Latest HUBER dewatering and conveying technology: new construction of the sludge dewatering system on the Beilngries WWTP

The Beilngries wastewater treatment plant is located in the Altmühl Valley, a region very popular with tourists. The plant treats the wastewater of approx. 10,000 inhabitants. The digested sludge is dewatered three times a year over a period of two weeks using a decanter from a contractor. The practice of contract dewatering was then scrutinised for the following reasons:

1. The long stacking of the digested sludge, also due to its cooling, combined with the high throughput rate on the decanter, led to poor dewatering results of only 20% dry matter content in the press cake. The disposal costs for the poorly dewatered press sludge were correspondingly high.
2. The centrate water produced then also had to be stacked and returned as evenly as possible, which was labour-intensive, in order not to overload the biological treatment process and avoid peaks of return load.
3. Recently, the digester has also been fed with large quantities of food waste/fat from the surrounding catering industry in order to significantly increase the gas yield and thus the electricity generation from the digester gas. However, the food waste contains high nitrogen and phosphorus loads, which further jeopardised compliance with the limit values in the wastewater treatment plant's effluent during discontinuous sludge dewatering via the centrate.

HUBER Screw Press Q-PRESS® 620.2 wins the contract

After several on-site performance comparisons of different sludge dewatering suppliers, the contract for a permanently installed sludge dewatering system was awarded to HUBER SE with the Screw Press Q-PRESS® 620.2. In addition to the screw press, the complete new construction also includes the pump and measuring technology including online solids measurement, polymer preparation, polymer mixing into the sludge, press sludge conveying technology and the electrical control system with control system connection by Spangler.

The planning for the complete new building was significantly influenced by the plant manager Mr Porkert with the focus on:

• Extensive automation and process visualisation
• Control technology safety concept for sludge and gas treatment
• Possibility of dewatering 45°C warm digested sludge from the digester brine
• Resistance of the sludge path to coarse materials and sediments from the digester or the fat intake
• Consistent discharge of corrosive process air
• Maximum flexibility when filling and removing the sludge containers

Performance data from tests exceeded

The performance data of the sludge dewatering system now exceed the results of the previously tested mobile HUBER demonstration plant. With a throughput of 5 m³/h, a dewatering degree > 28% DR is achieved. The screw shaft of the press operates at a maximum speed of 0.3 rpm, requiring an electrical power consumption of only 1 kW. The control system of the screw press automatically regulates the number of revolutions with the aim of maximising the dewatering result and minimising the filtrate load.

Automation of the conveying system

The fully automatic operation of the sludge dewatering system continues with the discharge of the dewatered sludge using a HUBER Screw Conveyor Ro8 TC as a distribution screw. Three containers can be filled without operator intervention by means of the automatically swivelling distribution screw. For example, five preset drop points can be approached for each container and filled to a desired height. This means that the volume of the skip containers can be utilised to the maximum without, for example, having to smooth out the filling manually before removal.

The motorised position adjustment for the distribution screw and the discharge chute even allows several skips to be filled in layers at the same time. This function makes it possible to refill sludge to a skip after the sludge has settled or compacted. Some operators even report systematic air-drying of the dewatered sludge when several skips are filled alternately in layers. 

The automation of the conveyor technology does not end with the filling of the skip: Before the containers are collected by the haulage contractor, the distribution auger automatically swivels into a safe parking position, allowing the skips to be collected safely and quickly, even without the intervention of the operator.

HUBER SE would like to thank the client, the city of Beilngries, the head of the wastewater treatment plant Mr Porkert and the engineering office Goldbrunner from Gaimersheim responsible for planning, tendering and construction supervision for the trust they have placed in us and the very good, constructive and smooth cooperation.