Survey of receiving‐water environmental impacts associated with discharges from pulp mills: 1. Mill characteristics, receiving‐water chemical profiles and lab toxicity tests

Abstract This survey examined the relationship between environmental responses at pulp mill sites and the pulping process (kraft vs. sulphite/thermomechanical pulping), effluent treatment (primary vs. secondary treatment), and bleaching technology used by pulp mills. This manuscript is the first in a series of four; it reviews the location and operating characteristics of mills included in the survey and provides background information on water chemistry that is relevant to the other components of the survey. In addition, lab 7-d toxicity tests of receiving water were conducted using fathead minnows (Pimephales prome-las) and the cladoceran Cenodaphma dubia with water samples collected upstream (reference) and downstream (plume) of effluent discharges at 11 Canadian pulp and paper mills; these samples were collected at the same time as fish surveys were conducted. Survival of fathead minnow larvae was significantly reduced at four of the 11 downstream sites. Ceriodaphnia reproduction was significantly higher at six of the 11 downstream sites and significantly lower at two downstream sites. There were no significant effects on fathead minnow larva growth or adult Cenodaphma survival at any of the examined downstream sites. Negative effects in the toxicity tests were generally associated with the low dilution discharge of primary treated effluent with a previous history of acute toxicity. Fathead minnow and Cenodaphnia tests were generally correlated with historical data on benthic mac-roinvertebrate community responses. Neither toxicity test predicted the physiological changes in wild fish that are presented in accompanying papers.