Filtralite - Processes for Wastewater treatment

Processes for Wastewater treatment

Biological filtration

Among the essential parts in the biological aerated filters, (BAF), is the filter media. The biomass that treats organic and nitrogenous matters is fixed to the Filtralite medium, which also works well as a mechanical filter for suspended solids. Filtralite is used both in processes of aerobe systems (nitrification and organic matter) and anoxic systems (denitrification).

Both crushed and uncrushed Filtralite are excellent as a growth medium for bacteria. In biofilm processes the total efficiency is dependent on the utilisation of support media. Large available growth surface on the media is important and gives a high concentration of specialised groups of bacteria. This enables the process to be very efficient on volumetric basis. Crushed Filtralite has a rough and angular surface with sharp edges and a large porosity. The crushed particles have a larger surface area than the rounded particles and are therefore more effective in most reactors.

Biological processes are very dependent of time. Therefore it is essential that the contact time, i.e. the time the water is in contact with the filter media and bacteria, is as long as possible. In most cases the contact time for BAF filters is about 20 minutes.

Tertiary filtration

As water is a scarce resource in many parts of the world, reuse of water has become more and more normal. To be able to reuse the effluents, tertiary filtration for removal of suspended solids is necessary. The same will be the situation in areas with extra sensitive recipients.

Filtralite has proved to be as good as, or better than, comparable filter media, both in single- and dual media filters. In dual media filters, by replacing the most traditional top layer filter material, anthracite, with Filtralite, time between backwashes can be increased by about 25%. This means fewer stops for backwash and reduced use of backwash water, resulting in more stable operation and lower operational costs.

In single media filters using Filtralite the time between backwashes has been recorded to be up to 4-5 times as long as for filters using sand as filter media.

Filters with Filtralite can be operated within a large range of filtration rates. The filtration rate will always be dependent of the configuration of the filter and the treatment process. Filtralite tertiary filters can operate at up to around 15-20 m/h.