A multinational general contractor was awarded a project to treat municipal wastewater of over 14.000m3/d in Central Poland. Due to the project specifications, a reliable and proven solution was required to warrant stable denitrification even in very low temperatures of sewage and to meet the strict EU BNR removal requirements. In winter, when the flow is unstable and might vary up to 600m3/h, the temperature of sewage might drop to 6oC, making denitrification difficult.
SYMBIONA was chosen because of our partner MBBR technology, complete with screening and our proprietary aeration system.
To meet the strict requirements, the overall design of WTTP is divided into various process stages, consisting of anoxic zone for RAS pre-denitrification, BIO-P removal, anoxic selector before MBBR, MBBR zone and then aerobic zone with carousel-type aerobic reactor. Provided by SYMBIONA, the MBBR stage is filled with biomass carriers and it also receives some stream sludge recirculated from the aerobic reactor. It guarantees constant nitrification, even in very low temperatures in winter (below 12oC, minimum temperature of wastewater 6oC).
The aeration system consist of a special HDPE grid, high-efficiency diffusers, which warrant airlift hydraulics pattern for carriers in moving bed. Wedge wire screens retain biomass carriers inside the MBBR reactor, allowing free flow of wastewater downstream to the aerobic step. Wedge wire screens are continuously cleaned by the mixed flow of air bubbles, water and the movement of biomass carriers.
Treated wastewater from the main carousel biological reactors with normal MLSS (around 4g/l) goes to secondary clarifiers for the final solid-liquid separation. After that, the clean effluents are to meet the requirements not only these of reduction in COD/BOD but also those regarding the complete nutrient removal, which is below 10mg/l of TN and 2mg/l of TP also in winter.