AWPPCE Bill Bardin Homework 10.2 In recent years, rainwater harvesting has emerged as a water conservation tool and an alternative water supply source, especially in arid areas of the United States. Escalating costs of centralized water systems and well drilling, an increasing recognition of the beneficial qualities of rainwater and dwindling water supplies are contributing to this trend. Interest in rainwater harvesting has also been spurred by the prospect of rising municipal water demand resulting from the enormous population growth. Rainwater harvesting is nothing new. Humans have been harvesting rainwater since we first began to walk erect on this planet. Harvesting rainwater is only a small part of the entire water cycle, but it is of growing importance. It’s not just about harvesting the rainwater but efficient use of all our water resources. Many communities in the United States face serious threats to a safe, steady supply of water. These include a longstanding reliance on centralized water delivery systems that results in urban areas and agencies largely overlooking opportunities to integrate alternate local sources of water to meet their water supply needs. One of the biggest offenders is the unnecessary use of potable water for non-potable uses, such as irrigation and indoor toilet flushing. The continually increasing areas of impervious surfaces, parking lots driveways, sidewalks and buildings in our landscape result in storm water runoff carrying pollution to our rivers, lakes, and beaches. Although the problems of water supply and water pollution can be complex, practical solutions for both are available now, such as capturing and using rainwater from rooftops. Rooftop rainwater capture is a simple, cost-effective approach for supplying water that promotes sustainable water management. By using rainwater rather than allowing it to run off of paved surfaces to pick up pollutants and carry them to nearby surface waters. Simple rainwater capture can provide numerous benefits to the local environment. Rainwater capture is an inexpensive, on-site supply of water that can be used for outdoor and non-potable uses with little, if any, treatment. In many cases captured rainwater can, and is used as a potable water supply with appropriately higher levels of treatment such as multi stage filtration and ultraviolet sterilization. One of the big advantages of using captured rainwater is minimal, or no energy and economic costs associated with treating and delivering potable water to end users because capture systems can often be designed using low-volume, non-pressurized, gravity fed systems or require only the use of a low power pump for supply, especially in the more arid areas of the United States where prolonged sub-freezing temperatures are present. By capturing and using rainwater for irrigation and other non-potable uses we are reducing the load on the potable water system, reducing the electricity to treat and pump that water and reducing the use of chemicals used in the purification. It also eliminates the addition of chemicals, chlorine and fluoride directly into the ecosystem. Reduced runoff that would otherwise contribute to storm water flows which is a leading cause of surface water pollution and urban flooding could be significantly reduced with rainwater capture. High periods of rain, during which most of the water runs off into the streams and rivers, can be captured and distributed over longer periods of time, maximizing the effectiveness of the water source. In the arid southwestern area of the United States the population is expected to double over the next fifty years and demand for water supplied from municipal sources is projected to double over the same time period. This problem is compounded by the fact that existing freshwater supplies are, for a variety of reasons, expected to decrease during that same time period. Increased loads on the water system from the agricultural demands of an exploding population place additional pressure on the total water supply making new farming methods and conservation essential. A repeat of the “Dust Bowl” era, 1930 – 1939, could prove catastrophic to the food supply in the United States. During the dust bowl era, over 10 million acres of land in the southwest and high plateau of the eastern Rocky Mountain area were stripped of their serviceable topsoil, an estimated 4.8 billion tons. The main source of water for the area, the Ogallala Aquifer, is being depleted at an alarming rate. A study by Kansas State University in Manhattan, Kansas, was recently published on in the journal Proceedings of the National Academy of Sciences. According to the study, the Ogallala Aquifer will see a 39 percent depletion of its available groundwater over the next five decades, which is in addition to the 30 percent reduction that the water supply has already recently faced. In response to this alarming condition, the State of Colorado, in 2009 passed laws outlawing the capture of rainwater. They have since relaxed some of these restrictions but the basic law remains in place. Other states, like Texas have actively promoted rain harvesting especially in the western areas of the state where rainfall totals less than 10 inches a year. Quite simply, rainwater harvesting is the capture and storage of rainwater for use. A rainwater harvesting system can be as simple as channeling the rain that runs off of a roof into a barrel or cistern or as sophisticated as a system made up of pumps, filters and water treatment equipment. Regardless of its complexity, a rainwater harvesting system consists of six parts: a catchment surface such as a roof; a channeling system such as gutters and downspouts; a screen or diverter; storage tanks such as barrels or cisterns; a delivery system such as pumps; and if the end use requires it, a treatment system such as sediment filters and ultraviolet lamps. Simple systems can supply water for lawns and other non-potable uses while more sophisticated systems, if properly designed, constructed and operated, can provide potable water. Costs for a rainwater harvesting system can range from a few thousand dollars to tens of thousands of dollars depending on size and complexity. The volume of water that can be collected by a rainwater harvesting system depends primarily on two factors: the catchment area and the amount of rainfall. For every square foot of catchment area, about 0.62 gal of water can be collected for one inch of rainfall. For example, if a house with a roof area of 2,000 ft2 receives 1 inch of rainfall, the volume of water that the homeowner can expect to realistically collect is about 1,240 gal. Is harvesting rainwater a good investment? Like most things it depends on your social view and commitment to improving the environment. For those taking the “Do no harm” approach, rainwater recycling can be a good, economical starting point. Rainwater harvesting systems can deliver a good return on investment. In certain areas of the country and the world, catching rainwater for household use is the only cost-effective solution. In locations like the US southwest, and arid rocky areas where no municipal water system is available and where well drilling can be prohibitively expensive, harvesting rainwater is a smart economic and environmental choice. On many Caribbean Islands, rainwater harvesting is the only reliable source of residential water, due mostly to the lack of infrastructure and relatively