What is Greywater, Blackwater, and Cleanwater?
This article will describe the differences between cleanwater, greywater, and blackwater, and cover how these water classifications can both reduce the stress humans put on the freshwater environments as well as save taxpayers money. Let’s get started!
Background
Before talking more about clean, grey, and black water, let's going to give a little background on the environmental and economic cost associated with cleaning and disinfecting water for human use:
The water humans use for domestic practices and industry come at both an environmental and economic cost. Water taken from freshwater systems for human uses reduces reservoir levels, river flows, and groundwater levels in systems that would be otherwise be used to sustain aquatic habitats. For instance, recent 2022 Lake Mead, a man-made reservoir, levels are at near-historical lows, which is compounded by human reliance on the reservoir and extreme drought conditions. This not only has an effect on human usage, but also the freshwater ecosystem which relies on sustained water levels.
An economic cost is also generated when water is removed from freshwater ecosystems for human use. There is significant cost involved for pumping water out of freshwater systems, disinfecting the water so it’s of drinking quality, and piping water to individual households and industries to be used. All this requires machinery, pumps, chemicals, and electricity, to name a few. This cost is paid for by municipalities, taxpayers, and individuals who may be in rural areas relying on well water.
Research has found that the dirtier the water used from a freshwater ecosystem, the more expensive it will be to process and make clean as it will require more chemicals and/or filtration. For example, it was found that a 1% decrease in intake water turbidity will result in a $1,123/year savings in treatment costs. May seem like a little, but when this value is compounded to the 153,000 drinking water plants in the United States, a 1% decrease in turbidity could save the U.S. $171 million annually.
Further, water that is used, wastewater, has to be disinfected and cleaned before returning to the natural environmental, causing significant costs to do so. Some research has found that it costs $87,000 for a facility to treat 1,000,000 gallons of sewage day. Again, that may not seem like much but, when you think that New York City alone produces 1.3 billion gallons of sewage, this would be equivalent to $113 million in treatment costs for the New York Island.
In total disinfecting both the inflows and outflows of water is expensive, and every city/individual is required to do this to keep freshwater ecosystems safe.
How to reduce domestic water intake and effluent usage?
When seeing both the environmental and economic costs of treating water for human consumption, it raises the question:
Does all water need to be of the same quality to be used?
For example, does water for irrigation need to be treated to the same standards as drinking water?
Can water used for washing hands be again used to water a garden?
All these questions have given rise to research looking at water uses of varying quality. And this research has been utilized by select governments across the globe to approve different uses for water quality types collectively known as clean- (clear), grey-, or black-water.
In the remainder of this article, we’ll talk about clean-, grey-, and black-water and their different uses in society. We will also talk about how these water quality varieties could be used to help conserve water and costs into the future.
What is Cleanwater?
Cleanwater, or clear water, is water that will not harm a human should they come into contact with it. Although this could mean many different types of water, cleanwater is water that has been properly disinfected and is ready for domestic use, for tasks such as drinking, cooking, cleaning, and bathing. Other names for cleanwater include clear, tap, potable, domestic, and safe water.
Typically, cleanwater sources are from uncontaminated, springs, wells (groundwater) or treated water (like city water). This would be water that you would feel safe using when it has come out of the tap.
Cleanwater is theoretically the costliest to produce (both environmentally and economically), as clean water must be free of all harmful bacteria, chemicals, and pathogens. This is not to say that all water coming out of a well or faucet is implicitly clean and disinfected. So, please know your water source before you drink!
What is Greywater?
After cleanwater has been used for domestic purposes, it becomes what’s known as greywater or blackwater, let’s cover greywater first.
Greywater is domestically used water without fecal contamination, major toxins, and major pathogens. So, this can be water from showers, washing machines, and some sinks. It is thought that 50 to 80% of all water produced in domestic households could be considered greywater that may be reusable for other purposes. Research has found that about 40% of greywater comes from showers and bathrooms, 27% from kitchens, and 26% comes from laundry and washing clothes.
In general, greywater can be reused for some tasks as it has less pathogens than blackwater (to be discussed). This can have a great cost savings to individuals when compared to using cleanwater for all water usages, like for flushing toilets and irrigation. Greywater both reduces the energy to take in water from areas and disinfect it as clean water, as well as reduces the time and energy to treat wastewater before putting back into a freshwater ecosystem.
It may seem unimportant from person to person, but saving water one household at a time can have an acute benefit on freshwater ecological systems. And when whole cities and industries within that city are reusing their water for select purposes, this can have a major impact on area surface water, ground water, and effluent amounts heading into these water sources.
