Pilot Reactors Research Articles

Determining the appropriate mixing ratio in a multi-substrate anaerobic digestion of organic solid wastes employing Taguchi method.

The current research proposed a method for optimally combining feed input ratios in order to improve the quantity and quality of daily biogas production through optimizing the variable response level in the Taguchi method. The anaerobic digestion (AD) process of an existing plant in Iran was simulated through a set of two-stage pilot reactors under mesophilic temperature conditions in order to achieve optimal operational performance. Three common substrates (organic fraction of municipal solid wastes, fruit and vegetable wastes, and horse manure) along with two recirculated materials; the post-digestion sludge and the secondary digester slurry, were investigated in 16 experimental runs based on four different pre-surface hypotheses. Comparison of the results of daily biogas energy (J/d/g-VS) in Run#9, to which the actual yield of hydrogen sulfide was minimal in parallel to a methane yield above 100 mL/g-VS, with the result of the optimal run with the ratios provided by the model, showed that the daily biogas energy was improved by 50% comparing to the control Run that had similar conditions to which was being applied in the full-scale existing AD plant.

Rheological evolution of straw-cattle manure (SCM) treated by dry anaerobic digestion in batch and in continuous pilot reactors

Knowledge of rheological evolution of biomass during dry anaerobic digestion (D-AD) is important in the engineering design, modeling, and operation of D-AD reactors. In this work, two methods of rheological analysis, the slump test and the shear-box, were used to measure the evolution of the yield stress, cohesion and friction angle of the straw-cattle manure (SCM) during the D-AD. Firstly, four 60 L batch leach-bed reactors (LBR) were started in parallel and stopped at different stages of the D-AD process on days 0, 10, 21 and 31. Secondly, a 500 L and 2 m length plug flow reactor (PFR) was operated with 40 days of solid retention time and samples were recovered at different positions. The solid degradation during D-AD process was monitored by analysis of the degradation of volatile solids, the fiber content and the Flash BMP. Similar degradation patterns of SCM and rheological evolution were observed in both reactors type. VS content decreased of 10.7% and 10.2% in 30 days in PFR and LBR respectively. VS degradation in both cases was well explained by hemicellulose and cellulose consuming in D-AD process. Considering the rheological analysis, the results showed that D-AD induced a reduction of the yield stress of 28.1 and 24.2% in 30 days in PFR and LBR respectively. Moreover, a similar evolution of cohesion and friction angle value for samples from both reactors was observed. This study demonstrates the close relationship between the state of degradation of the solid biomass and its rheological properties.

Removal of nitrogen from municipal wastewater by denitrification using a sulfur-based carrier: A pilot-scale study

In the present study, to improve nitrate removal rate, a sulfur-based carrier was applied for autotrophic denitrification, and the removal rate was evaluated for advanced wastewater treatment without adding any external organic carbon source. Based on the results, an increased PAC concentration affected the removal efficiency of NO3−-N, and the optimal concentration of PAC was at 15 wt%. During the 60 d operation of a pilot process with a capacity of 1 m3/d, the removal of T-N was 81.2% and 50.2% in reactors with and without sulfur-based carrier, respectively. The removal efficiency of NO3−-N exhibited a similar trend to that of T-N. According to the results, the removal of T-N and NO3−-N was noticeably enhanced to approximately 30% by adding a sulfur-based carrier to the A2O pilot system. In addition, microbial community in both reactors was dominated by Thiobacillus, which is an autotrophic microorganism, displaying a dominant denitrification status. The present study compared the relative efficiencies of nitrate removal in A2O pilot reactors with and without sulfur-based carriers for its successful application in real-scale autotrophic denitrification.

