عنوان المقالة:Optimisation of extensive wastewater treatment systems under Mediterranean conditions (Morocco): compared purification efficiency of artificial ecosystems
Radoux M, Cadelli D, Nemcova M, Ennabili A, Ezzahri J
الملخص العربي
The Mediterranean coast of Morocco is characterised by very fast urbanisation. One of its major consequences is the high pressure on the demand for water and the impact on the environ ment, mainly wetland degradation, microbiological contamination of bathing areas and high contamination of rivers. The water management institutional framework, formerly a public body, now operates water services in Tangiers and Tetouan through a 25-year private concession contract. Wastewater management will be one of the major activities that have to be undertaken in order to restore and to improve the coastal and freshwater quality. Within that framework, the use of well-designed and high efficient extensive wastewater technologies can provide subsequent economic advantages (low-cost investment and cheaper operational costs) and can contribute to protecting the environment and ensuring safe water resources (re-use of treated wastewater for agricultural purposes. The purpose of the MHEA® Experimental Centre located in M'Diq is to develop the most appropriate, simple and low-cost reliable extensive wastewater technologies by means of comparative studies and optimization processes. An initial 2-year comparative test was carried out in 1998/2000 in order to identify and to assess the purification efficiency ofthe main types of ecosystems. The testing procedure compares 8 distinct systems made up of 3 successive levels. With 1 PE (person equivalent) = 70 L d-l, the net treatment area of a single system is 2.3 m2PE-1 (level 1: 0.84 m2PE-1; level II: 0.73 m2PE-1; level III: 0.73 m2PE-1). The first level is common to the 8 systems and consists of a shallow pond while levels II and III make it possible to compare the purification efficiency of aquatic, semi-aquatic and terrestrial ecosystems, whether planted or not. This paper presents the main results concerning the efficiency of primary (suspended solids), secondary (COD and BODs), and tertiary (nitrogen and phosphorus) purification and disinfection during the second and the third year of operation (from January 1999 to 5eptember 2000). - The shallow pond (level 1) demonstrates, under Mediterranean conditions, similar results to the ones already shown under temperate and 5ahelian climates. In Morocco, it confirms its key-role in removing suspended solids and organic load. As observed under other climatic conditions, its inefficiency to reduce tertiary (nitrogen and phosphorus) pollution is also confirmed. - At the second level, aquatic and semi-aquatic ecosystems present similar results while the terrestrial ecosystems show the best removal efficiencies in relation to suspended solids (55) and the organic load and make it possible to achieve high quality standards for tertiary treatment. - With regard to the third level, the purification efficiency of aquatic, semi-aquatic and terrestrial ecosystems presents more variations and must be clarified for each ecosystem, it should be highlighted that each system makes it possible to reach or to exceed the E.U. 91/271 directive standards for sensitive areas. - With regard to disinfection, the efficiency of the shallow pond (level1) remains low (1 log10 unit reduction). The aquatic and semi-aquatic ecosystems tested at both levels II and III present a similar efficiency (1 log10 unit reduction for faecal coliforms and 0.5 log10 unit reduction for faecal streptococci). But, on the other hand, terrestrial ecosystems show a very high disinfection efficiency ranging from 2 to 4 10g10units of reduction at each level for both faecal coliforms and streptococci. These initial results led us to design a second experimental protocol. It has been operational since April 2001. This programme is expected to provide the structure for one or several MHEA® technologies adapted to the South Mediterranean socio-economic and environmental context. Keywords: Arundo donax, disinfection, MHEA® System, Morocco, wastewater treatment.
تاريخ النشر
20/07/2003
الناشر
J Vymazal (ed.), Wetlands: nutrients, metals and mass Cycling, Backhuys Publishers, ISBN-13: 978-9057821400, Leiden, The Netherlands
عبد السلام النبيلي | Abdeslam Ennabili | 5753