BioCrack: Optimized process and degradation rate of sewage treatment plant
Case Study - dairy Zott GmbH & Co. KG
Strong fluctuation in utilization, low gas yield
Electrokinetic disintegration with Vogelsang BioCrack
The sewage treatment plant belonging to the ZOTT dairy has a capacity of 100,000 PT. The Swabian company is one of Germany's largest producers of milk and yoghurt products. Around three million litres of milk are processed each week for these products alone. Mozzarella production is also an important source of income in the summer months, when around seven million litres of milk are processed each week on average. To improve the operation of the sewage treatment plant, ZOTT tested the electrokinetic disintegration process.
The company-owned sewage treatment plant cleans the production effluents. In winter only 50 per cent of its capacity is used, whereas in summer the daily intake increases to 2,500-3,000m³/h. In the first stage, all of the intake is transported to the flotation plant (grease trap). Approx. ten cubic metres accumulate here each day, and are conveyed directly to the digestion tower. The rest is transported to the biological plant. 30-50m³ of excess sludge is thickened here by a machine every day before being transported to the digestion tower, which operates at full capacity. On average, the input has a dry substance content of six per cent and is removed again with 4.1-4.2 per cent. After drainage, approx. 3,000 t of sewage sludge is produced each year, and is used in agriculture. The gas from the digestion tower is recycled by two combined heat and power plants, and the waste heat is used by the sewage treatment plant itself.
In the test with electrokinetic disintegration, the thickened excess sludge was treated with two BioCrack modules before it entered the digestion tower. Noticeable improvements were apparent immediately, as a result of which the operator, ZOTT, decided to keep the modules. In addition to a higher gas yield from the digestion tower, the degradation rate also improved significantly. This is how the loss on ignition was able to be reduced by four per cent: Before the operation, the sludge had a loss on ignition of approx. 68 per cent, which reduced to 62 per cent in the course of cleaning. With the same intake values, the sludge had a final loss on ignition of 58% with electrokinetic disintegration.