Water reclamation

Water reclamation is a process by which wastewater from homes and businesses is cleaned using biological, chemical, mechanical, or a combination of these treatments so that the water can be re-purposed, or returned to the environment safely to augment the natural systems from which it came. It is used today as both an aquifer and stream enhancement strategy, and to preserve this natural resource.

Benefits

Water reclamation helps decrease diverging water from sensitive eco-systems which depend greatly on the flow to improve the quality of the water. Water reclamation also decreases the pollution to bodies of water, such as oceans and rivers, by diverting the wastewater. Some of the pollutants are used for irrigation purposes, such as nitrogen, which would be harmful to these bodies of water. Another benefit is the enhancement of wetlands which benefits the wildlife dependent on that eco-system. For instance, The San Jose/Santa Clara Water Pollution Control Plant instituted a recycling program to protect the San Francisco Bay area's natural salt water marshes.^[1]

Uses

Most of the uses of water reclamation are non potable uses such as: Washing Cars, flushing toilets, cooling water for power plants, concrete mixing, artificial lakes, irrigation for golf courses and public parks, and for hydraulic fracturing. Where applicable, systems run a dual piping system to keep the recycled water separate from the potable water.

Indirect water reclamation (water passing through a body of water first) will result in potable water usage. While this is not practiced in the United States, it is in other countries such as Namibia.

Aboard the International Space Station, astronauts have been able to drink recycled urine due to the introduction of the ISS ECLSS system. The system costs $250 million and has been working since May 2009. The system recycles wastewater and urine back into potable water used for drinking, food preparation, and oxygen generation. This cuts back on the need for resupplying the space station as often. ^[2]

In recent years, as hydraulic fracturing of oil and gas formations has become more and more common place, new technologies for recycling the water needed for the process have emerged. One such technology uses a combination of ozone and electrocoagulation. This process removes organics, hydrocarbons, spent polymers (chemical additives used in the fracturing process, and heavy metals such as barium, iron, boron and more. This then allows the water to be used for fracing purposes and can save an estimated 4 - 7 million or more gallons per well. ^[3]

Alternatives to Water Reclamation

Greywater

Like water reclamation, greywater recycles used water for irrigation and other various uses. Greywater uses the same waste as water reclamation with the exception of toilet water. Unlike water reclamation, greywater does not purify the water through a biological process, but by sand filters and soil. After passing through the soil, where it is filtered like rain water, it flows into the groundwater where it will be reused again. ^[4]

Desalination

Desalination is an energy-intensive process where salt and other minerals are removed from sea water to produce potable water for drinking and irrigation, typically through membrane filtration (reverse-osmosis), and steam-distillation.

Many ships and submarines make use of this technology. The idea of desalination is a heavily researched area worldwide. Many methodologies have been developed, including nuclear-powered desalination, and solar-powered desalination.

Reclamation Processes

Wastewater must pass through numerous systems before being returned to the environment. Here is a partial listing from one particular plant system:

• Barscreens - Barscreens remove large solids that are sent into a grinder. All solids are then dumped into a sewer pipe at a Treatment Plant.

• Primary Settling Tanks - Readily settable and floatable solids are removed from the wastewater. These solids are skimmed from the top and bottom of the tanks and sent to the Treatment Plant where it'll be turned into fertilizer.

• Biological Treatment - The wastewater is cleaned through a biological treatment method that uses microorganisms, bacteria which digest the sludge and reduce the nutrient content. Air bubbles up to keep the organisms suspended and to supply oxygen to the aerobic bacteria so they can metabolize the food, convert it to energy, CO₂, and water, and reproduce more microorganisms. This helps to remove ammonia also through nitrification.

• Secondary Settling Tanks - The force of the flow slows down as sewage enters these tanks, allowing the microorganisms to settle to the bottom. As they settle, other small particles suspended in the water are picked up, leaving behind clear wastewater. Some of the microorganisms that settle to the bottom are returned to the system to be used again.

• Tertiary Treatment - Deep-bed, single-media, gravity sand filters receive water from the secondary basins and filter out the remaining solids. As this is the final process to remove solids, the water in these filters is almost completely clear.

• Chlorine Contact Tanks - Three chlorine contact tanks disinfect the water to decrease the risks associated with discharging wastewater containing human pathogens. This step protects the quality of the waters that receive the wastewater discharge.

One of two procedures are then followed according to the future disposal site:

1. Reclaimed Water Pump Station - The pump station distributes reclaimed water to users around the City. This may include golf courses, agricultural uses, cooling towers, or in land fills.
2. Water is passed through high level purification to be returned to the environment. Currently this means a reverse osmosis system. ^[5]

See also

• Sewage treatment
• Reclaimed water
• Wastewater engineering

References