Removal of nitrogen using different carbon source

• Main Author: Chen, Yimin.
• Other Authors: Sun Delai, Darren
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Environmental engineering::Water treatment
• Online Access: http://hdl.handle.net/10356/15935
• Institution: Nanyang Technological University

Nutrient is essential for plant growth. However, presence of excessive nutrient will result in eutrophication, which is harmful to the ecosystem and environment. Therefore, removal of nitrogenous compound in wastewater is necessary. Denitrification is commonly used in activated sludge process for removal of nitrate, which combined with nitrification, converting ammonium to nitrate. To understand the removal of nitrogen, an experimental setup involving two batch reactors, with and without organic carbon source were carried out. The organic carbon source used was methanol. The experimental result had shown that carbon source is essential for denitrification. Some important parameters to optimize denitrification process are: DO concentration to be less than 0.3mg/L, pH range between 6.5 to 8.5, temperature range of 20°C to 30°C. During the experiment, the analysis tests involved were NH4+, NO2- and NO3- concentration, pH value, TSS, VSS, SVI, TOC, particle size and SEM. From the batch reactor containing methanol, we had observed the presences of gas bubbles, indicating denitrification had took placed. These bubbles would entrap in solid and hinder settleability causing particles to remain in suspension. As a result, a decrease in membrane flux with time was observed. This phenomenon was contributed due to an increased in resistance and fouling of membrane. Growth of irregular, brown and large floc particles were observed. Despite of the entrapment of gas bubbles, flocs settled more readily compared to reactor without carbon source. Adaptation of environment for bacteria was about 100days. There was no significant growth in particle size. Removal of NH4+ was a slower process compared to removal of NO3-. As a result, NH4+ accumulation could be observed and gradual decrease in NH4+ concentration when new substrate was not added. It took about 3 days for 80% removal of NH4+. After new substrate was added, a rapid decrease in NO3- concentration was observed at the first 6 hours. Removal efficiency of NO3- could reach up to 100%. There was no or little intermediate product (NO2-) generated during denitrification. There was an increase in alkalinity and pH when denitrification occurred. Inorganic carbon was produced during denitrification, increasing IC concentration and organic carbon was consumed causing a decline in TOC. Through SEM, presence of filamentous, coccus and bacillus bacteria could be observed.