Supernatant organics from anaerobic digestion after thermal hydrolysis cause direct and/or diffusional activity loss for nitritation and anammox. (15th October 2018)

• Record Type: Journal Article
• Authors: Zhang, Qi; Vlaeminck, Siegfried E.; DeBarbadillo, Christine; Su, Chunyang; Al-Omari, Ahmed; Wett, Bernhard; Pümpel, Thomas; Shaw, Andrew; Chandran, Kartik; Murthy, Sudhir; De Clippeleir, Haydée
• Is Part Of: Water research. Volume 143(2018)
• Page Start: 270
• Page End: 281
• Publication Date: 2018-10-15
• Subjects: Biological nutrient removal -- Partial nitrification/anammox -- Water resources recovery facility; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2018.06.037
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Treatment of sewage sludge with a thermal hydrolysis process (THP) followed by anaerobic digestion (AD) enables to boost biogas production and minimize residual sludge volumes. However, the reject water can cause inhibition to aerobic and anoxic ammonium-oxidizing bacteria (AerAOB & AnAOB), the two key microbial groups involved in the deammonification process. Firstly, a detailed investigation elucidated the impact of different organic fractions present in THP-AD return liquor on AerAOB and AnAOB activity. For AnAOB, soluble compounds linked to THP conditions and AD performance caused the main inhibition. Direct inhibition by dissolved organics was also observed for AerAOB, but could be overcome by treating the filtrate with extended aerobic or anaerobic incubation or with activated carbon. AerAOB additionally suffered from particulate and colloidal organics limiting the diffusion of substrates. This was resolved by improving the dewatering process through an optimized flocculant polymer dose and/or addition of coagulant polymer to better capture the large colloidal fraction, especially in case of unstable AD performance. Secondly, a new inhibition model for AerAOB included diffusion-limiting compounds based on the porter-equation, and achieved the best fit with the experimental data, highlighting that AerAOB were highly sensitive to large colloids. Overall, this paper for the first time provides separate identification of organic fractions within THP-AD filtrate causing differential types of inhibition. Moreover, it highlights the combined effect of the performance of THP, AD and dewatering on the downstream autotrophic nitrogen removal kinetics. Graphical abstract: Image 1 Highlights: Four organic fractions quantified in digester filtrate after thermal hydrolysis. Organics inhibit aerobic and anoxic ammonium-oxidizing bacteria (AerAOB and AnAOB). Dissolved organics and small colloids directly inhibit AerAOB and AnAOB. Large colloids create diffusion resistance indirectly limiting AerAOB activity. Digester stability and chemically optimized dewatering facilitate deammonification.