Effects of organic matter and initial carbon–nitrogen ratio on the bioconversion of volatile fatty acids from sewage sludge

Modeling of enhanced VFAs production from waste activated sludge by modified ADM1 with improved particle swarm optimization for parameters estimation

“…The soluble and particulate fractions of proteins, carbohydrates, and lipids were separated by centrifugation at 10 000 rpm for 10 min, followed by filtration through a cellulose acetate membrane (pore size = 0.45 m). The COD, protein, carbohydrate, and lipid contents in the fermentation sludge were determined as described elsewhere [27].…”

Investigation of nutrient feeding strategies in a countercurrent mixed-acid multi-staged fermentation: Development of segregated-nitrogen model

“…Many studies show that carbon-nitrogen ratio greatly influences fermentation yield. Too much or too little nitrogen can limit fermentation performance (Kayhanian, 1994;Kayhanian and Rich, 1995;Kayhanian and Tchobanglous, 1992;Kim and Holtzapple, 2006;Liu et al, 2008;Marchaim, 1992;Oztekin et al, 2008). Previous mixed-acid fermentations did not quantify or control the carbon-nitrogen ratio (C/N ratio) Aiello-Mazzarri et al, 2006;Blasig et al, 1992;Coleman, 2007;Domke et al, 2004;Forrest et al, 2010;Fu and Holtzapple, 2009;Fu and Holtzapple, 2010a,b;Kayhanian and Rich, 1995;Moody, 2006;Ross and Holtzapple, 2001;Thanakoses et al, 2003); thus, these fermentations may have been hindered because of excess or limiting nitrogen.…”

“…For similar mixed-acid fermentations making methane or hydrogen, the literature cites a wide range of optimal C/N (10-90 g/g) each with different units Liu et al, Marchaim, 1992). Because 30 is a commonly cited value, for the purpose of discussion and reference, this paper assumes 30 g C NA /g N is the optimal C/N ratio.…”

Investigation of Nutrient Feeding Strategies in a Countercurrent Mixed-Acid Multi-Staged Fermentation: Experimental Data

“…For countercurrent mixed-acid fermentations, no models currently exist that describe nitrogen behavior. For similar fermentations (methane and hydrogen), the literature cites a wide range of optimal C/N (10-90 g/g); 30 is the most cited optimum for producing carboxylic acids [24,29,30]. Because the C/N ratio is reported in a variety of units and there are conflicting scopes of research, a new study should be done to determine the optimum C/N ratio for mixed-acid fermentations.…”

“…In biomethane fermentations, the carbon-nitrogen (C/N) ratio influences performance [17,29]. Too much nitrogen may result in ammonium toxicity [30,31], and too little nitrogen limits cellular activity; therefore, nitrogen control is necessary for optimum performance.…”