ABSTRACT
This study focuses on the enhancement of aerobic granulation and biological nutrient removal maintenance treating domestic wastewater. Two sequencing batch reactors (SBRs) were inoculated with either only floccular sludge (100%-floc SBR) or supplemented with 10% crushed granules (90%-floc SBR). Granules developed in both reactors. The 100%-floc SBR achieved 75% of nitrogen and 93% of phosphorus removal at the end of the performance, but some floccular sludge remained in the system. The 90%-floc SBR became fully granulated and finished with 84% and 99% of nitrogen and phosphorus removal, respectively. Regarding biological phosphorus removal, nitrite was identified as an inhibitor of the process. Nitrite levels lower than 5 mg N-NO2-L(-1) were used for anoxic phosphate uptake while higher concentrations inhibited the process.
Subject(s)
Family Characteristics , Nitrogen/isolation & purification , Phosphorus/isolation & purification , Sewage/microbiology , Waste Disposal, Fluid , Water Purification/methods , Aerobiosis , Anaerobiosis , Batch Cell Culture Techniques , Biodegradation, Environmental , Biomass , Bioreactors , Denitrification , Fatty Acids, Volatile/analysis , Flocculation , Glycogen/metabolism , Nitrates/analysis , Nitrification , Nitrites/analysis , Oxidation-Reduction , Particle Size , Polyphosphates/metabolism , Quaternary Ammonium Compounds/metabolismABSTRACT
Aerobic granulation is a novel and promising technology for wastewater treatment. However, long start-up periods required for the development of granules from floccular sludge, and the loss of biomass in this period leading to poor nutrient removal performance are key challenges. In a recent study the addition of crushed granules to a floccular sludge significantly reduced the start-up period, and also maintained the nutrient removal performance during granulation. In this study, we examined the mechanisms responsible for the fast granulation from a mixture of floccular and granular sludges. Fluorescent microbead particles (4 µm diameter) were successfully applied to differentially label the surfaces of floccular and crushed granular aggregates. Labelled flocs and crushed granules were added to a laboratory scale wastewater treatment reactor, and the granule formation process was monitored using confocal laser scanning microscopy over an 80 day period. Flocs were observed to attach to the surface of the seeding granules, resulting in reduced biomass washout during granulation. This mechanism not only reduces the granulation period, but also maintains the nutrient removal performance of the reactor. The results indicate that the granules acted as nuclei for floccular particle attachment, which accelerated granule formation.
