Water samples from the wastewater treatment system in Soliman, Tunisia, were obtained along the treatment process from the influent input, the pretreatment pond, the oxidation channel based on activated sludge treatment and the effluent pond (Fig. 1).
Soliman STP system renewed in 2004, receives influents(12300 m3/day) from a population of 30 000 residents (www.onas.nat.tn, 2007).
The primary treatment is carried out to remove the coarse fraction inclusive of oil, fatty acids and suspended solids.
The biological processing is used to remove microorganisms, nitrogen and phosphorus, and lower the organic load as defined by the BOD.
The biological treatment, based on the natural ability of wastewater containing
bacteria to degrade organic material, is roughly divided into aerobic and anaerobic treatments including conventionally the oxidation pond and the activated sludge process.