Incorporate anoxic/aerobic swing cells -BNR procees

[nilaypathak]

Hello,

WE do have BNR process at the plant. influent flow varies from 7000m3/d to 13000m3/d.
One of the operation brought up idea of changing on cell of bio reactor to swing zone as plant has significant season variation. I have been searching to good case study to identify the favourable conditions for the swing zone to further invest in the idea.
I am looking for pro and cons of swing zone based upon past experience.
My appreciated in advance for your valuable input.
Regards,
RS

 

[ashtree]

nilaypathak

Swing zones can be good for the seasonal application you are talking about but they must also be approached with caution.
You mention flows between 7 and 13 ML/day but you dont mention what capacity your plant is actually designed for.If the plant is actually only a 7 ML/day plant than you may not be able to "swing" any capacity.
A couple of other points to consider are:

1) What is your plant configuration now? BNR is a generic description only that covers a wide range of configurations. You may already have too much/not enough capacity in a part of your plant and swinging capacity may make the situation worse. I would start looking at this issue by calculating the volumetric loadings on each of the zones you now have and see how this compares to typical design guidelines quoted in a works such as Metcalf and Eddy
2) What are your typical influent conditions? COD, BOD, TN,TP, Ammonia, TSS
3) What are your effluent conditions? Do you have a licence or permit to comply with.
4) What are you trying to achieve with your swing zone? More throughput, better nutrient removal, lower power consumption.

One of the classic swing zone applications is in cold conditions particularly where there are different permit conditions for nitrogen during the winter and summer months. During the summer when reaction rates are faster and the nitrogen limits lower multiple anoxic zones might be used with mixing only as well as the normal aeration. However in the winter time with slower reaction rates but higher acceptable nitrogen limits one or more of the anoxic zones may be aerated as well as the normal aeration to give a greater aerobic mass fraction.But nitrogen removal may be significantly reduced.

In saying all this processes such as SBRs are the ultimate swing zone plant. By adjusting cycle times , aeration intensity , DO etc you can within the volumetric and control system limits of the plant swing the plant through differing "volumes" of anaerobic , anoxic and aerobic phases. If that is done correctly it can work quite well.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[bimr]

Here is a link to an example:

http://www.onewaterohio.org/docs/11...ng_Design_Construction_and_Startup.Talbot.pdf

 

[nilaypathak]

Thank you Ashtree and Bimr:

Intent here is energy saving and better nutrient removal.
Influent : BOD/PH/TSS/TP/Dissolved Orth/TAN = 167/ 7.6 / 165/ 3.6/2.2 /12.9
Effluent : BOD/CBOD/ph/TSS/TP/Dis Orth/TAN/TKN/No2+No3/TN = 2/3/7.5/2.5/.11/0.04/0.5/1.02/5.21/6.15

Bio reactor arrangement is ---Influent > Pre anoxic > Anaerobic cell> Anoxic cell 1>anoxic cell 2> Aerobic cell 1-2-3>secondary clarifier.

looking forward to hear from you.

Regards,

 

[ashtree]

nilaypathak

Looks like from a nutrient removal perspective you are doing pretty good, so i dont think a swing zone will be appropriate for that purpose.
Energy saving in a wastewater plant is very complex and its a lot more than just using things less or fitting energy efficient motors. There are lots of things you can do that might just give you a fraction more efficiency but if you can several of those small savings combined it can really add up.
Things like:
Reducing the amount of sludge produced through changes to anaerobic and anoxic mass fractions.
Changes in recycle and return sludge rates. Less pumping saves energy.
Is your aeration at the correct set point.
What is the most energy efficient way of running your aeration. This will depend on the type of system eg: surface , diffussed air, jet aerators etc.
Are there advantages in doing things at a different time of the day.

It is way too complex to work through the detail here. It takes lots of investigation and time to achieve but in doing so you will obtain an excellent understanding of the process.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"