Monitoring the denitrification of wastewater containing high concentrations of nitrate with methanol in a sulfur-packed reactor.
Biological denitrification of high nitrate-containing wastewater was examined in a sulfur-packed column using a smaller amount of methanol than required stoichiometrically for heterotrophic denitrification. In the absence of methanol, the observed nitrate removal efficiency was only about 40%, and remained at 400 mg NO(3)(-)-N/l, which was due to an alkalinity deficiency of the pH buffer and of CO(2) as a carbon source. Complete denitrification was achieved by adding approximately 1.4 g methanol/g nitrate-nitrogen (NO(3)(-)-N) to a sulfur-packed reactor. As the methanol concentration increased, the overall nitrate removal efficiency increased. As influent methanol concentrations increased from 285 to 570, 855, and 1,140 mg/l, the value of Delta mg alkalinity as CaCO(3) consumed/Delta mg NO(3)(-)-N removed increased from -1.94 to -0.84, 0.24, and 0.96, and Delta mg SO(4)(2-) produced/Delta mg NO(3)(-)-N removed decreased from 4.42 to 3.57, 2.58, and 1.26, respectively. These results imply the co-occurrence of simultaneous autotrophic and heterotrophic denitrification. Sulfur-utilizing autotrophic denitrification in the presence of a small amount of methanol is very effective at decreasing both sulfate production and alkalinity consumption. Most of methanol added was removed completely in the effluent. A small amount of nitrite accumulated in the mixotrophic column, which was less than 20 mg NO(2)(-) -N/l, while under heterotrophic denitrification conditions, nitrite accumulated steadily and increased to 60 mg NO(2)(-) -N/l with increasing column height.
Kim
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IS
Department of Environmental Science and Engineering, Kwangju Institute of Science and Technology (K-JIST), 1 Oryong-dong, Puk-gu, Kwangju 500-712, Korea. iskim@kjist.ac.kr
Oh
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SE
Bum
M S
MS
Lee
J L
JL
Lee
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ST
D019149:Bioreactors; D006863:Hydrogen-Ion Concentration; D000432:Methanol / Q000378:metabolism; D009566:Nitrates / Q000737:chemistry* / Q000378:metabolism; D009584:Nitrogen / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014871:Water Microbiology; D018508:Water Purification
D009566:Nitrates; D013455:Sulfur; D009584:Nitrogen; D000432:Methanol