A member of the community from the Mnyamtsini area in Swaziland (Mrs. Jabu Dlamini) built this (attached photo)grey water dam entirely on her own. She invited us after she completed the facility. She is a regular participants of our Dry sanitation and waste management project. This is the second grey water disposal facility built within the community. It shows how simple the setup is to build.



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For those who asked me about the detail of the design of grey water dam that i posted here, i have published the research in the Journal of Water Resource and Protection. Below is the link to the publication and you can download the pdf file from this site:

www.scirp.org/journal/PaperInformation.a...D=50581#.VEVjgxaQ4hA

I have also attached the pdf file here.


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Dear HA

Thank you again for the information especially on detergents and on the need for monitoring the use of chemicals in washing. I also agree with your suggestion and with that of Mohammad as well. The problem may also occur at a later stage due to accumulation although apparently for now the plants seem to grow well.
Best regards
Ababu

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Dear Mohammad:

Thank you again for your points. I quite agree with you on the need to look at quality of grey water from broader perspectives in context of grey water reuse because the chemical hazards may also affect the growth of plants.

Best regards
Ababu

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Dear Ababu, dear Mohommad,

thanks for your detailed explanations from my side, too, Ababu. I would agree with Mohammad that risks are also coming from the chemicals used in detergents. I think it is essential that these are biodegradable, otherwise they can accumulate in the soil and affect the growth of the plants. I have heard of cases where plants that have been irrigated with water from washing clothes or dishes (I don't quite remember) have died. But then, many people are totally overusing such products and are using much more than what is required. In any case, we should strive that detergents are completely biodegradable (and not just partially as may be the case for many such products), and then teach users about the appropriate dosage.

In fact detergents have been my biggest worry when I have constructed my grey water garden, but it has turned out to be unfounded looking at how healthy the papaya plants are growing. But then, we attempt to minimize the use of detergents and only buy good brands (even though an investigation about biodegradability would be very helpful).

Kind regards, H-A

Dear Ababu

Thank you so much for your comprehensive explanation , I am very interested in water recycled and reusing on bio remediation and wetland based but I am laboratory technologist as well as I teach material safety data sheet(MSDS) to university students (B.Sc.M.Sc and (Ph.D)
yes you work on grey water ,but today kitchen washing(Dish washing) and laundry washing manufacturers widely use of Enzyme and other strong chemical in their formulation which I wrote in my last mail are not biodegradable I believe for any waste water treatment in addition pathogen bio hazard ,chemical hazards determination must be lunched because their risk are higher(long term) than bacteria pathogen(short term) which I believe they will removed with considering growth log (limitation of nutrients ,competition with aerobic non pathogen bacteria) in water dam and wetland.
and yes the water dam is being to used for irrigations but we face with ecosystem chain ,Plants ,human being and animal so we must be assured of (integrated) total safety in waste water treatment although I am sure dam process reduces chemical hazard but in how extend?
In conclusion I congratulate you for your innovative design which I am very interested in it because of it wide applicable in water scarce region.
Thank you again for your mail.

with best regards
Mohammad

Dear Mohammed:

