Giovana Tommaso

Characterization of aqueous phase from the hydrothermal liquefaction of Chlorella pyrenoidosa

This study investigated the characteristics of aqueous phase from hydrothermal liquefaction of low-lipid microalgae Chlorella pyrenoidosa. The interactions of operating conditions, including reaction temperature, retention time and total solid ratio were evaluated by response surface methodology. The chemical oxygen demand, total nitrogen and total phosphorus were selected as indicators of the property of AP. Results indicated that total solid ratio was found to be the dominant factor affecting the nutrient recovery efficiencies of AP. Based on energy recovery, GC-MS indicated that the AP at two optimized operating conditions (280 °C, 60 min, 35 wt.% and 300 °C, 60 min, 25 wt.%) were observed to have a higher concentration of organic acids (10.35% and 8.34%) while the sample (260 °C, 30 min, 35 wt.%) was observed to have the highest concentration of N&O-heterocyclic compounds (36.16%).

Chemical characterization and anaerobic biodegradability of hydrothermal liquefaction aqueous products from mixed-culture wastewater algae.

This study examined the chemical characteristics and the anaerobic degradability of the aqueous product from hydrothermal liquefaction (HTL-ap) from the conversion of mixed-culture algal biomass grown in a wastewater treatment system. The effects of the HTL reaction times from 0 to 1.5 h, and reaction temperatures from 260 °C to 320 °C on the anaerobic degradability of the HTL-ap were quantified using biomethane potential assays. Comparing chemical oxygen demand data for HTL-ap from different operating conditions, indicated that organic matter may partition from organic phase to aqueous phase at 320 °C. Moderate lag phase and the highest cumulative methane production were observed when HTL-ap was obtained at 320 °C. The longest lag phase and the smallest production rate were observed in the process fed with HTL-ap obtained at 300 °C. Nevertheless, after overcoming adaptation issues, this HTL-ap led to the second highest accumulated specific methane production. Acetogenesis was identified as a possible rate-limiting pathway.

Biochemical methane potential of raw and pre-treated meat-processing wastes

Raw and pre-treated greaves and rinds, two meat-processing wastes, were assessed for biochemical methane potential (BMP). Combinations of temperature (25, 55, 70 and 120 °C), NaOH (0.3 g g(-1) waste volatile solids) and lipase from Candida rugosa (10 U g(-1) fat) were applied to promote wastes hydrolysis, and the effect on BMP was evaluated. COD solubilisation was higher (66% for greaves; 55% for rinds) when greaves were pre-treated with NaOH at 55 °C and lipase was added to rinds after autoclaving. Maximum fat hydrolysis (52-54%) resulted from NaOH addition, at 55 °C for greaves and 25 °C for rinds. BMP of raw greaves and rinds was 707±46 and 756±56 L CH4 (at standard temperature and pressure) kg(-1)VS, respectively. BMP of rinds improved 25% by exposure to 70 °C; all other strategies tested had no positive effect on BMP of both wastes, and anaerobic biodegradability was even reduced by the combined action of base and temperature.

Anaerobic digestion of post-hydrothermal liquefaction wastewater for improved energy efficiency of hydrothermal bioenergy processes

Hydrothermal liquefaction (HTL) is a promising process for converting wet biomass and organic wastes into bio-crude oil. It also produces an aqueous product referred to as post-hydrothermal liquefaction wastewater (PHWW) containing up to 40% of the original feedstock carbon, which reduces the overall energy efficiency of the HTL process. This study investigated the feasibility of using anaerobic digestion (AD) to treat PHWW, with the aid of activated carbon. Results showed that successful AD occurred at relatively low concentrations of PHWW (≤ 6.7%), producing a biogas yield of 0.5 ml/mg CODremoved, and ∼53% energy recovery efficiency. Higher concentrations of PHWW (≥13.3%) had an inhibitory effect on the AD process, as indicated by delayed, slower, or no biogas production. Activated carbon was shown to effectively mitigate this inhibitory effect by enhancing biogas production and allowing digestion to proceed at higher PHWW concentrations (up to 33.3%), likely due to sequestering toxic organic compounds. The addition of activated carbon also increased the net energy recovery efficiency of AD with a relatively high concentration of PHWW (33.3%), taking into account the energy for producing activated carbon. These results suggest that AD is a feasible approach to treat PHWW, and to improve the energy efficiency of the HTL processes.

