Quantification of resin acids, fatty acids and sterols in process and waste water from forest industry

Abstract: This work focuses on wood extractives in effluents from the CTMP plant at Skoghall Mill. Pulp and paper industry effluents contain mostly natural compounds which are part of the trees. They are toxic to aquatic life but harmless in nature, as they are present in low concentrations. Processing tons of wood, such as in a pulp mill, strongly increases the concentrations of the toxic compounds (Ali, M. and Sreekrishnan, T., 2001) which have to be treated before transferring to the aquatic environment.Extractives can be found in different forms, as micelles soluble in water, unprocessed in fibers or absorbed on the surface of fibers. It is important to know in which forms extractives are mostly present in the effluent, so that they can be treated more efficiently. It is desired to have extractives absorbed on the fibers and fibrils present in the waste water, so they can be separated from the water and treated separately, e.g. burned for energy recovery. Dissolved extractives complicate the oxygen transfer in an aerated biological treatment step with their surface active properties (Sandberg, 2012).The aim of this study is quantification of extractives on the fibers suspended in the waste water and extractives dissolved in the water. The distribution between the two forms is an important input when designing future effluent treatment. Wood extractives itself are a wide group with different compounds. This work focuses on the main groups present in waste water: resin acids, free and esterified fatty acids and, free and esterified sterols. These groups are analyzed in different process waters and waste water before the waste water treatment plant. The measured concentrations of extractives were as expected, higher in process and effluent waters, lower in white water. Most of the extract was dissolved in the water and unfortunately fiber samples contained very low concentration from the total extract in the samples.