The aerobic activated sludge process is common practice in municipal wastewater treatment. Here, the wastewater discharged from housing estates and industry is treated so that it can be discharged directly into nearby bodies of water without causing any damage. In practice, the treatment works very well, but there are also negative aspects to the treatment method. The purification of organic loads and the reduction of nitrogen and phosphorus require high energy expenditure for the aeration of the basins in the form of electricity. Furthermore, due to the biology that grows during the purification process, residual substances remain in the so-called sewage sludge, which accumulates in the sewage treatment plants as primary sludge and surplus sludge. As a rule, sewage sludge is only used to generate energy from a plant size of 10,000 PE (population equivalent) by using digestion towers.
There are already other approaches to anaerobic wastewater pre-treatment. In this process, up to 80 % of the organic load is converted into valuable sewage gas prior to final aerobic treatment. This significantly relieves the aerobic final cleaning process and reduces the oxygen requirement and thus the compressor output required to aerate the treatment tanks. Due to the anaerobic degradation of organic loads during pre-treatment, only a fraction of the organic load reaches the final aerobic treatment stage. As a result, the production of excess sludge is significantly reduced, while the cleaning performance of the aerobic process stage remains the same.
The main issue with upstream anaerobic pre-treatment is the temperature of the incoming wastewater, which is around ten degrees Celsius. Anaerobic systems usually operate in the mesophilic temperature range around 38 degrees Celsius.
We at FlexBio have solved the problem and use our fixed-bed reactor to fix the anaerobic biology in the reactor and thus make the generation times of the biology independent of operating temperatures.
Initial tests with our mobile test plants showed high throughput rates with a retention time of four hours, an operating temperature of around 14 degrees and a COD degradation rate of 60 %.
Thanks to our plug-and-play system, wastewater treatment plants up to a size of 50,000 PE can be retrofitted quickly and allow municipalities to make their wastewater treatment more energy-efficient.