Smart sludge control
Process optimization with RheoScan at a wastewater treatment plan in Ljubljana, Slovenia
In Ljubljana, Slovenia, one particular customer in the wastewater industry has continuously sought to improve efficiency. That is why the plant owner tested our RheoScan, an automated, optical polymer measurement and dosage system at the belt thickening stage to reduce polymer consumption and enhance digester performance, in 2014.
The challenge:
Reduce polymer costs and increase overall efficiency
However, rapid fluctuations in incoming sludge quantity and quality made it essential to optimize the system
prior to implementation. The following targets were set for a new test series in 2015 in order to verify the performance and economic viability of the new test installation:
- Reduce polymer consumption at the belt thickener to achieve at least 5% dry solids at the thickener discharge
- Examine the effects of reduced polymer dosage on digester performance, biogas production, and polymer consumption in centrifuge dewatering
- Demonstrate the reliability of the RheoScan system in the long term
All of these criteria had to be fulfilled, despite challenging operations with highly dynamic incoming sludge. The parameters for the RheoScan tests had to be carefully monitored, optimized, and correlated with belt speed controls in order to achieve optimum results.
Our solution:
Real-time optimization for KPIs and advanced data analysis
Given the wide range of variables involved in the test, an array of process data had to be collected and fed into ANDRITZ SEPARATION’s smart service platform. This included specific KPIs, such as polymer savings at the belt thickener and decanter centrifuge, rheoscan availability, and biogas production.
The actual storage capacity of the digester and of other intermediate steps had to be taken into account. And the reaction kinetics for biogas generation as well as the delay in feeding sludge from the belt thickener to the decanter were recorded carefully in real time. Thanks to remote access and processing of plant performance
data during the testing process, ANDRITZ SEPARATION and the customer succeeded in making the necessary adjustments and programming the system to achieve all KPIs over the course of the test period.
Results:
Total savings providing an impressive ROI
The test operations were a resounding success, enabling the plant to achieve significant savings thanks to the RheoScan system. We were able to confidently calculate annual polymer savings of 33.8% in the belt thickening stage alone, plus 16% polymer savings in the dewatering stage. In addition, an annual production increase
for biogas of 11.7% was predicted.
Together these efficiency gains would give the plant a total amortization period of only a few months for its RheoScan system. The fully automated system used for more than 85% of the test period also reduced the
need for manual supervision and intervention, while ensuring high reliability. No existing operational performance standards were compromised by the reduced polymer consumption, making full implementation of RheoScan the obvious choice after test operations.
