Effects of recycled and grey water on the growth of ornamental shrubs used in urban green spaces of north-western Greece

Abstract

Worldwide efforts for water conservation has led to successful reuse of water for irrigation. This is particularly important for countries that demonstrate water scarcity phenomena as in Southern Europe, especially during the summer, due to increased summer temperatures, low precipitation and increased demands for water for irrigation and tourism. Irrigation of urban green spaces uses considerable amounts of water and water reuse constitutes a sustainable, practice. However, the application of reusable water for irrigation purposes faces the potential risk of exhibiting toxicity in plants, as it usually contains high concentrations of dissolved salts. Therefore, a field study was undertaken at the Technological Educational Institute of Epirus (TEIEP, Arta, Greece) from May to October 2014 in order to assess the effects of irrigation using recycled water and greywater on the quality and growth of ornamental shrubs. Three irrigation treatments were applied to six shrub species namely Abelia chinensis, Ligustrum japonicum, Photinia serrulata, Viburnum tinus, Pittosporum tobira and Thuja occidentalis. Irrigation treatments constituted of tertiary treated wastewater provided by the Municipal Sewage Treatment Plant, grey water captured from TEIEP's facilities and tap water provided by the local municipal potable water supply network. Plant quality (overall status of plant determined by photographs), was rated on a five point scale at regular intervals and plant growth assessed by the measurement of height and mean width, and the calculation of growth index at fortnight intervals. Results showed that the different irrigation treatments affected both the visual quality and growth of plant species differently. Therefore depending on the plant species, irrigation with tap water could be replaced or supplemented by irrigation with grey water or/and recycled water.