Теплотехнические характеристики процесса пиролиза отработанных шин

A significant annual growth in the number of spent car tires creates a serious environmental problem and calls for the need to continue searching for efficient resource-saving methods of their recycling. There is a growing number of efforts aimed at studying waste tire thermochemical conversion processes, including their pyrolysis to obtain valuable products, including a solid fraction (coke residue), liquid hydrocarbon fraction (pyrolysis oil), and noncondensable gaseous fraction (pyrolysis gas). Commercial and pilot pyrolysis plants and reactors are reviewed. A rotating drum reactor, shaft and screw reactors are the most promising solutions for implementing a continuous process. The development of new resource-saving solutions for the pyrolysis of waste tire requires knowledge of the thermal characteristics of this process, including information on the material and heat flows in the pyrolysis reactor. The composition and thermal properties of waste tire, as well as specific outputs, composition and fuel properties of pyrolysis product material flows, including pyrolysis gas, pyrolysis oil and coke residue, are presented. Information on the pyrolysis plant or reactor heat balance structure is either absent or incomplete. Based on the data available in the literature, the heat balance of a commercial pyrolysis plant equipped with screw reactors characterized by a specific thermal destruction heat of 0.640 MJ/(kg of tires) is drawn up and studied. The numerical analysis results correlate with the data published for the commercial-grade plant. Information on the pyrolysis chamber heat balance structure is correct enough for use in engineering practice. It has been found that the specific heat consumption for the pyrolysis process is 2.269 MJ/(kg of tires). This value can be used in numerically analyzing pyrolysis plants equipped with other designs of pyrolysis reactors.

Development of a green innovative semi-industrial scale pilot combined microwave heating and centrifugal force to extract essential oils and phenolic compounds from orange peels

A new process for extraction of essential oils from orange peels (Citrus sinensis L.) using microwave and centrifugal (MW/C) force was studied. MW/C is a combination of microwave heating to explode the internal cells of biological material, and centrifugation to intensify diffusion, collection and separation of compounds of interest. MW/C is performed at atmospheric pressure with an injection of water vapor. A detailed study concerning optimization of different operating parameters like microwave power density and centrifugation was performed. MW/C has been compared to the hydrodistillation method. In addition of essential oils collection, in the aqueous phase several phenolic compounds can be obtained and valorized. Influence of the two main parameters was discussed first on essential oils and, in second part, on phenolic compounds recovery. The new combined MW/C process provided reduction in the extraction time compared to hydrodistillation method, with an advantage to collect in a same experiment volatile and nonvolatile compounds with high quality. Industrial relevanceThis work was carried out thanks to the investment of IFTS France, an international technical center worldwide known in the field of solid-fluid separations. Considering the huge amount of plant extracts this new combined system using microwave and centrifugal (MW/C) force may be suitable for scaling up. The results of this investigation on pilot reactors pave the way for the design of an industrial device.

Methotrexate Degradation by UV-C and UV-C/TiO2 Pro-cesses with and without H2O2 Addition on Pilot Reactors

Methotrexate (MTX) is an anti-cancer drug that can be excreted up to 90% after administration due to its low biodegradability. Advanced Oxidation Processes (AOPs) are a feasible alternative for the elimination of MTX in the environment. In this research, AOPs were performed in specialized patented reactors (UBE Photocatalytic systems and BrightWater Titanium Advanced Oxidation Process) under experimental pilot conditions. Photolysis and heterogeneous photocatalysis (UV and UV/TiO2) experiments were performed with and without addition of H2O2 and at different initial pHs. Best degradation percentage was achieved by photolysis when initial pH was 3.5 and added H2O2 was 3 mM, reaching a MTX degradation of 82% after 120 min of reaction. HPLC-MS analysis of the resulting samples showed four possible byproducts of MTX degradation, which presented a higher ecotoxicity than the starting compound.

Toxicity of leachates from pilot reactors simulating a landfill with different concentrations of AgNP

ABSTRACT This work’s objective was to verify the leachates toxicity from pilot reactors (PR) simulating a landfill containing different concentrations of silver nanoparticles (AgNP). Acute toxicity tests (48 h) with Daphnia magna were carried out in leachates containing 50, 150 and 450 mg AgNP.kg-1, in addition to a blank for control. Toxicity tests with the pure solution of silver nanoparticle and leachates resulted by the reactors were performed. The acute toxicity tests performed with D. magna confirmed the toxicity of the leachates, as well as confirmed that the silver nanoparticles are toxic, presenting EC50 (48 h) of 0.63 µg.L-1 of pure nanoparticle and ranging from 1.52 to 3.37% for the leachates. Overall, the results from the present study indicate that exposures of aquatic invertebrates to silver nanoparticles could have important ecological effects on lower trophic levels in aquatic ecosystems. The results may contribute to a better understanding of the quality of municipal solid waste (MSW) landfill leachates, with reference to nanoparticle interference and consequent treatment efficiency.

