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Publish Ahead of Print Alert. Latest Issue Alert. New Content Alert. Close Modal. In both cases the occurring substrate gradient compensates the low loading of the wastewater and bulking sludge can be prevented.
A similar method of solution is found in the stage of biological phosphate removal in advanced wastewater treatment: Here the effect of the upstream, anaerobic mixing tanks is the same as of the selectors. Other methods to achieve a better settleability is bypassing the preliminary sedimentation, improving the wastewater characteristics of lopsided effluents or the addition of precipitants and flocculants.
An easier and less dramatic measure than adding constructive selectors or flocculants is supplying LennSludge. Please click here for further information on LennSludge. Filter presses for sludge treatment.
Toggle navigation. Home Library Sludge treatment filamentous organisms. The other side arm was sealed with two glass tubes connected to feed and effluent lines. The media for S. The volume of media in the chemostat was maintained at 1 L.
The dissolved oxygen DO concentration was kept above 2. Each chemostat experiment was run for at least three times the target mean cell residence time MCRT to reach quasi-steady state in the system. Flow rates were measured at the outflow volumetrically, and steady-state specific growth rates were subsequently calculated. The chemostat operational data are shown in Table S2 Supporting Information. PCR was performed in triplicate for each sample. S1, Supporting Information.
The operational conditions of the aeration basins and the performance data of these three WRFs are shown in Tables S3 and S4 Supporting Information , respectively. The WRFs were not experiencing bulking at the time of sampling. Each extraction was then performed, and each extract was subjected to triplicate PCR.
The primers are listed in Table 1 and primer design is discussed below. In all PCR runs, sterile water was used for each master mix as no template control. The expected size of the S. The serial dilutions were used as template for real-time PCR to generate a standard curve.
An additional DNase reaction was performed on-column during purification. After purification, samples were quantified Nanodrop, Thermo Scientific and serially diluted fold. The 22 sequences used for primer design are listed in Table S1. Regions that targeted all of the S.
The most specific primers were chosen Table 1. The primers were optimized for annealing temperature and other PCR parameters. Initially, the same set of primers was used for real-time PCR and to create the standard curves. However, overestimation of the standard occurred while creating the standard curves, which may be due to the insufficient amplification of the PCR binding sites. The same problem was also observed in another study when generating standards for PCR reactions Fey et al.
Thus, an additional set of primers Table 1 was designed to create RNA and DNA standards targeting regions upstream and downstream, respectively, of the real-time primers to avoid overestimation of the standard. Moreover, melt curve analysis on activated sludge samples North Cary WRF was performed by increasing the temperature 0. As the temperature increased, dsDNA denatured and became single stranded, causing the fluorescence dye to dissociate, and decreasing the fluorescence.
The negative first derivative of the fluorescence curve was plotted Fig. S2, Supporting Information. Thus, the primers did not target other organisms but S. The detection limits were 2 and copies for DNA and RNA, respectively, determined by using the calculation method in a previous study Smith et al.
Data outside these limits were considered to be below the detection limit of the assay. Error bars indicate standard deviation. The error bars in Fig. The larger error bars are likely due to the variability in the measurement of RNA, which was higher at the higher growth rate. The variability of the ratio requires that multiple samples have to be obtained and samples have to be taken frequently to observe reliable trends over time.
To evaluate if in situ growth rate of S. The overall decay coefficient b represents all death, decay, lysis and predation processes that in essence lower the overall growth in activated sludge. For the North Cary WRF, where the rRNA:rDNA ratio for one sample was higher than the maximum determined limit of , the ratios for the other two samples were within the range of the standards used in the chemostat experiments.
Assuming that the linear relationship between rRNA:rDNA ratio and specific growth rate applies to all possible growth rates, the in situ growth rate of S.
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