Sand filters after WW ponds? 1

[sjohns4]

Hi all,

I have a small wastewater treatment systm I've been working with on and off for a while now. The The existing system is an aerated lagoon with two manually alternated, shallow, non-aerated settling ponds prior to chlor/de-chlor and surface discharge. The reciving stream recently got hit with very low effluent limits (5/3 - BOD/NH3-N, TSS report only).

The average effluent concentrations since some minor repairs to the damaged blower piping have been 14-BOD / 8-NH3-N, which seems prety good for a lagoon system. However we've got to meet those tight limits in the permit. (The NH3-N concentrations have historically been quite high this time of year, during the rest of the year they're typically much lower)

I was thinking of something like an intermitent/alternating sand filter system. The bit of info I found on those were referencing their performance after a day or few residence time in an anaerobic environment (septic tank); therefore, the influent on the filters was still reasonably strong. I'm somewhat concerned that by using one in our situation we would not have strong enough influent to the filter to promote the growth of suitable biomass.

Does anyone have expirence in using or designing sand filters in a similar situation? Otherwise are tehre any good references someone could point me too?

Thanks,

Mike

 

[nackra]

http://www.ipcb.state.il.us/documents/dsweb/Get/Document-12042/

370.940 Intermittent Sand Filtration for Secondary Treatment

 

[ckeller]

Have you considered converting one or more of the shallow ponds to a treatment wetland? You may be able to knock both the BOD and NH3 down and should also control TSS as long as it is properly vegetated and not allowed to run too deep.

 

[sjohns4]

Actually I had not, that would be very cool if it would work though...be a good project to market too.

Do you know of any good reference materials for evaluating & designing such a system?

 

[ckeller]

Treatment Wetlands, 2nd Edition by Kadlec and Wallace (2009) covers it all in terms of a wetland design reference. I know that there have been several successful pond to wetland conversions in the US for purposes of reducing effluent nutrient and TSS concentrations.