Continuous-flow Treatment Research Articles

Multiple strategies for maintaining stable partial nitritation of low-strength ammonia wastewater

Stable production of nitrite is an essential technical challenge for mainstream anaerobic ammonia oxidation (Anammox). Due to difficulties in the stable inhibition of nitrite oxidizing bacteria (NOB) and maintenance of long-term partial nitritation (PN), integrated multiple, rather than a single, controlling strategies were preferred especially in a continuous-flow treatment system. A mathematically model was developed to evaluate effects of integrated multiple-strategies on ammonia oxidizing bacteria (AOB) and NOB. Through experimental study and model simulation, intermittent aeration and low SRT (3.5 d) resulted in unstable nitrite accumulation. Integrated multiple-strategies of intermittent aeration, low SRT (3.5 d) and bioaugmentation achieved nitrite accumulation rate of 81% and NO2−-N/NH4+-N ratio in effluent of 1.29, which was preferable for further anammox process. Meanwhile, the richness and diversity of microbial community increased due to the bioaugmentation. The AOB/NOB ratio increased from 13.8 to 34.1 which facilitated nitrite accumulation. In combination with bioaugmentation, the observed growth rates of AOB and NOB increased from −0.0835 and −0.0282 to 0.0434 and 0.0127 d−1, respectively, which promoted AOB outcompeting NOB in the mixed liquid.

Daily frequency of water changes in flooded pens during initial bullfrog rearing

The flooded pens represent ease of handling when compared to other systems and allow the use of higher stocking densities, which results in an increase in productivity by area. However, information on management in this type of system are scarce in the literature. The objective was to evaluate the effect of the daily frequency of water changes on the performance of bullfrog froglets (Lithobates catesbeianus) reared in flooded pens, for a period of 30 days. A total of 360 froglets with 8.13 ± 0.22 g and 4.85 ± 0.81 cm was randomly distributed in twelve flooded pens (0.48 m2) in a density of 30 animals/ pen. A completely randomized design with four treatments and three replications was used, the pen being the experimental unit. The treatments were the total replacement of the water in the pens performed once, twice and three times a day and a treatment with continuous water flow. The frogs were fed, ad libitum, three times a day. The average survival rate was high (96.75%) and did not differ between treatments. Higher feed intake was observed in the treatment of one and two daily water changes and continuous water flow. The continuous water flow treatment showed a higher percentage of animals over 30 g. The other variables of productive performance were not significant. Total ammonia was lower in the continuous water flow treatment. Therefore, prioritizing well-being, the use of a continuous water flow for the creation of froglets in flooded pens is the most suitable. As flooded pens is the most used system in frogs farming, is important to continue studies on management in flooded pens, especially in relation to the reuse of water resources.

Continuous Flow Treatment Chamber for Liquid Food Processing Through Pulsed Electric Field

In pulsed electric field (PEF) treatment, non-uniform distributions of the electric field and temperature are problematic within a treatment chamber. The helical shape has a favorable feature of flow that facilitates to resolve these issues. This work was performed to determine the optimal design of the helically shaped treatment chamber and its proficiency in the quality and stability of liquid foods. The uniformity of the electric field was evaluated using numerical simulation. The simulations were validated through three different designs of the helical chambers to treat the liquid samples of mango, pineapple, and coconut milk. The consequence of the treatments and the storage time were monitored through physicochemical and microbial analysis of the treated samples. This treatment process causes a temperature rise of less than 10%. The beverages treated inside the helical treatment chamber were stable up to 7 days of storage at ambient storage condition (25 °C) by minimizing quality changes and reducing microbial growth.

Cr(VI) Femoval from Ground Waters by Ferrous Iron Redox-Assisted Coagulation in a Continuous Treatment Unit Comprising a Plug Flow Pipe Reactor and Downflow Sand Filtration

