Effect of SRT and temperature on biological conversions and the related scum-forming potential.

Sludge flotation was reported to cause several operational problems in anaerobic systems including UASB reactors treating both strong domestic sewage and some industrial wastewater. This research is to investigate the effect of anaerobic digestion on scum-forming potential (SFP) of sludge and other physical-chemical properties. A simple test was developed to measure and compare the tendency of different sludge to form a scum layer. Results showed that anaerobic digestion affects chemical composition of sludge flocs and consequently, SFP, which was found to be inversely proportional to the degree of digestion (both SRT and temperature). It was suggested that higher protein concentration at elevated SRT and 25 degrees C increased the negative surface charge of sludge flocs and ,consequently, reduced the ability of sludge to attach to gas bubbles and float. Floc average size increased with increasing SRT and temperature, especially for sludge with 75d SRT at 25 degrees C. On the other hand, settling properties of sludge were negatively affected by increasing SRT to 75d at 25 degrees C. Filterability had a strong positive correlation with average floc size, but also polymeric constituents correlated positively with filterability at 25 degrees C.

[1]  P. Lant,et al.  Impacts of morphological, physical and chemical properties of sludge flocs on dewaterability of activated sludge , 2004 .

[2]  T. M. Keinath,et al.  Influence of particle size on sludge dewaterability , 1978 .

[3]  G. Zeeman,et al.  The role of sludge retention time in the hydrolysis and acidification of lipids, carbohydrates and proteins during digestion of primary sludge in CSTR systems , 2000 .

[4]  H. Lemmer,et al.  Scum actinomycetes in sewage treatment plants—Part 2 , 1988 .

[5]  P. Vesilind,et al.  Limits of sludge dewaterability , 1997 .

[6]  Gatze Lettinga,et al.  Anaerobic Sewage Treatment: A Practical Guide for Regions with a Hot Climate , 1995 .

[7]  A. E. Greenberg,et al.  Standard methods for the examination of water and wastewater : supplement to the sixteenth edition , 1988 .

[8]  Nidal Mahmoud,et al.  Anaerobic pre-treatment of sewage under low temperature (15 [degrees] C) conditions in an integrated UASB-digester system , 2002 .

[9]  M. Yoda,et al.  Controlling granular sludge floatation in UASB reactors , 1997 .

[10]  J. Ferguson,et al.  Solubilization of particulate organic carbon during the acid phase of anaerobic digestion , 1981 .

[11]  Keisuke Hanaki,et al.  Prevention of Lipid Inhibition in Anaerobic Processes by Introducing a Two-Phase System , 1991 .

[12]  P. Lant,et al.  The influence of key chemical constituents in activated sludge on surface and flocculating properties. , 2003, Water research.

[13]  W. Sanders,et al.  Anaerobic hydrolysis during digestion of complex substrates , 2001 .

[14]  D. Armstrong,et al.  Foam Flotation Enrichment of Enantiomers , 1994 .

[15]  J. Rubio,et al.  Primary treatment of a soybean protein bearing effluent by dissolved air flotation and by sedimentation , 1995 .

[16]  Grietje Zeeman,et al.  The role of anaerobic digestion of domestic sewage in closing the water and nutrient cycle at community level , 1999 .

[17]  S. Sayed,et al.  The performance of a continuously operated flocculent sludge UASB reactor with slaughterhouse wastewater , 1988 .

[18]  Krishna R. Pagilla,et al.  Causes and effects of foaming in anaerobic sludge digesters , 1997 .

[19]  Jörg Schwedes,et al.  Anaerobic digestion and dewatering characteristics of mechanically disintegrated excess sludge , 1997 .

[20]  Indu Mehrotra,et al.  Treatment of wastewater from slaughterhouse by DAF-UASB system , 2000 .

[21]  P. Lant,et al.  A comprehensive insight into floc characteristics and their impact on compressibility and settleability of activated sludge , 2003 .

[22]  A. James,et al.  Destabilisation of oil-water emulsions and separation by dissolved air flotation. , 2002, Water research.