Alkalinity and external carbon requirements for denitrification-nitrification of coke wastewater. Issue 17 (2nd September 2018)

• Record Type: Journal Article
• Authors: Raper, Eleanor; Fisher, Raymond; Anderson, David R.; Stephenson, Tom; Soares, Ana
• Is Part Of: Environmental technology. Volume 39:Issue 17(2018)
• Page Start: 2266
• Page End: 2277
• Publication Date: 2018-09-02
• Subjects: Nitrification -- denitrification -- external carbon -- industrial wastewater; Environmental engineering -- Periodicals; Environmental protection -- Periodicals; 628.05
• DOI: 10.1080/09593330.2018.1437779
• Languages: English
• ISSNs: 0959-3330

Abstract

ABSTRACT: The Industrial Emissions Directive requires that coke wastewater is treated to reach an effluent with < 50 mg/L total nitrogen (TN). A shortage of alkalinity (3.6 mg as CaCO3 /mg ) in the wastewater limited nitrification to 45%. Various compounds were tested as a source of additional alkalinity, with optimal results being found for sodium carbonate, which enabled 95% nitrification at 300 mg/L (as CaCO3 ). Sodium bicarbonate led to incomplete ammonia oxidation (76%) whilst soda ash prevented nitrite oxidation. Addition of sodium hydroxide enabled 98% nitrification but was associated with accumulation. Ammonia and nitrite oxidation had optimal pH ranges of 7.0–8.3 and 5.5–6.8, respectively. As organic carbon concentrations in coke wastewater are at times insufficient for effective denitrification external organic carbon was also considered to enhance denitrification. A laboratory-scale anoxic-aerobic activated sludge process was used to investigate glycerol and acetic acid as carbon sources. Glycerol was associated with a low biomass production (0.18 mg of biomass produced per 1 mg of glycerol) and mixed liquor suspended solids (MLSS) declined from 2235 to 750 mg/L leading to incomplete nitrification (< 30%) and an effluent TN of 59 mg/L. Acetic acid had a higher biomass production (0.31 mg of biomass produced per 1 mg of acetic acid) maintaining stable MLSS concentrations (3137 mg/L). Overall, a denitrification-nitrification process with alkalinity (Na2 CO3 at 300 mg/L) and acetic acid dosing enabled an effluent TN of 24 mg/L.