Evaluation of triclosan toxic effects on the methanogenic activity

BACKGROUND: Triclosan (TCS) is an antimicrobial agent widely used in health care and consumer products. This compound is present in sludge of wastewater treatment plants (WWTPs), and because of its bactericidal characteristics, it can inhibit the methanogenic activity in anaerobic digestion (AD) technology. The aim of this study was to evaluate the toxic effects of TCS on the methanogenic activity. RESULTS: Batch anaerobic reactors were used with TCS concentrations of 7.8, 15.7, 23.5, and 31.4 mg/L. These assays consisted in three successive feedings (I, II, and III), wherein the sludge was exposed to each TCS concentration and volatile fatty acid (VFA) substrate. For evaluation of the residual sludge activity during feeding III, only VFA was used. The results showed that the increase in TCS concentrations correlated with the reduction in methane (CH4) production. In this case, the minimum values were achieved for TCS concentration of 31.4 mg/L with CH4 levels between 101.9 and 245.3 during feedings I, II, and III. Regarding the effect of TCS on VFA consumption, an inhibitory effect was detected for TCS concentrations of 23.5 and 31.4 mg/L, with concentrations of acetic, butyric, and propionic acids at the end of the assay (37 d) between 153.6 and 206.8, 62.5 and 60.1, and 93.4 and 110 mg/L, respectively. Regarding the removal of TCS during AD, these values were above 47%. Conclusion: TCS is an inhibitor of methanogenic activity with a decrease between 63 and 70% during the different feedings. The CH4 production was not recovered during feeding III, with inhibition percentages of 21­72%.

Methanogenic toxicity evaluation of chlortetracycline hydrochloride

Background Anaerobic digestion is a technology applied successfully to converting organic matter into biogas. However, the presence of inhibitory compounds such as antibiotics can adversely affect methane production. The aim of this study is to evaluate the toxic effect of chlortetracycline hydrochloride (CLOR) on the methanogenic bacteria. In order to study the methanogenic toxicity of CLOR, different concentrations of CLOR (10, 50, 100, 200 mg L- 1) were evaluated by methanogenic toxicity assays using three feedings. Results Maximum methane production was obtained for the assays with 10 mg CLOR L- 1, the values obtained were 277 ± 4.07; 193 ± 11.31 and 166 ± 7.07 mL for the first, second and third feedings, respectively. The average values for acetic, propionic and butyric acid at start of the experiments were 2104 ± 139; 632 ± 7.6; 544 ± 26 mg L- 1, respectively. The VFA values obtained finally of the experiment were dependent on the evaluated antibiotic concentrations, indicating that the efficiency of methanogenesis is directly affected by the CLOR concentration. Conclusions CLOR is an effective methanogenic bacteria inhibitor. Moreover, the results show that CLOR has a bactericidal effect on methanogenic activity given that methane production did not recover during the third feeding. This study shows that the 50% inhibitory concentration (IC50) for methanogenic bacteria in 10 mg L- 1.

Effect of free ammonia nitrogen on the methanogenic activity of swine wastewater

Swine wastewater is characterized by high organic matter content, solids, nitrogen (expressed as total ammonia and protein) and heavy metals. This work determines the methanogenic toxicity effect of free ammonia contained in swine wastewater comparing raw swine wastewater (RW) and the liquid fraction of swine wastewater (TW). The values of IC50 (50 percent of inhibition) obtained for methanogenic bacteria ranged between 56 and 84 percent for RW, meanwhile IC50 for TW was ranged between 84 and 94 percent. Such inhibitory effects can be related to the free ammonia nitrogen concentration (> 40 mg NH3-N/L) contained in swine wastewater.

Aerobic removal of stigmasterol contained in kraft mill effluents

Kraft mill effluent, due to its organic matter content and acute toxicity, must be treated. A primary treatment followed by a secondary treatment is the most common system. Aerated lagoon is also considered an effective biological treatment, although this technology has some drawbacks related with operation parameters and land extension space. Moreover, the recovery efficiency for micropollutants contained in kraft mill effluent is questioned due to the anoxic zone in the system. The goal of this work is to evaluate the performance of the aerated lagoon to remove stigmasterol contained in kraft mill effluents. Kraft mill effluent was treated by an aerated lagoon (AL), which was operated with three different stigmasterol load rates (SLR = 0.2, 0.6 and 1.1 mg/L x d) and a hydraulic retention time of 1 day. The AL’s maximum Chemical Oxygen Demand (COD) removal was 65 percent, whereas the Biological Oxygen Demand (BOD5) was around 95 percent. The removal efficiency of stigmasterol removal was 96 percent when SLR 1.1 mg/L x d, although an accumulation of stigmasterol was detected for lower SLR.

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.

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.

Fed-batch decolorization of Poly R-478 by Trametes versicolor

Efluentes industriais altamente coloridos são difíceis de degradar utilizando as tecnologias fisico-químicas e bacterianas existentes atualmente. O sistema enzimático extracelular secretado pelo fungo de podridão branca apresenta um grande potencial oxidativo, capaz de dar início a decomposição das estruturas residuais dos compostos responsáveis pela cor destes efluentes. Aspectos fisiológicos foram avaliados para optimizar as condições de descoloramento de um corante sintético, Poly R-478, pelo fungo de podridão branca Trametes versicolor # 52J. Os experimentos de descoloramento foram realizados em operação semi-contínua durante três ciclos para melhorar a eficiência do processo. As melhores eficiências de descoloramento (65 % a 80%) foram obtidas em culturas de fungos tratadas em condições limitadas de nitrogênio em atmosfera de ar.