By Toby Hughes, P. Eng
For nearly two centuries, North Americans have enjoyed the convenience of running water in their homes. While once considered a luxury, we have become so accustomed to its role in our everyday lives that we often take for granted the work that goes into making it safe. The lead crisis in Flint, MI, opened our eyes to the importance of safe drinking water. Since then, Americans have increasingly turned to bottled water or in-home drinking water systems, due to concerns or lack of trust in the safety of public drinking water.
According to the Water Quality Association’s (WQA) 2019 National Study of Consumers’ Opinions & Perceptions Regarding Water Quality, more than half of American households are concerned or very concerned about the quality of their water supply. The concern over both overall water quality and the safety of tap water have both grown since the WQA undertook the same household study in 2017.
The study also showed that RO systems are one of the top choices in drinking water systems and that eliminating contaminants is one of the top concerns of American households, along with cost and performance. With increasing concern over the quality of drinking water and the emergence of new contaminants like PFAS and PFOS, demand for drinking water systems will continue to be strong in the residential and commercial water conditioning industry.
Reverse osmosis technology is known for its high effectiveness in removing many types of contaminants, including lead. RO systems are also effective at reducing arsenic, radium and other harmful elements from water. What’s often less known about RO technology is the large volume of water that is sent to the drain during the filtration process. Most RO systems reject anywhere from three gallons (11.35 liters) to more than six gallons (22.71 liters) of water for every gallon (3.78 liters) of purified water that they produce.
As environmental consciousness and consumer savvy continue to rise, particularly among younger generations who are representing a growing percentage of US homeowners, there is no doubt that simply delivering safe drinking water won’t be enough. Consumers will demand RO systems that are more efficient and environmentally friendly. In fact, this trend is already well established. Washington, DC-based fact tank Pew Research Center says between 1995 and 2015, daily water consumption in American homes fell from 97.5 gallons (369.07 liters) per person to 81.7 gallons (309.26 liters). Today, virtually all water-using appliances have significantly improved their water efficiency to meet customer expectations.
Offering an RO system that uses significantly less water during the filtration process can be a selling feature that sets you apart from your competition. With the right high-efficiency RO system, your customers can have the best of both worlds: bottled quality water at their tap and a system that doesn’t send gallons of precious water down the drain every day. High-efficiency RO systems currently on the market are achieving efficiency ratios (total water to drain/RO permeate water produced) of 2:1 concentrate (or reject) water to product water, 1:1 and some are wasting virtually no water at all, all of which are significant improvements from the 12:1 ratio of some conventional RO systems.
High-efficiency RO technology at work
Reverse osmosis removes contaminants from water by using pressure to force water molecules through a semipermeable membrane. The water that does not make it through the membrane becomes concentrated with particles or molecules that didn’t pass through the membrane and that concentrated water is continually removed from the system. Some systems have improved their efficiency by reducing back pressure, a key reason that water is rejected during the RO process.
One RO system on the market has taken a dramatically different approach to reducing water consumption and as a result is wasting virtually no water during the filtration process. This high-efficiency RO system has been designed to recycle 99.9 percent of the concentrated water created during the RO process back into the household’s water supply.
If the home has a softener or filtration system, the concentrate water is fed back from the RO system into the home’s inlet or feed-water line just before the softener or filter. If the home is built on a slab, doesn’t have a softener or whole-home filter, or requires the system to be installed under a sink rather than in a mechanical room, a blending tank is installed. In the latter applications, the concentrate is fed back into the blending tank and mixed with incoming feed water, so the ratio of concentrate to feed water slightly increases the TDS in the water before it is used in the home.
Whether the RO system uses a blending tank or runs through a softener or filtration system, it creates a continuous feed of concentrated water from the RO system back into the home or business’ plumbing, sending virtually no water to drain during the filtration process. The strategic placement of flow controls, check valves and solenoid valves on the system’s concentrated water line allows it to maintain enough pressure on the RO membrane for the purification process, while also creating the pressure needed to run the concentrated water back into the inlet or feed-water line. The end result is an RO system that produces high-quality water, while recycling 99.9 percent of the concentrated water created during the RO process.
This system can save a household approximately 7,000 gallons (26,497.88 liters) a year of water, based on four people consuming one gallon (18.92) each per day and the RO system wasting five gallons of water per one gallon of drinking water produced. The savings increase for RO systems that use as much as 12 gallons (45.42 liters) of water for every gallon of drinking water they produce.
If reverse osmosis systems are part of your product offering and you haven’t done your homework on new high-efficiency models, it’s time to start. These systems can be a game changer for environmentally conscious customers, for homeowners who believe that needlessly sending water to the drain is a waste of money and for customers who are carefully managing water consumption because they are using septic systems. High-efficiency RO systems are a great way to set you apart from your competition.
(Author note: It’s important to note that in this article, the system being referred to is being used on a potable, municipal water system and the intended use is to reduce TDS in the purified water. The concentrated water is returned ahead of the softener or filter system. This aids in the dilution of the concentrated water to minimize potential negative effects of the recycling. The increase in TDS will depend on the volume of stored concentrate fed into the plumbing system as well as the TDS concentration of the stored water.)
About the author
Toby Hughes, P.Eng, Chief Operations Officer and co-Founder of Canature North America, has more than two decades of engineering and management experience in the North American residential and commercial water conditioning industry. He can be reached at email@example.com.