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The relative locations of AOB, NOB, and DNB were examined for three different kinds of carriers in two types of hybrid biofilm process configurations: integrated fixed-film activated sludge (IFAS) and moving bed biofilm reactor (MBBR) processes. IFAS water resource recovery facilities (WRRFs) used Anodkalness K1 carriers (KC) at Broomfield, Colorado, USA and polypropylene resin carriers (RC) at Fukuoka, Japan, while MBBR WRRFs used KC carriers at South Adams County, Colorado, UsA and sponge carriers (SC) at Saga, Japan. Influent COD to N ratios ranged from 8:1 to 15:1. The COD and BOD removal efficiencies were high (96%–98%); NH4+-N and TN removal efficiencies were more varied at 72%–98% and 64%–77%, respectively. The extent of TN removal was higher at high SRT, high COD:N ratio and low DO concentration in the anoxic tank. In IFAS, RC with high specific surface area (SSA) maintained higher AOB population than KC. Sponge carriers with high SSA maintained higher overall bacteria population than KC in MBBR systems. However, the DNB were not more abundant in high SSA carriers. The diversity of AOB, NOB, and DNB was fairly similar in different carriers. Nitrosomonas sp. dominated over Nitrosospira sp. while denitrifying bacteria included Rhodobacter sp., Sulfuritalea sp., Rubrivivax sp., Paracoccus sp., and Pseudomonas sp. The results from this work suggest that high SRT, high COD:N ratio, low DO concentration in anoxic tanks, and carriers with greater surface area may be recommended for high COD, BOD and TN removal in WRRFs with IFAS and MBBR systems. [ABSTRACT FROM AUTHOR]

In side-by-side tests with high nitrogen wastewaters (483-1096 mg N/L), it was shown that an attached-growth media system more effectively removed nitrogen than did a suspended-growth system. The attached-growth system better handled the high nitrogen loading concentrations as calculated by the specific annamox activities (SAA) of the two systems. Moreover, the attached-growth medium was able to retain the anammox culture within the system. Based on these results, attached-growth was chosen for additional investigation of the effect of acetate in short- and long-term studies. In a short-term experiment, acetate concentrations of 0.25 and 0.5 mM did not affect the anammox bacteria activity. However, in a long-term experiment, the addition of acetate at 0.25 mM decreased the ammonium oxidation rate. The results from this study suggest that attached-growth systems show more promise for use in the field than suspended-growth systems. [ABSTRACT FROM AUTHOR]

We investigated the effects of free ammonia (FA) and free nitrous acid (FNA) concentrations on the predominant ammonia-oxidizing bacteria (AOB) and the emission of nitrous oxide (NO) in a lab-scale sequencing batch reactor for partial nitrification. The reactor was operated with stepwise increases in the NH loading rate, which resulted in a maximum FA concentration of 29.3 mg-N/L at pH 8.3. Afterwards, FNA was increased by a gradual decrease of pH, reaching its maximum concentration of 4.1 mg-N/L at pH 6.3. Fluorescence in situ hybridization indicated that AOB remained predominant during the operation, achieving specific nitrification rates of 1.04 and 0.99 g-N/g-VSS/day at the highest accumulations of FA and FNA, respectively. These rates were in conjunction with partial nitrification efficiencies of >84%. The NO emission factor of oxidized NH was 0.90% at pH 7.0, which was higher than those at pH 8.3 (0.11%) and 6.3 (0.12%), the pHs with the maximum FA and FNA concentrations, respectively. High-throughput sequencing of 16S ribosomal RNA genes showed that increases in FNA drastically changed the predominant AOB species, although increased FA produced no significant changes. This study demonstrates that the FNA concentration and pH are the main drivers that determine the predominant AOB species and NO-emission in a partial nitrifying bioreactor. [ABSTRACT FROM AUTHOR]