Storing and Processing Greywater
After cleanwater is used, it has to be collected in some way. This requires some forethought on how the greywater will be used. Some collection tanks exist under sinks as well as in earthen chamber under houses. Piping from greywater holding tanks to new areas of use can then be constructed, like to the toilets of a house for flushing, or in gardens as drip irrigation.
One issue of greywater is that it can have some odors and smells due to the breakdown of organic material within it. As a reminder greywater is not free of all pathogens or human byproducts (skin, hair, saliva, etc.). Bacterial, chemical, and salt build up may occur, rendering the greywater unusable.
In some instances, greywater will have to be treated to remove fats, oils, and other products before being used; a process called source separation. Mechanical (filters, membranes) and biological (bioreactors) treatment processes have been begun to be tested to treat greywater for use in areas.
Some grey water components like salt may be in issue for some bioreactors. Some systems have control centers that will remove greywater from a holding tank if it has been too long. This will prevent greywater petrification petrification and void additional bacterial back up that might be an issue.
Example Source Separation Processes include:
Coagulation and flocculation: this process assists in the removal of colloids. Particles have select charges that can combine to form large coagulates or flocculants that can be skimmed off of the surface or sink to the bottom of a tank. Usually this process requires mixing to make particles and charged materials come in to contact with each other.
Filtration such as the use of sand and gravel can be effective at removing bacteria and larger particles. Other unwanted sources in greywater can also be removed by using activated charcoal, which can bind unwanted times and tramp them in the filter.
Bioreactors: are areas where bacteria is grown, in this case, to breakdown unwanted contaminants within the greywater. This can be both aerobic and anaerobic.
Wetlands: Some researchers have also made constructed wetlands to use the ecology of the plant life to remove unwanted contaminants from greywater such as nutrients, suspended solids, metals, another organics.
Where is Greywater approved for use?
The use of greywater is popular, if not mandatory, in European and Australia. For example Australia allows house-collected greywater to be reused for lawn watering and toilet flushing.
Greywater is gaining some headway in the United States, but is still considered as wastewater in many U.S. areas. However, California Arizona, Connecticut, Colorado, Montana, New Mexico, Oregon, Texas, Washington, and Wyoming have provided some allowance for greywater for some forms of irrigation. For instance, the Utah water quality board in 2004 allowed greywater from showers, sinks, and washing machines to be used in residential drip irrigation. Water from toilets kitchen sinks and dishwater is illegal to use.
As a recap here is the here are some highlighted uses for greywater.
Reduction in water headed to waste water treatment plants and septic tanks.
Less drawdown of water from natural freshwater areas.
Reduction of energy and cleaning chemicals influencing costs.
Reduction in groundwater recharge.
Less disposition of nutrients into water systems.
What is Blackwater?
Black water is domestically used water that contains urine, fecal contamination, and/or high levels of bacteria and organic matter. This would be water from toilets, dishwashers, and kitchen water, depending on its grease and harmful bacteria accumulated during cooking processes.
Dealing with human effluent is no joke and is why cleaning wastewater is necessary before putting it back into the environment. Many diseases like E. coli, shigella, typhoid fever, salmonella, and cholera can be in sewage.
Treatment for blackwater does exist and is commonly used and wastewater purposes. This effluent either goes into a septic system that degrades the sewage with bacteria or other chemical components. Or the effluent goes to a wastewater treatment plant that treats water with a variety of components including bacteria, chemicals, and filtration.
Conclusions:
Think you want to start using greywater? Well, if you live in an approved area, we hope you do consider using it! Check with your local water guidelines to learn more.
Let’s leave off this article with the steps you need to take to start collecting and using greywater:
Step 1: Collect grey water from showers, sinks, and washing machines in a holding tank. **remember to consult with local regulations to see what is allowed for greywater reuse if allowed at all.
Step 2: Incorporate plumbing to holding tank to transport greywater for usage. This could include more advance pumping and filtration, depending on regulations.
Step 3: Use the greywater to irrigate gardens, flush toilets, etc.
Step 4: System maintenance: to have a greywater system you need to perform routine maintenance making sure it is being correctly used and not putrefying. Some systems have certain holding times and there may be parts of a system that may need to be flushed if too much time elapses.
Bonus Step: before the process of collecting greywater can be accomplished, keep in mind what you are putting down your sink. Commercial cleaners that are non-biodegradable, salts, are other bacterial effluent may cause health problems if reused in other areas. For example, drain cleaner may be a useful cleaning solution, but it will wreck havoc on your garden.
In reading this article, we hope you’ve learned a little bit more about clean-, black-, and greywater, as well as the importance of water usage in general. Humans can have an extreme draw on freshwater ecosystems, especially groundwater sources that take time to recharge, a topic we will cover in later articles. Greywater can be a useful alternative to reduce human reliance on freshwater ecosystems. But needs to be used cautiously to keep humans safe from disease. Happy learning!