Dissertations / Theses on the topic 'Autothermal thermophilic aerobic digestion'

The current research relates to a system driven by renewable energy and chemical energy contained in the feed, which will eliminate and reduce pathogens found in human excreta. A project in the form of an experiment for demonstration will be designed and built to operate in the local waste water treatment plant. Data will be analyzed and recorded, including fecal coliforms and E.coli levels, chemical oxygen demand (COD) and total solids removal (TS). The effectiveness of the system will depend upon results obtained and weather conditions. The principal objective of the research is to test and demonstrate that the "Small Decentralized ATAD" is successful in removing/eliminating enteric pathogens found in human excreta. Most importantly, the Bill and Melinda Gates Charity Foundation is providing financial support (Grants) for new sanitation ideas to help developing countries overcome diseases, specifically water borne diseases and also diseases related to hygiene and sanitation. Moreover, the "Water, Sanitation & Hygiene: Grand Challenges Explorations" granted a $100,000 Grant to Professor James Blackburn from Southern Illinois University at Carbondale in the Mechanical Engineering and Energy Processes Department. Consequently, the "Decentralized Next Generation for Diarrheal Pathogens" project will be tested using the ATAD (Autothermal Thermophilic Aerobic Digestion) to demonstrate its effectiveness in pathogen reduction and elimination.

Five different combinations of Hydraulic Retention Times (HRT) and temperatures were used in a two stage (feed and test reactor) Autothermal Thermophilic Aerobic Digestion System to assess the impact of these parameters on the production of odorous gases. The gases monitored were hydrogen sulphide, dimethyl sulphide, methyl mercaptan, ammonia, and amines. Other liquid parameters were also monitored in order to better understand the impacts of temperature and HRT. These parameters are total solids content, volatile solids content, volatile solids destruction, specific oxygen uptake rate, alkalinity, ammonia concentration, and pH. In order to assess the character of the sludge and understand the digestion process the carbohydrate, fat, and protein content were also measured in the inputs and in the test reactor. It was found that all of the odorous compounds measured were affected by stage of digestion and temperature more than by HRT. Of the five compounds monitored, none were affected by changes in the HRT of the test reactor. However, the concentrations measured in the feed and test reactors were often a degree of magnitude apart. The reduced sulphur compounds (hydrogen sulphide, methyl mercaptan, and dimethyl sulphide) were found in higher concentrations in the feed reactor than in the test reactor; whereas ammonia and amines were found in much higher concentrations in the test reactor than in the feed reactor. Also, ammonia concentrations were significantly higher in both reactors when the temperature was higher; and amine concentration was higher in the test reactor when the temperature was higher. One set of tests for volatile fatty acid concentration was also undertaken. While breakdown of the carbohydrates and fats occurred throughout the process, proteins were broken down into their amino acids, releasing reduced sulphur compounds in the feed reactor and then deaminated, releasing ammonia and amines in the test reactor.

Autothermal thermophilic aerobic digestion (ATAD) of sludge has been used to produce class A biosolids. With stringent EPA guidelines, more and more municipalities are looking to use this process for digestion of sludge. However the large polymer costs associated with dewatering these sludges has made the use of this technology unfavorable. Several studies have been conducted in the past which have looked into the mechanism leading to such a poor dewatering of sludge. Some of these studies have attributed the release of protein and polysaccharide during the high temperature digestion to be responsible for the poor dewatering. However the exact mechanism leading to the poor dewatering is still not totally clear. Laboratory scale studies were conducted to evaluate the mechanism leading to the poor dewatering of these sludges and also to be able to economically condition these sludges. ATAD sludge samples were collected from ATAD processing facilities in Ephrata, PA, Cranberry, PA, Titusville, FL and College Station, TX. The research included experiments evaluating the protein and polysaccharide concentrations in solution, cations and anions, iron and aluminum, zeta potential and capillary suction time. It was found that during digestion large amounts of protein and polysaccharide were released which were in the colloidal range, and the dewatering of each of these sludges became poorer as the amount of protein and polysaccharide in the solution increased. The release of protein and polysaccharide was related to the monovalent to divalent cation ratio and the iron and aluminum concentration in the sludge. Also during the digestion process, the pH of the sludge increased appreciably and the divalent cations precipitated out. The zeta potential of the ATAD digested sludge was also found to be positive. Different chemical coagulants were used to condition the sludge, but even with high polymer doses the dewatering of the sludge was not satisfactory. A combination of iron (or cationic polymer) followed by anionic polymer was found to improve the dewatering to a desired level. The use of this combination of sludge conditioning also provides an economical solution to the problem of dewatering. The role of iron in improving the dewatering of the sludges was found to be important, with the sludge dewatering being better for sludges with a high iron content. The combination of high pH, divalent cation precipitation, iron deficiency and biopolymer release all contribute to the poor dewatering of ATAD sludge.
