Chemical Control Of Filamentous Sludge Bulking In A Full-Scale Biological Nutrient Removal Activated Sludge Plant

Simulation analysis based on a mathematical model is one of the powerful tools for determining the operational conditions for a full scale biological nutrient removal plant. The model that included the Activated Sludge Model No.2 was developed for simulating the performance of the plant in Sapporo City. The investigated plant has the biological reaction basin which consists of the four zones, anaerobic-aerobic-anoxic-aerobic phases with the step feed of the primary effluent to the anaerobic and anoxic zones. We performed three experiments to calibrate and verify our model: (i) Characterization of organic matters in the influent of the reaction basin with the OUR measurement method; (ii) Measurement of COD and nutrient concentration at the plant; (iii) Lab-scale batch experiments with the anaerobic-aerobic-anoxic-aerobic phases. The calibrating process of the model showed that no modification of parameter values was required to evaluate the performance of the plant and population of the activated sludge. Simulated results showed that the choice of the sewage step feed ratio did not affect the nitrogen removal and that the denitrification rate in the anoxic zone was controlled by the hydrolysis rate of the slowly biodegradable organic matters. The results of the lab-scale experiment and simulation results showed that the addition of the readily biodegradable organic matters like fermentation products of the primary settler sludge was effective to improve the performance of nitrogen removal.

Download Full-text

The effect of chemical bulking control on biological nutrient removal in a full scale activated sludge plant

Water Science & Technology ◽

10.2166/wst.1996.0441 ◽

1996 ◽

Vol 34 (3-4) ◽

pp. 275-282 ◽

Cited By ~ 5

Author(s):

G. B. Saayman ◽

C. F. Schutte ◽

J. van Leeuwen

Keyword(s):

Hydrogen Peroxide ◽

Activated Sludge ◽

Nutrient Removal ◽

Pilot Scale ◽

Full Scale ◽

City Council ◽

Phosphate Removal ◽

Biological Nutrient Removal ◽

Removal Processes ◽

The City

The use of chemicals for sludge bulking control has a direct effect on the biological nutrient removal processes in activated sludge systems designed for this purpose. Chlorine has been used on full scale but information on the use of ozone and hydrogen peroxide is limited to pilot scale tests. The objective of this study was to investigate the effects of chlorine, ozone and hydrogen peroxide on nutrient removal processes when used on a continuous basis for bulking control in a full scale biological nutrient removal activated sludge plant. The full scale studies were conducted over a period of 39 months at the Daspoort sewage works of the City Council of Pretoria. The results indicate that at low dosages the oxidants have limited effects on the nutrient removal processes but at higher levels chlorine had a detrimental effect resulting in the phosphate limit of 1 mg P.1−1 being exceeded. It is concluded that chlorine is the most effective of the three oxidants for bulking control, but that it should be used with caution in order not to upset the biological phosphate removal processes. Ozone at low levels had a small but consistent positive effect on bulking control as well as on nutrient removal. The effects of hydrogen peroxide were very small except at high dosages.

Download Full-text