Within the idea project, the wastewater of the treatment plant of Locarno has been characterised by measuring the ammonium, nitrate, chemical oxygen demand (COD), phosphorous and solid content. The inflow water to the pilot plant had an average COD content of 190 mg/L, 32 mg/L ammonium nitrogen, phosphorus 3.8 mg/L and an average alkalinity of 113 mgCaCO3/L.
For the demonstration of the functionality of the IDEA concept, a coagulation tank with a volume of 3 m3 with a downstream dissolved air flotation (DAF). The effluent water of this, so called advanced primary treatment, was further treated in a downstream installed 1.2 m3 fixed bed reactor. The reactor is divided into four compartments, three fixed bed compartments and one clarifier. Each of the three bio-compartment were equipped with fixed bed carrier. The final carrier surface used was 75 m2. The high caloric sludge from the DAF unit was valorised in a 50 L anaerobic digester on site.
The installed pilot plant was tested with clear water before the start-up with municipal wastewater taken after the coarse grit. The advanced primary treatment was operated with 5 m3/h from which a side stream was further biological treated (380 L/h).
The process combination of a coagulation step, the solid-liquid separation with a dissolved air flotation, heterotrophic carbon elimination in a fixed bed biology and the valorisation of the sludge with an anaerobic digester is functional and except of the performance of the final settling tank showed no problems during the monitoring period. The settling tank is not designed and build in a hydraulic optimal way and shall be redesigned in a further application. The separation performance of the primary treatment and elimination showed that the water discharge limits can be reached and the high caloric primary sludge is a good substrate for the anaerobic digestion.
The total advanced primary sludge potential is at small scale (400 PE) plants is overcoming the electrical needs for the treatment process. As showed in following table, the final electrical potential is covering already 42% of the plant consumption, already at small scale.