Biomass In Reactor Research Articles

Production of high purity biodiesel through direct saponification of wet biomass of Chlorella protothecoides in a low cost microwave reactor: Kinetic and thermodynamic studies

We studied production of biodiesel from microalga Chlorella protothecoides (SAG 211-10 C) through direct saponification of its wet biomass (70% moisture) in a microwave reactor using ethanolic potassium hydroxide. The resulting soap was precipitated by “common ion effect” using saturated solution of potassium chloride and subjected to simultaneous acidulation and esterification to form biodiesel. The optimum parameters for saponification were: Temperaure- 60 °C, Ethanol to dry biomass ratio (ml/g)-80 : 1, concentration of KOH-0.5%, microwave power-450W; and for esterification they were Temperature-60 °C, wt% of sulfuric acid-2.5%, molar ratio of methanol to fatty acids-70 : 1, microwave power-450W. The kinetics and thermodynamics of saponification and esterification were investigated. Both reactions were found to follow pseudo-first-order kinetics. Activation energies were determined as 14.177 kJ/mol and 17.234 kJ/mol for saponification and esterification, respectively. The final biodiesel yield and purity were 98.74% and 94.83%, respectively.

Characterization of Aerobic Granular Sludge Developed under Variable and Low Organic Loading Rate

Understanding the formation of aerobic granules sludge (AGS) under the variations of organic loading rate (OLR) could give a different insight on AGS stability, which had become the bottleneck for practical application in sewage treatment. This study demonstrates the formation of AGS that had previously been stored for eight months at 5oC in sequencing batch reactor (SBR) with sewage as substrate. Despite being redeveloped under variable OLR of 0.26 to 0.81 kg CODs/m3 d and low superficial air velocity (SAV) of 1.33 cm/s, the loose structure of AGS during storage can be recovered within 46 days of formation process. Variations in OLR intrude the formation process particularly during low OLR, resulting in longer period to achieve mature AGS or full granulation of biomass in reactor. The next-generation sequencing (NGS) analysis indicated that the shift in microbial community from Rhodocyclaceae to Comamonadaceae class for denitrification process was accommodated with the changes in the AGS size from 326 μm to more than 600 μm.

High-throughput sequencing-based microbial characterization of size fractionated biomass in an anoxic anammox reactor for low-strength wastewater at low temperatures

The microbial characterization of three size-fractionated sludge obtained from a suspended-growth anoxic anammox reactor treating low-strength wastewater at low temperatures were investigated by using high-throughput sequencing. Particularly, the spatial variability in relative abundance of microorganisms involved in nitrogen metabolism were analyzed in detail. Results showed that population segregation did occur in the reactor. It was found, for the first time, that the genus Nitrotoga was enriched only in large granules (>400μm). Three anammox genus including Candidatus Jettenia, Brocadia and Kuenenia were detected. Among them, Candidatus Brocadia and Kuenenia preferred to grow in large-sized granules (>400μm), whereas Candidatus Jettenia dominated in small- and moderate-sized sludge (<400μm). The members of genus Candidatus Jettenia appeared to play the vital role in nitrogen removal, since sludge with diameters smaller than 400μm accounted for 81.55% of the total biomass. However, further studies are required to identify the activity of different-size sludge.

Effect of intermittent aeration on microbial diversity in an intermittently aerated IFAS reactor treating municipal wastewater: A field study