Chromium(VI) (Cr(VI)) is the main chromium species found in groundwater and is considered as a highly toxic and carcinogenic element to humans. In the present study, removal of Cr(VI) by coagulation with ferrous iron is studied in a continuous flow treatment unit comprising pipe flocculation reactors followed by a sand filter. The studied parameters, regarding their effect on the removal of hexavalent chromium, were the ferrous iron dose, the effect of linear velocity, and the effect of the starting Cr(VI) concentration. The experiments have shown that the Cr(VI) removal achieved was very efficient and residual Cr(VI) and total Cr concentration in the treated water was lower than 10 μg/L, provided that the required dose of ferrous iron is provided. In particular, the study demonstrated that the removal of hexavalent chromium, from initial concentration of 50 μg/L and 100 μg/L, was more than 90% with ferrous doses of 1 mg/L and 2 mg/L respectively, applying linear velocity of 8 m/h, at an initial pH value of 7.3. Iron concentration in treated water was very low, far below 200 μg/L, which is the limit for iron in drinking water. This unit comprises a simple treatment option, for applications at the household level, with minimum maintenance requirements capable of removing Cr(VI) to concentrations below 10 μg/L, which might be the future limit for chromium in drinking water.

Feasibility test of autotrophic denitrification of industrial wastewater in sequencing batch and static granular bed reactors.

In order to evaluate the efficacy of using reduced sulfur species in lieu of conventional substrates, a sequencing batch reactor (SBR) was used to develop an autotrophic denitrifying culture which in turn was used to seed a static granular bed reactor (SGBR) for continuous flow treatment. Both bioreactors were able to quickly acclimate to the anoxic environment and achieve stable autotrophic denitrification within several weeks of being placed in operation. The seed for the SBR was obtained from operating basins at the Cedar Rapids plant. MiSeq analysis showed the presence of the autotrophic denitrifier Thiobacillus in the seed from the sulfur oxidation basin; however, Shinella and Sulfurovum became the dominant autotrophic denitrifiers in the SBR. Both the SBR and SGBR achieved excellent nitrate removal (i.e., >95%) with stoichiometric amounts of thiosulfate added to the synthetic influent. The results of this feasibility study suggest that anaerobic granules from the UASB at the plant serve as good seed biomass for autotrophic denitrification when augmented by sulfur oxidation basin and sulfide scrubber biomass, and that reduced sulfur species at the plant (or augmented with an external sulfur source) can serve as electron donors for nearly complete denitrification. PRACTITIONER POINTS: Autotrophic denitrification of industrial wastewater was investigated to evaluate reduced sulfur species as electron donor for nitrogen removal. An autotrophic denitrifying culture was cultivated in an SBR, and continuous autotrophic denitrification was accomplished in an SGBR. No increase in head loss was observed in the SGBR, and it was able to operate without the need for backwashing in more than 200days of operation. Reduced sulfur was demonstrated to be a sufficient electron donor for nearly complete denitrification. MiSeq analysis resolved primary species responsible for autotrophic denitrification in this study.

EFFECT OF NUTRIENT SOLUTION FLOW INTERVAL ON GROWTH AND YIELD OF LETTUCE (Lactuca sativa) GROWN IN HYDROPONICALLY DEEP FLOW TECHNIQUE

Lettuce (Lactuca sativa L.) is one of the vegetables that are commonly cultivated by using hydroponic systems. Some hydroponic systems require high current expenses in particular for the electricity in order to circulate nutrient solution e.g. in the water culture system – deep flow technique (DFT) -. Electricity costs can be reduced by changing from continuous nutrient flow to intermittent nutrient flow. The aim of this research was to investigate the effect of interval nutrient flow on growth and yield of lettuce. The experiment was conducted in Cirebon from February to April 2018. The experiment was arranged by using randomized complete block design with four treatments: (i) continuous nutrient flow (control), intermittent nutrient flow (nutrient flow during (ii) 15 minutes, (iii) 30 minutes, and (iv) 45 minutes). For each intermittent treatment, the nutrient flow was interrupted for 60 minutes. Each treatment was repeated four times. The result showed nutrient flow interval affected to plant height, shoot diameter, and leaf area at 35 days after planting (DAP). Meanwhile, leaves number, root volume, and fresh weight of harvested crops were not significantly different in all nutrient interval treatments. The highest plant height and shoot diameter were detected in the treatment (ii) nutrient flow during 15 minutes and interruption for 60 minutes, the results were not significantly different to the control – continuous flow treatment. It can be concluded the interval nutrient flow can be used as an alternative of the continuous flow of nutrient solution in hydroponically DFT.

