Full scale implementation of the nutrient limited BAS process at Södra Cell Värö

Area of Science:

• Environmental Engineering
• Biotechnology
• Wastewater Treatment

Background:

• Pulp and paper mill effluents pose significant environmental challenges.
• Conventional wastewater treatment methods can be inefficient and produce large amounts of sludge.
• The combination of biofilm and activated sludge processes offers a promising solution.

Purpose of the Study:

• To evaluate the effectiveness of a nutrient-limited biofilm-activated sludge (BAS) process for treating pulp and paper mill effluents.
• To assess the impact of nutrient limitation on sludge characteristics and overall process efficiency.
• To validate the full-scale implementation of the nutrient-limited BAS process.

Main Methods:

• Implementation of a nutrient-limited biofilm process followed by an activated sludge stage (BAS).
• Full-scale operation at Södra Cell Värö kraft mill starting July 2002.
• Monitoring of effluent quality parameters including COD, EDTA, suspended solids, and nutrients.
• Analysis of sludge production and sludge volume index.

Main Results:

• The nutrient-limited BAS process achieved high removal rates: ~70% COD and >90% EDTA.
• Stable operation met all effluent discharge limits after a 5-month optimization period.
• Effluent concentrations were low: 20-30 mg/L TSS, 0.3-0.5 mg/L phosphorus, and 3-5 mg/L nitrogen.
• Sludge production was minimized at 0.09 kgSS/kg COD removed with a sludge volume index of 50-100 mL/g.

Conclusions:

• Nutrient-limited BAS is a robust and highly efficient process for pulp and paper mill wastewater treatment.
• This approach significantly improves sludge characteristics and minimizes sludge production.
• The full-scale implementation demonstrates the process's viability and effectiveness in meeting stringent environmental regulations.