Master of Science

The efficacy of Volatile Fatty Acid (VFA) production in Thermophilic Aerobic Digestion (TAD) of primary sludge was investigated. This research program was carried out in a pilot scale, TAD process, located in the wastewater treatment pilot plant site, at the University of British Columbia. Preliminary results showed that the highest accumulation of VFA (950 mg/L as acetate) had occurred, under microaerobic conditions (air flow rate of between 0-0.17 V/V-h), in the first stage of the 150 L, 2-stage process. The two other aeration conditions examined (transition-air flow rate of 0.28 V/V-h and aerobic-air flow rate of 0.6 V/V-h) accumulated negligible amounts of VFA. Therefore, the subsequent research concentrated on the first stage of the TAD process, under microaerobic conditions. The two independent variables examined were air flow rates and solids retention times (SRT). The three SRTs tested were 3, 4.5 and 6 days. The four air flow rates examined were assigned the labels true anaerobic, low flow microaerobic, medium flow microaerobic and high flow microaerobic conditions. Net VFA production was found to be a function of both aeration and SRT. In general, as SRT and air flow rates decreased, net VFA production increased (specifically acetate and propionate). The measured concentration of any species of VFA, at any given time, was a function of both the relative rates of its synthesis and biodegradation. Decreasing or increasing the aeration rate and/or SRT resulted in a proportional change in VFA accumulation. The maximum measured acetate accumulation rate occurred under the 4.5 d SRT and the true anaerobic condition. A biochemical model was developed in order to explain the process of VFA metabolism in TAD. In this process, under strict anaerobic conditions, bacteria must achieve oxidation/reduction balance by diverting the catabolic flow of carbon to fermentative end products (eg. propionate) that will consume NADH (Nicotinamide Adenine Dinucleotide). The key issue in fermentation is the recycling of NADH by the conversion of specific intermediates to different fermentation products which regenerate NAD⁺. The oxidation of intermediates that required the net reduction of NAD⁺ cannot proceed under fermentative conditions. Consequently, these catabolic intermediates added under batch test conditions, using TAD sludge, under anaerobic conditions, remained in their unoxidized form and persisted in the medium. The oxidation of intermediates which required no net reduction of NAD⁺ can and did proceed under fermentative conditions. Under strict anaerobic conditions, the VFA profiles in the pilot scale TAD process were similar to fermentation type processes (eg. an even distribution of VFA between acetate and propionate). When the bioreactors were operated under microaerobic conditions (ie. oxygen demand is greater than oxygen supply), metabolism resulted in a characteristic VFA distribution profile with acetate as the predominant VFA produced (up to 80% of the total VFA). Propionate constituted the second largest fraction at 11%. Under this microaerobic condition, the NADH produced during oxidation of substrates could be reoxidized by operation of the respiratory chain. Therefore, the carbon flow could be uncoupled from the necessity to maintain redox balance via fermentative means. This separation would presumably allow the organisms in a TAD process to maximize ATP (adenosine triphosphate) production by increasing the flux of intermediates to acetate. The majority of the substrates examined under batch test conditions, with TAD process biomass, under microaerobic conditions, were oxidized to an acetate intermediate.

