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Membrane BioReactors Primer Need to know more? Send us an email or feel free to search our online series with our give away search engine: |
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Let's calculate an estimate of the required solids retention time for a small petroleum refinery stream containing benzene (1850 ppm -> COD = 1850* 3.08 = 5700 mg/L). Please be aware that these calculations are a simplification of the actual project data. For example, actual solids inventories could be smaller or larger and all other derived magnitudes adjusted accordingly. SRT is thus about ballpark.
| SRT Sludge Age Sizer | ||||||||||||
| T | 25 | °C | ||||||||||
| Yoc | 0.5 | Petroleum Refinery Stream | ||||||||||
| Kd | 0.250 | (also called b) | Stream containing about 1850 ppm benzene | |||||||||
| Carbonaceous Removal Sludge Age | ||||||||||||
| flow in | 240 | m3/d | 0.063 | mgd | ||||||||
| CODin | 5700 | mg/L | 3011 | lbCOD/day | 1366 | kgCOD/day | applied | |||||
| 0 | kgCOD/day | via denitrif | ||||||||||
| 1366 | ||||||||||||
| Percent | 100 | % Treated | 1366 | kgCOD/day | ||||||||
| Percent | 98 | % COD removed | ||||||||||
| Vreactor | 190440 | gallon | 721 | m3 | (from order of magnitude sizing) | |||||||
| 0.19044 | mg | 1.89 | kg applied COD/day per m3 | (Residual OK) | ||||||||
| Target MLVSS | 1.89 | kg applied + from denitri COD d/m3 | ||||||||||
| 5320 | mg/L | 8439.463 | lb bugs | 3828 | kg bugs | total bugs in tank but say only | 100.0 | % heterotrophs | ||||
| 5320 | mg/L | 8439.463 | lb bugs | 3828 | kg bugs | (heterotrophic biomass) | ||||||
| SRT | 20.04 | days | (iterates automatically) | |||||||||
| Ync | 0.143 | ok | f/m | 0.357 | kg AppliedCOD d per total kg bugs (Residual OK) | |||||||
| f/m | 0.357 | kg Applied + From Dentir / total kg bugs | ||||||||||
| biomass yield = | 191 | kg/day bugs | due to appliedCOD | |||||||||
| HRT = V / Q = | 3.0 | days | ||||||||||
| 72 | hours | ok | ||||||||||
| Oxic chamber | |||||||||||||
| s.w.d. | 1.2 | m | MBR | ||||||||||
| Pilot Scale | |||||||||||||
| at 20°C and sea level | |||||||||||||
| wastewater flow | 1 | m3/day | kgCOD/day | ||||||||||
| COD in (mg/L) | 5700 | 12.6 | lbCOD/day | 6 | 25 | lbO2/day | at 2.0 lbO2/lbCOD | ||||||
| TKN in (mg/L) | 0 | 0.0 | lbTKN/day | 0 | lbO2/day | ||||||||
| AOR | 25 | lbO2/day | 1 | lbO2/hr | |||||||||
| oxic cell data | |||||||||||||
| length | 1 | m | |||||||||||
| width | 1 | m | tank volume | residence (days) | area (m2) | ||||||||
| s.w.d. | 1.2 | m | 1.2 | m3 | 1.20 | 1 | |||||||
| 3.9 | (feet) | 42 | cubic feet | ||||||||||
| alt. cir diameter | 1.1 | m | (in case circular tank is used instead - arbitrary to be later fine tune w/manufacturer) | ||||||||||
| lbCOD/day 1000 cu.ft. | 296.4 | MLVSS | 12000 | mg/L | |||||||||
| Fcod/Mlvss = | 0.396 | ||||||||||||
| 4.75 | kgCOD/day m3 | inventory | 32 | lb bugs in tank | |||||||||
| total residence time | 1.20 | days | Flux Rate | 24 |
L/m2 hr | 14.1 | GFD | 14 | kg bugs in tank | ||||
The reader may find that the overall treatment of the topic, i.e., the incorporation of micro- or ultrafiltration, has been excessively harsh or even critical. Part of this approach stems from the identification of projects based almost entirely on manufacturers' recommendations, be they aerators, membranes, diffusers, cooling towers, condensers of all types, rotating biological contactors (RBCs), incinerators, etc. History shows us that science is not always reflected in catalog information. With this caveat, i.e., caution, we gladly conclude this preliminary presentation of the topic by transcribing two internal communications from good-faith engineering firms:
"Membrane bioreactors are the future for both industrial and municipal wastewater treatment because they provide excellent reuse opportunities, particularly for water reuse. The primary problem, in addition to operating costs, is clogging of the membranes by bacterial excretions and debri, which translates to frequency of membrane cleaning." - Dr. C. W. Randall (Cliff)
"Membrane bioreactors are seeing a lot of research and application in the US, Europe, and Asia. Their major advantages is that they can remove bacteria and protozoa in drinking water applications. In wastewater applications, their major advantage is that the can separate biomass very efficiently and allow better control of biological reactor operation and performance. They are costly, but have a real appeal to some engineers." - Dr. J.C. Young (Jim)
Sample keywords: hydrogen sulfide EGSB tannery (no commas!)
