B4B project adopt an innovative rotating biological contactor capable to increase anaerobic digestion efficiency reducing maintenance costs and energy consumption. Archimede system is based on rotating biological contactors (RBCs) exploiting fixed biomass process including low energy consumption, simple operativity and good capacity to withstand shock loading. “Archimede Rotors” represents advancement in the state of the art in comparison with existing equipment for several reasons as described below. Even if the main application of RBCs is for aerobic processes, B4B project adopt fixed film has for producing Biogas through anaerobic processe. The two-Phase anaerobic digestion has the advantage to create microenvironment existing between the medium and the liquor determining the activity and functionality of a fixed biomass system. RBCs “Archimede Rotors” will allow a better control of several parameters avoiding
- Getting the largest surface to volume ratio
- Helping mass transfer through the biofilm
- Promoting biofilm renewal with proper turbulence
- Enhancing operative flexibility
- Reducing energy consumption.
In Fig. 1 front and lateral sights of the novel contactor are shown.
Unlike conventional RBCs the novel contactor does not require mechanical powering. Rising to the surface, the gas fills the channels not only to induce the rotational thrust, but also to promote an efficient gas-liquid exchange through the whole body of the contactor. Due to the special arrangement of channels, gas blowing can take place in the best conditions. When operating in aerobic conditions (Fig. 2) the tank is open and air is the gas inflated while – when operating under anaerobic condition (Fig.3) – the tank is closed and the inflated gas is oxygen-free. As an example, it is possible to employ the nitrogen evolving from denitrification, or biological gas evolving from methanogenic processes.
The novel contactor carries on many benefits in the field of fixed-biomass systems. Many drawbacks limiting the well-known performances of the existing contactors arc eliminated. Running of the novel contactor is obtained or anaerobic conditions: hence the denomination “gas-driven rotating biological contactor” (GDRBC). It differs from conventional contactors featuring mass transfer rates near the theoretical limit, even at different operating conditions. In summary, these are the advantages:
- It can operate in both aerobic and anaerobic processes;
- While operating in aerobic mode larger amount of oxygen is supplied to the biofilm;
- At any rotation speed an efficient mixing action of the suspended solids is achieved;
- A lighter and cheaper construction is used because it is not necessary to support high torque typical of mechanical-driven RBCs;
- Due to simple manufacturing it can be structured with different diameters or lengths in order to adapt it to any process requirement and for convenient partition in stages;
- Speed rotation is not limiting, but can be adapted to different needs containing, in the same time, energy consumption;
- When a multi-stage arrangement is necessary, it is possible to operate any stage under independent conditions, optimizing single stage performance;
- Energy consumption is optimized modulating the gas flow according to the organic load;
- An easier accommodation is possible when updating existing water treatment plants.
- Maintenance is extremely reduced.