Influence of Secondarily Treated Kraft Mill Effluent on the Accumulation Rate of Attached Algae in Experimental Continuous-Flow Troughs

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Abstract
In three seasonal experiments in 1977, increases in the rate of attached algal accumulation were normally found with each additional increment of secondarily treated kraft mill effluent (KME). The effect of KME on the instantaneous accumulation coefficients of algae were 1.2–2.8 times greater in the summer than in the autumn or spring at all dilutions tested. At higher concentrations (5 and 25% v/v KME) an inhibition of accumulation was usually observed during the first 5–6 d of exposure; after this period diatom biomass increased sharply. Succession of diatom taxa to different forms, rather than physiological adaptation by usually predominant species occurred. No inhibition was noted at lower concentrations (0.5, 1, and 2% v/v) of KME. Relatively high levels (20–30 μg∙L−1) of soluble reactive phosphorus (SRP) and low concentrations of nitrate + nitrite–nitrogen (5–10 μg∙L−1) and ammonia–nitrogen (2–20 μg∙L−1) in the river dilution water suggested that nitrogen was the primary limiting nutrient. Ammonium uptake tests for nitrogen deficiency confirmed nitrogen limitation in algae grown in unenriched river water compared to algae exposed to KME for 6 d. Differences in chlorophyll a: ATP ratios among periphyton communities of the different treatments were minimal after 9 d.Key words: kraft mill effluent, algal growth, nutrient enrichment, benthic algae, river, chlorophyll a

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