博士
國立中興大學
環境工程學系
92
The autothermal thermophilic aerobic treatment (ATAT) is a biological process in which the operating temperature can be maintained spontaneously at 45 — 65 oC. Comparing with the activated sludge process (ASP), the ATAT produces significantly less excess sludge yet proceed at higher reaction rate. However there is a need of developing evaluation tools for heat and kinetic analysis for the ATAT system. This study aims to develop mathematical and laboratory procedure for the determination of specific biological heat potential (hb, cal/(g Ou)) and kinetic parameters for the ATAT system. In order to verify these procedures, this study conducts respirometric tests and analyzes data collected from full-scale ATAT operation. Three kinetic algorithms and two hb algorithms are proposed for this study: (1) respirometric batch kinetic algorithm, (2) respirometric serial dilution kinetic algorithm, (3) respirometric graphical kinetic algorithm, (4) respirometric hb algorithm, and (5) full-scale hb algorithm. Based on the Monod kinetics, this study first develops a two-phase model for analyzing a batch OUR vs. Ou respirogram. An algorithm is then proposed to determine the four Monod kinetic parameters (mm, Yg, Ks, and kd) and the initial seed (Xo) and substrate (So) concentration. The algorithm is illustrated by a respirometric test on glucose of 10,000 mg/L COD at a temperature of 55oC. The result shows a maximal specific growth rate (mm) of 6.37 1/d, gross growth yield (Yg) of 0.84 mg BOD of X/mg BOD of S, half-saturation constant (Ks) of 82.3 mg/L BOD, and decay coefficient (kd) of 0.44 1/d for the ATAT system. This study also develops a respirometric serial dilution kinetic algorithm. The procedure requires only one batch test, using a series of substrate concentration (So) at the same seeding dosage (Xo). The algorithm can be used to determine for the type of kinetic model (Haldane vs. Monod) based on testing results with that the corresponding kinetic parameters can be assessed. In addition, the algorithm can determine a ratio of biodegradability (bBOD/ThOD) of the substrate. A test is conducted on para-hydroxybenzoic acid (PHBA) as the substrate at various concentrations. The result shows a biodegradability ratio (bBOD/ThOD) of 1.38 mg BOD/mg ThOD and observed growth yield (Yo) of 0.16 BOD of X/ BOD of S. It further determines that the Michaelis-Menten model is more appropriate with a km of 1.3 1/hr and Ks of 12 mg/L BOD. The bBOD/ThOD is greater than 1, which may be caused by the nitrification of NH4Cl being added as a nutrient for that nitrification inhibitor (TCMP) is not used. The graphical algorithm offers another solution for kinetic parameter estimation based on OUR vs. Ou respirograms, which can also be used for the diagnosis of respirometer tests. This study performs a respirometric test on glucose-glutamic acid (GGA) at three different seeding sources. The result shows that seeding source and the mixing intensity are two major factors affecting the pattern of respirogram. Other factors include the diversity of microbial consortium, the homogeneity of seeding, and the substrate residual carried over from seeding materials. This study attempts to develop a bio-calorimeter capable of simultaneous measuring of accumulative heat compensation data (Hc vs. t) and oxygen uptake data (Ou vs. t) so that the hb of a given substrate can be experimentally determined. A test is conducted on glucose of 10,000 mg/L COD, yielding an average hb of 51.4 kcal/(g Ou) with a large variation coefficient (Cv) of 80%. The estimated hb is much higher than the value of 3.4 — 3.5 kcal/(g Ou) reported by previous researchers. An analysis by computer aided design (CAD) program indicates that the errors are likely associated with high compensating heater power (100 W), poor precision of temperature probe (±0.25oC), less frequent on/off temperature control (0.5 1/s), and high operating temperature (> 45oC) making the oxygen sensor malfunction. It is suggested further study be made for improvement. For full-scale application, this study also develops a heat balance model for assessing hb and system analysis based on daily operating data of temperature (Tt), COD of influent (Si,COD) and effluent (Se,COD), biomass concentration (Xt,SS), and effluent solids (Xe,SS). A case study is analyzed using 6-month daily operating data of a full-scale ATAT plant located at north part of Taiwan. The plant was verified to be definitely autothermal for that the biological heat rate (Jb) was determined to be the major source (89.1%) for heating the influent at 29oC to the reaction temperature of 48oC. The result shows that increasing the sludge retention time (SRT), the oxygen transfer efficiency (OTE), and the influent temeperature (Tw) and concentration (Si,COD) can all increase the autothermal temperature (Tt). The analysis also indicates that, providing an oxygen transfer efficiency (OTE) of 20% and SRT of 30 d, the influent substrate should be at least 6,000 and 9,000 mg/L COD to maintain the operating temperature of 45oC and 50oC, respectively.