SiO2/TiO2 Composite Coating on Light Substrates for Photocatalytic Decontamination of Water

In this study, we describe synthesis and characterization of a floating photocatalyst for water treatment consisting of a light substrate coated by SiO2/TiO2 composite. Three supports of natural origin were used: natural cork, expanded clay (Liapor), and volcanic porous glass (Sorbix). The photoactivity of the coated supports was tested in a laboratory photoreactor, with Liapor being the most photoactive support with good mechanical stability. The corresponding rate constant for the degradation of a model pollutant, 4-chlorophenol, was 7.8 × 10−5 s−1. Detail characterization of the coated Liapor was obtained by XRF, SEM/EDX, and UV-Vis diffuse reflectance spectroscopy, and surface area measurements. Outdoor experiments were carried out with calcined Liapor and oxalic acid or methylene blue under sunlight on pilot reactors in the Czech Republic and Vietnam. We demonstrated satisfactory photocatalytic activity, long-term stability, and reusability of the new floating photocatalyst. The photoefficiency to mineralize oxalic acid in water under sunlight was estimated as 6.7% under the applied conditions.

Understanding fungal potential in the mitigation of contaminated areas in the Czech Republic: tolerance, biotransformation of hexachlorocyclohexane (HCH) and oxidative stress analysis.

The study of the soil microbial community represents an important step in better understanding the environmental context. Therefore, biological characterisation and physicochemical integration are keys when defining contaminated sites. Fungi play a fundamental role in the soil, by providing and supporting ecological services for ecosystems and human wellbeing. In this research, 52 soil fungal taxa were isolated from in situ pilot reactors installed to a contaminated site in Czech Republic with a high concentration of hexachlorocyclohexane (HCH). Among the identified isolates, 12 strains were selected to evaluate their tolerance to different isomers of HCH by using specific indices (Rt:Rc; T.I.) and to test their potential in xenobiotic biotransformation. Most of the selected taxa was not significantly affected by exposure to HCH, underlining the elevated tolerance of all the tested fungal taxa, and different metabolic intermediates of HCH dechlorination were observed. The oxidative stress responses to HCH for two selected species, Penicillium simplicissimum and Trichoderma harzianum, were investigated in order to explore their toxic responses and to evaluate their potential functioning in bioremediation of contaminated environments. This research suggests that the isolated fungal species may provide opportunities for new eco-friendly, integrated and cost-effective solutions for environmental management and remediation, considering their efficient adaptation to stressful conditions.

Continuous-flow aerobic granulation in plug-flow bioreactors fed with real domestic wastewater

This pilot study was designed to explore the feasibility of achieving successful aerobic granulation in continuous flow infrastructure like that existing in modern wastewater treatment plants (WWTPs). Results demonstrated that aerobic granulation of activated sludge can be achieved in plug-flow reactors (PFRs) fed with primary effluent from a domestic WWTP with seasonal temperature variation between 10 and 22.5 °C. It took about 90 days during the reactor startup to reach a state of sustained aerobic granulation. The characteristics of aerobic granules formed were comparable to those measured in sequential batch reactors (SBRs). The feast-to-famine concentration profiles measured in the plug-flow pilot reactors were found to be in line with those present in the full-scale treatment trains, lending support to the feasibility of converting existing infrastructure to continuous flow aerobic granulation systems. A selection pressure based on settling velocity (Vs) was applied in a Vs selector to retain bioparticles with Vs greater than ~9–9.75 m h−1. It was theorized that an external Vs selection pressure would be necessary but would not be the sole condition sufficient to drive aerobic granulation. The alternating feast-to-famine internal selection provided by the PFRs is also believed to be a required condition to transform biomass from flocs toward dense and compact aerobic granules. While the pilot-scale Plug-flow Aerobic Granulation (PAG) reactor achieved similar COD and NH3 removal efficiencies as the full-scale WWTP treatment train, its effluent from Vs selector contained an average of 138 mg L−1 total suspended solids (TSS) as a result of the biomass ‘wash-out” by the Vs selection pressure. Pilot results suggest a second clarifier for polishing, in addition to the Vs selector, may be needed in a full-scale application of the technique unless other downstream processes (flocculation, sedimentation, filtration) are provided to reach final water quality goals.

