Greywater Information
What is greywater?
Greywater is normally defined as water that comes from your showers, baths, hand basins in the bathrooms and water from your washing machine. It does NOT include water from the toilets, kitchen/ scullery sinks or dishwasher. This water is classified as black water.
Uses
Greywater can normally be used for applications where non-potable water is adequate. This includes irrigation, washing of cars or driveways and toilet flushing. Greywater should never be used for drinking water.
Greywater systems
Basically there are two ways of re-using greywater for these functions mentioned above. These are either simple systems or complex systems.
Simple systems focus on capturing the greywater from source and then immediately re- using it again. Immediately can be defined as within 24 hours. Complex systems focus on capturing the water and storing it for longer than 24 hours, treating it and then re-using it.
Simplest is often best and the more complicated the system, the more the cost involved.
When greywater is stored for longer than 24 hours, it begins to change into blackwater. The pathogens present in the water begin to multiply, feeding on any organic material in the water and using up oxygen in the process. The water rapidly changes, developing an offensive odour and becoming foul.
Simple systems focus on capturing the water from the household, normally by allowing it to gravity feed into a temporary collection sump/tank, and then pumping it out for use in the garden or for toilet flushing. There is normally some sort of macro filtration device that captures big particles such as hair, fluff, etc., before the water enters the collection sump. This is to prevent fouling of the pump and/or irrigation system.
In systems where there is an existing irrigation system, this water may first be pumped into a second larger collection tank where it is “bulked up” with another water source (rainwater or municipal water) and then it is pumped through to the irrigation system using a pressure booster pump. It may then pass through another finer filtration system to prevent fouling of the irrigation nozzles. It must be understood that the water is not truly being stored in the second larger tank, but is merely pausing there before being pumped out. The defining factor may be that it is still being used within the 24 hour period. Irrigation systems often need this “bulking up” with another water source to provide sufficient volume to satisfy a larger garden with many sprayers. This can happen if the household is not generating enough greywater for the entire gardenʼs needs. Smaller gardens may get away with only surviving on the greywater being generated by the household. Having said this, it may be better to replace water thirsty plants with indigen
The water from greywater can also be pumped to toilets for flushing. However the one problem with taking “raw” greywater straight to a toilet cistern is that if it is allowed to sit inthe cistern or toilet bowl for longer than 24 hours, it may start to smell due to reasons mentioned above.
There are also different schools of thought as to how to apply the water to the garden. Many systems and countries prefer the subsoil route of administration. Soil is an excellent system for breaking greywater down into safe components. This is due to the high microbial activity found in the first few feet of soil. If the greywater is applied directly to the subsoil layers, it interacts with these microbes and is broken down. This can be done using drip irrigation.
Other schools of thought prefer to spray it onto the garden using a sprayer that has large droplets. They feel that the smaller particles in greywater not filtered out may clog the drip irrigation and prevent it from working. Larger droplets are also less likely to aerosolise and thus there would be less chance of people inhaling it.
Complex systems also capture greywater but normally store it and treat it to remove the pathogens before it is re-used. There are various methods of treating greywater including biological/ bacterial methods, ozonation, electro-flocculation and fine filtration systems e.g. Reverse osmosis.
As mentioned earlier, these systems increase the cost and complexity of a greywater system. There is however a place for these systems in larger facilities such as schools, hotels and commercial buildings.
Also check out the following resources;
http://en.wikipedia.org/wiki/Greywater
http://www.enviro-friendly.com/greywater-systems-australia.shtml
What is greywater?
Greywater is normally defined as water that comes from your showers, baths, hand basins in the bathrooms and water from your washing machine. It does NOT include water from the toilets, kitchen/ scullery sinks or dishwasher. This water is classified as black water.
Uses
Greywater can normally be used for applications where non-potable water is adequate. This includes irrigation, washing of cars or driveways and toilet flushing. Greywater should never be used for drinking water.
Greywater systems
Basically there are two ways of re-using greywater for these functions mentioned above. These are either simple systems or complex systems.
Simple systems focus on capturing the greywater from source and then immediately re- using it again. Immediately can be defined as within 24 hours. Complex systems focus on capturing the water and storing it for longer than 24 hours, treating it and then re-using it.
Simplest is often best and the more complicated the system, the more the cost involved.
When greywater is stored for longer than 24 hours, it begins to change into blackwater. The pathogens present in the water begin to multiply, feeding on any organic material in the water and using up oxygen in the process. The water rapidly changes, developing an offensive odour and becoming foul.
Simple systems focus on capturing the water from the household, normally by allowing it to gravity feed into a temporary collection sump/tank, and then pumping it out for use in the garden or for toilet flushing. There is normally some sort of macro filtration device that captures big particles such as hair, fluff, etc., before the water enters the collection sump. This is to prevent fouling of the pump and/or irrigation system.
In systems where there is an existing irrigation system, this water may first be pumped into a second larger collection tank where it is “bulked up” with another water source (rainwater or municipal water) and then it is pumped through to the irrigation system using a pressure booster pump. It may then pass through another finer filtration system to prevent fouling of the irrigation nozzles. It must be understood that the water is not truly being stored in the second larger tank, but is merely pausing there before being pumped out. The defining factor may be that it is still being used within the 24 hour period. Irrigation systems often need this “bulking up” with another water source to provide sufficient volume to satisfy a larger garden with many sprayers. This can happen if the household is not generating enough greywater for the entire gardenʼs needs. Smaller gardens may get away with only surviving on the greywater being generated by the household. Having said this, it may be better to replace water thirsty plants with indigen
The water from greywater can also be pumped to toilets for flushing. However the one problem with taking “raw” greywater straight to a toilet cistern is that if it is allowed to sit inthe cistern or toilet bowl for longer than 24 hours, it may start to smell due to reasons mentioned above.
There are also different schools of thought as to how to apply the water to the garden. Many systems and countries prefer the subsoil route of administration. Soil is an excellent system for breaking greywater down into safe components. This is due to the high microbial activity found in the first few feet of soil. If the greywater is applied directly to the subsoil layers, it interacts with these microbes and is broken down. This can be done using drip irrigation.
Other schools of thought prefer to spray it onto the garden using a sprayer that has large droplets. They feel that the smaller particles in greywater not filtered out may clog the drip irrigation and prevent it from working. Larger droplets are also less likely to aerosolise and thus there would be less chance of people inhaling it.
Complex systems also capture greywater but normally store it and treat it to remove the pathogens before it is re-used. There are various methods of treating greywater including biological/ bacterial methods, ozonation, electro-flocculation and fine filtration systems e.g. Reverse osmosis.
As mentioned earlier, these systems increase the cost and complexity of a greywater system. There is however a place for these systems in larger facilities such as schools, hotels and commercial buildings.
Also check out the following resources;
http://en.wikipedia.org/wiki/Greywater
http://www.enviro-friendly.com/greywater-systems-australia.shtml
