Acute ecotoxicity on Daphnia magna to evaluate effluent samples of Kraft pulp mill treated by UV/H2O2 process

Abstract

The pulp and paper industry is one of world’s largest water consumers, generating high volumes of effluents. The Kraft process produces effluents with high BOD, COD, suspended solids, lignin and a myriad of potentially toxic compounds, which require treatment before discharge into the aquatic environment. Advanced oxidation processes, such as UV/H2O2, have been applied as treatment alternatives because they can destroy many compounds before they mineralize. However, when the oxidation process is incomplete, occurs could be produced by products with high toxicity. This study evaluated the acute toxicity on Daphnia magna of two effluent samples of Kraft pulp mill (KE1 and KE2) treated by UV/H2O2 process. The effects of the pH variation and oxidant concentration on the removal of DOC, total UV-vis spectral area and apparent color were considered to adjust the experiments’ conditions with diluted effluent KE1. Both samples were treated at pH 4.0 and 70 mg L-1 of H2O2 for 40 min, achieving removals of up to 69.4% in apparent color, 73.7% of phenolic compounds and 68.9% of lignin compounds. When the reaction was applied in undiluted effluent samples, the acute toxicity for Daphnia magna decreased for KE1 after 780 min of treatment, whereas KE2 became four times more toxic. The data showed that although the treatment had been efficient considering physics and chemicals parameters, it is necessary follow the oxidative processes with ecotoxicological bioassays to guarantee their safety, since different effluents of the Kraft pulp mill could present different levels of organic compound mineralization.

Characteristics and treatment of Brazilian pulp and paper mill effluents: a review

“…Some studies collected and characterized more than one effluent sample and from different days in the same mill. Considerable differences were observed for some characteristics, mainly BOD 5 (Amaral et al, 2013 ; Castro et al, 2019 ; Chaparro & Pires, 2011 ; Micheletto et al, 2019 ).…”

“…Considerable differences were observed for some characteristics, mainly BOD 5 (Amaral et al, 2013 ; Castro et al, 2019 ; Chaparro & Pires, 2011 ; Micheletto et al, 2019 ).…”

“…This mixture of effluents also showed cytotoxic, genotoxic, and mutagenic effects on Allium cepa L. (Chaparro & Pires, 2011 ). For Daphnia magna , a kraft process effluent showed acute toxicity (Micheletto et al, 2019 ). On the other hand, the effluent evaluated by Giroletti ( 2017 ) was not toxic for lettuce seeds ( Lactuca sativa ).…”