In 1986, we successfully applied the practical use of UASB method in the treatment of wastewater generated during the production process of isomerized sugar. Since then, the method was employed to various effluents and more than 70 UASB reactors were distributed both in the local and international industry.
1. UASB method
Our TROLL reactor, which employs UASB method, is illustrated in Fig. 1. Wastewater flows in from the lower section of the reactor. The anaerobic microorganism inside the reactor decomposes the inflow effluent, produces an upward flow of methane or carbon dioxide as decomposition product, and then agitation and mixture is gently performed. Simultaneously, this action effects granulation of the agitating mixture and the anaerobe.
Consequently, the anaerobe forms the sludge (Fig. 2), which forms into granules, and becomes a living group, which can be separated into solid-liquid phase. While wastewater is moving up through the granulated sludge formation layer, it undergoes more biodegradation and finally, it is discharged as treated water from the upper part of the reactor. The released gas containing methane is then used as source of heat and electrical energy.
2. The feature of the Super UASB TROLL
(1) Less operating power
Wastewater treatment using aerobic microorganisms requires a continuous supply of air, specifically oxygen in order to maintain activity, whereas anaerobic treatment operates in the absence of oxygen. Thus, in the anaerobic method, drastic reduction of running cost is possible.
(2) Easy operation management
Maintenance of appropriate temperature and pH can stabilize the operation. There is no need to control for aeration unlike the treatment by activated sludge. In addition, there are no difficulties in bulking.
(3) Less production of excess sludge
Lesser surplus sludge is produced by the anaerobic method as compared with the treatment by activated sludge. Especially, the UASB system among other anaerobic treatment processes, about １/5?1/10 less sludge is released.
(4) Simple structure
As shown in Fig. 1, the reactor has a very simple structure. There are inhalant canals for the wastewater and equipment for the separation of gas, liquid, and solid particles inside the reactor.
(5) High quality treated water
The BOD removal is more than 90%. Higher removal rate of more than 99% by effluent can be obtained.
(6) Collectable energy
Decomposition products by anaerobic treatment are mainly methane and carbon dioxide. Methane releases energy by burning, and by subsequent collection, efficient energy is salvaged.
(7) Quick start of equipment operation
After an inoculation source is input, treatment starts at CODCr volume load of 17 kg/ m3･d. On the ninth day, it reaches CODCr volume load 60 kg/ m3･d. The removal rate of CODCr is also beyond 96%. This feature is considered appealing.
3. Example of application to a food factory
The UASB system is suitable for processing wastewater from a food factory such as seasoning represented by bean paste, soy sauce, and vinegar; alcohol represented by sake, beer, and distilled spirit; pickles, etc. (Fig. 3)
Fig.3 UASB Equipment TROLL appearance
(1)Example of wastewater treatment from rice water washing
In a factory which mainly discharges wastewater from rice water washing, the amount of daily BOD is 5,550 kg/d. The components are starch, protein, oil, and large amount of SS. The CODCr concentration of raw water averages per month at 4,500mg/l. The meanBODconcentration per month is 2,500mg/l. Each removal rate is more than 80% and is stable.
(2) Example of wastewater treatment from bean paste manufacturing process
The main wastewater is bree from beans or streamed liquid. The BOD concentration is high at 20,000 mg/l. The entire effluent in conjunction with the water used for washing inside the factory often creates a BOD concentration of less than 10,000 mg/l. The water treated by the TROLL reactor is the entire effluent from a factory. The BOD concentration is 6,200 mg/l. The treated water through the TROLL reactor could be reduced to 150 mg/l. The removal rate is approximately 98%.
(3) Example of wastewater treatment from pickles manufacturing process
The mean BOD concentration is 9,000 mg/l in raw water. It is 13,000 mg/l in CODCr. It is treated down to 100 mg/l through the TROLL reactor. The removal rate of BOD reaches 98％?99.7％. Using the TROLL reactor, the BOD concentration undergoes treatment by the activated sludge for the final outflow. The BOD concentration is reduced to less than 20 mg/l. The treatment status for 12 months is shown in Fig. 4. The BOD volume load is 13kg/ m3･d. The CODCr volume load is approximately 19 kg/m3･d. The water temperature in the reactor in the range of 26-350C for stable processing of the operation is possible.
Fig.4The example of wastewater treatment from pickles manufacturing process