Growth of Flax Plants (Linum usitatissimum) as Affected by Water and Sludge from a Sewage Treatment Plant

Abstract

Compliance with the European Union regulations (European Community 1991) resulted in the construction of numerous secondary treatment Sewage Treatment Plants (STP) in many maritime cities of Greece. Thus, the production of sludge and wastewater dramatically increased and various solutions concerning their disposal or utilization are under investigation. Sewage of these cities, where the activities are limited to agriculture or tourist services is characterized by the lack of heavy metals and toxic substances and the utilization of the STP products in various ways seems unthreatening to the environment. Yet, both wastewater and sludge are characterized by high microbial loads. Water has to be sterilized by chlorination prior to any disposal. Sludge keeps the high microbial load and, although rich in inorganic nutrients, has to be treated carefully.

The effect of sewage sludge application to agricultural soils has been investigated, mostly in industrial countries (Raven and Loeppert 1997; Towers and Home 1997). The effect of treated domestic and industrial effluents on plants have also been investigated (Hooda et al. 1997; Logan et al. 1997; Palacios et al. 1999; Samaras and Kallianou 2000; Weir and Allen 1997).

Respecting the restrictions imposed by the E.U.’s directive (European Community 1986), but also taking into account the exhortation included for further investigation, we launched a project to find out how water and sludge could affect plant crops of great economical importance (Margaris et al. 1995). Corn (Christodoulakis and Margaris 1996) and cotton plants (Tsakou et al. 2001a) cultured in sludge amended agricultural soil were monitored during the culture period of concern to various developmental parameters. A comparison to plants cultured the conventional way led to interesting results (Tsakou et al. 2001a, Tsakou et al. 2001b). Having in mind: a) the global interest for reducing the use of chemical fertilizers, b) the great financial value of plant fibers, and c) the fact that non edible plants are preferred for this kind of experiment, we continued our investigation selecting flax (Linum usitatissimum). Our interest remains focused on the study of the impact that sewage sludge and wastewater have on the phenology, growth, productivity, and heavy metal accumulation of these plants.