Stormwater: The Middle Child of Water Quality

Stormwater is the third category of water to be managed, following drinking water and wastewater. With a high performing first child (drinking water) and the third child to clean up after (wastewater), the middle child stormwater can be overlooked. However, stormwater might be getting its day. With growing pressures on our existing drinking water sources, both in terms of volume and quality, it’s time to think outside the box. Local, national, and international groups are working to use this resource through new technologies and policies. As we learned at last year’s AWWA Water Quality Technology Conference, all water is source water.

Stormwater is typically managed, but not utilized. Techniques are used to prevent stormwater from causing problems such as flooding or the washing of fertilizer into lakes and streams. As concerns grow over dwindling potable water sources, there is a call, and a response, to think outside of conventional stormwater management processes. Rainwater harvesting is a topic of focus at AWWA’s Sustainable Water Management Conference. A group founded in 1994 known as the American Rainwater Catchment Systems Association promotes and supports stormwater reuse projects. Due to the small scale of stormwater reuse projects, the U.S. EPA only has a little information on the topic, though they have a quite extensive website regarding green infrastructure, which generally encompasses techniques for distributed stormwater management that reduce energy requirements. Other countries with higher water stresses, such as China and Australia, have also begun seriously examining stormwater harvesting systems.

While stormwater harvesting is not commonly undertaken by a municipality itself, it is often encouraged to be undertaken by individual households and institutions through incentive systems. Thus, the market for rainwater systems fall in the small to mid-scale range. There are a number of companies filling this design space with new and innovative technologies. A major hurdle in stormwater utilization is the treatment needed to remove pollutants that enter through contact with air, soil, and pavement, and to maintain the quality of water while in storage. Additionally, as systems increase in size, storage and pumping solutions become increasingly complex. Techniques for maintaining water quality include the adoption of first flush, which diverts the initial water flow of a rain event to avoid water with the highest contamination, and the use of opaque materials to prevent algal growth. Further water treatment depends on the end use of the stored water: for irrigation, water can be used as is, for indoor non-potable applications (such as toilet flushing), filtration to remove suspended particles is required to avoid damage to piping systems. Higher levels of treatment can be taken to produce water suitable for laundry and dishwashing, and even to produce water suitable for drinking. By giving stormwater the attention it deserves, we are maximizing our precious drinking water resources.