Thank you for your interest in the grey water dam. Yes quality and characterizing the possible health risk is part of our research concern. We believe the grey water dam set up provides a better barrier against pathogen compared to the vertical grey water tower because the grey water tends to get soaked up in the vertical grey water tower from my experience. We are not including fecal and urine wastes in the dam. We are using grey water. We do not therefore anticipate heavy metals, pesticides, urine products such as endocrine disruptor, hormones, etc as some thing to worry about assuming of course grey water that is being used in the grey water dam comes from the kitchen, baths and washing and some control is exercised although cross contamination is possible. The effect of BOD/TOC is indirect in the sense that bacterial count may increase with availability of organic matter in grey water. However, there are not many documented cases of effects of chemicals on grown plants from grey water application although i do not mean to discount that. How much of these chemicals ends up in the plants is another question because the risk is in eating the plants unlike drinking water and this risk might be low because plants do have barriers. While some control on what should be taken to the dam is necessary and while pretreatment might be considered to improve the water quality going into the grey water dam, we, however, think that our main concern in relation to the grey water dam should be pathogen risk (bacteria, virus, protozoa and helminth) because grey water might contain pathogen although to a lesser degree compared to fecal waste. The grey water dam can be considered as a form of restricted irrigation and the WHO guideline of achieving 3-4 log reduction of E.coli ( 99.9 and 99.99% removal)within the soil in addition to <1 helminh/egg per 100gm of soil with an infection risk of 1 in 1000 might be the appropriate guideline to apply. The most probable risk is in our case direct ingestion of the soil containing pathogens in the course of dealing with harvesting plants and maintenance or contamination of plants by the soil and here proper hygiene also plays a role. There are reports of 2-7 log removal of ecoli by soil depending on how fine the soil is and in this connection we would like to see how the mixture of ash, manure and fine/coarse mixture we used fares in terms of pathogen removal.There is a need to establish the effectiveness of the grey water dam soil as a pathogen barrier.

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Dear Ababu

your design is very interesting but I have sebstain similar questions about its safety do you had any output analysis for example TOC (Total organic Carbon) for washing material use in laundry, bath in both shampoo ,soap, washing powder ,etc) heavy metal ,TOC and BOD , you know there are household material which are not biodegradable and will accumulated in both biological environment (human being ,animal, plants) and even ecosystem and environment such TOC ,Heave metal ,pesticides and addition medicine residual is execrate from Urine or fecal.

your design very interesting and easy practical for rural area.

Regards
Mohammad Mojtabae

OK, thanks for the clarification!
H-A

Dear HA
No the planted filter is supposedly a horizontal flow filter. We control the outlet pipe to regularly lift the water level and lower it to allow alternately water and air into the root zone. I also suspect the root zone might be anaerobic but the plants do grow still as u said. The soil has some manure in it. We are thinking of chlorination for other household uses such as laundry, cleaning, etc. where there is a health risk tat should not be ignored just because it may not be as high as toilet water and not for plantation. From the way it appears, the effluent water after chlorination may achieve a potable quality in terms of aesthetic acceptability and pathogens risk.
Ababu

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Sounds as though the planted bed works like a vertical flow filter - did I understand that correctly? Regular vegetable plants like cabbage, etc. cannot grow if the root zone is anaerobic, but if the bed is allowed to drain on a regular basis, it wouldn't be anaerobic. Looking at the photo, the plants seem not to do too badly. If you've put a soil that doesn't contain much humus or compost, I wouldn't expect them to grow very well.

And do you need to use chlorine on treated grey water - it shouldn't be necessary. But I understand you concern about odors.

H-A

Dear HA
Concerning the quality coming out of the planted filter, i take your suggestion on board as one possibility. We would carry out quality analysis along the treatment line inclding the nutrient inputs and outputs.However, grey water BOD is also high, contains a significant organics especially the ones from the kitchen. I am wondering if it would not be possible to produce soil compost from grey water rather than try to grow plant on it directly. However, we still have a significant problem in the planted filter. In the first drum we put floating plastic media (for ease of cleaning) as anaerobic growth medium but packed during treatment. The second drum is sand on grave support. The effluent from the two drums flows through the panted filter that contains gravel at the bottom followed by sand and soil at the top. The effluent after all these in the end is very clear but quite odourous and not acceptable for some types of reuse. We were thinking of adding charcoal and sand as an additional treatment to reduce the odour. We also have put a number of vertical pipes down the level of the gravel bottom in the planted filter for aeration and release of gases but the growth of plants is still limited. The entire scheme ( the drum filters plus the planted filter) is anaerobic. Part of the problem in growth of plants could be lack of mineralization of nutrients. It is a little difficult to adapt aerobic treatment of waste water at household level with limited space. Some of the prescriptions of grey water treatment in the literature may not be as good as they appear to be assuming of course we were not wrong in copying them. For other types of reuse how much chlorine demand the effluent has is some thing we want to investigate.

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