Design and optimization of an electrocoagulation reactor for fluoride remediation in underground water sources for human consumption

Fluoride remediation in underground waters of volcanic origin was performed at laboratory scale using an electrocoagulation (EC) technique. The natural waters from certain volcanic springs on the island of Tenerife (Canary Islands, Spain) contain average fluoride concentrations in excess of 7 mg/L. Thus, it is necessary to treat the water for fluoride mitigation below the maximum acceptable concentration of 1.5 mg/L according to Spanish regulations for drinking water. The design and optimization of a sustainable process was accomplished using a progressive scale-up procedure involving three pilot reactors with different configurations and effective working volumes. A bipolar electrode cell design using aluminum electrodes was used in all cases. The good performance of the process was confirmed by reducing the fluoride concentration from 7.35 to 1.4 mg/L. The following optimized operating conditions were determined for a continuous flow cell system: current density, 10 mA/cm2; residence time, 10 min; and, half-period of polarity reversal, 1 min. Furthermore, the kinetics of the remediation process can be fitted using the Variable Order Kinetic (VOK) model, with a power relationship between fluoride concentration and residence time in the EC reactor.

PAC dosing to an MBBR – Effects on adsorption of micropollutants, nitrification and microbial community

Two nitrifying MBBR reactors were operated in parallel, one with PAC dosing and one without, to determine the effects of PAC dosing on nitrification and micropollutant adsorption in municipal wastewater. The removal of micropollutants was evaluated for several doses of PAC and batch experiments were performed to measure adsorption kinetics and nitrification rates. The influence of PAC on the nitrifying microbial community was examined by high-throughput amplicon sequencing. Long-term operation of the pilot reactors showed that nitrification could be maintained while supplying PAC at increasing doses, as confirmed by high nitrification rates and significant abundance of nitrifying bacteria. The adsorption of organic micropollutants could be controlled by the PAC dose, and increased dosing resulted in corresponding improvements in removal efficiency. Biomass, suspended or attached to carriers, did not interfere with the adsorption of organic micropollutants. Freundlich isotherms obtained from the batch experiments were used to predict removal of organic micropollutants in the pilot reactors, suggesting that batch adsorption experiments can be used to predict micropollutant removal on a full scale. Collectively, the results show that nitrification and adsorption of organic micropollutants can be performed simultaneously in an MBBR.

Aeration of pig slurry affects ammonia and greenhouse gases emissions

Manure management is considered to be a main key for mitigating gas emissions from livestock buildings. Since there are a number of limitations that make it difficult to identify these conditions in farm-scale experiments, these experiments should be conducted on a laboratory scale. Therefore, the aim of this study was to develop pilot reactors for simulating the operation conditions to be used later in a farm-scale experiment. The developed reactors were made from polyvinylchloride with 1.5 m height and 0.16 m diameter to be filled with 0.19 L slurry. The generated concentrations of NH3, N2O and CH4 from the slurry were continuously analysed at 800 mL min−1 air flow rate using three different sampling methods. The concentration gradient was also analysed within gas chamber height above the slurry. No differences were apparent neither between the various sampling methods nor concentrations gradient in the gas chamber. Acid pilot reactor was developed to determine the required acid concentration and quantity. Influences of pH slurry and air flow rates on gases concentrations were investigated. At 0.32 $${\text{m}}_{\text{air}}^{3} \;{\text{m}}_{\text{slurry}}^{ - 3} \;{\text{h}}^{ - 1}$$ flow rate, the reproducible value of the emissions was minimized. The emissions of NH3, N2O and CH4 were 3.2, 2.3 and 38 $${\text{mg}}\;{\text{m}}_{\text{slurry}}^{ - 3} \;{\text{h}}^{ - 1}$$ , respectively. In order to achieve minimum gas emissions under aerobic conditions, slurry pH should be kept in the neutral range. A comparison of gas emissions under aerobic and anaerobic conditions was conducted. Approximately 70% less NH3 and 130% more N2O were produced under aerobic than with anaerobic conditions.

