The Biotec-Filter

How the Filter Works

The Biotec Filter was developed specially for cleaning garden ponds. It adds oxygen to the water and guarantees intensive biological filtering in 24-hour-a-day operation. If specially cultivated (BIO-KICK) bacteria are added, the filtering efficiency is optimized and the running-in period shortened. The filter converts nutrients into a solidified bacterial biomass which is then easily flushed away when the individual filter modules are washed out.

The Biotec Filter consists of various chambers, through which the pond water is pumped. Figure 8 (page 14) is a simplified representation of how the water flows through the filter. The various stages in the filtering process are as follows:

  1. The polluted pond water is pumped into the filter.
  2. Some of the untreated water is diverted via a bypass into the UVC area, where algae and pathogens are destroyed by ultraviolet rays.
  3. The water is enriched with oxygen by means of spray aeration at the inflow. A high degree of oxygenation is essential for optimum biological filtering.
  4. The water now passes into the blue zone. Here coarse particles are mechanically filtered out. The remaining particles are oxidized, and first-order nitrification (i.e., the conversion of ammonium or ammonia into nitrite) takes place. A very limited measure of second-order nitrification (the breaking down of the nitrite into nitrate) can also take place in this zone.
  5. The distinctive feature of the special bio elements is the enormous surface area they provide for very small organisms and micro-organisms to colonize on. The bacteria lawns which forms on these surfaces of the bio elements not only activate the mineralization process, they also bring about second-order nitrification (i.e., they break down nitrite into nitrate).
  6. Filter starters (BIO-KICK) and other biological additives (e.g., BIO-ACCU or BIO-STABILIZER) can be used in the Biotec-Plus-Zone to improve and speed up filtration.
  7. Mechanical fine filtration, mineralization, and second-order nitrification (i.e., the conversion of nitrite into nitrate) all take place in the red zone.
  8. Since little oxygen is present in the denitrification zone, conditions are such that excess nitrate is converted into gaseous nitrogen, which is not available to plants and algae.
  9. The treated, clear water passes through the filter and into the garden pond. Since the amount of oxygen in the water is now much reduced, oxygen enrichment at the outlet end by means of, for example, a watercourse or waterfall, is essential.


Zones 4, 5, 7 and 8 have extremely large surface areas and are therefore excellent settlement locations for micro-organisms, which will flourish in the type of environment they provide. At the same time, nutrients are converted into solid biomass in these zones. The dirt tank in the filter is removable, so the biomass can easily be disposed of after it has been filtered out of the water. It should be remembered that although biomass is a nuisance in ponds, it makes an excellent fertilizer.




The Importance of Flow-Through Speed

The performance of the micro-organisms as filtration agents is affected by the flow-through speed of the polluted pond water. For optimum filtering efficiency a pump with a flow regulator should be used with the Biotec-Filter System. For severely polluted ponds stocked with fish a powerful pump will be required to ensure that the water is adequately oxygenated and that high rates of decomposition and nitrification are achieved.

In ponds with low levels of pollution, or at times when fish are not being fed, a slower flow-through speed may be selected, since although the rate of decomposition will be correspondingly lower, it will be adequate for the less extreme conditions. Denitrification is improved at slower flow-through speeds and accumulations of excess fertilizer counteracted by rainwater. (In the absence of rain, tap water can be used for this purpose.)

Micro-organisms require oxygen in order to be able to mineralize organic compounds and to provide nitrification (i.e., convert ammonium first into nitrite and then into nitrate. This means that nitrification has to take place in the front part of the filter, where large quantities of oxygen are added to the water by means of spray aeration. The higher the flow-through speed, the further the oxygen is carried into the filter, and the larger will be the zone containing oxygen-enriched water, and thus the larger the zone in which nitrification can take place.

Denitrification (i.e., the reduction of nitrate to nitrogen) takes place in a medium which is not well oxygenated - in other words, towards the back of the filter. At slow flow-through speeds less oxygen will be carried into the filter than at higher speeds. The oxygen is used up in the front part of the filter and in the back part a large zone which is not well oxygenated (i.e., a denitrification zone) develops.

The flow-through speed affects not only the balance between nitrification and denitrification, but also the rate of growth of the micro-organisms. If the flow-through speed - and thus the level of oxygenation - is high, then high rates of decomposition and of growth will also be possible. This means the filter will have to be cleaned more frequently when flow-through speeds are high, on account of the greater quantities of biomass produced. For optimum performance it is therefore important that the flow-through speed be adapted to the prevailing conditions. This means that if pollution in the pond is severe, a high flow-through speed should be selected to begin with. Under normal circumstances, a biological equilibrium will have been established in the pond 2-4 weeks after the Biotec Filter System has been put into operation. At this point the flow-through speed can be reduced.

For ponds that are only slightly polluted a lower flow-through speed may be selected to begin with. This means that one of the less powerful types of pond pump would perform satisfactorily. However, it is recommended that a reasonably robust pump capable of operation at a variety of settings be used.


Biological Additives

BIO-KICK

BIO-KICK is a filter starter developed by Biotec. It contains specially cultivated bacteria and high-quality additives which accelerate initial settlement in new biological filter units. The BIO-KICK bacteria are taken from their natural environment (water and soil), sorted according to their most desirable characteristics, and then concentrated. If BIO-KICK is used, running-in periods for filters will be reduced to a minimum. BIO-KICK should also be used after fish have received medication, in order to counteract any deterioration in filtering that may have been caused by antibiotics.

BIO-ACCU

BIO-ACCU stores energy for the micro-organisms and should be added 2-4 weeks after the use of BIO-KICK. It provides additional nutrition for the bacteria living in the Biotec-Filter and thus consolidates and intensifies the filtering process.

BIO-STABILIZER

BIO-STABILIZER can be used to maintain the biological equilibrium of both new and well run-in filters. BIO-STABILIZER contains no bacteria, since by the time it is used enough active biomass will have settled in the filter. It should be added 2-4 weeks after the use of BIO-ACCU, and then once again after approximately 6 weeks.


Bitron 11

Bitron 11 is an optionally available unit which contains an ultraviolet C lamp (see figure 8). It should be connected up in front of the Biotec-Filter. The UVC rays of the Bitron 11 lamp are highly energized and of short wavelength. They destroy algae and pathogens and cause them to flocculate (clump together), so that they can be easily removed from the pond water before it reaches the biofilter itself. UVC treatment will prevent algae which are able to pass through the filter from being returned to the pond and turning the water green. The efficiency of the filter is increased, and additional food is made available to the micro-organisms in the system.

UVC rays have been used in garden-pond filter systems for some time, and it is now known that over a period of years algae can develop a resistance to these rays. Once they have developed such a resistance, UVC lamps are virtually useless.

The algae become resistant if the water is exposed to UVC rays for insufficient periods of time and in consequence only small numbers of algae are destroyed. Those algae which adapt best not only survive but go on to propagate their UVC resistance.

The Bitron 11 lamp was designed for use in a bypass which only some of the polluted pond water is allowed to flow through. This small volume of water (small in relation to the entire volume of water in the system) is exposed to the UVC rays for an extended period, with the result that virtually all the algae are destroyed. Thus unintentional breeding of resistant algae mutations in either the short or the long term is precluded. UVC rays cause oxidation and are germicidal. They leave no traces of toxins in the water.

Food Pyramid 		Water Quality Page
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