The inhibitory impact of ammonia on thermally hydrolyzed sludge fed anaerobic digestion. (1st February 2021)

• Record Type: Journal Article
• Authors: Li, Baoqiang; Ladipo‐Obasa, Mojolaoluwa; Romero, Adrian; Wadhawan, Tanush; Tobin, Michael; Manning, Elizabeth; Higgins, Matthew; Al‐Omari, Ahmed; Murthy, Sudhir; Novak, John T.; Riffat, Rumana; De Clippeleir, Haydée
• Is Part Of: Water environment research. Volume 93:Number 8(2021)
• Page Start: 1263
• Page End: 1275
• Publication Date: 2021-02-01
• Subjects: AD -- biosolids -- free ammonia -- inhibition kinetics -- NH3 -- TAN -- THP; Water quality management -- Periodicals; Water -- Purification -- Periodicals; Water -- Pollution -- Periodicals; Water -- Pollution; Water -- Purification; Water quality management; Sewage; Water Pollution; Periodicals; Electronic journals; Periodicals; 628.16
• DOI: 10.1002/wer.1509
• Languages: English
• ISSNs: 1061-4303

Abstract

Abstract: This study evaluated the impact of ammonia on mesophilic anaerobic digestion (AD) with thermal hydrolysis pretreatment (THP) treating a mixture of primary sludge and waste activated sludge and operated under constant organic loading rate of 9 kg COD/m 3 /d. Free ammonia concentrations in the digesters were varied between 37 and 966 mg NH3 ‐N/L, while maintaining all other operational conditions constant. A decrease in volatile solids reduction from 54 ± 5% (at <554 mg NH3 ‐N/L) to 35 ± 6% at the maximum free ammonia concentration of 966 mg NH3 ‐N/L was observed at steady‐state conditions. No impact of free ammonia on final dewaterability was detected. Free ammonia thus mostly limited methanogenesis. A free ammonia Monod inhibition constant of 847 ± 222 mg NH3 ‐N/L for methanogens was estimated based on the digester steady‐state methane rates dynamics. This study showed that current THP AD digesters (typically 110–260 mg NH3 ‐N/L) operate under 12%–18% ammonia inhibition for methanogenesis. Operation under SRT of 15 days, about 2 times more than needed to retain methanogens, can compensate for lower methanogens rates and avoid performance impacts. The later shows a good potential to operate under higher free and total ammonia concentration without jeopardizing performance. Practitioner points: Only from a free ammonia concentration above 554 mg NH3 ‐N/L, decreased volatile solids reduction and biogas yield were observed. A volatile solids reduction of 35 ± 6% at maximum free ammonia concentration of 966 mg NH3 ‐N/L was still achieved. A Monod inhibition constant for methanogens of 847 ± 222 mg NH3 ‐N/L was estimated. It was estimated that current THP AD systems (110–260 mg NH3 ‐N/L) operate under 12%–18% NH3 inhibition for methanogenesis. Abstract : Current THP AD systems (110‐260 mg NH3‐N/L) operate under 12‐18% NH3 inhibition for methanogenesis and have great potential for increased AD capacity and co‐digestion.