GB No. 4, spring 1991

EFFECTIVENESS OF WASTE WATER PLANTS
IN GDAŃSK AREA

All municipal waste water and part of industrial waste water of the Gdańsk and Sopot area (total volume of wastes 200,000 m³/d where municipal wastes amount to 160,000 m³/d) are treated prior to discharge into receiving waters. The treatment occurs in two large plants:

1. Mechanical-biological waste water treatment plant "Zaspa", designed for a nominal capacity of 37,000 m³/d (F=4,55ha); and
2. Mechanical waste water plant "Wschód" - nominal capacity 188,000 m³/d, however the real operating capacity does not exceed 120,000+130,000 m³/d (F=46.0 ha).

Industrial waste waters are also treated in a number of small plants; yet the wastes in these plants are only partially treated.

Here are the characteristics of the two main waste water treatment plants:

1. "ZASPA" waste water treatment plant The mechanical section of the plant consists of:
   • screens
   • grit chamber
   • row wastewater pumps
   • grease-removal tank
   • Imhoff's primary settling tanks.

   The biological section comprises:

   • aeration basins of "Inka" type
   • aeration basins of deep aeration
   • secondary vertical settling tanks
   • radial settling tanks

   Effectiveness of the plant is:

   • for BOD5: 80-85%
   • for sludge removal: >90%

   In the case of this plant phosphorus and nitrogen pose a problem since these elements are not sufficiently removed
   
   

2. "WSCHÓD" waste water treatment plant It is the largest plant in Gdańsk county. The planned capacity is going to reach 270,000 m/d (3.1m/s). It is a mechanical waste water plant consisting of:
   • screens chamber
   • aerated grit chamber
   • radial settling tanks
   • sludge digestion basins
   • sludge drying beds

   The effectiveness of this plant is poor. BOD5 reduction is lower than 30% and sludge removal doesn't exceed 60%. Sludge treatment is a considerable problem as digestion does not proceed properly because of the faulty design of the digestion chambers.

Low effectiveness of waste water treatment adds up to the devastation of the beaches in the Gdańsk area.

Unfortunately the situation cannot be changed before the biological section of the plant has been build, which will not take at least then 5-6 years.

The additional and urgent problem in the case of this plant is the difficulty in nitrogen and phosphorus removal.

Dr inż. B. Kasterka
Dept. of Water and Waste Water Techn.
Institute of Hydrotechnics
Technical University of Gdańsk