M.S. - Bioengineering

Permanent URI for this collectionhttps://hdl.handle.net/10125/1918

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Design, Simulation And Fabrication Of A Cooler And Controller Facilitating Study Of Magnetic Field Effects On Nucleation In Super Cooled Bulk Water
(University of Hawaii at Manoa, 2020) Francis, Sean; Jun, Soojin; Biological Engineering
In this paper the effects of magnetic fields on supercooled water were investigated for application to a food supercooling storage technology that uses magnetic fields. Current cold storage technologies were reviewed and compared to supercooled storage, highlighting the latter’s longer storage periods without changing food texture. Literature on supercooled water was also reviewed, featuring crossover and relaxation phenomena definitions used in waters possible “liquid-liquid” critical point. Using equations from a previous Monte Carlo study, a correlation between magnetic fields and waters temperature was proposed, showing the magnetic moment between two water molecules in a given magnetic field will decrease with temperature. Furthermore, it was shown that the magnetic moment interaction between water molecules and a 0.6 T magnetic fields imparted ~-2.3*〖10〗^(-5) J/mol energies at -10°C. With this model as a guideline, a cooling device (Supercooler 2) and controller were created to investigate supercooled waters interaction with magnetic fields. Energy balance calculations were used to define hardware specifications before creating a CAD model. Computational fluid dynamic (CFD) analysis on the model showed thermal gradients were minimized when simultaneously drawing heat from the top and bottom of the sample, validating this design feature. The main chassis and custom designed integral components were 3D printed from the CAD and assembled with a GMW 3470 electromagnet to create Supercooler 2 (Appendix F). The Supercooler 2 performance validation testing showed the sample gradient was 0.6°C when cooled bi-directionally and 1.19°C unidirectionally. Further analysis fitted a linear model to sample cooling rates where R^2=0.995 could be obtained with 95% prediction interval=±0.33 °C for 5 repeated replicates, demonstrating the linear temperature control accuracy and precision. A preliminary study using 20 samples with pulsed magnetic fields from 1-100 Hz and 10-600 mT had a normally distributed nucleation temperature with mean= -7.39 and standard deviation=0.307°C. Linear regression models were fit to the results, showing positive correlation between increasing frequencies and supercooling magnitude. Negative correlation was shown between increasing field strength and supercooling magnitude. The independent variables, magnetic frequency and magnitude, were changed simultaneously and thus correlation with supercooling magnitude was ambiguous. This experimental method saved time and provided background data. Furthermore, outliers were discovered and the data provided by this study highlighted a group treated with 70 mT at 20 Hz. This group’s nucleation temperatures were 2.11 standard deviations away from the mean, while the average for the remaining dataset was 0.739, and therefore, it is suggested that the group be investigated for future studies. The subsequent High Field Study improved upon critical experimental methods and process controls. This study focused on experimental groups treated with 600 mT 1 Hz fields and Control groups with no treatment. In the midst of the High Field Study, the PID process variable location was changed to improve smoothness of the sample temperature cooling profile. The result was a separation of groups; two Control groups and two Experimental groups. All groups were found to have the same cooling rates and steady state temperatures. This was shown with 95% prediction intervals=±0.68°C and ±0.82°C for steady state and linear cooling regimes, respectively. This included 16 Control groups (no magnetic field treatment) and 13 Experimental groups treated with 600 mT 1 Hz fields. Experimental groups were 1.5 to 2.9 times more likely to have a nucleation event than Control groups. The temperature profiles were statistically the same between all groups, therefore, the only remaining variable was the difference in treatment. Therefore, the Experimental groups had an increased nucleation probability compared to the control group because of the 600 mT 1 Hz treatment.
