COD removal and nitrification of piggery wastewater in a sequencing batch reactor : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Technology in Environmental Engineering

Piggery wastewaters are particularly problematic when released untreated into the environment. They contain high levels of chemical oxygen demand (COD) and also nutrients such as nitrogen and phosphorus which can cause eutrophication in surface waters. The sequencing batch reactor is a form of biological treatment in a completely mixed reactor with aerobic and anoxic periods to facilitate nutrient removal. In this study nitrogen removal of piggery wastewater in a SBR by nitrification and denitrification was investigated. Screened raw piggery effluent was used in this study. Average non filtered feed contained a chemical oxygen demand of 12,679 mg/l. The average of the non filtered feed TKN was 1103 mg/l with its largest component being ammonia having an average concentration of 681 mg/l (non filtered feed). Initial experiments with solids retention time (SRT) of 15 days and the hydraulic retention time (HRT) was 5 and 3.3 days for 9 and 4 weeks respectively during Stage 1. No significant nitrification activity was observed during this period. The reactor cycle time was then increased to 2 days which effectively increased the SRT to 30 days and HRT to 6.7 days (Stage 2). The new environment allowed the nitrifying population to develop and nitrification was observed with the formation of nitrite and nitrate. The heterotrophic kinetic constants determined the yield coefficient as 0.49. The maximum specific growth rate (μ max) was 6.8 day-1 and half saturation constant (Ks) was 293.6 mg/l. The COD removal of the feed in the SBR started from around 70% in weeks 6-10 during Stage 1 and reached 92.7% in week 29. Ammonia removal was not significant in the first 17 weeks due to no significant nitrification activity during that time. After initiating a 2 day reactor cycle, ammonia removal rates increased to over 90%. Batch tests indicated that most of the ammonia needed to be removed in the first aerobic period. This allows nitrite and nitrate concentrations to build up and be removed by the subsequent anoxic period. This was when there was enough readily degradable COD as not to inhibit denitrification. The reactor cycle time which achieved full nitrification and the highest nitrate removal by denitrification was observed in the batch test on day 256. The first 6 hour aerobic period removed 81.1% of the ammonia. Subsequent anoxic periods reduced the nitrate concentration in the effluent to 11.0 mg N/l. The nitrification rates increased in the reactor over time as the nitrifying population acclimatised to the piggery effluent. In fact the highest nitrate formation and ammonia oxidation rate was 15.5 mg N/l. h and 24.6 mg N/l.h measured during the last test on day 270. Nitrite formation rates peaked at 11.5 mg N/l.h. The SBR biomass population was able to remove nitrate efficiently as batch tests showed that denitrification rates could reach 22.1 mg N/l.h. The relationship between effluent nitrate levels and COD: ammonia concentration ratio was assessed in order to determine the importance of these chemical characteristics important in controlling the nitrification and denitrification activity in the SBR. Results showed that as the COD: ammonia concentration ratio increases, the effluent nitrate levels decreases. The study found that the SBR was suitable in removing COD and Nitrogen from piggery wastewater

Trends in the education sector from 1993 - 98

Vietnam has achieved remarkably high rates of school enrollment and has maintained good social indicators (infant and under-five mortality rates, life expectancy, fertility rate, child nutrition, and access to basic services) compared to other countries with similar low income per capita. The author documents and analyzes changes in enrollment and education finance in Vietnam from 1993-98. Enrollment rates increased substantially, but the increases were not equally spread across different income groups, regions, gender, and ethnic groups. The higher the level of education, the larger the gap in school enrollment among different socioeconomic groups. Although school fees were no longer compulsory at the primary level, households paid for many other school-related items, such as books, uniforms, private tutors, lunch, and transportation. These costs are a significant financial burden on the poor. On the other hand, there is considerable variation in public spending per student across regions that, when coupled with variation in enrollment rates across regions, resulted in a not pro-poor public spending pattern, although public spending on primary education was neutral in 1998. Finally, the author investigates whether rates of return to education in the private wage sector changed in the 1990s. She concludes that returns to schooling increased substantially between 1992-93 and 1997-98, especially at the upper secondary education and university levels.Public Health Promotion,Teaching and Learning,Curriculum&Instruction,Primary Education,Health Monitoring&Evaluation,Primary Education,Gender and Education,Teaching and Learning,Health Monitoring&Evaluation,Curriculum&Instruction

What\u27s Happening with Potential Ratings?

