Sludge Blanket Response to Storm Surge in an Activated‐Sludge Clarifier

Abstract

use of the diluted sludge volume index (OS VI) in mUg, based on a diluted 30-minute settling test (DSV30) in percent (mUdL), in which the sample is diluted to give a settled volume of less than 30%. The settling velocity of an undiluted sample was correlated with the diluted 30-minute settled sludge volume in an unstirred I-L graduated cylinder. For return sludge, the OSV30 was determined as DSVI X C, where C is the solids concentration in percent.At the time of the report by Garrett et al. (1984), principal models used to relate the settling velocity to solids concentration were the power model used by Yoshioka et al. ( 1957) and Dick and Young (1972) and the exponential model used by Vesilind (1968). These models, respectively, are as follows:ABSTRACT: Aspects of operation and design for stonn flows at a 190-m 3 /h (1.2-mgd) dry weather design flow activated-sludge plant were tested. A significant plant enlargement allowed recycle of test clarifier effluent to the main plant versus discharge to a stream. Thus it was possible to test high overflow rates without risk of a permit violation.On-line monitoring showed that the return sludge concentration increase lagged approximately I hour behind the start of the storm flow. This required an adjustment of the power equation model used. Furthermore, when the overflow rate exceeded the settling velocity of the feed solids, the sludge blanket rose faster than the model prediction. This phenomenon required developing a new model to predict blanket behavior under various loading conditions. The new model allows for plant design to more accurately include a clarifier zone for storing solids during peak flows associated with rain stornlS. An exponential equation, fitted to settling data, was also used in the new model with test data for comparison. The exponential equation gave a low blanket prediction. Results are compared with those of other research for solids storage during peak flow. Waler Environ. Res., 71,432 (1999).KEYWORDS: activated-sludge clarifier, diluted sludge volume index, floc volume flux, sedimentation model, sludge blanket model, storm flow. and Where Vs Vs = a X Xi-" at X e-n'XXi (I) (2)

Validation and application of a simple model for circular secondary settling tanks

“…Therefore, abrupt changes in the operation, such as hydraulic overloads, cannot be modeled adequately. Similar deviations were also reported in the majority of models (Dupont and Dahl, 1995;Göhle et al, 1996;Chatellier and Audic, 1998;Joannis et al, 1999;Manning et al, 1999;Chatellier and Audic, 2000) revealing a general mathematical discrepancy in such conditions. Research is currently in progress to develop a more efficient, but still simple equation, for the calculation of X f involving the hydraulic characteristics of the SST.…”

“…The applicability of the model was further assessed with two data sets from the literature; (a) a set of average data from Watts et al (1996) and (b) a set of data from Manning et al (1999) obtained during hydraulic overloads induced by storm surges.…”

“…Steady-state operation was assumed to occur when the criterion of non-variable amount of sludge solids stored in the SSTs was satisfied. In addition, two more sets of data consisting of average and dynamic data from other researchers (Watts et al, 1996;Manning et al,1999) were used to demonstrate the general applicability of the proposed model. The plant operators measured Q i , Q r and H sb and effluent turbidity (practically X e ) in the four SSTs every two hours; X i and X r were measured every twelve hours.…”

Operating Charts for Continuous Sedimentation II: Step Responses

“…To investigate the monotonicity properties of T o we need to know more about u 2 , which is defined by (14). Note that g changes with the operating point, since q e does via s = (q u + q e )u f .…”

“…Nonetheless, the solids-flux theory is still used today with some success, see e.g. [11][12][13][14][15][16]. All consequences of Kynch's assumption are not yet examined.…”