Design, Fabrication, and Validation of a Microcontroller Based Supercooling Control Unit for Use in Food Preservation
(University of Hawaii at Manoa, 2017-12) Hoptowit, Raymond A.; Biological Engineering
Freezing is the most widely used food preservation technique in the commercial and domestic market, however the freezing process causes irreversible damages to foods as ice nucleation occurs. New emerging technologies attempt to prevent these damages from occurring by delaying ice formation within foods while maintaining internal sub-zero temperatures (i.e., Supercooling). Investigations into the simultaneous application of pulsating electric fields (PEF) and oscillating magnetic fields (OMF) during the freezing process for extension of the supercooled state within foods have been conducted. In such studies it is common to use numerous electrical equipment and instruments to precisely measure and regulate the power applied to the test food during the supercooling process. As a result, these studies have proven to be quite expensive. In an effort to reduce costs, improve portability, and simplify the data collection process a supercooling control unit was developed to replace all major equipment related to supercooling research conducted at the University of Hawai‘i at Mānoa (Hawaii, USA). The control unit regulates and monitors all power within the magnetic and electric field generation systems. A separate thermocouple based temperature measurement system allows for monitoring of any temperatures associated with the test food sample or ambient environments. Data logging is accomplished either through on-board SD™ card or through USB port to external PC. The supercooling control unit offers a total uncertainty of ±0.7˚C for temperature measurements, ±1.71% of measurements for the PEF current, ±1.67% of measurements for PEF voltage, ±2.88% of measurements for OMF current, and ±1.91% of measurements for OMF voltage. Supercooling experiments conducted with the newly developed control unit have shown agreeable measurements with lab grade electrical equipment. 180g top round beef steak (London broil) was successfully supercooled at -4˚C for a validation period of 7 days, various food quality assessments conducted on the beef showed comparable results with data from previous supercooling studies. The control unit provides a seamless data collection process, while maintaining an adequate level of precision and accuracy within collected data. The newly developed device cuts costs, improved portability, and offers a scale-able platform upon which additional functionality can be implemented.
Protein-Rich Fungal Biomass Cultivation on Agro-Industrial Wastes/Residues for Aquaculture Feed Production with Simultaneous Organic Removal
(University of Hawaii at Manoa, 2017-12) Batsaikhan, Misheel; Biological Engineering
Global aquaculture industry faces an ever increasing challenges of acquiring feed that is cost efficient yet environmentally sustainable. Single cell protein (SCP) from the edible fungus R.oligosporus has high potential as aquaculture feed as it is nonpathogenic to humans and has high essential amino acid and fatty acid content for fish feed. Additionally, to minimize cost and promote sustainable development, fungal protein can be cultivated on low-cost wastes/residues, preferably from agricultural industries which are high in organics and nutrients. In this research, fungal biomass was investigated for its ability to grow on variety of agro-industrial wastes/residues. Sugarcane molasses, unmarketable papaya juice, and sugarcane vinasse were examined for their potential as substrates. Efficiency of organics removal, quantified as soluble chemical oxygen demand (sCOD) was also examined to determine feasibility of the process as a bioremediation technology. Small scale optimization studies showed that the fungus can successfully be cultivated on all three of the agro-industrial wastes/residues. Molasses, however, yielded the highest specific fungal biomass of 0.41 ± 0.02 (g biomass/g sCOD removed) at COD concentration of 50 g/L, and pH of 5.0. Both molasses and vinasse achieved fungal pellet growth, while papaya juice only supported free mycelial growth. Sugarcane molasses was selected for the bench-scale studies to further demonstrate the feasibility of the bioremediation process. Fungal fermentation was conducted in two 2.5-L working volume bubble column reactors. Maximum fungal biomass yield of 4 grams of dry biomass per liter of molasses was achieved after 48 hours of cultivation. Organics removal of 56 ± 4.23 % (quantified as % sCOD removed) as well as significant solids and nutrients removal were also obtained. However, bacterial contamination was detected beginning at 16 hours post spore inoculation, and may have assisted the organics and nutrient removal. Molasses-derived fungal biomass had a protein content (38%), essential fatty acid profile and in vitro protein digestibility (~80%) comparable to that of commercial fish feed. Importantly, lysine, a limiting amino acid in fish feed, was in high amount (8.6%).
In situ crystallization of native poly(3-hydroxybutyrate) granules in varying environmental conditions
(University of Hawaii at Manoa, 2010-12) Porter, Michael Martin
Poly(3-hydroxybutyrate) (PHB) is a microbial biopolyester that can be produced from renewable feedstocks as an eco-friendly bioplastic. PHB in vivo exists as amorphous, intracellular granules that contain a small amount of water and are surrounded by a membrane of lipids and proteins. The native granules undergo varying degrees of crystallization when subjected to changes in environment such as dehydration, temperature, pH, and other mild conditions. For the first time, the in situ crystallization of native PHB granules was monitored via ATR-FTIR. Empirical models describing the crystallization of PHB granules in different environments were developed from Avrami's equation. The extent of granule crystallization is governed by granule size, number of nucleation points, and spherulitic geometry. The primary stabilizing factors of amorphous PHB granules are water, membrane lipids and proteins. Removing any of these factors may induce partial crystallization of PHB, which toughens the granules against extensive molecule degradation and granule aggregation.
