Reningsgrad

Reningsgrad, or degree of purification, is a measure of how effectively a treatment process reduces pollutants in a stream or wastewater. It is commonly expressed as a percentage and can be calculated for specific pollutants or on a mass basis.

Calculation: Reningsgrad = (Cin − Cout) / Cin × 100%, where Cin is the influent concentration and Cout is the effluent concentration. On a mass basis, it can be written as (Mass_in − Mass_out) / Mass_in × 100%. A higher reningsgrad indicates greater removal of the pollutant.

Context and pollutants: In wastewater treatment, reningsgrad is used to assess removal of pollutants such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), and nutrients like nitrogen and phosphorus. It can be reported for each pollutant or as an overall measure of plant performance.

Typical values: Municipal treatment plants using activated sludge systems often achieve BOD removal in the range of 85–95% and COD removal of 80–95%. TSS removal commonly exceeds 90%. Nitrogen and phosphorus removal vary more and depend on process design (aeration, anoxic/anaerobic stages, tertiary treatment) and operational conditions.

Factors affecting reningsgrad: The degree of purification depends on organic load, hydraulic retention time, temperature, oxygen supply, microbial community, process type, and operational control. Seasonal variations and upsets can also influence measured values.

Limitations and use: Reningsgrad is a useful benchmarking and compliance metric but is pollutant-specific and should be interpreted alongside standard effluent limits and overall water quality goals. It informs design, optimization, and regulatory reporting in wastewater management.