Biological hydrolysis and acidification of sludge under anaerobic conditions: The effect of sludge type and origin on the production and composition of volatile fatty acids

• Published in: Water research (Oxford) Vol. 42; no. 14; pp. 3729 - 3738
• Main Authors: Ucisik, Ahmed Suheyl, Henze, Mogens
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2008; Elsevier Science
• Subjects: acidification; activated sludge; anaerobic conditions; Anaerobiosis; Applied sciences; Biological nutrient removal (BNR); Bioreactors; bioremediation; biosolids; chemical oxygen demand; effluents; estimation; Exact sciences and technology; Fatty Acids, Volatile - chemistry; fermentation; Hydrogen-Ion Concentration; Hydrolysis; Other industrial wastes. Sewage sludge; Pollution; Sewage; sewage sludge; Sludge fermentation; solids retention time; Solids retention time (SRT); temperature; Time Factors; volatile fatty acids; Volatile fatty acids (VFAs); Waste Disposal, Fluid - methods; Wastes; wastewater treatment; wastewater treatment plants; Water treatment and pollution; Denmark; Europe; Biological nutrient removal (BNR); Volatile fatty acids (VFAs); Solids retention time (SRT); Sludge fermentation; Activated sludge; Legislation; Acidification; Volatile organic compound; Fermentation; Retention time; Sewage treatment plant; Biological purification; Hydrolysis; Batchwise; Anaerobe; Volatile fatty acid; Waste water purification; Reactor; Semicontinuous; Organic compounds
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2008.06.010

New wastewater treatment processes resulting in considerably reduced sludge production and more effective treatment are needed. This is due to the more stringent legislations controlling discharges of wastewater treatment plants (WWTPs) and existing problems such as high sludge production. In this study, the feasibility of implementing biological hydrolysis and acidification process on different types of municipal sludge was investigated by batch and semi-continuous experiments. The municipal sludge originated from six major treatment plants located in Denmark were used. The results showed that fermentation of primary sludge produced the highest amount of volatile fatty acids (VFAs) and generated significantly higher COD- and VFA-yields compared to the other sludge types regardless of which WWTP the sludge originated from. Fermentation of activated and primary sludge resulted in 1.9–5.6% and 8.1–12.6% COD-yields, soluble COD (SCOD)/total COD (TCOD), in batch experiments, respectively. The COD-yields for primary, activated and mixed sludge were 19.1%, 6.5% and 21.37%, respectively, in semi-continuous experiments operated at solids retention time (SRT) of 5 d and temperature of 37 °C. The benefit of fermentation for full-scale application was roughly estimated based on the experiments performed in semi-continuous reactors. The results revealed that even though the VFA production of primary sludge was higher compared to activated sludge, substantial amounts of VFA could be produced by fermentation of activated sludge due to the substantially higher production of activated sludge in WWTPs.