Evaluation of a microwire sensor functionalized for rapid detection of escherichia coli cells from liquid foods
(University of Hawaii at Manoa, 2011-12) Lu, Lin
Nowadays, outbreaks of foodborne illness linked to pathogenic bacteria such as Escherichia coli have attracted increasing public attention. Traditional culture-based methods for pathogens identification are time-consuming and labor-intensive, raising the need for fast and sensitive detection techniques. Rapid detection method for E. coli performed by a functionalized microwire sensor was developed and evaluated in this work. A gold-tungsten microwire with a diameter of 25 μm was immobilized with anti-E. coli-antibodies on the surface and used to capture E. coli bacterial cells from cells suspension with dielectrophoretic force generated by an alternating current (AC) electric field at 20 Vpp and 3 MHz. Both fluorescence microscopy and electrochemical techniques were employed to see the amount of cells captured on the wire. Field emission scanning electron microscopy was used to visualize the cells. The detection limit was found to be about 5 CFU/ml with only target bacterial cells captured on the wire. The developed sensor demonstrated relative high sensitivity and specificity with fast detection rate, which shows a strong potential for the application in food industry.
Pulsed field electroflotation for harvesting microalgae
(University of Hawaii at Manoa, 2014-05) Koelsch, Kyle Malone
Microalgae are used in a number of commercial applications including biofuel production, nutraceuticals, and as feedstock for aquaculture. Typical methods for harvesting microalgae like centrifugation, microfiltration, and foam fractionation are extremely energy intensive. Reducing the energy input for harvesting microalgae would improve the overall energy balance for algae based biofuels and benefit any industry where algae is required. One method for harvesting microalgae is electrolytic flotation (electroflotation). This is simply using electrolysis-generated bubbles to float particles out of suspension and to the surface. The primary objective of this research project is to examine the effects that electrical waveform characteristics have on bubble size, gas generation efficiency, biomass separation, and lipid separation of Chlorella sp. from a marine media. Sets of 23 factorial tests were performed on a coplanar interdigitated electrode array. The waveform variables reviewed included applied potential, duty cycle, and frequency. The smallest mean bubble diameter (30.1 μm) occurred at 3V, 20%, 25 Hz. The smallest median bubble diameter (25.0 μm) occurred at 3 V, 10%, 25 Hz. The highest observed gas generation efficiency (1.69x10-6 (mol J-1)) occurred at 3 V DC. The highest observed biomass recovery (6.8%) occurred at 6 V, 20%, 25 Hz. Lipid recovery analysis was attempted as well but high variability in results rendered it inconclusive.
Yeast from papaya processing wastes as aquaculture feed supplement
(University of Hawaii at Manoa, 2007) Kang, Hsu-Ya
The Pacific Island is facing the challenge of short in cost-effective aquafeed. The protein source is the most costly ingredient in feed supplements. Yeast is enriched with protein and has been reported to be able to enhance shrimp's immune system, survival rate and average body weight. Hawaii produces million tons of fruit and food by-products each year which may have the potential to be upgraded into protein enriched value-added products. This study plans to develop a bioprocess procedure to convert fruit processing wastes into yeast biomass, to establish design and operational criteria for yeast production in batch and/or continuous/semi-continuous flow system, to evaluate the nutrient potential of the bioprocessed product as shrimp feed and the cost of the proposed production system. Papaya processing waste collected from a food company in Honolulu was used for yeast growth (S. cerevisiae) in a 14-L fermenter mixing at 200 rpm under room temperature (22±2°C). PH, oxidation reduction potential (ORP) and dissolved oxygen (DO) were monitored with the change of soluble chemical oxygen demand (SCOD) removal and suspended solids increase in the growth medium to determine the required reaction time for maximum desirable product formation. An initial SCOD concentration ranged from 12,000 to 25,000 mg/l with 8-12h aeration was found for optimal and economical operation in the batch production system. It was able to remove more than 70% SCOD and produce 40-45% crude protein in suspended solid. Preliminary work of continuous/semi-continuous flow operation, shrimp (L. vannamei) feed trail and economic analysis on the batch production system indicated the successful development of the bioprocess system would be a mutual beneficial solution for local aqua-industries and environmental pollution control. In addition, the bioprocess could be applied widely to other agri-food by-products to produce the value-added products for the sustainability of agriculture production and environmental protection.
