The first 1/10th inch of rainwater requires different treatment than the remaining 9/10th’s. Depending on the surface it initially falls on, rainwater quality can fluctuate. When it first touches the ground, it can collect oils, contaminants, and chemicals. However, as it continues to fall and flow over a surface, the cleaner it becomes. This is why the first 1/10th inch is so critical. We now have the technology to not only treat this initial rainwater but address other challenges as well.
For example, diverting rainwater has been a challenge for the Los Angeles area for some time. During a storm event, there is an influx of freshwater, known as clean water incursion, that can disrupt the wastewater treatment process, leading to an imbalance in the system. Thus, technology was developed to separate a portion of the rainwater and send it to the wastewater treatment plant while directing the remaining water to the groundwater recharge basins or ocean.
This technology is comprised of three key components: the detection device, pilot stations and valves. The detection device was created to identify when 1/10th of an inch of rainfall occurs. This amount of rainfall typically contains high levels of contaminants and bacteria, making it unsuitable for the groundwater basins and requiring treatment before being discharged into the ocean.
The pilot station operates in two modes: normal mode and divert mode. In normal mode, when it is not raining, the valve is set to direct the flow to the sewer system. An automatic timer opens the solenoid valve for 15 minutes every 10 hours. When it is raining and the pilot station is in divert mode, the valve directs the water to the appropriate stormwater management destination. Destinations being either the ground water recharge basins, ocean, or on-site retention for later managed release to the sewer system for treatment.
It's not just a big city like L.A. where this technology is applicable. For instance, in heavily trafficked patio areas of large residential or commercial buildings, where water runoff is diverted to the sewer system or the building's rain gutter system. Incorporating this water diversion technology can ensure that the first 1/10th of an inch heads to the sewer system while the rest is utilized for the building's intended purposes.
The
RainSwitch™ technology is made of stainless steel to ensure long life against harsh environments. The
RainSwitch™ is designed with a 14” funnel to collect the falling rain. It is connected to a diversion system, directing the subsequent run off to the storm drain system. The diversion system typically consists of a butterfly/ball valve adjacent to a clarifier, or sometimes a sump pump is used which controls the flow to the sewer or storm drain. The system design depends on the plumbing arrangement of your drainage system.
I penned an article for
International Filtration News last year that outlined this technology in depth. If you have the opportunity, please give it a read.
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