Determinación de la capacidad nitrificante de un sedimento marino proveniente de un centro de cultivo de salmones / Determination of the nitrifying capacity of marine sediments from a salmon farming centre

En el proceso productivo del salmón se eliminan residuos líquidos y sólidos. Si estos residuos no son tratados o retirados de los sitios de cultivos pueden ser tóxicos a los sistemas acuáticos, debido a su descomposición y producción de amonio (NH4+) y nitrito (NO2 4 +). En los ecosistemas acuáticos las bacterias nitrificantes son responsables de la oxidación de estos compuestos. El objetivo del presente trabajo es obtener cultivos de bacterias amonio oxidantes (BAO) y nitrito oxidantes (BNO) en sistemas de tipo batch y evaluar la capacidad de eliminación de nitrógeno, determinando las respectivas cinéticas. Como inóculo inicial se utilizó sedimentos de un centro de cultivo de salmones. Los resultados muestran la baja actividad nitrificante presente en los sedimentos, obteniéndose para BAO producciones de 197-206mg·l -1 N-NO -2, velocidades de consumo de O2 (VCO) con respecto del factor estequiométrico de 0,023mg·l -1·min-1 N y consumo neto de O2 (CNO) de 0,055mg·l-1·min-1 O2, mientras que para BNO, se obtuvieron producciones de 404-631mg·l-1 N-NO3-, VCO de 0,027mg·l-1·min-1 N y CNO de 0,0122mg·l?1·min?1 O2. Los resultados corroboran la incapacidad de las bacterias nitrificantes de oxidar la gran cantidad de compuestos nitrogenados generados por esta actividad acuícola.

Anaerobic biodegradation of sterols contained in kraft mill effluents.

Bleached kraft mill requires large quantities of water and chemicals reactives and generates effluents containing active organic compounds. Specifically, hormonal changes in fish and their communities have been demonstrated, which could be attributed to endocrine-disrupting chemicals (EDCs) contained in kraft mill effluents. This chronic toxicity is attributable to extractive compounds, such as resin acids, sterols, and fatty acids. The goal of this work is to evaluate the methanogenic toxicity and anaerobic biodegradation of stigmasterol and beta-sitosterol. A continuously anaerobic filter (AF) was used for the anaerobic biodegradation of stigmasterol and beta-sitosterol. Three phases were evaluated. In phase I, an elementary chlorine-free bleached kraft mill effluent was fed to the reactor whereas in phases II and III, the effluent was supplemented with increasing stigmasterol and beta-sitosterol concentrations. The AF displays high performance in biological oxygen demand (BOD5) removal (up to 94%); however, only 50% of the chemical oxygen demand (COD) was removed. Simultaneously, the AF system shows a great ability to remove beta-sitosterols (77-100%) and stigmasterols (87-95%). No negative effect on the methanogenic activity inhibition was shown by beta-sitoesterols and stigmasterol. However, a mixture of beta-sitosterols and stigmasterols (ratio 1:1) caused a less than 10% reduction in methanogenic activity.

Resistance of diethylenetriaminepentaacetic acid to anaerobic biodegradation

Kraft mills are responsible for the massive discharge of highly polluted effluents, and new bleaching processes (i.e. Total Chlorine Free (TCF)) is presented as a feasible option to reduce this environmental impact. However, increased TCF pulp production is accompanied by an increase in chelate use. The most commonly used chelates, ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DPTA), are considered to be relatively persistent substances in water treatment plants, and consequently environmentally critical compounds. The purpose of this work is to investigate DPTA behaviour in an anaerobic system. An Anaerobic Filter (AF) was operated with three different DPTA load rates (LRDPTA = 0.07 - 0.28 gDPTA/L×d), and the operating strategy was to maintain the anaerobic system stable during the entire operation (alkalinity ratio below 0.3). The AF's maximum Chemical Oxygen Demand (COD) removal was 59 percent, whereas the Biological Oxygen Demand (BOD5) was around 95 percent. However, only 5 percent of DPTA removal was observed under anaerobic conditions during the first operating period. Scanning electronic microscopy indicates that the operating system reduced microorganism biodiversity.