Storm Water, Gray Water, & Black Water Recycling and Reuse

Using  Natural  Ecosystems  As  Our  Guide  
By: Melissa Meyer

Less than two-tenths of one percent of the planet's water is drinkable. In many developing countries the majority of the population does not have access to clean, safe water. Out of desperation people drink contaminated water, even though it carries deadly diseases and heavy metals that are toxic to tissues and organs. Open sewers ensure that contaminants reach the water table and remain in the water supply. As Americans we are privileged to live with the luxury of being able to turn on a tap and have clean, fresh, potable water (water that is safe for drinking and cooking) that is enriched with fluoride for dental health.

We use potable water to drink, cook, bathe, and to wash our dishes, to flush our toilets, water our landscaping, wash our cars, hose down our driveways, fill our pools and fountains, and we use it in our heating and cooling systems. Eighty percent of our nation’s potable water is used in the construction and operations of our buildings. We need potable water only for drinking, cooking, bathing, and washing our dishes. Harvested rain water and reclaimed gray water (domestic wastewater composed of wash water from kitchen, bathroom, and laundry sinks, and from bathtubs, showers, dish washers and clothes washers) can be used to flush our toilets, water our landscaping, wash our cars, hose down our driveways, fill our pools and fountains, and in our heating and cooling systems. If a community can recycle and reuse eighty percent of the water it uses, it can increase its’ water supply by four hundred percent!

In urban China, where water scarcity, contamination and pollution pose great challenges, a dual piping system is used to supply both potable and reclaimed water to homes and businesses. A separate tap delivers the potable water. The system prevents the mixing of the two water supplies and allows for the recycling and reuse of gray water. With proper planning, beginning in the early stages of the design of the landscape, architecture, and engineering processes of a community, the recycling and reuse of gray water can be commonplace. The problem of black water, (water that contains animal, human, or food waste) can be mediated by the use of composting toilets that allow for the use of harmless humanure as fertilizer for landscaping and vegetable gardens.

Water purification occurs in nature as rainwater, flood waters, and runoff move through estuaries, swamps, marshes, bogs (areas of soft, marshy land where moss and rare plants thrive), and riparian areas (the zone between a stream or river and the adjacent land). Infiltration occurs as water soaks into the ground and flows through soil, rock, and gravel. Tightly packed particles that make up the soil filter out impurities and absorb excess nutrients such as nitrogen and phosphorous while pollutants and waste  are filtered out. Water is also absorbed by the roots of specially adapted plants and moves up through the xylem of the plant and is transpired into the atmosphere as vapor, leaving waste particles behind to be broken down by the plant. By the time the water flows into lakes, streams, rivers, and oceans it is often cleaner than tap water.

However, the earth’s ability to purify its water is being severely compromised by humans. Overdevelopment is causing a loss in acreage of wetlands and an increase in impervious surfaces such as roads, highways, and parking lots, accelerating runoff, increasing flooding, and funneling contaminated water directly into lakes, streams, rivers and oceans, completely bypassing natural filtration systems. The natural flow of surface water and groundwater is being altered by hydrologic modifications and the reconfiguration of waterways, increasing invasive plant and animal species, disrupting entire ecosystems, and thus destroying nature’s water purification systems. Periods of heavy rain or snow melts intensified by global warming are overwhelming the natural filtering systems that we have left.

Storm water is rain and snow melt that runs off surfaces, such as, rooftops, paved streets, highways, and parking lots. It does not infiltrate the ground and flows into trench drains and storm sewers where it is usually routed directly into lakes, rivers and streams, taking harmful toxins and pollutants with it. The first step in managing storm water is reducing the amount of paved surfaces. Alternative paving materials are porous asphalt, porous concrete, block pavers, and plastic grid systems. Each of these products is designed to allow percolation and infiltration of storm water through the surface into the soil below where pollutants are removed through natural processes. If storm water is properly managed, the need for trench drains and storm sewers is eliminated.

Storm water can be directed to a permeable surface or rain garden (a collection of plants that can survive on the rainfall and do not require watering), via a bio-swale (a mechanism for directing the flow of storm water) where it can be naturally purified and filtered down to replenish the ground water  supply (any subsurface water that occurs beneath the water table in soil and other geologic forms). Storm water can also be harvested, using rain water barrels or cisterns, and reused to flush toilets, water landscaping, wash cars, hose down driveways, fill pools and fountains, and in heating and cooling systems.

Gray water from wash water from kitchen, bathroom, and laundry sinks, and from bathtubs, showers, dish washers and clothes washers can be collected in an internal tank or external container and, after mimicking water filtration and purification processes that occur in nature, can be reused to flush toilets, water landscaping, wash cars, hose down driveways, fill pools and fountains, and in heating and cooling systems. Green cleaning products should be used so as not to taint the gray water supply. Garbage disposals should not be used. Garbage disposals dispose of food waste into gray water, making it more complicated to treat. Food waste should be composted and the compost should be used to fertilize landscaping and gardens.

Harvested storm water and collected gray water can be combined and the two water sources can be naturally treated and reused simultaneously for non-potable uses, vastly increasing the water supply. Gray water from kitchen, bathroom, and laundry sinks, and from bathtubs, showers, dish washers and clothes washers, can be directed into the same cistern that is being used to harvest storm water from roofs. Storm water and gray water from the cistern can then be directed to a contained, below grade or above grade sandbox, where waste particles are filtered out.

Gravity or an adjacent pump, which can be run with electricity generated from solar panels, can move the water to the next station, a planter box, where water will percolate through vegetated soil and gravel filters, removing more pollutants such as phosphorus and nitrogen, as microbes in the plants' roots capture chemical toxins and release them as harmful gases. Sustainability can be maximized by using plants that produce fruits or vegetables in the planter box. Next, gravity, or a secondary pump, running on electricity from solar panels, will then direct the clean water to another cistern. The cleaned water can then be routed, with the assistance of gravity or another pump, back to kitchen, bathroom, and laundry sinks, and to bathtubs, showers, dish washers and clothes washers for reuse. It can also be used to water landscaping, power wash decks, hose down driveways, etc.

Planter boxes can be designed to create courtyards and outdoor rooms. Cisterns and sand box containers can be placed out of sight, under the house, on the roof, or in enclosed quarters, situated in such a way so that the use of pumps is minimized and the use of gravity to move water through the filtration process is maximized. Black water can also be treated and reused as gray water, but additional steps are required. First solids must be trapped, removed and stored for later use as humanure.  A retention pond can be added and designed to mimic natural wetlands where aerobic conditions can be sustained and the breakdown of organic nitrogen can occur. The ponds can be integrated into the landscape. Fish can be added to aid in the particle removal process. Waterfalls and recirculating fountains can also be used as addition cleansing mechanisms and can enhance the built environment. Storm water, gray water, and black water recycling and reuse can be simple and affordable if we use natural ecosystems as our guide.

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