ADVANCED NITROGEN REMOVAL: EXPERIENCES AND OPERATION RESULTS OF 80 MGD POST-DENITRIFICATION FILTERS, VIIKINMÄKI WWTP, CITY OF HELSINKI

The world's largest tertiary denitrification filtration plant was taken into operation in the end of the year 2003. The tertiary unit includes ten Biostyr-filter cells each having 144 m2 surface area. The first year's operational experiences from the process have been positive without any major problems. The average flow to the plant has been 73 MGD which is equivalent to 7.7 m/h as hydraulic filter load. On average effluent TN concentration has been 5.4 mg/l with an 86 % total reduction calculated from the plant influent. The effluent TP has been on average 0.24 mg/l with a 96 % total reduction. The specific consumption of the methanol has been 2.9 g MeOH/g NO3-N removed. Amount of backwash water has been 2.1 % calculated from the influent flow. Operational costs of the tertiary filtration have been 1.3 /kg N and 0.95 cent/m3. The total investment cost for the tertiary unit was 32.5 M.