Sludge-retention times

In the conventional activated sludge process with biological sludge recycled from the final sedimentation clarifier, shown in Figure 27.11, the mean cell residence time or sludge retention time is... 

Tc Mean cell residence time, or sludge retention time, time (s)... 

In order to determine more precisely the fate of pharmaceuticals during sludge treatment, different experiments have been conducted in controlled conditions. In continuous anaerobic reactors treating sludge spiked with pharmaceuticals, Carballa et al. [114] observed removals higher than 80% for naproxen, sulfamethoxazole, and roxithromycin, while 40% and 23% of ibuprofen and iopromide, respectively, were eliminated at both mesophilic (37°C) and thermophilic (55°C) temperatures. For diclofenac and diazepam, elimination of about 60% was observed in mesophilic conditions while in thermophilic conditions, 38% and 73% of these two compounds, respectively, were eliminated. In these experiments, the sludge retention time (15 or 30 days) did not seem to influence pharmaceutical removal... 

Majewski M, Galle T, Yargeau V, Fischer K (2011) Active heterotrophic biomass and sludge retention time (SRT) as determining factors for biodegradation kinetics of pharmaceuticals in activated sludge. Bioresour Technol 102 7415-7421... 

The sludge retention time (SRT) is known as a very important operational parameter for color removal in SBR system. To obtain efficient color removal rate, adequate microbial population is desired. It was reported that 10 days SRT remained insufficient to obtain adequate population, and to ensure the color removal, SRT was increased to 15 day [2]. 

Kreuzinger N, Clara M, Droiss H (2004) Relevance of the Sludge Retention Time (SRT) as de-sign criteria for wastewater treatment plants for the removal of endocrine disrupters and pharmaceuticals from wastewater. Water Sci Technol 50 149-156... 

Conventional wastewater treatment plants (WWTPs) were not designed for an efficient APIs removal. The sludge retention time (SRT) is one of the crucial parameters, which influence on the design, operation and control of WWTPs. APIs can be divided into three major groups compounds with optimum SRT range for which their removal is the most effective (e.g., antibiotics and antiinflammatories), compounds on which SRT has no impact (e.g., anticonvulsants, p-blockers and hormones), compounds with visible influence of SRT on their removal rate (e.g., lipid regulators) [43]. 

These reactors were capable to decouple sludge retention time (SRT) from HRT, allowing the reactors to retain hydrogen-producing bacteria concentration at higher level. 

Mean cell residence time (MCRT), sludge retention time (SRT), or sludge... 

Huang H, Gui P, and Qian Y. Effect of sludge retention time on microbial behaviour in a submerged membrane bioreactor. Proc Biochem. 2001 36 1001-1006. 

In this study, the optimization of a WWTP control law by means of a multi-objectives genetic algorithm proved to be a reliable technique. To be feasible, this optimization however needs to be performed on a limited time horizon (typically two or three sludge retention times). This study showed that the addition of a long term simulation of final optimized settings allows the decision maker to check the quality of the results produced, as well as to have more insight into the performances of the control law. 

The hydraulic retention times (HRTs) of the activated sludge range from 4 hours to as high as 24 hours. With recirculation of sludge and wasting in the sedimentation tank, the suspended solids in the aeration basin are maintained at a concentration of 2,500 to 4,000 mg/L, while the sludge-retention times (SRTs) are between 10 and 30 days. 

Sludge retention time (SRT) BODS normalized load d 7.5 5.9 ( )... 

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