ABSTRACTIn the present study, the effect of three intermittent aeration (IA) cycles on treatment performance and microbial diversity was investigated in an integrated fixed film activated sludge (IFAS) reactor treating municipal wastewater. The results showed that IA strategies were able to achieve efficient removal of organics and nitrogen ranging between 90 and 95% and 70 and 80%, respectively, however the phosphorus removal was found to be inversely proportional to the duration of aeration off time in each IA cycle. The microscopic analysis revealed that the suspended and attached biomass had compact morphology and open floc structure, respectively. For each gram of volatile suspended solids, 165 and 148 mg of extracellular polymeric substances (EPS) were extracted from attached and suspended biomass, respectively, constituting carbohydrates (∼24%), proteins (∼31%), humic acids (∼28%), DNA (∼2%) and unknown substances (∼12%). The microbial diversities of suspended biomass in IFAS reactor were investigated using culture-dependent approach, which confirmed the presence of Clostridium spp., Pseudomonas spp., Bacillus spp., Escherichia coli spp., Nitrosococcus spp., Streptococcus spp., Acinetobacter spp., Betaproteobacteria outliers, Klebsiella pneumoniae, Klebsiella aerogenes, Serratia marcescens, Micrococcus, Proteus vulgaris spp., Actinomycetes spp., and Actinobacteria including Micromonospora spp. and Streptomyces spp. Molecular tools for diversity analyses were used for ammonia and nitrite oxidizer identification, such as Nitrospira and Nitrosococcus species. Denitrifiers include the species of Pseudomonas, Betaproteobacteria and Flavobacterium. Acinetobacter, Betaproteobacteria and Gammaproteobacteria were responsible for the phosphorus removal in the present system. Overall, the system performed efficiently showing Proteobacteria (59%), Acinetobacter (12%) and Bacteroidetes (11%) as the dominant bacterial groups. However, the dominance of the bacterial diversity varied with the IA cycle time numerating the maximum percentage of bacterial species during IA1 phase i.e. 2.5 h aeration/0.5 h non-aeration.

Elimination of organic micro-contaminants in municipal wastewater by a combined immobilized biomass reactor and solar photo-Fenton tertiary treatment

AbstractMunicipal wastewater treatment plants (MWTPs) have become one of the main sources of water for potential reuse. However, some pharmaceuticals, pesticides, hormones and others organics escape conventional wastewater treatments, and therefore, new technologies must be applied to overcome the problem. This article presents an efficient alternative that combines an aerobic immobilized biomass reactor (IBR) with a solar photo-Fenton process as a tertiary treatment. Real municipal wastewater was treated in the IBR system in batch and continuous modes. Micro-pollutants were monitored by using an advanced analytical procedure consisting of pre-concentration of samples by solid phase extraction (SPE) followed by liquid chromatography coupled to mass spectrometry. Results were compared with those observed in the MWTP secondary conventional activated sludge treatment. Effluents from the IBR, operating at the maximum treatment capacity, were treated in a previously optimized solar photo-Fenton pilot plant as a tertiary treatment to entirely eliminate remnant micro-pollutants.

A two dimensional Euler-Lagrangian model of wood gasification in a charcoal bed — Part III: Parameter influence and comparison

The efficient utilization of biomass in fluidized bed reactors depends on numerous operation conditions and parameters which can be investigated systematically with computational models. Based on a previous study [1] we compare a base scenario which mimics the experimental situation with different parameter settings for an Euler-Lagrangian simulation of wood gasification in a fluidized charcoal bed. For the varied parameters superficial velocity, reactor wall temperature, air inlet temperature, wood particle size, and the wood inlet temperature we analyse the simulation results based on data for temporal evolution of reactor outlet temperature, averaged particle temperature, overall wood mass, overall charcoal mass, concentrations of several gaseous species (N2, CO, CO2, H2, H2O, CH4, C2H2, and three virtual tar components) and axial barycenter data of particles bed mass. Furthermore we show time averaged data for gaseous species and gas phase temperature at the reactor outlet. At the end we critically examine our findings under consideration of the models opportunities and limitations.

