Concerns discharges containing high concentrations of ammonia are increasing. Indeed, discussions and guidelines on these releases are accentuated by the decision makers in Canada and Quebec. Although, there are different biological methods to remove ammonia nitrogen, few of them are effective in cold wastewater as encountered in Quebec. In terms of physicochemical methods, there are various disadvantages, including reagents consumption, among others.
In this perspective, this research project aims to study a new decentralized treatment configuration for the residential sector (advanced secondary treatment system) allowing ammonia nitrogen removal in water. The system should meet the classification requirements of advanced secondary treatment system to meet up a real market need. To do so, four pilot units designed under the principles of a trickling filter have been built and powered by a synthetic wastewater. The use of a natural zeolite as an ion exchange resin is considered. The process is to capture and fasten ammonium ions in continuous operation mode on the zeolite. In parallel, the autotrophic bacteria attached to the media provide biological nitrification while favoring media bioregeneration. To interpret these phenomena involved, one of the four units is composed exclusively of granite stone used as the control unit of the study. The considered benefits of this research are: a) minimize risks of acute and chronic toxicity because of nitrogen compounds presence in streams; b) develop a reliable advanced secondary treatment decentralized for ammonia nitrogen removal. Parameters monitored in laboratory are ammonium nitrogen (NH4 +), pH, nitrite (NO2 -) and nitrate (NO3 -), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total suspended solids (TSS), alkalinity, temperature and dissolved oxygen (O2).
Results of this project suggest that variations in daily surface flow applied to zeolite filters influence nitrification and ammonia fixation on the media. Indeed, flow rates from 14,8 to 51,5 L / (m2/d) ensure nitrification as an average percentage of 63% of influent load. Subsequently, for flow rates from 42 to 114 L / (m2/d), fixing takes over on nitrification for an average of 49% of entry head and finally when the daily surface flow is greater than 100 L / (m2/d), the filter is allowing more ammonia than it nitrified or adsorbs. Moreover, we see that the filter provides better performance (nitrification and/or fixation) on the zeolite first 15 cm. Indeed, over 183 days of filters continuous operation, there has been a 72% average reduction of ammonia nitrogen load on this thickness. Regarding organic matter (DBO5), for an average concentration of 62 mg-O2/L, filters degrade completely this portion from the third week of operation. Zeolite offers better efficiency than the granite stone. An average gain of 25% (for BOD5) is observed for the first 118 days of operation. The entire experimental campaign was conducted at temperatures ranging from 9 to 16 °C. No temperature difference is observed between zeolite and granite. Finally, alkalinity, pH, and dissolved oxygen were not limiting factors in this study.
| Date | 21 Sept 2012 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Frédéric Monette (Supervisor) |
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Petit, D. (Author),
Monette (Supervisor),
21 Sept 2012Student thesis: Master's thesis › Master in Engineering: Engineering