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The agricultural spreading of dehydrated sewage sludge from urban sewage treatment plants is economically profitable provided that the soil agronomic quality and the absence of contamination, in particular of heavy metals, are maintained. We evaluated the variability of sludge between five treatment plants in northern Algeria. We determined parameters that account for their agronomic quality and total content of Ag, Cd, Co, Cr, Cu, Ni, Pb, Ti and Zn. The speciation of metals, which determines their bioavailability, was characterized by sequential extraction into five fractions: easily exchangeable, acid-soluble, bound to carbonates and Fe-sulphides, bound to Fe–Mn oxides, bound to organic matter or sulphides, residual. All the sludges analysed showed satisfactory properties for plant growth. High total Ni contents for three of the sludges indicated that they were not landfillable under French or Chinese regulations. Ni, however, was contained in poorly bioavailable fractions and therefore presented a low risk to soils. In contrast, the total Cu was lower than the regulatory limit values, but mainly contained in very bioavailable fractions whose accumulation over time could reach toxic levels for plants over a period of 3 to 11 years depending on the sludges. These results showed that regulations are not adapted and must take into account the bioavailability with regard to the characteristics of the soils on which to spread. The speciation of metals in the sludge has also, on the one hand, made it possible to identify the zone of the sewerage network in which the sources of contamination must be sought and, on the other hand, has given indications on the possible nature of these sources. [ABSTRACT FROM AUTHOR]

The increase of drug-resistant pathogens occurring due to indiscriminate use of antibiotics and their rejection in nature are becoming a serious problem. This situation has motivated researchers across the globe to search for suitable alternatives in natural compounds. Moringa oleifera has been the object of several researches due to its multiple uses, as its seeds are known to possess antibacterial and antifungal properties. In the present study, pathogenic bacteria were isolated from wastewaters of Oued Bechar; the in vitro antibacterial activity of aqueous seeds extract against 30 strains, and the phytochemical screening of this plant were investigated. The results of isolated strains revealed the existence of various pathogenic bacteria dominated by: Escherichia coli, Salmonella spp, Klebsiella spp, Enterobacter spp; Streptococcus D, Pseudomonas spp, Vibrio spp. the inhibition diameters of aqueous seeds extract with and without oil removal ranged from 7mm to 21mm, and 8mm to 27mm respectively, with a significant antibacterial effect was observed against 3 of 4 Streptococci D around 1g/ml disc. Additionally, the phyto-chemical screening results showed that seeds of M. oleifera are rich in phyto-molecules such as terpenoids and tannins which are characterized by antifungal and antibacterial activity. The results of this study suggest that M. oleifera seeds from South-Western Algeria can be a source of natural antibacterial agent. [ABSTRACT FROM AUTHOR]