Updated: July 2002

1. Outline of Equipment

This is a waste water treatment system for low to high organic waste water called EGSB ( Expanded Granular Sludge Bed ) , high-loading type of the UASB (Upflow Anaerobic Sludge Blanket). Fig-1
The organic waste water is firstly led to the conditioning tank where the BOD compounds are degraded to volatile fatty acids (VFA). Both the temperature and the pH are also adjusted there. Then the waste water is introduced the lower part of the reactor via well-designed distributor nozzles, going up with some high velocity and discharged from the three phase ( Gas-Solid-Liquid ) separator: settler at the upper part of the reactor.
A lot of the anaerobic granular sludge is present in the reactor and degrades the VFA to CH4 and CO2. The section of the Biobed^® reactor is designed smaller compared to the one of the UASB reactor, resulting in the high upward velocity of both the gas and liquid. That helps the granules move easily and improves the performance.
The energy recovery can be possible from the gas produced by the way of a boiler or a fuel cell etc.
The system is fully closed so that an odor treatment is not needed and it has an advantage to a corrosion problem.

Fig-1

2. Characteristics

In the EGSB system as well as the UASB system, the main feature is applying of the anaerobic granules and the settler that prevents them to wash out from the reactor. The settler is the most remarkable feature of the Biobed^®. It was developed through the hydraulic studies of view to sustain the high upward velocities of both the water and the gas . Fig- 2
1) Multiple baffle system
The multiple baffles are installed at the lower part of the settler to guide the gas away from the settling compartment. The circulating stream occurs around the gas baffles by the effect of gas-lift theory. In the Biobed^® system, the reactor is designed to be high upward velocities. However just single baffle can not control bringing the gas into the settling compartment against the high stream. It's proved that multiple baffles can solve this phenomenon.
2) Energy dissipation chamber
The water coming from the baffles has to leave the reactor via the settling compartment. The way the water is introduced in this compartment is crucial and prevents the granules to settle. The energy dissipation chamber takes out the energy and makes an easy settlement of the granules.
3) Settling Compartment
The steep angle promotes an easy settlement of the granules. The shape of this compartment makes the upward stream uniform and there are no local areas where the upflow velocity is higher than the settling velocity of a granule. The granules can slide back through a thin boundary that can exist due to the laminar conditions in the settler.

3. Performance

Fig-2

The volumetric loading of the Biobed^® is generally 20 to 30kgCODcr/m³d for the waste from a food industry. The CODcr removal efficiency is 70 to 90% and the effluent can be discharged to the sewage. In the case of the discharge to a river, an aerobic treatment will be needed.
In the actual treatment of toxic formaldehyde, 8000mg/l in the influent could be removed to less than 20mg/l in the effluent. The plant has been operated well.

4. Adaptable field

The Biobed^® can be applied to following fields.
Food : Sugar, Beer, Vegetable & Fruit processing, Dairy, Candy, Beverage, Potato etc.
Fermentation : Yeast, Citrate, Ethanol etc.
Chemical : DMT, PBT, PET, PO etc.
Pulp and paper : Pulp, Recycle paper etc.