My Aim in Life

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ARTICLE IN PRESS
Microbiological Research 161 (2006) 93—101

www.elsevier.de/micres

Changes in microbial and soil properties following amendment with treated and untreated olive mill wastewater Ali Mekki, Abdelhafidh Dhouib, Sami SayadiÃ
Laboratoire des Bioprocedes,Centre de Biotechnologie de Sfax, BP: ‘‘K’’ 3038 Sfax, Tunisie ´ ´ Received 8 June 2005; accepted 15 June 2005

KEYWORDS Microbial community; Olive mill wastewater; Polyphenols; Soil respiration

Summary
We investigated the effect of untreated and biologically treated olive mill wastewater (OMW) spreading on the soil characteristics and the microbial communities. The water holding capacity, the salinity and the content of total organic carbon, humus, total nitrogen, phosphate and potassium increased when the spread amounts of the treated or untreated OMW increased. The OMW treated soil exhibited significantly higher respiration compared to the control soil. However, the C-CO2/Ctot ratio decreased from 1.7 in the control soil to 0.5 in the soil amended with 100 m3 haÀ1 of untreated OMW. However, it slightly decreased to 1.15 in the soil amended with 400 m3 haÀ1 of treated OMW. The treated OMW increased the total mesophylic number while the number of fungi and nitrifiers decreased. Actinomycetes and spore-forming bacteria were neither sensitive to treated nor to untreated OMW. The total coliforms increased with higher doses of treated and untreated OMW. A toxic effect of the untreated OMW appeared from 100 m3 haÀ1. This toxicity was more significant with 200 m3 haÀ1, where microflora of total mesophilic, yeasts and moulds, actinomycetes, and nitrifiers were seriously inhibited except for total coliforms and spore-forming bacteria. & 2005 Elsevier GmbH. All rights reserved.

Introduction
The olive mill wastewater (OMW) is a critical problem, especially in the Mediterranean area, where the olive cultivation is widespread and huge amounts of this effluent 30 millions m3 yÀ1 worldÃCorresponding author. Tel./fax: +216 74 440 452.

wide and 500 000 m3 yÀ1 in Tunisia alone, are annually produced (Sayadi and Ellouz, 1995; Casa et al., 2003). This waste contains an enormous supply of organic matter, COD between 40 and 210 g dmÀ3 and BOD5 between 10 and 150 g dmÀ3 (Feria, 2000). Some characteristics of this material

E-mail address: sami.sayadi@cbs.rnrt.tn (S. Sayadi). 0944-5013/$ - see front matter & 2005 Elsevier GmbH. All rights reserved. doi:10.1016/j.micres.2005.06.001

ARTICLE IN PRESS
94 are favourable for agriculture since this effluent is rich in organic matter, nitrogen (N), phosphorous (P), potassium (K) and magnesium (Mg). The organic fraction of this wastewater includes sugars, tannins, poly phenols, poly alcohols, pectins, lipids, and proteins (Mulinacci et al., 2001; LesageMeessen et al., 2001). For these reasons, increasing attention has been given to find the best methods to spread OMW on agricultural lands and to recycle both the organic matter and the nutritive elements in the soil crop system. Moreover, agricultural irrigation with wastewater effluents became a common practice in arid and semiarid regions, where it was used as a readily available and inexpensive option to fresh water (Angelakis et al., 1999; Oved et al., 2001). Fresh OMW was used as a fertilizer in the horticulture and in the olive cultivation (Cox et al., 1997; Ben Rouina et al., 1999; Ammar and Ben Rouina, 1999; Cereti et al., 2004). However, biodegradation of this waste in the nature is difficult because it contains a strong antibacterial effect exerted, by various phenolic compounds (Yesilada et al., 1999; Sayadi et al., 2000; Rinaldi et al., 2003). Before its utilization in the irrigation, OMW was treated by several processes such as aerobic treatment, anaerobic digestion and composting process (Sayadi and Ellouz, 1992, 1995; Ehaliotis et al., 1999; Paredes et al., 2000; Kissi et al., 2001; Marques, 2001; Casa et al., 2003; D’Annibale et al., 2004). Some Mediterranean...
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