Challenges in Treatment of Digestate Liquid Fraction from Biogas Plant. Performance of Nitrogen Removal and Microbial Activity in Activated Sludge Process

Abstract

Even thoughdigestate, which is continually generated in anaerobic digestion process, can only be used as fertilizer during the growing season, digestate treatment is still a critical, environmental problem. That is why the present work aims to develop a method to manage digestate in agricultural biogas plant in periods when its use as fertilizer is not possible. A lab-scale system for the biological treatment of the digestate liquid fraction using the activated sludge method with a separate denitrification chamber was constructed and tested. The nitrogen load that was added tothe digestate liquid fraction accounted for 78.53% of the total nitrogen load fed into the reactor. External carbon sources, such as acetic acid, as well as flume water and molasses, i.e., wastewater and by-products from a sugar factory, were used to support the denitrification process. The best results were obtained using an acetic acid and COD (Chemical Oxygen Demand)/NO3–N (Nitrate Nitrogen) ratio of 7.5. The removal efficiency of TN (Total Nitrogen), NH4–N (Ammonia Nitrogen) and COD was 83.73%, 99.94%, 86.26%, respectively. It was interesting to see results obtained that were similar to those obtained when using flume water and COD/NO3–N at a ratio of 8.7. This indicates that flume water can be used as an alternative carbon source to intensify biological nitrogen removal from digestate.

Performance of an Innovative Low-Cost Recycled Filling (LCRF) in Anaerobic Treatment of Dairy Effluent—A Pilot-Scale Study

“…Of course, converting organic P species into orthophosphates makes it easier to remove them in subsequent treatments [ 49 ]. Methods used to this end include an aerobic pass (activated sludge step) [ 50 ], biological beds, hydrophyte-based treatments, chemical precipitation with iron- or clay-based inorganic coagulants [ 51 , 52 ] and microalgae [ 46 ]. One approach increasingly discussed in the literature is the use of active fillings to promote phosphorus removal directly in the digester [ 53 ].…”

Managing the Effluents of Anaerobic Fermentations by Bioprocess Schemes Involving Membrane Bioreactors and Bio-Electrochemical Systems: A Mini-Review

“…Conventional wastewater technologies, such as an improved activated sludge method, can be effective as environmentally sound post-treatment for anaerobic effluents. However, they present the double disadvantage of requiring an additional carbon source for denitrification and of losing agriculturally useful nitrogen compounds by converting them to N 2 gas [66]. Likewise, by biodegrading an unnecessary portion of the polluting organic matter and releasing the carbon content as CO 2 to the atmosphere, they lose organic carbon compounds that could serve as much-needed humus precursors in cultivated soils [19].…”

Insights into the microbial community structure in the biodegradation process of high-strength ammonia digestate liquid fraction in conventional activated sludge system

“…The methodology for analysing concentrations of total nitrogen (TN), ammonia nitrogen (NH4-N), nitrate nitrogen (NO3-N), nitrite nitrogen (NO2-N), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), mixed liquor volatile suspended solids (MLVSS), as well as pH and oxygen content measurement methods were described in a previous article (Chuda and Ziemiński 2021b). The concentrations of volatile fatty acids (VFAs) and sugars were determined using the Agilent 7890A gas chromatograph (Agilent Technologies, Santa Clara, CA, USA) and UV-spectrophotometer (Thermo Scientific Multiskan Go, Thermo Fisher Scientific, Munich, Germany), respectively, following the procedures described by Cieciura-Włoch et al (2021).…”

“…The COD loading rate depended on the type of carbon source and CODext/NO3-N ratio and ranged from 172.99 ± 22.82 (DAA1, DFW1, DMS1 series) to 218.89 ± 29.79 mg O2/g MLVSS d (DAA2, DFW2 and DMS2 series). The method of determining CODext/NO3-N ratio in the influent, and thus COD/TN ratio, as well as the dimensions and operating parameters of the reactors were presented in detail in the authors' previous article (Chuda and Ziemiński 2021b).…”