A small pilot reactor containing active MgTi–based hydrides at low operational temperatures

This study was investigated to utilize innovatively oil-free diaphragm pump to forcibly desorb the hydrogen from the small pilot MgH2–TiH2 based hydride reactor below the theoretical temperature of 278 °C. Active MgH2-0.1TiH2 composites were prepared using ball milling. Their hydrogenation performances at 25–300 °C were measured under a constant H2 flow mode using a modified Sieverts apparatus. The dehydrogenation rates at 250–350 °C with or without diaphragm pump were investigated to examine whether the pilot reactors could be integrated with a proton exchange membrane fuel cell (PEMFC) for power generation. At a H2 flow rate of 25 ml min−1 g−1, the reactors exhibited excellent hydrogenation, achieving gravimetric hydrogen storage capacities of 2.9–5.2 wt% (excluding the weight of the reactors) at 25–300 °C after 22 min. All hydrided MgTi–based reactors could be dehydrogenated at 250 °C at an average rate of 5 ml min−1 g−1 under vacuum. This is the first demonstration of Mg-based reactors that were hydrogenated at 100 °C and dehydrogenated at 250 °C to power a small PEMFC, yielding a measured conversion efficiency of 18%.

Tailoring the Structure and Morphology of Low-Molecular-Weight Cellulose Produced during Supercritical Water Hydrolysis

This paper discusses the influence of reactor design and initial consistency when partially hydrolyzing microcrystalline cellulose (MCC) in supercritical water. Experiments conducted on two pilot reactors located in Finland and in Spain showed that stopping the reaction using depressurization instead of quenching, combined with a sufficiently high MCC consistency, led to significant change in reaction kinetics. A complete particle size reduction was achieved after 50 ms only due to additional shear-induced degradation, with a low-molecular-weight product yield above 50 wt % and an average DP of 25. In addition, gradually increasing the MCC consistency triggered precipitation under higher apparent temperature, which affected both the morphology and structure of the product. A range of particles from ribbon-like cellulose II to shish-kebab structures to lamellar cellulose IVII crystals was obtained. Furthermore, heat requirements as low as 66 kJ·g–1 of product confirm the high potential and versatility of t...

Pilot Scale Cavitational Reactors and Other Enabling Technologies to Design the Industrial Recovery of Polyphenols from Agro-Food By-Products, a Technical and Economical Overview.

We herein provide an overview of the most recent multidisciplinary process advances that have occurred in the food industry as a result of changes in consumer lifestyle and expectations. The demand for fresher and more natural foods is driving the development of new technologies that may efficiently operate at room temperature. Moreover, the huge amount of material discarded by the agro-food production chain lays down a significant challenge for emerging technologies that can provide new opportunities by recovering valuable by-products and creating new applications. Aiming to design industrial processes, there is a need for pilot scale plants such as the ‘green technologies development platform’, which was established by the authors. The platform is made up of a series of multifunctional laboratories that are equipped with non-conventional pilot reactors, developed in direct collaboration with partner companies, in order to bridge the enormous gap between academia and industry via the large-scale exploitation of relevant research achievements. Selected key, enabling technologies for process intensification make this scale-up feasible. We make use of two selected examples, the grape and olive production chains, to show how cavitational reactors, which are based on high-intensity ultrasound and rotational hydrodynamic units, can assist food processing and the sustainable recovery of waste, to produce valuable nutraceuticals as well as colouring and food–beverage additives.

