Abstract
The start-up and performance of the completely autotrophic nitrogen removal via nitrite (CANON) process were examined in a sequencing batch reactor (SBR) with intermittent aeration. Initially, partial nitrification was established, and then the DO concentration was lowered further, surplus water in the SBR with high nitrite was replaced with tap water, and continuous aeration mode was turned into intermittent aeration mode, while the removal of total nitrogen was still weak. However, the total nitrogen (TN) removal efficiency and nitrogen removal loading reached 83.07% and 0.422 kgN/(m3·d), respectively, 14 days after inoculating 0.15 g of CANON biofilm biomass into the SBR. The aggregates formed in SBR were the mixture of activated sludge and granular sludge; the volume ratio of floc and granular sludge was 7 : 3. DNA analysis showed that Planctomycetes-like anammox bacteria and Nitrosomonas-like aerobic ammonium oxidization bacteria were dominant bacteria in the reactor. The influence of aeration strategies on CANON process was investigated using batch tests. The result showed that the strategy of alternating aeration (1 h) and nonaeration (1 h) was optimum, which can obtain almost the same TN removal efficiency as continuous aeration while reducing the energy consumption, inhibiting the activity of NOB, and enhancing the activity of AAOB.
Highlights
Biological nitrogen removal processes are generally used for the elimination of nitrogen from wastewater
The discovery of the anaerobic ammonium oxidation process has revolutionized the removal of nitrogen from wastewater that contains high amounts of nitrogen and has low carbon to nitrogen ratios (C/N) [3]
The anammox process involves the oxidation of ammonia into nitrogen gas, with nitrite serving as an electron acceptor in the absence of oxygen and organic carbon compounds [4]
Summary
Biological nitrogen removal processes are generally used for the elimination of nitrogen from wastewater. Wastewater with low carbon to nitrogen ratios (C/N), such as supernatants of anaerobic sludge digesters, landfill leachate, and special industrial wastewater, makes the conventional nitrification and heterotrophic denitrification processes more difficult [1, 2]. The discovery of the anaerobic ammonium oxidation (anammox) process has revolutionized the removal of nitrogen from wastewater that contains high amounts of nitrogen and has low C/N [3]. The anammox process involves the oxidation of ammonia into nitrogen gas, with nitrite serving as an electron acceptor in the absence of oxygen and organic carbon compounds [4]. AerAOB aonnxitidrdifiNizceOast2Ni−oHni)n4,+twothoNiNc2hO[i1s22−f]o.ulCnlodAweNerdaOebNryoAbisincoAcnoOenBdoifctoitonhnvesear(uit.iteno.g,tprNoaprHthi4ai+cl nitrogen removal processes that maintain AerAOB and AnAOB in a single reactor by controlling low DO levels [13]
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