The U.S. Environmental Protection Agency’s (EPA) Water Infrastructure Resiliency and Finance Center, in collaboration with the...
Integrating water conservation strategies into water management
With drinking water becoming scarcer due to drought in highly populated areas and drinking water sources becoming more polluted, both individual homeowners and businesses are becoming aware of the need for drinking water conservation. This brings to mind the old saying, “reduce, reuse, recycle.”
While the thought of drinking recycled water may turn off many consumers, in a way we have been drinking recycled water for centuries. The water, or hydrological, cycle describes how water constantly changes between various states above and below the Earth’s surface, which is basically nature’s way of recycling. The mass volume of water on Earth is nearly the same as it was millions of years ago. It is the form in which the water exists, as oceans, rivers and groundwater, which varies over hundreds of thousands of years.
While businesses may look into reducing water use and the possibility of reusing water in production, it is usually done as a cost-saving measure as water rates continue to rise. The average consumer may accept the rate increases or look for simple options to reduce their water use, such as turning off the faucet when brushing their teeth or installing water-saving devices like low-flow toilets. In drought-affected cities, there is a demand for water conservation that involves restrictions on lawn watering.
The amount of freshwater that can be used for drinking is becoming more polluted, so we must act now to ensure clean drinking water. This involves conservation of current water resources and proper management of all water resources, which should include reducing the use of drinking-quality water in applications in which greywater or rainwater could be used instead. The cost of treating water to potable quality is higher, so we should use that water only for consumption. Non-potable water, such as rainwater and greywater, can be reused to flush toilets, wash cars, and water lawns and gardens.
In an effort to reduce the amount of water used, some people may opt to collect rainwater for gardening purposes. Of course, rainwater collection works best in areas with high rainfall levels. Some areas of the world, such as the island of Bermuda, rely heavily on rainwater collection for drinking water.
In some areas of the country, collecting rainwater not only saves water, but also helps cities control storm water and the pollution it may carry. Even in New York City, in a part of the U.S. that generally receives more than adequate rainfall to meet its needs, rainwater detention is mandated for new building projects above a certain size to help control storm water runoff.
Matt Kaye, president of Better Waters, a water technology company that actively advises engineering firms and has supplied rainwater reuse technologies for numerous large-scale New York City projects, noted that there has been an exponential increase in demand for such systems as construction has returned to robust levels following the recent economic downturn. “Today, unlike before the Great Recession, we are seeing one high-end project after another, whether residential, commercial, hotel or mixed use, include rainwater retention and reuse,” Kaye said. “In fact, I think we are at the point that a majority of the most prestigious new projects underway in New York City incorporate this conservation measure: 99 Church Street, 56 Leonard Street, 855 Sixth Avenue and 205 E. 92nd Street, for instance, are excellent examples. And part of our challenge [in] meeting the principles of sustainability is to design technology sequences that minimize [the] power required to accomplish the goals of conservation.”
Some cities or sewer districts offer financial incentives for homeowners and businesses by providing a discount on water and sewer bills for those who install rain barrels or rain gardens, or remove or reduce impervious surfaces, thus reducing runoff. The payoff can be substantial. In Austin, Texas, for example, businesses can earn up to $40,000 in rebates for installing rainwater harvesting and greywater reuse systems. Rainwater reuse also helps buildings qualify for LEED (Leadership in Energy & Environmental Design) credit, which is a certification for green building growing in popularity.
Because rainwater is raw and can pick up contaminants from the surface it runs over, it is a good idea to assess the water quality. The two biggest quality concerns with rainwater are particulates and microbiological contaminants.
The intended use of rainwater dictates what treatment may be necessary. Rainwater that will be used in non-potable applications may not require treatment for microbiological contaminants, but would need filtration to reduce particulates. If rainwater will be used for potable applications, microbiological contaminants must be addressed.
Microbiological contamination can occur easily as water runs from rooftops, which may contain animal excrement. Bacteria also can thrive if water sits stagnant for a period of time. Ultraviolet light is commonly used for rainwater disinfection, but other technologies, such as ozone or chemical disinfection, may be used depending on regulatory requirements and the client’s needs. In some cities, rainwater that will be used for drinking requires a disinfectant that has a residual, like chlorine. It is important to become familiar with local requirements for rainwater collection and treatment before installing these types of systems.
Recycled Water Treatment
Recycled water, also called reclaimed water, comes from treating water that normally would be discharged as wastewater — i.e., water from wastewater treatment plants that has been treated. This reclaimed water is mainly used for irrigation and recharging aquifers, but some drought-stricken areas are considering using reclaimed water to supplement dwindling water supplies.
In the U.S., California and Florida are active in utilizing reclaimed water. Irvine Ranch Water District in California was one of the first to approve the use of reclaimed water for in-house non-potable use. The reclaimed water makes up about 21% of the district’s water supply, and is mostly used for irrigation, cooling towers and toilet flushing. To distinguish between reclaimed water and potable water, purple pipe is used for reclaimed water delivery.
In addition to reclaimed water, there also is greywater, which is wastewater from sinks, showers, dishwashers and washing machines that can be reused on site for non-potable applications like flushing toilets or irrigation. As expected, drought-affected states California and Texas have regulations in place for the use of greywater, as do New Mexico, Wyoming, Montana and Utah. More states are likely to follow with regulations of their own as water conservation becomes more important.
Recycling water can become complex depending on which contaminants are present and the intended end use of the water. Some important things to consider when recycling water are energy and chemical costs, as well as size restrictions for equipment.
The first step in any recycling project is to determine what the recycled water will be used for. If it will be used for potable purposes, additional treatment will be needed. Then determine what possible contaminants may be present. It is a good practice to have the waste stream tested to identify which contaminants are present and at what levels. For blackwater, testing should include bacteria, metals and other inorganics, specifically phosphates, nitrates, biological oxygen demand, chemical oxygen demand and ammonia. Keep in mind that pharmaceuticals likely will be present in wastewater, and these may be regulated in the future. Once you have a profile of the water quality, you can begin to consider what treatment options are available and what costs are involved.
The need for water conservation is evident all over the world. The U.S. is just now realizing it is time to change its water management practices, including encouraging rainwater harvesting and reusing greywater and reclaimed water. Rainwater harvesting and greywater reuse present opportunities for water treatment professionals to expand their services to meet customers’ water treatment needs, which may not just be for drinking water anymore.