Estimate of denitrifying microbiota in tertiary sewage treatment and kinetics of the denitrification process using different sources of carbon

Abstract

A study of the kinetics of denitrification was carried out in the laboratory based on the quantification of N2O, the final product of the activity of denitrifying microorganisms, when the enzymatic reduction of N2O to N2 was blocked by acetylene. Concentrated mixed liquor (sludge from a reactor with intermittent aeration used for sewage treatment) was used as the inoculum, while methanol, acetic acid, glucose, effluent sewage from an anaerobic fluidized bed reactor and synthetic substrate simulating domestic sewage were used as carbon sources. The mean concentration of nitrate was 20 mg/L. Maxima of N2O production and NO3 -consumption occurred between 0.5h and 2.0h of incubation using all the carbon sources, which characterized the denitrification process. Acetic acid and methanol were responsible for the highest rates of N2O production. The estimated number of denitrifying microorganisms in the reactor with intermittent aeration, using the MPN technique, varied from 10 9 to 10 10 MPN/g VSS, indicating a high potential for the occurrence of denitrification.

Nitrogen removal in a wastewater treatment plant through biofilters: nitrous oxide emissions during nitrification and denitrification

“…However, this is not the case here since a reduction in nitrate is invariably found and denitrification rates are directly correlated with the quantities of added methanol (R 2 = 0.90, Fig. 7); these observations are in agreement with those by Marchetto et al [35], who showed that beyond a ratio COD/N-NO 3 -of 1.9 (i.e. 40% MeH), the effectiveness of denitrification increases regularly (up to a COD/N-NO 3 -ratio of 5, or 120% MeH).…”

“…In fact, whereas Itokawa et al [32] used sodium acetate as a source of carbon, we used both methanol and the carbon contained in domestic wastewater for the activated sludge experiments [14]. Note that Marchetto et al [35] found the maximum N 2 O production rates in descending order, with acetic acid, methanol, domestic sewage, glucose and synthetic sewage.…”

Substrate-dependent denitrification of abundant probe-defined denitrifying bacteria in activated sludge

“…Although activated sludge denitrification appears to be driven by few denitrifying bacterial groups; the substrate utilization specificity of these denitrifiers in full-scale activated sludge plants is only partially understood. Acetate is widely reported to promote the highest denitrification rates (3-12 mg NO x -N gVSS À1 h À1 ) for different activated sludge types (Gerber et al, 1987;Eilersen et al, 1995;Lee & Welander, 1996;Hallin & Pell, 1998;Marchetto et al, 2003), but mixed, complex substrates are also reported to yield high rates (Monteith et al, 1980;Lee & Welander, 1996). Recent ecophysiological studies on denitrification have shown that some denitrifying bacteria in activated sludge appear very specialized in their substrate uptake while others are more versatile (Thomsen et al, 2007).…”

Remoção de nitrogênio de águas residuárias com elevada concentração de nitrogênio amoniacal em reator contendo biomassa em suspensão operado em bateladas seqüenciais e sob aeração intermitente

“…Essa alternância de valores foi relatada por vários autores e é considerada como comportamento inerente a sistemas com aeração intermitente (WAREHAM et al, 1993, RA et al, 2000, VILLAVERDE et al, 2000 5.1.4 -Perfil temporal de um ciclo anóxico/aeróbio Tam et al (1994) demonstraram que a adição de substrato prontamente biodegradável como acetato de sódio melhorou significativamente a eficiência de remoção, quando comparado com metanol e glicose. Aesoy et al (1998) As velocidades de desnitrificação via nitrato de Marchetto et al (2003), com uso de diferentes fontes de carbono, como ácido acético, metanol, esgoto doméstico, glicose e esgoto sintético, variaram de 0,25 a 0,39 g N/gSTV.d. Os autores obtiveram velocidades mais rápidas com ácido acético e metanol e concluíram que a eficiência de remoção de N deveu-se aos valores favoráveis de balanço energético de formação e degradação dos compostos envolvidos no processo.…”

“…Os resultados de velocidade de desnitrificação nesse experimento pelas duas vias (nitrato e nitrito) foram muito semelhantes e esses valores se aproximam dos resultados obtidos por Marchetto et al (2003), com uso de fonte de esgoto sintético e glicose como fontes de carbono. Almeida et al (1995)…”