| dc.description.abstract | Nutrient mishandling of wastewater poses a substantial threat to environmental stability as a result of the continuous accumulation of nitrogen-rich effluent in the surface waterbody, which leads to eutrophication and disrupts the equilibrium of aquatic life. Therefore, it is necessary to address the problem of environmental contamination resulting from the release of nutrients, mainly Nitrogen and Phosphorus into rivers, lakes etc. Among several biological treatment processes, anaerobic ammonium oxidation (ANAMMOX) has been recognized as a very promising technique for autotrophic nitrogen removal. This process is more cost effective than conventional nitrification-denitrification processes due to its reduced sludge production, no carbon use and partial aeration requirement. However, despite the full-scale adoption of anammox processes in the side stream, there are still numerous persistent problems in mainstream wastewater removal. The primary challenge is the adaptation of anammox species to work efficiently at low temperatures, given that the temperature of incoming wastewater in Europe typically ranges from 10°C to 20°C.
The study aimed to accomplish four objectives - to establish a UASB anammox reactor at mesophilic temperatures, analyzing substrate concentrations to understand reactor dynamics, track performance by lowering temperature stepwise, and conduct a literature review on the mainstream anammox process. While three of the goals were achieved, it was not feasible to reduce the temperature owing to the time limitations imposed by slow reactor process that had to be faced during the experiment.
An Upflow Anaerobic Sludge Blanket (UASB) reactor was set up at a mesophilic temperature (35°C) and was operational for 57 days. The reactor was fed with synthetic water in two phases. Phase I (Days 1 to 36) involved feeding the reactor with an influent substrate ratio of 1:1 (25 mg/L NH4-N and 25 mg/L NO2-N), while in phase II (day 37 to 57) NO2-N concentration was changed to 50 mg/L, resulting in a substrate ratio of 1:2. In the first phase, the denitrifiers were dominated by reducing over 90% of NO2-N into N2 gas with minimal NH4-N removal through anammox process. Provided that the first phase encountered microbe washout. However, phase II demonstrated superior removal with a modified influent ratio of 1:2. On the 57th day, the reactor observed approximately 78% NH4-N removal through the anammox process.
It is concluded that the initial stage of phase I was dominated by heterotrophs, and it ultimately failed without anammox activity as a result of the microbial washout. Despite the fact that the second phase was exhibiting satisfactory removal at the end of the study, there was a time constraint to stabilize the process and initiate the temperature test. | |
