In 2014, DC Water will begin operating a new solids processing train at the Blue Plains Advanced Wastewater Treatment Plant consisting of the CAMBI thermal hydrolysis process for solids pretreatment prior to mesophilic anaerobic digestion. DC Water has chosen sequencing batch reactors capable of nitritation-denitritation or deammonification (using the DEMON process) for separate biological treatment of the dewatering sidestream. As part of the sidestream treatment alternatives evaluation, studies were conducted using sidestream generated from an existing CAMBI-digestion plant to confirm the suitability of the DEMON process to treat such a sidestream and to provide insight on design loading rates and related issues. Experimental results reveal a significant reduction in nitrogen conversion rates-rather for the aerobic ammonia oxidizers than for the anammox organisms. Both biomass acclimation and decrease in refractory soluble COD concentrations could alleviate inhibitory impacts.

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Nitrifying granules were grown in a sidestream reactor fed municipal anaerobic digestion centrate and added in an initial slug dose and subsequent smaller daily doses to a non-nitrifying mainstream activated sludge system at 12 °C and 2.5-day aerobic solids retention time (SRT) to increase its nitrification capacity. Effluent NH3-N concentrations less than 1 mg/L were achieved with bioaugmentation, and nitrification was immediately lost when granules were removed after 30 days of bioaugmentation. Molecular microbial analyses indicated that nitrifying organisms remained attached to granules in the mainstream system with little loss to the flocculent sludge. Maximum specific nitrification activity of the bioaugmented granules decreased in mainstream treatment but the nitrification capacity remained due to new granule growth in the mainstream. This study demonstrated that bioaugmentation with sidestream nitrifying granules can intensify nitrification capacity in low-SRT, low-temperature flocculent activated sludge systems to achieve low effluent NH3-N concentrations and nitrogen removal.