Escumador...

[Windrider]

Olá.

Movido pelos meus problemas com a transparência da água, tenho andado a espreitar o que posso acerca de filtragem.

Encontrei, entre outros, o seguintes texto, a propósito de escumadores:

 

"Why skimming?

In all marine systems wastes are continuously produced. Fishes secrete most of the food in form of ammonia/ammonium (= NHx), protein, amino acids and fibers. To prevent fish and other animals against toxic concentrations, these substances must be eliminated or changed into harmless material.

With biological filtration almost every substance may be converted into carbon dioxide, water, nitrate, phosphate and sulfate - mineralisation. But these products accumulate.

The foam of a skimmer shoud be very dark. So you can get out high amounts of organic waste.

With skimming or flotation proteins and some other substances are taken out of the system before the biological filtration works. The raising of nitrate and phosphate lowers with skimming. The water has lower concentrations of biological oxidizing substances. So the redox (ORP) is higher and the animals grow better.

If high concentrations of organic matter occur (death of an animal, too much feeding), a biological working trickling filter reacts very slowly. Bacteria must adapt to the new input. Especially nitrifying bacteria Nitrosomonas and Nitrobacter need a long time to react to the new concentration. The flotation process reacts automatically and prevent a rising of toxic products like NHx and nitrite.

Principle of flotation:

Proteins can adsorb at surfaces. In skimmers a large surface is produced by small air bubbles. At this surfaces the proteins couple. Additionally some other substance can adsorb at the proteins: dirt particles, death cells (bacteria, algae, fungus) and some metals. Therefore you have to dose trace elements - most of them are metals - regularly.

To create a flotation process you need small air bubbles (diameter <1 mm), a salinity of minimum 15‰ and not too much fat in the water.

Some factors affect the skimming:

The higher the temperature the higher the speed of the adsorption process.

The smaller the air bubbles the larger the surface and the power of the skimmer.

The higher the contact time between air and water the better the flotation process.

The lower the motion in the reaction (contact) tube the higher the adsorption force between air bubbles and proteins.

The lower the protein concentration in the water the higher the percentage of the skimming rate.

Supplement of ozone raises the adsorption forces of some substances and raises the skimming rate about 30%.

Additionally advantages of the flotation technique

With the skimming process you get much air into contact with water. During the day too much oxygen goes out of the water. At night you get oxygen into the water.

Carbon dioxide is an important gas for plants, algae and zooxanthellae. If additionally CO2 is not used the skimmer put this gas into the water and stabilizes indirectly the pH value. The longer the contact time between water and air the better the input of CO2.

A good skimmer is able to reduce the free bacteria concentration in the water. ... . Small particles (the bigger the skimmer the bigger the skimmable particles) are filtered out of the water and makes the water crystal clear.

Some variants of skimming technique

Same Way Principle: Water and air have the same way from the bottom to the top of the skimmer. The contact time is short and the skimmer is not effective.

Counter Flow Principle: Water and air have the same way but the other direction: water flows from the top to the bottom and air rises to the top of the skimmer. The contact time is longer and the skimmer is better.

Principle of Jülich Research Center: The aquarium water is enriched with air by air stones, injectors (venturi) or dispergators and is pumped into the skimmer at the bottom. Here is the biggest pressure in the system, so the interchange between the gases is the best. The water plus air ascend the contact tube and at its top the protein foam is created. The water stream carries a part of the air down into the outer tube. At the release conus the water streaming is lower and the air stops its motion. The bubbles are caught in the outer tube. The only comes out if other bubbles come into the tube. This principle realizes a very long contact time.

The foam is formed at the top of the skimmer. If the skimmer is operated correctly, the foam is thick and dark."

 

Sobretudo num aqua com discus, com elevada carga de poluição emergente da alimentaçãoe dos dejectos, parece a solução perfeita para resolver muitos dos problemas que resultam na deterioação da qualidade da água.

Ademais tende a maximizar a diluição de CO2 na água durante o dia e do O2 à noite, o que se revela também importante em aquas plantados.

Agora digam-me lá porque é que estou a ser profundamente estúpido por pensar nisto?

Porque devo estar, já que nunca vi nenhum aqua de água doce com um escumador.

E parece tão evidente que faz lá falta...

Abraços

PBL

[Joao Machado]

...porque a baixa "densidade" da Àgua doce "anula" (minimiza muito) o desejado efeito.

É só mandar dinheiro fora.

Se o problema é transparencia, boa filtragem mecanica, limpeza MUITO regular de esponjas, lãs, etc., e ....UV potente.

JPM