Biological Effluent Treatment

Reduction of biodegradable organic carbon from reduced groundwater by filtration

In semi-industrial trials, biological conversion processes for the removal of iron, nitrification and the removal of manganese by rapid filtration have been tested in the treatment of groundwater of low oxygen content for the supply of drinking water. A reduction of some 30% in the biodegradable organic carbon content has been achieved. Wet filtration has been clearly superior to dry filtration.

 

Summary

In addition to increased concentrations of iron, ammonium and manganese, near-surface groundwater of low oxygen content frequently contains naturally-occurring organic water constituents which, in the presence of oxygen, may be a source of contamination.

To date, germ-free drinking water treatment has been achieved by rapid filtration and the addition of flocculents, with disinfection by chlorination or ozonisation. Contact filtration, in which organic constituents are removed by adsorption in precipitated iron flakes and subject to biodegradation, is increasingly applied as a means of preventing unwanted disinfection by-products.

For the targeted analysis of biological conversion processes, two process variants for dry/wet filtration and separate wet filtration have been applied to raw water mixtures and shallow well water in a semi-industrial trial installation using contact filtration.

 

Results:

In accordance with analyses, a reduction in the overall carbon content has been observed, in addition to iron removal, nitrification and manganese removal. This was attributable to a combination of the adsorption of organic substances in precipitated iron flakes and biological conversion processes.

A reduction of some 30% in the biodegradable organic carbon content (BDOC) has been observed in both types of raw water analysed, regardless of the process variant applied.

A reduction of the pH value from 7 to 6.2 has increased carbon degradation by a further 10%.

The assimilable organic carbon content (AOC) has only been reduced by wet filtration. Where dry filtration is applied, contamination associated with the presence of oxygen has been observed.

 

More Project Information

Project title: Reduction of biodegradable organic carbon from reduced groundwater by filtration

Project number: 02WT9718/2

Project period: 1997 - 1999

Project region: Germany (Hamburg)

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Source: German National Library of Science and Technology Hannover (TIB)