Summary
In recent years, increasing success has been achieved in the improvement of discharges from sewage treatment plants. Nevertheless, the residual content of potentially toxic xenobiotic substances and faecal bacteria in sewage treatment plant discharges still represents a substantial pollution hazard, particularly for smaller bodies of water.
In consequence, this project involved the investigation of potential for the application of biological process tanks as an advanced ecological purification stage.
The key elements of laboratory tests conducted in a micro-ecosystem, together with pilot plant trials, were as follows:
Investigation of the efficiency of an ecological aftertreatment stage for the elimination of residual Chemical Oxygen Demand;
- Investigation of the efficiency of an ecological aftertreatment stage for the elimination of residual Chemical Oxygen Demand;
- The elimination of pathogenic bacteria and viruses;
- The composition of biocenoses in process tanks, together with seasonal variations in these biocenoses;
- The impact of adjustments in process control upon the stability and performance of the pilot plant.
Results:
- In summer, 99% elimination of coliform bacteria has been observed. Discharge concentrations of enteroviruses have been some 60 – 70% lower than the influent values.
- The installation of longitudinal partitions in tanks has prevented short-circuit currents, whilst ensuring the maintenance of the dwell times required for degradation and elimination processes.
- In the pilot plant, Chemical Oxygen Demand has been reduced from an average of 25 to 15 mg/l, even without the installation of partitions.
- At a pool depth of 3 metres, the effects of redissolution from sediment can be reduced. The surface area required can be reduced at the same time.
