Background: I bought parts for a reverse osmosis membrane filtration system on the internet and installed the RO system under the kitchen sink of my home in Scarsdale, New York. Please refer to video link of the assembly.
Type of Membrane: My RO system is comprised of sediment filters, activated carbon filters, an RO membrane, and a post-filter for additional water clarity. The RO membrane is a thin film composite (TFC) membrane made of polyamide (and it is produced by Dow).
Production capacity of permeate of the installation: 50 gallons per day design capacity. The membrane discharges into a tank filter (which I connected to the refrigerator for fresher ice). The flow rate is not uniform, and generally higher when the tank is full.
Permeate Quality: I got a TDS reduction of 97.73% (tested using my TDS meter). The municipal water in New York is pretty clear (from the Catskills Mountains, and further processed at local water treatment plants) with a TDS of ~44. The RO system was able to reduce the TDS to 1, which computes to a 97.73% reduction vs. stated reduction of 98%,
Recovery of the Installations: I directed the concentrate into the drain-pipe, and computed a concentrate concentration of 87 mg/L based on mass balance and a feed-to-permeate conversion of 2:1. Recovery (γ = Qp/Qf) = 50.0%.
| Q (Flow rate, gallons) | Concentration (mg/L) | Notes | |
| Feed | 2 | 44 | Measured |
| Concentrate | 1 | 87 | Computed |
| Permeate | 1 | 1 | Measured |
Operating Pressure: The RO membrane can work under a pressure of 30 to 120 psi. The operating pressure on the RO system in my house is ~65 psi (or 4.48 bar).
Concentrate Handling: As stated above, I directed the concentrate into the drain-pipe.
Next Steps/ Areas for Further Improvement in RO Design:
- The Concentrate stream is relatively clean with a TDS of 87ppm and can be recycled. I need to think of a clever way to recycle the stream into the RO at least once/twice till the TDS is of acceptable quality. The challenge will be to prevent against an iterative recycle loop.
- The permeate TDS of 1ppm may be too clean (and may impact salt balance in our body). I am thinking of adding a mineral filter.
- I am working on adding smart controls such as a smart faucet to remote-monitor the flow.
