An Olszewski tube is a pipe designed to bring oxygen-poor water from the bottom of a lake to the top. This tube was first proposed by a Polish

limnologist Limnology ( ; from Greek λίμνη, ''limne'', "lake" and λόγος, ''logos'', "knowledge") is the study of inland aquatic ecosystems. The study of limnology includes aspects of the biological, chemical, physical, and geological characterist ...

named Przemysław Olszewski in 1961 and helps combat the negative effects of

eutrophication Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...

, high nutrient content, in lakes. The basic concept behind the Olszewski tube is the reduction of nutrient concentration and destratification; the more specific goal is hypolimnetic withdrawal.

Eutrophication

When nutrients build up in a lake, eutrophication occurs, and this generally occurs in the top layer of a lake. The nutrients come both naturally and artificially and usually contain

phosphates In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...

. The artificial nutrients can come from sewage and fertilizers, from

agricultural runoff Agricultural pollution refers to biotic and abiotic byproducts of farming practices that result in contamination or degradation of the environment and surrounding ecosystems, and/or cause injury to humans and their economic interests. The pol ...

Phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

from the phosphates causes algae to grow rapidly and spread throughout the top layer of the lake. Algal blooms have negative effects on both the

aesthetics Aesthetics, or esthetics, is a branch of philosophy that deals with the nature of beauty and taste, as well as the philosophy of art (its own area of philosophy that comes out of aesthetics). It examines aesthetic values, often expressed t ...

and the

ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...

of the lake. Aesthetically, the lake is not pleasing because it is covered with algae. Ecologically, eutrophication causes organisms in the lake to die because the algae deplete the

dissolved oxygen Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium at the given temperature. It ca ...

in the lake.

Design

At the most simple level, the Olszewski tube is a pipe that spans from the bottom, hypolimnetic layer of the lake to the outlet. The outlet part of the pipe is installed under lake level in order for the device to act as a siphon. Once warm water flows in the lake at the surface, it forces the cold anoxic water of the hypolimnetic layer through and up the tube. This oxygen-poor water is then brought to the top of the lake where the eutrophication occurs. This eventually helps the lake as a whole because the bottom of the lake will have more dissolved oxygen and the top of the lake will have less eutrophication.

Implementations

The first implementation of the Olszewski tube was attempted at Lake Kortowo in

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populou ...

and this led to oligotrophication, reduction of nutrient cycling. This tube has shown the most promise in a 3.9 meter deep eutrophic lake in Switzerland because the phosphorus and

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

levels in the summer drastically decreased, oxygen levels increased, and the amount of cyanobacteria decreased from 152 grams per square meter to 41 grams per square meter. It has also been reported by a scientist named Bjork that there have been successes with the Olszewski tube in European lakes. Other limnologists like Pechlaner and Gachter have reported successes in small lakes where the total phosphorus decreased, transparency of water increased, and less algae was present.

Complications

Some complications that can arise with the use of an Olszewski tube include disruption of the

thermocline A thermocline (also known as the thermal layer or the metalimnion in lakes) is a thin but distinct layer in a large body of fluid (e.g. water, as in an ocean or lake; or air, e.g. an atmosphere) in which temperature changes more drastically with ...

and excessive water loss. The thermocline separates the upper layer of water that is mixed temperatures with the deeper, cooler water. If the thermocline is disrupted, it could alter the ecology of the lake, potentially making it uninhabitable. Another complication is that the installation must be a long-term process. Short-term uses of Olszewski tubes have largely failed because it takes some time for the anoxic condition of the hypolimnetic layer to increase in dissolved oxygen. Also, it must be a slow process in order to avoid disrupting the thermocline in a lake. If the Olszewski tube is operated slowly enough, the rate of water going in and going out will be fairly constant causing the thermocline to stay intact.

Cost

One advantage to hypolimnetic withdrawal is that it is relatively inexpensive to install an Olszewski tube or any similar device. Along with low initial cost, it also has a relatively low annual maintenance cost. The following are four systems installed in the United States (2002), their area in

hectares The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is a ...

, the rate of flow in cube-meters per minute, and their initial installation costs in US dollars: * Lake Ballinger 41 ha
3.4 m³/min
$420,000 * Lake Waramaug 287 ha
6.3 m³/min
$62,000 * Devil's Lake 151 ha
9.1 m³/min
$310,000 * Pine Lake 412 ha
5.3 m³/min
$282,000

Other Techniques

Aside from using an Olszewski tube and hypolimnetic withdrawal, there are other techniques implemented to achieve the same goals as an Olszewski tube. These include increasing dissolved oxygen, reducing nutrient concentration, and lessening the amount of algae and unwanted biomass in lakes. * Sediment oxidation is the artificial

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

of the top 15 to 20 centimeters of anaerobic lake sediment. This technique reduces internal nutrient release through a series of

chemical reactions A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking ...

starting with iron(III) chloride. After these reactions, the concentrations of phosphorus and ammonium (another nutrient found in lakes) decrease and the demand for oxygen gas in reduced as well. This technique is still not fully developed yet but can mirror the effects of the Olszewski tube. *

Biological control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also i ...

methods are the most promising techniques because they do the least harm to the ecosystem. These methods introduce a particular species (e.g. fish, bacteria, etc.) into a lake as a solution to a current problem. The introduction of a certain type of bacteria can help decrease nutrients. In turn the algae will not spread and the oxygen in the lake will stay in high dissolved concentrations. *

Hypolimnetic aeration Via deep water aeration or hypolimnetic aeration, the oxygen demand of deep water is provided by oxygen from the atmosphere without destroying the lake’s natural stratification. Thus the deep water becomes aerobic, the dissolving of phosphates i ...

is another technique in which oxygen is added to the lake. This helps increase the concentration of dissolved oxygen in the lake as well as bring down the levels of phosphorus. While the results of this technique are similar to those of the Olszewski tube, hypolimnetic aeration differs in that it uses compressed air to move the water rather than a siphoning effect.

References

{{Reflist Limnology Environmental engineering