From Practice

Experience in Restoring a Pond in the City Center

A. F. Ilyina and Z. P. Sokolova

From the Parasitology and Disinfection Departments of the Basin Sanitary and Epidemiological Station of the Lower Volga Waterway Health Department, Astrakhan

The restoration of ponds within city limits has received little attention in the literature. We therefore believe it worthwhile to share our experience in this field.

In a busy part of Astrakhan, near V. I. Lenin Square, there is an enclosed pond in the park of the passenger river terminal. It has an area of 7,410 m² and a depth of up to 3 m. The pond is connected to a canal running through the city. When the highway between the pond and the canal was widened, the pond became an enclosed body of stagnant water. The lack of water exchange caused green algae to proliferate, and within 3 years they covered 40% of the water surface in a layer 60 cm thick. The ornamental pond had become a stagnant swamp.

Because it was not immediately possible to establish a flow through the pond or periodic water exchange, we proposed restoring it by mechanically removing the algae, followed by treatment with chemicals. To speed up the mechanical cleaning, half the water was pumped out. The algae were then pulled ashore with nets, rakes, and mesh shovels, from boats and by workers wading in the pond. Nets were dragged along the bottom to bring all the algae to the surface for removal. The pond was then treated with copper sulfate at a rate of 4 g per 1 m³ of water.

The dying algae intensified the putrid odor in the pond. On the fourth day after the copper sulfate treatment, staff of the preventive disinfection department chlorinated the pond at a rate of 10 g of chlorinated lime per 1 m³ of water. The treated water was left in the pond for 7 days, after which fresh Volga water was added to bring the volume to 40,000 m³.

Chemical and bacteriological analyses showed that the water was similar in quality to Volga water. The pond remained free of algae throughout the summer.

Young fish of several species from the Astrakhan Nature Reserve were released into the pond. To date, not a single dead fish has been recorded.

Thus, the neglected pond was restored by mechanical cleaning followed by chemical treatment. The work was carried out by members of the public at little expense.

Received November 24, 1959.