Characterization of E1 Kraft Mill Effluent by Toxicity Identification Evaluation Methodology

Abstract

In order to recover and reuse water in the Kraft mill process, evaluation of separate streams is required to identify toxic compounds or microcontaminants. The stage E1 Kraft effluent, corresponding to the first extraction step of the bleaching Kraft mill process, provides the main toxic compounds found in the final process effluent. This paper uses the toxicity identification evaluation (TIE) procedure for the physicochemical and ecotoxicological characterization of the E1 Kraft effluent. To distinguish the most important toxic compounds, a physicochemical characterization and Phase I of the TIE procedure were performed. The acute toxic effect of the E1 Kraft effluent and treated fraction was performed on Daphnia magna. Results show that untreated E1 Kraft effluent exerts an acute toxic effect on D. magna (24 h LC50 = 27.6%), where the E1 Kraft effluent is characterized by pH 10.5, chemical organic demand (COD) 1,348.8 mg/l, and biological organic demand (BOD5) 397.5 mg/l, while total phenolic compounds and color are 853.7 mg/l and 0.204 1 × 1 cm, respectively. Additionally, Cu+2 (0.51 mg/l) and Fe+2 (0.64 mg/l) were detected. With respect to different treatments, our results indicate that activated carbon, anionic and cationic exchange treatments were able to reduce more that 45% of E1 Kraft effluent’s acute toxicity and that the ethylenediaminetetraacetic acid treatment was able to reduce the E1 Kraft effluent’s acute toxicity to around 75% and the Cu+2 concentration to 0.019 mg/l. Moreover, specific analysis of heavy metals and organic compounds by GC-MS show that the main compound responsible for the toxicity was Cu+2, whose tolerance level on D. magna of the 0.12 mg/l.