BODreningsgrader

BODreningsgrader is the degree of removal of Biochemical Oxygen Demand (BOD) achieved by a wastewater treatment process. It is a measure of how much organic matter capable of consuming oxygen in the water has been removed from influent to effluent. The term is commonly used in Nordic and European contexts to assess effluent quality and environmental impact.

Calculation and measurement: Reningsgrad = ((BOD_in − BOD_out) / BOD_in) × 100%. BOD_in denotes influent BOD, BOD_out effluent BOD. BOD is typically reported as BOD5, the amount of oxygen consumed in five days at 20°C. BOD testing follows standard methods and local regulations; results indicate the fraction of biodegradable organic matter removed.

Treatment stages: Primary treatment removes a portion of BOD through sedimentation and preliminary processing, usually roughly 20-40%. Secondary biological treatment delivers the largest removal via microbial oxidation, commonly about 80-95% of the remaining BOD. Some plants employ tertiary or advanced polishing steps to reduce residual BOD further. Overall removal often falls in the 90-99% range for well-operated plants, depending on wastewater characteristics and process design.

Use and significance: BODreningsgrader is used in plant design, performance monitoring, and compliance to environmental standards. Regulators set limits on BOD concentration in treated effluent, reflecting the required reningsgrad. The metric helps compare different treatment configurations and monitor long-term performance.