Ammonia Removal / Trickling Filter Solids Contact WWTP

[Sparky31]

First and foremost I would like to thank all of you that have participated in these forums. I often times perform searches on the internet and end up at an eng-tips.com forum.

I am currently working with a small village (~800 residents) that is having significant issues with their WWTP. We are currently working on a preliminary engineering report for the village to recommend possible upgrades or any retrofitting that may be possible.

The treatment plant consists of the following:

ADF: 150,000 gpd and PDF: 500,000 gpd or more

16’ Diameter Spirogester (settling tank/anaerobic digester)
50’ Diameter Trickling Filter (7’ rock media)
15’ Diameter Sprioflo Clarifier
Gas Chlorination and Dechlorination tank.
Recirculation is from the final clarifier to the head of the plant.

NPDES Limits: CBOD5 = 10 mg/l, TSS = 20 mg/l, and NH3 = 1.5 mg/l (summer) and 4.0 mg/l (winter)

The current average influent levels are: CBOD5 = 85 mg/l, TSS = 160 mg/l, NH3 = 16 mg/l.

The current average effluent levels are: CBOD5 = 10.5 mg/l, TSS = 19.1 mg/l, NH3 = 3.6 mg/l.

As you can see the village has been struggling with meeting their BOD, TSS and Ammonia NPDES interim limits, although they are very close with all three.

Given this information I would like to discuss the following:

1) The modification to a Trickling Filter Solids Contact (TFSC) treatment plant has been brought up. Initially, it appeared that this type of addition would give us the ammonia removal we are looking for, but after further research it appears that this may be a general misconception to the TFSC system. Please confirm or provide any information you may have in regards to TFSC systems for the additional removal of BOD, TSS and Ammonia. From my understanding TFSC is primarily used for additional TSS removal. Is this correct?

2) Discussion has also been made in modifying the existing plant by utilizing the existing T.F. and then providing an additional activated sludge process after the T.F. My question is what would the activated sludge process all entail? Would it have to be a complete packaged plant or is there something else I am missing? Another point I will have to consider is the deteriorating condition of the spirogester and T.F., so it may be that we can initially use the T.F. as a roughing filter, but eventually it may have to be taken off line because it would be beyond repair without spending a lot of money.

3) Any other suggestions for additional NH3 removal??

It seems to me there may be an increase in Ammonia from the anearobic digestor. Should we be recirculating to the head of the plant or just to the T.F.?

Thank you in advance!!

 

[bimr]

You have left out an important detail. What are the weather conditions?

Probably the only feasible option is some type of package plant considering the small flow that you have.

It probably makes sense to just install a new system rather then upgrade the old system.

 

[Sparky31]

Oh yes the weather. Looking at the monthly reports from the past 4 years the monthly average effluent temperature ranged from -2.2 C to 24.4 C with a daily min of -10!

With the never ending money problems with many of the villages we work for I didn't want to write off just building a new plant without checking out as much as I can first.

Let me know if there is anything else that would be helpful.

Thanks!

 

[bimr]

Based on the temperature that you are posting, it would probably be a good idea to stay away from a trickling filter. You have 2 things working against you. The low temperature and the trickling filter is going to reduce the temperature further.

You might want to investigate the vertical loop reactor from Siemens. It is an oxidation ditch type of process that has a small footprint.

http://www.usfilter.com/en/Product+...ts/envirex_products_vertical_loop_reactor.htm

 

[Sparky31]

I understanding that the T.F. will just continue to decrease the temperature of the water as is passes through and when we are recirculating it.

I will take a closer look at the VLR option and contact our Siemens rep. to see what he thinks. The Siemans rep. initially gave me information on an MBR option and is currently looking into an Integrated Fixed Film/Activated Sludge(IFAS)system to see if this would be applicable.

My other options at this point is an SBR plant and a Packaged Activated Sludge Extended Aeration plant.

I've written off a Carrousel sytem such as EIMCO b/c the flow would just not be adequate given the low BOD levels.

Many thanks!!

 

[bimr]

The MBR option is nice, but exceedly expensive. Unless you have to remove the TSS down to extremely low levels, and/or you have very tight siting requirements, it would be hard to justify.

I know that the old Envirex division of Siemens has all kinds of options. They can do a VLR followed by Membrane filtration or clarifier. They also have options regarding nutrient removal as well and can remove as little or as much as required.

I actually did a small VLR system with about the capacity that you are proposing.

 

[Sparky31]

Thanks bimr! Hopefully everyone will be off next week and I will be able to take a closer look at these options.

Happy Holidays!