Differences in soluble COD and ammonium when applying inverted phase fermentation to primary, secondary and mixed sludge

• Published in: Water science and technology 2015-10, Vol.72 (8), p.1390-1397
• Main Authors: Negral, L, Marañón, E, Castrillón, L, Fernández-Nava, Y
• Format: Article
• Language: English
• Subjects: Ammonium; Ammonium compounds; Ammonium Compounds - metabolism; Anaerobic conditions; Anoxic conditions; Biodegradation; Biological Oxygen Demand Analysis; Bioreactors; Chemical oxygen demand; Environmental science; Enzymes; Enzymolysis; Fatty acids; Fermentation; Hydrolysis; Laboratories; Phase separation; Primary sludge; Resource recovery; Separation; Sewage; Sludge; Ultrasonic imaging; Volatile solids; Waste Management - methods
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2015.351

Primary, secondary and mixed sludge were treated by inverted phase fermentation. This treatment results in solid-liquid separation of sludge after endogenous enzymatic hydrolysis (anaerobic conditions: 42°C, 48 hours). The soluble chemical oxygen demand (sCOD) was increased in the solid phase up to 1,800%, 21,300% and 260% in primary, secondary and mixed sludge, respectively. The corresponding increase in sCOD in the liquid phase accordingly reached values of up to 440%, 5,100% and 140%. Phase separation led to an enrichment of volatile solids in the solid phase (89-358% primary sludge, 80-102% secondary sludge and 29-133% mixed sludge). The NH4+-N values increased notably after the endogenous enzymatic hydrolysis itself. To investigate the short-term evolution following the treatment, the variation in sCOD, NH4+-N and solids was also monitored after keeping the hydrolysate at 37°C under anaerobic conditions for 24 hours. This stage showed no generalized pattern in terms of sCOD.