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.

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.

E. coli happens!

Database Central

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

Wiff Peterson

Wiff Peterson