碩士
國立中興大學
環境工程學系所
101
The activated sludge process is the most widely used biological treatment process for municipal and organic industrial wastewaters treatment, But the major by-product of this process is waste activated sludge (WAS). The treatment and disposal of WAS accounted for about half, even 60%, of the total wastewater treatment cost. Thermophilic aerobic digestion (TAD) is a process being operated at 45-65℃ in the aerobic condition. Also, a considerable amount of heat would be released during the aerobic biological process which can make autothermal thermophilic aerobic digestion an economically viable option. USEPA assessed the autothermal thermophilic aerobic digestion (ATAD) was a feasible process on the sludge digestion. ATAD process also demonstrated its major merits on the high biosolids mass reduction, acceptable PFRP (process to further reduce pathogens) performance, and high digestion rates. In this study, the thermophilic aerobic membrane bioreactor, with a volume of 25 L, was operated at 55℃. Initially, a mixed thermophilic bacterial culture was acclimated with the influent substrate of 10,000 mg-COD/L which was made of glutamic acid and sucrose. When the system reached steady state, the same concentration of the glutamic acid, sucrose and wasted sludge were substituted for the influent substrate. In addition, this study embloyed different batch test to obtain factors affecting sludge degradation and operations. Furthermore, PCR-DGGE was applied to determine the microbial communities of mixed culture in the bioreactor. The results showed that the average removal efficiency of SCOD was 86% and the cofficient of growth (Y) was 0.17 mg-cell/mg-COD when treated with high concentration organic wastewate. That confirmed the thermophilic aerobic digestion system had exhibited considerable advantages for the treatment of high-strength wastewater and low sludge production. When the influent substrate was made of glutamic acid, sucrose and wasted sludge, the results showed that the removal efficiency of TCOD, MLSS and SCOD were up to 28、10 and 71% respectivily. After mixing the thermophilic bacteria which were taken from different sources to digest the WAS, the result showed that the removal efficiency of MLSS and MLVSS were up to 27 and 38% at 25 days.

碩士
國立臺北科技大學
環境規劃與管理研究所
95
As the more popular sewerage treatment system, the more sludge produced in Taiwan. Depending on the characteristics of organic sludge, this study researches the properties of thermophilic aerobic digestion by innovative technologies developed. In this process, the excess activated sludge is reduced in two stages : (1) A part of the returned sludge is solubilized with enzyme secreted from the thermophilic bacteria in the S-TE reactor. This enhances the bio-degradability of the return sludge. (2) The solubilized return sludge is then decomposed and mineralized by the activated sludge microorganisms in the aeration tank. The focus is about the properties of thermophilic aerobic digestion applying in sewage by S-TE process. The experiments includes two parts: one is pre-heat at the level of 60~65℃, and find out the efficiency of disintegration cell well. The other is thermophilic aerobic digestion. The results show that the most advantageous temperature for microorganism is 60~65℃. In addition, dissolve COD twice as which not be 360 min agitating, indicate agitating help for the efficiency of disintegration. The results also show that removal efficiency in batch digestion of SS, VSS and CODss are 53.7％, 64.3％ and 63.3％. removal efficiency in semi-continuous digestion efficiency of SS, VSS and CODt are 30.2％, 50.4％ and 24.8％. Overall sludge broken and thermophilic aerobic digestion are positive help.

