Oil pollutants in alluvial sediments: Influence of the intensity of contact with ground waters on the effect of microorganisms

The influence of the intensity of interaction between oil pollutants and ground waters in alluvial sediments on the effect of microbial activity was investigated in this work. The study was based on a comparison of detailed analyses of two fractions of an oil pollutant originating from a Danube alluvial formation near the Pancevo Oil Refinery: fraction 1, separated from the aqueous layer by decantation, presumed to have been in less intensive interaction with water, and fraction 2, isolated from the aqueous emulsion by extraction with chloroform, presumed to have been in stronger interaction with water. Both fractions were shown to originate from the same type of oil pollutant. Nevertheless, significant compositional differences between the two fractions were observed. Asignificantly pronounced domination of even carbon number homologues of C18?C24 n-alkanes in fraction 2, atypical for crude oil pollutants, compared to the corresponding distribution observed in fraction 1, suggested a more intense activity, i.e., a much better effect of microorganisms in direct contact with the oil pollutant within the aqueous environment. The identification of even carbon number C14?C18 n-alcohols and C14?C18 fatty acids, as well as cholesterol, in fraction 2, suggested that microorganisms of the algal type in non-photosynthetic conditions were most probably responsible for the mentioned microbial processes.

Preliminary evaluation of the performance of new pre-polymerised inorganic coagulants for lowland surface water treatment

This paper is concerned with the performance of relatively new kinds of pre-polymerised inorganic coagulants, poly-alumino-iron-sulphate (PAFS) and polyferric sulphate (PFS). Laboratory experiments were undertaken to evaluate the PAFS and PFS, in comparison with conventional coagulants such as ferric sulphate (FS) and aluminium sulphate (AS), for the coagulation of algal-type model waters and a lowland surface water containing algae and natural organic matter (NOM). Experimental results demonstrated that under the conditions studied, the performance of pre-polymerised coagulants were consistently superior to conventional coagulants (i.e., FS and AS). This is attributed to the presence of a range of pre-formed polymerised species. The coagulation mechanism of PAFS and PFS has been discussed in the paper.