COD and TPH analysis in slops experimental treatment plants: analytical problems.

Abstract

COD AND TPH ANALYSIS IN SLOPS EXPERIMENTAL TREATMENT PLANTS: ANALYTICAL PROBLEMS. In the last years, the persistence and accumulation of xenobiotic compounds in the environment created many disposal problems of oily wastewater generated by ships, mainly in engine-rooms (bilge waters) and by cleaning of tanker (slops). The high salinity levels (up to 25.000 mgL-1) and the pollutants concentration, both limit the chances of discharge into the sewer systems and address the disposal of these wastewaters to the sea. For these reasons it is necessary to treat such wastewater efficiently before discharging [1]. As a part of a broader project concerning slops treatments, this work addresses issues related to the analytical methods of the COD and TPH parameters, chosen under the provisions of Italian Legislative Decree 152/06, that implements the European directives on environmental protection. In the COD analysis the greatest difficulty was the high salinity levels corresponding to high chlorides levels. Chlorides cause a positive interference in the measurement, and this interference during the analysis of COD was investigated at various concentrations of mercury in order to try to minimize the use of this reagent that causes many problems of safety and disposal, and at different times reaction [2][3][4]. The major problems in TPH analysis concerned correct setup of the gas chromatographic separation, high variability in sample composition and the high capacity of the sample to form emulsions during the liquid-liquid extraction procedure. This paper reports the results of the analysis of COD and TPH and the problems related to the development of a suitable analytical method for the analysis of these specimens. This study is part of STITAM European project, created with the aim to develop innovative technologies for the treatment of liquid wastes of navigation, in order to better safeguard marine environment. [1] G. Mancini, S. Cappello, M.M. Yakimov, A. Polizzi, M. Torregrossa, Chemical Engineering Transactions 27 (2012) 37-42. [2] I. Vyrides, D.C. Stuckey, Bioresource Technology 100 (2009) 979–982 [3] Alexandra M.E. Viana da Silva, Ricardo J.N. Bettencourt da Silva , M. Filomena G.F.C. Camoes, Analytica Chimica Acta 699 (2011) 161– 169 [4] D.D.C. Freire, G.L. Sant’anna jr, Environmental Technology 19 (1998) 1243- 1247