Home > Products & Services > Environmental Systems > Our Featured Systems > Hitachi High-rate Filtration System
"Hitachi High-rate Filtration System" uses a high efficiency treatment process, which tackles the problem of "combined sewage overflow control".
Combined sewage systems treat domestic sewage together with rainwater flowing through sewers. However, with increasing populations and urbanization, many existing systems become stressed when rain increases sewage volumes and flow rates.
Expanding existing systems are unfeasible as available land surrounding many existing urban sewage treatment facilities is limited. New technology needs to be more powerful, yet compact and flexible so it can be installed into existing facilities.
The "Hitachi High-rate Filtration System" is a compact primary treatment system that replaces the primary sedimentation tank in existing facilities to boost treatment rates with its higher removal efficiency.
It was developed by a joint research program with Tokyo Sewage Bureau.
"Hitachi High-rate Filter" is a space saving system so it can be installed in existing treatment plants.
The required water surface area of our system is 1/8 in fine weather and 1/20 (in-house comparison) in rainy weather when compared with conventional primary treatment systems.
Outline of System
"Hitachi High-rate Filtration System" removes suspended solid (SS) from inflowing sewage water with a floating porous filter media developed by Hitachi.
Inflowing sewage water passes through the filtration tank and SS is efficiently removed unlike a surface filtration sand filter but an all layer filter.
Therefore, inflowing sewage water with a high SS concentration, can be effectively treated to improve the quality of primary treatment water, and combined sewage overflow control can be achieved.
System flow
Features
- High-rate treatment in fine weather without a coagulant can achieve high filtration rate of 400 m3 / m2 per day.
- In rainy weather, a filtration rate of 1,000m3 / m2 per day can be achieved by adding a coagulant to raw water.
- High performance SS removal ratio of this system is greater than 60% in fine weather and 70% in rainy weather.
- This shows that this system has a high treatment performance compared with conventional primary treatment systems (in-house comparison).
- Low maintenance, as filter media can be back-washed by inflowing raw water.
Filter media
SS catched by filter media
Treatment process
Comparison with former system
| Gravity sedimentation method | At rain | ||
|---|---|---|---|
| At rain | At fine weather | ||
| Flow sheet | |||
| Filtration rate (m 3 /m 2 day) | 50 (surface loading) | 1,000 or less | 400 |
| SS removal ratio (%) *1 | 40 or less | 70 or more | 60 or more |
| Coagulant dosage (mg/L) | None | 1-2 | None |
| Back wash | - | once every three hours | 2-3 times/day |
| Combined sewage overflow control | Impropriety | Acceptable | |
| Comparison of treatment plant area (%) | 100 *2 | 40 (Include utility area.) | |
- *1
- SS concentration of inflow raw water is to be 200mg/L
- *2
- Gravity sedimentation is assumed to be 100
Hitachi High-rate Filtration System Image
Demonstration
Layout
| Method of treatment | Up-Flow filtration | |
| Perone block | Treatment Capacity (m 3 /d) | Fine weather 122,000 |
|---|---|---|
| Rainy weather 334,000 | ||
| Filtration Rate (m 3 /m 2 d) | Fine weather 400 | |
| Rainy weather1,000 (coagulant added) |
||
| Number of tanks | 60 m 2 /tank X 8 tank | |
| Installation size (m) | Approx21.4W X 46.2L | |