Puraflo Peat Fibre Replacement

Puraflo Peat Fibre

What is a Peat Filter

The peat filter can in some ways be considered to be a fixed film filtration system much like other sewage treatment filters composed of sand or artificial media. Peat, however, has unique chemical, physical and biological properties, all of which contribute to the sewage treatment process. Sewage treatment within the peat filter is accomplished by a combination of physical filtration, chemical adsorption, and biological treatment by microorganisms. Peat fibers are polar, have a high surface area, and a highly porous structure (90-95% porosity).

These properties enable the peat bed to hold a large amount of water, much like a sponge. As a result, effluent has a long residence time in the peat. As the wastewater is wicked through the peat it flows in a thin film over the surfaces of the peat fibers. This allows the effluent to become aerated, become exposed to the acidic chemical environment of the peat, and come in close contact with the microbiological community inhabiting the peat. The relatively constant moisture content of the peat filter also enables the survival of the natural microbial population in the peat even when the system is not being actively used. Moisture in the peat also helps keep the temperature of the peat bed relatively constant even when outside air temperatures change. This likely accounts for peat’s ability to perform well even in very cold conditions. Solids that are larger than the interstitial channels in the peat are trapped on the peat fibers as the effluent trickles through the peat. This accounts for the very low total suspended solids seen in finished effluent and may account for some removal of BOD as organic particles are trapped for later digestion. The highly polar nature of the peat fibers creates an environment with a high cation exchange capacity.

How it works

Many wastewater components become chemically adsorbed to the peat fiber surface causing them to be trapped in the peat. Peat’s highly porous structure and very high surface area make the peat bed an ideal environment for supporting an aerobic microbiological community that performs biological treatment of the sewage. Within several weeks of use the peat filter is colonised by a range of microorganisms and invertebrates from the septic tank effluent and the surrounding soil. These include bacteria, fungi, protozoa, nematodes, earthworms, rotifers and others. Treatment of the septic tank effluent is performed mainly by acid-tolerant bacteria and fungi living in the peat media. Pathogenic bacteria in the wastewater undergo significant die-off in the peat due to the acidic conditions and predation and competition from the natural microbiological community in the peat. It is also possible that the fungi in the peat produce antibiotics and that the peat itself releases antibiotic and phenolic substances that further act to reduce bacterial numbers.