Quantitative balance and analysis of fulvic acids changes in the process of municipal sewage treatment

Abstract

The latest researches show that large amounts of humic substances (HS) are discharged by municipal facilities, including sewage treatment plants, therefore this paper covers characteristics of a soluble HS fraction, i.e. fulvic acids (FAs) contained in municipal sewage and balance of their amounts introduced to and discharged from a biological reactor.FAs were extracted from samples collected from mechanically and biologically treated sewage and from sewage and activated sewage sludge, from the following cells of a biological reactor: predenitrification, dephosphatation, denitrification and nitrification, according to the flow through sewage treatment plant's section.The paper discussed quantitative (concentrations and 24-h loads of FAs introduced to and discharged from the biological reactor) and qualitative (basic composition, share of selected non-organic pollutants, including heavy metals, thermo-gravimetric analysis and infra-red spectroscopy) research. Additional, atomic quotients (C/O, C/H, C/N and O/H) of basic composition were defined, which made possible to conduct analysis of FAs chemical and biochemical changes in the process of sewage treatment in the biological reactor. The conducted quantitative balance of FAs, extracted from raw sewage and activated sewage sludge indicated that these substances are not subjects to biodegradation but, to a large extent, they are precipitated and absorbed on activated sewage sludge. The remaining quantities are discharged from a sewage treatment plant together with treated sewage.

Keywords

• Humic substances
• Sewage sludge
• Biological reactor
• Biodegradation
• Adsorption