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Sludge Dewatering


Olpas measurement technology allows a complete insight into the (sludge) dewatering process, measuring dry solids in the thickened sludge, residual polymer and TSS in centrate, and concentration of the dry cake.

During the sludge dewatering process, water is removed from the sludge to reduce its volume and weight for disposal or further treatment. No matter what methods are used for sludge dewatering, it is important to finetune the process in order to minimise both the environmental and economic cost.

Full monitoring of the dewatering process

The sludge dewatering process, either performed by a thickening table or decanter centrifuge, can be fully monitored using four Olpas sensors on three locations (not all are required):

  1. Sludge inlet: measuring sludge concentration of thickened sludge

  2. Centrate: measuring residual polymers in centrate

  3. Centrate: TSS in centrate

  4. Sludge Cake (dry cake)

All four of these parameters have specific challenges, that can be attacked by the innovative OLPAS Technology using ultrasound instead of the traditional optical or microwave technology.

Keep an eye on dosing effectiveness by measuring solids in sludge during different stages of sludge dewatering.

Olpas sensors in this application do not need automated mechanical cleaning. No wipers. No pressured air. And only limited preprocessing of the centrate in a flow-cell or preprocessing unit.

Sludge inlet concentration [1]

The sludge concentration measurement at the inlet of the dewatering unit is vital to determine the amount of polymers to add. An accurate measurement that swiftly follows the real concentration trend allows the control system logic to adapt the added polymer content or sludge flow-rate.

Current state-of-the-art optical sensors fail to measure the concentration accurately in changing conditions, due to their dependence on the optical parameters of the sludge. Furthermore, fouling is present after a few days of operation that cannot be fully reversed by the fault-prone mechanical wipers.

A correct measurement of the inlet concentration is the first step Olpas proposes for an improved and efficient dewatering process.

Centrate [2 & 3]

The quality of the centrate is a more subtle indicator of the dewatering process efficiency.

  1. A high suspended solids (TSS) content in the centrate increases waste water processing costs upstream in the plant and is an indicator of an inefficient dewatering process.

  2. A clean centrate with a large polymer content is an indicator that polymer dosing is not scaled correctly in relation to the incoming solids content.

Both measurements combined allow to optimize centrate quality without reducing dewatering performance. A good set of sensors with low drift and long maintenance intervals are required to make sure dewatering performance is kept continuously on point.

Centrate is almost never monitored actively. Not because it does not provide important information, but because it is extremely hard to do. Untill now. Olpas changes this paradigm and makes monitoring centrate possible and economically feasible.

Sludge cake [4]

The goal of a dewatering solution is to obtain a sludge cake with a minimal amount of moisture present while consuming as little polymers and energy as realistically possible.

Using a set of sensors as described before, sludge cake quality can be expected to be kept constant. However, for a more optimal control of this parameter, Olpas developed a solution that does not require compressing of the sludge cake. The application is currently only available for selected partners in a co-development agreement.

Check all 4 applications to find the specific advantages our Olpas sensors provide. Remember: not all measurements are necessary in all applications.

Just adding 1, 2 or 3 applications already gives advanced insight into the dewatering process.

By ensuring effective dewatering and maintaining optimal TSS levels and residual polymer levels in centrate, WWTPs can achieve cost savings:

  • reduced disposal costs

  • lower chemical usage

  • decreased energy consumption


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