Ecotoxicity assessment of the industrial effluent from the Valdivia cellulose pulp mill and of its discharge receptor body (rio Cruces)

摘要

This research analyzes the ecotoxicological characteristic of the liquid discharges of one of the last pulp mill built in Chile: Planta Celulosa Valdivia. Its effluent falls into the Cruces River which in turn empties at the Carlos Anwandter Nature Sanctuary. During the year 2006 effluent and river water was evaluated for acute and chronic toxicity with six freshwater species: Hyalella gracilicornis (anphipod), Daphnia obtusa (water flea), Oncorhynchus mykiss (rainbow trout), Gambusia affinis (mosquito fish), Selenastrum capricornutum (microalgae) and Lemna valdiviana (duckweed). Acute toxicity bioassays of effluents from processing pine or eucalyptus did not find lethal effects in any of exposed species. Chronic toxicity testing of the effluent did not show significant effects either. Only with D. obtusa certain level of chronic toxicity became evident after exposure of 21 days, with a fecundity reduction of 18 % (pine-effluent) and 32 % (eucalyptus-effluent) compared to control medium. The results of the toxicity assessment to the river water revealed absence of lethal toxicity at the pre and post impact sites of the effluent discharge. No negative effect on growth or reproduction of the tested species was registered, except with D. obtusa. This species revealed significant differences in reproductive output in relation to the control when exposed to pre-impact water. This implies that contaminants up the river might have been polluting the water or, otherwise, natural variations in water quality might have affected Daphnia's fecundity at that time. Modern pulp production combined with appropriate waste treatment has improved considerably the environmental impact of chemical wood pulping.