Comparison of different technologies for dilute milk parlor wastewater treatment and reuse
(University of Hawaii at Manoa, 2007) Lin, Luo-Ting
Analysis of segmentation methods for partial volume correction in magnetic resonance spectroscopy voxels
(University of Hawaii at Manoa, 2007) Andrews-Shigaki, Brian C.
Application of EMMC-biobarrel technology for domestic wastewater treatment and reuse
(University of Hawaii at Manoa, 2006) Zhu, Jia, 1977
The entrapped-mixed-microbial-cell-biobarrel (EMMC-biobarrel) processes with both configurations of single-layer and double-layer were investigated for the removal of carbon and nitrogen simultaneously from synthetic-domestic wastewater with a CODIN ratio of 5 under various operational conditions. For the single-layer systems, the carrier was employed at the packing ratios of 10% and 20% based on the bioreactor water volume. In the double-layer system, carriers were separated into two layers which occupied the top and bottom parts of the reactor with an overall packing ratio of 13%. At the organic and nitrogen loading of O.75kg COD/m3/day and 0.16kg NH3-N/m3/day, all these systems achieved more than 96% of SCOD removal and NH3-N removal efficiencies under continuous aeration. The double-layer system achieved about 40% of total nitrogen removal, which was comparable with the single-layer system with packing ratio of 20% but higher than the single-layer system with a packing ratio of 10%. The SRT for the double-layer system and single-layer system with a packing ratio of 20% could be achieved to more than 200 days. Based on the economics analysis, in the achievement of comparable performance, the capital cost for the double-layer configuration was lower than that for the single-layer configuration. Therefore, double layer configuration is recommended for the EMMC-biobarrel process design. EMMC-biobarrel process offers many advantages over the existing wastewater treatment processes including small space requirement, simple operation and maintenance and . improved nitrogen removal. It demonstrates great potential for onsite, small scale/land limited wastewater treatment applications. The installation cost for an EMMC-biobarrel treatment unit with capacity of 400 gallons/day and 1,500 gallons/day are estimated as $4,671 and $10,191, respectively, which are comparable or lower than those for the existing commercial products which also involve the nitrogen removal technology. For small sca1e/land limited application, the total cost requirement is about $0.90 per 1000 gallons for treating settled domestic sewage per day.
Engineering and economic evaluation of innovative bioreactor for milk parlor wastewater treatment/reuse
(University of Hawaii at Manoa, 2006) Kongsil, Piyalerg
Hydrogen production from glycerin reforming
(University of Hawaii at Manoa, 2006) Douette, Aurelien M.D.
Following a factorial experimental design, a series of tests were performed to investigate the effects of operating parameters; oxygen to carbon ratio (O/C), steam to carbon ratio (SIC) and temperature (T), on reforming glycerin to a H2 rich gas. A mathematical model defining the effect of those three variables was derived., and used for improving the reaction hydrogen yield. From the range of experimental conditions tested it was concluded that OIC, as well as the interaction between OIC and temperature had the most important effects on H2 yield. 4.5 mole of hydrogen were produced per mole of glycerin at experimental conditions of O/C=1, S/C=2.2, and T=804°C. This is 65% of the maximum theoretical yield, and 90% of the yield predicted by thermochemical equilibrium. 1.4 moles of carbon monoxide per mole of glycerin were also produced., presenting a potential for an additional 1.4 mole hydrogen per mole glycerin. A water gas shift reaction was then used., and its operating temperature optimized, in order to convert the reformate gas CO into hydrogen by combining it with water. Results were satisfying, with a final yield of 5.3 moles H2 I mole glycerin, which is 75% of the maximum stoichiometric hydrogen yield. Crude glycerin, obtained from biodiesel production, was finally tested (without a water gas shift) as a feed to compare it with pure glycerin used throughout the tests. The initial results were very encouraging, almost identical to those of pure glycerin, but carbon formation quickly became a problem. Possible contaminants causing the coking may include methanol, chloride and sodium cations, and free fatty acids, all present in crude glycerin as byproducts of biodiesel synthesis.