碩士
國立臺北科技大學
環境工程與管理研究所
97
In order to improve environmental quality, Taiwan’s government makes more effort on building sewerage systems construction. These operating sewerage systems will lead to an important increase in sewage sludge production .Due to the limitation of landfall site, municipal sewage sludge disposal will become a hot issue in the future. The purposes of this study was to carry out the comparison the different of the ultrasounds and untreated sludge, moreover the kinetic analytic integrated with thermophilic aerobic digestion process were also be discussed. The aim of ultrasounds is to solubilise and/or to reduce the size of organic compounds, and especially refractory compounds, in order to make them more easily biodegradable. Final quantity of residual sludge and time of digestion can thus be reduced. The objective of pretreatment is to increase reduction efficiency of thermophilic aerobic digestion. The characteristics of thermophilic aerobic digestion process include three parts: (1) increase in organic sewage sludge reduction (2) sludge retention time can be reduced (3) biosolids may be totally contained until they are stabilized. The characteristics of sludge dynamics was also studied and the dynamics model can be utilized to (1) understand the changing of sewage quality and the operational conditions of sewage treatment; (2) lower the cost of sewage treatment (3) support management policies and help to evaluate new sewage treatment design, and shorten the designing time. The experiment includes two parts. The first is pretreatment of sludge using ultrasounds, and find out the efficiency of disintegration cell well. The second stage takes substrate concentration before and after digestion to derive the indecomposable ratio. Inserting the number into the Monod equation, μmax and Ks was obtained. From the result of this experiment, the digestion dynamics coefficient, and the comparison to references, it was demonstrated that the 4 experimental groups, there were (Ks) 8410, 978, 198, 4340 mg/L separately. We suspect the reason that a high Ks was achieved with the combination of thermophiles and ultrasound irradiation is that the experiment was partial continuous and the air sparging mixer was not automated.This was only observed in a combination of thermophiles and ultrasound irradiation. The result demonstrates that ultrasound irradiation in combination with high temperature digestion can increase Ks and the microbes in sludge, enabling a better decomposition of substrate.

The biological nutrient removal (BNR) process usually requires external carbon supplements for enhanced phosphorus and nitrogen removal. It has become popular for full-scale wastewater treatment plants to implement carbon addition and optimization, to ensure best system performance. Thermophilic aerobic digestion (TAD) is operated at elevated temperatures to achieve sludge stabilization, volatile solids destruction, and pasteurization. Preliminary tests indicated that the volatile fatty acids (VFAs) accumulation in the TAD sludge supernatant, under a microaerated operation (system oxygen demand exceeds the supply), was a potential carbon source for BNR enhancement. A targeted degree of solids destruction efficiency can also be achieved under the microaerated operation, and the VFAs can be internally recovered for BNR enhancement purposes. The objectives of this study were to investigate the feasibility of using the TAD supernatant as a carbon source for BNR enhancement, and the potential impacts of the TAD supernatant addition on the system performance. Furthermore, due to the nature of VFA variance in TAD supernatant, TAD supernatant addition must be optimized in practice to obtain the benefits of carbon supplement and eliminate the potential nutrient overloading. A new control and monitoring technique was developed in this study using the headspace gaseous monitoring to estimate the VFA concentrations in TAD supernatant, and