Physicochemical properties of apple juice influenced by induced potential difference (induced electric field) during disposable continuous-flow treatment

A disposable continuous-flow system was established by treating apple juice with induced electric field (IEF). Under synchronous alternating magnetic flux, rather than electrodes, the electrical treatment was implemented in multi-series coils consisting of the flowing sample. An activation effect at 50 °C and inactivation effect at 70 °C were observed under IEF. High excitation voltage (900 V) caused a significant decrease in the residual activities (RA). As the flow rate decreased from 87.5 to 17.5 mL/min, RA of PPO and POD were changed without applying IEF indicated shear effect of the pump had an impact on the RAs. At 17.5 mL/min, PPO was inactivated after IEF treatment for 7.6 min. In compared with the control (0 V), the fluid impedance was increased at 70 °C and 80 °C under IEF, whereas it was decreased at 30 °C and 40 °C. IEF had no adverse influence on the color and volatile compounds of apple juice in this system.

Feasibility Test of Autotrophic Denitrification of Industrial Wastewater in Sequencing Batch and Static Granular Bed Reactors

In order to evaluate the efficacy of using reduced sulfur species in lieu of conventional substrates, a sequencing batch reactor (SBR) was used to develop an autotrophic denitrifying culture which in turn was used to seed a static granular bed reactor (SGBR) for continuous flow treatment. Both bioreactors were able to quickly acclimate to the anoxic environment and achieve stable autotrophic denitrification within several weeks of being placed in operation. The seed for the SBR was obtained from operating basins at the Cedar Rapids plant. MiSeq analysis showed the presence of the autotrophic denitrifier Thiobacillus in the seed from the sulfur oxidation basin; however, Shinella and Sulfurovum became the dominant autotrophic denitrifiers in the SBR. Both the SBR and SGBR achieved excellent nitrate removal (i.e., >95%) with stoichiometric amounts of thiosulfate added to the synthetic influent. The results of this feasibility study suggest that anaerobic granules from the UASB at the plant serve as good seed biomass for autotrophic denitrification when augmented by sulfur oxidation basin and sulfide scrubber biomass, and that reduced sulfur species at the plant (or augmented with an external sulfur source) can serve as electron donors for nearly complete denitrification. PRACTITIONER POINTS: Autotrophic denitrification of industrial wastewater was investigated to evaluate reduced sulfur species as electron donor for nitrogen removal. An autotrophic denitrifying culture was cultivated in an SBR, and continuous autotrophic denitrification was accomplished in an SGBR. No increase in head loss was observed in the SGBR, and it was able to operate without the need for backwashing in more than 200 days of operation. Reduced sulfur was demonstrated to be a sufficient electron donor for nearly complete denitrification. MiSeq analysis resolved primary species responsible for autotrophic denitrification in this study.

Simultaneous nitrogen and organics removal using membrane aeration and effluent ultrafiltration in an anaerobic fluidized membrane bioreactor

Dissolved methane and a lack of nutrient removal are two concerns for treatment of wastewater using anaerobic fluidized bed membrane bioreactors (AFMBRs). Membrane aerators were integrated into an AFMBR to form an aeration membrane fluidized bed membrane bioreactor (AeMFMBR) capable of simultaneous removal of organic matter and ammonia without production of dissolved methane. Good effluent quality was obtained with no detectable suspended solids, 93±5% of chemical oxygen demand (COD) removal to 14±11mg/L, and 74±8% of total ammonia (TA) removal to 12±3mg-N/L for domestic wastewater (COD of 193±23mg/L and TA of 49±5mg-N/L) treatment. Nitrate and nitrite concentrations were always low (<1mg-N/L) during continuous flow treatment. Membrane fouling was well controlled by fluidization of the granular activated carbon (GAC) particles (transmembrane pressures maintained <3kPa). Analysis of the microbial communities suggested that nitrogen removal was due to nitrification and denitrification based on the presence of microorganisms associated with these processes.

Toward a Philosophy and Theory of Volumetric Nonthermal Processing.

