Assessing a mixture of biosurfactant and enzyme pools in the anaerobic biological treatment of wastewater with a high-fat content.

The use of rhamnolipid-type biosurfactant produced by Pseudomonas aeruginosa was evaluated for solubilization of fat present in effluent from a poultry processing plant, followed by anaerobic biological treatment. The rhamnolipid was used in combination with enzyme pools produced by solid medium fermentation of the fungi Penicillium simplicissimum and Penicillium brevicompactum. In experiments with raw effluent, the accumulation of fat caused the specific methane production (SMP) to be much less than with pretreated effluent (0.074 vs. 0.167 L CH4/g chemical oxygen demand (COD) removed). In experiments with pretreated effluent, the SMP ranged from 0.105 to 0.207 L CH4/g CODremoved. A statistical analysis of the results of four sequential batches found that all variables had a significant effect on the SMP in the fourth batch. A fifth batch was initiated for three conditions, and it led to the highest SMP when compared with the control, which showed similar behaviour for the SMP over time, ending up with values three times greater than the SMP in the control conditions. The residual oil and grease analysis revealed removals from 51% to 90% with pretreated effluent and only 1% in the control conditions with raw effluent. Thus, the best synergistic effect of fat release/hydrolysis of effluent components from a poultry processing plant was found with a 0.5% P. brevicompactum pool and rhamnolipid at half the critical micelle concentration (24 mg/L).

Profiles of fatty acids and triacylglycerols and their influence on the anaerobic biodegradability of effluents from poultry slaughterhouse.

The hydrolysis of effluent from a poultry slaughterhouse containing 800 mg oil and grease (O&G)/L was conducted with 1% (w/v) of an enzymatic pool obtained by solid-state fermentation with the fungus Penicillium restrictum. The chromatographic evaluation of the lipid profile during hydrolysis indicated a higher concentration of acids after 4h of reaction (2954 mg/L), with a predominance of oleic, palmitic, and linoleic acids. Effluent aliquots were collected after 4, 8, and 24h of hydrolysis and tested for anaerobic biodegradation in sequential batches. An adaptation of the biomass was observed, both in the control experiment (with non-hydrolyzed raw effluent) and in the experiments with enzymatically pre-treated effluent. The specific methane production in the control experiment was 0.248 L CH(4)/g COD(consumed), and in the experiment with effluent pre-treated for 4h, this production was 0.393 L CH(4)/g COD(consumed), indicating a higher methane production after enzymatic hydrolysis.

Evaluation of different pre-hydrolysis times and enzyme pool concentrations on the biodegradability of poultry slaughterhouse wastewater with a high fat content.

The effect of different hydrolysis times (4, 8 and 24 h) of a lipase-rich enzymatic preparation (0.1, 0.5 and 1.0% w/v) produced by fungus Penicillium sp. in solid-state fermentation was evaluated on the anaerobic biodegradability of a poultry slaughterhouse wastewater with 800 mg oil and grease [O&G]/L in three sequential batches. The enzymatic pre-treatment of O&G in the experiments with no acclimated sludge had no discernible effect because regardless of the conditions adopted COD removal efficiencies of 95.3% to 98.7% were obtained. However, when the sludge was reused (once or twice) the COD removal efficiencies in the control experiments (69.8% and 53.4%) were considerably lower than in the experiments with hydrolyzed effluent (of 93.8% to 98.4%). Higher values of specific methane production were obtained with 0.1% SEP and 4 h of hydrolysis. After acclimation of the sludge, 19.9% fat was still adhered to the sludge in the control experiment, while the sludge in the experiment with enzymatically pre-treated effluent contained only 8.6% fat, confirming the accumulation of fat when the enzyme pool was not used.

A review on hydrolytic enzymes in the treatment of wastewater with high oil and grease content.

Wastewater from dairies and slaughterhouses contains high levels of fats and proteins that present low biodegradability. A large number of pretreatment systems are employed to remove oil and grease (O&G) to prevent a host of problems that may otherwise arise in the biological process, and reduce the efficiency of the treatment station. Problems caused by excessive O&G include a reduction in the cell-aqueous phase transfer rates, a sedimentation hindrance due to the development of filamentous microorganisms, development and flotation of sludge with poor activity, clogging and the emergence of unpleasant odors. Therefore the application of a pretreatment to hydrolyze and dissolve lipids may improve the biological degradation of fatty wastewaters, accelerating the process and improving time efficiency. However thus far, only a few studies describing the degradation of fats and oils by alkaline/acid/enzymatic hydrolysis have been reported; the treatment of effluents from several origins is a new and promising application for lipases. Among the strains that produce the hydrolytic enzymes studied, the fungus Penicillium restrictum is a particularly promising one. When cultivated in low-cost solid medium composed of agro-industrial waste, P. restrictum produces a pool of hydrolases capable of degrading the most complex organic compounds. This degradation enables a considerable increase in organic matter removal efficiency to be realized, which results in the attainment of a high-quality effluent in the subsequent biological treatment stage. Consequently, there is presently a wide variety of ongoing scientific investigation in the field of developing enzymatic hydrolysis processes to precede traditional biological treatment.

Reduction on the anaerobic biological activity inhibition caused by heavy metals and sulphates in effluents through chemical precipitation with soda and lime.

