Felicita Briški

Modelling of Composting of Food Waste in a Column Reactor

The composting of organic solid waste, the mixture of fruit and vegetable leftovers enriched with night soil, was investigated in a closed thermally insulated reactor. It was found that 80.9 % of the original substrate biodegraded after 14 days. A mathematical model of the column reactor was proposed where the biodegradation rate of the organic solid waste was described using simple n-thorder kinetics. A good prediction of process performance was obtained using the proposed kinetics and experimentally obtained reaction heat.

Biodegradation of tobacco waste by composting: Genetic identification of nicotine-degrading bacteria and kinetic analysis of transformations in leachate

The tobacco industry produces large quantities of solid and liquid waste. This waste poses a significant environmental problem, as some major components are harmful and toxic. The aim of this work is to isolate and identify the nicotine-degrading microorganisms in the composting of tobacco waste. The bioremediation process for the detoxification of waste was carried out in a column reactor at an airflow-rate of 0.4 L min−1 kg−1. The concentrations of nicotine and number of CFU in the samples taken from reactor were monitored over nineteen days. After nineteen days, 89.8 % of nicotine conversion was obtained. A nicotine-degrading bacterium, strain FN, was isolated from the composting mass and identified as Pseudomonas aeruginosa on the basis of morphology, 16S rDNA sequence, and the phylogenetic characteristics. To confirm that the isolated Pseudomonas aeruginosa FN is the actual nicotine degrader, batch experiments were performed using tobacco leachate. It was confirmed that the strain FN possesses a considerable capacity to degrade nicotine with simultaneous COD removal. The Monod kinetic model for single substrate was applied to obtain the substrate degradation rate and half saturation constant.

Removal of Humic Substances from Aqueous Solution by Fungal Pellets

The removal of humic substances from aqueous solution at pH=4.8 and 6.0 and 25 °C by pure culture of Aspergillus niger has been examined. The removal of humic substances from aqueous phase was monitored by following the decrease in absorbance at 370 nm. COD and fungal growth were also measured. The initial concentration of humic and fulvic acids, pH and diameter of fungal pellets were found to be the most important parameters. The results suggested that decolorization of batch culture was a consequence of several processes. In the first 5 hours for pellets with diameter 1–3 mm and 10 hours for pellets with diameter 2–5 mm adsorption of humic substances was dominant. Afterwards, desorption of slightly bound humic substances and their degradation, as well as degradation of remaining humic substances in the solution, continued simultaneously through the period of 10 days.

Software sensors for monitoring of a solid waste composting process

Process identification for composting of tobacco solid waste in an aerobic, adiabatic batch reactor was carried out using neural network-based models which utilized the nonlinear finite impulse response and nonlinear autoregressive model with exogenous inputs identification methods. Two soft sensors were developed for the estimation of conversion. The neural networks were trained by the adaptive gradient method using cascade learning. The developed models showed that the neural networks could be applied as intelligent software sensors giving a possibility of continuous process monitoring. The models have a potential to be used for inferential control of composting process in batch reactors.

Zeolite and potting soil sorption of CO2 and NH3 evolved during co-composting of grape and tobacco waste

The gaseous byproducts produced during the composting of different kinds of solid waste are carbon dioxide (CO2) and ammonia (NH3). CO2 is a greenhouse gas and NH3 is a toxic and corrosive air pollutant so, they must be removed from exhaust gases prior to release into the atmosphere. The purpose of this work was to investigate the sorption of CO2 and NH3, evolved during composting, on zeolite and potting soil. The composting of the mixture of grape waste (GW) and tobacco waste (TW) in the mass ratio GW: TW = 55: 45 (dry mass basis) was carried out under forced aeration (0.645 L min−1 kg−1) in a column reactor (10 L) under adiabatic conditions over 21 days. Adsorption of the gases evolved was carried out in the fixed-bed column reactor (0.166 L). The most important physical-chemical characteristics of the composting mass and adsorbents and the evolved CO2 and NH3 were closely monitored. The highest CO2 and NH3 concentrations were measured at the thermophilic stage and the cooling stage of composting, respectively. The results showed that zeolite and potting soil were good adsorbents for the sorption of CO2 and NH3. The zeolite adsorbed 31 % of the evolved CO2 and the entire concentration of ammonia, whilst the potting soil adsorbed 3 % of CO2 and 49 % of NH3 from the exhaust gases.

Modelling of kinetics of microbial degradation of simulated leachate from tobacco dust waste

This paper presents a kinetic analysis of the biodegradation of organic pollutants in a batch bioreactor and investigates the kinetic properties of activated sludge using different mathematical models. The treatment was conducted for different initial concentrations of leachate from 500 mg dm−3 to 5000 mg dm−3 and initial concentrations of activated sludge from 1.84 g dm−3 to 6.62 g dm−3 over 48 h. Four different kinetic models were applied to the data. The kinetic analysis was performed with the traditional Monod model, the modified Monod model with endogenous metabolism, the Haldane model, and the Haldane model extended to include endogenous metabolic consumption and known as the Endo-Haldane model. Kinetic parameters for each model were determined using differential analysis and the Nelder-Mead method of non-linear regression. The lowest deviations and very good matches with the experimental data were achieved using the Endo-Haldane model. This indicated that this model best described the process of biodegradation of leachate from tobacco waste composting. This is due to this model incorporating the effects both of inhibition and endogenous metabolism.

Kinetic Analysis of Aerobic Composting of Tobacco Industry Solid Waste

Solid waste accumulated during the processing of tobacco for cigarette manufacture mostly contains tobacco particles and flavoring agents. Its main characteristics are a high content of nicotine, which is a toxic compound, and high value of total organic carbon of the aqueous extract. Because of this fact tobacco waste cannot be disposed of with urban waste.

Biodegradation of Agro-industrial Waste

The production of agro-industrial waste is growing worldwide and these wastes cannot be disposed on the ground without treatment. The objective of this work was to conduct composting process and anaerobic digestion of a mixture of agro-industrial waste (W), grape (GW), olive (OW) and tobacco (TW) waste. The composting process and anaerobic digestion of the mixture of GW, OW and TW in the ratio GW:OW:TW = 1:1:1.98 (dry matter) were carried out in column reactors with effective volume of 10 dm3 and 124 cm3, respectively, during 21 days. The composting experiment was carried out under forced aeration, while anaerobic digestion was conducted without aeration at temperature of 37 °C in anaerobic digester. Three different anaerobic experiments were conducted, without inoculum (E1) and with different ratio of inoculum and waste (E2, E3). During 21 days of composting of agro-industrial waste, the obtained conversion was 50 %. The volume of biogas produced during 21 days in experiments E1, E2 and E3 was 256 cm3, 280 cm3 and 162 cm3, respectively.

Emission of Gases During Composting of Solid Waste

Composting is a biochemical process converting organic components into stable compost with release of heat, water, CO2 and NH3. The objective of this work was to determine the amount of CO2 and NH3 in the exhaust gases during composting of tobacco waste (TW) and mixture of tobacco and grape waste (TGW). The cumulative evolved CO2 during 21 days of composting of TW and TGW, per mass of volatile matter, was 94.01 g kg−1 and 208.18 g kg−1, respectively, and cumulative evolved NH3 during composting of TW and TGW, per mass of volatile matter, was 504.81 mg kg−1 and 122.45 mg kg−1, respectively.