Use of ethylenediaminetetraacetic acid in pulp mills and effects on metal mobility and primary production

Abstract

Over the last decade, the use of ethylenediaminetetraacetic acid (EDTA) has increased by a factor of three within the Swedish pulp industry. The effects of pulp mill wastewater in combination with EDTA on metal mobility and the consequences for ecologically relevant organisms have been studied. Ethylenediaminetetraacetic acid was added to pulp mill effluent water in the laboratory and compared to wastewater without EDTA. Degradation of the water was followed over a experimental period up to eight weeks and samples were taken five times for chemical analysis and at the beginning and the end for biological tests. Half a year later, the experiment was repeated. The results from both experiments showed that EDTA markedly increased the solubility of zinc, cadmium, lead, iron, nickel, and copper, whereas the solubility of vanadium, molybdenum, thallium, arsenic, and chromium was not changed by the presence of EDTA. No measurable degradation of EDTA occurred even after 5.5 months. The toxicity of the pulp mill effluent water was low, and only a slight toxic effect was observed on the reproduction of Ceramium strictum. The most pronounced effect was a stimulation in the growth of three algal species in 5 to 20% (v/v) total effluent wastewater with and without EDTA. The presence of EDTA in the dissolved fraction of the pulp mill effluent water increased the growth stimulation in 20 to 40% (v/v), possibly because of the increased availability of essential metals like iron, zinc, and copper. The capacity of the pulp mill wastewater to support algal growth was nearly as good as a rich nutrient medium for algae. The combination of poorly degradable EDTA and the increasing availability of metals might further enhance eutrophication in the recipient areas of pulp mills.

LOCAL ADAPTATION OF CERAMIUM TENUICORNE (CERAMIALES, RHODOPHYTA) WITHIN THE BALTIC SEA1

“…The results of experiment 4 also indicate that growth of Ceramium from the Bothnian Sea may be regulated by deficiency of certain ions, rather than by osmotic stress in ambient water (Kirst 1990). To some extent, the observed outcome may reflect treatment effects, as the treatments media of very low salinity were not natural waters, but were prepared from dilution of brackish sea water with distilled water of a different ionic composition, or the added EDTA or some other component in the trace element solution may have stimulated growth directly (Eklund et al 2002). However, none of this alternatives would explain the observed differences in responses among isolates.…”

An in situ bioassay for freshwater environments with the microalga Pseudokirchneriella subcapitata

“…The laboratory assay was performed using simultaneously plain site waters and site waters enriched with the same nutrients comprising the MBL. Because growth differences when performing a microalgal assay on natural water samples may be due to toxicity, nutrient shortage, or both, it is a recommended approach for laboratory algal assays evaluating the hazard of natural samples (e.g., effluents) to add nutrients to the test waters (Environment Canada, 1992;USEPA, 1994;Eklund et al, 2002). In this way, nutrient differences among waters are eliminated and it is possible to distinguish a toxic effect from that caused by poor nutrient levels.…”

A screening method for toxicity identification evaluation on an industrial effluent using Chelex®-100 resin and chelators for specific metals

“…Liu et al [23] reported 5 to 10 mg/L of Ni in a deplating wastewater. In the pulp and paper industries, Ni concentrations of 0.030 mg/L were detected in the present study (Table 2), and a concentration of 0.001 mg/L was found in a Swedish pulp and paper mill effluent [24]. Thus, compared with other industries, the amount of Ni discharged from pulp and paper mills is relatively low.…”