Ioannis K. Kalavrouziotis

The site of New Pleurona, a well fortified city of the Hellenistic period, is located in the western part of Greece. Archaeological and geophysical evidence indicates that the city, during its existence, was connected to the sea. The geomorphological changes are linked to the delta's progression of the two neighboring rivers, Acheloos and Evinos. In addition to the city's impressive fortifications, Pleurona had an extensive network of water supply and storage, including one of the most impressive cisterns of the ancient world. The case of Plevrona can be viewed as an example of adapting a city's needs through environmental changes and as a best practice in the use of its water resources.

A greenhouse experiment was conducted during 2010–2011. A complete randomized blocks design was used including seven treatment levels of sludge(tons per hectare), i.e., 0, 6, 12, 18, 24, 30, and “30+ treated wastewater”, in four replications. Lettuce (Lactuca sativa L var longifolia) was chosen as a test plant. The purpose of the experiment was to study the relationships between soil Pollution Load Index, heavy metal transfer factor, and concentration factor and to determine optimum concentration factor values. The following were found: several mathematical relationships were established between the above parameters that could be used for the study of heavy metal accumulation in soils and plants under the effect of the applied sludge. They can be also used for the calculation of one of the above parameters as a function of the others. Based on the experimental data, the optimum concentration factor for several heavy metals were determined by multiple linear regression analysis, expressing the concentration factor as a function of the maximum dry lettuce matter yield, and of optimum/minimum heavy metal content of plant dry matter. The mean value of the calculated concentration factor obtained for each separate metal was: Zn, 2.93; Cd, 0.39; Co, 1.47; and Ni, 0.52.

A greenhouse experiment was conducted in Agrinion, Greece, using a randomized block design, testing five levels of treated municipal wastewater (TMWW), i.e., 0%, 25%, 50%, 75%, and 100% of irrigation water, in four replications. The vegetable Brassica oleracea var. capitata (cabbage) was used as a test plant. The purpose of the experiment was to investigate the effect of different TMWW levels on the contribution of elemental interactions in total macroelement, microelement, and heavy metal content of different cabbage plant parts (roots, leaves, stems, and heads), with emphasis on the edible parts (heads). From the 362 statistically significant interactions, 70.72% were synergistic, 16.85% antagonistic, 8.01% synergistic–antagonistic, and 4.42% antagonistic–synergistic. The highest mean contribution of elemental interactions regarding total macroelements in cabbage heads was observed for potassium (K), calcium (Ca), and magnesium (Mg) with 1256.2, 1022.6, and 155.98 mg/100 g head dry matter (dm), respectively, whereas the lowest was found for heavy metals i.e., lead (Pb), nickel (Ni), chromium (Cr), and cobalt (Co) with 0.642, 0.143, 0.0112, and 0.0046 mg/100 g head dm, respectively. The toxic cadmium (Cd) did not contribute to heads in statistically significant levels.

Soil heavy metal pollution due to wastewater reuse was assessed by means of the concentration factor (CF) and/or pollution load index (PLI).In this respect, a greenhouse pot experiment was conducted, using a completely randomized block design, including five treatments of treated municipal wastewater (0%, 25%, 50%, 75%, and 100%), in four replications. Brassica oleracea var. Capitata was used as a test crop. The optimum CFs were expressed as a function of maximum dry matter of cabbage plant parts yield, and the values obtained per plant part were as follows: stems—Zn-CF 2.96, Co-CF 0.85, Ni-CF 0.92; whole plant—Cu-CF 3.90, Ni-CF 0.87, and Pb-CF 11.52; and leaves—Pb-CF 11.78. The PLI was calculated as the geometric mean of the CF of each metal, and was related to the maximum dry mater yield of cabbage stems and heads. The optimum values found were: stems PLI 1.99–2.55 and heads 2.25.

In the present paper, the possibility of the treated municipal wastewater (TMWW) reuse in agriculture, produced by the Wastewater Treatment Plants of Aitoloakarnania prefecture, one of the greatest agricultural regions of Greece, has been investigated. The boundaries of agricultural soils and the irrigated crops were defined, and the water requirements of crops were calculated. Also the chemical characteristics of the TMWW were determined for the safe reuse in crop production, and for the protection of soils from potential pollution. The research conducted in this area is expected to constitute the basis for an integrated TMWW reuse planning in soils and crops, in the context of sustainable agriculture, and environmental protection. It must be mentioned that the Messolongion-Aitolikon lagoon is in the area under investigation, one of the largest wetland ecosystem of Mediterranean region, which makes the area ecologically sensitive. The ultimate scope of this study is to describe the planning of the TMWW reuse on the basis of soil characteristics, climatic factors, and irrigation water requirements of the crops, grown in this ecologically sensitive area. The volume of the effluents produced by the wastewater treatment plants of Messolonghion, Agrinion, Nafpaktos, Aitoliko and Thermo could cover 19.3%, 25.14%, >100%, 17.18 and 87.84% of the irrigation water requirements, respectively.