Single Stage Phosphorus and TSS Removal by DynaDisc Filters in Finland

DynaDisc® Filters remove phosphorus and TSS in a single stage for Pietersaari WWTP in Finland.

The Situation

Pietersaari WWTP in Finland was built in the 1970’s and serves a population equivalent of approximately 5000.  The plant additionally takes industrial flows from an abbatoir, as well as surface water.

The plant includes conventional processes such as screening, sand/grease traps, primary sedimentation, activated sludge treatment and flotation.  The flotation system was not able to meet the Total Suspended Solids (TSS) and phosphorus discharge limits.

The Problem

The Pietersaari WWTP in Finland had been set a phosphorus discharge target of 0.25 mg/l and the current flotation process was struggling to meet this.

Typical Flow and Discharge Limits

  • Design Flow - 2200 m3/h
  • P Discharge Limit - 0.25 mg/l or less
  • TSS Discharge Limit - 5 mg/l

The Solution

DynaDisc® technology was chosen to replace the flotation system because, as well as meeting the TSS and phosphorus removal targets, it is compact and fits within the existing flotation basins.  Typical TSS and phosphorus levels in the inflow, and removal levels at outflow are shown below.

Results of Sampling

  • TSS at inlet - 15-25 mg/l
  • Total P at inlet - 0.75 mg/l
  • TSS at outlet - 6-7 mg/l
  • Total P at outlet - 0.06 - 0.08 mg/l

Two CDC2435/35 DynaDisc® filters were installed within the flotation basins.  These units provide TSS and phosphorus removal in one step.

The design flow to the DynaDisc® filters is 2200 m3/h and contains a maximum phosphorus content of 0.75 mg/l.  The target for total phosphorus removal is to 0.25 mg/l or less and a sample taken at the outlfow to the filters is showing phosphorus at only 0.063 mg/l.


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