Wastewater denitrification process—the influence of methanol and kinetic analysis

Abstract

The aim of this work was to achieve rapid nitrate removal from synthetic wastewater (SW) without nitrite accumulation and to improve the economic effectiveness of the process. For that purpose, experiments were carried out to determine the influence of methanol on denitrification rate in batch assays and in the continuous-flow stirred cultures. Nitrate Á/N (200 mgNO 3 ( Á/N/l) was reduced under anoxic conditions during approximately 4 Á/6 h for the MeOH/NO 3 ( Á/N ratio above 2.5. Nitrite concentration was elevated to the maximum of 1.2 mgNO 2 ( Á/N/l and at the end of the tests nitrite concentrations were 0.06 Á/0.1 mgNO 2 ( Á/N/l. At lower MeOH/NO 3 ( Á/N ratios the denitrification process stopped after exhaustion of methanol. The analysis of experimental results showed that denitrification was a zero-order reaction with respect to nitrate and a first-order reaction with respect to the biomass concentration (the first-order overall reaction). In the continuous denitrification process during 45 days the hydraulic retention time (HRT) was decreased from 62 to 28 h. Dissolved oxygen concentration fell from 5.50 to 0.40 mgO 2 /l during the first 4 h, but over 3 days of continuous flow it increased to 2.5 mgO 2 /l and remained at that level. Accumulation of nitrite ions in SW was similar to that in batch tests, but at an HRT of 28 h the nitrite concentration increased to 6 mgNO 2 ( Á/N/l. Complete denitrification at 25 8C was achieved at nitrate and methanol loading rates of 4.35 mgNO 3 ( Á/N/l h and 23 mgO 2 /l h, respectively.

Nitrate removal with bacterial cells attached to quartz sand and zeolite from salty wastewaters

“…4 and 5). Gas production was also measured, as described in our previous papers (Foglar and Briški 2003;Foglar et al 2005). At the nitrate loading rate of 11.76 mg NO 3 --N L -1 the generated nitrogen gas volume accounted for 9.7 mL N 2 L -1 h -1 which was in agreement with the previously published data (Clifford and Liu 1993).…”

“…and Paracoccus sp. were the only true denitrifiers (Zellner et al 1995;Glass and Silverstein 1998;Foglar and Briški 2003). Paracoccus and Pseudomonas bacterial genera being such, their presence in mixed culture obviously accomplished complete nitrate removal with minimum nitrite accumulation.…”

“…The used apparatus was similar to the previously described one (Foglar and Briški 2003). In the 0.3 dm 3 bioreactor (diameter 54 mm and height 200 mm) the barrier-grid was placed above the magnetic mixer.…”

Denitrification of nitrate-contaminated groundwater using biodegradable snack ware as carbon source under low-temperature condition

“…3). Denitrification rate had a negligible change, and was maintained in the range of 9-10 mg/(L h) with 20-50 mg/L of initial concentration of NO 3 -N, indicating a zero-order kinetic model can be used to described the denitrification process under this condition (Foglar and Briski 2003). Several studies have shown that denitrification rate increased consistently with an increase in the initial NO 3 -N concentration using soluble carbon sources (Elefsiniotis and Li 2006), which conflicts with obtained results.…”

Enhancing denitrification using a carbon supplement generated from the wet oxidation of waste activated sludge

“…N 2 ) during respiratory denitrification (Lee and Welander, 1996). The denitrification process depends on a number of factors, including change in environmental conditions (temperature and pH), dissolved oxygen and the presence or accumulation of nitrite during the process (Foglar and Briški, 2003). Critically important amongst these factors is the presence and nature of the electron donor, which is usually an organic carbon source (Lee et al, 2003).…”