Comparative life cycle assessment of real pilot reactors for microalgae cultivation in different seasons

Microalgae are promising natural resources for biofuels, chemical, food and feed products. Besides their economic potential, the environmental sustainability must be examined. Cultivation has a significant environmental impact that depends on reactor selection and operating conditions. To identify the main environmental bottlenecks for scale-up to industrial facilities this study provides a comparative life cycle assessment (LCA) of open raceway ponds and tubular photobioreactors at pilot scale. The results are based on experimental data from real pilot plants operated in summer, fall and winter at AlgaePARC (Wageningen, The Netherlands). The energy consumption for temperature regulation presented the highest environmental burden. The production of nutrients affected some categories. Despite limited differences compared to the vertical system, the horizontal PBR was found the most efficient in terms of productivity and environmental impact. The ORP was, given the Dutch climatic conditions, only feasible under summer operation. The results highlight the relevance of LCA as a tool for decision-making in process design. Weather conditions and availability of sources for temperature regulation were identified as essential factors for the selection of geographic locations and for microalgal cultivation systems based on environmental criteria. Simulation of large-scale reactors with optimized temperature regulation systems lead to environmental improvements and energy demand reductions ranging from 17% up to 90% for systems operated in favorable summer conditions.

Nutrient removal and biodiesel feedstock potential of green alga UHCC00027 grown in municipal wastewater under Nordic conditions

Integrating cultivation with wastewater treatment improves the economics of microalgal based biofuel production and allows for the sustainable reuse of nitrogen (N) and phosphorus (P) from waste streams. Batch-cultivation of a locally isolated green microalga, UHCC00027, and an indigenous algal-bacterial consortium was undertaken on screened municipal wastewater in 24L pilot reactors. Evaluations of growth and of N and P removal were performed at different Chemical Oxygen Demand (COD) levels and N:P ratios. Lipid accumulation and fatty acid composition of the resulting biomass were also examined. Unique to the present study was the evaluation of wastewater treatment performance under cold temperatures (7–13°C) typical of a Nordic climate. While temperature exerted little influence on heterotrophic COD removal, vigorous (temperature dependent) growth of microalgae was important in the efficient removal of N and P, with the N:P ratio playing a central role. The studied cultivation regime and organisms achieved regulatory N and P removal levels with a hydraulic retention time (HRT) of 12days. However, biodiesel properties of the resulting biomass did not meet international standards due to a high proportion of polyunsaturated fatty acids. Possible workarounds for simultaneously increasing nutrient removal efficiency, biomass productivity, and improving biomass suitability for biodiesel under a Nordic climate are discussed.

Circular economy in drinking water treatment: reuse of ground pellets as seeding material in the pellet softening process.

Calcium carbonate pellets are produced as a by-product in the pellet softening process. In the Netherlands, these pellets are applied as a raw material in several industrial and agricultural processes. The sand grain inside the pellet hinders the application in some high-potential market segments such as paper and glass. Substitution of the sand grain with a calcite grain (100% calcium carbonate) is in principle possible, and could significantly improve the pellet quality. In this study, the grinding and sieving of pellets, and the subsequent reuse as seeding material in pellet softening were tested with two pilot reactors in parallel. In one reactor, garnet sand was used as seeding material, in the other ground calcite. Garnet sand and ground calcite performed equally well. An economic comparison and a life-cycle assessment were made as well. The results show that the reuse of ground calcite as seeding material in pellet softening is technologically possible, reduces the operational costs by €38,000 (1%) and reduces the environmental impact by 5%. Therefore, at the drinking water facility, Weesperkarspel of Waternet, the transition from garnet sand to ground calcite will be made at full scale, based on this pilot plant research.

The headspace of microaerobic reactors: Sulphide-oxidising population and the impact of cleaning on the efficiency of biogas desulphurisation

O2-limiting/microaerobic conditions were applied in order to control the H2S content of biogas. The S(0)-rich deposits found all over the headspace of two pilot reactors (R1 and R2) as a result of operating under such conditions for 7 and 15 months (respectively) were sampled and removed. After restarting micro-oxygenation, H2S-free biogas was rapidly obtained, and the O2 demand of R2 decreased. This highlighted the need for a cleaning interval of less than 14 months in order to minimise the micro-oxygenation cost. The H2S removed from R2 after approximately 1 month was recovered from its headspace as S(0), thus indicating that the biogas desulphurisation did not take place at the liquid interface. Denaturing gradient gel electrophoresis indicated that the composition, species richness and size of the sulphide-oxidising bacteria population depended on the location, and, more specifically, moisture availability, and indicated increasing species richness over time. Additionally, a possible succession was estimated.