assess the BNR system performance. In this study, TAD supernatant was proven to be a potential carbon source for B NR enhancement in both batch and continuous feed studies. The VFAs in TAD supernatant resulted in comparable phosphorus release and denitrification. In addition, substrates other than the VFAs in the TAD supernatant were also found to be available for both P release and denitrification. The extra nutrient load (nitrogen and phosphorus) was significant, requiring mitigation and dosing optimization to reduce treatment system deterioration. Due to the feature of degradation during its storage, it was found that TAD supernatant should be added into the process train as fresh as possible, to maximize the VFA utilization and heat energy production. The "headspace carbon dioxide (C0₂) monitoring" method proposed in this study was proven feasible in estimating the VFA equivalent in the TAD supernatant. This C0₂ monitoring approach can be applied for the on-line TAD supernatant dosing optimization practice. The duration of C0₂ changes shown on the C0₂ profile (between the point of C0₂ starting to increase, and the point starting to decrease after the peak) of the phosphorus release and denitrification enhancement, due to the external carbon source addition, was defined as the "E Time" in this study. The duration of "E Time" was found to be proportional to the available carbon source concentration at the time of addition. A high accuracy in sodium acetate (NaAc) concentration estimation was also demonstrated in this study. In addition, the VFA equivalent in TAD supernatant was derived by comparing the "E Time" with a standard sodium acetate test. This headspace C0₂ monitoring can be potentially applied as a means of monitoring the efficiency and microorganism activity in a BNR process train. This "E Time" approach using the headspace C0₂ monitoring can be an attempt to replace the current oxygen utilization rate (OUR) method for readily biodegradable substrate determination. BNR operation can be benefited by this on-line monitoring to obtain the information of readily utilizable carbon concentration, optimized dosage control, and system performance. The headspace monitoring setup also prevents the sensor contacting with the sludge samples and saves the maintenance efforts.

This study was on autothermal thermophilic aerobic digestion (ATAD) of "Biological Nutrient Removal" (BNR) sludge. Solids and nutrient balances were performed using 2 bench scale thermophilic aerobic digesters operated in series. In total there were 4 reactors; 2 series running in parallel. The digesters were fed waste activated sludge from a biological phosphorous removal treatment plant located in Penticton, B.C. Four experiments were completed, each under different aeration conditions and different hydraulic retention times i.e. a 2x2 factorial design. The aeration conditions were defined by a combination of airflow, oxidation reduction potential and dissolved oxygen measurements. The hydraulic retention times that were investigated were 24 hours and 48 hours and the aeration rates used in conjunction with them were 0.5 L/min and 1.5 L/min. The overall findings were that this type of treatment was extremely successful in decreasing chemical oxygen demands (COD) and solids levels. In the low air flow experiments the decrease in COD and solids values were, 35.5% and 45% respectively, and in the high air flow experiments they were 26.5% and 33% respectively. Orthophosphates were noted to increase significantly (+8%) in the low air flow experiments when compared to the high air flow experiments (-12.5%) i.e. therefore there was absorption of the orthophosphates happening in the high air experiments. The total kjeldahl nitrogen (TKN) values were found to decrease by 30% in the low air experiments and 27.5% in the high air flow experiments. The liquid phase nitrogen increased by 134% in the low air experiment and by 124% in high air flow experiments.

