Combining the biological nitrogen and sulfur cycles in anaerobic conditions

Abstract

The biochemical processes involved in the anaerobic degradation of carbon, nitrogen and sulfur compounds can be represented by an oxidation-reduction or electron donor-acceptor scheme. The theoretic values of Gibbs free energy (deltaG0) calculated from thermodynamic data indicate the feasibility of the reactions. The interactions C-S and C-N are well known but there is a lack of information about the interaction N-S. The anaerobic transformation of nitrates using reduced sulfur compounds can be explained considering that nitrate acts as electron acceptor while reduced sulfur compounds are the electron donors. A new N-S interaction in anaerobic conditions (ORP = -425 mV) has been experimentally observed when treating industrial wastewater rich in organic nitrogen and sulfate. The mass balances of the different nitrogenous and sulfur compounds in the liquid and gas phases clearly indicated an uncommon evolution. An important percentage of the nitrogen entering the reactor as TKN was removed from the liquid phase appearing as N2 in the gas phase. Simultaneously, only part of the sulfate initially present in the influent appeared as sulfide in the effluent or as hydrogen sulfide in the gas. These experimental observations may suggest a new anaerobic N-S biological interaction involving simultaneous anaerobic ammonium oxidation and sulfate reduction, ammonium being the electron donor and sulfate the electron acceptor.

Sulfate-reducing anaerobic ammonium oxidation as a potential treatment method for high nitrogen-content wastewater

“…Thus, the newly-discovered bacterium, named Anammoxoglobus sulfate, performs the first stage of SRAO, a reaction described by Eq. 2 as initially assumed by Fdz-Polanco et al (2001). The discovery made by Liu et al (2008) shows that anammox microorganisms have a more versatile metabolisms than previously assumed and that at least some of them may use electron acceptors alternative to NO 2 -.…”

“…Sulfate-reducing ammonium oxidation (SRAO) process was first assumed by Fdz-Polanco et al (2001) to explain ''abnormal'' losses of nitrogen and sulfate observed by the authors while researching the anaerobic treatment of yeast wastewater in a fluidized-bed reactor. Fdz-Polanco et al (2001) have shown the feasibility of methanogenesis and SRAO in a single reactor and proposed a summary equation describing the two-staged process:…”

“…Fdz-Polanco et al (2001) have shown the feasibility of methanogenesis and SRAO in a single reactor and proposed a summary equation describing the two-staged process:…”

Sulfur reducing bacteria from coal pits waste heaps of Chervonograd mining region

“…1) [16,28,30]. The most of representatives of Desulfuromonaceae and Geobacteraceae reduce sulfur compounds as well as some metals with variable valence [8,21,23,[25][26][27]34] and support chlorine and nitrogen reduction [4,15,32].…”

How reliable are thermodynamic feasibility statements of biochemical pathways?

“…Thermodynamic considerations may for instance help to predict growth parameters like biomass yields (Fdz-Polanco et al, 2001;Heijnen et al, 1992;Roels, 1983), maintenance coefficients m S (Tijhuis et al, 1993), maximum growth rates m MAX or threshold concentrations (Heijnen, 1999). The extension of thermodynamics into nonequilibrium process can even provide useful information about the kinetics of biological systems (Stephanopoulos et al, 1998;Westerhoff and van Dam, 1987).…”