I recently attended a reuse symposium, where reuse of various types of water were discussed.
One speaker spoke of how wrong and absolutely risky it is to reuse grey water if not treated before reuse. She was emphasizing the extreme health risk it poses for direct reuse.
A following speaker spoke of how they directly reuse grey water to water gardens and flush toilets in a community project. This speaker said that there are no serious health risks to this application.
We in South Africa are experiencing a serious drought. South Africans are reusing shower/bath water to water gardens or flush toilets in our area.
So my question is - is it safe to reuse grey water for gardening and flushing toilets without treating? What health issues could using grey water in gardens pose? Is there anyone who can shed light on where we can we use grey water without pretreatment?
Many commenters are expressing a lot of unfounded angst, mainly from their inexperience. Actually grey water and other water reuse have been practiced for many years safely. Wastewater is 100% recyclable. Quality standards and appropriate treatment based upon end use are well established. We are not running out of water. We are running out of free or wasted or cheap water in some locations where population demands are overtaxing local natural supplies. Of course, the first principle is to reduce wasteful use. Apart from conservation, which has limits, proper reuse of all types, including potable reuse, is the best opportunity for quantity, reliability and sustainability. The experienced and creative engineers, not the amateurs, know how to do it. The public needs to be informed with facts so they can support the recycling efforts. WHO has new direct and indirect potable Reuse Guidelines coming out this summer. It already has published other water use guidelines.
Does salt increase in those soils often, but slowly? Do pharmaceuticals, or any other potentially toxic chemicals accumulate in some of these soils? Do drip holes gradually plug with deposits?
With regard to grading e.g. flowers, it could be used in restricted area (fenced area) where no access allowed. However you have to bear in your mind that by time the concentration of detergents and other elements will have a detrimental impact on soil and plant's growth.
For toilet flushing you need at least residual chorine -0.5 to 1mg/l to ensure some safety. The danger of not treating and disinfection grey water, by time, will encourage growth in the e.g. toilet tank and toilet tank will be an incubator to microbiological pathogens.
In some country using unauthorized grey water is illegal.
Should you required further clarification, please do not hesitate to contact me.
The toxicology potentials are NOT even known well, because we can not even know effectively just what toxicant actually exist in a given grey water. If you can't really know WHAT to test for in a sample, and many toxicants do NOT even have analytical protocols developed, how can we in good faith due diligence scientific integrity state whether or not a reuse is 'safe'. There will always be reasonable doubt about the safety. 'Safety', is always relative, but we have existential responsibility to use all available caution in public health best management practices. Clean, freshwater scarcity is an immense pressure to shortcut the whole investigatory aspect of due diligence assessment, this is a very important issue. To be more a part of the solution than a continuing part of the problem for public health responsibility, we must all 'doubt, without unbelief, of the things to be believed'. We have great responsibility, and tools that are not yet adequate to use, but must always strive for excellence, while fearing we are not really being adequate. Short of reverse osmosis everywhere, we must strive for diligence. IMHO
we , at huliot in israel manufacture the ClearGrey grey water plants , for the last 5 years . withe 2 kind of systems SBR type , with a secondery efluent qualty . and MBR type system for a tertiary efluent qualty .
My suggestion is to have your Garden as Vertical Wetland, simple easy Wetland will give a proper look of a Garden too. Instead of going to complicated solutions, Vertical Wetlands are the cheapest and easiest solution for such areas where houses have Gardens/Lawns or ample land available.
On the other hands, if you filter the grey water and disinfect (with Chlorine the cheapest disinfectant) and use it for Flushing the Toilets could be a solution.
Quality of grey water depends on the use of water. In areas of low-income people, where water availability is low, and use of water itself is low, the grey water becomes highly concentrated in terms of its impurities. One might think twice before using such grey water.
On the other hand, in areas of high-income people, where water availability is high, and the use of water is lavish, the grey water is diluted and can be reused.
Grey water is most commonly used as an irrigation water source, however, if not suitably treated, this source can contain pollutants (e.g. Heavy metals) that actually cause long-term destruction of the soil fertility
Reuse of Grey water depends upon. BOD .COD etc. hair,impirities. The hair can be removed with simple strainer. Some treatment is required for reuse like sand filtrationetc.