Hydrodynamics and mass transfer in a novel multi-airlifting membrane bioreactor
(University of Hawaii at Manoa, 2007) Xu, Zhe
Nowadays, in order to relieve the environmental burden, more and more concerns are concentrated on how to maximally dispose the industrial organic waste. Meanwhile, it is expected to find a solution which can combine the waste treatment with the production of valuable products. In this way, the high cost of disposal procedures would be effectively cut down by adding extra value in it. The procedure of production of polyhydroxyalkanoates (PHAs) provides such a beneficial waste treatment which can be applied In various industries, especially in food processing industry where high cost of high BOD wastes treatment is involved (Yu and 51 2001). By using different configurations of bioreactors, several new technologies have been developed demonstrating the feasibility of combining anaerobic digestion of food scraps with aerobic production of biodegradable thermoplastics, polyhydroxyalkanoates (PHAs). Yu and his coworkers (1999) reported the effects of superficial gas and liquid velocities on bed expansion, solid and gas hold-ups and specific oxygen mass transfer rate, kLa by using a type of porous glass beads for immobilization of microbial cells in a three-phase aerobic fluidized bed reactor (AFBR) with an external liquid circulation. This is the first attempt to combine the anaerobic/aerobic treatment of wastewater to produce PHAs. Later on, Du and Yu (2002) developed a new technique to connect the anaerobic reactor and the aerobic reactor through a tubular module of silicone rubber membrane or dialysis membrane. Their efforts yielded 72.S% (wt) PHAs In PHA-producing cells which was the highest polymer content achieved in waste treatment since their work were reported. Although waste water process can get great benefits from PHAs production, the major barrier to widely apply the production of PHAs is their high price, which is more than 10 times higher than the price of synthetic counterparts, reported by Yu and 81 (2001). PHAs have attracted academic and industrial attention due to their potential use as biodegradable thermoplastics. The production cost can be Significantly reduced by raising the scale as well as the productivity of bioreactors. Based on this, we investigate a mini-pilot scale bioreactor (SOL), which is promising to be scaled up to 3000L for PHAs production at a reduced production cost. In this work, a multiple airlifting membrane bioreactor (MAMBR) was designed, fabricated and investigated for operational hydrodynamics and mass transfers (as shown in Flg.1.1).
Pseudo-Steady Model For Anaerobic Bio-Nest Reactor For Treatment Of Milk Parlor Wastewater
(University of Hawaii at Manoa, 2005-08) Koppar, Abhay
Determination Of Chemical Contamination In Green Coffee Beans Grown In East Timor
(University of Hawaii at Manoa, 2005-08) Reis, Carlospeloi Dos
Optimal Harvesting Strategy For Haematococcus Pluvialis Using A Stella-Based Model
(University of Hawaii at Manoa, 2004-12) Tsang, Shuki
One method for reducing the atmospheric concentration of carbon dioxide, C02, a greenhouse gas that plays a role in global warming, is to capture it from stationary combustion systems that burn fossil fuels and sequester it underground, in the deep ocean or in biological sinks such as photosynthetic microalgal species. The cost of capture and sequestration of CO2 is not insignificant and this poses a serious hurdle to the implementation of this greenhouse gas emissions mitigation strategy. Toward this end, research and development is being conducted to develop low-cost, high efficiency CO2 gas separation systems. Another alternative that has been explored is utilizing captured C02 in commercial processes to generate an offsetting income stream, while displacing C02 that would otherwise need to be generated (by oxidation of fossil carbon) for these processes. Under adverse environmental conditions, the photosynthetic microalgae Haematococcus pluvialis produces a high-value compound called astaxanthin, a carotenoid pigment that provides health benefits to humans and that is also used in mariculture feed to enhance the color of salmon flesh. Mera Pharmaceuticals, Inc. has an industrial-scale astaxanthin production facility on the island of Hawai'i. In their production process, Haematococcus pluvialis is first grown in a photobioreactor called a Mera Growth Module (MGM). A portion of the culture is then transferred to open ponds where astaxanthin accumulates in the cells under imposed environmental stress. The harvesting strategy for the transfer of cells from the MGM to the pond has not been optimized. The goal of this study was to explore utilization of captured C02 for Haematococcus pluvialis cultivation and to assess the benefits of this in terms ofCO2 displacement (utilization) and biomass production (i.e., revenue generation). The specific objective of the research described in this thesis was to develop a process model that could be applied to optimize the harvesting strategy from the perspective of maximizing carbon uptake. The model employed STELLA, a commercially available simulation software package. Results of the present study suggest that the carbon capture efficiency of the photobioreactor system is modest. About 25% of the carbon sparged into the media is eventually assimilated into the cell biomass. Most of the remaining 75% is lost via degassing and venting. To maximize carbon capture efficiency, a closed system in which vented gas is recirculated back into the photobioreactor should be explored. Simulations were conducted to identify harvesting scenarios that would maximize cell biomass yield (and, hence, carbon capture). It was determined that reducing harvesting quantities while increasing target cell concentrations in the photobioreactor could provide significant increases in cumulative yield (about 10%) compared to the harvesting strategy currently applied by Mera Pharmaceuticals, Inc. Unfortunately, this would require daily harvests and additional ponds. A target cell concentration of 5.5 x 105 cells/mL and a harvesting cell quantity of 3.2 x 1012 cells produced a realistic (i. e., achievable with the current labor force and ponds) maximum cumulative yield of 3.12 x 1013 cells, which is 2.57 x 1011 cells greater than the cumulative yield of the current harvesting strategy. This is an insignificant gain; hence, the current harvesting strategy appears to be very close to the best scenario under the real constraints imposed by labor force and available ponds. Although the number of harvesting scenarios tested was limited, the results suggest that the process model can be a valuable tool in optimizing microalgae production operations from the perspective of profit or carbon capture.
