Increasing the energy efficiency of sludge stabilization by an interconnected operational approach

In Germany sewage treatment plants with serving sizes from 5,000 to 40,000 PE are usually designed with simultaneous aerobic sludge stabilisation. Main advantages of this approach are the simple operation and easy technical design of the biological stage. But the balance of the turnover of the organic load shows an increased energy consumption of these sewage plants compared to plants with separate anaerobic sludge stabilisation. In order to optimize the energy consumption omitting the implementation of a digester on every plant, an interconnected operational approach for sludge stabilisation was developed. In this concept the aerobic stabilisation plants are operated at reduced sludge ages providing nutrient removal without sludge stabilization. The unstabilised sludge of these plants is transported to a central digestion plant with corresponding aggregates like digester, CHPP, dewatering.