Stanford CEE 215: - Microbiological assessment of food crops irrigated with domestic greywater

Unformatted text preview:

700Available on website http://www.wrc.org.zaISSN 0378-4738 = Water SA Vol. 32 No. 5 (Special edn. WISA 2006)ISSN 1816-7950 = Water SA (on-line)This paper was originally presented at the 2006 Water Institute of South Africa (WISA) Biennial Conference, Durban, South Africa, 21-25 May 2006.* To whom all correspondence should be addressed. +2731 311-8015; fax:+2731 311-8003; e-mail: [email protected] assessment of food crops irrigated with domestic greywaterSiobhan Jackson1,2*, N Rodda2 and L Salukazana21 Durban Metro Water Services, Wastewater Management Laboratory, PO Box 1038, Durban 4000, South Africa 2 Pollution Research Group, University of KwaZulu-Natal, Howard College, Durban 4041, South AfricaAbstractTwo of the challenges facing Africa in the 21stcentury are effective use of restricted water resources and ensuring food security. The eThekwini Municipality is not exempt from these challenges and is investigating ways in which they can be addressed in the local context. One of the aims of national government has been to ensure the supply of clean drinking water and suitable sanitation to every household. As part of its efforts in this regard, eThekwini Municipality has introduced a multi-tiered water supply programme ranging from full-pressure water systems and flush toilets to stand pipes and dry toilets. In the dry sanitation systems, there is no real provision for the disposal of domestic greywater and, bearing in mind that South Africa is a water scarce country, the municipality is investigating ways of using this water as a resource rather than viewing it as a waste. A preliminary trial was set up in 2003 using this water to irrigate vegetables to be used for home consumption. The microbiological safety of this practice needed to be examined to ensure that it would indeed help to uplift communities by the provision of healthy food as well as provide an ecologically sound use and reuse of available water. The initial proposal was to investigate total coliforms, E. coli and Enterococcus as the normal faecal indicators for health purposes as well as Staphylococcus as a human skin surface micro-organism and coliphage as a viral indicator. The first controlled field trial was put in at the test site at the University of KwaZulu-Natal in 2005 using several crop types and three irrigation regimes. The vegetable samples were examined both internally and externally for the selected micro-organisms. It was found that very few E. coli were detected and in later crops the micro-organism list was expanded and further identifica-tion of the total coliform organisms detected is being addressed. This paper presents the results from the analyses to date. Keywords: greywater, irrigation, health risk, domestic cropsIntroductionA previous Minister of Water Affairs and Forestry expressed the wish for water in South Africa that there would be ‘Some for all, forever’. As the Southern African region is recognised as a water scarce area, action needs to be taken to ensure that this wish is fulfilled. As a leader in the water supply arena in this country, the eThekwini Municipality was the first to implement the concept of 6 kℓ of free water per household per month. At the earliest stages of implementation of community upliftment, the feeling in the communities was that one of their highest priorities was to receive potable water; the aspect of sanitation came much further down on the list. This led to the situation where communities were receiving water but had no formal means of disposing of it after use. In many instances, water was thrown outside the door of the residence resulting in pooling and unsanitary conditions including the breeding of mosquitoes. In any sanitary intervention the Bellagio Prin-ciples (Hurst, 2002) need to be kept in mind to ensure accept-ability and sustainability of the intervention. In addition, Kwa-Zulu-Natal has the highest HIV positive rate in the country and the eThekwini area is certainly not exempt. In many cases, the family bread winner is either dead or dying, households are headed by children or aged grandparents and finances are at a sub-economic level. As a result, the nutritional status of the household can be extremely poor which results in increased susceptibility to disease and a further drain on resources. An opportunity was seen for the re-use of greywater which could result in an improvement in the living conditions of these fami-lies. In 2003, a preliminary trial was set up using greywater to irrigate above-ground vegetables to be used for home con-sumption. The crops produced appeared to be excellent and the community involved wanted to expand operations. There was some doubt, however, about the hygiene of crops grown under such conditions and whether there needed to be some restriction in the type of crop grown. A joint project between eThekwini Water and Sanitation and the University of Kwa-Zulu-Natal was initiated to investigate these issues.Experimental designA semi-field trial plot was established at the University of Kwa-Zulu-Natal in which it was originally planned that four crops would be planted. During the course of the year additional veg-etables were added and the final selection was: spinach, green peppers, madumbis, potatoes, onions, beetroot and carrots. These were grown in plastic bags filled with sterile, low nutrient Berea red sand and drip-irrigated through a plastic bottle with either normal municipal tap water, greywater or a hydroponics solution. Irrigation through plastic bottles pierced at the bottom was to prevent splash back contamination of above surface growth as far as possible. The vegetables were watered daily with 500 mℓ of the relevant solution and harvested at maturity, after approximately three to four months. A rep-Available on website http://www.wrc.org.zaISSN 0378-4738 = Water SA Vol. 32 No. 5 (Special edn. WISA 2006)ISSN 1816-7950 = Water SA (on-line)701resentative sample of each crop was dried, the percent-age dry mass of each sample was calculated and used to calculate bacterial load per dry mass. Fresh samples were weighed and placed in 100 mℓ of sterile Ringer’s solution in a sterile jar and shaken on a platform shaker at 220


View Full Document

Stanford CEE 215: - Microbiological assessment of food crops irrigated with domestic greywater

Download Microbiological assessment of food crops irrigated with domestic greywater
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Microbiological assessment of food crops irrigated with domestic greywater and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Microbiological assessment of food crops irrigated with domestic greywater 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?