Half the iron, same clean water

Skanderborg Forsyning (Utility) reduces two WWTPs’ iron dosing by 55% & 44%.

Skanderborg Utility manages five WWTPs served by 1290 km of sewer pipelines, a distance equivalent to travelling from Himmelbjerget to Vienna. Every year, these five WWTPs process approx. 5.1 billion litres of wastewater.

At the five facilities, the wastewater treatment process begins with a mechanical removal of larger particles followed by biological water treatment. Here, microorganisms bind nitrogen, phosphate, and other organic matter to sludge.

However, these microorganisms leave behind a small residual amount of phosphate, and as temperatures drop during the winter months, their activity decreases. It is, therefore, common for WWTPs to add iron chloride in the third treatment stage to bind the remaining phosphate.

Less chemicals, greater savings

WWTPs frequently apply a fixed and careful amount of iron chloride to guarantee a safe discharge quality. However, phosphate concentrations in wastewater may vary significantly throughout the year. Consequently, relying on a constant fixed dose often results in a unnecessarily elevated consumption of precipitation chemicals.

To explore the potential for optimised iron dosing at Skovby and Hørning, Skanderborg Utility carried out an analysis of the plants.

”Following thorough case studies, we have now implemented soft sensor control on two of our treatment plants.”
Pernille Gammelgaard, Operations Manager, Skanderborg Utility.

A safe and transparent process

Since its installation, BSS SoftSensor has been operating reliably at the WWTPs in Skovby and Hørning and delivered great savings without compromising the effluent quality.

“It has been a very transparent and reassuring process for us to go through with excellent support from BSS from the start right through to commissioning and completion. We have achieved good savings on chemicals, without any deterioration in our discharge results,”
Pernille Gammelgaard, Operations Manager, Skanderborg Utility.

BSS’ software dynamically adjusts and recommends dosing in response to phosphate levels, ensuring accurate and efficient chemical dosing. At the same time, BSS SoftSensor incorporates a high level of built-in safety, including alarms and an automatic fallback mechanism in case of any data issues.

Ironclad results

Using BSS SoftSensor, the WWTP in Skovby has achieved a 54.84% reduction in its use of precipitation chemicals, while the plant in Hørning has reduced dosing by 43.86%. Collectively, the two WWTPs are on track towards an estimated annual saving of 18.286 EUR (136.627 DKK).

Furthermore, the WWTPs’ chemical savings has lowered the plants' joint CO₂ emissions by 44.87 tonnes annually. This environmental achievement is attributable to the omitted chemicals’ production and transportation.