low population density. With the ever-rising costs of utility water, rainwater-harvesting systems can now make good financial sense for homeowners in high-water-rate areas typically in the western half of the United States. It’s not just the direct demands of population growth that are impaction our water resources. In 1973 the United States experienced the first of several oil crises. In an effort to wean ourselves from oil, the US mandated the use of ethanol as a fuel additive. In this country, ethanol is primarily produced from corn. The process uses exorbitant amounts of water. Petroleum refining consumes 1-2.5 gallons of water per gallon of refined product. Colorado scientists Kreider and Curtiss estimate that refining a gallon of corn ethanol today requires thirty-five gallons of water. But that is only the beginning. Kreider and Curtiss estimate that three times as much water is needed to grow the corn that yields a gallon of ethanol. That brings the tally to 140 gallons of water per gallon of corn ethanol produced. (6) If their calculation is correct, the 5.4 million gallons of corn ethanol used in America in 2006 required the use of 760 million gallons of fresh water. (7) Because of demands like ethanol production, water rates can be expected to continue to increase faster than the rate of inflation, so in more areas rainwater harvesting will make great economic sense. These increases are being driven by population growth and demand, diminishing fresh water supplies, and greater costs to process water to make it drinkable. Increased costs will spur more conservation, but it will also make the option of rainwater harvesting more viable for people. Many cities have such an old water delivery system that routine maintenance costs are rising at a rapid rate. New York City is spending billions of dollars to dig a new water aqueduct to bring water from the Adirondack Mountains north of the city. This is to supplement the existing lines that are over 100 years old. So is it worth it? Because of the number of variables, current water costs, expected increases, rainfall rates, household use rate, etc. It is very hard to determine the financial viability of a system. Each system needs to be evaluated on it’s own merits. The typical payback period for projects in the business world is three years. Projects that take longer to pay back typically require long-term financial justifications. Unless rainwater harvesting is essential to survival of the homeowner or the homeowner is socially committed to the environment, these systems do not come with a strong financial payback. Although the return on a rainwater system will only improve over time as utility water rates rise. Grey Water Recycling There are four basic types of water used in residential structures: White water – Potable water Grey water – Shower, Bath, Laundry, Lavatory Basin Dark water – Kitchen waste, food, strong detergents Black water – Toilets, Laundry (if washing diapers, etc.) For the purposes here I am dealing only with recycling grey water. Grey water can be defined as any household wastewater with the exception of wastewater from toilets, which is known as black water, or kitchen waste which may contain foodstuffs. Typically, 50-80% of household wastewater is grey water from bathroom sinks, tubs and showers. Freshly generated grey water is not as offensive as black water, but if it's not handled properly it can soon become so. Grey water decomposes at a much faster rate than black water and if stored for as little as 24 hours, the bacteria in it use up all the oxygen and the grey water becomes anaerobic and turns septic. At that point it is more like black water, a health hazard. Many jurisdictions have strict regulations about disposal of grey water, and some even prohibit it’s reuse or direct disposal. The safest way to handle grey water is to introduce it directly to the topsoil layer, where soil bacteria can quickly break it down, releasing the nutrients available to plants. Almost half of the water consumed by the average household in North America is for outdoor use, which begs the question, “Why use treated, potable water, if you don’t need to?” Capturing the grey water for use outdoors can cut water usage in half. There are additional benefits to be gained by using grey water. By diverting the grey water from the septic system extends the life and capacity of the system. If you are on a municipal sewer system, diverting grey water reduces the load. Grey water recycling for irrigation replenishes groundwater, helping the natural water cycle to keep functioning. Grey water can support plant growth in areas that might otherwise not have enough water, like the arid southwest. The nutrients in the grey water are broken down by bacteria in the soil and made available to plants. This helps to maintain soil fertility. The grey water user gets the satisfaction of direct participation in the responsible management of global nutrient and water cycles. In addition to applying grey water directly to the soil, it is possible to recycle it into the home for use in toilets to further reduce the water load of the home. This requires a significant investment in equipment and creates an ongoing maintenance commitment to be effective. As with any system of this type, the local environment must play the major roll as to the overall viability. For grey water recycling the type of soil plays a large part. If your soil is either too permeable or not permeable enough, you may not be able to recycle your grey water, or you may need a system with some modifications. The amount of grey water produced is also an important factor in the effectiveness of the overall system. It is essential that you have enough soil available to process the grey water and enough plants to use it. Since grey water recycling is a relatively new technology, many cities and towns have no clear guidelines regarding grey water processing. With water shortages looming in the near future for many regions, this may change sooner than later. Health concerns are often cited as the reason for not allowing grey water recycling, although the possibility of becoming sick is minimal with a properly designed, installed and maintained grey water system. Conclusion Both rainwater harvesting and grey water recycling are viable solutions to the growing water crisis. The ever changing climate on the planet which is exacerbated by, for lack of a better term, global warming, continues to put pressure on the global ecosystem. With the population expected to reach 7 billion in the next 6 years and 11 billion by 2050, there will be significant burdens placed on all our natural resources, especially water. (8) For example, Iceland, that gets 75 percent of it’s electricity from hydroelectric sources, primarily glacial runoff, projects that they will run out of water in 100 years. Even though the surface of the planet is 70 percent water, only 1 percent is potable. There are solutions to the water issue, iceberg harvesting, desalination, etc. but these tend to be very energy intensive and, at present, cost prohibitive. Rainwater harvesting makes sense in most areas of the world and grey water recycling can supplement our water use but both require a social and economic commitment. The biggest commitment being the social one. Only people on the ‘fringe’ are early adopters of programs that recycle, reduce, reuse, and even up cycle the products and resources we use today.