Team members: Sagari Datta, Shuchang Dong, & John Michael LaSalle.
The Problem : Risk hiding behind the splendid river bank
Combined Sewer Overflows (CSO) occur when rain overwhelms combined sewer systems leading to untreated sewage entering rivers. This can make the water unsafe for human contact and harms aquatic organism health.
The Schuylkill River in Philadelphia has been impacted by CSO problems and is currently under a consent decree by the EPA to improve water quality. Despite the Green City Clean Water program that began in 2011 to build green stormwater infrastructure in Philadelphia, the segment of the Schuylkill River that runs through Center City has not seen any reduction in overflow volume, frequency, or duration. Philadelphia Water provides information on the current quality of the river through its RiverCast.
Because of this we believe we should try to treat the outflows in the river through smart floating wetlands. The initial focus area for the project is the riverbank next to the Schuylkill River Park and Schuylkill Banks Boardwalk.
The Solution: What does Sew-kill do and why does it work?
Sew-kill has 4 objectives:
- Monitor water quality in the Schuylkill river
- Treat the water to improve the quality
- Educate Philadelphians about the river’s water quality
- Beautify the river edge.
Monitoring System:
Philadelphia Water has a single continuous monitoring station just upstream of the Fairmount Dam. This data was useful for establishing baselines, but we think that including water quality sensors at the installation is important because the Philly Water station is upstream of most of the CSO outflow points.
Through literature review, we finally decided to use a combination of three sensors (turbidity sensor, pH sensor, Conductivity sensor) as our monitoring system:
Floating wetlands have precedents as a response to CSO:
A review by the Auckland Regional Council of applications of floating wetlands found that s floating wetland system combined with a sedimentation was effective at reducing suspended solids, chemical oxygen demand, and total phosphorus, but did not affect total nitrogen because the vegetation mat created anaerobic conditions in the water underneath it.
Sew-kill uses three components to treat the water. A floating mat of wetland plants, activated carbon filters, and aeration.
The Prototype Model: Implement in the real world
The prototype comprises of two parts: (1) vegetation basin and (2) controller basin containing the sensor box and solar panels. As can be seen from the work flow diagram below, if any two of the three sensors read values that exceed the threshold values for bad water quality, the LED color will change to red and the aeration system will switch on. When the readings fall below the threshold values, the aeration system will switch off and the LED color will turn blue.
In the real world, the prototype will be arranged as modular units. Each unit will have the power source/controller basin in the center and multiple vegetation basins will surround the controller basin.
The basic structure of the vegetation basin and the controller basin are quite similar. Both basins will be circular in shape and will hold active carbon between two mesh layers. However, the top of the vegetation basin will comprise of a vegetation mat while the top of the controller basin will contain the solar panels and the sensor box. Furthermore, the aeration system will be attached to the bottom panel of the controller basin.
Another structure that is common to both the vegetation and the controller basin is the static filtration door located at the center of each basin. The filtration door adds resistance to the CSO water flow which in turn helps slow down the flow speed. This ensures that the amount of time the water flows through the filtration materials in the basins is prolonged.
Here is how the electrical wiring works!
You can also check out code used for this project on GitHub.
Estimated cost of a real world installation:
Our cost estimate indicates that our prototype is relatively less expensive when compared to many of the existing sewage purification installations.
Renderings
Next steps:
Based on the feedback we received, our next steps would involve finding out how our prototype would interact with the existing Schuylkill river infrastructure. In particular, we will need to research how the information generated from the sensors can be transmitted using the LoRa network.
We also got feedback on how our prototype could function as an educational placemaking feature along the Schuylkill river banks in addition to being a water filtration system. This is something we would like to explore as well.
We also plan to include a cost-benefit analysis to our existing cost estimate. We would first need to determine the CSO outflow volumes a real world installation of our prototype would be able to handle. Based on this figure, we would then have to calculate the economic benefits gained from a Sew-kill installation and perform a comparative analysis with the our existing cost estimates.
Prototype demo:
Look at our video to find out how the LED respond will respond to the water quality!
THANK YOU!