On the oxy-combustion of lignite and corn stover in a lab-scale fluidized bed reactor

This paper addresses an experimental investigation concerning oxy-combustion of coal and biomass in a lab-scale fluidized bed reactor. While co-firing has been widely studied under conventional air conditions, few experiences are available to date for O2/CO2 atmospheres. The research is focused on SO2 and NOx emissions, along with the deposition rates and ashes mineralogy. The influences of the atmosphere (air vs. 30/70% O2/CO2), the coal-to-biomass energy input ratio (80/20%, 90/10%), the chlorine mass fraction in the biomass (0.35%, 1%, 2%) and the Ca:S mole ratio (2.5, 4) are reported and discussed in the paper, for two specific fuels: high sulfur lignite and high chlorine corn stover. Concerning SO2 emissions a correlation among the sulfur and the chlorine contents is clearly detected, being affected by the direct desulfurization mechanism occurring under oxy-firing conditions. The single effect of the chlorine content is found to be almost 1.5% of the desulfurization efficiency. NOx emissions are otherwise more dependent on oxygen excess and CO concentration in the reactor, rather than the fuel share or the chlorine supplied. Thick deposition is only detected when chlorine content in the corn is 2%. Potassium aluminosilication is found to be enhanced in comparison to potassium sulfation under oxy-firing, especially for the highest Ca:S mole ratio: observed aluminosilication is five times higher when Ca:S ratio is increased from 2.5 to 4. A significant enrichment in iron is also detected for the fly ash composition, with an increase of 30–50% in comparison to air combustion.

Biodegradation of Methanol Using Thiosulphate as an Electron Acceptor Under Anaerobic Conditions.

Background.Methanol is a volatile organic compound commonly found in the effluent of the pulp and paper industries. Because of its toxicity, methanol can cause metabolic acidosis, neurologic sequelae, and even death when ingested. Information on biokinetic activity such as biodegradation rate of methanol and thiosulphate, biomass growth rate and biomass yield coefficient is limited in the literature.Objectives.To study the biomass growth rate and biomass yield coefficients of methanol and thiosulphate biodegradation. This research aims to increase knowledge of how to reduce the emission of toxic gas to the environment.Methods.The biodegradation trends of both methanol and thiosulphate were studied under anaerobic conditions using batch experiments at ambient temperature and alkaline conditions. Both supplement each other for their degradation. Methanol is an electron donor, whereas thiosulphate acts as an electron acceptor. A mixed culture from a previously used biomass in a biotrickling filter reactor from theUnited Nations Educational, Scientific and Cultural Organization (UNESCO), International Graduate Water Education Facility and fresh activated sludge from the Harnaschpolder wastewater treatment plant were used as a biomass source.Results.A specific biomass growth rate of biomass ranging from 0.04 to 1.7g per day was observed. The thiosulphate is biologically degraded by the biomass grown inside the reactor. The biodegradation rate of thiosulphate in the reactor varied from 0.02 to 0.80g per unit gram of biomass per day. A biodegradation rate of methanol in the reactor was observed in the range between 0.04 to 3.9g per unit gram of biomass per day. Bacterial biomass was grown as per the amount of methanol present inside the reactor. A maximum biomass yield coefficient of 0.7g biomass per gram of methanol was recorded. Thiosulphate was converted to sulphate that indirectly served as an electron acceptor for methanol degradation. Both degradation of methanol and thiosulphate in this experiment were in the range of the degradation rate shown for sulphate and organic compounds in other studies.Conclusion.Simultaneous removal of thiosulphate and methanol using an anaerobic bioreactor is promising and can be applied on an industrial scale. This finding is an important contribution to public health as it reduces the emission of toxic gas to the environment.

