Community structure of denitrifying and total bacteria during nitrogen accumulation in an ammonia-loaded biofilter.

AIMS: To obtain insight into the complex behaviour of denitrifying and total bacterial groups during the nitrogen accumulation process in an ammonia-loaded biofiltration system. METHODS AND RESULTS: Denitrifying and total bacterial communities in a laboratory-scale rockwool biofilter with intermittent water recirculation were analysed by using denaturing gradient gel electrophoresis targeting nosZ and metabarcoding sequencing of the 16S rRNA gene. Gene abundance was evaluated by quantitative PCR. The nosZ number increased from 6·59 × 106 to 3·33 × 108 copies per gram dry sample over the 436 days of operation, during which nitrogen mass balance errors increased to 39%. The nosZ sequences associated with the genera Castellaniella, Hyphomicrobium and Pseudomonas were detected. Metabarcoding sequencing analysis indicated that the proportions of the genera for which at least one denitrifying strain or species possessing nosZ had been characterized corresponded well to the nitrogen loss. In addition, the genus Nitrosococcus (γ-proteobacteria) increased its relative abundance at days 317 and 436. CONCLUSIONS: The increased proportion of denitrifying bacteria in this ammonia-loaded biofiltration system could be related to the nitrogen loss. SIGNIFICANCE AND IMPACT OF THE STUDY: These results will help to clarify the complex behaviour of nitrifiers and denitrifiers within ammonia-loaded biofiltration systems.

Responses of community structure of amoA-encoding archaea and ammonia-oxidizing bacteria in ammonia biofilter with rockwool mixtures to the gradual increases in ammonium and nitrate.

AIMS: To investigate community shifts of amoA-encoding archaea (AEA) and ammonia-oxidizing bacteria (AOB) in biofilter under nitrogen accumulation process. METHODS AND RESULTS: A laboratory-scale rockwool biofilter with an irrigated water circulation system was operated for 436 days with ammonia loading rates of 49-63 NH(3) g m(-3) day(-1). The AEA and AOB communities were investigated by denaturing gradient gel electrophoresis, sequencing and real-time PCR analysis based on amoA genes. The results indicated that changes in abundance and community compositions occurred in a different manner between archaeal and bacterial amoA during the operation. However, both microbial community structures mainly varied when free ammonia (FA) concentrations in circulation water were increasing, which caused a temporal decline in reactor performance. Dominant amoA sequences after this transition were related to Thaumarchaeotal Group I.1b, Nitrosomonas europaea lineages and one subcluster within Nitrosospira sp. cluster 3, for archaea and bacteria, respectively. CONCLUSIONS: The specific FA in circulation water seems to be the important factor, which relates to the AOB and AEA community shifts in the biofilter besides ammonium and pH. SIGNIFICANCE AND IMPACT OF THE STUDY: One of the key factors for regulating AEA and AOB communities was proposed that is useful for optimizing biofiltration technology.

Bacterial community dynamics in aerated cow manure slurry at different aeration intensities.

AIMS: This study aimed to characterize microbial community dynamics in aerated cow manure slurry at different aeration intensities. METHODS AND RESULTS: Batch aerobic treatments were set up in 5-l jar fermentor, each containing 3 l of manure slurry; the slurries were subjected to low, medium and high (50, 150 and 250 ml min(-1), respectively) aeration for 9 days. Microbial community composition was determined using terminal restriction fragment length polymorphism and a clone library targeting 16S rRNA genes. High and medium aeration accelerated organic carbon degradation in parallel with the degree of aeration intensity; however, 90% of the initial total organic carbon was retained during low-aeration treatment. During the active stages of organic carbon decomposition, clones belonging to the class Bacilli accumulated. Moreover, Bacilli accumulation occurred earlier under high aeration than under medium aeration. CONCLUSIONS: Organic matter degradation was mainly governed by a common microbial assemblage consisting of many lineages belonging to the class Bacilli. The timing of community development differed depending on aeration intensity. SIGNIFICANCE AND IMPACT OF THE STUDY: This study reports on changes in several environmentally important parameters and the principal microbial assemblage during the pollution-reducing phase of cattle manure aeration treatment.

Bacterial community dynamics during reduction of odorous compounds in aerated pig manure slurry.

AIMS: To study the microbial community responsible for the reduction of the polluting load during aerobic digestion of pig slurry. METHODS AND RESULTS: We analysed bacterial succession by nonculture-based methods and determined the physicochemical parameters and polluting substances during 6 days of aerobic digestion. The bacterial subpopulations evolved by aeration, predominantly Bacillus spp., degraded organic matter and vigorously consumed oxygen, as indicated by low oxidation-reduction potential (ORP). In this phase, the volatile fatty acid (VFA) levels drastically decreased, and VFAs were almost depleted on day 4. Simultaneously, the ammonia concentration decreased to its lowest level on day 4; thereafter, it increased until the end of the process. After the decrease in the total organic carbon content in the supernatant of the decomposed slurry, the ORP increased (approximately 0 mV), and the microbial community showed an abundance of lineages belonging to the phylum Proteobacteria. CONCLUSIONS: Bacillus was the predominant member of the bacterial community driving the VFA-removal process. Their predominance was related to the presence of available carbon, including VFAs and changes in ORP. SIGNIFICANCE AND IMPACT OF THE STUDY: Information on the relationships among the involved microbes, polluting materials and physicochemical parameters will aid process design and retrofitting of the process.

Enhancement of the thermophilic stage in cattle waste composting by addition of tofu residue.

The microbial degradation and temperature rise during the composting of a cattle waste and rice straw mixture blended with tofu (soybean curd) residue was investigated using an insulated and unheated in-vessel composter (effective volume, 12 1) and a static pile with passive aeration. The addition of 11% (dry weight basis) of tofu residue shortened the time required for temperature to reach the thermophilic phase and increased the duration of the temperatures above 55 degrees C significantly, but the maximum temperature was not affected by the additive level. As shown by the change in BOD, most of the easily biodegradable matter in the tofu residue was consumed during 12 days of composting. The same results were observed in the temperature profile of the static pile with passive aeration. Tofu residue addition yielded a higher maximum temperature and a nearly two times longer duration of temperatures above 55 degrees C in almost all locations of the pile. The use of tofu residue as a co-composting material would promote thermophilic degradation throughout the entire composting mass.