博士
國立中興大學
環境工程學系所
101
The autothermal thermophilic aerobic treatment (ATAT) system is a biological process in which the operating temperature can be spontaneously maintained at 45 - 65oC. Comparing with the activated sludge process (ASP), the ATAT produces significantly less wasted sludge. Although, full-scale ATAT or autothermal thermophilic aerobic digestion (ATAD) systems have been well documented in literature, the technology is not widely used due to the scarcity of documentation relating to spontaneity and feasibility. There is no effective technique to evaluate the feasibility of an ATAT system. Therefore, it is necessary to develop evaluation tools for the specific biological heat potential (hb) and kinetic analysis for the ATAT system. This study also verifies the two-phase kinetic model algorithm of respirometer serial dilution kinetic and estimates microbial kinetic parameters. Based on the two-phase model for analyzing a batch OUR vs. Ou respirogram was analyzed. For this verification study, results showed that the maximal growth rate (μm), half-saturation constant (Ks), decay coefficient (Kd) and gross growth yield (Yg) had lower coefficients of variation (Cv value was 2.5% to 15.9%) than that from the transient method. Because the oxygen uptake estimation variability of substrate was only 2.5%, therefore, respirometer is an advantageous tool to estimate kinetic parameters in microbial systems. Then, it is suggested that the ratio of S0/X0 must be higher 15 for two phase kinetic model algorithm of respirometer. The algorithm was illustrated by a respirometric test on glucose of 2,500 mg/L COD at 55oC. The result shows the μm of 5.16±0.1 1/d, Yg of 0.46±0.04 mg BOD of X/mg BOD of S, Ks of 401.7±15.2 mg/L BOD, and Kd of 0.39±0.05 1/d for the ATAT system. Also, these microbial kinetic parameters had the tendency showing that an increase in temperature also increased these paramenters. The temperature effect constants (Φ) of van’t Hoff-Arrhenius law for μm, Ks, Kd and Yg were 1.040, 1.028, 1.019 and 1.033, respectively. This result demonstrated the ATAT system has successfully competed the traditional active sludge with better microbial kinetic parameters and higher potential treatment efficiency for high concentration organic wastewaters. Then, this study focuses on the calculation of hb of wastewater in an ATAT system. The treatment system was daily fed with realistic and artificial wastewater at 11,250 and 17,420 mg COD/L, respectively. The wastewater was rich in oil and grease (O&G) at 1,220 and 600 mg/L, respectively. The sludge retention time (SRT) was controlled at 5 days. The results showed that the COD removal efficiency was as high as 88 to 93% for the realistic and artifical wastwaters, respectively. The O&G reduction was 69 to 72%. These two systems could maintain reactor operating temperatures at 43 oC and 48oC, respectively. The average values of hb were 3.7 and 3.1 kcal/g-COD-removed and the observed growth yield (Yo) were 0.10 and 0.13 mg MLSS/mg COD for realistic and artificial wastewater, respectively. Next, this system was daily fed with oily and artificial wastewater at 21,460 mg/L COD. The SRT was controlled at 5 days and tank temperature was controlled at 35, 45, 55, and 65oC. The results showed that the COD removal efficiency was 77% to 91%. However, the O&G removal efficiency was 50% to 69%. These results might indicate that oil and grease become more soluble and accessible to microorganisms at high temperatures. The average values of hb were 3.25 to 3.63 Kcal/g-COD-removed for the artificial wastewater. The values of Y0 were 0.08 to 0.19 mg-MLSS m/L-COD for the wastewater at different temperatures. The temperature effect constant (Φ) of van’t Hoff-Arrhenius law for Yo was 0.958 with ATAT pilot study, which explained typical characteristics showed in the low sludge yield of an ATAT process. The high organic matter removal capacity with low sludge yield of ATAT process have been demonstrated.

