Updated: July 2002

1. Summary

There are various types of wastewater discharged from food processing industry because the number of raw materials, processes and types of products involved in the industry are enormous. The content of wastewater and its concentration as well as the volume of wastewater large vary with the type of wastewater. Thus, it is difficult to generally discuss waste-water from food processing industry. Most types of wastewater require BOD reduction because they contain organic matter represented by starch, sugars and protein. The decomposability of BOD content, however, differs with the type of wastewater. In some cases, SS content and oils are also contained in wastewater. In addition, wastewater is discharged in different forms which is dependent on production system. Therefore, it is necessary to select the most suitable BOD treatment equipment from among various BOD treatment equipment with pretreatment equipment provided, as required, according to the type and volume of wastewater and the location of treatment facility because effluent standards differ from location to location.

2. Type and Feature

1) Activated sludge combined with fluidized media for high load operation: NEW GLUTTON 50^®
The retention of highly activated sludge with good settlability has been realized through the combination of porous media and aerobic bacteria. The equipment utilizing NEW GLUTTON 50^® can be operated under a high BOD load 20 to 50 times higher than that of conventional activated sludge process equipment. The following are the features of the equipment.
(1) Suitable for primary treatment of concentrated wastewater and also for treatment of wastewater to a level under which discharge to sewage system is allowed.
(2) Tank capacity and installation space are small since it can be operated under a high BOD load.
(3) Maintenance is easy because no sludge bulking occurs.

2) Sequenced batch reactor system
The equipment utilizing this process can prevent sludge bulking because the growth of hyphomycetes is inhibited through the temporary creation of anaerobic environment during batch activated sludge process. This type of equipment has both the simplicity of batch operation and maintainability. In addition, the operation can be conducted by any person, who is not qualified engineer, due to the dedicated control system developed for the equipment. The equipment has the following features.
(1) The equipment can be installed at low cost because no receiving tank is required, and also because the construction of the equipment is simple.
(2) Denitrification and dephosphorization can be conducted, to some extent, only by adjusting the operating condition.
(3) No sludge bulking occurs.

3) Multipurpose activated sludge process environment control system
The system is a hybrid equipment having such functions as sludge bulking prevention, denitrification and dephosphorization by means of the creation of partial anaerobic environment during continuous activated sludge process and also through the circulation of the more than required volume of returned sludge. The standard control system takes an operation pattern of Anaerobic Treatment - Aerobic Treatment - Sedimentation. The system can be applied to the modification of existing activated sludge process equipment for the prevention of sludge bulking and the treatment of N and P. The following are the features of the system.
(1) No sludge bulking occurs.
(2) Denitrification and dephosphorization can be carried out.
(3) Sludge excellent in solid-liquid separability can be maintained.
(4) The system can be easily added to existing activated sludge process equipment.

4) UASB system TROLL^®
The system has an upflow anaerobic sludge bed in which BOD decomposition and solid-liquid separation are performed by passing raw wastewater upward through its reactor packed with self-solidified granular biomass of anaerobic bacteria having a diameter of 1 to 3 mm. The equipment can be operated under a BOD load of 10 kg/m³ which is 10 to 20 times greater than that of activated sludge process. No aeration is required because of anaerobic treatment. The volume of excess sludge generated is one tenth of that by activated sludge process. In addition, no sedimentation tank is required, and generated methane gas can be utilized as heat source. Thus, it is an epoch-making treatment system. Especially, due to the special construction of the solid-liquid separation section, the growth of biomass and solid-liquid separation in the equipment is excellent. The following are the features of the equipment:
(1) Installation space is very small because there is no need of sedimentation tank, and because it can be operated under a high BOD load on unit volume of reactor of 10 kg/m³ or above.
(2) Running cost can be largely reduced because it does not require aeration and methane gas can be recovered as heat source, and also because the generation of excess sludge is one tenth of that by activated sludge process.
(3) The operation and maintenance are easy. A extended period of shutdown poses no problem when resuming the operation.
(4) Commissioning can be started within the day because the supply system of granular biomass has been established.