WWTP Fojnica (Bosnia-Herzegovina)

The works by Azierta collect sewage of part of the municipality of Fojnica, population 15,000. These works include the construction of a sewer, the spillway, the WWTP and the piping of the treated waters, thus, mitigating the damaging effects of untreated sewage on the environment.

Water is taken to the water treatment plant through a system of sewers. Treatment starts at the screens (two sets of screens) that keep the thickest solid waste out.

Pre-treatment continues to end up at the grease and sand trap where, using mechanical procedures, sand sinks and grease floats.

At the primary sludge settler, sludge drops to the bottom. The remaining pollutants are removed using biological procedures at the biological reactor by adding oxygen. It is at the reactor where the biological treatment of active sludge occurs. This is a two stage procedure.

Weight makes that biosolids formed in the reactor drop to the bottom of the secondary settler and are separated from the water (secondary sludge).

Water line

• Sewer
• Pre-screening
• Screening
• Delivery to biological treatment
• Pre-aeration
• Primary settling
• Secondary settling
• Disinfection

Sludge line

• Primary sludge purge
• Recirculation and secondary sludge purge
• Measurement of sludge flow
• Sludge digestion
• Thickening
• Discharge system