If I choose a chemical sewage treatment plant what should the idle unit operations?
Screening, Equalization, coagulation and flocculation, sedimentation, filtration, and post aeration
need to add or remove any more?
Dear Proban
I hope you know the steps of wastewater treatment processes. First use screening, second use coagulation, thirdly or finally use filtration or adsorption process (activated carbon).
The standard processes are
1. Screening
2. Equilization
3. Primary Sedimentation
4. Secondary Biological Treatment that includes aeration
5. Secondary Sedimentation
6. Tertiary Filtration
7. Disinfection by UV or Chorine
8. Most of the sludge from secondary treatement is recycled to Aeration process as activated sludge.
9.Remaining sludge is sent to sludge holding tank then digester or drying beds before disposal
For oxidation ditches primary sedimentation and equilizatuon are not required.
Modified process for secondary treatment involves reactions in separate or same reactors for anaerobic, anoxic and aerobic reactions. Membrane type technologies such as Membrane Aerated Biorectors ( MABR) by Fluence utilizes all three (3) reactions in one reactor in the secondary process. For MABRs no primary sedimentation is required however equilization is needed. Upflow Sludge Blanket Filtration (USBF) utilizes the same conditions and procesess as MABR.
If neutrient removal for your processes are critical I would suggest a secondary treatment option that reduces phosphorus by anaerbic reactions and nitrates by anoxic reactions. Further precipitation of phosphorus may be neccessary where alum is added during the secondary sedimentation stage before disinfection. Hope tbis helps.
Hope this helps.
Indeed, I agree with the Vicky and Fikiru replys for the stages of the wastewater treatment processes. 1st- screening, 2- coagulation, flocculation, 3- adsorption onto activated carbon which according to studies gives the best yields and finally end with disinfection (sodium hypocrite or UV).
However, it's also necessary to specify whether this wastewater is of industrial or domestic origin?
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