If your system is overloaded it can help to add MBBR carriers and extra aeration. You get more capacity for the same tank volume. Do you experience biodegradable COD in the effluent?

Thank you Henrik

Effluent BOD is below the maximum allowable limit for wastewater effluent discharge to rivers. The HRT of the plant is about 8 hr. We need to work the plant with a lower HRT so that the  influent wastewater flowrate can be increased.

A pilot MBBR plant with capacity of 1 m3/hr  has been installed and fed by the same influent wastewater, after about 3 monthes there wasn't noticeable biofilm growth on the MBBR carrier.

Normally, MBBR could keep high biomass(MLSS) than AC process, so it is beneficial to undertake high strength wastewater under a lower HRT. While if the influent COD is lower than 200mg/L and well B/C ratio( biodegradable), I would like to recommend you the AC process because that is enough to fix this problem.

MBBR are better than activated sludge processes to avoid biomass washout.

You can operate the process as an IFAS (a hybrid system coupling suspended and attached growth)

Keep the organic loading rate above 10 gbCOD per m^2 per day (surface is referred to the actual colonizable surface of the carriers) and avoid excessive aeration, by keeping dissolved oxygen below 3 mg/L.

Examples of some industrial applications are listed in the links below, but many others are available. Please note: the links below are intended only as examples for your information; this does not imply any endorsement of the products nor of the Companies that are reported.

I hope these hints may help you.

http://www.krugerusa.com/medias/files/anoxkaldnes.htm

http://www.headworksinternational.com/biological-wastewater-treatment/IFAS.aspx

http://www.degremont-technologies.com/dgtech.php?article397

http://www.evoqua.com/en/products/biological_treatment/integrated_advanced_wastewater_systems/Pages/mbbr-ifas.aspx

In your pilot MBBR plant did you use a shorter HRT than the full scale plant. Did it achieve sufficient COD removal?

The HRT of the pilot plant was 6 hr. Less COD removal was achieved. It was clear to the naked eye that the growth of biomass was occurred mainly in the bulk solution not on the MBBR carriers. The pilot plant was operated by an expert wastewater treatment company.

Thanks for the description. It seems there is a problem in the initial attack of the biofilm on the surface of the carriers (MBBR chip). There is sometimes problems with initiating the biofilm on new carriers. Once the carrier ages biofilm can grow and function well. If you look in the bottom of my linked poster you can see how the biofilm should look on the carrier. The darkest one in the picture was exposed to 200-400 mg COD/L.

In pilot testing we have used carriers from an established plant. It seems biofilm adapt much quicker than it is extablished on new carriers.

I have heard of two procedures used to speed the attachment on fresh carriers. One is to soak the carriers in 1 or 5 mg/L KMnO4 solution before applying them to the biotank. The other is to pour thickened sludge (return activated sludge ~20 g SS/L) on the carriers and leave them for a week.

Poster Staged MBBR optimised for pharmaceutical biodegradation and ...