What is called "slow sand filter" in drinking water treatment is also primarily a biological process (google for "schmutzdecke"; yes that term is used in English too). I therefore doubt that it would work for treating OMWW.

Here is a good overview chapter on the OMWW issues at hand and possible treatment options:
fabe.gr/images/stories/KEFALAIA/1.pdf

Seems like it is a problem with much active research going on, but so far little suitable (low-cost & low maintenance) treatment solutions.

Hi Christoph,
thanks for your reply. Yes, co-digestion is one of the options I am looking into.
However, adding OMWW without pre-treatment into small domestic WWTPs seems a bit risky. The pond will help a bit, but I would like to further reduce TS and increase pH through sand filtration.
There are tons of publications on OMWW treatment around, but I couldn't find a a single suitable solution for decentralised, small-scale applications that tested positiv and is affordable for small olive oil producers. There is nothing in Jordan so far either.

The sand filter would be simple to build and operate. Clogging should be avoided by alternating applications on 3 or more beds, and drying periods in between (you agree?). But since there is no real-life experience on this approach for OMWW, I am a bit hesitant.
We are working here on a conceptual study only, but our proposal should nevertheless be realistic.

thanks a lot for your useful posts!

Hi Frank,
Spontaneously I would look into an anaerobic CO-digestion. I don´t have own experience, but here are some references in the web as well.
But I´m almost sure you looked in that direction. If yes... why didn´t you find is suitable?

Yours
Christoph

There is also an EU funded project on this topic called MEDOLICO

www.medolico.com/

Hello Frank, have you tried discussing this with academics at Yarmouk University in Jordan? It sounds like they have looked into this before: see this article called "Low Cost Treatment and Disposal of Olive Mill Wastewater"

www.envirotech-online.com/article_read/284/

Dear all,

wastewater from olive mills (OMWW) is a big headache in many countries around the Mediterranian Sea and in the Near East.

OMWW’s basic characteristics prove its ‘‘strong’’ nature, featuring:
• Strong offensive smell,
• extremely high degree of organic pollution (COD values up to 220 g/L),
• a COD/BOD ratio between 2.5 and 5 (hardly degradable),
• pH between 3 and 6,
• high content of polyphenols (up to 80 g/L) which are not easily biodegradable and toxic to most microorganisms,
• high content of solid matter (total solids up to 20 g/L).


On a larger scale, OMWW can surely be treated by sophisticated treatment technologies, requiring very skilled O&M staff and a lot of energy.
This is obviously not a solution for the many small-scale olive mills in rural areas as prevailing in Jordan, where I am currently working.
For smaller, decentralised applications, it seems there are only 2 options:

- storage and evaporation in designated lagoons,
- Co-treatment in domestic wastewater treatment plants (share not exceeding -say- 5% of the total volume)

For applications in a decentralised context on village level, I am thinking about a solution as follows:

storage / evaporation (reduction of volume through evaporation, and COD reduction through phase separation) --> slow sand filtration (removal of solids and hence further reduction of COD) --> co-treatment in a decentralised WWTP (at very small input rates).

My question:
Does anybod have experiences with that kind of slow sand filtration systems? It is basically supposed to treat settled raw wastewater. I am aware of the fact that slow sand filtration is usually applied in drinking water processing, but there are obviously also applications for WW treatment around. (Vertical Flow CW or comparable solutions are NOT possible do to the toxic nature of the OMWW).
Or are there any other solutions around that might be suitable for small-scale solutions in rural areas, with limited O&M resources in terms of personnel and finances?

Thanks for your considerations
Greetings from Jordan
Frank