Greywater Overview

Greywater is a type of wastewater that makes up a large percentage of the total water consumed by an individual in the course of their life. Wastewater is classification of water that includes anything that leaves a house through the sewage pipes after being used in some way. This sort of water is generally broken down into two categories depending on the severity of contamination, with blackwater being septic water that has been exposed to direct human waste, while greywater is simply wastewater than is less contaminated. Both gray and blackwater are the end result of the use of ‘whitewater’ which is clean, potable water that comes to a house from a well or municipal water system.

Grey Water vs “Blackwater” (waste water)

Outgoing greywater makes up around 50 to 80 percent of residential waste water, with the remainder being sewage or blackwater. Things like a dish washer or laundry machines are examples of greywater sources, as they don’t contain human waste but are no longer drinkable.  Greywater is usually devoid of any contaminants besides food wastes or chemicals from cleaning agents. Cleaning greywater is far less intensive than purifying blackwater with human waste in it, as it lacks most of the bacterial contaminants that require extensive cleaning activity.

While greywater is relatively clean, it is no longer potable thanks to the presence of contaminants. And greywater does posses some of the bacterial activity that makes blackwater dangerous to humans. Given enough time and the right conditions, greywater can turn into blackwater if it’s left standing for more than a couple of days.While greywater is not clean, it is far easier to purify than blackwater. The large amounts of greywater produced by an average household, coupled with the ease of purification, has lead to a great deal of interest in different methods of recycling greywater. Effectively sequestering the greywater from more dangerous wastes would allow a drastic reduction the amount of water consumed, which is a very desirable outcome for environmentalist and economical homeowners alike.

In a normal household, water comes in from a well or water system and gets used for all sorts of things, like laundry, showers, dish washing and more. All of this greywater is flushed out of the household along with blackwater to flow into the local sewage system (or septic tank for more rural homes). The water is then run through a treatment routine or allowed to filter out depending on the specific system. Because the mixture of black and greywater has to be treated as if it was heavily contaminated, the mixing of water types ends up wasting a large amount of water.

Recycling systems separate gray and blackwater sources from each other and then disposes of the blackwater in the normal way. The greywater is kept separate from its more contaminated counterpart and then treated or recycled in various ways. These systems can drastically reduce water consumption by recycling or reusing the water locally after making sure the water is made hygenic by different techniques.

Greywater recycling is broken into two basic types: treated and untreated. Untreated greywater recycling is often used to provide water for agricultural activities like growing trees, or other areas where water potability is not a prime concern. Some recycling systems use greywater for irrigation, but the legality of untreated greywater recycling depends on a variety of factors and is varies from location to location. These untreated systems are generally called ‘diversion systems’ because essentially they just keep the gray and blackwaters separate from each other. Diversion systems can be built into new construction or retrofitted into an existing home.

Recycling systems that treat the water are further broken down into hard and soft types. Soft recycling systems rely on naturally occurring phenomena like sand filtration or biological processes like treatment ponds or manufactured wetlands. Hard systems are based around technological purification systems like distillation. There are numerous recycling systems based off of soft recycling techniques, but there are almost no hard systems available for recycling greywater appropriate for use on a household level.

Greywater recycling is an important subject considering the rapidly decreasing sources of potable groundwater in the United States. Water conservation is becoming a hot button issue in a number of areas where rainwater levels are down or population increases have driven up water consumption. Greywater recycling, though a complicated process with lots of different legal implications depending on your locale, is an effective method of addressing water consumption issues and improving the environmental footprint of a given household.