Abstract
The application of partial nitritation and anammox processes (PN/A) to remove nitrogen can improve the energy efficiency of wastewater treatment plants (WWTPs) as well as diminish their operational costs. However, there are still several limitations that are preventing the widespread application of PN/A processes in urban WWTPs such as: (a) the loss of performance stability of the PN/A units operated at the sludge line, when the sludge is thermally pretreated to increase biogas production; (b) the proliferation of nitrite-oxidizing bacteria (NOB) in the mainstream; and (c) the maintenance of a suitable effluent quality in the mainstream. In this work, different operational strategies to overcome these limitations were modelled and analyzed. In WWTPs whose sludge is thermically hydrolyzed, the implementation of an anerobic treatment before the PN/A unit is the best alternative, from an economic point of view, to maintain the stable performance of this unit. In order to apply the PN/A process in the mainstream, the growth of ammonia-oxidizing bacteria (AOB) should be promoted in the sludge line by supplying extra sludge to the anaerobic digesters. The AOB generated would be applied to the water line to partially oxidize ammonia, and the anammox process would then be carried out. Excess nitrate generated by anammox bacteria and/or NOB can be removed by recycling a fraction of the WWTP effluent to the biological reactor to promote its denitrification.
Highlights
Improving the energy efficiency of urban wastewater treatment plants (WWTPs) is a crucial step for decreasing their operating costs and environmental impact
Siegrist et al [7] reported that a 52% reduction in the total energy consumption of WWTPs could be achieved through the implementation of partial nitritation and anammox (PN/A) processes in the sludge line
This work focuses on proposing, modelling, and analyzing different operational strategies to overcome the most critical aspects limiting the application of PN/A processes in urban WWTPs such as: (a) the loss of performance stability of the PN/A units operated at the sludge line, when the sludge is thermally pretreated; (b) the proliferation of nitrite-oxidizing bacteria (NOB) in the mainstream; (c) the challenge of obtaining a suitable effluent quality in the mainstream
Summary
Improving the energy efficiency of urban wastewater treatment plants (WWTPs) is a crucial step for decreasing their operating costs and environmental impact. In order to overcome these drawbacks, different control strategies have been proposed to avoid NOB proliferation [16], while the combination of PN/A processes with others involved in the nitrogen cycle seems to be the way to improve effluent quality [17] At this moment, there is only one WWTP where a combination of partial nitritation, anammox, and denitrification processes is applied at full scale to remove nitrogen [18]. This work focuses on proposing, modelling, and analyzing different operational strategies to overcome the most critical aspects limiting the application of PN/A processes in urban WWTPs such as: (a) the loss of performance stability of the PN/A units operated at the sludge line, when the sludge is thermally pretreated; (b) the proliferation of NOB in the mainstream; (c) the challenge of obtaining a suitable effluent quality in the mainstream
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
