Alkalinity and external carbon requirements for denitrification-nitrification of coke wastewater

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 CaCO/mg [Formula: see text]) 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 CaCO). 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 [Formula: see text] 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 (NaCO at 300 mg/L) and acetic acid dosing enabled an effluent TN of 24 mg/L.

The Influence of Different Operation Conditions on the Treatment of Mariculture Wastewater by the Combined System of Anoxic Filter and Membrane Bioreactor

“…When the alkalinity of the influent was 500 mg/L, the treatment efficiency in TOC removal was a little better than for other values of alkalinity. It was reported that when the alkalinity is low, the pH of the system would decrease significantly as the reaction proceeds, which will affect microbial activity and reduce the treatment efficiency of the system [44]. However, in this study, even if the applied alkalinity was as low as 300 mg/L, no obvious decrease of the removal performance was observed.…”

“…The availability of inorganic carbon was critical for stable nitrification to provide sufficient alkalinity to buffer the acidification resulting from the production of hydrogen ions during ammonia oxidation. Furthermore, the loss of nitrification resulted in a decrease in nitrate concentrations being recycled back to the anoxic reactor, which led to reduced inorganic carbon formation through denitrification, further exacerbating the shortage of inorganic carbon in the aerobic cell [44]. The provision of adequate alkalinity for nitrogen removal was therefore essential for a stable treatment.…”

Nitrogen removal from coke making wastewater through a pre-denitrification activated sludge process

“…The addition of sodium carbonate was previously established in coke wastewater samples taken from the full-scale steelworks, as critical for successful nitrification of coke making wastewater through the provision of inorganic carbon for nitrifying bacteria and pH buffering (Raper et al, 2018b). The influent wastewater was therefore dosed with the optimised concentration of sodium carbonate of 523 mg/L as CaCO 3 .…”

Enhancing the removal of pollutants from coke wastewater by bioaugmentation: A scoping study

“…The impact of alkalinity addition, micronutrient addition and bioaugmentation was investigated by spiking the coke wastewater. Alkalinity was added at the previously optimized dose of 300 mg L –1 (as CaCO 3 ) through the addition of sodium carbonate (Na 2 CO 3 ) . A micronutrient solution was designed taking account of the coke wastewater characterization and activated sludge nutrient requirements reported by Burgess et al .…”

“…Alkalinity was added at the previously optimized dose of 300 mg L -1 (as CaCO 3 ) through the addition of sodium carbonate (Na 2 CO 3 ). 25 A micronutrient solution was designed taking account of the coke wastewater characterization and activated sludge nutrient requirements reported by Burgess et al 6 (Table 1). A commercially available bioaugmentation product was added at doses of 0.1, 0.5 and 1.5 g L -1 .…”