Valorization of Napier grass via intermediate pyrolysis: Optimization using response surface methodology and pyrolysis products characterization

This study presents first optimization report on pyrolysis oil derived from Napier grass. Effects of temperature, heating rate and nitrogen flow rate on the intermediate pyrolysis of Napier grass biomass in a vertical fixed-bed tubular reactor were investigated collectively. Response surface methodology with central composite design was used for modelling the process and optimization of the process variables. Individual second order polynomial model was found to be adequate in predicting bio-oil, bio-char and non-condensable gas yield. The optimum bio-oil yield of 50.57 wt% was recorded at 600 °C, 50 °C/min and 5 L/min nitrogen flow. The bio-oil obtained throughout this study was two-phase liquid, organic and aqueous phase. The bio-oil, bio-char and non-condensable gas were characterized using standard analytical techniques. The results revealed that the organic phase consists of hydrocarbons and various benzene derivatives, which can be further processed into fuels and valuable chemicals. The aqueous phase was predominantly water, acids, ketones, aldehydes and some phenolics and other water-soluble organics. The non-condensable gas was made up high hydrogen/carbon monoxide ratio suitable for liquid fuel synthesis via Fischer-Tropsch Synthesis. The bio-char was a porous carbonaceous material with high energy content, which can be applied as a solid fuel, adsorbent or source of biofertilizer. This study demonstrated that Napier grass biomass is a viable feedstock for production of high-value bioenergy precursors.

Simultaneous investigation into the yields of 22 pyrolysis gases from coal and biomass in a small-scale fluidized bed reactor

Flash pyrolysis gas yields from bituminous coal and torrefied biomass have been investigated in the temperature range between 873 and 1273K for 22 different gas species simultaneously. Recording a larger number of species gives a more detailed insight into pyrolysis of solid fuels than it is provided by other studies in literature, where typically smaller numbers of species are tracked. As processes utilizing biomass are designed for lower process temperatures, literature data for biomass pyrolysis are scarce in the temperature range between 1023 and 1273K. This work, aiming at investigating potential fuels for pulverized solid fuel combustion, approximates pyrolysis conditions in the ignition zone of actual power plant boilers, where possible.Thus, based on results of a literature review, an experiment was designed using a small-scale fluidized bed reactor (FBR) to simultaneously analyze the pyrolysis gas yields for 22 species and to close the temperature gap found for biomass. Small batches of pulverized torrefied biomass from poplar wood and pulverized Colombian bituminous coal (Mina Norte) were rapidly pyrolyzed in the reactor. The two fuels were chosen as exemplary conventional and alternative energy sources for pulverized fuel fired power plants. Experiments have been carried out under atmospheric pressure in pure nitrogen atmosphere.Product gas analysis was carried out by Fourier transform infrared spectroscopy (FTIR) including two different sampling techniques. As a novelty, offline measurements have been used exclusively to improve the gas species selection procedure and reliability of detection. In case of offline measurements, the gas flow to the FTIR gas cell is stopped and the gas is enclosed in the cell allowing longer scan times of the captured gas mixture and thereby enlarging the signal-to-noise ratio (SNR). In succession, regular measurements with continuous flow (online) were performed for the simultaneous quantitative analysis of total pyrolysis yields for 22 selected gas species.Obtained pyrolysis yields show good agreement with available literature data. The larger number of investigated species provides an extended data set also covering minor pyrolysis species, for which quantitative data are scarce. Additionally, trends in the gas yields for biomass agree well with those found by other authors outside the mentioned temperature gap between 1023 and 1273K.

