Aeration for fish: Saturating Moscow’s water bodies with oxygen

January 28
Municipal services

Moscow’s water bodies freeze in the persistent sub-zero temperatures, and their aquatic inhabitants don’t get enough air. To support the ecosystem, Mosvodostok workers aerate local ponds and lakes and perform improvised “cardo-pulmonary resuscitation” (CPR) on fish, algae and microorganisms through ice-holes. Mosvodostok handles 250 ponds with an area of about 690 ha. Specialists have already drilled more than 1,300 ice-holes. This mos.ru story discusses the aeration process at Patriarshy Pond.

Oxygen for fish and algae

A lorry with a compressor unit is standing on the shore of Patriarshy Pond, and workers are dragging a hose towards the water body.

“There are two types of aeration, that is, natural and forced aeration. In the first case, we drill an ice-hole, and the air fills it. In the second case, we use a hose to blow oxygen into the pond. We use this method when the ice is over ten centimetres thick, and when the ice-hole freezes completely in 90 minutes,” Dmitry Kupriyenko, Deputy Head, Operational Hydro-Technical District No. 1 of Mosvodostok Effluent Control and Recovery Company, explained. As he talked, his coworker used a spiral drill to puncture the ice and also measured the ice-hole’s wall.

The pond is about 1.5 metres deep, and its underwater area shrinks if an ice layer reaches ten centimetres or more.

Dmitry Kupriyenko, Deputy Head, Operational Hydro-Technical District No. 1 of Movodostok Effluent Control and Recovery Company. Photo by Maxim Denisov, Mos.ru

Fish find it hard to breathe because the air cannot penetrate the thick layer of ice.

According to Mr Kupriyenko, the pond is home to silver carp, pikes and crucian carp. Human beings have played no part in their arrival in the lakes, instead ducks and other waterfowl carry fish spawn on their feet and feathers from lake to lake. “I have already counted five carp while diving in this pond. They are about ten years old, and we help them stay alive,” he laughed.

Each month, Mosvodostok specialists calculate the quantity of dissolved oxygen in the water bodies. They place retorts inside ice-holes and deliver the water samples to an environmental laboratory. The oxygen content should total four mg per one cubic decimetre. The fish need an “oxygen mask” in the event of lower content. The company’s specialists decide how often to carry out aeration, depending on how far the oxygen content has fallen below the required levels. During severe frosts, they have to repeat the procedure daily.

A grateful crucian carp

The workers open the lid of the aeration box covering the ice-hole. The wooden box prevents the ice-hole from freezing immediately; however, since yesterday, this ice-hole has frozen. The specialist uses a chisel to break the ice inside the box, places the ice fragments inside a net and throws them away. After that, he sticks a hose inside the ice-hole, and two coworkers turn on a flow of oxygen from a lorry. The water inside the ice-hole seethes just like in a Jacuzzi bath.

“The aeration procedure usually lasts about 30 minutes,” Mr Kupriyenko noted.

He treats fish as intelligent creatures, joking that a crucian carp will stick his head out of the water and thank the team and might well ask why there are ripples on the water, and Mr Kupriyenko will tell him that they did not have time to smooth them out.

After oxygen is pumped into the water, the workers close the box until the next day and leave for other water bodies. As a rule, one team usually aerates 15 ponds. Mr Kupriyenko and his coworkers have five water bodies to deal with, including Patriarshy Pond, Chistiye Prudy, Novodeevichy Prudy, Mandelshtam Park and Zaryadye.

“I like my job, although we have to work 12 hours a day. I have been working at Mosvodostok for over 15 years. We have a good team, and it is always great to work outdoors,” Mr Kupriyenko noted.

When it gets warm and the ice recedes, forced aeration is no longer necessary. Mr Kupriyenko and his coworkers will then work on other projects, such as diving. Once, he had to dive into Patriarshy Pond to retrieve some strange-looking plastic pedestals. Mosvodostok employees also have to cut back dead wood from the edges of the ponds and remove pollutants from the water. Right now, the team is off to save fish from oxygen starvation. “We will now move on and choose our next destination with minimal air levels,” Mr Kupriyenko said.

Source: mos.ru

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