Plant performance of an Sequencing Batch Reactor in Poland, operated with high Chromium load, reaching advanced nutrient removal

This paper presents performance experiences from the operation of a large SBR facility in Nowy Targ, Poland. The plant has been in operation since 1995, and a number of investigations have contributed to the evaluation of the operating conditions at the Nowy Targ plant. The plant was designed for treating municipal and industrial wastewater from about 150,000 person equivalents. The plant receives chromium rich wastewater from almost 400 small and medium-sized tanneries in the area. Although the Cr concentration sometimes exceeds 20 ppm in the combined incoming wastewater, the nutrient removal as well as organic removal has proven to be very good. The possible effect of Cr acting as a precipitant for phosphorus is also addressed. The influence of water temperature on the nitrogen performance is clearly demonstrated by the results. The prevailing low water temperature has affected but not inhibited the nitrogen removal. The phosphorus removal as found in this investigation suggests an advanced biological removal; however the impact of a possible precipitation by Cr is addressed.