Effect of agitation on the performance of an anaerobic sequencing batch biofilm reactor in the treatment of dairy effluents

Agitation rate is an important parameter in the operation of Anaerobic Sequencing Biofilm Batch Reactors (ASBBRs), and a proper agitation rate guarantees good mixing, improves mass transfer, and enhances the solubility of the particulate organic matter. Dairy effluents have a high amount of particulate organic matter, and their anaerobic digestion presents inhibitory intermediates (e.g., long-chain fatty acids). The importance of studying agitation in such batch systems is clear. The present study aimed to evaluate how agitation frequency influences the anaerobic treatment of dairy effluents. The ASBBR was fed with wastewater from milk pasteurisation process and cheese manufacture with no whey segregation. The organic matter concentration, measured as chemical oxygen demand (COD), was maintained at approximately 8,000 mg/L. The reactor was operated with four agitation frequencies: 500 rpm, 350 rpm, 200 rpm, and no agitation. In terms of COD removal efficiency, similar results were observed for 500 rpm and 350 rpm (around 90%) and for 200 rpm and no agitation (around 80%). Increasing the systems agitation thus not only improved the global efficiency of organic matter removal but also influenced volatile acid production and consumption and clearly modified this balance in each experimental condition.

Morphological observation and microbial population dynamics in anaerobic polyurethane foam biofilm degrading gelatin

This work reports on a preliminary study of anaerobic degradation of gelatin with emphasis on the development of the proteolytic biofilm in polyurethane foam matrices in differential reactors. The evolution of the biofilm was observed during 22 days by optical and scanning electron microscopy (SEM) analyses. Three distinct immobilization patterns could be observed in the polyurethane foam: cell aggregates entrapped in matrix pores, thin biofilms attached to inner polyurethane foam surfaces and individual cells that have adhered to the support. Rods, cocci and vibrios were observed as the predominant morphologies of bacterial cells. Methane was produced mainly by hydrogenothrophic reactions during the operation of the reactors.

Clean Strategies for the Management of Residues in Dairy Industries

The transformation of raw milk into dairy products is one of the most important activities of the dairy industry worldwide. Along with the production of pasteurized and sterilized milks for direct consumption, a variety of processes are used for the production of cheeses, butter, cream, ice-creams, yogurts and other fermented milks. As a consequence, the processing of milk usually generates huge amounts of waste products, such as whey and buttermilk. These products have high nutrient and economic values; therefore they can be used as ingredients for others milk products such as flavored milk beverages, chocolates, candies, cookies, processed cheeses, ice cream, and powdered milk. Because of their intrinsic composition, dairy wastewaters cannot be discharged into septic systems, state waters or direct dumping; appropriate treatment is required before release into the environment. There are many alternatives for the treatment of this type of effluent, all based in a sequence of processes and operations presented as functions of physical-chemical characteristics of dairy waste effluent. The selection of some processes requires careful and must be based on, consideration of technical, economical, and social aspects.

THE INFLUENCE OF IRRIGATION WITH TREATED DAIRY WASTEWATER ON THE YIELD AND QUALITY OF TABLE BEET

Abstract. This work was conducted to evaluate the level of total soluble solids and the yield of the table beet irrigated with of the dairy treated effluent and with different irrigation depths. The experiment was conducted in a greenhouse (210 m 2 ), near of the dairy effluent treatment plant of the University of SA£o Paulo, located at Pirassununga, Brazil. The treatments consisted of three types of water: (1) Anaerobic Effluent – ANE; (2) Aerobic Effluent – AE; (3) Treated rainwater – RW. Three different irrigation depths were used, 50, 100 and 150 % of the crop water demand. All these treatments were applied combined with 50% of the mineral nitrogen fertilization recommended for the table beet. Apart from these, there was a control (table beet with 100% of the nitrogen fertilization recommended, irrigated with water and irrigation depth equal to 100% of the crop water demand). The use of wastewater and the higher irrigation depths promoted differences in the evaluated parameters. Comparing the treatments, it is possible to note that the table beet development was most favorable when irrigated with ANE and AE. The irrigation with ANE was superior in all irrigation depths compared to other treatments (AE and RW). This indicates the importance of differentiating the source of available nutrients (particularly nitrogen) in the wastewater. The level of total soluble solids were not affected by water quality, but were reduced with the increasing of irrigation depths applied with treated dairy wastewater. However the obtained values did not reduce the table beet quality.

Food By-products for Biofuels

The rise in global energy usage, together with the disappearance of fossil fuel reserves, has highlighted the importance of developing technologies to harness new and renewable energy sources. In addition to sustainability, climate change is another major issue that has driven the search for clean carbon-neutral fuels.