Estimation of sludge sedimentation parameters from single batch settling curves

Abstract

AbstractÐIn this paper a comparison is made between two means of obtaining the parameters for the settling velocity models that are at the core of the solid¯ux theory: (i) the traditional approach using zone settling velocity (V ZS ) data obtained from a dilution experiment and (ii) a new direct parameter estimation method relying on a single batch settling curve (SBSC). For four distinct sludges, settling curves were recorded at dierent sludge concentrations (X ) and the Vesilind parameters were calculated in the traditional way. The value of the resulting model was evaluated by cross-validating it on its ability to describe complete SBSC's. Provided the dynamics of the sludge blanket descent were moderate a settler model incorporating these traditional Vesilind parameters could reasonably match the experimental batch settling curves. However, when the dynamics of the sludge blanket descent were fast, the Vesilind model failed. It was tried whether other settling velocity models could result in better ®ts to the SBSC. Here, the Cho model turned out to be the most eective one. When cross-validating the Cho model on the dilution experiment V ZS -data, however, it was found to be less performing than the Vesilind model in describing the relationship between V ZS and X. The fact that the Vesilind model is superior to the Cho model in describing such relationships, while the Cho model is better in describing complete settling curves, clearly points out that current settling models are still very empirical in nature. An important ®nding was that with all settling velocity models tested, practical identi®ability problems appeared, indicating the need for better experimental designs. Finally, the¯ux curves associated with the SBSC-estimated Cho parameters were compared with the traditional Vesilind ux curves. Although both types of¯ux curves generally showed similar trends, the reliability of SBSCbased¯ux curve predictions is at present insucient to warrant replacement of the traditional estimation of settling characteristics. # 1999 Elsevier Science Ltd. All rights reserved

A temperature‐gradient sensor for determining the activity of activated sludge

“…12 The temperature profiles of each probe primarily inform us of the metabolic heat production and the sedimentation characteristics of the sludge, which is helpful for predicting the effluent quality. 13 The sensor can also be applied to evaluate sludge quality. Sludge stored at 4…”

Experimental Methods in Wastewater Treatment

“…For example, if the solid-liquid interface shows a very rapid initial increase then additional measurements can be recorded during the first 2 min of sampling. If the appropriate specialised equipment and experience is available then the solid-liquid interface may even be tracked automatically (Vanderhasselt and Vanrolleghem, 2000). Depending on the concentration of the recycle flow sample, the standard dilution series (100, 80, 60, 50, 40 and 20 %) may not provide sufficient coverage of the concentration range for hindered settling.…”

“…Aerobic granules are spherical biofilms with a typical shape factor of 0.7 -0.8 (Beun et al, 2002). Whereas conventional activated sludge is characterized by settling velocities below 5 m h -1 (Vanderhasselt and Vanrolleghem, 2000), granular sludge settles significantly faster with settling velocities in the range of 10 up to 100 m h -1 Etterer and Wilderer, 2001;Winkler et al, 2012Winkler et al, , 2011a. Moreover, granules show a low flocculating tendency positioning their settling behaviour at the far left side of Figure 6.1.…”

Estimation of the batch-settling flux function for an ideal suspension from only two experiments

“…The dominant approach in this field has been to fit a simple functional expression with only a few parameters to batch (or sometimes continuous) settling data, usually some kind of sludge volume index, see Ekama et al (1997, Chapter 3) and the references therein. Later work also applies this methodology Dold, 1998, 1999;De Clercq et al, 2005;Giokas et al, 2003;Hasselblad and Xu, 1998;Lynggaard-Jensen and Lading, 2006;Renko, 1998;Suh et al, 2005;Vanderhasselt et al, 1999;Vanderhasselt and Vanrolleghem, 2000;Zeidan et al, 2003;Wilén et al, 2004). The most common functional expression relating the settling velocity and concentration is the one by Vesilind (1968); v s () = v 0 e −n , where v 0 and n are parameters to be determined.…”