Semi-continuous treatment of recalcitrant anaerobic effluent from pulp and paper industry using hybrid pellets of Trametes versicolor.

The objective of this work was to evaluate the semi-continuous post-treatment of anaerobically-pre-treated weak black liquor (anaerobic effluent, AnE) by aerobic post-treatment using hybrid pellets of Trametes versicolor. The latter consisted of fungus immobilized onto holm oak sawdust (mixed or double pellets) or a mixture of holm oak sawdust and powdered activated carbon (triple pellets). First, a semicontinuous experiment was run to compare the effectiveness of triple and mixed pellets in agitated flasks for 15 cycles of 7 days each. A second extended batch test was implemented with 500 mL AnE and triple pellets to give 400 mg fungal biomass; some units were spiked with protease inhibitor. In the first experiment, triple pellets displayed consistently higher removal efficiencies of pollutant parameters than double pellets (10 to 15% higher), although overall averages were moderate and no statistical significance to the difference could be set because of the noise of fluctuations. Periodic fluctuations of removal were characterized by three periods of approximately six cycles each with maximum removals occurring at cycles 3-4, 7-9, 13, and 14. Evaluating pooled removals of the latter cycles showed that triple pellets were significantly more effective than double pellets, with removal efficiencies as high as 47% of COD, colour, and absorbance at 254 nm (A254). In general, protease activity seemed to increase in the third period (last six cycles), whereas activities of MnP, LiP and Lac significantly decreased. In the second experiment, pollutant removals and enzymatic activities of triple pellets with protease inhibitor were significantly higher than those of units without added protease inhibitor. These results indicate that protease could be the main cause of periodic falls of pollutant removal efficiencies found in the first experiment.

Study of the cellular retention time and the partial biomass renovation in a fungal decolourisation continuous process.

The long-term continuous decolourisation treatment of the textile dye Grey Lanaset G (150 mg/l) was carried out in an air-pulsed bed bioreactor with retained pellets of the white-rot fungus Trametes versicolor. Maximum cellular retention time (CRT) was established at 40 days. During this time period, colour reduction remained at 90% and laccase activity was over 400 AU/l. Higher CRTs involved operational problems related to biomass conglomerates formed at the top of the bioreactor, which made individual movement of the pellets difficult. In order to carry out the long-term continuous treatment, a strategy of purge and biomass renovation that had to allow fungal stable activity levels to be maintained was planned. The purge and biomass renovation strategy consists of partial biomass renovations: 1/3 of the total biomass of the system is renewed every 1/3 of the CRT. Different CRTs were tested; with a CRT of 21 days carrying out partial biomass renovations every 7 days and with a hydraulic retention time of 2 days, decolourisation percentages higher than 80% were obtained, maintaining a young culture in the bioreactor and guaranteeing microbial activity. In accordance with the strategy observed, different simulations of the age of the biomass in the bioreactor were carried out, obtaining suitable age distributions for CRT of 20-21 days.

Olive oil mill waste waters decoloration and detoxification in a bioreactor by the white rot fungus Phanerochaete flavido-alba.

Olive oil mill wastewater (OMW) is produced as waste in olive oil extraction. With the purpose of treating this highly polluting waste, a number of experiments were conducted in a laboratory-scale bioreactor with the white rot fungus Phanerochaete flavido-alba (P. flavido-alba). It is known that this fungus is capable of decolorizing OMW in static or semistatic cultures at Erlenmeyer scale and at 30 degrees C. The objective of this work was to prove that P. flavido-alba could decolorize OMW in submerged cultures and that it is capable of reducing OMW toxicity at room temperature (25 degrees C) and in a laboratory-scale bioreactor. In the experiments conducted, manganese peroxidase (MnP) and laccase enzymes were detected; however, unlike other studies, lignin peroxidase was not found to be present. Decoloration obtained after treatment was 70%. The reduction of aromatic compounds obtained was 51%, and the toxicity of the culture medium was reduced by up to 70%. We can therefore state that P. flavido-alba is capable of reducing important environmental parameters of industrial effluents and that prospects are positive for the use of this process at a larger scale, even when working at room temperature.