The relatively clean waste water from baths, sinks, washing machines, and other kitchen appliances.Grey water can be defined as any domestic wastewater produced, excluding sewage. The main difference between grey water and sewage (or black water) is the organic loading. Sewage has a much larger, With proper treatment grey water can be put to good use. These uses include water for laundry and toilet flushing, and also irrigation of plants. Treated grey water can be used to irrigate both food and non food producing plants.
The grey water cannot be used in vegetable garden,if you want to water herbs and vegetables you'll need to get a higher level of water treatment. Untreated grey water should definitely not be used on food that will be eaten raw.
Untreated grey water should only be used for sub-surface garden irrigation — that is, through a network of pipes buried at least 1m below the ground – to reduce the risk of human or animal contact.
Following instruction may be follows-
Pipes carrying untreated grey water must display relevant warning labels.
You can't store untreated grey water, because the bacteria and other pathogens could multiply to dangerous levels.
Use it immediately (or within 24 hours), and if it's raining, divert it to the sewer.
If someone in your family is sick with gastro or flu or another contagious disease, stop using the grey water.
Don't use grey water if you've been washing nappies or using bleaches or dyes.
Don't water herbs, vegetables or pot plants with untreated grey water.
Your grey water shouldn't escape from your property into a neighboring one, into storm water systems or aquifers used for drinking water — in fact it's illegal.
Small amounts of phosphorus can be useful for plants, and it's a major component of fertilizer. When it gets into waterways, however, it can cause excessive algal growth, leading to toxic algal blooms. The effect on your soil is varied depending on your soil type. Clay soils can deal with more phosphorus because the phosphorus binds to clay minerals and doesn't leach away. On sandy soils, excess phosphorus can leach into groundwater. Australian soils are typically low in phosphorus, and some native species can't tolerate high levels.
All laundry detergents contain salts, typically sodium salts such as sodium nitrate, sodium sulphate, sodium phosphate and sodium silicate. All laundry detergents are highly saline, and frequent long-term use would likely harm your garden, unless it was spread over a large area.
Health and Safety requirement for using Grey Water: Grey water may contain organisms that are found in black water and may transfer diseases to human beings and present health risk. To avoid these conditions, the following requirements should be taken into consideration:
1. Designing appropriate greywater system according to the estimation of greywater from each household.
2. Greywater should not be stored before or after treatment more than 24 hours.
3. Greywater system must be maintained and operated by a well trained person.
4. Fresh water should be used from time to time to minimize build up of negative effects on soil properties and drip irrigation system.
5. Spray irrigation is prohibited.
6. Avoid direct contact with greywater.
7. Avoid inhalation of spray coming from greywater.
8. Do not use greywater for washing or bathing.
9. It is not allowed to discharge greywater through storm drainage network.
10. The greywater system should be operated and maintained in a well programmed manner.
11. Do not construct the greywater pipes near drinking water pipes to avoid cross contamination.
12. Greywater should not be used in a manner that may result in a direct contact with vegetables or plants eaten raw.
13. Greywater should be used on the site where it is generated household (property boundary).
14. It is advisable to construct the irrigation pipes below the soil to minimize odor problems coming from the greywater.
15. Avoid using greywater if there is a family member with an infectious health conditions.
16. Avoid using greywater discharged or mixed with washing diapers.
17. Avoid using hazardous chemicals in washing activities discharged to greywater system.
18. Avoid making pools resulting from greywater reuse activities.
19. The property area to be irrigated should be suitable to the generated greywater quantity on a daily basis.
Simple steps to reduce the BoD by anaerobic digestion of organic solids reduces the risks of using partially treated grey water for irrigation. Any way, in developing nations, grey water is getting used for irrigation even though we call them rivers sources !
Query by GDarries on re use of grey water. If the treatment has remediatoin done by plants in its later stages then these davrificial plants will reduce the BOD levels. A bit of sun exposure takes care of curing and UV rays to part sterilise the treated water. When this water is used for plants then the veggies grown to be consumed with caution...st best deep fry them avoid eating thrm raw or in boiled form... w wshs ...