Conventional wastewater treatment systems mainly use aerobic microorganisms to treat wastewater. However, this treatment incurs high costs to treat high-concentration organic wastewater discharged from facilities, such as food processing plants.
We, Toshiba, adopt a methane fermentation reactor with anaerobic microorganisms. By fully bringing out the excellent features of methane fermentation, our system efficiently treats high-concentration organic wastewater to achieve compatibility between environment friendliness and economy.
Wastewater Treatment System for Starch Factory
Wastewater treatment in starch factories carries a high burden of organic matter in raw water and needs to respond to the seasonal operations of the factories. Our system decomposes organic matter in low-pressure flotation treated wastewater in the UASB(*1) methane fermentation tank, and purifies it through nitrification, denitrification, and membrane separation. The system converts biogas produced during methane fermentation into steam in the boiler to effectively use it for starch production. Thanks to the biological desulfurization system, no pH adjuster is used in the methane fermentation tank and less desulfurizer is required for biogas, resulting in a significant reduction in chemical costs.
- (*1) UASB: Upflow Anerobic Sludge Blanket
- The top of GSS(*2) is open and its biogas outlet is not blocked by scum (film of residue floating on the water surface) or granules because biogas is recovered in the gas phase.
- A submerged weir is installed before the overflow weir to quickly precipitate granules without overflowing when the granules are lifted by the biogas and collide with the submerged weir to reduce the flow speed.
- (*2) GSS: Gas-Solid Separator
High-concentration Organic Wastewater Treatment System
We adopt UASB for high-concentration organic wastewater treatment systems. The high-concentration organic wastewater treatment system treats wastewater to the environmentally acceptable level and then discharges the treated water. The UASB methane fermentation bioreactor system achieves high economic efficiency and effective use of energy, as well as easy O&M(*3).
This system is suitable to treat wastewater with a high burden of organic matter (BOD(*4) concentration of 2,000 mg/L or more), which is, for example, discharged from food factories.
- (*3) O&M: Operation and Maintenance
- (*4) BOD: Biochemical Oxygen Demand It is the amount of dissolved oxygen needed by aquatic microorganisms to decompose and stabilize organic matter. It is an indicator of the degree of water pollution.
UASB Methane Fermentation Bioreactor
- Low power consumption
No power is required for aeration.
- Small excess sludge Approx. 1/5 to 1/10 of excess sludge produced by aerobic treatment is generated.
- Energy recovery The produced biogas can be used as power and heat sources.
- Small installation space Smaller space is required compared to aerobic treatment.
- Easy operation and shutdown It is suitable for seasonal and batch operation.
- No aeration system is required for aerobic treatment when methane fermentation can meet wastewater discharge standards.
- A smaller amount of excess sludge is generated, compared to conventional aerobic treatment, resulting in a significant reduction in sludge disposal cost.
- Thanks to high load design, fewer installation space requirements are needed.
Two-stage UASB System (Option)
In addition to the above-mentioned common features of the UASB system, the future prospects of our two-stage UASB system are described below.
- Our two-stage UASB system achieves even higher BOD removal rate than single-stage system (based on our investigation in 2013).
- It reduces sewage treatment costs, compared to the method to dilute the discharge water for single-stage methane fermentation (based on our own simulation in 2013).
We select a basic or two-stage system by taking into account both are suitable for the particular raw water quality and meet wastewater discharge standards.
Two-stage methane fermentation system
The two-stage system without aerobic treatment enables discharge of higher-concentration wastewater, for which the basic system cannot meet BOD discharge standards, to sewer only by methane fermentation.
When the BOD sewage discharge standard is 600 mg/L or less, this system can treat raw water with high concentration of organic matter up to 15,000 mg/L(*5) of BOD.
- (*5) The actual value may vary depending on raw water quality or other external factors.
With our expertise and rich experience in water and sewerage infrastructure development in Japan, we conduct business on a global scale.
We operate worldwide, and enhance capacity to provide the best solution to meet the needs of our clients.
We contribute to the creation of environmentally advanced communities with sustainable water infrastructure in response to regional, cultural and environmental requirements.