2,4-Dinitrotoluene removal in aerobic granular biomass sequencing batch reactors

Aerobic granules were cultivated in sequencing batch reactor (SBR) by feeding 2,4-dinitrotoluene (2,4-DNT) along with acetate. Aerobic granules with an SVI10 of 34.57 ± 2.6 mL g−1 and average diameter of 0.78 ± 0.3 mm were formed during 30 d of SBR start-up period. In an alternative approach, aerobic granules cultivated using acetate as carbon source were acclimatized and evaluated for 2,4-DNT removal. In both the approaches, the aerobic granules exhibited rapid 2,4-DNT removal wherein >90% of 10 mg L−1 2,4-DNT was removed within 24 h cycle period. The aerobic granules also exhibited ammonium-nitrogen and phosphorus removal in addition to organic carbon removal, indicating that presence of 2,4-DNT did not negatively affect nutrient removal. In aerobic granular biomass reactors, most of the organic carbon was consumed within the first 6 h while, majority of the 2,4-DNT was removed during the 24 h cycle period. HPLC analysis detected smaller amounts of 2-amino-4-nitrotoluene, a biotransformation product of 2,4-DNT. 2,4-DNT removal by granules under anaerobic conditions was observed to be much smaller compared to the aerobic SBR. Thus, 2,4-DNT removal by aerobic granules was likely mediated by combination of both oxidative and reductive pathways. Although, the mechanisms of 2,4-DNT removal requires further investigations, effective and stable removal of 2,4-DNT in aerobic granular biomass reactors offers practical possibilities for treatment of wastewaters from ammunition factories.

Potential of using non-inoculated self-aerated immobilized biomass reactor for post-treatment of upflow anaerobic staged reactor treating high strength industrial wastewater

BACKGROUND Cake industry produces a heavily polluted wastewater that is characterized by high amounts of suspended solids, lipids, chemical oxygen demand (COD), biochemical oxygen demand (BOD5) and nitrogen components. In this study, assessment the efficiency of non-inoculated self-aerated immobilized biomass (SAIB) reactor for post-treatment of the anaerobic effluent of cake processing wastewater was extensively investigated. RESULTS The reactor was operated at different hydraulic retention times (HRTs) and sludge residence times (SRTs). CODt and CODs removal efficiencies increased from 50 ± 15.2 to 61.8 ± 20.7% and from 51.6 ± 9.3 to 60 ± 17.8% at increasing the HRT from 2.5 to 5.0 h, respectively. Maximum nitrification efficiency and biomass concentration of 67% ± 3.1% and 39.8 gVS/ Lsponge was obtained at an SRT of 42 days. The results of the empirical model showed a good agreement between predicted and experimental values. Ammonium oxidizing bacteria (AOB) was dominated and represented 0.14% at the middle zone of the reactor where the dissolved oxygen is sufficient for growth of nitrifiers. CONCLUSION The innovative (SAIB) reactor was able to treat cake wastewater with high content of carbon and lipids in comparison with the other conventional technologies. The efficiency of the reactor was contingent mainly on HRT, SRT, VSS/TSS ratio, F/M ratio and CODp/CODt ratio.

Consolidated bioprocessing of microalgal biomass to carboxylates by a mixed culture of cow rumen bacteria using anaerobic sequencing batch reactor (ASBR)

This study employed mixed-culture consolidated bioprocessing (CBP) to digest microalgal biomass in an anaerobic sequencing batch reactor (ASBR). The primary objectives are to evaluate the impact of hydraulic residence time (HRT) on the productivity of carboxylic acids and to characterize the bacterial community. HRT affects the production rate and patterns of carboxylic acids. For the 5-L laboratory-scale fermentation, a 12-day HRT was selected because it offered the highest productivity of carboxylic acids and it synthesized longer chains. The variability of the bacterial community increased with longer HRT (R2=0.85). In the 5-L laboratory-scale fermentor, the most common phyla were Firmicutes (58.3%), Bacteroidetes (27.4%), and Proteobacteria (11.9%). The dominant bacterial classes were Clostridia (29.8%), Bacteroidia (27.4%), Tissierella (26.2%), and Betaproteobacteria (8.9%).

