have appeared at the South-West Wastewater Treatment Plant (SWWTP) of Vodokanal of St.Petersburg in the summer of 2011. Six Australian red claw crayfish (Red Claw Cherax Quadricarinatus) live in aquaria via which the treated effluent passes by. Scientists and technologists control the SWWTP effluent quality before the discharge into the Neva bay on the basis of animals’ palpitation and well-being.

Bioelectronic system of SWWTP treated effluent toxic security control is the new product of St.Petersburg scientists. Vodokanal of St.Petersburg actively cooperates with St.Petersburg Research Centre for Ecological Safety of RAS. If the water quality deteriorates, sensitive crayfish will feel it immediately – scientists will observe not only the change of its behavior, but they will also receive the signal from special optical fiber sensor that is attached to the crust. The sensor performs online registration of the animal cardiac activity. If the cardiac rhythm of all six crayfish will increase simultaneously by 1.5 – 2 times, the red alarm signal of the “light signal” system will light in the operators control room. Herewith specialists of the wastewater treatment plant will act in accordance with specific regulations – to find out and eliminate causes of the event.

Wastewater treatment quality is daily monitored by special devices and the laboratory. Nevertheless, owing to the bioelectronic monitoring system it is possible to trace animals' reactions to evaluate the synergism of simultaneous effect of multiple factors, influencing the water – the crayfish's habitat. For example, one device measures phosphates in the wastewater, and another device registers the amount of nitrates. But only the indicator-animal organism can simultaneously assess the aggregate of all the quality characteristics of the water, where it lives.

At the waterworks the Neva water quality is “assessed” by a different kind of crayfish — narrow-clawed crayfish. The optimal water temperature for these crayfish must not exceed 22î – 23î Ñ. Because in summer the wastewater temperature can reach 26î – 30î Ñ, it was necessary to find a more thermophilic species of crayfish to be used as biological indicators of the treated effluent's quality at the South-West WWTP. Having considered a number of characteristics, the choice was made in favor of Red Claw Cherax Quadricarinatus (red claw crayfish). This species demonstrates resistance to temperature range between 18î and 31î Ñ. Its extreme survival temperature range is quite broad: from 10î to 36î Ñ. The red claw crayfish originally comes from the north-western and northern tropical Australia. Its distinctive feature is blue-green color with yellow spots, typical of tropical species. A distinctive feature of male species is a visible red spot on the belly. The average length of male species is 18 cm, of female species is 15 cm. Their life span is 4 - 5 years, during which they reach the length of 40 cm and the weight of 650 g in wild nature. They reach sexual maturity at 7 months old, weighing 110-120 g.

Vodokanal employs male species of Red Claw Cherax Quadricarinatus, which are assumed by researchers as more stable in their behavior than female species. Twice a week the crayfish is fed with bloodworms, prawn food, and some species of fresh-water macro vegetation.

It is worth mentioning that the Australian crayfish's job is seasonal. When wastewater temperature drops, they are replaced by narrow-clawed crayfish, which is aboriginal to central Russia. For them cool water is the most habitual environment.