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?
The speaker who was opposed to reuse had no idea what she was talking about. Water can be reused for any application with appropriate treatment and finished quality. The treatment and quality specifications are determined by the end use and human contact potential. The World Health Organization released guidelines for direct and indirect potable reuse. You can find them on line at www.who.int/water reuse. There are numerous large scale reuse projects in operation and many more being planned.
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Many health jurisdictions in North America permit single-family residences to recycle ( i.e. without treatment) greywater (typically defined as bath/shower, lavatory and laundry drainage) for direct shallow (within the root zone) subsurface irrigation. There are two Canadian municipalities that allow recycled greywater to be used for toilet flushing without treatment by capturing bath/shower water and pumping it to the toilet as required. These are "smart" systems that drain the stored greywater to sewer if the storage time exceeds 24 hours, automatically top up the water in storage with potable water (if required), and have UPS power supplies in the event of a power failure. This simple practice could save up to 30% of a household potable water demands and reduce the volume of wastewater generated by the same amount without the burden of treatment costs. The principal impact on the household is a more frequent need to clean biofilm from the toilet tank and bowl. The expressed concerns I have heard are primarily related to the potential for disease transmission as a result of a person coming into contact with droplets of water as a result of flushing. However, common sense dictates that fecal deposition and bowl contamination from previous users of the toilet are a significantly greater health risk -one that we accept, particularly with respect to public toilets. Further, intuitively, we can appreciate there is a much greater risk of disease transmission within a family as a result of interpersonal contact and food preparation, that there is with incidental potential contact with bath water used to flush a toilet.but
Here is a link to the ConservePump greywater recycling system that was manufactured by iDUS Controls designed to recycle bath/shower drainage for toilet flushing. I am not sure the company still actively markets the technology, but the link provides information on how the system functioned. It was installed in homes in Nanaimo, British Columbia, and Guelph, Ontario, Canada.
An International Association of Plumbing and Mechanical Officials (IAPMO) committee developed a small-scale residential greywater recycling performance Standard 1207, in 2014, that failed to receive approval because of unfounded concerns the practice posed a health risk.
The Sloan AQUS system also directly recycles greywater from lavatories for toilet flushing without treatment, but does incorporate a simple chlorine puck system for disinfection.
The surfactants and synthetic chemicals would have a negative impact on the environment. Especially in our rivers and oceans. Please visit http://www.goesfoundation.com/ to see why. This is why I do not recommend reusing grey water without treatment.
Modern pharmaceuticals and other chemicals are becoming increasingly harder to breakdown. The government here considered this a few years ago. I would recommend otherwise until we learn how to treat these new chemicals.
Hydrodynamic cavitation could be the key, we have successfully removed 91 agricultural chemicals for a drinking water project here in Australia recently.
A membrane bio-reactor could be used although, the bacteria may not survive if concentrations of synthetic chemicals are too high. We have had a successful reuse project in China using this method of treatment for a hotel. The treated effluent is resued for their toilets and wash basins.
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by Andrew Tran, Engineer
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The Goes issues are generally irrelevant to recycled greywater. Recycling actually reduces transport to waterways and oceans, Soil applications allow soil bacteria to degrade many chemicals, about as well as sewage treatment plants. Recent pharmaceuticals are not more or less degradable then older ones. The most relevant question is whether certain substances would be taken up by food plants. Of course, waste recycling has been used for perhaps thousands of years, but it is probably better to avoid use on food plants, primarily because of possible pathogen recycling, if the wastewater or night soil has not been composted or sterilized. There are standards for that.
Yes, we need to reuse water, we often CAN get away with it. However, our ignorance is still very great, risks abound, and we always need to reduce our ignorance. Fortunately, ignorance can be fixed.... with enough new knowledge to gradually identify and reduce the harm. On the other hand, you can't fix "stupid' as easily. Science is the key, and is always increasing, always needed, and is essentially never done. We, far too often, assume 'safety' when we are short-cutting the science. When we take scientific shortcuts, we always need to acknowledge our ignorance, try to decrease it, and fear our hidden stupidity.
This is a complicated subject, and there have been some very good comments, reuses a huge need in many geographic areas. We have created about eighty-five thousand chemicals mostly new to the environment, to put into products we have been using, these products are dispersed around the world to eventually degrade often becoming pollution. Very few have had adequate toxicity testing done. Water is a solvent and transporter of most of these chemicals. Grey water is contaminated by a huge number of these chemicals, but highly variably. We have not even developed test protocols for identifying multiple thousands of these contaminants. Extremely low doses of many chemicals can have adverse biologic, and pathogenic, effects that we are unaware of of even having, let alone ascribing causation to. Some of these chemicals are accumulative in our bodies. They can be additive in adverse effects, and even synergistic in subtle-but-persistent low dose effects as mixtures. Science is able to look at many toxic effects of many of these chemicals, but does not do a very good job of identifying toxic effects of mixtures of them. There are huge gaps in our knowledge of the toxicologic effects potentials and our ability to tease out the risks in grey water that is highly variable. Anything we can do to gain additional knowledge about these very real health risks is going to become even more essential as clean freshwater becomes increasingly contaminated by our products. The science is critical, we are harming ourselves and others, but often it is very subtle to determine adequately.... we are not very good at this yet... but we must keep getting better at it rapidly IMHO
Hello and Bravo for your post. The side effects of all these chemical additives should not be minimized. The best solution is to eliminate them at the source.
