Aerobic wastewater treatment
Nutriflok macronutrients to support activated sludge performance
Sludge settling is an utmost important parameter in aerobic wastewater treatment plants. Insufficient sludge settling decreases effluent quality and increases discharge levels. Poor settling can be induced by an excess of filamentous bacteria, an imbalanced influent, a shock loading or a toxic pulse.
Another major challenge for sludge settlement in aerobic wastewater treatment is to guarantee the performance of the nitrification process at lower temperatures (<15°C, <59 °F).
Based on a thorough full scale experimentation, Avecom has succesfully developed a range of specialized powder supplements (Nutriflok) to improve the sludge quality and the effluent quality of aerobic wastewater treatment plants.
The standard product consists of
- Carbohydrates, stimulating Zoogloeal bacteria (floc formers),
- Mineral compounds enhancing nitrifiers and floc formers, and weakening filamentous bacteria, and
- Aluminosilicate matrices facilitating microbial adhesion and aggregate formation.
Tailor-made variations can be developed in cooperation with the customer.
- Better sludge settling (lower sludge volume index)
- Improved effluent quality (better removal of organic material, total suspended solids and nitrogen)
- Increased reliability in case of disturbances (eg shock loadings or temperature variations)
- Enhanced nitrifying capacity particularly at lower temperature
- Lower operational costs of the installation
- Decreased levy costs on the final effluent
- Tailor-made adaptation of the supplement composition possible
- Dosage optimization by Avecom specialists based on analyzed sludge characteristics
- Biological aerobic wastewater treatment plant with variable floc formation
- During colder periods proactive dosing to maintain the nitrifying activity (nitrification is made possible at lower temperature)
By means of rigorously controlled lab-scale activated sludge systems operated in parallel, the effect of the addition of a nutritive supplement on the overall performance of these systems was verified.
Nutriflok 50 S is a commercially available product, containing nutrients and flocculating agents.
In a first series of tests by means of SCAS (semi-continuous activated sludge) reactors, fed with synthetic wastewater, the positive effect of the supplement (dosed at 5% of the chemical oxygen demand (COD) load) on the sludge volume index (SVI) (39% improvement) and the residual COD (40% improvement) was demonstrated. In a second series, an industrial wastewater was used in a benchscale set-up according to the OECD procedure. The overall efficiency and sludge sedimentation characteristics were compared for two parallel activated sludge systems continuously fed with pharmaceutical wastewater. In the control no additive was given; the other reactor received on a daily basis a dose of Nutriflok 50 S corresponding to 10% of the COD load.
The performance of the Nutriflok 50 S supplemented reactor was found to be statistically better in terms of sedimentation characteristics, nitrification and COD removal than the control.
Especially when operated under winter conditions (10°C) and at higher sludge loading rates (Bx = 0.26 kg COD/kg VSS.d) the COD removal efficiency was about 35% higher in the treated reactor. Moreover, nitrification could be maintained in the supplemented reactor at low temperatures, whilst it became minimal under those conditions in the control reactor. Also in the second series of tests, sludge sedimentation characteristics improved with Nutriflok 50 S. The SVI was 40% lower for the Nutriflok 50 S amended sludge and the recycled sludge was 27% more concentrated. When operated at higher temperatures (20–26°C) the amended sludge was less sensitive to denitrification linked flotation in the settler.
Microscopic examination of the sludge revealed a more diverse microbial community and the presence of higher trophic organisms in the supplemented reactor. These results indicate a potential for considerable improvement, not only of the overall conversion efficiency, but also of the sludge management characteristics when Nutriflok 50 S is dosed to the activated sludge.
Full article: Technical Note