Claudio Mudadu Silva

Aerobic granular sludge to treat paper mill effluent: selection of ideal strains that contribute to the formation of strong aggregates

AbstractThe formation of aerobic granules after the treatment of paper mill effluents was feasible. Granular sludge presented a lower fouling potential than flocculent sludge, allowing a higher flux through the membranes in a membrane bioreactor (MBR). However, it was observed that after filtration many of the biogranules disrupted, which increased the membrane fouling. Therefore, the formation of aggregates that are physically and mechanically more resistant to decomposition would be beneficial to an MBR process. This work determines which of the microorganisms found in the aerobic granular sludge contribute to microbial aggregation, thereby increasing the mechanical resistance of aggregates. Nineteen strains were isolated from granular aerobic sludge. Tests for coaggregation showed that some isolates (E2, E7, E9, E13, and E25) were able to improve the formation of granules, while others (E10, E14, E18, and E26) inhibited the aggregation. The extracellular polymeric substances analyses indicated which su...

Integrated diversity analysis of the microbial community in a reverse osmosis system from a Brazilian oil refinery

Oil refineries are known for the large volume of water used in their processes, as well as the amount of wastewater generated at the end of the production chain. Due to strict environmental regulations, the recycling of water has now become a viable alternative for refineries. Among the many methods available to treat wastewater for reuse, the use of membranes in reverse osmosis systems stands out due to several economic and environmental benefits. However, these systems are vulnerable to contamination and deposition of microorganisms, mainly because of the feedwater quality. In this study, the microbial diversity of feedwater and reverse osmosis membranes was investigated using a combination of culture-dependent and culture-independent methods in order to characterize the microorganisms colonizing and deteriorating the membranes. In total, 37 bacterial isolates, 17 filamentous fungi and approximately 400 clones were obtained and analyzed. Among the bacterial genera identified, the most represented were Sphingobium, Acidovorax, Microbacterium, Rhizobium and Shinella. The results revealed genera that acted as candidate key players in initial biofilm formation in membrane systems, and provided important information concerning the microbial ecology of oligotrophic aquatic systems.

A multi-criteria decision analysis of management alternatives for anaerobically digested kraft pulp mill sludge

The Multi-Criteria Decision Analysis (MCDA) procedure was used to compare waste management options for kraft pulp mill sludge following its anaerobic digestion. Anaerobic digestion of sludge is advantageous because it produces biogas that may be used to generate electricity, heat and biofuels. However, adequate management of the digested sludge is essential. Landfill disposal is a non-sustainable waste management alternative. Kraft pulp mill digested sludge applied to land may pose risks to the environment and public health if the sludge has not been properly treated. This study is aimed to compare several recycling alternatives for anaerobically digested sludge from kraft pulp mills: land application, landfill disposal, composting, incineration, pyrolysis/gasification, and biofuel production by algae. The MCDA procedure considered nine criteria into three domains to compare digested sludge recycling alternatives in a kraft pulp mill: environmental (CO2 emission, exposure to pathogens, risk of pollution, material and energy recovery), economic (overall costs, value of products) and technical (maintenance and operation, feasibility of implementation). The most suitable management options for digested sludge from kraft pulp mills were found to be composting and incineration (when the latter was coupled with recycling ash to the cement industry). Landfill disposal was the worst option, presenting low performance in feasibility of implementation, risk of pollution, material and energy recovery.

Biological treatment and ultrafiltration of woodchip pre-hydrolysis liquor from dissolving pulp mills

Abstract Dissolving pulps could be considered as the future biorefineries, which normally generate liquor during the wood chip pre-hydrolysis (PHL). PHL has high chemical oxygen demand (COD) and biochemical oxygen demand (BOD). Mills do not have efficient means for disposal of PHL, being in general burned in the recovery boiler with a high cost due to its low consistency. The objectives of this work were to evaluate i) the biotreatability of PHL and the effects it would have on a kraft mill effluent biological treatment plant and ii) the use of ultrafiltration (UF) membrane to treat the PHL prior to biological treatment. PHL was generated into lab with a hydrothermal process and was mixed with kraft pulp mill effluent in different proportions and added to sequencing batch reactors (SBRs). The SBRs achieved high rates of COD removal (>75 %). However, treated effluent COD increased with the increase in PHL dose. This treatment using UF membranes reduced the COD load. Biotreatability of the UF permeate was higher than that of PHL. UF retentate, with 28 % of the volume and a much higher solids content than the initial PHL, would have a significantly lower evaporation energy demand if sent to the black liquor evaporators.

Thermal drying of industrial sludge using forced aeration

ABSTRACT This study investigated an industrial biosludge drying system using hot gases from a coal furnace, seeking to increase the solids content of the biosludge above 50% (w.b.), considered suitable for combustion in biomass boilers. Biosludge was collected from a paper mill activated sludge plant. Biosludge mixtures with eucalyptus chips and eucalyptus bark in two different proportions (15% and 25%) were placed into a drying chamber. Hot gases generated by the furnace, with a flowrate of 0.64 ± 0.02 m3 s−1 at 100 ± 20°C, were applied to the piles through a blowing system. The results demonstrated that the 75% biosludge/25% eucalyptus bark mixture achieved the best drying ratio, increasing the total solids content from 31% to 72%, over a 5-h drying period. Nevertheless, all other treatments involving the addition of a bulking agent achieved solids content above 50%, confirming the positive effect of adding dried material to the sludge. These results indicate a potential use of hot gases that are currently available and released into the atmosphere by paper mills. GRAPHICAL ABSTRACT