Development And Characterization Of A Parallel Microbioreactor System
(University of Hawaii at Manoa, 2004-12) Rivera, Gwendolyn Leialoha Cheney
A parallel microbioreactor with novel optical sensors was developed for monitoring and controlling cell culture conditions. A dissolved oxygen sensor based upon the fluorescence quenching of ruthenium diphenylphenanthroline dichloride was developed, and a novel fiber optic sensor configuration was implemented in a six-well microbioreactor array. The oxygen sensor's response to dissolved oxygen was shown to be comparable to that of a commercial Clarke-type probe. Furthermore, the sensor configuration resulted in a sensor that exhibits sensitivity to oxygen but is independent of the turbidity of the surrounding fluid. An optical density sensor based on light transmittance was also created, and demonstrated similar response to conventional absorbance measurement methods. These optical sensors, being compact and relatively inexpensive to fabricate, are well suited for miniaturization and multiplexing. The six-well bioreactor system that has been developed herein serves as a prototype for potentially larger arrays of microbioreactors. The sensor design may also find applicability in a wide range of optical sensors.
Aerobic And Anaerobic Process For PCBs Removal From Aqueous And Oil Phases
(University of Hawaii at Manoa, 2004-12) Liu, Kan
Anaerobic Treatment Of PCBs-Contaminated Oil
(University of Hawaii at Manoa, 2004-12) Ahn, Sun Young
Characterization of residual soluble Cod in entrapped-mixed-microbial-cell and activated sludge process
(University of Hawaii at Manoa, 2003-08) Song, Chenyan; Yang, Ping Yi; Bioengineering
To meet more strict standards than before for wastewater discharge and reuse criteria, a post-treatment for the secondarily treated effluent needs to be followed. This means not only additional cost, but a more complicated design and operation for a tertiary treatment is involved. Therefore, an evaluation of the characteristics, such as concentration, molecular weight distribution (MWD) and composition of residual soluble COD from a secondary treatment process is required. In this work, a conventional activated sludge process (ASP) and entrapped-mixed-microbial cell (EMMC) process (fluidized-bed and packed) were investigated. The investigation of the system performance shows: at the operation of 1 hr aeration/1 hr non-aeration with HRT 16.5 hr, all of the reactors had> 95% of COD removal and > 66% of nitrogen removal for treating high-strength synthetic wastewater (COD ~ 700 mg/l); at the operation of 1 hr aeration/1 hr non-aeration with HRT 6 hr, the EMMC reactors had> 93% COD removal and > 45% nitrogen removal for low strength synthetic wastewater (COD ~ 200 mg/l), while the ASP reactor had > 93% COD removal and 26.6% nitrogen removal at continuous aeration with HRT 6hr. Due to the longer SRT (solid retention time) for EMMC process, the MWD patterns and composition of the residual soluble COD (RSCOD) for the treated effluent of the EMMC are different from those of ASP when operated under the same HRT and aeration time. The study on the MWD shows the change of HRT, aeration and OLR cause different patterns for the RSCOD of the treated effluents from the same reactor. The experiment indicates that the effluent of the EMMC is more suitable to be treated physical-chemically than biologically in tertiary treatment, because it has more biologically stabilized components produced than that of the ASP process. Further biological oxygen demand for this stabilized effluent is apparently not required. The accomplishment of this work will provide a guideline for the requirement and design of a unit process for tertiary treatment.

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