Several years ago, we would hear everywhere that the performance ratings are dead. Companies then revamped their performance management systems and many went back to ratings they eliminated. Is the same happening with potential ratings? Is the 9-box Performance Potential Grid dead? What are the benefits of doing that? Findings show that across a wide range of tasks, industries and organizations, a small proportion of the workforce tends to drive a large proportion of organizational results. In other words, the top 1% accounts for 10% of organizational output; the top 5% accounts for 25% of organizational output; and the top 20% accounts for 80% of organizational output and organizational outperformance. Synthesis of ‘star’ research, findings, and amongst other outperformance evidence indicates that simply adding a star performer to a team can boost the effectiveness of the team members by 5-15%. Therefore, it is necessary to understand how to identify and assess HIPO in order to help develop them and help your organization achieve performance maximization in this dynamic globalized economy

Influences on Throughput and Latency in Stream Programs

Vu Thien Nga Nguyen and Raimund Kirner, 'Influences on Throughput and Latency in Stream Programs' paper presented at the 2nd Workshop on Feedback-Directed Compiler Optimization for Multi-Core Architectures. Berlin, Germany. 22 January 2013Stream programming is a promising approach to execute programs on parallel hardware such as multi-core systems. It allows to reuse sequential code at component level and to extend such code with concurrency-handling at the communication level. In this paper we investigate in the performance of stream programs in terms of throughput and latency. We identify factors that affect these performance metrics and propose an efficient scheduling approach to obtain the maximal performance

Transactions Costs and Point-Nonpoint Source Water Pollution Trading

The implications of transactions costs for the performance of water pollution trading involving point and nonpoint sources are examined. The analysis focuses on the impacts of transaction costs on different classes of trading partners and its consequence on the trading equilibrium. The model of point-nonpoint water pollution trading in the context of the total maximum daily loads explicitly incorporates transactions costs for both buying and selling exchanges of nonpoint source and point source permits. Transactions costs unarguably reduce the optimal level of trades in both types of permits compared to the costless trade case.Environmental Economics and Policy,

Magnetic field dependence of the many-electron states in a magnetic quantum dot: The ferromagnetic-antiferromagnetic transition

The electron-electron correlations in a many-electron (Ne = 1, 2,..., 5) quantum dot confined by a parabolic potential is investigated in the presence of a single magnetic ion and a perpendicular magnetic field. We obtained the energy spectrum and calculated the addition energy which exhibits cusps as function of the magnetic field. The vortex properties of the many-particle wave function of the ground state are studied and for large magnetic fields are related to composite fermions. The position of the impurity influences strongly the spin pair correlation function when the external field is large. In small applied magnetic field, the spin exchange energy together with the Zeeman terms leads to a ferromagnetic-antiferromagnetic(FM-AFM) transition. When the magnetic ion is shifted away from the center of the quantum dot a remarkable re-entrant AFM-FM-AFM transition is found as function of the strength of the Coulomb interaction. Thermodynamic quantities as the heat capacity, the magnetization, and the susceptibility are also studied. Cusps in the energy levels show up as peaks in the heat capacity and the susceptibility.Comment: 16 pages, 24 figure

Cyclotron resonance of a magnetic quantum dot

The energy spectrum of a one-electron quantum dot doped with a single magnetic ion is studied in the presence of an external magnetic field. The allowed cyclotron resonance (CR) transitions are obtained together with their oscillator strength (OS) as function of the magnetic field, the position of the magnetic ion, and the quantum dot confinement strength. With increasing magnetic field a ferromagnetic - antiferromagnetic transition is found that results in clear signatures in the CR absorption. It leads to discontinuities in the transition energies and the oscillator strengths and an increase of the number of allowed transitions.Comment: 11 pages, 14 figure