NL2004556C2

NL2004556C2 - Method for inhibiting and/or preventing the growth of algae in a lake or shallow water.

Info

Publication number: NL2004556C2
Application number: NL2004556A
Authority: NL
Inventors: Maarten Hoorn
Original assignee: Mfde B V
Priority date: 2010-04-15
Filing date: 2010-04-15
Publication date: 2011-10-18

Description

Method for inhibiting and/or preventing the growth of algae in a lake or shallow water

The invention relates to a method for inhibiting and/or preventing the growth of algae in a lake or shallow water, in particular blue algae, and for preventing the development of sludge of such algae.

5 It is known that algae, in particular blue algae as well as the sludge of such algae are a prime cause of turbidity of lakes and shallow waters. Generally speaking the prior art applies two distinct methods to fight such turbid waters, notably repeatedly dredging of the lake or shallow water to remove 10 the algae-sludge or digging a settling pit for the algae-sludge in the bottom of the lake or water. Another method consists of covering the sludgelayer on the bottom of the lake or shallow water, for instance with sand or geotextiles.

Dredging of the lake or shallow water provides a tempo-15 rary solution for the turbidity of the lake or shallow water.

The removal of algae-sludge which is intended with the dredging of the lake or water clearly has an initial effect, but deteriorates over time due to the growth, development and death of the remaining blue algae. A further disadvantage is that the removed 20 algae-sludge must be transported and dumped elsewhere which may affect the environment. This is also time and energy consuming, and very expensive.

Digging a settling pit usually provides a temporary solution for the turbidity of the lake or shallow water. In a num-25 ber of years the settling pit is filled up with algae-sludge and the settling pit is no longer effective. A further disadvantage is that it takes time after digging of the settling pit until the entire lake or shallow water is clear and free from turbidity. The clarity of the water has to develop from the vicinity 30 of the settling pit to the areas surrounding the settling pit. Still a further noticeable disadvantage is that it requires a lot of time, energy and costs to dig a settling pit of sufficient depth (notably more than 12 m depth), which depth is believed to be necessary to prevent that the algae-sludge that is 35 settled down in the settling pit can whirl up due to for instance streams in the lake or water. Other disadvantages are that the stability of the bottom of the lake or shallow water 2 may be effected, and that the pattern of streams in the lake or water may change due to the presence of the settling pit.

Covering the bottom of the shallow water or lake with inert materials, though a method carried out in a smaller number 5 of cases, is not expected to provide an enduring solution to the problem, because it does not act upon the mechanism of sludge production.

It is an object of the invention to provide an alternative solution to fight the turbidity of lakes and shallow wa-10 ters, which is effective, durable, and less costly than the existing solutions that are known from the prior art.

The method according to the invention is characterized by the feature that the bottom terrain of the lake or shallow water is provided with furrows or cuts in order to expose peat 15 that is present in the bottom to the water.

Surprisingly this method is effective and provides enduring results over time. The method is further very cost-effective in that it is not required to transport or remove soil from the bottom of the lake or water to elsewhere. This also 20 saves on energy. A further advantage is that the entire bottom of the lake or water can be provided with furrows or cuts, which makes the method immediately effective for the entire lake.

The inventor contemplates that the surprising effect of the method of the invention can be explained by the fact that 25 the exposed peat releases substances to the water that reduce the propagation of light at wavelengths in the range 550-625 nanometer. As is explained in the co-pending Dutch patent application 2004414 with the same inventor, this has an effect on the growth conditions of blue algae and in particular reduces the 30 propagation of light at wavelengths for which blue algae have a sensitivity which is not present in green algae. As is mentioned in that application it is the competitive advantage of blue algae over green algae that is a prime cause for turbidity of many lakes. By reducing or removing this competitive advantage the 35 influence of the blue algae may be reduced and turbidity of the lake may be prevented.

A favorable effect of the method of the invention is in particular that the substances that are released from the exposed peat are one or more of the group comprising humic acid, 40 fulvic acid, ulmic acid, lignin containing and other vegetable matter, and their complexes with iron and with other metals.

3

The mentioned substances are very effective for reducing the propagation of light at wavelengths in the range 550-625 nanometer. Furthermore the metals that are released can remain in solution when it forms complexes with the mentioned acids and 5 then be beneficially available for the living organisms in the ecological system of the lake or shallow water. Depending on the circumstances it is possible to promote this availability by additionally supplying metalchlorides to the lake or shallow water .

10 Is further remarked that it is desirable that the fur rows or cuts are provided in the bottom terrain of the lake or shallow water at least once a year, preferably spring, and optionally repeated the same year.

For making the furrows or cuts use can be made of de-15 vices such as ploughs that are known for working the soil of terrains that are used for raising crops and the like. It is however also possible to work with heavy anchors or other instruments that are suited to make furrows or cuts.

Claims

Method for braking and / or preventing the growth of algae in a lake or shallow water, in particular blue algae, and for preventing the development of sludge from such algae, characterized in that the bottom of the lake 5 or shallow water is provided with grooves or cuts to expose peat present in the soil to the water.

Method according to claim 1, characterized in that the grooves or cuts are provided in the bottom of the lake or water for releasing one or more substances from the exposed peat to the lake, for reducing the light pro- pagination at wavelengths for which blue algae have a higher sensitivity than green algae.

3. Method as claimed in claim 1 or 2, characterized in that one or more substances are added to the lake for reducing the light propagation at wavelengths in the range 550-625 nanometers.

4. Method as claimed in any of the foregoing claims, characterized in that the grooves or cuts are provided at least once a year, preferably in the spring, in the bottom of the lake or shallow water, and that this optionally becomes the same year repeated.

5. A method according to any one of the preceding claims, characterized in that the substances released from the exposed peat are one or more from the group comprising human acid, fulvic acid, ulmic acid, including lignin and other vegetation materials, and their complexes with iron and other metals.

6. A method according to any one of the preceding claims, characterized in that additional metal chlorides are added to the lake or shallow water. 2004556