碩士
淡江大學
水資源及環境工程學系碩士班
101
Hospital wastewater treatment plant might receive wastewater from isolation ward or sewage contacted by patients, therefore, their properties are different from general industrial or domestic sewage .Biosolids produced from hospital wastewater treatment plant include waste sludge and screen residue, which might contain lots of unknown pathogens. It will cause the crisis of germs-spreading if without proper handling. Besides, screen residue contains solids rich in organic matters such as food waste, excrements, etc. and smells stinky. 　　Thermophilic aerobic digestion (TAD) process has the advantages of easy operating, small area required, stable system, rapid biomass degradation, and efficiently pathogen inactivation. In this study, we used TAD process to stabilize and reduce the biosolids produced by hospital wastewater treatment plant. At the same time, pathogens were inactivated by TAD process, too. The emphasis in our study was combine waste sludge and screen residue to precede TAD process, in order to improve the efficiency of the degradation of organic matters and solve the problem of odor-emission. 　　In this study VS/TS was used as a decomposable index, the digestion ratio of the total and volatile solid and water quality analysis of filtrate were used as the digestion efficiency indexes, E. coli colonies was used as the pathogen inactivation index. The experiments were operated in batch model. The efficiency of TAD process by explored by modulating sludge retention, proportions of biosolids and operating temperature. Different waste sludge and screen residue ratio were exam, in order to find the optimal combination and different solid liquid ratio, and also realize food loading to the microorganisms. After that, the effects in different operating temperature were discussed. 　　The results found that, combining waste sludge and screen residue in TAD process can degrade biomass rapidly. The better digestion efficiency was screen residue : sludge = 1:2.5(SR/SL=0.48). The reaction rate constant (Kd) is 0.994 day-1.When the digestion temperature controlled at 50℃,we got the better digestion efficiency. In sludge digestion system, the TS and VS digestion efficiency were 51.16% and 55.82% respectively; in sludge and screen residue digestion system, the TS and VS digestion efficiency were 47.59% and 51.85% respectively. After 2-3 days of digestion time, the offensive odor was vanished. According to the qualitative analysis of organic acid, TAD process was found to fit the pathway of TCA cycle. When the operating temperatures were controlled at 50℃ and 70℃, E. coli colonies in biosolids sharply reduced from unable counting to 2.6*105 CFU/100mL and N.D. respectively.

Research was undertaken to determine if a mixture primary and secondary sludge could provide increased volatile fatty acid (VFA) production, as compared with primary sludge alone, in a thermophilic aerobic digestion process. In addition, pre-solubilization of the secondary sludge, with NaOH, was investigated for its effect on VFA production. Previous research has demonstrated that VFA production can be enhanced during the thermophilic digestion of primary sludge with reduction in both aeration and retention time. Secondary sludge was predicted to further enhance production by providing the required substrate for process micro-organisms 'pre-packages' in the correct ratios. Pre-solubilization of the secondary sludge was intended to make this substrate readily available to process micro-organisms, eliminating a potentially rate-limiting step. Pre-solubilization of feed sludge has been shown to enhance anaerobic digestion. Experiments were carried out at UBC's Wastewater Treatment Pilot Plant. Primary and secondary (Bio-P) sludges were generated on-site, by a modified UCT process, and metered to feeding tanks daily for use in the autothermal thermophilic aerobic digestion (ATAD) reactors. Configured in parallel, the two, 125 L reactors were each operated as first stage reactors, in semi-continuous mode, with an average retention time of 3 days. Based on TS, primary/secondary mix sludge ratios of 100/0, 65/35, 35/65, and 0/100 were tested in parallel with primary sludge in the control reactor. The 35/65 and 0/100 streams were additionally pre-solubilized, with 15 meq/L of NaOH, and tested in parallel with non-solubilized mix ratios of 35/65 and 0/100, respectively, in the control reactor. Through all experimental runs: feed consistency was maintained around 1% TS; reactor temperatures stayed between 42°C to 50°C, ie. within the thermophilic range; and a "micro-aerobic" environment was sustained with a constant supply of air into the reactor contents (< 1 mg/L DO, and consistent ORP values between -200 mV and -450 mV). The incorporation of secondary sludge, in mixed sludge feed, resulted in increased production and accumulation of VFA. The greatest production and accumulation of VFA was produced with the digestion of 100% secondary sludge. Although chemical pre-solubilization of sludge resulted in increases in VFA concentrations in the feed tanks, no conclusions could be made with respect to its efFect on VFA production in ATAD. The addition of NaOH did produce large fluctuations in reactor pH. Based on this impact on digester stability, and the positive results obtained without chemical pre-solubilization of feed sludge, further investigations were not undertaken with NaOH. Analysis of nutrient species confirmed that, both the mixing of primary and secondary sludge, and further, the thermophilic aerobic digestion of mixed and secondary sludges, results in the release of stored phosphorus and increases in ammonia nitrogen. Post-treatment, of some type, would be required before recycle to nutrient removal processes.