Long-term operation of anaerobic immobilized biomass reactor treating organic wastewater containing sulfate

This work evaluates the long-term performance (888 days) of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor fed with synthetic wastewater containing organic matter and sulfate. The HAIB reactor achieved stable performance, exhibiting high sulfate and organic matter removal efficiencies subjected to organic matter concentration (expressed as chemical oxygen demand – COD) of 1500mg/L and sulfate of 500mg/L. Sulfate removal efficiency close to 100% was obtained for COD/sulfate ratios equal to or higher than 2.6, decreasing to ∼80% for COD/sulfate ratio of 1.4. Sulfidogenesis was clearly dependent on the availability of electron donor; but not methanogenesis. The smaller COD removal efficiencies (∼93%) were observed at the higher sulfate (1980mg/L) and organic matter (COD of 7000mg/L) concentrations, with COD/sulfate ratio of 3.5. Under these conditions, the presence of volatile fatty acids in the effluent indicates the occurrence of methanogenesis inhibition probably due to sulfide. The fixed-film HAIB reactor did not present bed clogging throughout the entire long-term operation period, thereby leading the way to new perspectives to use the efficient treatment of sulfate-rich wastewater.

Technological aspects of the production of biodegradable polymers and other chemicals from renewable sources using lactic acid

Lactic acid produced from renewable sources is used for the production of polylactic acid and lactic acid-based biodegradable polymers. However, large-scale production of biodegradable polymers and other large-tonnage lactic acid-based chemical products is limited by the difficulties of production-related waste and low productivity. To overcome these problems, we developed a method of ammonium lactate production from carbohydrates using a membrane bioreactor and semicontinuous cultivation with controlled parameters. During the 130 cycles, the average specific productivity of the biochemical reactor for ammonium lactate was 56 g L−1·h−1, which was 10-fold higher than that obtained using traditional industrial processes. This method of using concentrated biomass in membrane reactors may also be applied in other similar processes of microbial transformation of organic substances. To significantly reduce the waste produced in the form of calcium sulfate, lactic acid derivatives were isolated from the butyl lactate intermediate without calcium sulfate formation. A method for the production of large-volume chemicals such as propylene glycol was also developed through hydrogenation of butyl lactate on a copper oxide–silica catalyst. This highly effective process gave 99% yield and 99% selectivity for propylene glycol formation. Our data on the development and improvement of the production processes of lactic acid and its derivatives pave the way for the development of competitive industrial processes for the production of biodegradable polymers and large-tonnage chemical products based on renewable raw materials.

Impact of microbial physiology and microbial community structure on pharmaceutical fate driven by dissolved oxygen concentration in nitrifying bioreactors

Operation at low dissolved oxygen (DO) concentrations (<1 mg/L) in wastewater treatment could save utilities significantly by reducing aeration energy costs. However, few studies have evaluated the impact of low DO on pharmaceutical biotransformations during treatment. DO concentration can impact pharmaceutical biotransformation rates during wastewater treatment both directly and indirectly: directly by acting as a limiting substrate that slows the activity of the microorganisms involved in biotransformation; and indirectly by shaping the microbial community and selecting for a community that performs pharmaceutical biotransformation faster (or slower). In this study, nitrifying bioreactors were operated at low (∼0.3 mg/L) and high (>4 mg/L) DO concentrations to understand how DO growth conditions impacted microbial community structure. Short-term batch experiments using the biomass from the parent reactors were performed under low and high DO conditions to understand how DO concentration impacts microbial physiology. Although the low DO parent biomass had a lower specific activity with respect to ammonia oxidation than the high DO parent reactor biomass, it had faster biotransformation rates of ibuprofen, sulfamethoxazole, 17α-ethinylestradiol, acetaminophen, and atenolol in high DO batch conditions. This was likely because the low DO reactor had a 2x higher biomass concentration, was enriched for ammonia oxidizers (4x higher concentration), and harbored a more diverse microbial community (3x more unique taxa) as compared to the high DO parent reactor. Overall, the results show that there can be indirect benefits from low DO operation over high DO operation that support pharmaceutical biotransformation during wastewater treatment.

