The Impact of the Oxidising Agent Type and Coagulant Type on the Effectiveness of Coagulation in the Removal of Pollutants From Underground Water With an Increased Content of Organic Substances

Abstract

To cite this article: Izabela Krupińska (2016) The impact of the oxidising agent type and coagulant type on the effectiveness of coagulation in the removal of pollutants from underground water with an increased content of organic substances, Journal of Environmental Engineering and Landscape Management, 24:1, 70-78, Abstract. Trinitrotoluene (TNT), a commonly used explosive for military and industrial applications, can cause serious environmental pollution. 28-day laboratory pot experiment was carried out applying bioaugmentation using laboratory selected bacterial strains as inoculum, biostimulation with molasses and cabbage leaf extract, and phytoremediation using rye and blue fenugreek to study the effect of these treatments on TNT removal and changes in soil microbial community responsible for contaminant degradation. Chemical analyses revealed significant decreases in TNT concentrations, including reduction of some of the TNT to its amino derivates during the 28-day tests. The combination of bioaugmentation-biostimulation approach coupled with rye cultivation had the most profound effect on TNT degradation. Although plants enhanced the total microbial community abundance, blue fenugreek cultivation did not significantly affect the TNT degradation rate. The results from molecular analyses suggested the survival and elevation of the introduced bacterial strains throughout the experiment. Reference to this paper should be made as follows: Nõ lvak, H.; Truu, J.; Limane, B.; Truu, M.; Cepurnieks, G.; Bartkevičs, V.; Juhanson, J.; Muter, O. 2013. Microbial community changes in TNT spiked soil bioremediation trial using biostimulation, phytoremediation and bioaugmentation, Journal of Environmental Engineering and Landscape Management 21(3): 153Á162. http://dx. abstract.The article presents the results of studies concerning the impact of the method of Fe(II) ion oxidisation on the effectiveness of coagulation in the removal of pollutants from underground water with an increased content of organic substances (TOC up to 5.338mgC/dm 3 ). In order to oxidise the Fe (II) ions before the coagulation process, the underground water was subjected to aeration, or either potassium manganate (VII) or hydrogen peroxide were dosed in the stoichiometric amount in view of the concentration of Fe (II). The efficiencies of three coagulants were compared: that of aluminium sulphate (VI), polyaluminium chloride (PAX XL-60) and iron (III) sulphate (VI) -PIX-112. Coagulant doses expressed in mgAl/dm 3 or mgFe/dm 3 and changed within the range of 1 to 6 mgAl(Fe)/dm 3 . Volume coagulation was performed in 1-dm 3 groundwater samples using 1-minute rapid mix (250 rpm) and 25-minute slow mix (30 rpm) followed by 2-hour sedimentation. It has been proven that the type of oxidising agent and coagulant, as well as their dose, co-determines the effectiveness of the removal of the pollutants. Among the used methods of iron (II) oxidisation, the best effects have been achieved by potassium manganate (VII) with regards to the effects of the reduction...

The Influence of Aeration and Type of Coagulant on Effectiveness in Removing Pollutants from Groundwater in the Process of Coagulation

“…Because of this, a technological system for purifying this kind of groundwater should include a method for the efficient removal of iron occurring together with organic compounds. This condition is probably satisfied by the right process of coagulation 2,4,5 . Iron and aluminium salts are especially effective coagulants.…”

“…In the case of water with an increased content of organic substances, iron compounds, and increased turbidity and colour intensity, the application of conventional groundwater treatment does not ensure the required treatment efficiency [1][2][3][4][5][6] . Organic compounds delay, and sometimes even render the oxidation of iron(II) ions impossible.…”

“…It has also been shown that the stability of iron-organic compounds increases when the concentration of organic ligands increases, and in order to remove them, coagulation is necessary, most preferably with aluminium coagulants 9,10 . Regardless of the kind of coagulant used, before the process of coagulation, it is necessary to oxidise Fe(II) ions occurring in non-organic compounds, after which the process of sedimentation is not necessary 2,4,5 . Some authors 11 recommend the use of chemical oxidants for oxidizing Fe(II), dosed in quantities greater than stoichiometric quantities, which enable a high value of oxidization-reduction potential to be obtained.…”

“…Iron and aluminium salts are especially effective coagulants. Many researchers have reported 1,4,5 that iron coagulants are more effective in respect to manganese removal than aluminium coagulants. Laboratory tests conducted by Albrektiene et al 2 revealed that the coagulation process markedly increased efficacy in iron-organic complexes removal.…”

“…25. It has been found that the importance of the pH value is greater in the case of removing pollution that determines the colour and the level of organic pollution than in the case of pollution that determines turbidity 4,5 . In the case of non-prehydrolysed coagulants (e.g.…”