Conference Papers

Granular sludge consist of bacterial aggregates that are much more compact than traditional activated sludge, thus offering numerous advantages such as high biomass retention, good settling ability and simultaneous removal of organic load and nutrients. In a laboratory scale sequencing batch reactor (SBR) granules were cultured under aerobic conditions. To enhance the growth of granular sludge the SBR was operated with very short sedimentation and draw phases resulting in the washout of slow settling biomass (anaerobic feeding – 45 min, aerobic reaction – 11 h, settling – 5 min and effluent withdrawal – 10 min). The reactor was inoculated with conventional activated sludge and fed with dairy industry wastewater with high organic and nutrients load. The first aerobic granular structures, having 67–556 m in diameter, were observed after 5 days. After 25 days, they reached diameters between 513 m and 1276 m and increased gradually up to diameters of 2 mm by the end of the experiment. Treatment performances increased along with the growth of granules size.

Biological wastewater treatment processes have a crucial importance to the modern world, due to the ever increasing need of sanitation and pollution control in urbanized areas. Aerobic granular sludge represents an alternative for the conventional biological system. Recent studies have greatly expanded the vision on aerobic granular sludge morpho-functional and microbiological peculiarities and their influence on wastewater treatment performance and behavior. The microbial composition of the granules obtained in a sequencing batch reactor – SBR, were characterized using microscopy and molecular biology techniques. Scanning electron microscopy investigations,revealed in sights into the granules morphology and structure: size, pore dimensions, presence of filamentous bacteria. Molecular biology techniques were used to determine the presence and abundance of biotechnologically useful bacteria (nitrifiers, denitrifiers) in the sludge granules samples. The samples were subjected to PCR amplification using the following primers: specific for ammonium oxidizing bacteria; specific for nitrite oxidizing bacteria; universal bacteria primers. The results indicated the presence of nitrifying bacteria specific genes belonging to Nitrosomonas sp., Nitrospira sp., and Nitrobacter sp., species responsible for nitrification. The abundance and diversity of identified microbial species were correlated with the treatment performances registered for the operational sequencing batch reactor.

Aerobic granular sludge has several advantages over conventional activated sludge flocs such as fast settling ability, high biomass retention and ability to withstand high organic loading including potential toxic substrates, leading towards a compact reactor system – aerobic granular sludge sequential batch reactor (AGSBR). Aerobic granules have been successfully cultivated, previously, in SBR systems from flocculated activated sludge fed with synthetic medium with acetate as the sole carbon source or with real municipal wastewater. The main objective of this study was to investigate the possibility of an aerobic granular system to simultaneously remove the organic loading, nitrogen and phosphorus content. The experiments were performed in a SBR reactor with a hydraulic reaction time of 12 hours at loading rates of up to 3.0 kg m-3 day-1 COD and 0,2 kg m-3day-1 of N-NH4+. Compact granules with good settling ability were maintained during the experimental period and high COD removal but ordinary global nitrogen and phosphorus removal efficiency were registered. Aerobic granules possess high activity, compact structure and good settling ability, and have the potential to simultaneously treat wastewater with high organic and ammonium loading in sequential system at relatively low hydraulic retention times.

Many recent studies in the field of wastewater treatment and environmental protection have focused their attention on the possibility of obtaining aerobic granular sludge in order to develop new innovative wastewater treatment technologies. Compared to conventional activated sludge wastewater treatment plants, aerobic granular technology represent a novel alternative offering numerous advantages such as high biomass retention, good settling ability and simultaneous removal of organic load and nutrients. The main focus of research was to evaluate granules formation and evolution of treatment performances during startup and steady state conditions. Two lab scale sequencing batch bioreactors were used in the experiment: one of the bioreactors (D) was inoculated with conventional activated sludge while the other one (GM) was inoculated with crushed aerobic granular sludge. Both bioreactors were fed with dairy industry wastewater with high organic and nutrients load (CODCr = 1723 – 3550 mg O2/L, BOD5 = 492 – 1806 mgO2/L; NH4+= 64.6 - 114 mg/L, P tot = 5.04 – 21.5 mg/L) and underwent the same operational cycle: anaerobic feeding (45min), aerobic reaction (11 h), settling (5min.) and effluent withdrawal (10 min). The first granular structures were observed after 5 days (10 treatment cycles) with a diameter of 67 to 556 μm in D bioreactor and with 392 to 1200 μm in GM bioreactor. After 25 days the granules in D bioreactor increased significantly reaching diameters between 513 μm and 1276 μm. By the end of the experiment the granules reached 2 mm in diameter. The granules in GM bioreactor increased to 764-1482 μm and reached up to 4 mm in diameter by the end of the experiment. Treatment performances increased along with the growth of granules size.

Phenol can be removed from wastewater by biological treatment, which is generally preferred to physical or chemical treatment methods, because of lower costs and the possibility of complete mineralization. Many bacteria are capable of using aromatic compounds such as phenol as the sole source of both carbon and energy. While phenol, wastewater are usually treated in continuous activated sludge processes, these systems are known to be sensitive to high phenol loading rates and to fluctuations in phenol loading. Formation of microbial granules from activated sludge flocs, under aerobic conditions is currently an active area of investigation for developing new generation wastewater treatment plants for high strength organic wastewater, bioremediation of toxic aromatic pollutants including phenol, toluene, pyridine and textile dyes, removal of nitrogen, phosphate and adsorption of heavy metals. Aerobic granules have been successfully cultivated, previously, in SBR systems from flocculated activated sludge fed with acetate as the sole carbon source. The main objective of this study was to investigate how phenol loading affected the structure and activity of aerobic granules. The results indicated that phenol loading exerted a profound influence on the structure and activity of the aerobic granules. Compact granules with good settling ability were maintained at loading up to 3.0 kg phenol m-3 day-1, and structurally weakened granules were observed at the highest loading of 3.7 kg phenol m-3 day-1. Phenol-degrading aerobic granules possess high activity, compact structure and good settleability, and have the potential to treat wastewater with high phenol loading in sequential system at relatively low hydraulic retention times.