Shevtsova, L. V. 1994.  Control Strategy of Biofouling of Hydrotechnical Constructions by Dreissena (Dreissena polymorpha Pall., D. bugensis Andr.)  Institute of Hydrobiology Ukranian Academy of Sciences.

Proceedings of The Fourth International Zebra Mussel Conference, Madison, Wisconsin, March 1994

Control Strategy of Biofouling of Hydrotechnical Constructions by Dreissena (Dreissena polymorpha Pall., D. bugensis Andr.)

During recent decades the geographical distribution of the bivalve mussels Dreissena polymorpha and in particular D. bugensis has increased. It is known that D. polymorha is widespread in European reservoirs, and since the 1970s a northward expansion of this species has been observed. Currently, D. bugensis dominates in all reservoirs of the Dnieper cascade (Pligin, 1984). It has occupied canals in the southern Ukraine and reservoirs connected to the Dnieper River. In 1987 D. bugensis was found in the Seversky Donets river (Azov Sea watershed), where it had penetrated from the Dnieperdzerzhinskoye reservoir, located in the river Dnieper, through the canal Dnieper-Donbass. In 1989-1991 D. bugensis became abundant in Dniester reservoir, constructed in the middle current of the Dniester River. This species has also appeared in the Laurentian Great Lakes in America (Rosenberg G., Ludyanskiy M., 1993).

Both Dreissena species, despite some biological and ecological differences, have similar functional features. Being active filterers-sedimenters, they diminish the anthropogenic load to reservoirs by increasing the sedimentation of particulate matter, including organic substances and heavy metals, thereby improving water quality.

At the same time Dreissena's presence in reservoirs causes a complex of problems related to their tendency to colonize hard substrates used in hydrotechnical constructions. The most significant problems are related to the colonization of water pipelines. Dreissena fouling leads to a narrowing of the inner diameter of pipelines, resulting in a decrease in water delivery rate. As a result of such biofouling electric energy expenses required to maintain standard volumes of water delivery are increased.

Disturbances caused by Dreissena can be faced by pump stations and different enterprises using nonpurified water. Under the impact of biofouling the deterioration of hydrotechnical construction materials is speeded up. The corrosion rate of unprotected steel structures under the influence of biofouling can increase 4 times, and the structure of concrete can also be changed. Following a sharp decrease of the water level in reservoirs mass dieoffs of mussels can occur, leading to a deterioration of water quality and the appearance of strong odors..

Numerous studies have been devoted to Dreissena's biology and methods of preventing biofouling. I propose a general strategy to deal with Dreissena fouling in hydrotechnical constructions (Table 1).

An example of such a strategy can be found in works carried out during the construction of water transport pipelines from the newly-built Krasnopavlovskoye reservoir in the canal Dnieper-Donbass (Table 2) to the City of Charkov, and the construction of pipelines for water-use in small settlements on the Dneister River.

It was known that in Dnieperdzerzhinskoye resevoir, leading to the DnieperDonbass Canal, and in the canal itself, significant populations of D. bugensis and D. polymorpha existed. Experts predicted that Dreissena would colonize all hard substrates in Krasnopavlovskoye Reservoir. Mollusk densities were anticipated to reach 100,000/m²; the biomass was expected to reach 2000 g/m². Serious pipeline fouling was expected.

Data on reproductive timing, veliger dynamics, and growth rates obtained in similar water bodies were applied to this situation. In this reservoir Dreissena's reproduction was expected to take place within the time period of April-October and within a temperature range of 12-23 °C (Table 3). Expected veliger dynamics (with three peaks) and growth rates of newly settled mussels were expected to correspond to growth curves shown in Figures 1 and 2.

Studies of pipeline technical characteristics and water properties allowed us to make recommendations. These included constructing water intakes at a depth of 12-15 m, where Dreissena larvae are less abundant. We recommended that initial water chlorination levels range from 4-6 mg/1, so that the output water chlorination level would not be less than 0.5 mg/1. On the basis of biological and technical parameters chemical control programs must be implemented annually in June, August and October for 7-8 days.

These recommendations were included in the technical project design. Water pipelines were completed in 1988-1989, and fouling has not been observed.

For solving the problem of water intake protection in the Dniester River periodic chlorination was recommended, but the pipeline water purification system required technological modification. In that case chlorination of the water pipeline should not be conducted more than 2 times a year using a significantly larger dose of chlorine (10-17 mg/1) to reach the final concentration of 5 mg/1 when the water gets to the water treatment plant. In this case the pipeline treatment has to occur over a 24-hour period. The use of mobile chlorinators has been recommended.

Another problem is the removal of accumulated masses of fouled Dreissena. During the 1960s and 1970s in the Ukraine a large network of underground irrigation pipelines was built without any protection from biofouling. As a result unpredictable fouling has occurred, decreasing the water-carrying capacity of these systems, and leading to the blockage of irrigation devices.

Several control methods were unacceptable due to the toxicity of many ingredients to soil and agricultural crops. In addition, during the irrigation season it was impossible to turn off separate plots. Therefore an immediate need developed for controlling Dreissena in irrigation systems. Such a method needed to remove Dreissena without being toxic to the plants, without breaking the regime of irrigation for agricultural crops, and it had to be available for organizations serving irrigation systems.

In laboratory conditions the toxic action of different solutions of mineral fertilizers on Dreissena was tested. Finally, ammonia nitrate in a concentration of 300-600 mg/1 was selected as an effective control method. This method of Dreissena control in irrigation systems has been patented. In Table 4 data from experimental systems, using this new control method, is shown. At the present time this technique is widely applied in Ukraine irrigation systems. Controlling Dreissena's fouling in water systems, if not planned for ahead of time, presents many difficulties and requires additional expenses. Therefore, it is important to develop predictive techniques and practical control recommendations at the planning stage of hydrotechnical constructions.

Entire Paper
Keywords: Chemical_control, Industry, Prevention, Zebra_mussel
Product Type: Publication, Proceedings
User Type: Industrial_and_Municipal