The variables were hydraulic retention time (HRT) (6 14 h), the diameter ratio of internal and external column (Din/Dout) (0.3 0.7) (corresponding to 10 1 as surface area of downcomer and riser ratio), and dissolved oxygen (DO) concentration (0.5 3.5 mg/l).
Results of the long-term operation of the system showed that, both reactors provided up to 85% P removal and recovery over wide ranges of aeration times (1.0 4.0 h), hydraulic retention times (HRT) (6.0 15.0 h) and temperatures (0 29.5 °C) for an extended period of 247 d, in which approximate 30% of P was recovered by the struvite accumulation devices.
Due to nicotine's tendency to fluctuate and relatively short half-life (~2 h), cotinine, its major (~70%) metabolite with a longer retention time (~18 20 h) is preferred [11].
d (hydraulic retention time [HRT]=10 h) and 0.7 g CODt/L.
The OSA and TCS combined processes reduced sludge yield by 21 56% under the same sludge retention time (6.75 h) in sludge anoxic holding tank.
Figure 5 shows the length and diameters of top end and bottom of ZnO microrods at the retention time 0 6 h.
To obtain the optimum condition for diazinon biodegradation using RSM, input parameters included the initial concentration of diazinon (0.01 10 mg/L), concentration of S. cerevisiae (0.5 5%), pH (4 10), and retention time (1 30 h).
Regression analysis between mass nitrogen reduction and theoretical retention time (7.5 79 h) suggested minimum design retention times should be increased, though caution was also issued about this as increased design retention times and corresponding larger bioreactors may exacerbate detrimental by-products under low flow conditions.
The effects of inlet nitrate concentration (50 800 mg L− 1), retention time (2.5 24 h), waveform magnitude (0.1 9.6 Vp − p), adjustable direct current voltage added to offset voltage (0.1 4.9 V), alternating current frequency (10 60 Hz), and waveforms (sinusoidal, square, and ramp) were studied in this work.
Bacterial cells were allowed to settle for 6 h before the flow was restarted (with a mean hydraulic retention time of 2.5 h).