Nonthermal processes for food preservation have been under intensive investigation for about the past quarter century, with varying degrees of success. We focus this discussion on two volumetrically acting nonthermal processes, high pressure processing (HPP) and pulsed electric fields (PEF), with emphasis on scientific understanding of each, and the research questions that need to be addressed for each to be more successful in the future. We discuss the character or "philosophy" of food preservation, with a question about the nature of the kill step(s), and the sensing challenges that need to be addressed. For HPP, key questions and needs center around whether its nonthermal effectiveness can be increased by increased pressures or pulsing, the theoretical treatment of rates of reaction as influenced by pressure, the assumption of uniform pressure distribution, and the need for (and difficulties involved in) in-situ measurement. For PEF, the questions include the rationale for pulsing, difficulties involved in continuous flow treatment chambers, the difference between electroporation theory and experimental observations, and the difficulties involved in in-situ measurement and monitoring of electric field distribution.

Evaluation of a hybrid ion exchange-catalyst treatment technology for nitrate removal from drinking water

Ion exchange (IX) is the most common approach to treating nitrate-contaminated drinking water sources, but the cost of salt to make regeneration brine, as well as the cost and environmental burden of waste brine disposal, are major disadvantages. A hybrid ion exchange-catalyst treatment system, in which waste brine is catalytically treated for reuse, shows promise for reducing costs and environmental burdens of the conventional IX system. An IX model with separate treatment and regeneration cycles was developed, and ion selectivity coefficients for each cycle were separately calibrated by fitting experimental data. Of note, selectivity coefficients for the regeneration cycle required fitting the second treatment cycle after incomplete resin regeneration. The calibrated and validated model was used to simulate many cycles of treatment and regeneration using the hybrid system. Simulated waste brines and a real brine obtained from a California utility were also evaluated for catalytic nitrate treatment in a packed-bed, flow-through column with 0.5 wt%Pd–0.05 wt%In/activated carbon support (PdIn/AC). Consistent nitrate removal and no apparent catalyst deactivation were observed over 23 d (synthetic brine) and 45 d (real waste brine) of continuous-flow treatment. Ion exchange and catalyst results were used to evaluate treatment of 1 billion gallons of nitrate-contaminated source water at a 0.5 MGD water treatment plant. Switching from a conventional IX system with a two bed volume regeneration to a hybrid system with the same regeneration length and sequencing batch catalytic reactor treatment would save 76% in salt cost. The results suggest the hybrid system has the potential to address the disadvantages of a conventional IX treatment systems.

Continuous flow demulsification of a water-in-toluene emulsion by an alternating electric field

Abstract In this study, the in-flow demulsification of a water-in-toluene emulsion by an alternating electric field was investigated. A fluorocarbon tube, chosen for its flexibility and resistance to toluene, was positioned between copper electrodes attached to a voltage supply and a wave generator. With this design, it was possible to apply a strong electric field of 1000 kV/m as the emulsion was not in direct contact with the electrodes. The demulsification rate increased on increasing the frequency of the alternating electric field up to ∼100 Hz, and a square wave was more effective than a sine wave at low frequencies. Furthermore, the demulsification rate increased on increasing the content of the organic phase and intensity of the electric field. We investigated the effects of an electrolyte dissolved in the aqueous phase, and found that it promoted demulsification in relation to the valence of the cation used. Additionally, demulsification was strongly affected by the ionic strength of the aqueous phase. Our results show that demulsification by the application of an alternating electric field can be very useful in the continuous flow treatment of extraction mixtures in organic synthesis.

Influence of high power ultrasound on Brettanomyces and lactic acid bacteria in wine in continuous flow treatment

The purpose of this study was to investigate the effect of non-thermal technology, a high power ultrasound (HPU) in continuous flow treatment on the reduction in number of Brettanomyces yeasts and lactic acid bacteria (LAB) in wine samples. Yeast cells and lactic acid bacteria were screened for their sensitivity to a high power ultrasound treatment using an ultrasonic processor (400W, 24kHz, 100μm amplitude) at two different wine temperatures (30 and 40°C). High power ultrasound treatment in continuous flow showed satisfactory reduction of Brettanomyces yeasts (89.1–99.7%) and lactic acid bacteria (71.8–99.3%). Sensory properties of wine were impaired. The results indicate a great potential for the application of HPU in continuous flow system for wine processing in terms of lower usage of SO2 and preservatives. More attention is needed to preserve sensorial properties of wine.

