Wetland
There are two types of wetland in urban greenery for different purpose- Floating wetland and
Modular wetland
Modular Wetland
The modular wetland system is a self-contained treatment train that incorporates the following treatment processes: screening, hydrodynamic separation, media filtration, and a bioretention filter. The bioretention filter is an enhanced sub surface flow vegetated wetland with a special blend of sorptive media. This treatment train approach makes this system very effective at removing a wide range of stormwater pollutants.
The table below shows the pollutant removal performance of beach scale testing.
Pollutant |
Efficiency % |
TSS (Sil-Co-Sil 106) |
98% |
Dissolved Phosphorus |
22% |
Dissolved Copper |
93% |
Dissolved Lead |
81% |
Dissolved Zinc |
80% |
Oils & Grease |
84% |
Total Petroleum Hydrocarbons |
100% |
Turbidity |
93% |
Fecal Coliform |
66% |
E. Coli |
60% |
Testing of Quarter Scale Model is conducted at Flow Rate of 1.9 GPM. This flow rate is equal to 121.6 GPM for full size system.
The table below shows the full scale field testing result
Pollutant |
Efficiency % |
TSS (Sil-Co-Sil 106) (less than 15 microns) |
82% |
Nitrate-N |
76% |
Copper |
53% |
Lead (not present) |
N/A |
Zinc |
79% |
TPH - diesel |
100% |
TPH - motor oil |
100% |
Enterococci |
70% |
Fecal Coliform |
84% |
E. Coli |
79% |
This storm water filtration system can be used in many different configurations for new construction and retrofit applications. Available to accept variable pipe sizes or runoff directly from the built-in curb or drainage inlet this system can be used in most situations, regardless of site constraints.
Sizing
Calculation should be made to determine the appropriate water quality flow rate or water quality volume. Once this flow or volume is determined, the number of units needed for your project would be determined. This system also recommends decentralized treatment.
For larger projects multiple units will be needed to treat the water quality flow or volume. Decentralized treatment allows runoff to be treated at the source. This method is becoming preferred over end of the line treatment systems.
Depending on the most appropriate method for your project, the modular wetland system linear can be designed as both a flow-based or volume based. To determine which of the two is most appropriate, and analysis of project characteristics and specific treatment and flow control requirements should be properly analyzed.
Treatment Flow Rate
Peak Treatment Flow Rate = .27 CFS
Treatment Volume
Peak Treatment Volume = 4000 cubic feet
(requires pre-treatment and assumes 48 hour drain down time)
Flow Based Design
Typically, the water quality flow is defined as the flow of runoff produced by a rain event equal to at least two times the 85th to 90th percentile hourly rainfall intensity for the applicable area. The percentile and safety factor can vary by region and regulator.
Volume Based Design
Volume-based design can be designed to capture and then treat storm water runoff equal the Water Quality Volume (WQv). The WQv can be determined by the following method. Volume based design can be described as a capture, detain, and treat, discharge over an extended period (usually 48 to 72 hours).
Comparison
There are two main advantages of volume based design.
First, by detaining and then slowly treating and discharging over a period of 48 hours, you are creating a system that controls and attenuates flows. By doing so, this treatment system will not only satisfy treatment requirements, but also contributes to meeting all or part of the possible hydro-modification requirements.
The second advantage of volume based design is the 48 hour time period given to treat the WQv. The longer you have to treat the runoff the smaller the filtration system needs to be.
The only disadvantage is the cost and land required to detain the runoff in an above ground detention basin. Underground detention systems allow you to detain water without losing valuable space, though there are infrastructure costs associated with these systems. The value of the land will determine which of the two detention (above or underground) options are most feasible.
For more information, please contact us.
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Floating Wetland
Floating wetland park in singapore(will be completed in 2010)
more is coming...