The Effect of Aeration Basin Configuration on Activated Sludge Bulking at Low Organic Loading

Abstract

Continuous-flow laboratory-scale activated sludge units were operated on domestic sewage at low F/M. In CSTR units at the F/M range of 0.05–0.25 g COD removed/g TMLVSS, day bulking did not occur with a weak (BOD5 = 139 mg/L) sewage feed and TMLSS = 1.5 g/L. Supplementation of sewage by blending with raw sludge produced a stronger sewage (BOD5 = 315 mg/L) which caused TMLSS to increase to 3.5 g/L. Bulking occurred in CSTR, 2, 4, 8, and 16 compartment units. An aeration basin with initial compartment l/32nd of aeration basin volume prevented but did not cure bulking. An aeration basin with initial compartments 1/74th of aeration basin volume, prevented and cured bulking. Anoxia in an aeration basin with two initial compartments each 1/64th of the total aeration basin volume did not aid in curing bulking. The SVI of sludges at low F/M (0.3–0.35 g COD removed/g TMLVSS, day) and high TMLSS (3.5 g/L) is related to conditions in the initial compartment rather than those in the remainder of the aeration basin. Initial compartment soluble COD, first-compartment F/M, and initial compartment size are important; floc loading, dispersion number and total number of aeration basin compartments are not important.

Assessing activated sludge morphology by laser and image analysis

“…The present data and those reported by Lee et al (1982) however show that SVI was less sensitive to TEFL in the Figure 8. SVI, TEFL correlation from Lee et al (1982) normal wastewater treatment plant operating range (indicated by the rectangle) an SVI above 200 would be debilitating for most activated sludge plants (Palm et al, 1980).…”

“…This requires further analysis. Figure 7 shows a plot and potential correlation between TEFL and SVI when measured over the range suggested by Lee et al (1982). Lee et al noted a linear correlation below SVI 200 and exponential when above (Figure 8).…”

“…Extended filament length beyond the floc is thought to reduce settlement by preventing compression and consolidation of activated sludge floc. Sezgin and Jenkins (1978), Palm et al (1980) and Lee et al (1982) have suggested using TEFL beyond floc to predict sludge settleability. The machine is simple to use for particle size measurements from 0 .…”

“…SVI, TEFL correlation from Lee et al (1982) normal wastewater treatment plant operating range (indicated by the rectangle) an SVI above 200 would be debilitating for most activated sludge plants (Palm et al, 1980). These results are expressed as the sum of the extended filament length (TEFL) and the Lee et al (1982) results show a sharp inflexion at 10 8 ìm of filaments per millilitre. As noted previously on discussion of floc size distributions, a large number of small filaments could introduce bias in the results.…”

Physical Characteristics of Activated Sludge Flocs

“…The densities of solutions where the floes do not settle are considered those of the floes. The idea was suggested and adopted in the experiments by Schoepfer and Zemke (cited by Mueller et al 33 ), Mueller et al, 35 Lagvankar and Gemmell, 103 and Ozturgut and Lavelle. 106 Mueller et al 35 measured the density of the activated sludge as a whole instead of each individual floe, as did the others.…”