Ozone, the Cost Effective Solution for Rainwater Harvesting
Rainwater harvesting solutions have been increasing globally over the past decade. As population increases, so does the water demand for people, industry and agriculture. Climate change and growing water scarcity have now accelerated the need for sophisticated rainwater technology to conserve and utilize this often-ignored freshwater source. Ozone is a superior future proof treatment solution that offers many cost savings and treatment benefits for rainwater management. Ozone is the fastest growing technology in the global water disinfection market and is universally recognized as the fastest, strongest and most environmentally friendly water treatment technology available today.
3 in 1 Treatment
Ozone is a unique comprehensive three in one water treatment solution that provides disinfection, oxidation and – critical for water re-use - improved aesthetics. It is generated on site, requiring no consumables or chemicals, saving significantly on costs. Post treatment, ozone quickly breaks down to dissolved oxygen, leaving no residual in the effluent and eliminating the need for special disposal systems.
Wrinkled microbial mat (biofilm) growing on water surface
The treatment of rainwater, like any source water requires a detailed understanding of the range of contaminants that are most often present throughout the course of a typical year. As distilled rainwater falls from the sky, it collects contaminants from the air, building and ground surfaces. Contaminants from birds and animals as well as various roofing materials all need to be addressed. For example, when rain comes in contact with a metal roof, it is often contaminated with iron. If the roof is made of asphalt the rainwater can have trace amounts of hydrocarbons. Rainwater runoff from a green roof often contain contaminants from the soil it filters through.
Ozone has the ability to treat rainwater on demand, as well as prevent biofilm and other contamination in stored rainwater tanks. The resulting high quality water can be used for a wide variety of non-potable applications including toilet flushing, car washing, landscape irrigation, watering plants & trees etc.
For rainwater reuse to be “accepted” by the public for use in non-potable applications, the clarity and safety of that water is paramount. Ozone has the unique ability to provide on-demand disinfection and oxidation, while also treating colour, odour and other contaminants for clear, clean and safe water. These key benefits have contributed to ozone’s rapid adoption for rainwater treatment applications.
Biofilm and Pathogen Exposure Prevention
Biofilm is a common contaminant found in rainwater storage tanks. Biofilm can provide a harbour for pathogens, including Legionella. If rainwater containing biofilm is reused in applications where water can be aerosolized, such as water fountains, irrigation etc., Legionella exposure could be a risk factor. Ozone treatment systems remove and prevent the growth of biofilm, thereby removing the risk of Legionella and other pathogen exposure.
Ozone Versus Membrane
Ozone rainwater treatment solutions have several significant advantages over traditional membrane systems. Membrane filters are very fine and are expensive to maintain and replace. They require routine downtime and chemical washing to clean the contaminants captured in the membranes and biofilm build-up on the systems surfaces. Captured contaminants often require a secondary treatment for disinfection, such as UV or chemicals. If aesthetics is an issue, such as colour from organic matter, a further treatment may also be required.
Ozone by contrast, can treat rainwater independent of filters depending on the contaminants in the source water and the intended application. For example, if rainwater is to be used for landscape irrigation, filters may not be necessary.
When required, ozone systems incorporate self-cleaning media filters with automatic backwash features. Also, because ozone has the unique ability to coagulate & floc contaminants, media filters (typically 20-30 microns) are effective. These filters cost significantly less than membranes, are ideal for any flow range, require minimal maintenance/operational time, and offer an extended lifespan.
Membrane rainwater systems typically require a much larger footprint, which is an important factor in commercial building cost considerations. Ozone by contrast is compact, offering the most powerful treatment per square foot and can often be easily retrofitted within existing building space.
Water Efficiency and Cost Savings
Rainwater is typically captured and piped into large cisterns or holding tanks and treated on site when needed. Rainwater can also be incorporated into an automated closed loop system that can significantly reduce overall water consumption by providing non-potable water for re-use. For seasonal variations in rainfall, a municipal connection is also available when additional water may be required.
Rainwater reuse can contribute to significant cost reductions and efficiencies in municipal water demand and treatment including less treated drinking water needed for non-potable applications and less runoff rainwater to be collected and treated. Building owners within the municipality also benefit by reducing their paid water use while improving their ESG rating and overall water sustainability.
Ozone With or Without Filtration
Rainwater treatment options can be engineered with ozone alone, ozone plus filtration or, ozone plus filtration and UV (ultra-violet). An ozone system provides a site-specific solution engineered to address the source water contaminants and reuse application. Most solutions include self-cleaning filtration, pre and/or post treatment to capture organics and other solid matter treated with ozone.
Ozone offers the strongest treatment per square foot, saving valuable space. Typically, rainwater is collected in a tank or cistern where the water is “batch” treated on a recirculation loop to maintain quality. Inline automation provides continuous and precise water quality to ensure optimal treatment with minimal energy use. Optional 24/7 remote monitoring eliminates the need for chemistry, optimizes safety and reduces required operator time.
An ozone rainwater treatment system with slipstream injection.
Ozone/UV Combination Benefits
Ozone for rainwater is often combined with UV to enhance treatment and/or for redundancy. UV alone cannot treat metals, dissolved organic compounds (e.g., colour), biofilm and other contaminants which, if not removed will greatly impact its performance. Untreated contaminants can foul UV lights and result in high maintenance and poor water quality. Ozone in the treatment train ensures complete disinfection, treatment and clarification prior to UV which is a critical for optimal UV effectiveness. Lastly, combining ozone and UV results in Advanced Oxidation Processes, a short lived but extremely powerful treatment for tough to remove contaminants e.g., PFAS;
Ozone/UV rainwater systems are typically designed as follows :
i) Ozone is used to continuously treat the stored water and remove/prevent biofilm on the tank/cistern surfaces
ii) UV is used to treat the water on demand when sent to the application
An Ozone/UV combination offers a couple of benefits. Firstly, it provides redundancy in the event one system fails. Secondly, UV can remove virtually all residual ozone for applications where this may be required.
Aclarus has extensive experience in rainwater treatment. We engineer advanced ozone rainwater harvesting and managements systems that deliver superior complex water treatment and a range of cost efficient water re-use applications. To view an Aclarus ozone rainwater system, with automatic backwash and self-cleaning filtration, please click the video below. To learn more please contact us here.