Performance of rotary kiln reactor for the elephant grass pyrolysis

The influence of process conditions (rotary speed/temperature) on the performance of a rotary kiln reactor for non-catalytic pyrolysis of a perennial grass (elephant grass) was investigated. The product yields, the production of non-condensable gases as well as the biochar properties were evaluated. The maximum H2 yield was close to that observed for catalytic pyrolysis processes, while the bio-oil yield was higher than reported for pyrolysis of other biomass in rotary kiln reactors. A H2/CO ratio suitable for Fischer–Tropsch synthesis (FTS) was obtained. The biochars presented an alkaline pH (above 10) and interesting contents of nutrients, as well as low electrical conductivity, indicating a high potential as soil amendment.

The effects of different carriers on removal performance and membrane fouling by HMBR in treating sewage with low carbon-to-nitrogen ratio

A hybrid membrane bioreactor (HMBR) with biological-band carriers (reactor A) and a HMBR with suspended-honeycomb carriers (reactor B) were used for treatment of sewage with low carbon-to-nitrogen ratio (3–5). The pollutant removal performance and membrane fouling in HMBRs was investigated under different hydraulic retention times (HRT) (5h and 9h). The results demonstrated that both HMBRs can be effective for the removal of chemical oxygen demand (COD), NH3-N and total nitrogen (TN). The rate of TN removal in reactor A was higher than that in B. Moreover, it was found reactor A was more advantageous for the degradation of biodegradable organic matter than that of B. The biomass in reactors was characterized by mixed liquor adherent solids (MLAS), particle size distributions, mixed liquor suspended solids (MLSS) and concentration of extracellular polymeric substance (EPS). The results showed that MLAS content and particle size distribution in reactor A were higher than in B, whereas concentrations of MLSS and EPS exhibited the opposite trend. When systems were run under different HRTs, the increased rate of trans-membrane pressure (TMP) in reactor A was slower than that in B. Therefore, reactor A was considered superior to reactor B in pollutant removal and controlling membrane fouling.

Performance of passive aerated immobilized biomass reactor coupled with Fenton process for treatment of landfill leachate

The passive aerated immobilized biomass (PAB) reactor was investigated for the treatment of landfill leachate. Reactor performance was affected by hydraulic retention time (HRT), organic loading rate (OLR), volatile suspended solids to total suspended solids ratio (VSS/TSS) and CODtotal/NH4-N ratio. CODtotal and NH4-N removal efficiency dropped from 55 ± 6 to 33 ± 2% and from 93 ± 8 to 80 ± 11%, when the HRT was decreased from 16 to 4 h, respectively. Ammonia oxidation increased from 69 to 94% at decreasing the VSS/TSS ratio from 0.54 to 0.24, respectively. Fenton pre-treatment substantially improved the removal efficiency of CODtotal (83 ± 4%) and CODsoluble (83 ± 5%). The simple empirical model designed to assess the performance of PAB reactor treating landfill leachate showed good agreement between predicted and experimental parameter values.

Using of Ferrous Chloride in Anaerobic Digestion of a Substrate with High Sulphur Content

Possibilities of anaerobic processing of substrates rich in sulphur were studied. High concentrations of sulphur cause problems when contained in biogas, as well as inhibition by sulphides in anaerobic processes. The impact of ferrous chloride on anaerobic processes, directly dosed to the anaerobic reactor was studied. This sulphur removal method is commonly known, though the objective of our study was to identify problems when it is applied on substrates rich in sulphur. Waste biomass from cystine production was used as substrate, which is produced in large quantities (17000 t/y) by Biotika, a.s. Slovenská Ľupča and requires processing; sulphur content range from 4 up to 5 % in the biomass. Specific biogas production was 0.410 m3/kg COD i.e. 0.737 m3/kg VSS, while 77 % sulphide inhibition occurred after several dose repetitions. Inhibition decreased to 25.4 % during long-term processing of cystine biomass in a mixed anaerobic reactor. Ferrous chloride dosing, however, resulted in high excess sludge generation, lower organic content in the sludge and high concentration of dissolved inorganic salts. These factors may lead to secondary problems in long-term processing of cystine biomass.