Introduction

The problem of crop irrigation in Greece is becoming very serious due to the water shortage that is being faced more frequently. In fact it is slowly and steadily becoming more acute with time and it is expected to constitute an important constraint in agricultural production.

The volume of available natural water resource in Greece is estimated to about 14,340 hm3. Greece has suffered seriously lack of water for the last 40-45 years, and periodical cycles of water shortages every 5-7 years due to droughts. About 40% of the total land area of Greece is being irrigated [1]. On an annual basis, the total water demand for crop cultivation is approximately equal to 5,500 hm3 [1]. The total water demand per year in Greece is estimated to be 8,243 hm3, of which 83% is used for crop irrigation, 1% for animal husbandry, 13% for potable use (10% public water supply and 3% for industry and energy production).

Presently, the reuse of TMWW is in a stage of research, aiming at establishing the necessary basis for the safe of this marginal water with the view to protect both human life and environmental quality. However the reuse is starting to be applied in Northern Greece, basically in fibber crop (cotton) not as a routine practice, but as a tentative solution to reduce the effects of recurring drought problems, which appear in Greece every 5-7 years [1].

The investigations on the reuse which have started for the last 10 years include the followings:

(a) Tolerance of forest plant species Myoporum sp., Nerium oleander, and Geranium sp. to heavy metals from treated waste water and of water enriched with high levels of Mn, Zn and Cu [2].

(b) Estimation of crop water needs of various region in Greece and calculation of the quantities of treated wastewater needed in the context of the future exploitation of the wastewater treatment plants (WWTP) in Western Greece.

(c) Several research and pilot projects dealing with wastewater recycling and reuse in Greece [3].

(d) The capacity of the Mediterranean forest species to absorb Mn2+ when irrigated with treated municipal wastewater ([4])

(e) The effect of the treated municipal wastewater (TMWW) on some forest species growth characteristics such as: Eucalyptus spp, Medicago arborea, Buddleia variabilis and Nerium oleander [5]

(f) Effects of TMWW on the accumulation of nutrients and heavy metals in soil and plants, studied in a series of experiments using Alium cepa (onion) and Lactuca sativa (lettuce) as test plants [6].

(g) Interactions between plant macro, micronutrients and heavy metals in soil and in some vegetables (Brassica Oleracea var Italica (Broccoli) and Brassica oleracea var Gemmifera (Brussels sprouts), and Brassica oleracea var, Capitata).

Quantification of the elemental contribution to roots, stems, leaves and sprouts or heads (edible parts). Contribution of the elemental interactions to the accumulation of heavy metals in the edible plant parts [7]. (h) Interactions related to the consumers health such as ClxCd [7]. The relevant research work is under progress.

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