Isolation, Application Of Contraceptive Wastewater Superior Strains And Aerobic Granules Cultivation

Treatment of contraceptive wastewater with traditional methods has some problems that the effluent can't meet the discharge standard and in turn lead to serious pollution. In order to solve the problem, superior strains membrane bioreactor (MBR) and aerobic granules were used to treat contraceptive wastewater. 10 superior strains were isolated from activated sludge of contraceptive factory. Treatments of contraceptive wastewater by MBR technology were compared with and without the present of superior strains. It was indicated that the separation membrane facilitate the use of superior strains in wastewater treatment. Based on the successful cultivation, aerobic granules were used to treat contraceptive wastewater. The optimal conditions and results were discussed.10 superior strains named YS1, YS2,…, YS10 were isolated from activated sludge of contraceptive factory. Based on analyses of their morphology and 16S rDNA sequence, the bacteria were identified as five strains that Pseudomonas aeruginosa, Brevibacillus parabrevis, Acinetobacter lwoffii, Acinetobacter baumannii, Brevibacillus brevis. It was found that addition of superior strains needed less density of bio-cultures and degradation time than that without superior strains. At the same time, the results obtained with superior microbial cultures were better than those without superior microbial at different pH and temperatures.The MBR operation results showed that degradation ratios of COD was 90% with the addition of superior strains while only 80% without the superior strains. At the same time, the NH₃-N degradation ratios obtained from the superior strains MBR were 10% higher than those obtained from the MBR without superior strains due to the activity improvement of heterotrophic. 60 days operation indicated that retention function of membrane kept the system stable after the addition of superior strains.Aerobic granules were cultivated in a sequencing batch reactor (SBR) with conventional activated sludge in 30days. Formation of aerobic granules experienced three stages: domesticating, forming, mature and growing. After aerobic granules formation, aeration control was beneficial for the stable of aerobic granular.Aerobic granules were used to treat contraceptive wastewater after acclimation. Recycling time had been separated to two stages. Degradation ratio of COD reached above 90% within 2h at 0.3m³/h aeration. Meanwhile, under the given conditions, dissolved oxygen (DO) was sufficient to keep the activity of nitrifying bacteria while aerobic granules could be kept stable. Therefore, 0.3 m³/h and 2h were decided as the optimal aeration and recycle time of the first stage. In the second stage, degradation ratio of NH₃-N was above 98% in 22h. Over 0.1 m³/h aeration was not helpful to keep granules stable. So 0.1m³/h and 22h were selected as the optimal aeration and recycle time at the stage.