TREATMENT OF HIGH-AMMONIA WASTE STREAM USING A SINGLE SUBMERGED ATTACHED GROWTH BIOREACTOR - PERFORMANCE AND NITRIFYING COMMUNITY ANALYSIS
Abstract:This study investigated the nitrifying community structure in a single-stage submerged attached growth bioreactor (SAGB, sand filter) that successfully achieved stable nitrogen removal over nitrite of a high strength ammonia wastewater. The reactor was operated with intermittent aeration and external carbon addition (methanol). With influent ammonia and TKN range from 537 to 968 mg/L and 643 to 1510 mg/L, respectively, 85% nitrogen removal was obtained and effluent was dominated with nitrite (NO2/NOx > 0.95). Nitrifying community analysis using fluorescence in situ hybridization (FISH ) with a hierarchical set of probes targeting known ammonia-oxidizing bacteria (AOBs) within beta-proteobacteria showed that the AOB community of the biofilter consists nearly entirely of members of the Nitrosomonas europaea/eutropha and the Nitrosococcus mobilis lineages. Image analysis of FISH pictures was used to quantify the identified AOBs and it was estimated that Nitrosomonas europaea/eutropha-like AOBs account for 4.3% of the total volume of the biofilm while Nitrosococcus mobilis-like AOBs make up 1.2%; these numbers sum up to a total AOB fraction of 5.5% of the total volum on the biofilm. NOBs were not detectable in the biofilm samples with probes for either Nitrospira sp. or Nitrobacter sp., which indicates that NOB were either absent from the biofilters or present in numbers below the detection limit of FISH (<0.1% of the total biofilm). Nitrite oxidizers were likely out-competed from the systems because the aeration time length (from intermittent aeration) was not sufficient for the DO-sensitive NOBs to be released from the competition for oxygen with other heterotrophs and AOBs. The nitrogen removal via nitrite in a SAGB reactor described in this study is applicable for high ammonia strength wastewater treatment such as centrate or industrial wastes, where very low effluent nitrogen limit may not be required.
Document Type: Research Article
Publication date: January 1, 2007
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