Energy efficient measurement and control of decanters for waste water treatment

Decanter centrifuges are used at waste water treatment plants for separating water from sludge. Typically, the dry matter consentration is ingoing 2-3% and outgoing 25-35%. However, the separation process features large variations in dry matter content, typically +-10%. Variations on the inflow side are often replicated in the outflow, primarily because the commonly used controller cannot dampen the variations. This results in a loss of machine efficiency and in a waste of energy and a following emission of CO2 due to the larger water content in the sludge. Savings can be obtained using more advanced process controllers, which exploit the process history. At larger waste water treatment plants, (>100,000 PU) the saving potential is well above 100,000 DKK. Removal of sludge is expensive, 500-1000 DKK/ton, and sludge carries a large environmental load. Improving dry matter content means large savings in transport, incineration etc.

Our objective is in this project to establish and test a new energy efficient decanter control system, coupling a machine-internal measuring technology with a machine-external signal-filtering and adaptive control technology. The control system will be tested at selected waste water treatment plants. The saving results for the environment, energy and operating economy will be quantified