A non-partisan, neutral perspective supporting diversity in the color of water

Saturday, June 16, 2012

Less FUDing, More Growing with Greywater

While enroute to Norwich, England for a workshop in Water Security, the KLM airline magazine ran an ad for Plantagon, a living building and urban agriculture venture based in Sweden. The Rainbow Water Coalition has posted many times on the race for the best and biggest living building, highlighting some of the home-grown varieties such as the incredible work by the Moon Brothers and the doomed, but still apparently gasping, Oregon Sustainability Center. Living walls and roofs are common attributes of the living buildings. So are gardens, both for the amenities and treatment of greywater, glitz, and growing food in vertical farms.

The Plantagon Greenhouse can be integrated into existing or new infrastructure to increase the efficiency regarding use of water, waste and energy. The quite simple innovation is to use the full volume of a high-rise greenhouse, but to grow in the plants in a turning helix, thus maximizing the growing conditions for the each plant. The controlled conditions of the greenhouse also minimizes the use of water, energy and need for pesticides. The greenhouse will deliver fresh high-quality food directly to consumers or starving citizens of the third world. The Plantagon Greenhouse will dramatically change the way we produce vegetables in urban areas. 

So, what about this issue of greywater and growing food? Much hand wringing and FUDing has been expended in Oregon over just how far one can go with reusing greywater to grow food, especially regarding the issues of what parts of the plants can be "touched" with greywater, or can be consumed if irrigated with greywater.

Leave it to yet another great greywater thesis to address these issues.

Health risk of growing and consuming vegetables using greywater for irrigation by Siobhan Ann Forbes Jackson at the University of KwaZulu-Natal, South Africa


Two of the challenges facing Africa in the 21st Century are effective use of restricted water resources and ensuring food security especially for poor communities. In line with these aims, the eThekwini municipality has introduced a multi-tier system of water supply ranging from full pressure reticulated systems along with flush toilets to standpipes and dry toilet systems. In the latter case, it was soon recognized that the disposal of greywater presented a problem. Bearing in mind that South Africa is already a water scarce region, research was initiated into finding means of using this water as a resource rather than as a waste. Initial on-site trials using the greywater to irrigate crops proved popular and it was then regarded as necessary to test the possible health effects on the communities of such a system. A controlled field trial using pot plantings of a selected range of edible vegetables was initiated at the University of KwaZulu-Natal. Crops were tested both internally and externally for a range of indicator and potentially pathogenic organisms. Quantitative Microbial Risk Assessment (QMRA) techniques were used to assess the health risk to communities from growing and eating the greywater- irrigated vegetables. Although there was a health risk related to most of the activities, especially the handling of the greywater itself, the risks could be brought within the World Health Organisation guidelines of less than one case of disease per 10 000 people per year by the implementation of simple barrier interventions. The greywater irrigated crops themselves, did not present a statistically higher risk of infection than the crops irrigated with either hydroponic solution or tap water. These findings show the importance of applying QMRA to each case to determine health risk. This would allow the productive use of greywater and other water sources in the correct circumstances, thus providing food sustainability for people who currently do not have access to the levels of high purity water currently recommended for agriculture.

What is missing from the research, you ask? Not much, as the thesis indicates more work needs to be done regarding viruses and residual personal care products. But don't some of those same issues reside with tap water, too?
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Urban Agriculture is a concept that restores our common knowledge of a cyclic system of life and its necessities. We cannot distance ourselves from the resources we need or the waste we produce. 

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