In the city of Harstad, Norway, space is at a premium. When the need arose for a new wastewater treatment plant (WWTP), finding a solution that minimized land usage was crucial. The result is Harstad Sør RA, a modern facility that efficiently treats wastewater while occupying just a fraction of the space required by traditional methods.
The challenge: Harstad Sør RA receives relatively diluted domestic wastewater from 8200 inhabitants, along with septic and external sludge. The treatment requirement is primary treatment, focusing on removing suspended solids and reducing BOD5 (biochemical oxygen demand).
Inrigo stepped up to the challenge with a clever and compact design. Instead of relying on conventional sedimentation, which demands vast areas, they implemented rotating belt filters from Salsnes Filter. This innovative technology achieves the required treatment efficiency while using only 1/10th of the land.
Here’s how it works:
1. Inlet and Pre-treatment: Wastewater enters the plant through a pump station and undergoes pre-treatment with mechanical step screens to remove larger debris.
2. Coagulation and Flocculation: A cationic polymer is added to the wastewater, causing the suspended solids to clump together into larger particles (flocculation).
3. Filtration: The flocculated wastewater is then passed through rotating belt filters. The filters capture the solids, while the treated water passes through.
4. Sludge Removal and Cleaning: A scraper removes the sludge from the filter mesh, and high-pressure washing automatically cleans the filter mesh.
The result is impressive: The WWTP achieves an average removal rate of over 60% for suspended solids and over 50% for BOD5.
But the innovation doesn’t stop there. The sludge treatment process is equally advanced:
• Sludge Dewatering: A state-of-the-art screw press dewaters the sludge to over 30% dry matter without polymer addition, and up to approximately 40% when polymer is used.
• External Sludge Reception: A dedicated system receives septic and external sludge, removes coarse materials, and prepares it for treatment.
Inrigo was the total supplier for the primary treatment plant with belt filters and septic tank reception, with full process and electrical/automation responsibility. The Harstad Sør RA project showcases Inrigo’s expertise in delivering sustainable and efficient wastewater treatment solutions, even in challenging urban environments. By combining innovative technologies with smart design, Inrigo helps communities protect their environment and improve their quality of life.