The School of Chemistry Environmental Technology Laboratory generates 43.4 1 of effluent with low pH (0.7) and high contents of COD (1908 mgO2 l(-1)), phenol (132.1 mg l(-1)), sulfate (36700 mg l(-1)) and heavy metals (28.2 mg Hg l(-1); 82.1 mg Cr(total) l(-1); 30.8 mg Cu l(-1); 57.4 mg Fe(total) l(-1); 16.2 mg Al l(-1)) weekly. These data show that this effluent presents high toxicity for biological treatment, with a physical-chemical step being necessary before a biological step. Preliminary studies showed that the most toxic constituents of the effluent were sulfate, phenol and total chromium. In this work, a chemical precipitation step with sodium hydroxide or lime was evaluated for the toxicity reduction on anaerobic microbial consortium. These experiments were carried out with increasing concentrations of alkalis in the effluent in order to obtain pH initial values of 8-12. Similar results were obtained for COD (15-28%), turbidity (95-98%), phenol (13-24%) and total chromium (99.8-99.9%) removals in each condition studied with soda or lime. Sulfate was only removed by precipitation with lime, obtaining reductions from 84 to 88%. The toxicity on the anaerobic sludge was studied employing specific methanogenic activity (SMA) analysis of raw and treated effluent (after chemical precipitation step). The SMA experiments showed that chemical precipitation at pH 8 reduces the toxic effect of the effluent on anaerobic microbial consortium three times (with soda) and thirteen times (with lime). These results indicate that precipitation with lime is more efficient at toxicity removal, however the produced sludge volume is around two times higher than that produced with soda.

Degradation potential and growth of anaerobic bacteria in produced water.

The efficiency of an anaerobic biological treatment for the reduction of essential contaminants of produced water from an offshore oilfield was investigated using a microbial consortium enriched with sulphate-reducing bacteria (SRB). Experiments were conducted in a bench bioreactor at 35 degrees C, 250 rpm, with intermittent purges of N2 gas in order to establish anaerobic conditions and to remove the H2S generated. The results showed that pH control effectively influenced the activity of the anaerobic bacteria leading to COD removal of 57%. Meanwhile, pH control was found to have no influence on the removal efficiencies of oil and grease and total phenols. In all experiments, removals of oil and grease and total phenols of 60% and 58-67%, respectively, were obtained after a 15-day process. In studies carried out with biomass reuse the reductions obtained were 61% for oil and grease and 78% for total phenols over the same period. Such results point to the technical feasibility of anaerobic biodegradation for oilfield wastewater treatment.

Decolorization of dyes from textile wastewater by Trametes versicolor.

The white rot fungus Trametes versicolor was applied to the decolourisation of three synthetic textile dyes in the presence and absence of glucose. Different initial dye concentrations were tested and approximately 97% decolourisation was achieved. It was found that fungal metabolism induced by the glucose as well as the pH play an important role in the decolourisation process. This treatment was also applied to a real wastewater from a textile industry-dyeing sector leading to 92% decolourisation.

A new procedure for treatment of oily slurry using geotextile filters.

A new procedure to mitigate the environmental impacts and reduce the cost of disposal of oil slurry is present in this paper. Waste from the petroleum industry has a high environmental impact. Systems for oil-water separation have been used to mitigate the contamination potential of these types of effluents. At the outlet of these systems, the oil is skimmed-off the surface, while the slurry is removed from the base. Due to the high concentration of contaminants, the disposal of this slurry is an environmentally hazardous practice. Usually this type of waste is disposed of in tanks or landfills after removal from the industrial plant. Basically, the proposed procedure utilizes drying beds with geotextile filters to both reduce the water content in the slurry and obtain a less contaminated effluent. Laboratory tests were carried out to simulate the drying system. Four types of filters were analyzed: two non-woven geotextiles, one woven geotextile, and a sand filter.

Extraction of activated sludge bacteria exopolymers by ultrasonication.

Ultrasonication for the extraction of activated sludge exopolymers was evaluated by total cell count, exopolymer extraction and transmission electron microscopy (TEM). A high deflocculation was achieved after 30 s of sonication in PBS (phosphate-buffered saline). TEM showed that cell lysis was minimal only when sludges were sonicated for 30 s. For sludges sonicated for 30, 90 and 420 s and stained with Ruthenium Red, exopolymers were not extracted on a large scale without considerable cell lysis. Sludges sonicated for 30 s in EDTA gave a larger fraction of damaged cells and also showed copious amounts of attached exopolymers.

Biological treatment of oil field wastewater in a sequencing batch reactor.

This work reports the results of experiments carried out in a sequencing batch reactor (SBR) operated under 24 hour cycles, treating an effluent containing a mixture of oil field wastewater and sewage, in different percentages. The removal of phenols, ammonium and COD was monitored in several experimental runs, varying the dilution degree of the oilfield wastewater (10 to 45% v/v). The volatile suspended solids (VSS) content in the reactor was also monitored and the protein (PTN) and polysaccharide (PS) contents of the suspended biomass were determined. The removal of ammonium and phenols did not vary significantly in the experimental runs, attaining average values of 95% and 65%, respectively. COD removal efficiencies in the range of 30 to 50% were attained in the experiments carried out with dilution percentages of 45 and 35% (v/v) respectively. An experiment carried out with a lower proportion of produced water (15% v/v), keeping the salinity level corresponding to a higher proportion of industrial effluent (45% v/v), led to an improvement in the COD removal, indicating that the recalcitrance of the organic compounds found in the effluent is the main cause ofthe moderate COD removal efficiencies attained in the SBR system. With regard to the composition of the microbial flocs, no significant variation was observed in the PS/PTN, PS/VSS and PTN/VSS ratios when the effluent composition changed (increased salinity and levels of organic material).