There has been so many mix reviews regarding the topic at hand and I thank each and everyone for your participation. There are no clear yes or no's BUT what I gather from all the replies is that:
Yes, you can re-use gray water but Pre-treatment is IMPORTANT and Direct re-use is not advised.
Hello I do not know which sources come from the yes for the reuse of greywater. Ray Kinney's post should still enlighten you on the subject. Reusing greywater is a crime against humanity. No one can assure that these grey waters do not contain very toxic products. As the only treatment to date of greywater is of the order of filtration, no device is able to eliminate dissolved pollution. Everything alive on our planet feeds on organic. is a water impregnated with undetermined chemical molecules biological?
As grey water does not contain poop, urine, and too much contaminants, it can directly be used for watering gardens and other landscape uses. But, I'm really not sure if grey water poses threat to human health when using for flushing toilets.
We go for the lightest one, starting by (retrofit) upgrading the upstream biological treatment as to achieve ultralow residuals. This enables the highest water quality after UF + NF/RO as demonstrated at full scale in a sewage to drinking water project via ground water recharge under strict HACCP. The quality of the drinking water at the tap and its taste improved significantly in all parameters since this was project was completed in 2006.
In the 1970's I lived in Livermore, California, which is somewhat arid. As is often the case, there was a drought and water use was being restricted; could not water the grass or wash your car.
I set up a gray water system for my lawn and garden and used it for several months. Since my lawn was very green, I had the pleasure of a government water company official pay me a visit accusing me of violating the restrictions. I showed her my system which didn't impress her. She stated that the wastewater facility depended on the gray water to dilute the black water solids and that I needed to stop my reuse.
I did stop watering the lawn, but did keep using it in my garden.
I wouldn't advise using the grey water untreated like previous comments, however, there are good filtration systems. Not to turn this into a sales pitch but we have a system developed utilising organic filters that treat most of the nasties. This is in progress with United Nations and UNICEF currently.
I would be more than happy to have further dialogue with you. Let me know if you this would be of interest. Thanks in advance.
Using grey water to grow crops in constructed wetlands placed and planted sequentially may be an answer. Prairie grasses are excellent phytoremediators of heavy metals and can be used for gasification to produce energy while capturing the metals. A series of 5-6 sealed constructed wetland bays with gravity flow following the grasses that are planted with crops matching declining nutrient needs and increasing salt tolerance (EC) may completely remediate pathogens on root surfaces, consume most of the effluent, prevent groundwater contamination, and prevent alkali soil conditions. Remaining phyto-treated water could be used for groundwater recharge. Edible portion of crops would not contact pathogen contaminated water, no aerosols would be generated, and CEC's would be remediated by energy crops.
Water-Energy-Food--solution for one is the solution for all.
Answers below address issues of pathogenic aerosol from application methods, pathogenic contamination of edible portions of crops, and plant uptake of solubilized heavy metals--all of concern. One must also note that alkali conditions can damage soils in dry climates--most grey water contains high levels of salts , and over application can contaminate ground water sources--NO3-.
However, grey water is a great source of irrigation water for many reasons: contains nutrients, source of water in drought, use reduces eutrophication of receiving waters...
Aeration helps to reduce pathogens, subsurface irrigation reduces chances of contaminating edible portion of plants (changing water sources 15 days prior to harvest is common), and source testing can identify heavy metal polluters. (e.g. itai itai).
Hydroponic methodology can eliminate damaging soils with alkalinity or heavy watering during seasonal wet periods.
More care in using fresh water will reduce the issues encountered by recyclers.
Water-Energy-Food, the solution is obvious, reusing water.
Here in California we have very strict greywater reuse stands where all of it has to be treated for biological contaminants and other constituents of concern including heavy metals, suspended solids, etc. before final end use which at this time is only for non-potable non-crop landscape irrigation. There isn't sufficient studies and data as of yet showing that it's safe to reuse for potable water reuse. In my job as an Environmental Engineer we've only had a couple of greywater treatment system applications for landscape irrigation reuse and even with that the reporting requirements are very strict due to potential for public exposure with the sprinkler system spray. So it really depends on a project by project basis for feasibility of greywater treatment for reuse but 99.9% it has shown to be safe for non- potable landscape irrigation reuse when treated properly.