English

The possibility of microbial reduction by external pulsed electric field (PEF) offers a new application for pulsed power technology. Applying PEF technology to food pasteurization is a promising non-thermal method. One of such application is prevention of microbial growth, an effect that is based on irrreversible permiabilization of cell membranes. The objective of this study was to increase the shelf life of tomato juice using PEF method. It is reported that the microbes present in tomato juice were inactivated by PEF process using co-axial and co-field continuous treatment chambers. The samples were subjected to different electric field intensities (30 and 50 kVcm-1) with the same flow rate (100 mL min-1) and the same pulse number (150 pulses). After treatment, in both co-axial and co-linear chambers, greater reduction in microbial counts were seen at higher intensity of 50 kVcm-1. The co-axial treatment chamber at 150 pulses was more effective than co-linear treatment chamber (1.16 and 0.77 log reduction). Key words: Pulsed electric field, co-field continuous flow treatment chamber, co-axial continuous flow treatment chamber, tomato juice, microbial growth reduction.

Leaching behavior of Kresoxim-Methyl and Acid Metabolite in normal and sludge amended inceptisol soil

Kresoxim-methyl, a strobilurin fungicide, is a broad spectrum, foliar fungicide. Leaching studies conducted with kresoxim methyl and acid metabolite separately revealed that in column soil >90% of the kresoxim methyl undergo hydrolysis and changed into acid metabolite. Acid metabolite showed more leaching potential than the parent molecule. Residues moved to the lower soil depth with increasing amount of rainfall. Increasing the organic matter content of the soil by sludge amendment (5%) reduced the leaching potential of both the compounds. With the same amount of rainfall, leaching was found to be more under discontinuous flow than continuous flow treatment.

A multi-electrode continuous flow microbial fuel cell with separator electrode assembly design

Scaling up microbial fuel cells (MFCs) requires the development of compact reactors with multiple electrodes. A scalable single chamber MFC (130 mL), with multiple graphite fiber brush anodes and a single air-cathode cathode chamber (27 m2/m3), was designed with a separator electrode assembly (SEA) to minimize electrode spacing. The maximum voltage produced in fed-batch operation was 0.65 V (1,000 Ω) with a textile separator, compared to only 0.18 V with a glass fiber separator due to short-circuiting by anode bristles through this separator with the cathode. The maximum power density was 975 mW/m2, with an overall chemical oxygen demand (COD) removal of >90% and a maximum coulombic efficiency (CE) of 53% (50 Ω resistor). When the reactor was switched to continuous flow operation at a hydraulic retention time (HRT) of 8 h, the cell voltage was 0.21 ± 0.04 V, with a very high CE = 85%. Voltage was reduced to 0.13 ± 0.03 V at a longer HRT = 16 h due to a lower average COD concentration, and the CE (80%) decreased slightly with increased oxygen intrusion into the reactor per amount of COD removed. Total internal resistance was 33 Ω, with a solution resistance of 2 Ω. These results show that the SEA type MFC can produce stable power and a high CE, making it useful for future continuous flow treatment using actual wastewaters.

Ozone application in a modified screw conveyor to treat grain for insect pests, fungal contaminants, and mycotoxins

Recent efforts have focused on improving the application of ozone technology as a pest management tool for stored grain. This study evaluated the efficacy of a modified screw conveyor to treat grain with ozone in a continuous-flow system. The ozone concentration delivered into the screw conveyor was 47,800 ppm and the average retention time for a corn kernel moving through the system was 1.8 min. Under these conditions, 100% mortality of adult red flour beetle ( Tribolium castaneum (Herbst)) and adult maize weevil ( Sitophilus zeamais (Motsch.)) was achieved after three passes through the screw conveyor, which equated to a concentration × time (CT) product value of 258,120 ppm-min. The potential effectiveness of the continuous treatment to reduce mold on the surface of corn kernels was also explored. Aspergillus flavus counts were reduced by 96% in a single pass through the screw conveyor. Three passes through the screw conveyor reduced the mold count by more than 2-log units. Ozone treatment also reduced aflatoxin applied to the grain; however, the reduction was not sufficient enough to be of commercial value. The results of this study provide valuable information for estimating the parameters needed for effectively treating grain in a commercial scale continuous-flow treatment system.

