In an MBR facility treating domestic WW, the DO content has decreased significantly. Do you have experience or articles published on this topic? How would high content of MLSS impacts the oxygenation and performance of the MBR system? Will industrial discharges say petrochemicals exacerbate oxygen transfer rate? Any practical hints!
In this MBR: How about the MLVSS, petrochemical contamination, DO profile and COD, BOD removals? (also aeration method?).
When the MLVSS is too high (lets say, 10,000 mg/L) conventional aeration may not able to fulfill the Oxygen demand. Hence, usually MLVSS is maintained below that level.
For lower amounts of petrochemical contamination (~1 mL/L), there is no significant effect on air transfer.
The relatively high MLSS and small reactors associated with MBRs require that more oxygen be transferred per unit reactor volume. However, oxygen-transfer kinetics may decrease with increased MLSS concentration and viscosity. High viscosity can reduce the interfacial area for oxygen transfer by increasing the rate of bubble coalescence. In fact, several MBR studies reported that oxygen demand can exceed the volumetric capacity of the aeration system at high MLSS concentrations (>13000- 15000 mg/L). The influence of mixed liquor constituents on aeration capacity can be quantified by the alpha (α) factor. Because physical features and operating conditions of aeration equipment can vary, the relationship between MLSS and the α value is system-specific. For example increasing activated sludge MLSS concentration from 3 000 to 6000 g/L will reduce the aeration α from 0.77 to 0.59, resulting in 23% reduction in α.
Great and straight forward explanation with excellent scientific merit. I do agree with that and we are trying currently to register the impact of TSS increment on the DO content, aeration factors [ α values] can not be measured under filed conditions of large MBR systems [2000 m3/d]. Also I can assure that TSS ranged between 10-14 g/L, not possible to measure the exact impact [decrease percentage] on aeration capacity. May you suggest few references you published or read.
Thanks Ufuk, please use my Gmail account to send the refs: [email protected]. Best
Tamila: the MBR efficacy is NOT yet affected; effluent quality re: BOD/COD/Total N are ALL below 10 mg/L, amazing; despite zero DO content in the oxic zone and MBR units. May the denitirification [DN] process be not affected as they [DN] are facultative; BUT what about the first stage of NH4 oxidation [nitrification=NN], full DN means full NN. May Annamox be behind the full N removal, BUT we have no microbial evidence on that. This is something NEW for an MBR system working optimal under emergency conditions!!
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