The biological system of Bio-Cube applies a two-phase anaerobic process. The system includes two tanks: hydrolytic tank and fermentation tank. The structure of the fermentation tank is a modified anaerobic baffled reactor. The main micro-organisms in the fermentation tank are special bacteria which are researched and developed by Precise Energy.
Two-stage anaerobic process
The two stages of the anaerobic process are 1) hydrolysis and acidogenic stage and 2) methane production stage. The two-stage process allows a better environment for the growth and metabolism of the bacteria. It has several advantages over the conventional one-phase process.
Firstly, it allows the selection and enrichment of different bacteria in each phase. In the first stage, complex pollutants are degraded by acidogenic bacteria into volatile fatty acid which are subsequently converted to methane and carbon dioxide by methane producing (i.e. methanogenic) bacteria in the second stage.
Secondly, the first stage protects methanogens from overloads, preventing pH shock to the methanogenic population.
Thirdly, based on the clear division of the two tanks, the hydrolysis tank will process the waste water into a more suitable substrate for the fermentation tank to produce methane. The toxic substance in the waste water will also be diminished and eliminated in order to reduce the harmful effects to the methanogenic bacteria and to stabilize the operation of the system.
Highly efficient anaerobic fermentation process
The Anaerobic Contact Process (ACP) is applied in the Fermentation tank of the Bio-Cube. The ACP is developed from the conventional Completely Mixed Configuration (CMC), also known as Continuously Stirred Configuration (CST). A sedimentation tank is added to the fermentation tank to retain the bacteria and thus increase the bacteria concentration. This can improve the efficiency of the fermentation tank.
There are several advantages for the configuration.
- The configuration of the system is simple and the investment is lower than normal anaerobic digestion system, such as ABR, UASB. The running of the system is more stable while the system operation and the system management of system are easy.
- The completely mixed configuration is beneficial for maximum contact of the bacteria with the organic matters in the food waste, thus increasing the transforming speed of the organic matters and the efficiency of the fermentation process. The stirring process is based on multi-ports fluid influent. The mechanical stirring process can therefore be omitted and problems arising from such process, e.g. electrical failure of the stirrer, the mix solidifying during the transportation process can be avoided. The Completely Mix Configuration, together with the multi-port fluid influent, result in fewer dead corners in the fermentation tank, thereby increasing the utilization rate of the fermentation tank.
- The hydrolytic food wastes contain high concentration of suspended matters. The completely mixed configuration is a suitable form of treatment as the completely mixed configuration can improve the flow and the mixing of suspended matters in the fermentation tank, thereby preventing the sedimentation of the organic matters which if occured, may reduce the efficiency of the fermentation process. Moreover, the bacteria can adhere to the suspended matters to increase the contact area, thus, effectively isolating the organic matters.
- The matters in the completely mixed configuration are homogenized. The fermentation tank can be easily initiated resulting in high resistance to hydraulic shock and organic shock.
- The addition of the sedimentation tank, as opposed to just using solely the completely mixed configuration, can effectively hold most of the bacteria in the fermentation tank. Bacteria concentration in the fermentation tank is therefore increased, resulting in higher efficiency in the fermentation process.
Highly efficient bacteria group
The special bacteria, which are solely researched and developed by Precise Energy, are the main micro-organisms in the hydrolysis tank and the fermentation tank. The bacteria include some hydrolytic bacteria and methane producing bacteria (named as Methanogens). The high degrading efficiency of organic matters and methane yield are ensured by the existence of these bacteria.
The component of the food waste is complicated and the hydrolytic process will affect the methane yield of the food waste. So, special hydrolytic bacteria are added into the hydrolysis tank to increase the hydrolysis of the organic matters (Fig. 1 and Fig. 2).
Fig.1 The hydrolytic bacteria (1)
Fig.2 The hydrolytic bacteria (2)
The hydrolyzed organic matters (named as Volatile Organic Acid) are converted into methane in the fermentation tank. The special Methanogens (Fig. 3~5) are used in the fermentation tank in order to improve the conversion efficiency.
Fig.3 The methane producing bacteria (1)
Fig.4 The methane producing bacteria (2)
Fig.5 The methane producing bacteria (3)
