No abstract

No 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.

289Efecto del tratamiento de oscuridad y salinidad en el rendimiento y calidad del agar de Gracilaria cornea (Rhodophyceae)Effect of dark and salinity treatment in the yield and quality of agar from Gracilaria cornea (Rhodophyceae) Yolanda ResumenEl tratamiento alcalino previo a la extracción del agar del género Gracilaria reduce, entre otras reacciones, el contenido de sulfatos y aumenta la fuerza de gel; sin embargo, a nivel industrial, requiere de costosos procesos de purificación de los efluentes para reducir los niveles de contaminación. El alga roja Gracilaria cornea fue cultivada bajo diferentes tratamientos de oscuridad y salinidad antes de su cosecha con el propósito de remplazar dicho tratamiento alcalino. Los diferentes tratamientos realizados fueron: (a) oscuridad y 33‰ de salinidad durante 8 días, Todos los tratamientos redujeron el contenido de sulfatos en el agar en aproximadamente un 24% cuando se les compara con el agar obtenido sin ningún tratamiento. Para G. cornea el tratamiento [4+4] puede en el futuro llegar a ser un método adicional a un tratamiento alcalino ligero en el que se utilice una menor concentración de álcali durante la extracción de agar.Palabras clave: Agar, Gracilaria cornea, salinidad, tratamiento de oscuridad. AbstractThe alkali treatment used previous to agar extractions from the Gracilaria genus reduces, among other reactions, the sulphate content and improves the gel strength; however, at an industrial level it requires expensive effluent processing to reduce its polluting charge. The red alga Gracilaria cornea was cultivated under dark and salinity treatments to replace this alkali treatment. The different treatments tested were: (a) darkness and 33‰ salinity for 8 days, [dark treatment]; (b) darkness and 50‰ salinity for 4 days, followed by darkness and 25‰ salinity for 4 days, [4+4]; and (c) darkness and 50‰ salinity for 8 days, followed by darkness and 25‰ salinity for 4 days, [8+4]. The treatment [4+4] increased the agar yield in 26% (from 36.6 to 46.1%). All treatments reduced the sulphate content of the agar in approximately 24% when compared with agar obtained without any treatment. For G. cornea the [4+4] treatment might become in the future an additional treatment to a mild alkali treatment using less alkaline reagents for agar extraction.