Technical-economical analysis of selected decentralized technologies for municipal wastewater treatment in the city of Rome

Several wastewater treatment technologies were evaluated as alternative systems to the more traditional centralized continuous flow system to serve decentralized areas of the city of Rome (Italy). For instance, the following technologies were selected: (1) Constructed wetlands, (2) Membrane Biological Reactor, (3) Deep Shaft, (4) Sequencing Batch Reactor, and (5) Combined Filtration and UV-disinfection. Such systems were distinguished based on the limits they are potentially capable of accomplishing on the effluent. Consequently, the SBR and DS were grouped together for their capability to comply with the standards for the discharge into surface waters (according to the Italian D.Lgs. 152/06, Table 1, All. 5), whereas the MBR and tertiary system (Filtration+UVc-disinfection) were considered together as they should be able to allow effluent discharge into soil (according to the Italian D.Lgs. 152/06, Table 4, All. 5) and/or reuse (according to the Italian D.M. 185/03). Both groups of technologies were evaluated in comparison with the more common continuous flow treatment sequence consisting of a biological activated sludge tank followed by the secondary settlement, with final chlorination. CWs were studied separately as a solution for decentralized urban areas with limited population. After the analysis of the main technical features, an economical estimate was carried out taking into account the investment, operation and maintenance costs as a function of the plant's capacity. The analysis was based on real data provided by the Company who manages the entire water system of the City of Rome (Acea Ato 2 S.p.A.). A preliminary design of the treatment plants using some of the selected technologies was finally carried out.

Ultrasonic pretreatment of corn slurry for saccharification: A comparison of batch and continuous systems

The effects of ultrasound on corn slurry saccharification yield and particle size distribution was studied in both batch and continuous-flow ultrasonic systems operating at a frequency of 20 kHz. Ground corn slurry (28% w/v) was prepared and sonicated in batches at various amplitudes (192–320 μm peak-to-peak (p–p)) for 20 or 40 s using a catenoidal horn. Continuous flow experiments were conducted by pumping corn slurry at various flow rates (10–28 l/min) through an ultrasonic reactor at constant amplitude of 12 μm p–p. The reactor was equipped with a donut shaped horn. After ultrasonic treatment, commercial alpha- and gluco-amylases (STARGEN TM 001) were added to the samples, and liquefaction and saccharification proceeded for 3 h. The sonicated samples were found to yield 2–3 times more reducing sugars than unsonicated controls. Although the continuous flow treatments released less reducing sugar compared to the batch systems, the continuous flow process was more energy efficient. The reduction of particle size due to sonication was approximately proportional to the dissipated ultrasonic energy regardless of the type of system used. Scanning electron microscopy (SEM) images were also used to observe the disruption of corn particles after sonication. Overall, the study suggests that both batch and continuous ultrasonication enhanced saccharification yields and reduced the particle size of corn slurry. However, due to the large volume involve in full scale processes, an ultrasonic continuous system is recommended.

Continuous ozonation treatment systems as other alternative more efficient grain protection technologies

Previous static bed ozonation scale-up and demonstration trials have proven the use of ozone as an effective technology for grain protection without affecting its end-use quality. Due to the lack of current availability of high capacity ozone producing generators, grain treatment through static bed ozonation systems are limited to be used in metal silos of capacities smaller than 644-t. Also, the trials have shown that treatment time has to be of no less than 4 d during application in order to be effective for pest control. Therefore, more efficient ozonation treatment systems are needed for proper ozone usage for stored product protection. The primary objective of these research studies was to design and test a semi-continuous counter-flow ozonation and a continuous ozonation flow treatment systems in order to ozonate grain at faster rates based on the concentration-time product (CTP) of ozone required to achieve 100% insect mortality and effective mold reduction in grain. The procedure of the counter-flow semi-continuous ozonation system consisted of removing each grain layer inside a metal silo with a tapered unloading auger after each layer reached the desired ozone CTP. The treated grain is subsequently transported to a storage or shipping silo. The continuous ozonation flow system involves applying high ozone concentrations through a modified grain loading screw conveyor where ozone and grain are moving continuously in the same flow direction. The counter-flow semi-continuous ozonation system was successfully tested and proved to be a technically feasible tool for pest control and mold reduction. The continuous ozonation flow system was proved as an effective tool for treating grain during handling while achieving 100% insect mortality, and effective mold reduction. Keywords : Ozonation, Continuous treatment, Grain, Pest control, Molds.