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RE: Lagoon denitrification

Joel B — Fri, 25 Jan 2008 15:35:02 GMT

Cain,
I would consider running all influent to 1st aerated cell, putting a skimmer outlet on first cell to retain solids to build up nitrifiers, having extra aerators in first cell and then alternating them so that when an aerator turns on it kicks up solids that had settled in that area previously. The goal would be to get the TSS up in the first aerated cell to as high as you can, to increase nitrifier population. In most lagoons TSS comes in at 200mg/l and due to settling is 50 mg/l at the outlet. If you can keep it at 300-1000 mg/l in first total mix lagoon, you should nitrify just fine. Most likely, if you adjust aerators to keep DO just above 0 you will de-nitrify in the same lagoon, no need for the anaerobic lagoons with their odor issues. The downstream aerated lagoons will most likely not contribute to nitrogen removal at all due to no significant TSS in them. We can discuss this in more detail if desired, we have some experience with success with this approach.

RE: Lagoon denitrification

Wiff P — Fri, 11 Jan 2008 12:46:18 GMT

I'm not sure how cold it is where you are but could take a while to get going if you're only starting now in January so be patient. Also agree with recirc idea although could present a practical challenge in cold weather but if you can recirc even at 100% feed forward from last aerobic cell before settling that would likely be helpful in getting denitrification going. You don't mention influent condentrations or loadings but assume all this is with conventional municipal wastewater. Would watch DO concentrations in the different lagoons (will require sampling in various locations to really get a good handle on overall DO environment in each lagoon) but you'll want to check this to see if you're actually creating the right environment in each lagoon for both nitrification and denitrification.

Wiff Peterson

RE: Lagoon denitrification

TerryF — Mon, 07 Jan 2008 15:59:38 GMT

Cain,

In broad terms what you are proposing looks okay without doing the numbers. At the end of the day your results will depend on how big of a population of nitrifiers you can build up and being to maintain adequate aeration.

If your last cell is being used for settling , you will need recirculation up to the first cell to bring back nitrifiers. You don't say how big your last cell is but you should be careful about algae growth etc in that cell.

I agree with Jerry in that a filter might be worthwhile afterwards. Even an aerated rock filter outlet might be better than nothing.

Regards

TerryF

RE: Lagoon denitrification

Jerry — Mon, 07 Jan 2008 11:49:27 GMT

I would follow the existing lagoon with a Recirculating Sand Filter.

RE: Lagoon denitrification

Victor — Sun, 06 Jan 2008 22:21:27 GMT

Cain:

It appears that a resource for lagoon management is what you are looking for. In my honest opinion, the best online resource for lagoon information is www.lagoonsonline.com There is also a dedicated online forum.

Lagoon denitrification

Cain — Sun, 06 Jan 2008 19:48:54 GMT

Hi. Was wondering whether anyone had any experience or advice on achieving reasonable Nitrogen removal in lagoons?

We are looking at options to upgrade an existing lagoon. Our current thinking is to separate the lagoon into six cells in series. The cells would be an aerated cell with 2 days HRT, anoxic with 0.75 HRT, 2nd aeration with 2 days, 2nd anox with 0.75 days followed by a 3rd 1 day aeration cell and a large final cell for settling prior to discharge. We would split influent 50% to the first aeration cell, 25% to first anox and 25% to second anox.

The detention times are based on the full flow i.e. as only 50% flow goes to cell 1 the actual HRT for cell 1 would be 4 days. Aeration would be set point controlled using fine bubble diffusers.

We would also look at adding attached growth media to aeration cells to enhance year round nitrification. We are only looking for an effluent TN of < 15mg/L and there doesn't appear to be any limiting parameter in the influent. Influent flow is pretty stable. Any advice, experience or ideas very much appreciated.

Thanks