Abstract
Nitrogen pollution in reservoirs has received increasing attention in recent years. Although a number of aerobic denitrifying strains have been isolated to remove nitrogen from eutrophic waters, the situation in oligotrophic water environments has not received significant attention. In this study, a mixed aerobic denitrifying consortium screened from reservoir samples was used to remove nitrogen in an oligotrophic denitrification medium and actual oligotrophic source water. The results showed that the consortium removed 75.32% of nitrate (NO3−-N) and 63.11% of the total nitrogen (TN) in oligotrophic reservoir water during a 24-h aerobic cultivation. More initial carbon source was helpful for simultaneous removal of carbon and nitrogen in the reservoir source water. NO3−-N and TN were still reduced by 60.93% and 46.56% at a lower temperature (10 °C), respectively, though the rates were reduced. Moreover, adding phosphorus promoted bacterial growth and increased TN removal efficiency by around 20%. The performance of the immobilized consortium in source water was also explored. After 6 days of immobilization, approximately 25% of TN in the source water could be removed by the carriers, and the effects could last for at least 9 cycles of reuse. These results provide a good reference for the use of aerobic denitrifiers in oligotrophic reservoirs.
Highlights
In recent years, with the limitations of the groundwater extraction, reservoirs are gradually becoming the major water supply sources in many big cities [1]
The nitrogen removal performance of the mixed aerobic denitrifying in denitrification spectrophotometric methods, respectively
The mixed aerobic denitrifying consortium used in this study had remarkable nitrogen removal effects in actual oligotrophic source water, which was limited in all types of nutrients compared to the denitrification medium, and a suitable increase in the initial total organic carbon (TOC) may be beneficial for the denitrification effects, and the simultaneous removal of carbon and nitrogen
Summary
With the limitations of the groundwater extraction, reservoirs are gradually becoming the major water supply sources in many big cities [1]. Human activities and economic development have led to widespread nitrogen pollution in natural waters, including lakes and reservoirs. The excess nitrogen in reservoir waters causes eutrophication [2], and enhances the formation of nitrogen-containing disinfection byproducts (N-DBPs) during chlorination, which poses a great risk to human health [3,4]. Administration of China (SEPA) promulgated stricter Environmental Quality Standards for Surface. Water (GB3838-2002), in which the concentration of the total nitrogen in Grade III source water is required to be less than 1.0 mg/L. Most of the reservoirs in China fail to meet this standard. Removing nitrogen, especially nitrate, from natural water has become an important problem that requires solutions urgently
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