Types of plants for nitrification
Fig 6.10 shows examples of the design of single and two sludge activated sludge
treatment plants. Fig 6.11 shows some principal types for nitrification in biofilters.
These plant types should be regarded as two sludge treatment plants, even though
their functional design may suggest that they were single sludge treatment plants.
This is due to the fact that the biological tanks shown in Fig 6.11 may be considered
to have plug flow, whereas the necessary conditions for the presence of nitrifying
bacteria are only found in the lower part of the filters.
Fig 6.10 Examples of the layout of single and two sludge activated sludge treatment plants for
nitrification.
Fig 6.11 Examples ofbioftlters for nitrification.
6.2.1 Nitrification plants with separate sludge
The operation of activated sludge treatment plants for the nitrification of wastewater of which the only oxygen-consuming substance is ammonium is very difficult in practice. Normally the settling behaviour of the sludge is bad, and due to the
very small sludge production during the process it is difficult to maintain a reasonable sludge mass in the plant. In practice, plants for this type of wastewater are
nearly always designed as biofilters.
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